BG – Biogeosciences

EGU22-902 | Presentations | MAL31 | Vladimir Ivanovich Vernadsky Medal Lecture

Atmospheric Deposotion Impacts on Marine Biogeochemistry 

Adina Paytan

Atmospheric deposition of trace elements and nutrients to the ocean can significantly modify seawater chemistry and influence oceanic productivity.  However, mounting evidence suggests that the response of phytoplankton to atmospheric deposition depends on the chemical composition of the aerosols and varies across different phytoplankton species.  Responses are also different depending on oceanographic setting and season. To determine if and how nutrients, metals and other constituents from atmospheric deposition influence plankton activity and community structure in the ocean we analysed nutrient and metal concentrations in marine aerosols and tested how these constituents impact phytoplankton.  This is done using incubation experiments with natural phytoplankton assemblages and different sources and amounts of aerosol or pure nutrients and metal additions.  Variance in utilization of nutrients and susceptibility to metal toxicity was identified among different taxa, suggesting that aerosol deposition could potentially alter patterns of marine primary production and phytoplankton community structure.  In addition, input of bioaerosols can also affect phytoplankton communities and should be considered. Importantly, up to 25% of airborne microbes are viable upon deposition and may compete for resources with marine organisms. Airborne viruses can also infect specific phytoplankton hosts and hence impact the ecosystem. Natural and anthropogenic change could impact the chemical and biological composition of aerosols with consequences to ocean chemistry and productivity with potential feedbacks to the carbon cycle.

How to cite: Paytan, A.: Atmospheric Deposotion Impacts on Marine Biogeochemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-902, https://doi.org/10.5194/egusphere-egu22-902, 2022.

EGU22-3435 | Presentations | MAL31 | BG Division Outstanding ECS Award Lecture

Carbon budgets from global to regional scales: current challenges and future perspectives 

Ana Bastos

To fulfill the international objective “…to reach global peaking of greenhouse gas emissions as soon as possible … and to undertake rapid reductions thereafter in accordance with best available science...to achieve a balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century”, the Paris Agreement implemented the Global Stocktake Process to assess regularly the world’s collective progress towards achieving the purpose of the agreement and its long-term goals.

National greenhouse gas (GHG) inventories report only anthropogenic fluxes. However, many GHG sources are difficult to separate from the natural fluxes. Moreover, inventories cannot easily be scaled to the globe given the use of different approaches for GHG budgeting but, more importantly, because the states of the natural ocean and land sinks are not considered. Fast developments in the scientific capabilities to quantify GHG budgets and their trends consistently from the global to the national scale as well as accurate attribution of budgets to natural and anthropogenic processes are needed.

In Global Carbon Budgets top-down and bottom-up estimates still show large discrepancies at regional or country scale, due to large and multiple sources of uncertainty. Reducing these uncertainties and improving regional GHG budgets is currently the focus of the second “REgional Carbon Cycle Assessment and Processes” (RECCAP-2) initiative supported by the Global Carbon Project. This effort is fueled by an ever-expanding constellation of and in-situ and satellite-based GHG observations, and by increased process-based and data-driven modelling capabilities.

Here, I will discuss some of the elements that still challenge our ability to robustly link global to the regional and country carbon budgets, and their implications for the Global Stocktake. I will then show recent examples on how multi data-stream approaches can be used to identify and understand sources of discrepancies between top-down and bottom-up estimates and to improve attribution of regional carbon budgets to specific natural and anthropogenic processes.  

How to cite: Bastos, A.: Carbon budgets from global to regional scales: current challenges and future perspectives, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3435, https://doi.org/10.5194/egusphere-egu22-3435, 2022.

BG1 – General Biogeosciences

Unprecedented wildfires swept Mediterranean Europe in the summer of 2021 wreaking havoc economically and socially while clearing large swaths of forest land. Those that scorched the southern coastal highlands in Turkey came on the heels of a heat wave and at the peak of the arid season. Nearly two thirds of the Anatolian Peninsula are under the influence of Mediterranean-type climate and prone to seasonal wildfires, a quality that also encourages high species diversity. The region’s heterogenous topography is home to different meso- and micro-climates which in turn translate into high rates of endemism. Although fire as disturbance is essential for the regeneration of Mediterranean-type ecosystems, potential changes in fire frequency and severity, coupled with longer periods of drought expectations - mainly as a result of anthropogenic deforestation and climate change - is duly raising concerns. The expected increase in the frequency and intensity of climate-based disturbances necessitates some form of a predictive mechanism for future protection and mitigation, especially for these otherwise fire-adapted ecosystems. Dynamic Global Vegetation Models (DGVMs) with built in disturbance schemes when forced with future projections of climate models can be powerful tools in this regard.

In this study, we present our preliminary findings from six different model simulations, run with LPJ-GUESS, a process based DGVM. We initially introduced three native conifer species with different fire histories and significant distributions in the Anatolian Peninsula to the model and forced it with climatic drivers from ERA5 Land reanalysis dataset for the historical period. Once confident that our simulation results closely reflected the historical fires in the remote sensing datasets available through Google Earth Engine, we continued to force the model with climatic drivers from different model contributions to CMIP6, bias-corrected, interpolated to the 9-km horizontal resolution of ERA5 Land reanalysis and reflecting the RCP 8.5 scenario. All simulation results were analyzed using Climate Data Operators (CDO), ArcGIS, and R computing language.

Our preliminary results indicate an overall increase in pyro-diversity for the country across all simulations. A potential expansion of wildfire range towards the northwest was also observed, a curious outcome as this region includes the western Black Sea mountain ranges that are known for high precipitation rates. These mountains are also home to a rich forest cover with a fine mixture of broadleaved and conifer species spreading horizontally along different altitudinal belts. In light of our preliminary findings and along with our continuing research on the effects of any potential future climate-change related shifts in the fire regime on forest composition, we urge additional study of different landscape scale disturbances (i.e. soil erosion and landslides) which may potentially be triggered as a result of a diversifying and intensifying fire regime and which may have a significant impact for the terrestrial ecosystems and livelihood. 

This study benefited from the 2232 International Fellowship for Outstanding Researchers Program of the Scientific and Technological Research Council of Turkey (TUBITAK) grant 118C329. The financial support received from TUBITAK doesn’t mean that the content of the publication is scientifically approved by TUBITAK.

How to cite: Ekberzade, B., Yetemen, O., and Sen, O. L.: Looking into a fuzzy future: coupled effect of pyrogeography and a changing climate on an already fragile terrestrial ecosystem, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-239, https://doi.org/10.5194/egusphere-egu22-239, 2022.

EGU22-384 | Presentations | BG1.2

Pantanal’s 2020 fire season in perspective: the case of a natural heritage reserve 

Patrícia S. Silva, Joana Nogueira, and Renata Libonati

Pantanal saw a catastrophic fire season in 2020, with a quarter of the biome hit by flames (around 4 million ha). Protected and indigenous areas burnt entirely, and it is estimated that at least 17 million vertebrates died, including several endangered species endemic to the biome. These dramatic events drew attention to the occurrence and aftermath of fire within a fire-sensitive ecosystem such as Pantanal’s wetlands.

The RPPN (Reserva Particular do Patrimônio Natural) SESC Pantanal was one of such protected areas severely affected in 2020, with around 2/3 of its territory burnt. Here, we analyse the historical fire behaviour within the RPPN, including the 2020 events, using remote sensing products over the 2001-2020 period. 

Although fire has historically occurred within the RPPN at an average of 2 400 ha burned per year, the 2020 fire events were an absolute outlier with more than 70 600 ha burned. Before 2020, only 2010 reached above 10 000 ha of burned areas, and the most extreme events were found to be those above 3 000 ha. When considering the 2001-2019 period, wetlands and grasslands are the land cover types that burn the most (52 and 17% of the total burned area, respectively), followed by forests and savanna formations (16 and 9%, respectively). The year of 2020, however, changed this pattern: most burned areas occurred in forested areas (40%), followed by grasslands (26%) and savanna formations (24%). We also found that fire is not recurrent: during the 19 years of historical data the vast majority of burned areas occurred only once (60%), 35% burned up twice or thrice, and solely 5% burned more than 3 times.

Future climate change assessments seem to point at a warmer and drier future for the biome, when events such as 2020 might become more regular. Our results provide an historical characterization leading up to the 2020 fires within the RPPN SESC Pantanal, that may be of use for fire managers in light of future climate change. 

How to cite: Silva, P. S., Nogueira, J., and Libonati, R.: Pantanal’s 2020 fire season in perspective: the case of a natural heritage reserve, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-384, https://doi.org/10.5194/egusphere-egu22-384, 2022.

EGU22-1007 | Presentations | BG1.2

Investigating woody species resprouting in response to fire 

Yicheng Shen, Colin Prentice, and Sandy Harrison

Fire is a major disturbance in natural ecosystems and more extreme fires are predicted to occur in the future. Plant species can survive or resist wildfires and adapt to fire-prone regimes by exhibiting fire-related plant traits such as serotiny and heat-simulated germination. Resprouting is one of the most common plant traits that confer resilience to fire, promoting rapid post-fire recovery and affecting ecosystem dynamics. We investigated the relationships between the abundance of resprouting woody species, fire return interval and fire intensity in three regions: Europe, Australia and South and Central America. Species abundance data were obtained from the SplotOpen database while resprouting information are derived from regional and global databases, field information and the literature. Fire return time and fire intensity at each site were estimated using remotely sensed observations (MODIS MCD64CMQ, MODIS MCD14ML and Fire Atlas). We show that the abundance of resprouting woody species decreases with increasing fire return interval but that resprouters are most abundant at intermediate levels of fire intensity. These patterns are seen in all the three regions. Given that the abundance of resprouting woody species is strongly related to the fire regime, it should be possible to model their distribution in an optimality framework. Since the abundance of resprouters will affect ecosystem post-fire recovery, it is important to include this trait in fire-enabled vegetation models in order to simulate ecosystem dynamics adequately.

How to cite: Shen, Y., Prentice, C., and Harrison, S.: Investigating woody species resprouting in response to fire, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1007, https://doi.org/10.5194/egusphere-egu22-1007, 2022.

EGU22-1169 | Presentations | BG1.2

Recent and future intense fire seasons in the Mediterranean basin: the increasing role of droughts and heatwaves 

Ricardo Trigo, Marco Turco, Sonia Jerez, Pedro Sousa, Ana Russo, and Julien Ruffault

Mediterranean ecosystems are prone to forest fires, as evidenced by several extreme fire seasons which struck in the last two decades, including both western (2003, 2005, 2017) and eastern (2007, 2018, 2021) Mediterranean sectors. These fire seasons had a massive impact on the economy and the environment, having also caused many human casualties, including 145 in Portugal 2017 and about 100 in Greece 2018. Moreover, it is now widely accepted that these outstanding fire seasons are often associated with unusually intense droughts and heatwaves (Turco et al., 2019; Ruffault et al, 2020). Additionally, there is strong evidence that the frequency of drought events in the Mediterranean basin has increased significantly in the last decades and is bound to increase further under different climate change scenarios (Tramblay et al., 2020).

The relentless tendency for increasing summer temperatures in Europe in recent decades, when compared to the last 500 hundred years, also underlines that the increment in temperatures is extensive to central and Scandinavian countries (Sousa et al., 2020), where forest fires have become considerably more frequent. Recent assessments have emphasised the synergy between drought and extremely hot summers in the Mediterranean (Russo et al., 2020).

In addition to this climate change scenarios point to a likely increase in the frequency of two specific heat-induced fire-weather types, precisely those that have been related to the largest wildfires observed in recent years (Ruffault et al., 2020). Heat-induced fire-weather types are characterized by compound dry and warm conditions occurring during summer heatwaves, either under moderate (heatwave type) or intense (hot drought type) drought. The frequency of heat-induced fire-weather is projected to increase by 14% by the end of the century (2071-2100) under the RCP4.5 scenario, and by 30% under the RCP8.5. In summary, these results consistently suggest that the frequency and extent of wildfires will increase throughout the Mediterranean Basin.

 

Ruffault J., Curt T., Moron V., Trigo R.M., Mouillot F., Koutsias N., Pimont F., Martin-StPaul N., Barbero R., Dupuy J.-L., Russo A., Belhadj-Khedher C., (2020) Scientific Reports, 10, 13790, doi: 10.1038/s41598-020-70069-z

Russo A., Gouveia C.M., Dutra E., Soares P.M.M., Trigo R.M.  (2019) Environmental Research Letters, 14(1), 014011, doi: 10.1088/1748-9326/aaf09e

Sousa P., Barriopedro D., García-Herrera R., Ordoñez C., Soares P.MM, Trigo R.M. (2020) Communications Earth & Environment, 1, 48, doi: 10.1038/s43247-020-00048-9

Turco M., Jerez S., Augusto S., Tarín-Carrasco P., Ratola N., Jimenez-Guerrero P., Trigo, R.M. (2019) Scientific Reports, 9, 1, doi: 10.1038/s41598-019-50281-2

 

This work was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017). M.T. is supported by the Spanish Ministry of Science, Innovation and Universities - Spanish State Research Agency and the European Regional Development Fund through the PREDFIRE projects (RTI2018-099711-J-I00, MCI/AEI/FEDER, EU) and the Ramón y Cajal grant (RYC2019-027115-I). S.J. thanks the Spanish Ministry of Science, Innovation and Universities - Agencia Estatal de Investigación and the European Regional Development Fund for the support received through the EASE project (RTI2018 100870 A I00).

How to cite: Trigo, R., Turco, M., Jerez, S., Sousa, P., Russo, A., and Ruffault, J.: Recent and future intense fire seasons in the Mediterranean basin: the increasing role of droughts and heatwaves, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1169, https://doi.org/10.5194/egusphere-egu22-1169, 2022.

EGU22-1217 | Presentations | BG1.2 | Highlight

Palaeofire: current status and future opportunities 

Sandy Harrison, Daniel Gallagher, Paul Lincoln, Mengmeng Liu, Yicheng Shen, Luke Sweeney, and Roberto Villegas-Diaz

Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. The Reading Palaeofire Database (RPD) represents the most comprehensive compilation of sedimentary charcoal data currently available. It contains 1673 individual charcoal records from 1480 sites worldwide, with sufficient metadata to allow for the appropriate selection of sites to address specific questions. Most of the records have new age models, made by re-calibrating the radiocarbon ages using INTCAL2020 and Bayesian age-modelling software. In this talk we will show how these data are being used to document changing fire regimes during the Late Quaternary and to explore how fire regimes have responded to changes in climate, vegetation and human activities. We will demonstrate the progress that has been made to calibrate the charcoal records and make quantitative estimates of fire properties. We will also explore how these data can be used to evaluate and benchmark process-based fire-enabled models. Finally, we will highlight opportunities to use the palaeo-record together with models to explore fire regimes and their consequences for land-surface processes, biogeochemical cycles and climate.

How to cite: Harrison, S., Gallagher, D., Lincoln, P., Liu, M., Shen, Y., Sweeney, L., and Villegas-Diaz, R.: Palaeofire: current status and future opportunities, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1217, https://doi.org/10.5194/egusphere-egu22-1217, 2022.

EGU22-1372 | Presentations | BG1.2

Pyrogenic carbon decomposition critical to resolving fire's role in the Earth system 

Simon P.K. Bowring, Matthew W. Jones, Philippe Ciais, Bertrand Guenet, and Samuel Abiven

Recently identified post-fire carbon fluxes indicate that in order to understand if global fires represent a net carbon source or sink, one must consider both terrestrial carbon retention through pyrogenic carbon (PyC) production, and carbon losses via multiple pathways. Here, these legacy source and sink pathways are quantified using a CMIP6 land surface model to estimate Earth's fire carbon budget. Over 1901-2010, global PyC drives annual soil carbon accumulation of 337 TgCyr-1, offset by legacy carbon losses totalling -248 TgCyr-1. The residual of these values constrains maximum annual pyrogenic carbon mineralisation to 89 TgCyr-1, and PyC mean residence time to 5387 years, assuming steady state.   However, paucity of observational constraints for representing PyC mineralisation mean that without assuming steady state, we are unable to determine the sign of the overall fire carbon balance. 

The residual is negative over forests and positive over grassland-savannahs (implying a potential sink), suggesting contrasting roles of vegetation in the fire carbon cycle. Without widespread tropical grassland-savannah coverage, the legacy effects of fires could not feasibly enhance terrestrial C storage -a result afforded by grasses’ capacity for fire recovery. The dependency of the fire C residual on vegetation composition suggests that the preservation/restoration of native grasslands may be an important vector for decreasing C losses from future fire activity. We call for significant investments in understanding of PyC degradation and its drivers, in addition to improved estimates of legacy fire C fluxes. Reliable quantification of PyC mineralisation and erosion, particularly over grasslands, remains the principal missing link in a holistic understanding of fire’s role in the Earth system.

How to cite: Bowring, S. P. K., Jones, M. W., Ciais, P., Guenet, B., and Abiven, S.: Pyrogenic carbon decomposition critical to resolving fire's role in the Earth system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1372, https://doi.org/10.5194/egusphere-egu22-1372, 2022.

EGU22-1671 | Presentations | BG1.2

Representing socio-economic factors in INFERNO using the Human Development Index 

Joao Teixeira, Chantelle Burton, Douglas I. Kelley, Gerd Folberth, Fiona M. O'Connor, Richard Betts, and Apostolos Voulgarakis

INFERNO human fire ignitions and fire suppression functions excluded the representation of socio-economic factors (aside population density) that can affect anthropogenic behaviour regarding fire ignitions. To address this, we implement a socio-economic factor in the fire ignition and suppression parametrisation in INFERNO based on an Human Development Index (HDI) term. The HDI is calculated based on three indicators designed to capture the income, health, and education dimensions of human development. Therefore, we assume this leads to a representation where if there is more effort in improving human development, there is also investment on higher fire suppression by the population. Including this representation of socio-economic factors in INFERNO we were able to reduce large positive biases that were found for the regions of Temperate North America, Central America, Europe and Southern Hemisphere South America without significant impact to other regions, improving the model performance at a regional level and better representing processes that drive fire behaviour in the Earth System.

How to cite: Teixeira, J., Burton, C., Kelley, D. I., Folberth, G., O'Connor, F. M., Betts, R., and Voulgarakis, A.: Representing socio-economic factors in INFERNO using the Human Development Index, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1671, https://doi.org/10.5194/egusphere-egu22-1671, 2022.

EGU22-1916 | Presentations | BG1.2

Application of biochar to irrigated technosoils: Effects on germination and agronomic properties 

José María De la Rosa, Paloma Campos, Arturo Santa-Olalla, Águeda Sanchez-Martín, Ana Miller, and Elena Fernández-Boy

Today's agriculture faces the challenge of safely feeding a growing population. This situation generates additional pressures on the environment such as increased organic waste generation, irrigated cropland and the consumption of mineral fertilizers. Moreover, in the present context of global warming, it is necessary to transform the linear economy into a circular economy, in which organic waste should be valorized and greenhouse gas emissions reduced. During the last decade the transformation of organic waste into biochar, the carbon-rich material produced during pyrolysis of biomass to be applied as soil ameliorant [1], to increase the amount of pyrogenic C at soils have been developed [2]. Here, green compost and biochar were produced from contrasting agricultural wastes and applied at greenhouse under limited irrigation conditions.

Results showed that raw material, together with the pyrolysis conditions, determined physical properties of biochars, and thus its performance as soil amendment. In all cases, an increase in the pyrogenic carbon content and a general improvement in the physical properties of agronomic interest of the technosoils were observed. However, the use of high doses of olive-pomace biochar negatively affected the germination due to its high salinity.

Biochar, although beneficial, is therefore not a universal solution and must be characterized, have the appropriate properties and be applied in a specific way to correct specific soil deficiencies.

Acknowledgements: The BBVA foundation is gratefully acknowledged for funding the scholarship Leonardo to “Investigadores y Creadores Culturales 2020” (Proyecto realizado con la Beca Leonardo a Investigadores y Creadores Culturales 2020 de la Fundación BBVA).

References:

[1] Campos, P., Miller, A., Knicker, H., Costa-Pereira, M., Merino, A., De la Rosa, J.M., 2020. Waste Manag., 105, 256-267.

[2] De la Rosa, J.M., Rosado, M., Paneque, M., Miller, A.Z., Knicker, H., 2018. Sci. Tot. Environ., 613-614, 969-976.

How to cite: De la Rosa, J. M., Campos, P., Santa-Olalla, A., Sanchez-Martín, Á., Miller, A., and Fernández-Boy, E.: Application of biochar to irrigated technosoils: Effects on germination and agronomic properties, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1916, https://doi.org/10.5194/egusphere-egu22-1916, 2022.

EGU22-2442 | Presentations | BG1.2

Pyrogenic carbon from wildfire or from the laboratory 

Daquan Sun

Wildfires remove well-developed vegetation but restore it from an ecological point of view, although they are often called disasters when their intensity and extent in forests are large. Thermochemical decomposition of organic material at high temperatures (200 - 750 °C) in the absence of oxygen (or any halogen) to decompose biosolids has been recognised as a method with numerous benefits for waste management, carbon sequestration and sustainable agriculture. The effects of pyrogenic carbon (PyC) from wildfire and from the laboratory are believed to be different. The evidence to date is informative in bridging pyrogenic carbon from wildfire and pyrolysis, including aspects of: 1) PyC as a microsite for microbial communities; 2) the role of PyC of different sizes in soil aggregation; 3) the role of the soil microbiome in soil aggregation; 4) nutrient release - phosphorus availability in PyC. Future work is needed to investigate 1) the role of nano- or micro-sized PyC in the guts of soil fauna - nutrient uptake and function of the microbiome; 2) linking municipal biowaste to carbon sequestration; 3) improving efficiency in composting and vermicomposting; and 4) negative impacts on soil fauna such as earthworms. Knowledge of PyC in materials science, waste management and environmental microbiology offers opportunities to make breakthroughs in biowaste management and climate change mitigation.

How to cite: Sun, D.: Pyrogenic carbon from wildfire or from the laboratory, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2442, https://doi.org/10.5194/egusphere-egu22-2442, 2022.

EGU22-2463 | Presentations | BG1.2

Role of human impact on fire history and vegetation succession in one of the oldest protected forests in Europe 

Niina Kuosmanen, Tuomas Aakala, and Heikki Seppä

Fire is naturally an integral part of the northern boreal forests dynamics. However, anthropogenic activity has greatly affected the fire history in Fennoscandia, especially during the last millennia and the effective fire suppression practically led to the absence of a natural fire regime in boreal forests in Finland. However, the changing climate conditions may increase the risk of severe fire events regardless of the fire management. Therefore, it is important to look into the long-term interactions between human impact, fire and vegetation succession in order to understand the possible future role of fire in boreal forests.

One of the oldest protected areas in Europe is located in Central Finland and provides a good opportunity to investigate the change from natural fire and vegetation dynamics to human controlled fire regime and the natural vegetation succession after cessation of the slash-and-burn cultivation. The site is known to have been under slash-and-burn cultivation until the beginning of the 19th century and the last known burnings were done in the 1840s after which the site has been left to natural succession. The site was partly protected in 1911 and it was included into national the old-growth forest reserve protection program in 1994.

In order to investigate the long-term natural fire history and the role of human impact in the fire and the vegetation dynamics during last 3000 years we collected peat cores covering from two small forest hollows from the Kuusmäki old-growth forests protected area. Macroscopic (> 150 µm) charcoal and Neurospora-fungal spores are used to reconstruct the fire history and pollen analysis is performed to reconstruct the long-term vegetation dynamics in the study area.

The preliminary results demonstrate an increase in charcoal abundance from 16th century suggesting increased fire activity and a more intensive period of slash and burn cultivation in the area until the beginning of the 19th century. The absence of charcoal during the last century suggests absence of fire after the cessation of slash and burn cultivation. These results together with the vegetation succession will be further discussed in the presentation.

How to cite: Kuosmanen, N., Aakala, T., and Seppä, H.: Role of human impact on fire history and vegetation succession in one of the oldest protected forests in Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2463, https://doi.org/10.5194/egusphere-egu22-2463, 2022.

Paddy stubble burning is a major environmental issue that plagues the ambient air quality of the Indo-Gangetic Plain. Every year, during the post-monsoon season (October and November), approximately 17 million tons of paddy stubble are burnt openly in the fields of Punjab and Haryana. Over two months, this large-scale biomass burning results in persistent smog and severely perturbs the regional air quality. The emission of reactive gaseous pollutants like volatile organic compounds (VOCs) from this source drive the surface ozone and aerosol formation. However, there is a considerable knowledge gap regarding their identification, amounts and spatial distribution over North India. Widely used top-down global fire emission inventories like GFED, GFAS and FINN rely on the high-resolution MODIS and VIIRS satellite fire products. However, they are severely constrained by the missed fires, limited VOC speciation and uncertain biomass burnt calculations due to non-region-specific emission and land use parametrization factors. The current bottom-up emission estimates also have high uncertainties because of non-region-specific emission factors and burning practices. This work presents a new “hybrid” gridded emission inventory for paddy stubble burning over Punjab and Haryana in 2017 at 1 km × 1 km spatial resolution. First, the emission factors (EFs) of 77 VOCs were measured in smoke samples collected from the on-field paddy fires of Punjab. These were then combined with 1 km × 1 km stubble burning activity, constrained by annual crop production yields, regional rice cultivars, burning practices and satellite-detected fire radiative power. The results revealed that paddy stubble burning is a significant source of oxygenated VOCs like acetaldehyde (37.5±9.6 Ggy-1), 2-furaldehyde (37.1±12.5 Ggy-1), acetone (34.7±13.6 Ggy-1), and toxic VOCs like benzene (9.9±2.8 Ggy-1) and isocyanic acid (0.4±0.2 Ggy-1). These compounds are also significantly underestimated and unaccounted for by existing top-down and bottom-up emission inventories. Additionally, it was found that the emissions of NMVOC (346±65 Ggy-1), NOx (38±8 Ggy-1), NH3 (16±4 Ggy-1), PM2.5 (129±9 Ggy-1), GHG CO2 equivalents (22.1±3.7 Tgy-1) from paddy stubble were up to 20 times higher than the corresponding emissions from traffic and municipal waste burning over north-west India during October and November 2017. Mitigation of this source alone can yield massive air-quality climate co-benefits for more than 500 million people.

How to cite: Kumar, A., Hakkim, H., Sinha, B., and Sinha, V.: Gridded 1 km × 1 km emission inventory for paddy stubble burning emissions over north-west India constrained by measured emission factors of 77 VOCs and district-wise crop yield data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2565, https://doi.org/10.5194/egusphere-egu22-2565, 2022.

Biochar has become an accepted soil amendment due to its potential to improve soil properties and as a tool to increase carbon sequestration. The latter is based on its relatively high biochemical recalcitrance augmenting the slow C pool after its addition to soils. However, newer studies indicated that the longevity of biochar and naturally produced pyrogenic organic matter (PyOM) in soils is lower than commonly assumed. Many of those studies are based on the determination of CO2 production changes or on the recovery of their isotopic labels in the soil after amendment of biochar or PyC incorporation. Most probably because of the lack of appropriate techniques to differentiate between the natural soil organic matter fraction and the added black carbon, only few reports are available which relate turn-over data with chemical alterations of biochar during aging or the impact of the latter on the quality of the total SOM pool.  In order to fill this gap, we applied virtual fractionation of SOM into different organic matter pools by different solid-state NMR techniques. Whereas the most common combines the determination of turnover rates via stable isotope techniques, an alternative approach takes advantage of different relaxation behavior of biochar and humified SOM. In both cases spectra can be calculated that show either the added biochar or the respective SOM.  In the frame of the present work, the concept and the potential of the two approaches will be explained by using examples studied in our laboratory.  With this, we intend to provide a further powerful tool which can lead to a better understanding of the biochemistry related to the transformation of PyC and biochar during aging and their subsequent integration into the soil organic matter fraction.

 

Acknowledgement: Financial support has been provided by the European Institute of Innovation and Technology (EIT), a body of the European Union, under Horizon2020, the EU Framework Programme for Research and Innovation (Project 21217 Black to the future - biochar and compost as soil amendment)

How to cite: Knicker, H., Knicker, M., García de Castro Barragán, J. M., and Velasco-Molina, M.: NMR-spectroscopic virtual fractionation of soils mixed with pyrogenic carbon as a tool to separate chemical processes related to aging of pyrogenic carbon from those occurring during humification of soil organic matter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2603, https://doi.org/10.5194/egusphere-egu22-2603, 2022.

EGU22-2611 | Presentations | BG1.2 | Highlight

Present and future tropical fire risks associated with compound events 

Andreia F. S. Ribeiro, Paulo M. Brando, Lucas Santos, Ludmila Rattis, Martin Hirschi, Mathias Hauser, Sonia I. Seneviratne, and Jakob Zscheischler

Complex interactions between climate and land-use are altering the course of the fire regimes across the tropics. In Brazil, many recent peaks of burned area have co-occurred with extreme climate events, high deforestation rates and agricultural expansion. Particularly during compound dry and hot years, widespread fires have become increasingly common, and an intensification of the fire activity due to climate change may be already underway.

Based on a compound-event-oriented framework to assess fire risk, we provide evidence on the extent to which fire activity and the associated impacts could be constrained if anthropogenic global warming is limited. Here we quantify the nonlinear relationships between compound climate drivers and burned area across two main Brazilian biocultural heritage sites (Xingu and Pantanal) and estimate compound-event-related fire risks in terms of the occurrences of compound drivers beyond which the fire response becomes extreme.

Our results show that the exponential response of burned area to climate is well explained by compound events characterized by air dryness and precipitation deficits (high VPD and low precipitation) and that climate-change induced fire risks will increase due to the co-occurrence of drier and warmer climatic conditions under global warming. However, if global warming is constrained to +1.5°C instead of +3°C, the likelihood of fire risk can be reduced by ~11% in the case of the most prominent fire types (forest fires in Xingu and grassland fires in the Pantanal). We thus conclude that if we slow down the rate of warming and follow more sustainable uses of land, we might be able to prevent the crossing of tipping points and the consequent downward spiral of socio-environmental impacts that threatens these regions.

How to cite: Ribeiro, A. F. S., Brando, P. M., Santos, L., Rattis, L., Hirschi, M., Hauser, M., Seneviratne, S. I., and Zscheischler, J.: Present and future tropical fire risks associated with compound events, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2611, https://doi.org/10.5194/egusphere-egu22-2611, 2022.

EGU22-3357 | Presentations | BG1.2

High concentrations of environmentally persistent free radicals in fire derived pyrogenic organic matter 

Gabriel Sigmund, Cristina Santin Nuno, Marc Pignitter, Nathalie Tepe, Stefan Helmut Doerr, and Thilo Hofmann

Fire derived pyrogenic organic matter / charcoal is a source of environmentally persistent free radicals, which are precursors of potentially harmful reactive oxygen species. We analyzed charcoal samples from ten wildfires, including crown as well as surface fires in boreal, temperate, subtropical and tropical climate regions. Concentrations of environmentally persistent free radicals in these samples were orders of magnitude higher than those found in soils or other “background” matrices, as measured via electron spin resonance spectroscopy. The highest concentrations were measured in woody charcoals that were highly carbonized. We also found that environmentally persistent free radicals remained unexpectedly stable in the field for at least 5 years.

More details can be found in our recently published article: https://www.nature.com/articles/s43247-021-00138-2

How to cite: Sigmund, G., Santin Nuno, C., Pignitter, M., Tepe, N., Doerr, S. H., and Hofmann, T.: High concentrations of environmentally persistent free radicals in fire derived pyrogenic organic matter, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3357, https://doi.org/10.5194/egusphere-egu22-3357, 2022.

EGU22-3871 | Presentations | BG1.2

Projected changes in variability of fire weather in boreal regions under different levels of global warming 

Marianne T. Lund, Kalle Nordling, Astrid B. Gjelsvik, and Bjørn H. Samset

Recent years have seen unprecedented fire activity at Arctic latitudes, leading to severe consequences including unhealthy air quality in high latitude towns and cities. While wildfire occurrence and severity result from a complex interplay between natural and anthropogenic factors, weather is a key factor.

Weather conditions that promote high wildfire risk are characterized by the combination of high temperatures, little precipitation and low humidity, and often high winds. All of these can be affected by human-induced climate change and evidence is emerging that wildfire risk is already increasing in many regions. Such changes not only manifest as shifts in the means and extremes of the weather variables but can also be changes in the shape of their distributions. The importance of the full, regional Probability Density Functions (PDFs) of individual and aggregated variables, which contain information on expected weather not apparent from the distribution mean or tails, but through changes to their overall shape, for understanding climate risk has been broadly discussed in the literature. Furthermore, while simulations with regional climate models to derive such information are costly and time consuming, the advent of large ensembles of coupled climate model simulations has recently opened new opportunities.

Here we present a detailed characterization of the distribution and variability of weather variables conducive to wildfire risk across five high-latitude boreal regions in North America, Scandinavia and Russia. Building on methodology developed in Samset et al. (2019), we quantify the PDFs of daily data for a broad set of individual variables, as well as for the aggregate change expressed using the Canadian Fire Weather Index. Using ensembles of coupled simulations from two climate models (CanESM5 and MPI-ESM1-2) and two CMIP6 scenarios (the Shared Socioeconomic Pathways SSP1-2.6 and SSP5-8.5), we consistently quantify the changes of regionally and seasonally resolved PDFs under different levels of global warming.  

Our results provide a comprehensive picture of the potential future changes in drivers of fire weather and wildfire risk in the pan-Arctic region and demonstrate the difference between regions. We also show how statistical descriptions combined with emulation of Earth System Model (ESM) information can offer an alternative pathway to resource demanding model runs, for rapidly translating science to user-oriented information.

How to cite: Lund, M. T., Nordling, K., Gjelsvik, A. B., and Samset, B. H.: Projected changes in variability of fire weather in boreal regions under different levels of global warming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3871, https://doi.org/10.5194/egusphere-egu22-3871, 2022.

EGU22-3927 | Presentations | BG1.2

Siberian fire ignition caused by the dry lightning activity 

Jin-Soo Kim, Seung-Ki Min, Min-Gyu Seong, Daehyun Kim, Robert Holzworth, Ja-Ho Koo, Axel Timmermann, and Gabriela Schaepman-Strub

Wildfire activity in Siberia (60E-180E, 55N-80N) has been observed to be more frequent and stronger in recent years. To understand the underlying mechanism of the positive trend in the frequency and strength of wildfire events, especially the role of lightning, we analyzed the relationship among fire ignition, Convective Available Potential Energy (CAPE), precipitation, and lightning flash density over Siberia using observations and reanalysis products for the period 2012–2020. A similar analysis was performed on an ultra-high-resolution (25-km) climate model simulation made with Community Earth System Model version 1.2.2 (CESM) under a greenhouse gas-induced warming scenario. In the observations, we found that while the number of lightning flashes is proportional to CAPE and precipitation, the number of fire ignition is only proportional to CAPE. In particular, we identified a threshold of 3.5 mm/day of precipitation, below which fire ignition occurs more frequently. Our analyses reveal that precipitation plays a role in suppressing fire ignition, but dry lightning with high CAPE and low precipitation effectively cause fire ignitions. In the CESM simulation, we found a robust increase in the number of days with high CAPE (> 700 J/kg) and low precipitation (< 3.5 mm/day), which suggests an increase in the frequency of dry lightning events, and therefore more lightning-induced wildfire events in Siberia.

How to cite: Kim, J.-S., Min, S.-K., Seong, M.-G., Kim, D., Holzworth, R., Koo, J.-H., Timmermann, A., and Schaepman-Strub, G.: Siberian fire ignition caused by the dry lightning activity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3927, https://doi.org/10.5194/egusphere-egu22-3927, 2022.

EGU22-4095 | Presentations | BG1.2

Emission characteristics of atmospheric pollutants from field-scale crop residue burning in Northeast China 

Lili Wang, Qinglu Wang, Miaomiao Cheng, Tianran Zhang, and Jinyuan Xin

Crop residue burning in china increased significantly in the last decade, especially it took up a majority in Northeast China, which plays an important role of severe haze pollution. Hence, two main types of crop residues (corn and rice straw) were chosen to characterize the particle number concentration, chemical components of fine particulate matter and optical properties of carbonaceous aerosols by a suite of fast-response online portable instruments, together with offline sampling and analysis, during the field-based combustion experiments in Northeast China. For the range of 0.25 and 2.5 µm, more particles were emitted from rice straw burning than those from corn straw burning, and the time-averaged number concentration of particles during the flaming process was approximately 2 times higher than that during the smoldering process for these two straws. Organic carbon (OC), elemental carbon (EC) and water-soluble ions were the most abundant components and accounted for 42.5±7.5%, 7.7±1.7% and 18.0±3.4% of the PM2.5, respectively. Furthermore, rice straw burning emitted higher OC and lower Cl- and K+ than those from corn straw burning. The average absorption Ångström exponent (AAE) of carbonaceous aerosols was 2.1±0.3, while the AAE of brown carbon (BrC) was 4.7±0.4 during the whole burning process. On average, BrC contributed to 63% and 20% of the total light absorption at 375 nm and 625 nm, respectively. Parameterization of BrC absorption revealed that the fraction of absorption from BrC has a reasonably good correlation with EC/OC (-0.84) and AAE (0.94) at 375 nm. Generally, combustion conditions can affect the optical properties of carbonaceous aerosols, and a negative correlation (-0.77) was observed between the AAE and modified combustion efficiency; in addition, the percentage of absorption due to BrC were lower at the flaming phase. To explorer the spatial and temporal variability of open agricultural burning in Northeast China from 2014 to 2019, the emission inventory of key gaseous and particle pollutants was established, which derived from a combination of geostationary (Himawari) and polar (VIIRS) orbiter fire radiative power products. 

How to cite: Wang, L., Wang, Q., Cheng, M., Zhang, T., and Xin, J.: Emission characteristics of atmospheric pollutants from field-scale crop residue burning in Northeast China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4095, https://doi.org/10.5194/egusphere-egu22-4095, 2022.

EGU22-4271 | Presentations | BG1.2

Forest fire risk assessment with soil data in Croatia 

Diana Škurić Kuraži, Ivana Nižetić Kosović, and Ivana Herceg Bulić

Forest fire research can comprise forest fire case studies, laboratory experiments, fire detection by ground sensors, unmanned aerial vehicles and satellites, development of fire behaviour models, fire danger forecast, fire risk assessment, and much more. Commonly used and accepted Canadian method for forest fire danger forecast is expressed as Fire Weather Index (FWI) uses weather data. The index estimates the danger of wildfire and is based on meteorological parameters (air temperature, air humidity, wind speed, and rainfall amount) referring to 12 UTC for that day at the meteorological station or on a numerical weather prediction model grid point.

Knowing how weather and soil interact and affect each other, we propose a new fire risk index based on the innovative Soil Index. Using open-access data, we collected different soil data such as soil temperature and soil moisture, land cover, vegetation, slope, etc. Since there are different types of vegetation and states, Leaf Area Index (LAI) and Normalized Difference Vegetation Index (NDVI) are considered as well. Being focused on forest fires, data about the burned area were also taken into account as well as the slope of the terrain for which the fire risk is calculated.

Since all mentioned data have a diverse horizontal and temporal resolution, we decided to group them by temporal resolution: static, semi-static, and dynamic data. Static data refers to data that rarely change (never or every few years; e.g. land cover). Semi-static data refers to data that vary weekly or monthly (e.g. LAI). Dynamic data group refers to data that is strongly influenced by weather conditions (like soil temperature) and varies every hour. Because of various horizontal resolutions, soil parameters are interpolated to the same horizontal grid. Soil parameters are analysed concerning historical forest fires in Croatia. Despite Soil Index being based on soil parameters, we compared it with Fire Weather Index using data records for historical forest fires in Croatia. Obtained results indicate that the soil index has a better prediction performance compared to FWI. This study also highlights that not only the meteorological environment but also soil conditions are important parameters for fire risk assessment.

How to cite: Škurić Kuraži, D., Nižetić Kosović, I., and Herceg Bulić, I.: Forest fire risk assessment with soil data in Croatia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4271, https://doi.org/10.5194/egusphere-egu22-4271, 2022.

EGU22-4394 | Presentations | BG1.2

Fire aerosols slow down the global water cycle 

Fang Li, David Lawrence, Yiquan Jiang, and Xiaohong Liu

Fire is an important Earth system process and the largest source of global primary carbonaceous aerosols. Earlier studies have focused on the influence of fire aerosols on radiation, surface climate, air quality, and biogeochemical cycle. The impact of fire aerosols on the global water cycle has not been quantified and related mechanisms remain largely unclear. This study provides the first quantitative assessment and understanding of the influence of fire aerosols on the global water cycle. This is done by quantifying the difference between simulations with and without fire aerosols using the fully-coupled Community Earth System Model (CESM). Results show that presentday fire aerosols weaken the global water cycle significantly. They decrease the continental precipitation, evapotranspiration, and runoff by 4.1±1.8, 2.5±0.5, and 1.5±1.4 ×103 km3 yr-1 as well as ocean evaporation, precipitation, and water vapor transport from ocean to land by 8.1±1.9, 6.6±2.3, and 1.5±1.4 ×103 km3 yr-1. The impacts of fire aerosols are most clearly seen in the tropics and the Arctic-boreal zone. Fire aerosols affect the global water cycle mainly by cooling the surface which reduces ocean evaporation, land soil evaporation and plant transpiration. The decreased water vapor load in the atmosphere leads to a decrease in precipitation, which contributes to reduced surface runoff and sub-surface drainage.

How to cite: Li, F., Lawrence, D., Jiang, Y., and Liu, X.: Fire aerosols slow down the global water cycle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4394, https://doi.org/10.5194/egusphere-egu22-4394, 2022.

EGU22-4551 | Presentations | BG1.2

Fire prevents the regrowth of the Amazon rainforest after complete deforestation in a fire-enabled Earth system model 

Markus Drüke, Werner von Bloh, Boris Sakschewski, Wolfgang Lucht, and Kirsten Thonicke

The terrestrial biosphere is exposed to land use and anthropogenic climate change, which not only affects vegetation dynamics, but also changes land-atmosphere feedbacks. In particular, tropical rainforests are endangered by anthropogenic activities and are recognized as one of the terrestrial tipping elements. An ecosystem regime change to a new state could have profound impacts on regional and global climate, once the biome has transitioned from a forest into a savanna or grassland state. Fire is a potentially major driver in the position of the transition boundary and could hence impact the dynamic equilibrium between these possible vegetation states under a changing climate. However, systematic tests of fire-controlled tipping points and hysteretic behaviour using comprehensive Earth system models are still lacking.

Here, we specifically test the recovery of the Amazon rainforest after a complete deforestation at different atmospheric CO2 levels, by using the Earth system model CM2Mc-LPJmL v1.0 with a state-of-the-art representation of vegetation dynamics and fire. We find that fire prevents large-scale forest regrowth after complete deforestation and locks large parts of the Amazon in a stable grassland state. While slightly elevated atmospheric CO2 values had beneficial effects on the forest regrowth efficiency due to the fertilization effect, larger CO2 amounts further hampered the regrowth due to increasing heat stress. In a no-fire control experiment the Amazon rainforest recovered after 250 years to nearly its original extent at various atmospheric CO2 forcing levels. This study highlights the potential of comprehensive fire-enabled Earth system models to investigate and quantify tipping points and their feedback on regional and global climate.

How to cite: Drüke, M., von Bloh, W., Sakschewski, B., Lucht, W., and Thonicke, K.: Fire prevents the regrowth of the Amazon rainforest after complete deforestation in a fire-enabled Earth system model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4551, https://doi.org/10.5194/egusphere-egu22-4551, 2022.

EGU22-4571 | Presentations | BG1.2

Molecular characterisation of soil organic matter under different burned vegetation canopies 

Nicasio T. Jiménez-Morillo, Ana Z. Miller, Nuno Guiomar, José M. De la Rosa, Cristina Barrocas-Dias, Ana Manhita, and José A. González-Pérez

Forest fires are a recurrent ecological phenomenon in the Mediterranean basin. They induce molecular changes in soil organic matter (SOM) leading to immediate and long-term environmental consequences [1]. The SOM is of paramount importance as indicator of soil health [2]. Fire-induced changes in SOM include the alteration of biogenic chemical structures and the accumulation of newly formed ones, enhancing dynamics in the complex balance between the different C-types [2,3]. Therefore, understanding SOM molecular composition, before and after fire, is fundamental to monitor changes in soil health, as well as its natural or man-mediated recovery [3,4]. Our aim was to assess the molecular composition of organic matter in fire-affected leptosols, at two depths (0–2 and 2–5 cm) under different vegetation types located in the southwestern of Portugal (Aljezur, Algarve). The SOM characterization was conducted by analytical pyrolysis (Py-GC/MS), a technique based on the thermochemical breakdown of organic compounds in the absence of oxygen at elevated temperatures [5]. The Py-GC/MS has been found suitable for the structural characterization of complex organic matrices [4], providing detailed structural information of individual compounds considered fingerprinting of SOM. However, due to the relative high number of molecular compounds released by analytical pyrolysis, the use of graphical-statistical methods, such as van Krevelen diagrams, are usually applied to help monitoring SOM molecular changes produced by fire [3,4]. This work represents the first attempt to evaluate the fire effects in SOM using a detailed molecular characterisation of SOM under different vegetation canopies, recently affected by wildfire, in southern Portugal.

 

References:

[1] Naveh, Z., 1990. Fire in the Mediterranean – a landscape ecological perspective. In: Goldammer, J.G., Jenkins, M.J. (Eds.), Fire in Ecosystems Dynamics: Mediterranean and Northern Perspective. SPB Academic Publishing, The Hague.

[2] González-Pérez, J.A., González-Vila, F.J., Almendros, G., Knicker, H., 2004. The effect of fire on soil organic matter—a review. Environ. Int. 30, 855–870.

[3] Jiménez-Morillo, N.T., De la Rosa, J.M., Waggoner, D., et al., 2016. Fire effects in the molecular structure of soil organic matter fractions under Quercus suber cover. Catena 145, 266–273.

[4] Jiménez-Morillo, N.T.; Almendros, G.; De la Rosa, J.M.; et al., 2020. Effect of a wildfire and of post-fire restoration actions in the organic matter structure in soil fractions. Sci. Total Environ. 728, 138715.

[5] Irwin, W.J., 1982. Analytical pyrolysis—a comprehensive guide. In: Cazes, J. (Ed.), Chromatographic Science Series, 22: Chapter 6. Marcel Dekker, New York.

 

Acknowledgments: This work was funded by national funds through FCT–Fundação para a Ciência e a Tecnologia (EROFIRE project, ref. PCIF-RPG-0079-2018). This research was funded by the European Union through the European Regional Development Funds in the framework of the Interreg V A Spain-Portugal program (POCTEP) through the CILIFO (Ref.: 0753_CILIFO_5_E) and FIREPOCTEP (Ref.: 0756_FIREPOCTEP_6_E) projects. In addition, this research was funded by the EU-FEDER co-funded project MARKFIRE (ref. P20_01073) from Junta de Andalucía. A.Z.M was supported by a CEECIND/01147/2017 contract from FCT, and a Ramón y Cajal contract (RYC2019-026885-I) from the Spanish Government (Ministerio de Ciencia en Innovación – MCIN).

How to cite: Jiménez-Morillo, N. T., Miller, A. Z., Guiomar, N., De la Rosa, J. M., Barrocas-Dias, C., Manhita, A., and González-Pérez, J. A.: Molecular characterisation of soil organic matter under different burned vegetation canopies, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4571, https://doi.org/10.5194/egusphere-egu22-4571, 2022.

EGU22-4831 | Presentations | BG1.2

Influence of Atmospheric Teleconnections on Interannual Variability of Arctic-boreal Fires 

Zhiyi Zhao, Zhongda Lin, Fang Li, and Brendan M. Rogers

Fires across the Arctic-boreal zone (ABZ) play an important role in the boreal forest succession, permafrost thaw, and the regional and global carbon cycle and climate. These fires occur mainly in summer with large interannual variability. Previous studies primarily focused on the impacts of local surface climate and tropical El Niño-Southern Oscillation (ENSO). This study, for the first time, comprehensively investigates the influence of summer leading large-scale atmospheric teleconnection patterns in the Northern Hemisphere extra-tropics on interannual variability of ABZ fires. We use correlation and regression analysis of 1997–2019 multiple satellite-based products of burned area and observed/reanalyzed climate data. Results show that eight leading teleconnection patterns significantly affect 63±2% of burned areas across the ABZ. Western North America is affected by the East Pacific/North Pacific pattern (EP/NP) and the West Pacific pattern (WP); boreal Europe by the Scandinavia pattern (SCA); eastern North America, western and central Siberia, and southeastern Siberia by the North Atlantic Oscillation (NAO); and eastern Siberia /Russian Far East by the East Atlantic pattern (EA). NAO/EA induces lower-tropospheric drier northwesterly/northerly airflow passing through the east of boreal North America/Eurasia, which decreases surface relative humidity. Other teleconnections trigger a high-pressure anomaly, forcing downward motion that suppresses cloud formation and increases solar radiation reaching the ground to warm the surface air as well as brings drier air downward to reduce surface relative humidity. The drier and/or warmer surface air can decrease fuel wetness and thus increase burned area. Our study highlights the important role of the extra-tropical teleconnection patterns on ABZ fires, which is much stronger than ENSO that was thought to control interannual variability of global fires. It also establishes a theoretical foundation for ABZ fire prediction based on extra-tropical teleconnections, and has the potential to facilitate ABZ fire prediction and management.

How to cite: Zhao, Z., Lin, Z., Li, F., and Rogers, B. M.: Influence of Atmospheric Teleconnections on Interannual Variability of Arctic-boreal Fires, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4831, https://doi.org/10.5194/egusphere-egu22-4831, 2022.

EGU22-4922 | Presentations | BG1.2 | Highlight

Development of an arctic-boreal fire atlas using Visible Infrared Imaging Radiometer Suite active fire data 

Rebecca Scholten, Yang Chen, James Randerson, and Sander Veraverbeke

Intensifying wildfires in high-latitude forest and tundra ecosystems are a major source of greenhouse gas emissions, releasing carbon through direct combustion and long-term degradation of permafrost soils and peatlands. Several remotely sensed burned area and active fire products have been developed, yet these do not provide information about the ignitions, growth and size of individual fires. Such object-based fire data is urgently needed to disentangle different anthropogenic and bioclimatic drivers of fire ignition and spread. This knowledge is required to better understand contemporary arctic-boreal fire regimes and to constrain models that predict changes in future arctic-boreal fire regimes. 
Here, we developed an object-based fire tracking system to map the evolution of arctic-boreal fires at a sub-daily scale. Our approach harnesses the improved spatial resolution of 375m Visible Infrared Imaging Radiometer Suite (VIIRS) active fire detections. The arctic-boreal fire atlas includes ignitions and daily perimeters of individual fires between 2012 and 2021, and may be complemented in the future with information on waterbodies, unburned islands, fuel types and fire severity within fire perimeters. 

How to cite: Scholten, R., Chen, Y., Randerson, J., and Veraverbeke, S.: Development of an arctic-boreal fire atlas using Visible Infrared Imaging Radiometer Suite active fire data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4922, https://doi.org/10.5194/egusphere-egu22-4922, 2022.

EGU22-5199 | Presentations | BG1.2

Global changes, fire and spruce-forest dynamics in Québec-Labrador during the Holocene. 

Jonathan Lesven, Milva Druguet-Dayras, Laurent Millet, Adam Ali, Yves Bergeron, André Arsenault, François Gillet, and Damien Rius

Context

Boreal ecosystems provide numerous goods and services essential to human activities, such as wood and paper supply or the regulation of natural phenomena (floods, diseases) (Hassan et al., 2005). They also play a major role in the global climate balance, storing ~32% of the world's biogenic carbon (Pan et al., 2011; Bradshaw, 2015). Their dynamics are also intrinsically linked to fire activity, main disturbance driver in North American boreal forests (Kuuluvainen and Aakala, 2011), mainly controlled by climate-vegetation interactions (Ali et al., 2012). Under global warming, recent work predicts an increase of fire regimes, and a potential shift of the carbon sink function (Walker et al., 2019). However, Labrador and eastern Quebec regions remain poorly studied on multimillennial time scales. This study provides new insights on fire-climate-vegetation interactions in eastern Canadian forests, allowing us to better characterize the mechanisms by which climate change impacts fire regimes, and consequently forest structure and functioning.

 

Material and methods

To cover a wide range of fire-climate-vegetation interactions, this study is based on a North-South transect of 5 lacustrine sediment cores, covering the last 6,000 to 10,000 years across Quebec and Labrador regions. Chronologies were based on 210Pb/137Cs and 14C dating. Finally, to reconstruct local fire regimes, vegetation dynamics and climatic fluctuations during the Holocene, our study is based respectively on macrocharcoals (≥ 150 µm), pollen grains and chironomids assemblages.

 

Results and Discussion

Our study reveals that black spruce (Picea mariana (Mill.)) is the dominant species across the transect, but its proportion varies greatly, and is marked by a codominance with balsam fir in the south and with green alder in the north. In the south (white birch fir stand and spruce-lichen woodlands bioclimatic domains), our results show a high frequency but relatively low fire sizes during the warmest and driest periods, such as the Holocene Climate Optimum (HCO), followed by a reverse trend during the coldest and wettest periods such as the Neoglacial Period (NG), probably due to a longer fuel accumulation time promoting larger fires (Carcaillet et al., 2001). In the North (forest tundra bioclimatic domain), the HCO is marked by the absence of fire, whereas the NP is characterised by a strong increase in fire frequency, related to the progressive increase of black spruce after the deglaciation. Despite this north-south contrast, possibly related to the impact of the Atlantic Ocean, all sequences show an increase in both fire frequency and size after the industrial revolution, inducing a major change in vegetation trajectory towards more open environments marked by an increase in pioneer taxa.

 

Conclusion

During the Holocene, climate change induced variations in fire regimes in eastern Canada, but show spatial differences explained by black spruce dynamics and moisture inputs. Our study also reveals that temperature rises over the last 150 years have led to an increase in the frequency and size of fires and consequently to a progressive opening of the environment. This could ultimately alter the carbon sink function of boreal forests in the future (Bastianelli et al., 2017).

How to cite: Lesven, J., Druguet-Dayras, M., Millet, L., Ali, A., Bergeron, Y., Arsenault, A., Gillet, F., and Rius, D.: Global changes, fire and spruce-forest dynamics in Québec-Labrador during the Holocene., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5199, https://doi.org/10.5194/egusphere-egu22-5199, 2022.

EGU22-5320 | Presentations | BG1.2

Accounting for the impact of slope on fire spread in a dynamic global vegetation model 

Luke Oberhagemann, Markus Drueke, Maik Billing, Werner von Bloh, Boris Sakschewski, Henning Rust, and Kirsten Thonicke

Fire modelling incorporated into global dynamic vegetation models (DGVMs) allows for the projection of changes to fire-related biogeophysical and biogechemical processes under future climate scenarios, including anthropogenic climate change. Due to the large grid sizes often required to efficiently model fire and vegetation dynamics in a global manner, fire-enabled DGVMs generally neglect some finer-scale effects, including slope. However, slope can have a significant impact on the spread of individual fires and, therefore, the global area burned. As a fire moves uphill, the angle of flames is better suited to heating nearby fuel, thus increasing the rate of spread relative to fires on level ground. In this study, we apply a function to account for the impact of slope on fire spread in the SPITFIRE model incorporated into the LPJmL5.3 DGVM to improve the calculation of fire-related processes, including burnt area. We aggregate slope data across a grid cell to account for the impact of slope in a general way appropriate to the  grid size used in SPITFIRE. Our approach, while focused on the SPITFIRE model, may also be applicable to other DGVM-based fire models.

How to cite: Oberhagemann, L., Drueke, M., Billing, M., von Bloh, W., Sakschewski, B., Rust, H., and Thonicke, K.: Accounting for the impact of slope on fire spread in a dynamic global vegetation model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5320, https://doi.org/10.5194/egusphere-egu22-5320, 2022.

Fires play a critical role in global biogeochemical and hydrological cycles through influencing vegetation succession and ecosystem functioning. Observational evidence shows that fire regimes across global ecosystems have been altered by climate change and human activities. However, most fire-enabled terrestrial biosphere models (TBMs) poorly capture the spatial and temporal patterns of fire ignitions, burned area, vegetation mortality and post-fire recovery. To improve our ability in predicting fire behavior and its impacts on the ecosystem and climate, it is essential to better represent fire-vegetation interactions in TBMs. Here, we improve the fire module of the Dynamic Land Ecosystem Model (DLEM-Fire) and optimize the parameters by using the satellite observed fire ignitions, burned area and leaf area index (LAI) products. Our results show that the improved fire model can describe the magnitude, spatial patterns, and interannual variations of burned area and vegetation mortality more accurately. Moreover, the model is capable of providing robust estimations of post-fire vegetation regeneration to characterize the vegetation resistance and resilience to fire disturbances. This study emphasizes the importance of integrating terrestrial biosphere models and satellite observation data for fire monitoring and prediction.

How to cite: Li, X., Tian, H., Yang, J., You, Y., and Pan, S.: Understanding and quantifying fire-vegetation interactions through integrating satellite observation data with the Dynamic Land Ecosystem Model (DLEM), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5893, https://doi.org/10.5194/egusphere-egu22-5893, 2022.

EGU22-6512 | Presentations | BG1.2

Likely future(s) of global wildfires 

Douglas I Kelley, Camilla Mathison, Chantelle Burton, Megan Brown, Andrew Sullivan, Elaine Baker, and Tiina Kurvits

We show likely substantial increases in burning by 2100 in Boreal and Tropical Forests irrespective of future emissions and after accounting for the (often considerable) uncertainties and biases in global fire and climate modelling. Rather than projecting future fire regimes directly, we used the ConFire Bayesian framework to model the likelihood of all possible future burning levels given historic fire and climate model performance. Driving the framework with bias-corrected outputs from four ISIMIP2b GCMs run under RCP2.6 and RCP6.0 accounts for uncertainties in future emissions and climate model projections. 

While we forecast the potential for substantial shifts in fire regimes of much of the world by the end of the century, many show low likelihood given our confidence in the fire, vegetation and climate model projections. Tropical savannas show the largest potential for change, though without confidence in the direction of change due to uncertainty in future precipitation projections.  An increase in dry fuel drives an increase in burnt area in northern Australia. However, this is not significant against uncertainty associated with present-day veg/fire model performance. There is a significant agreement for decreased burning in Southern Brazil, Uruguay and northern Argentina, and the US east coast under RCP2.6, but not RCP6.0.

We do show a high likelihood of drying fuel loads driving an increase in burning in Indonesia, Southern Amazon, central and eastern Siberian Taiga and many Arctic areas across RCPs. These areas are of particular concern given the potential to release the high carbon content of forests and peatlands irrecoverable carbon. Mitigating from RCP6.0 to 2.6 will likely alleviate some though not all of this burning. This is important for future mitigation planning and determining likely temperature and emission targets to avoid the worst impacts of fire in our warmer world.

How to cite: Kelley, D. I., Mathison, C., Burton, C., Brown, M., Sullivan, A., Baker, E., and Kurvits, T.: Likely future(s) of global wildfires, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6512, https://doi.org/10.5194/egusphere-egu22-6512, 2022.

EGU22-6549 | Presentations | BG1.2

Remote sensing of tropical vegetation properties in response to fire return time 

Ramesh K. Ningthoujam, Nayane Cristina Candida dos Santos Prestes, Marcelo Feitosa de Andrade, Maria Antonia Carniello, Corli Wigley Coetsee, Mark E. Harrison, Kitso Kusin, Azad Rasul, Agata Hoscilo, Adam Pellegrini, Imma Oliveras, Ted R. Feldpausch, Susan Page, Keith J. Bloomfield, Sandy P. Harrison, and Iain Colin Prentice

Fire modifies vegetation spectral reflectances in the optical, thermal and microwave domains due to the changes it induces in vegetation canopy components (leaves, needles, branches) and in soil properties. Freely available satellite-derived (Landsat) Vegetation Indices (VIs) and PALSAR Mosaic backscatter measurements (known to be sensitive to vegetation structure) were used to help understand vegetation properties (species richness, basal area) in relation to fire return time (FRT) across a range of tropical biomes (open savanna, savanna forest, evergreen forest, peat-swamp forest) in Mato Grosso (Brazil), Kruger National Park (South Africa) and Central Kalimantan (Indonesia).

For each site, we combined: (i) post-fire Landsat imagery (30 m) to derive VIs sensitive to vegetation diversity with (ii) PALSAR (25 m) backscatter that employes a longer wavelength (21 cm) and dual polarisation (Horizontal-Horizontal, Horizontal-Vertical) enabling the capture of strong backscattering of signal by branches and trunks.

Most of the Landsat VI values showed greater variability in forests compared to open savanna, reflecting the greater diversity in species’ composition and growth form. A strong positive relationship was found between VIs and FRT across biomes and especially in forests. The amount of vegetation burned per fire as recorded by the magnitude of changes in these VIs, was highest in annual burn regimes (FRT = 1 year). Green and red-edge bands provided better discrimination of vegetation species richness and basal area. A significant positive relationship to basal area in response to fire return time was also found using PALSAR data due to its deeper canopy penetration level and strong backscattering from woody components. The observed responses of VI- and PALSAR-inferred species’ richness and basal area in response to FRT in different tropical biomes suggest that the green and red-edge channels from optical and longer wavelength HV-backscatter are useful metrics to quantify post-fire tropical vegetation dynamics.

How to cite: Ningthoujam, R. K., Prestes, N. C. C. D. S., Andrade, M. F. D., Carniello, M. A., Coetsee, C. W., Harrison, M. E., Kusin, K., Rasul, A., Hoscilo, A., Pellegrini, A., Oliveras, I., Feldpausch, T. R., Page, S., Bloomfield, K. J., Harrison, S. P., and Prentice, I. C.: Remote sensing of tropical vegetation properties in response to fire return time, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6549, https://doi.org/10.5194/egusphere-egu22-6549, 2022.

Ever-increasing wildfires in scale and duration have resulted in enormous human and material losses, and adverse health outcomes due to short- and long-term exposure to diverse air pollutants emitted from fires. Historically, the Mediterranean Basin, characterized by hot and dry summers, has been particularly affected by wildfires, and the situation is deteriorating as climate change worsens and the regional populations grow rapidly. To assess the health impacts due to short-term exposure to air pollution caused by the 2021 summer wildfires in eastern and central Mediterranean Basin, we demonstrate a multi-pollutant approach based on the Weather Research and Forecasting online-coupled Chemistry (WRF-Chem) model. The WRF-Chem model was used to simulate concentrations of major air pollutants such as fine particulate matter (PM2.5), SO2, NO2, and O3, in a fire and no-fire scenario. Elevated short-term exposure of the population to air pollutants were associated with excess all-cause mortality using relative risks (RRs) for individual pollutants based on previously published meta-analyses.

Our estimates indicate that the additional short-term exposure to O3, which is predicted to increase due to the wildfires, resulted in the highest number of excess deaths of 608 (95% CI: 456-771) over the entire region of investigation during the wildfire season between mid-July to early October 2021. This is followed by 270 (95% CI: 177- 370) excess deaths due to elevated PM2.5 exposure, rendering the health effect of increased O3 from wildfires larger than the effect of increased PM2.5. This is shown to be largely reasoned by the spatially more widespread impact of wildfires on O3. In contrast, the excess mortality caused by NO2 and SO2 emitted from wildfires is estimated low. This may be ascribed to the different sources of air pollutants, with NO2 a marker of traffic, while SO2 originating primarily from emissions from fossil fuel combustion, e.g., from power plants. Our study concludes with a discussion on uncertainties associated with the multi-pollutant health impact assessment and suggests a critical scrutiny of estimates based thereupon.

How to cite: Zhou, B. and Knote, C.: Multi-pollutant assessment of health impacts of 2021 summer wildfires in eastern and central Mediterranean Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7258, https://doi.org/10.5194/egusphere-egu22-7258, 2022.

EGU22-7318 | Presentations | BG1.2

Evaluating the effects of fire severity and post-fire management decisions on the carbon balance of a Swedish forest 

Julia Kelly, Stefan H. Doerr, Johan Ekroos, Theresa S. Ibáñez, Cristina Santín, Margarida Soares, and Natascha Kljun

Boreal forest fires are increasing in frequency and intensity due to climate change. Yet there is little knowledge on the impacts of fire severity and post-fire management decisions on the regeneration and carbon balance of production forests in Eurasia. To investigate these issues, we established 6 sites in a Swedish Pinus sylvestris forest that burned in 2018. Specifically, we evaluated the effects of (i) fire severity (low severity ground fire vs high severity stand-replacing canopy fire), (ii) post-fire wood management (salvage-logged vs unlogged) and (iii) post-fire vegetation management (natural regeneration, seeding or planting nursery seedlings of P. sylvestris). At each site, we measured soil respiration (CO2 release to the atmosphere) and methane fluxes (soil CH4 uptake) using the manual chamber approach, soil microclimate and vegetation cover for the first 3 years after the fire (2019-2021). Two of the sites also have eddy covariance flux measurements, which provided an insight into the ecosystem-scale carbon balance.

 

Fire severity had a strong impact on forest soils, with high fire severity sites having lower soil respiration, warmer soils and less vegetation regrowth compared to a low fire severity site. Surprisingly, soil respiration was similar at a low fire severity site and unburnt site, despite the almost complete loss of the soil organic layer during the ground fire. There were no clear effects of fire or post-fire management on the soil methane fluxes. Salvage-logging of a high fire severity site had no additional effects on soil respiration compared to leaving the dead trees standing. Salvage-logging of a low fire severity site led to a decline in soil respiration, but turned the ecosystem into a net source of CO2 due to the removal of the living trees. In terms of P. sylvestris regeneration, our results showed that the seedling density following natural regeneration was similar to or higher than the seedling density in sites which had been manually seeded or replanted with nursery seedlings.

 

Our results suggest that post-fire management interventions may not facilitate faster vegetation regrowth and the recovery of carbon uptake by forests compared to natural regeneration in the immediate post-fire years. Furthermore, despite the start of new vegetation growth and declines in soil CO2 release, the high fire severity and/or salvage-logged sites remain net CO2 sources 3 years after the fire, which must be considered in estimations of the net effect of fires on Sweden’s forest carbon balance.

How to cite: Kelly, J., Doerr, S. H., Ekroos, J., Ibáñez, T. S., Santín, C., Soares, M., and Kljun, N.: Evaluating the effects of fire severity and post-fire management decisions on the carbon balance of a Swedish forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7318, https://doi.org/10.5194/egusphere-egu22-7318, 2022.

EGU22-7457 | Presentations | BG1.2

Evaluation of simulations of the Last Glacial Maximum with fire-enabled vegetation models from the FireMIP intercomparison project 

Paul Lincoln, Sandy P. Harrison, Matthew Forrest, Jed Kaplan, and Chao Yue

Fire-enabled vegetation models are an important component of earth system modelling. Understanding the sensitivity of vegetation and wildfire to climate change benefits from out-of-sample experiments, of which the Last Glacial Maximum (LGM; 21 ka BP) is a preferred test. Here, we compared wildfire simulations for the LGM made with four fire-enabled vegetation models using a standardized protocol and driven by a climate-model simulation of the response to known LGM changes in ice-sheet extent, atmospheric composition and insolation. We compare the resulting model output with inferred changes in fire based on charcoal records from the Reading Palaeofire Database (RPD).

All four models show a global decrease in fire at the LGM compared to the present day, consistent with the charcoal records which also record less fire. The simulated change in fire is driven principally by changes in vegetation cover at the LGM, particularly the shift from forest to more open vegetation. The simulated reduction in forest cover is consistent with pollen-based reconstructions of LGM vegetation. Despite this general agreement among models, there are differences between the simulated fire anomalies at a regional scale. The largest differences between the models occur in equatorial Africa, South America and East Asia where the amplitude and spatial extent of regions of increased fire (driven principally by the replacement of tropical trees by grassland); in some regions even the direction of change is not consistent. Comparison of the simulated changes with charcoal records from these regions identifies which model(s) perform best, but also make it clear that there is no one model that simulates observed patterns of change in fire across all of the regions.

How to cite: Lincoln, P., Harrison, S. P., Forrest, M., Kaplan, J., and Yue, C.: Evaluation of simulations of the Last Glacial Maximum with fire-enabled vegetation models from the FireMIP intercomparison project, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7457, https://doi.org/10.5194/egusphere-egu22-7457, 2022.

EGU22-8312 | Presentations | BG1.2

Pyrogenic carbon in temperate forests - long-lasting impact of historical charcoal production on soils and ecosystems 

Alexander Bonhage, Thomas Raab, Anna Schneider, Alexandra Raab, Shaghayegh Ramezany, and William Ouimet

Pre- and early industrial charcoal production has left a striking legacy effect on today’s soil landscapes in many forests of Central Europe and the North Eastern USA. Charcoaling in upright standing hearths (also called kilns) resulted in distinct circular micro relief structures, easily identifiable today in the field and on high resolution LiDAR-based digital elevation maps. Soils on these sites are characterized by one or multiple layers of decimetre thick charcoal rich substrate, which makes them Spolic Technosols according to the WRB soil classification. The focus of research on these sites increasingly deals with the difference of their soil physical and chemical properties in relation to unaffected forest soils and the potential implications for changes in vegetation and faunal growth. The controlling factor thereby is the soils large content of charcoal in various particle sizes, ranging from fine dust to large chunks. Studies have repeatedly shown the soils significant increase in total organic- and pyrogenic carbon content. The increase in total carbon stocks is thereby not only caused by pyrogenic carbon, but also by an apparently increased accumulation of non-pyrogenic organic matter. Here we present the latest findings regarding the carbon contents of centennially old charcoal rich technogenic substrates, sampled as part of multiple research projects in Brandenburg, Germany and the Litchfield hills in North-western Connecticut, USA. A focus will be the determination of highly aromatic carbon by the molecular marker Benzene-polycarboxylic acid (BPCA) and its prediction by FTIR-MIR chemometric methods. We discuss the results on forest soil carbon stocks on a site specific to a landscape and regional scale. Furthermore, the potential to use these sites to study the long term effects of charcoal admixture to soils by wildfires or biochar application will be discussed.  

How to cite: Bonhage, A., Raab, T., Schneider, A., Raab, A., Ramezany, S., and Ouimet, W.: Pyrogenic carbon in temperate forests - long-lasting impact of historical charcoal production on soils and ecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8312, https://doi.org/10.5194/egusphere-egu22-8312, 2022.

EGU22-8737 | Presentations | BG1.2

Fire variability in the southeastern France over the past 8500 years 

Marion Genet, Anne-Laure Daniau, Maria-Angela Bassetti, Bassem Jalali, Marie-Alexandrine Sicre, Julien Azuara, and Serge Berné

The Mediterranean region is strongly impacted by fires at present day. Projected warming scenarios suggest increase fire risk in the Mediterranean region (Pechony et Shindell, 2010). However, models based on modern-day statistical relationships do not consider interactions between climate, vegetation, and fire. In addition, process-based models must be tested not only against modern observations but also against climate observations different from today to cover the range of climate variability projected for the next centuries. Here, we present a new biomass burning record for the last 8,500 years in southeastern France with a mean temporal resolution of 45 years based on a marine sedimentary microcharcoal from the Gulf of Lion, located in the Rhone River prodelta. Periodicities of 500 and 1,100 years emerge from this record. Most of the peaks coincide with cold and dry periods of several century duration reflecting enhanced burning of open evergreen sclerophyllous Mediterranean forests. Among the 15 peaks of biomass burning, 7 are associated with negative North Atlantic Oscillation (NAO) phase, 8 with cold events, and 13 with low solar activity. We suggest that cold and wet conditions during negative NAO led to the accumulation of biomass while dry and cold winds during negative East Atlantic (EA) phase favored fuel flammability resulting in peaks in biomass burning. Today, large fires in southeastern France occur during negative NAO or during the Atlantic Ridge weather regime, the latter being similar to the EA (Ruffault et al. 2017). The frequency of heat-induced fire-weather favoring the largest wildfires observed in recent years in the Mediterranean region is projected to increase under global warming (Ruffault et al., 2020). Our study suggests also that the French Mediterranean region might be affected by large wind-driven fires developing in the event of negative NAO and EA modes.

 

References

Ruffault et al., 2017 Daily synoptic conditions associated with large fire occurrence in Mediterranean France: evidence for a wind-driven fire regime. https://doi.org/10.1007/s10584-012-0559-5

Ruffault et al., 2020. Increased likelihood of heat-induced large wildfires in the Mediterranean Basin. https://doi.org/10.1101/2020.01.09.896878

Pechony et Shindell, 2010. Driving forces of global wildfires over the past millennium and the forthcoming century. https://doi.org/10.1073/pnas.1003669107

How to cite: Genet, M., Daniau, A.-L., Bassetti, M.-A., Jalali, B., Sicre, M.-A., Azuara, J., and Berné, S.: Fire variability in the southeastern France over the past 8500 years, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8737, https://doi.org/10.5194/egusphere-egu22-8737, 2022.

EGU22-8767 | Presentations | BG1.2

The Impacts of the 2017 Catastrophic Fire Season in Portugal on Vegetation Productivity 

Tiago Ermitão, Célia Gouveia, and Ana Russo

Wildfires have become a serious threat to ecosystems and human society over the last years of the 21st century, with many hectares being destroyed every year globally. The lengthening of the fire seasons and the increase of wildfires risk, which have been promoted by climate change, input many losses on society, economy and mostly in diverse ecosystems. In Portugal, the 2017 catastrophic fire season burned more than 450,000 hectares and caused the death of more than 100 people. In this context, relying on remotely sense products from MODIS collections, our study proposes an analysis of the effect of summer heat and water availability deficit in vegetation productivity decline that led to large fires propagation, especially in June and October of 2017. With the aim to evaluate the magnitude of the impact that compound or cascading extreme events had on the vegetation productivity decline, considering the 2001-2019 historical values, we defined three different classes of pixels that should reflect the conditions before the fire: affected by hot, by dry or by hot/dry conditions. Moreover, we assess the influence of favourable winter/spring meteorological conditions on enhancing vegetation productivity that promote high fuel accumulations susceptible to burn some months later. Our results reinforce the water and energy dependency of the vegetation of the region during the growing season and highlight that the combination of higher temperatures and water availability in spring can trigger summer wildfires propagation, flammability and intensity due to the accumulation of biomass. Considering that the example of 2017 can be more recurrent under the context of climate change, this study also highlights the need to improve the awareness strategies in fire prone regions like Portugal, especially on biomass accumulation control during growing season.

This study was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017) and IMPECAF (PTDC/CTA-CLI/28902/2017).

How to cite: Ermitão, T., Gouveia, C., and Russo, A.: The Impacts of the 2017 Catastrophic Fire Season in Portugal on Vegetation Productivity, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8767, https://doi.org/10.5194/egusphere-egu22-8767, 2022.

Fire danger rating systems (FDRS) are widely used for many purposes from planning for daily deployment of fire suppression resources to the evaluation of fire management strategies. FDRS can also be incorporated in different types of models to assess the short and long-term effects of specific fire regimes and fire management policies.

The Canadian Forest Fire Weather Index System (CFFWIS) is one of the most known FDRS’s, being extensively used for a fire early warning in several regions around the world, namely in Europe. The CFFWIS includes a set of 6 indices, based on meteorological data, which is used to predict fire weather danger and fire behavior over regions under study. To obtain a reliable assessment of the fire danger based on the CFFWIS it is crucial to determine the threshold values for each class of the CFFWIS sub-indices over different regions. One of the simplest methods to define the classes is to use percentiles based on historical data, but this method lacks information regarding wildfire history and its relation to CFFWIS sub-indices.

The proposed method is based on Fire Radiative Energy (FRE) released by fires, computed from Fire Radiative Power (FRP) product, that is generated, and disseminated in near real-time by EUMETSAT Land Surface Analysis Satellite Applications Facility. Since FRP estimates the radiative power emitted by a fire, it can be linked to fuel burned amounts and used as a proxy of fire intensity. By integrating FRP measures over a fire’s lifetime, an estimate of the total FRE released can be obtained for each event. In this work, daily FRE was derived for the 2010-2021 period, over the Mediterranean region countries. Thresholds values of each defined danger class for the FWI, FFMC, and ISI indices were obtained considering the FRE percentiles computed for different regions of the Mediterranean basin and discussed based on the different fire regimes for the region. A trend analysis of the CFFWIS sub-indices was performed to assess the fire danger behavior and the extreme fire weather over the different Mediterranean regions.

The regions where the extreme fire weather conditions have become more prevalent were identified considering the spatial correlations, and applying field significance testing allows the identification of the regions with significant trends. Since fire regimes in Southern Mediterranean countries have been changing over the last two decades, mostly due to climate-driven factors changes and to the load and structure of fuels, the observed trend towards warmer and drier conditions are expected to continue in the next years, possibly leading to an increased risk of large fires. In this context, the knowledge of fire danger trends and variability is a key factor for fire managing activities, planning and preparedness, and resources allocation.

Acknowledgments:

This study was performed within the framework of the LSA-SAF, co-funded by EUMETSAT and was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017) and by the 2021 FirEUrisk project funded by European Union’s Horizon 2020 research and innovation programme under the Grant Agreement no. 101003890).

How to cite: Durao, R., Silva, M., Alonso, C., and Gouveia, C.: Calibration of the Fire Danger Classes and Trend analysis over the Mediterranean basin, based on the Canadian Forest Fire Weather Index System and the Fire Released Energy from SEVIRI/MSG., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9651, https://doi.org/10.5194/egusphere-egu22-9651, 2022.

EGU22-10035 | Presentations | BG1.2

Live fuel moisture content approach using satellite data for Portugal mainland 

Catarina Alonso, Rita Durão, and Célia Gouveia

The fuel moisture content (FMC) is an important property to assess fire danger, to control fuel ignition and fire propagation. The wetting and drying rates of the fuels are driven by the fuel characteristics and weather conditions, being FMC strongly driven by solar radiation influencing fuel temperature in the highly exposed fuels. Usually, FMC is divided into Dead Fuel Moisture Content (DFMC) and Life Fuel Moisture Content (LFMC). LFMC is not easily estimated due to plants’ adaptation to drought and capacity of extracting water from soils that significantly vary among different vegetation species. Extreme climate events (such as droughts and heatwaves) are important factors addressed to fire danger assessment and related activities, due to their significant impacts on fuel conditions and in the vegetation status. High-impact mega-fires have been reported over areas where biomass and fuel accumulation present significant amounts. Therefore, the estimation LFMC is a useful approach to improve fire danger assessment, bringing also advantages in the study of the dynamics of biodiversity and biomass understory recovery.

Although LFMC in-situ measurements have limited spatial coverage and temporal sampling, the use of remote sensing data is essential to overcome space-time constraints and to develop methodological approaches to assess space-time LFMC variations over Portugal. Accordingly, to previous studies, LFMC estimation results improve when using a vegetation index together with the minimum temperature. The Leaf Area Index (LAI) is a quantitative measure of the amount of live green leaf material present in the canopy per unit ground surface. Since LAI and LFMC are interdependent variables with similar seasonal and interannual trends, it is possible to estimate LFMC based on LAI data.

The present work aims to obtain LFMC statistical model to pixel by pixel for Portuguese national scale, using LAI and Land Surface Temperature (LST) products, delivered by the EUMETSAT Land Surface Analysis Satellite Applications Facility (LSA SAF) and LFMC in-situ data for Atlantic Scrub that are routinely collected over 10 monitoring sites by AGIF (Agência para a Gestão Integrada de Fogos Rurais, IP).

Results revealed very good correlation values between LFMC in-situ data and LFMC estimated, ranging between 0.68 and 0.92, decreasing to values ranging from 0.30 and 0.90, highlighting the robustness of the model in the majority of the locations.  These results vary spatially, being higher over the most sampled locations, as expected; and have the drawback of being site-specific. The influence of LAI is higher than the minimum of LST however being less important LST in the northeast of Portugal.  Further work will focus on the assessment of the remote sensing-based LFMC estimations uncertainty and the linking of LFMC to fire danger and behavior.

 

Acknowledgments: This study was performed within the framework of the LSA-SAF, co-funded by EUMETSAT and was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017) and by the 2021 FirEUrisk project funded by European Union’s Horizon 2020 research and innovation programme under the Grant Agreement no. 101003890).

How to cite: Alonso, C., Durão, R., and Gouveia, C.: Live fuel moisture content approach using satellite data for Portugal mainland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10035, https://doi.org/10.5194/egusphere-egu22-10035, 2022.

EGU22-10391 | Presentations | BG1.2

Impacts of Fires on Convective Cloud Features in Southeast Asia: Variability with ENSO 

Azusa Takeishi and Chien Wang

Located right in the middle of the tropical warm pool, convective activities over Southeast Asia are subject to interannual variability in sea surface temperature due primarily to varying phases of the El Niño-Southern Oscillation (ENSO). Observations often show a reduction in the amount of rainfall during El Niño and its increase during La Niña over Southeast Asia. Because of this interannual variability in rainfall and humidity, emissions of aerosol particles and their abundance in the atmosphere, often manifested in aerosol optical depths, are also subject to interannual variability; they increase during El Niño and are reduced during La Niña on average. Our previous study has shown an impact of biomass-burning aerosols on convective clouds, which enhanced rainfall and generally invigorated convection. Here we present the comparison of this aerosol effect among different years with different ENSO phases. We utilized month-long cloud-resolving simulations by the WRF-CHEM model that are capable of including both aerosol direct and indirect effects. The extensive simulation domain size and time period enabled the inclusion of a wide range of contributors to cloud development over the area, from aerosol activation to ENSO-affected meteorology. We show whether the invigoration effect that we found from the year of strong El Niño in 2015 still holds in years of weaker El Niño or even during La Niña.

How to cite: Takeishi, A. and Wang, C.: Impacts of Fires on Convective Cloud Features in Southeast Asia: Variability with ENSO, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10391, https://doi.org/10.5194/egusphere-egu22-10391, 2022.

EGU22-10524 | Presentations | BG1.2 | Highlight

Observing the climate impact of large wildfires on stratospheric temperature 

Matthias Stocker, Florian Ladstädter, and Andrea K. Steiner

In the future, large wildfires are expected to become more frequent and intense. Not only do they pose a serious threat to people and ecosystems, but they also affect the Earth's atmosphere. Aerosols from large wildfires can even reach the stratosphere where they can linger for months to years. However, little is known about their impact on climate. In particular, the potential of large wildfires to cause temperature changes in the stratosphere has hardly been studied.

In our study, we analyze two extreme wildfire events, those in 2017 in North America and those in 2019/20 in Australia, using new satellite observational data. We find strong effects of the fires on the atmospheric temperature structure and short-term climate in the stratosphere. The results show significant warming of the lower stratosphere by up to 10 K within the aerosol clouds emitted by the wildfires immediately after their formation. The climate signal in the lower stratosphere persists for several months, reaching 1 K for the 2017 North American wildfires and a remarkable 3.5 K for the 2019/20 Australian wildfires. This is stronger than any signal from volcanic eruptions in the past two decades. Such extreme events potentially influence the atmospheric composition and stratospheric temperature trends, underscoring their importance for future climate.

Improved knowledge of the temperature signals from extreme wildfires is particularly important for trend analysis. Our ongoing research on this topic aims to further improve the separation of natural variability from anthropogenic influences in climate trend detection, especially in the stratosphere.

How to cite: Stocker, M., Ladstädter, F., and Steiner, A. K.: Observing the climate impact of large wildfires on stratospheric temperature, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10524, https://doi.org/10.5194/egusphere-egu22-10524, 2022.

EGU22-10772 | Presentations | BG1.2

The impact of heat waves in forest fires over the Amazon rainforest 

Luiza Narcizo, Filippe LM Santos, Leonardo F. Peres, Ricardo Trigo, and Renata Libonati

Wildfires have become an imminent threat to ecosystems, consequently leading to economic loss and generating negative impacts on population health. Considering IPCC’s projection of a significant increase in the frequency of these events, it is important to understand which conditions lead to a fire intensification, as recently happened in California, Australia, and Brazilian Pantanal. Some of the greatest wildfires registered in North America and in Europe occurred in concomitance to intense heat waves and drought events. The lack of a comprehensive understanding of the physical mechanisms associated with extreme wildfire events in the Amazon rainforest, underlines the current inability to properly prevent them. Therefore, this study aimed to identify the role of extreme temperature events, such as heat waves (HW), in forest fires behaviour in the Brazilian Amazon during extreme drought years. The relationship between wildfires and HWs was hereby analysed during both dry and wet years in the Amazon Forest, in order to understand the association between different time and spatial scale events in forest fires magnitude. Accordingly, CPC/NOAA reanalysis data of daily maximum temperature between 1979 and 2019 were used as input to determine HW events in a multi-method global heatwave and warm-spell data record and analysis toolbox1. A standard HW definition was applied, where an event corresponds to at least three consecutive days in which the maximum temperature exceeds the 90th percentile for that day. Wildfire magnitude analyses were calculated through active fire (AF) and fire radiative power (FRP) data from MODIS C6 sensor, obtained at FIRMS/NASA for the comprehended period between 2003 and 2019. Spatial intensity of HW was classified and then confronted with precipitation anomaly in both normal and dry years. Also, statistical comparison of fire magnitude (i.e., AF and FRP) in HW and non heat wave (NHW) days was analysed to measure extreme temperature events impacts in wildfire. Results showed a significant increasing trend in HW occurrences in recent decades, with peaks in known drier years. An increase of AF counting and fire intensity was noticed during HW events. This latter effect appears even when the HW occurs during extremely dry seasons, such as happened at the Amazon Forest in 2005, 2010 and 2015. Extreme values of AF and FRP were a quarter higher in 2005, doubled in 2010 and tripled in 2015 at HW days when compared to NHW days.

 

References 

[1] Raei, E., Nikoo, M., AghaKouchak, A. et al. GHWR, a multi-method global heatwave and warm-spell record and toolbox. Sci Data 5, 180206 (2018).

Acknowledgements

This study was supported by FAPERJ project number E26/202.714/2019. L. N. was supported by CNPq PIBIC  number 160099/2021-8.

How to cite: Narcizo, L., Santos, F. L., Peres, L. F., Trigo, R., and Libonati, R.: The impact of heat waves in forest fires over the Amazon rainforest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10772, https://doi.org/10.5194/egusphere-egu22-10772, 2022.

EGU22-11099 | Presentations | BG1.2

Reconstructing fire regimes using micro-charcoal in modern marine sediments off Africa 

Aritina Haliuc, Anne-Laure Daniau, Florent Mouillot, Wentao Chen, Valérie David, Vincent Hanquiez, Bernard Dennielou, Enno Schefuß, Germain Bayon, and Xavier Crosta

Fire is a pervasive component of almost every terrestrial ecosystem, but the African continent is rather unique, holding the most vulnerable ecosystems to fire which account for most of the global burned area and for more than half of fire-carbon emissions. Fire has a significant role in ecosystem functioning though our understanding of this complex process is still limited which hinders our ability to model and predict fire.

Paleofire records go beyond the short instrumental records of the last decades and can provide long-term information about fire, but only at a descriptive scale and with difficulties in relating it to the fire regime. To address these limitations, we attempt to develop a quantitative calibration model based on the examination of micro-charcoal from 137 surface sediment samples collected offshore the African continent in conjunction with a set of fire parameters (burnt perimeter, fire radiative power, fire spread) derived from satellite data, environmental information (hydrographic basins, vegetation cover, climatic parameters) and a wind dispersal particle model. Our results show that changes in charcoal concentration and morphometry are linked with fire regime and the type of burnt vegetation on the adjacent continent. In (sub)tropical settings, elongated micro-charcoal particles in high concentrations relate to rare but intense fires spreading in graminoid-mixed ecosystems whereas squared particles in low concentrations are typical for frequent but low intensity fires, characteristic for tree-dominated ecosystems.

This work provides the first calibration model of micro-charcoal in marine sediments which can be applied to long marine charcoal records to help reconstruct past fire regimes. This investigation addresses a key issue in unlocking specific methodological and theoretical problems related to fire research; it provides a better understanding of the local to regional processes that govern the fire signal and contextualize current and past environmental changes.

How to cite: Haliuc, A., Daniau, A.-L., Mouillot, F., Chen, W., David, V., Hanquiez, V., Dennielou, B., Schefuß, E., Bayon, G., and Crosta, X.: Reconstructing fire regimes using micro-charcoal in modern marine sediments off Africa, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11099, https://doi.org/10.5194/egusphere-egu22-11099, 2022.

EGU22-11223 | Presentations | BG1.2 | Highlight

Future fire impact on PM2.5 pollution and attributable mortality 

Chaeyeon Park, Kiyoshi Takahashi, Shinichiro Fujimori, Fang Li, Vera Ling Hui Phung, Junya Takakura, Tomoko Hasegawa, and Ahihiko Ito

Fine particulate matter with a diameter of ≤ 2.5  (PM2.5), one of the hazardous air pollutants, contributed 4.5 million to 8.9 million global mortality annually. Among the total PM2.5 related mortality, 5%–21% were attributed to fires. While anthropogenic fire has been declined by reduced land fragmentation and changed land use, climate change has increased fire activities especially in fire seasons. These fires eventually lead to high PM2.5 in many regions, leading to public health concern. However, the impact of future fires on PM2.5 and its health burden according to climate change and socioeconomic scenarios has not been studied globally. We estimated fire related PM2.5 at the end of 21st century under various future scenarios (combination of Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs)) and its attributable mortality. We used modified CLM and GEOSChem for simulating fire emissions and PM2.5 concentration, respectively. The Global Burden of Disease (GBD) method was used for estimating attributable mortality. We also evaluated how global inequality in fire-PM2.5 mortality by income (economic inequality) would change. We found that future climate change led to higher fire-PM2.5 by increasing drought and biomass carbon density, whereas future increased GDP would offset the increase in fire-PM2.5. The results of fire-PM2.5 mortality varied significantly by SSPs. Population increase under SSP3 would lead to increase in mortality and economic inequality. The total fire-PM2.5 mortality decreased under SSP1–4, but the economic inequality increased under SSP4. If the world follows SSP1-RCP2.6 scenario, fire-PM2.5 mortality would reduce about 40% and improve economic equality.

This research was supported by the Environment Research and Technology Development Fund (JPMEERF20202002) of the Environmental Restoration and Conservation Agency of Japan.

How to cite: Park, C., Takahashi, K., Fujimori, S., Li, F., Phung, V. L. H., Takakura, J., Hasegawa, T., and Ito, A.: Future fire impact on PM2.5 pollution and attributable mortality, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11223, https://doi.org/10.5194/egusphere-egu22-11223, 2022.

EGU22-11616 | Presentations | BG1.2

Fire weather risk analysis over Portugal in the last decades and their impacts over the atmosphere  - The Monchique study case 

Filippe LM Santos, Flavio T Couto, Vanda Salgueiro, Miguel Potes, Maria João Costa, Daniele Bortoli, and Rui Salgado

More intense fire seasons have been favoured by climate changes worldwide, like Russia, Brazil, the USA, Canada and Portugal. Portugal experienced numerous severe fire seasons with catastrophic wildfires that caused enormous impacts in the last years. This study aimed to investigate the fire risk evolution in Portugal over the last 40 years and the extreme wildfire emission impacts derived from remote sensing data. First, the Fire Weather Index (FWI) from 1979 to 2020, at 0.25º spatial resolution, provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5 reanalysis version 4 based on meteorological variables, was used. Then, FWI monthly mean values and trends were analysed for four districts of Southern Portugal (Beja, Evora, Faro and Portalegre). The results indicate that the Faro district presented extreme fire risk values, which peaked on August 2, 2018, one day before the Monchique (a mountain in Faro) wildfire began and lasted between August 3 and 10. The Monchique wildfire was the most destructive in Portugal during 2018, with almost 27.000 ha burned. Second, based on the previous results, atmospheric products derived from the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor satellite, the first Copernicus mission dedicated to atmospheric composition monitoring, were collected. These datasets were obtained from Google Earth Engine (GEE), the online platform that combines multiple imageries and datasets with cloud processing to perform analyses. The Carbon monoxide (CO) and Nitrogen dioxide (NO2) concentrations, as well as Absorbing Aerosol Index (AAI) products were analysed during the fire event. The concentrations released by the wildfire reached values 3 and 5 times higher than usual for CO and NO2, respectively. Therefore, the work confirms that extreme wildfire events can release huge pollutant concentrations into the atmosphere. Also, the Sentinel-5 products are useful to evaluate the fire emission evolution in extreme wildfires events and may constitute additional valuable information to combine with ground-based information to map air quality related to wildfire occurrences.

This research was funded by the European Union through the European Regional Development Fund in the framework of the Interreg V A Spain - Portugal program (POCTEP) through the CILIFO project (Ref.: 0753-CILIFO-5-E), FIREPOCTEP project (0756-FIREPOCTEP-6-E), and also by national funds through FCT - Foundation for Science and Technology, I.P. under the PyroC.pt project (Refs. PCIF/MPG/0175/2019), ICT project (Refs. UIDB/04683/2020 and UIDP/04683/2020), and TOMAQAPA (PTDC/CTAMET/ 29678/2017).

How to cite: Santos, F. L., Couto, F. T., Salgueiro, V., Potes, M., Costa, M. J., Bortoli, D., and Salgado, R.: Fire weather risk analysis over Portugal in the last decades and their impacts over the atmosphere  - The Monchique study case, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11616, https://doi.org/10.5194/egusphere-egu22-11616, 2022.

EGU22-11760 | Presentations | BG1.2

Climatic drivers explain the interannual variability of the global burned area 

Andrina Gincheva, Sonia Jerez, Juli G. Pausas, Joaquín Bedía, Sergio M Vicente-Serrano, Antonello Provenzale, Emilio Chuvieco, John Abatzoglou, and Marco Turco

Understanding the response of fire to climate variations is essential to adapt fire management systems under climate change. Although several studies have analysed the drivers of the average spatial variability of fire, the assessment of the temporal variability of fire in response to climate across the globe has proved challenging, largely due to complexity of the processes involved, the limitation of observation data and the compound effect of the multiple drivers, which usually cause non-linear effects.

In this study, we analyse how much of the interannual variability in observed burned area (BA) is linked with temporal variations in climate at global scale. To solve this question, we use the burned area data of the FireCCI51. product for the period 2001-2019 at the global scale, and different climate metrics that are directly related to drought occurrence, including indices like the Fire Weather Index (FWI), the Standardized Precipitation Evapotranspiration Index (SPEI), and the Standardized Precipitation Index (SPI). Our study shows complex spatial patterns in the relationship between climate drivers and BA variability, highlighting where variations in FWI, SPI, SPEI or their interaction explain BA variability. While in some areas the interannual variability of burned area does not show a statistically significant influence of climate variability, over a substantial portion of the global burnable area (~60%) the BA variability can be explained by interannual variability of climate drivers. Globally, climate variability accounts for roughly two thirds (64%) of the observed temporal BA variability.

How to cite: Gincheva, A., Jerez, S., Pausas, J. G., Bedía, J., Vicente-Serrano, S. M., Provenzale, A., Chuvieco, E., Abatzoglou, J., and Turco, M.: Climatic drivers explain the interannual variability of the global burned area, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11760, https://doi.org/10.5194/egusphere-egu22-11760, 2022.

EGU22-11856 | Presentations | BG1.2

Analysis of the environmental conditions favoring the development of deep pyroconvection in Southern Europe 

Martín Senande-Rivera, Damián Insua-Costa, and Gonzalo Míguez-Macho

Deep pyroconvection can strongly modify surface weather conditions, especially when a firestorm develops, completely altering fire spread and making it more difficult to predict and control. However, the limited number of observations constrains our understanding of this type of events, so the environmental controls on deep pyroconvection are not entirely clear and, in particular, there are still uncertainties about the atmospheric conditions conducive to the development of this phenomenon. We conduct idealised numerical simulations with the fire-atmosphere coupled model WRF-Fire initialised with selected real-case atmospheric profiles of wind, temperature and moisture, obtained from the ERA5 database, corresponding to the 100 days of highest fire risk per year during the 2010-2019 period at six different European fire-prone locations. For each of these atmospheric profiles, we perform a suite of paired experiments of an ideal fire spreading through five different fuel categories. Each pair consists of a control run with interaction between fire and atmosphere and a simulation in which the sensible and latent heat fluxes from the fire are turned off (uncoupled simulation). This experiment allows us to make a significant statistical study of pyroconvection events and thus analyse which environmental factors favour its development. We found that a high fuel load, a large vertical temperature lapse rate between the 850 hPa and the 500 hPa levels and a high moisture content in the lower layers of the atmosphere are some of the main factors in the development of firestorms. 

How to cite: Senande-Rivera, M., Insua-Costa, D., and Míguez-Macho, G.: Analysis of the environmental conditions favoring the development of deep pyroconvection in Southern Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11856, https://doi.org/10.5194/egusphere-egu22-11856, 2022.

EGU22-12015 | Presentations | BG1.2 | Highlight

Evidence for a stronger global impact of fire on atmospheric composition 

James Randerson, Yang Chen, Li Xu, Joanne Hall, Louis Giglio, Dave van Wees, Sander Veraverbeke, Guido van der Werf, Douglas Morton, Elizabeth Wiggins, Niels Andela, and Stijn Hantson

Toward the development of the 5th generation of the Global Fire Emission Database (GFED5), we provide evidence for a significantly higher level of contemporary global fire emissions than what has been reported in previous inventories, as a result of advances in our understanding of burned area, fuel consumption, and emission factors. Increases in the availability of high-resolution burned area datasets from Sentinel and Landsat now allow for more effective estimation of fire scars associated with small and discontinuous fires in many biomes. By combining these regional-scale datasets with burned area and active fire observations from MODIS, we estimate that global burned area exceeded 700 Mha per year during 2001-2020. This estimate is more than 40% higher than previous estimates from GFED4 with small fires (GFED4s), mostly as a consequence of increases in savanna and grassland burning across Africa, South America, and Southeast Asia. At the same time, more extensive field observations in boreal forest ecosystems provide evidence for higher levels of fuel consumption than has been integrated into previous regional and global inventories. New emission factor observations from tropical peatlands and boreal forests provide evidence for a stronger smoldering phase of emissions, elevating emissions of carbon monoxide and organic carbon aerosol. Together, these advances suggest the impact of contemporary wildfires may have been underestimated in past work; we conclude by exploring the compatibility of this inventory with atmospheric aerosol and trace gas observations using a global atmospheric chemistry model.

How to cite: Randerson, J., Chen, Y., Xu, L., Hall, J., Giglio, L., van Wees, D., Veraverbeke, S., van der Werf, G., Morton, D., Wiggins, E., Andela, N., and Hantson, S.: Evidence for a stronger global impact of fire on atmospheric composition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12015, https://doi.org/10.5194/egusphere-egu22-12015, 2022.

EGU22-12049 | Presentations | BG1.2

A novel parameterization for wildfire plumes in LPJ-GUESS 

Lars Nieradzik and Tommi Bergman

Wildfires are one of the major disturbances in the global terrestrial ecosystems and can be the key driver for both vegetation composition and structure, affecting the carbon stocks above and below the surface. With a total of about 2 Pg(C)/year emitted into the atmosphere wildfires also play an important role in the global carbon cycle. Beyond this, emissions from wildfires influence regional air quality, can have a fertilizing effect on the surroundings, or alter the albedo of both the burned area itself but also of distant areas when e.g. black carbon is deposited on ice sheets or snow. Large fires creating pyrocumulonimbus-clouds even elevate trace gases into the lower stratosphere. 

The chemical and physical evolution of the compounds emitted by wildfires can be simulated by modern CTMs (Chemistry Transport Models) and ESMs (Earth-System Models). A key uncertainty in these models, though, are the fires and the resulting emissions themselves, both in space and amount. Many plume rise models use satellite retrievals for fire intensity as e.g. FRP (Fire Radiative Power) and top height for hindcast or historical simulations, where the accuracy of FRP is anti-correlated with the total emissions because the plume itself blocks the frequencies needed to measure a fire’s intensity, i.e. the larger in scale a fire is the less accurate its intensity, and therefore, it is difficult to generate a vertical emission profile. Furthermore, for future projections, these parameters need to be computed from available information within the operating model.

The approach presented here was developed in the framework of the project CoBACCA and is an attempt to invert this problem. Therefore, we use the 2nd generation dynamic global vegetation model LPJ-GUESS and its incorporated wildfire-model SIMFIRE-BLAZE. Vegetation in LPJ-GUESS is represented by 12 different Plant Functional Types (PFTs; 10 tree and 2 grass PFTs) plus litter and soil pools. In combination with meteorological parameters, the combustion model BLAZE then computes their mortality, their combustion completeness, the intensity of the fire, and finally a vertical emission profile. 

Another critical issue for the use of vertical emissions is that one of the uncertainties in atmospheric models is the height of the planetary boundary layer (PBL) which more or less determines whether emitted air-parcels remain in the mixing layer or reach the free troposphere or even the lower stratosphere. We, therefore, decided to compute the vertical emission profile relative to a model-generated PBL.

These emission profiles will be used online in the upcoming version 4 of the ESM EC-Earth but they can also be used offline as emission inventories for other models. This is a step towards a fully coupled plume-rise sub-grid model to be developed within EC-Earth4.

How to cite: Nieradzik, L. and Bergman, T.: A novel parameterization for wildfire plumes in LPJ-GUESS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12049, https://doi.org/10.5194/egusphere-egu22-12049, 2022.

EGU22-12134 | Presentations | BG1.2

Impacts of summer 2021 wildfire events in Southwestern Turkey on air quality with multi-pollutant satellite retrievals 

Merve Eke, Fulya Cingiroglu, and Burcak Kaynak

Climate change has several impacts on our Earth. Even though wildfires are natural processes to sustain structure of an ecosystem, there is a significant increase in the global fire cases and their extent in the recent years caused by the climate change. These wildfires have important impacts on air quality, climate and relatedly public health. Copernicus Atmospheric Monitoring Service (CAMS) indicated that Siberia, North America, and the Mediterranean regions are greatly impacted by wildfires and the intensities of these fires are expressed as Fire Radiative Power (FRP). Effect of wildfires can also be observed with gas pollutant satellite retrievals of CO, NO2, and HCHO which is an important volatile organic carbon (VOC).

Turkey was challenged with wildfires that result in the destruction of forests, the death of animals and devastating impacts on local people in 2021. CAMS Global Fire Assimilation System (GFAS) indicated that the worst fire case observed in Turkey compared with other Mediterranean countries. Global Forest Watch fire counts showed that, fire counts reached up to 695 and 385 in summer (between June-August) 2021 for Antalya and Mugla provinces, respectively. However, fire counts did not exceed 165 fires in the summer season for either Antalya or Mugla in the last five years. Moreover, there was a significant increase in fires in the forested lands for Mersin province as well. Fire counts reached up to 171 per day (31st August) in Antalya province and fire smokes were observable from MODIS Corrected Reflectance images in the fire period. In addition, air pollutants caused by these fires were observable with high resolution TROPOMI retrievals.

In this study, multi-pollutant satellite retrievals were used to investigate the wildfires air quality impacts on the Southwestern Turkey. VIIRS S-NPP Fire Radiative Power product and TROPOMI CO, NO2, and HCHO, products were used to analyze impacts of these extreme wildfire cases. Products were processed spatially and temporally for two months (July-August 2021). A specific attention was given on period of 28th July-12th August. A 1×1 km2 gridded domain covering the impacted region was selected to investigate the spatial distribution of these pollutants. 29th and 31st of July were the days where the impacts of wildfires were analyzed specifically. Wind speed and direction were used to understand the relation between meteorological conditions and the pollution distribution caused by the wildfires. Aerosol signals will be also investigated using MODIS aerosol optical depth (AOD) and TROPOMI aerosol index (AI) retrievals.

How to cite: Eke, M., Cingiroglu, F., and Kaynak, B.: Impacts of summer 2021 wildfire events in Southwestern Turkey on air quality with multi-pollutant satellite retrievals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12134, https://doi.org/10.5194/egusphere-egu22-12134, 2022.

EGU22-12301 | Presentations | BG1.2

Spatiotemporal post-fire change analysis using optical and SAR imagery 

Yeji Lee, Junse Oh, Su Young Kim, Yoon Taek Jung, and Sang-Eun Park

Wildfires on permafrost covered with the boreal forest can influence vegetation composition, surface soil moisture, and the active layer. Since wildfires on permafrost occur extensively in unpredictable areas, remote sensing is a useful tool for monitoring burn severity and ecosystem changes. Optical spectral indices such as the differenced normalized burn ratio (dNBR) and normalized difference vegetation index (NDVI) were traditionally used to detect burn severity and vegetation regrowth. However, since optical imagery is significantly affected by cloud cover and weather conditions, there is a limitation in acquiring temporally dense images. Synthetic Aperture Radar (SAR) can obtain images regardless of day/night or weather conditions, so it is possible to densely observe the area of interest spatiotemporally. In addition, SAR images, unlike optical images, can acquire information on the active layer of the permafrost in the winter season. This study aimed to analyze winter season time-series SAR backscattering coefficient change with burn severity in south Northwest Territories, Canada using optical and SAR data. The study area, south Northwest Territories, belongs to the discontinuous permafrost zone and consisted of the taiga. Burn severity and vegetation regrowth were estimated by dNBR and NDVI using optical imagery. To increase the temporal resolution, Landsat-8 OLI and Sentinel-2 MSI were acquired through the cloud-based Google Earth Engine (GEE) in the summer season. C-band dual-polarization Sentinel-1 and X-band single-polarization TerraSAR-X were obtained to understand the multi-frequency backscattering coefficient to fire-induced changes. The changes pattern of the SAR backscattering coefficient varies according to the burn severity, especially in the winter season, not affected by vegetation and soil moisture. It can be seen that the wildfires affected the changes in the scattering mechanism in permafrost on the boreal forests. These results represent that C-band and X-band SAR images have the potential to monitor the changes of the active layer with burn severity.

How to cite: Lee, Y., Oh, J., Kim, S. Y., Jung, Y. T., and Park, S.-E.: Spatiotemporal post-fire change analysis using optical and SAR imagery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12301, https://doi.org/10.5194/egusphere-egu22-12301, 2022.

In this work, a multi-sensors temporal and spatial approach was carried out to monitor the vegetation post-fire recovery rate in a Mediterranean site (in part falling within the Nature2000 network) through the use of the optical Sentinel-2 and SAR C-band Sentinel-1 imagery temporal-series. The study area was observed for one year before and three years after the fire event. Several vegetation indices (VIs) were calculated for both optical (normalized difference vegetation index, NDVI; green NDVI, GNDVI; normalized red-edge vegetation index, NDRE, normal burn index, NBR; normalized difference water index, NDWI) and SAR (radar vegetation index, RVI; dual-polarized SAR vegetation index, DPSVI; radar forest degradation index, RFDI) data from which the temporal spectral profiles were extracted in the function of one of the three vegetation types (natural/semi-natural native forest, eucalyptus plantation and grasslands), of the burn-severity gradient, and of the orbit path of SAR satellite. What emerged is that the recovery spectral dynamics are highly influenced in terms of time and magnitude by both vegetation type and, mainly, burn severity. Optical Sentinel-2 observations showed that native woody and non-woody vegetation presented higher efficiency in restoring the ecological and physiological equilibrium by the observed time, whereas C-band SAR Sentinel-1 information seems to point out that the structural characteristics cannot be recovered in such a short time, although both the data appeared impacted by saturation. Climate variables, in particular monthly rainfall, compared and correlated with the temporal spectral profiles,  demonstrated to be very influential on the SAR signal, especially for a higher degree of burn severity. The spatial distribution of the post-fire recovery rate was estimated by calculating the burn recovery ratio (BRR), optimized using the random forest (RF) machine learning regressor model to account the natural phenological changes which affect unburned vegetation during the time.  The BRR results validated what had been recorded in the temporal profiles. The effectiveness of open-source data, software, and models interoperability for post-risk monitoring purposes of vulnerable habitats was also emphasized in this study.

How to cite: De Luca, G., Silva, J. M. N., and Modica, G.: Temporal and spatial analysis for post-fire vegetation recovery in a Mediterranean site. An approach using optical Sentinel-2 and SAR Sentinel-1 imagery., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12542, https://doi.org/10.5194/egusphere-egu22-12542, 2022.

EGU22-12805 | Presentations | BG1.2

The role of meteorological factors on interannual variability of fire activity in Iberia: an assessment performed over four subregions 

Carlos C. DaCamara, Sílvia A. Nunes, and José M.C. Pereira

The Iberian Peninsula is recurrently affected by devastating wildfires that result from an interplay of human activities, landscape features, and atmospheric conditions. The fact that the Mediterranean basin, and the Iberian Peninsula in particular, is a hotspot of climate change, strongly suggests that particular attention should be devoted to the role played by atmospheric conditions on wildfire activity.

Here we present a statistical model that is able to simulate the probability of occurrence of a fire event that releases a given amount of Fire Radiative Power, provided a specified level of meteorological fire danger as rated by the Fire Weather Index.

The model combines a lognormal distribution central body with a lower and an upper tail, both consisting of Generalized Pareto (GP) distributions, and daily FWI is used as a covariate of the parameters of the lognormal and the two GP distributions.

The Iberian Peninsula is subdivided into four spatially homogeneous pyro-regions, namely the northwest(NW), southwest (SW), north (N) and east (E) regions. Fire data cover the period 2001-2020 and consist of Fire Radiative Power (FRP) as acquired by the MODIS instrument on-board Aqua and Terra Satellites. Fire Weather (FWI) data covering the same period were obtained from the Copernicus Emergency Management Service.

For each region, the statistical model is fitted to the sample of FRP of all recorded events. First a base model (with fixed parameters) is fitted to the decimal logarithm of FRP, and the quality of fit is assessed using an Anderson-Darling test. Then the model is improved using FWI as a covariate, and performances of models without and with covariate are compared by computing the Bayes Factor as well as by applying the Vuong’s closeness test.

For each region, a set of 100 synthetic time series of total annual FRP is set up using the statistical models without and with FWI as a covariate. This is achieved by randomly generating probabilities for each observed event, generating the FRP associated to that probability and then adding up the generated FRP all events for each year. The interannual variability of synthetic time series obtained is then compared with the corresponding interannual variability of the recorded events.

Results obtained for region SW show an increase from 91 to 96% of interannual explained variance of FRP when going from the model without to the model with FWI. Increases from 95 to 96%, 84 to 90% and from 78 to 86% were obtained for regions NW, N and E. It is worth stressing that these are conservative estimates of change since the dependence of number of ignitions on FWI was not taken into account.

 

This work was supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project FIRECAST (PCIF/GRF/0204/2017).

How to cite: DaCamara, C. C., Nunes, S. A., and Pereira, J. M. C.: The role of meteorological factors on interannual variability of fire activity in Iberia: an assessment performed over four subregions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12805, https://doi.org/10.5194/egusphere-egu22-12805, 2022.

EGU22-1945 | Presentations | BG1.3

Predicting the risk of groundwater nitrate contamination using machine learning tools 

Xin Huang, Menggui Jin, Xing Liang, Jingwen Su, and Bin Ma

Nitrate contamination in groundwater is affected by both anthropogenic activities and natural conditions, becoming one of the most prevalent problems worldwide. In this study, several machine learning methods including decision tree (DT), k nearest neighbors (KNN), logistic regression (LR), support vector machine (SVM), and extreme-gradient-boosted trees (Xgboost) were applied to predict the risk of groundwater nitrate contamination (NO3- > 50 mg L-1) in the riverside areas of lower reaches of Yangtze River, east China. The developed model included 13 hydrochemical parameters (K+, Na+, Ca2+, Mg2+, Cl-, SO42-, NH4+, NO2-, Fe, Mn, As, Sr, pH) and well depth as explanatory variables, and a total of 1089 groundwater samples. The results showed the hydrochemical dataset could effectively predict the risk of nitrate contamination, with a minimum accuracy of 82.7% in LR and maximal accuracy of 91.7% in SVM and Xgboost. However, only the Xgboost model under a cutoff probability of 0.3 had the best performance with the highest sensitivity of 80.3% and AUC 0.95, whereas other models had sensitivity lower than 60% with insufficient capability of identifying contaminated groundwater samples. The results showed that the ensemble learning method had a strong, robust prediction capability. In addition, the relative importance of K+, SO42-, and Cl- exceeded 0.65, indicating the dominant influence of domestic or industrial sewage in the study area due to widespread urbanization. Finally, we examined the relationship among nitrate contamination risk, land use type, the intensity of anthropogenic activities, and redox conditions and obtained the risk map of nitrate contamination in the study area. This study successfully proved the validity of predicting the risk of groundwater nitrate contamination using machine learning tools, which favors regional groundwater management and protection.

Keywords: groundwater; nitrate contamination; risk prediction; machine learning

How to cite: Huang, X., Jin, M., Liang, X., Su, J., and Ma, B.: Predicting the risk of groundwater nitrate contamination using machine learning tools, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1945, https://doi.org/10.5194/egusphere-egu22-1945, 2022.

Nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) is a crucial link between carbon and nitrogen cycles in estuarine and coastal ecosystems. However, the factors that affect the heterogeneous variability in n-DAMO microbial abundance and activity across estuarine and intertidal wetlands remain unclear. This study examined the spatiotemporal variations in n-DAMO microbial abundance and associated activity in different estuarine and intertidal habitats via quantitative PCR and 13C stable isotope experiments. The results showed that Candidatus 'Methylomirabilis oxyfera' (M. oxyfera)-like DAMO bacteria and Candidatus 'Methanoperedens nitroreducens' (M. nitroreducens)-like DAMO archaea cooccurred in estuarine and intertidal wetlands, with a relatively higher abundance of the M. oxyfera-like bacterial pmoA gene (4.0×106-7.6×107 copies g-1 dry sediment) than the M. nitroreducens-like archaeal mcrA gene (4.5×105-9.4×107 copies g-1 dry sediment). The abundance of the M. oxyfera-like bacterial pmoA gene was closely associated with sediment pH and ammonium (P<0.05), while no significant relationship was detected between M. nitroreducens-like archaeal mcrA gene abundance and the measured environmental parameters (P>0.05). High n-DAMO microbial activity was observed, which varied between 0.2 and 84.3 nmol 13CO2 g-1 dry sediment day-1 for nitrite-DAMO bacteria and between 0.4 and 32.6 nmol 13CO2 g-1 dry sediment day-1 for nitrate-DAMO archaea. The total n-DAMO potential tended to be higher in the warm season and in the upstream freshwater and low-salinity estuarine habitats and was significantly related to sediment pH, total organic carbon, Fe(II), and Fe(III) contents (P<0.05). In addition to acting as an important methane (CH4) sink, n-DAMO microbes had the potential to consume a substantial amount of reactive N in estuarine and intertidal environments, with estimated nitrogen elimination rates of 0.5-224.7 nmol N g-1 dry sediment day-1. Overall, our investigation reveals the distribution pattern and controlling factors of n-DAMO bioprocesses in estuarine and intertidal marshes and gains a better understanding of the coupling mechanisms between carbon and nitrogen cycles.

How to cite: Chen, F., Zheng, Y., and Hou, L.: Microbial abundance and activity of nitrite/nitrate-dependent anaerobic methane oxidizers in estuarine and intertidal wetlands: Heterogeneity and driving factors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2143, https://doi.org/10.5194/egusphere-egu22-2143, 2022.

EGU22-3066 | Presentations | BG1.3 | Highlight

High off-season nitrous oxide emissions negate potential soil C-gain from cover crops in boreal cereal cropping 

Peter Dörsch, Ievina Sturite, and Sigrid Trier Kjær

Enhancing carbon storage in managed soils through increased use of cover and catch crops in cereal cropping is at the heart of a carbon-negative agriculture. However, increased C storage by additional biomass production has a nitrogen cost, both in form of increased N fertilizer use and by potentially increasing nitrous oxide (N2O) emissions when cover crops decay. Frost-sensitive, N-rich aboveground biomass may be a particular problem during wintertime, as it may fuel off season N2O emissions during freezing-thawing cycles, which have been shown to dominate the annual N2O budget of many temperate and boreal sites. Here we report growing season and winter N2O emissions in a plot experiment in SE Norway, testing a barley production system with seven different catch and cover crops (perennial and Italian ryegrass, oilseed radish, summer and winter vetch, phacelia​ and an herb mixture) against a control without cover crops. Cover crops where either undersown in spring or established after harvesting barley. While ryegrass undersown to barley marginally reduced N2O emissions during the growing season, freeze-thaw cycles in winter resulted in significantly larger N2O emissions in treatments with N-rich cover crops (oilseed reddish, vetch) and Italian ryegrass. N2O budgets will be presented relative to aboveground yield and quality of cover crops and compared to potential souil organic carbon gains. 

How to cite: Dörsch, P., Sturite, I., and Trier Kjær, S.: High off-season nitrous oxide emissions negate potential soil C-gain from cover crops in boreal cereal cropping, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3066, https://doi.org/10.5194/egusphere-egu22-3066, 2022.

Most often, yield variability can be associated with differences in topography, soil properties and other environmental factors across agricultural landscapes. Ensuring high yield levels while simultaneously minimizing the risk of N-losses through inadequate use of fertilizers is especially difficult due to the high spatial variability of N transformations originating from those heterogeneities. Thus, understanding of N transformation in heterogeneous agricultural landscapes is key to an efficient and sustainable crop management.

To assess the impact of soil heterogeneity on N transformation processes, a novel field design was established in Tempelberg, North-East Germany. The experimental area was categorized in high yield and low yield potential zones based on historic yield and soil textural maps with field sizes of half a hectare. To display the small-scale soil heterogeneity within the patches, measurements were done along transects of gradients of yield potential.

We hypothesized that low yield soils with sandy texture, low soil water holding capacity (WHC) and locations at lower elevations within the field are associated with low N2O emissions and high N-leaching. In contrast, we expected high yield potential soils located at higher altitudes with a loamy texture to be characterized by high WHC, high N2O emissions and low N-leaching. Additionally, we postulated that edge effects across the transects may play a role due to patch design. We present results of the monthly N2O emission measurements done in fields cultivated with rape seed (Brassica napus L.), sunflower (Helianthus annuus L.) and maize (Zea mays L.), measured with NFT-NSS closed chambers, over a period of 6 months. 15N balances were calculated in the same fields tilled with sunflower (Helianthus annuus L.) and maize (Zea mays L.), by 15N tracer application and evaluation at three time points over growing season. Combination of N transformation processes and gaseous N fluxes in addition with WHC and topography allows for the identification of factors controlling soil N transformation and N availability in agricultural landscapes with high spatial variability of soil properties.

Soil dependent N2O measurements were observed across each transect. Elevation, texture as well as soil water content (SWC) showed a clear influence on N2O emissions. High emissions were measured in plots characterized by a loamy texture, high SWC and locations at higher elevations. In addition, lower emissions were measured at the edge point of the given transect, which could be described as an edge effect.

Evaluations of 15N tracer application results showed significant higher 15N leaching in low yield soils, which tend to have a higher sand content. High yield soils showed lower N-leaching. A strong dependence on soil texture and SWC was visible in the field cultivated with sunflower (Helianthus annuus L.): plots with higher sand content and lower SWC located at the center of the transect showed a higher N-leaching. This finding is in agreement with measured N2O emissions, which were noticeably lower in these areas.

In conclusion, soil heterogeneity in agricultural fields originating from differences in soil texture, SWC and topography show a clear impact on N transformations and N emissions.

How to cite: Zentgraf, I., Hoffmann, M., and Holz, M.: Does soil heterogeneity drive nitrogen transformation in agricultural landscapes? Towards an increased process understanding by quantification of N emissions and N transformation in soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3495, https://doi.org/10.5194/egusphere-egu22-3495, 2022.

EGU22-4806 | Presentations | BG1.3 | Highlight

Global NH3 emissions from livestock management : development of a module within a land surface model and impact on atmospheric chemistry 

Maureen Beaudor, Nicolas Vuichard, Juliette Lathière, Martin Van Damme, Lieven Clarisse, and Didier Hauglustaine

Ammonia (NH3) is a key species in the atmosphere, playing a crucial role in air quality and climate through the formation of sulfate and nitrate particles. Moreover, NH3 surface deposition alters ecosystems. About 85% of NH3 global anthropogenic emissions are related to food and feed production and in particular to the use of mineral fertilizers and manure management. Even though the estimate of the emissions from livestock can reach 36 Tg N/yr, they are generally not represented explicitly in global land surface models.  Most global chemistry transport models rely on bottom-up emission inventories subject to large uncertainties. Our objective consists of replacing these external emissions data by dynamical emissions computed by ORCHIDEE, a terrestrial ecosystem model including the carbon and the nitrogen cycles. This new version of the ORCHIDEE model includes a detailed integrated scheme for livestock management, from housing and storage to grazing emissions. Ultimately, our work aims at developing an interactive nitrogen cycle model in a coupled climate-chemistry-vegetation model in order to investigate the impact of NH3 emissions from livestock on atmospheric chemistry and climate, and the associated feedbacks.

In this study, we describe and present global NH3 emissions from livestock calculated based on the new version of the ORCHIDEE land surface model . We evaluate NH3 emissions simulated by ORCHIDEE with previous inventories and model estimates. An analysis of key parameters driving the soil NH3 emissions (pH of the manure, the timing of the N application, the surface atmospheric concentration etc… ) have also been performed in order to assess the sensitivity of the simulated emissions. Last, we investigate the impact of prescribing these new simulated emissions on atmospheric chemistry, using the global atmospheric chemistry transport model LMDZ-OR-INCA. The simulated NH3 atmospheric columns are evaluated by global and regional comparisons with the spaceborne IASI instrument measurements. The products used are monthly gridded NH3 distributions using morning observations of IASI-(Metop)A and IASI-(Metop)B for the period 2011-2017. In addition, we compare the ammonia atmospheric columns simulated based on the dynamical livestock emissions and based on reference bottom-up emission inventories. Finally, we investigate the impact of the different NH3 emission inventories on key atmospheric species concentrations.

How to cite: Beaudor, M., Vuichard, N., Lathière, J., Van Damme, M., Clarisse, L., and Hauglustaine, D.: Global NH3 emissions from livestock management : development of a module within a land surface model and impact on atmospheric chemistry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4806, https://doi.org/10.5194/egusphere-egu22-4806, 2022.

EGU22-5064 | Presentations | BG1.3

Gas kinetics and stoichiometry from four fungi incubated under conditions favouring denitrification 

Lena Rohe, Reinhard Well, Shahid Nadeem, and Peter Dörsch

Even though the ability of fungi to produce the greenhouse gas nitrous oxide (N2O) during denitrification has been demonstrated, the proportion N2O emissions from fungal denitrification in soils cannot yet be determined or predicted. In order to develop methods for estimating the fungal proportion, N2O must be partitioned to bacterial and fungal denitrification. The denitrification regulatory phenotype (DRP) is well described for a number of bacterial strains (Bergaust et al. 2010, Bergaust et al. 2011), but to our knowledge there are only few data relating to the fungal DRP in terms of oxygen (O2) tension in fully stirred cultures at which they start producing N2O. The aim of this study was to analyse the kinetics of fungal denitrification combined with analysis of the isotopic composition of N2O. In particular, the 15N site preference of N2O (SP-N2O) is known to be a promising tool to differentiate between N2O produced during bacterial and fungal denitrification.

Four fungal species (Fusarium oxysporum, Fusarium decemcellulare, Fusarium solani fsp. pisi and Chaetomium funicola) were incubated as batch cultures in a robotized incubation system (Molstad et al. 2007) for 165h. Batch cultures were incubated in 120 ml flasks containing 50 ml of growth medium amended with ample amounts of carbon and nitrate in a He atmosphere with 2 vol%O2. To test for pH effects, a complex medium (Shoun et al. 1992) with pH values adjusted to 6.9 and 7.4 as well a minimal medium (Dox 1910) with a pH value of about 7.9 were used. O2 consumption and production of nitric oxide (NO), N2O, dinitrogen (N2) and carbon dioxide (CO2) were monitored at high temporal resolution while isotopic composition of N2O was analysed in samples taken manually at selected time points.

All four fungal cultures quickly consumed O2. NO production increased strongly before O2 was completely consumed and was followed by immediate N2O production. The kinetics of N2O production differed to published kinetics of denitrifying prokaryotes by showing a lower sensitivity to O2. This could result in a larger share of fungal denitrification under microaerobic conditions in soil.

Isotopic analysis of N2O confirmed previous results of specifically high SP-N2O values of fungal produced N2O. We further showed that SP-N2O values of fungal N2O are quite stable and do not depend on denitrification kinetics. Likewise, incubation conditions such as pH of the medium had little impact on SP-N2O values. These findings support the usage of SP-N2O values for partitioning N2O soil fluxes and provide a tool to study the biology of fungal denitrification under field conditions, which is needed to develop mitigation strategies of N2O from fungal denitrification.

References:

  • Bergaust, Y. Mao, L. R. Bakken, Å. Frostegård, Appl Environ Microbiol 2010, 76.
  • Bergaust, L. R. Bakken, Å. Frostegård, Biochem Soc Trans 2011, 39.
  • Molstad, P. Dörsch, L. R. Bakken, J Microbiol Methods 2007, 71, 202.
  • Shoun, D.-H. Kim, H. Uchiyama, J. Sugiyama, FEMS Microbiol. Lett. 1992, 94, 277.
  • W. Dox, U.S. Dept. of Agriculture, Bureau of Animal Industry, Washington, D.C., 1910, 70 p.

How to cite: Rohe, L., Well, R., Nadeem, S., and Dörsch, P.: Gas kinetics and stoichiometry from four fungi incubated under conditions favouring denitrification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5064, https://doi.org/10.5194/egusphere-egu22-5064, 2022.

EGU22-5489 | Presentations | BG1.3

Glacial Rock Flour as soil fertility amendment increases N fixation activity in red clover and enhances soil N2O reduction. 

Fotis Sgouridis, Harry Forrester, Sarah Tingey, and Jemma Wadham

The current climate trajectory in conjunction with agricultural intensification and the reliance on synthetic fertilisers, present further threat to the resilience of future food production through their contributions to soil degradation and consequent climatic feedback. Innovative sustainable agricultural technologies are needed to produce nutritious and equitable food products in line with the UN’s goal for Zero Hunger and sustainable development. Glacial Rock Flour (GRF) is a fine mineral rock dust, made available through the glacial abrasion of bedrock, and is often enriched in nutrients (e.g. Potassium, Phosphorous, Silicon, trace elements) but low in Nitrogen. It would therefore be a suitable soil fertility amendment for legume crops grown in acidic, nutrient poor soils often found in many mountainous regions (e.g. Hindu Kush Himalaya), where GRF is considered an alluvial ‘waste’ silting up dams and reservoirs. We have investigated the effect of GRF soil amendments in soil-plant mesocosms using a typical UK silt loam arable soil (pH~7) for cultivating red clover (Trifolium pratense) inoculated with Rhizobium. GRF from the Chhota Shigri (India) and Sólheimajökull (Iceland) glaciers were applied at 2 and 20 T/ha, while no GRF treatments included synthetic fertilizer applications of phosphorus (P), potassium (K) and P+K, and they were all compared against control red clover plants grown with no soil amendments. The nitrogen fixation capacity of red clover was estimated via 15N natural abundance against a rye grass control (Lolium perenne) in two harvests on weeks 14 and 19. Both 20 T/ha GRF treatments appeared to stimulate fixed nitrogen yield compared to synthetic fertilizer treatments and control red clover plants, while the stimulation was more pronounced in the 2nd harvest as the soil nutrients were progressively depleted. Soil greenhouse gas fluxes over the growth period (weeks 4-14) were monitored by enclosing pots in sealed chambers. While no difference was observed in carbon dioxide fluxes between treatments, nitrous oxide (N2O) flux was negative for all red clover mesocosms with the N2O reduction being more prominent in both 20 T/ha GRF treatments towards the end of the first growth period (week 14). Gross N mineralization and nitrification were estimated in post-harvest soils from all the mesocosms using the isotope dilution method, while 15N-N2O and 15N-N2 production were also measured after amending the soils with 98 at% 15N-NH4+ and 15N-NO3-.  Gross N mineralization was not different between treatments, while nitrification was non-detectable, indicating a very tightly coupled N cycle between Rhizobium and red clover. However, when excess nitrate was applied, bacterial denitrification was active but the amendment of the soils with GRF appeared to reduce the production of N2O and promote complete denitrification to N2. Our novel study on the properties and application of GRF as a sustainable soil fertility amendment under a low nitrogen cropping system, holds promise that it can promote leguminous nitrogen fixation and a tightly-coupled N cycle that maximises N-use efficiency while mitigating N2O emissions by promoting complete denitrification.

How to cite: Sgouridis, F., Forrester, H., Tingey, S., and Wadham, J.: Glacial Rock Flour as soil fertility amendment increases N fixation activity in red clover and enhances soil N2O reduction., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5489, https://doi.org/10.5194/egusphere-egu22-5489, 2022.

EGU22-6937 | Presentations | BG1.3

The effects of drip irrigation with nanobubbles aerated water on soil N transformation 

Shahar Baram, Maya Weinstien, Guy Kaplan, and Shmulik Friedman

In recent years, irrigation with nanobubbles aerated water (NB-water) [i.e., air or oxygen-NB (ONB)] has emerged as a new method to alleviate transient hypoxic conditions in the rhizosphere. We aimed to study the effect of surface and subsurface drip irrigation with ONB aerated waters [i.e., fresh (0.4 dS/m), secondary urban treated wastewater (TWW; 1.3 dS/m), saline (3dS/m)] on soil nitrogen transformations. Greenhouse lysimeter experiments were conducted in vertisol (58% clay), sand (98% sand), compost, and sand:compost (1:1) mixture, under well aerated and poorly aerated conditions. Ammonium-N to nitrate-N ratios in the irrigation waters ranged from 15% to 50%.  In all the experiments, irrigation with ONB water, with dissolved oxygen (DO) concentrations of 11 to 35 mg/L, increased the transient buildup of nitrite in the porewater, even under well-aerated conditions (soil air O2> 19%). The most significant effects were observed in the sand, sand:compost, and compost media, where nitrite concentrations were 2 – 8 times greater than the controls and reached over 65 mg/L. Despite the increased nitrite concentrations, irrigation with ONB waters reduced the nitrous oxide fluxes by 4 – 85%. Both phenomena suggested higher oxygen availability in the soil. Nitrite buildup implies that ammonia (NH3) oxidation may not be the rate-limiting step of nitrification under irrigation with ONB aerated water. 

How to cite: Baram, S., Weinstien, M., Kaplan, G., and Friedman, S.: The effects of drip irrigation with nanobubbles aerated water on soil N transformation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6937, https://doi.org/10.5194/egusphere-egu22-6937, 2022.

Dissolved organic nitrogen (DON) is a kind of reactive nitrogen in the nitrogen cycling processes, which has been neglected for decades because of the difficulty in measurement, leading to underestimating the nitrogen saturation in the ecosystem. As a result, the need for a complete understanding of DON export behaviors is urgent. This study compares the DON export behaviors to previous studies, focusing on the relationship between DON, dissolved inorganic nitrogen (DIN), dissolved organic carbon (DOC), carbon-nitrogen coupling. We analyzed the data collected at the Fushan Experimental Forest (FEF) in northeastern Taiwan. Preliminary research results showed that (1) behaviors of DON export were unchanged between wet and dry seasons, but only switched at typhoon events, (2) the concentration of DOC was deficient in stream water, (3) unknown endmember between DON and DOC appeared at typhoon events, (4) the high bioavailability of DON occurred in soil and stream water, and (5) the concentration of DOC in soil pool was significantly higher than that of stream water. This study infers that typhoon disturbance appeared to alter the carbon limiting at FEF, causing the change of DON export patterns.

How to cite: Yu, Y.-L., Lee, L.-C., and Huang, J.-C.: Flow regime shifts the carbon-nitrogen coupling of dissolved organic nitrogen losses in a subtropical mountainous catchment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6942, https://doi.org/10.5194/egusphere-egu22-6942, 2022.

EGU22-7562 | Presentations | BG1.3

Fertilizer type effect on nitrous oxide (N2O) emissions in a Swedish long-term field experiment 

Rong Lang, Muhammad Shahbaz, Katharina H. E. Meurer, Gunnar Börjesson, and Thomas Kätterer

Fertilization in agriculture contributes substantially to an increase in nitrous oxide (N2O) emission to the atmosphere, optimizing fertilization is one of the mitigation strategies to reduce greenhouse gas (GHG) emissions while maintaining high crop production. In the Ultuna long-term frame trial, treatments including organic amendments and different types of mineral nitrogen fertilizers have been applied since1956 to quantify their effects on crop production, soil carbon and nitrogen cycling. However, the understanding of their effect on GHG emissions from soils is still quite limited. For this reason, we chose four treatments, including no fertilizer (control), calcium nitrate, ammonium sulfate and calcium cyanamide to study the mineral fertilizer type effect on N2O emissions and the plant-soil-microbe interactions over one crop growth period.  

N2O fluxes in the growing season were continuously measured from the 1 June to 15 Oct in 2019, using a Picarro N2O analyzer and 12 automated eosAC chambers. The frame trial has a randomized complete block design and we chose treatments in three blocks as replicates. In each plot, we placed two sensors to measure soil moisture and temperature. A mixed model was used to test the effect of fertilizer type and measurement date, with consideration of auto-correlations in the repeated measurements. Soil moisture and temperature were added to the regression model to quantify the controlling factors of the N2O fluxes. Measurement date was treated as a continuous variable.

The effects of both treatment and measurement date were statistically significant. Despite its higher pH values, the calcium nitrate  treatment emitted significantly more N2O than the control: 90.8±23.4 compared with 32.2±8.3 nmol m-2 s-1, respectively. The treatment with calcium cyanamide had pH-values and total N similar to those in the calcium nitrate treatment, but N2O emissions were 72% lower (25.0±6.5 nmol m-2 s-1) than the emission in the calcium nitrate treatment. Due to low soil pH, N2O fluxes were constantly low in the ammonium sulfate treatment, with an average emission of 24.3±6.3 nmol m-2 s-1. The temporal dynamics differed a lot between treatments, as suggested by significant interaction between treatment and measurement date. Further, regression with soil moisture and temperature showed that both variables contributed to explaining the temporal variation of N2O fluxes mainly in the control and calcium nitrate treatments. In contrast, N2O fluxes in the calcium cyanamide treatment were low throughout the growing season, suggesting that it effectively suppressed not only nitrification in the early growing season, but also the denitrification process in the late growing season.

Considering the highest maize biomass and lowest N2O emissions the calcium cyanamide treatment, using calcium cyanamide as nitrogen fertilizer has a great potential to reduce N2O emissions from agricultural soils without compromising crop production.  

How to cite: Lang, R., Shahbaz, M., Meurer, K. H. E., Börjesson, G., and Kätterer, T.: Fertilizer type effect on nitrous oxide (N2O) emissions in a Swedish long-term field experiment, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7562, https://doi.org/10.5194/egusphere-egu22-7562, 2022.

EGU22-7612 | Presentations | BG1.3 | Highlight

Global hotspots of nitrous oxide mitigation potentials in croplands 

Feng Zhou and Xiaoqing Cui

Mitigating soil nitrous oxide (N2O) emissions is essential for staying below a 2°C warming threshold. However, accurate assessments of mitigation potential are limited by uncertainty and variability in direct emission factors (EFs). To assess where and why EFs differ, we create high-resolution maps of crop-specific EFs based on 1,507 georeferenced field observations. Here, using a data-driven approach, we show that EFs vary by two orders of magnitude over space. At global and regional scales, such variation is primarily driven by climatic and edaphic factors rather than the well-recognized management practices. Combining spatially explicit EFs with N surplus information, we conclude that global mitigation potential without compromising crop production is 30% [95% CI: 17-53%] of direct soil emissions of N2O, equivalent to the entire direct soil emissions of China and the United States combined. Two thirds (65%) of mitigation potential could be achieved on one fifth of global harvested area, mainly located in humid subtropical climate and across gleysols and acrisols. These findings highlight the value of a targeted policy approach on global hotspots that could deliver large N2O mitigation as well as environmental and food co-benefits.

How to cite: Zhou, F. and Cui, X.: Global hotspots of nitrous oxide mitigation potentials in croplands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7612, https://doi.org/10.5194/egusphere-egu22-7612, 2022.

EGU22-7977 | Presentations | BG1.3

Atmospheric acidity and its impacts on macronutrient deposition and plant growth 

Andrea Arangio, Kalliopi Violaki, Juan-Carlos Quezada Rivera, Megan He, Ghislain Motos, Luca Bragazza, Charlotte Grossiord, Alexandre Buttler, and Athanasios Nenes

Biological diversity and competition among species in ecosystems are sensitive to changes in macronutrient supply and nutrient availability. Human activity is intensively and extensively altering macronutrient cycles from a regional to a global scale with rates that can far exceed natural ones. Moreover, anthropogenic pollution exposes ecosystems to additional nutrients and stressors. These processes, although not well studied, can have a strong impact on ecosystem composition and productivity. In this study, we characterize the atmospheric deposition of bioavailable macronutrients from air pollution and study their impact on plant (oat) productivity and soil quality at a site in the Bois-Chamblard forest outside of Lausanne, Switzerland by Lake Geneva.

To evaluate the importance of atmospheric deposition as a nutrient path for soil and plants, we set up a mesocosm experiment where plants and bare soil were exposed to atmospheric deposition for four months (during Spring and Summer, 2021) and compared against replicates not exposed to atmospheric deposition. Carbon (C), N, P in plant and soil, as well as soil enzymatic activity, fungi and bacterial communities are quantified for each member of the mesocosm experiment. Quantification of the total nitrogen (N) and phosphorous (P), gas- and aerosol-species (inorganic/organic species and metals) in rain water, dry deposition and airborne particles and soil is carried out.

We find that plants exposed to atmospheric deposition display higher photosynthetic activity, larger N content and higher capacity to compete for nutrients in the soil. The soil community in the atmospheric deposition treatment shown higher nitrification rate and enzymatic activity towards lignin decomposition compared to the control. These results indicates that atmospheric pollutants act as plant fertilizers fostering their control on soil microbial community and accelerating soil nutrient stocks consumption.

How to cite: Arangio, A., Violaki, K., Quezada Rivera, J.-C., He, M., Motos, G., Bragazza, L., Grossiord, C., Buttler, A., and Nenes, A.: Atmospheric acidity and its impacts on macronutrient deposition and plant growth, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7977, https://doi.org/10.5194/egusphere-egu22-7977, 2022.

EGU22-8543 | Presentations | BG1.3

Real-time soil nutrients monitoring 

Ernesto Saiz, Aleksandar Radu, Sami Ullah, Ruben Del-Rio-Ruiz, Mossab Alsaedi, and Sameer Sonkusale

The availability of nutrients is one of the main factors in soils that affect plant growth. This is something that has always been worrying humans; initially using natural fertilizers such as animal and human waste to enhance crop productivity. However, the industrial revolution brought the Haber-Bosch process (artificial nitrogen fixation), which posed a milestone on artificial fertilizers. The production of fertilizers increased exponentially during the twentieth century and is still increasing although at a slower pace. It has had not only positive results, e.g. food production, but is also causing major environmental, health and economic problems.

Because of these problems, it is critical to improve soil management strategies at the precise spatial scales in order to protect human health and the environment, while food production is also guaranteed. To do so, what is needed is a low-cost way to measure nutrients in the soil, in real-time, at different spatial scales.

During recent years, researchers have been working on the adaptation and modification of Ion Selective Electrodes for the analysis of nutrients directly in the soil. However, low precision and accuracy, intense instrument handling (pre and post-calibration), and complex data processing is preventing its general use.

We will present here two modifications of our first prototype of a low-cost ISE-based sensor probe. The probe allows measurements in situ and/or continuous monitoring of up to 16 chemical species. We will here showcase preliminary data obtained by measuring four replicates of four analytes. We also apply the Bayesian calibration methodology previously developed by us in order to improve the precision and accuracy of measurements.

How to cite: Saiz, E., Radu, A., Ullah, S., Del-Rio-Ruiz, R., Alsaedi, M., and Sonkusale, S.: Real-time soil nutrients monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8543, https://doi.org/10.5194/egusphere-egu22-8543, 2022.

EGU22-11430 | Presentations | BG1.3

Risks of converting coniferous forests to broadleaved species 

Caitlin Lewis, Martin Lukac, Elena Vanguelova, and Matthew Ascott

Non-native coniferous plantations in the UK have long been associated with potentially negative impacts on surface water and groundwater quality due to high levels of nitrogen accumulation in their soils. Recent changes in UK forestry policy and targets and in attitudes towards biodiversity triggered a shift towards restocking conifer forests with broadleaved species. Broadleaved species are typically associated with lower rates of nitrogen deposition, scavenging and nitrate leaching, so it is often assumed that this change in management will enhance water quality. However, the conversion of coniferous woodland to broadleaved woodland typically stimulates the breakdown of organic matter, leading to a pulse release of nutrients which cannot be taken up rapidly enough by the nascent broadleaved forest.

 

To assess the significance of this process we conducted a study at Thetford Forest, Norfolk, a forest exposed to elevated levels of nitrogen deposition.  We measured throughfall and soil solution chemistry, soil C/N ratios, pH and net nitrification in a chronosequence of stands (0-72 years old) in the conversion process. Observed changes in organic soil C/N ratios indicate the potential for elevated nitrate leaching fluxes within the first decade post-conversion. Results also show an increase in net nitrification in the summer five to eight years post-conversion, followed by an accumulation of nitrogen in the deep mineral soils (30-90 cm depth) ten years post-conversion. Our ongoing analysis of deep soil solution and throughfall chemistry will confirm whether these observations are linked to elevated leaching fluxes in the first decade after conversion. Mature broadleaf stands were unexpectedly associated with greater concentrations of throughfall nitrate from August-October, and lower rates of soil nitrification in the summer than coniferous stands. Further analyses from winter-spring 2022 will explore seasonal variations in throughfall chemistry between broadleaf and coniferous stands in the context of elevated nitrogen deposition.

 

Our observations highlight the need to consider interactions between the effect of land management, seasonality and elevated deposition on nitrogen cycling processes to understand the impact of intensive nitrogen use on terrestrial nitrogen fluxes.    

How to cite: Lewis, C., Lukac, M., Vanguelova, E., and Ascott, M.: Risks of converting coniferous forests to broadleaved species, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11430, https://doi.org/10.5194/egusphere-egu22-11430, 2022.

EGU22-11621 | Presentations | BG1.3 | Highlight

A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm 

Michael Dannenmann, Elisabeth Ramm, Chunyan Liu, Per Ambus, Klaus Butterbach-Bahl, Bin Hu, Pertti J. Martikainen, Maija E. Marushchak, Carsten W. Mueller, Heinz Rennenberg, Michael Schloter, Henri M. P. Siljanen, Carolina Voigt, Christian Werner, and Christina Biasi

The paradigm that permafrost-affected soils show restricted mineral nitrogen (N) cycling in favor of organic N compounds is based on the observation that net N mineralization rates in these cold climates are negligible. However, we find here that this perception is wrong. By synthesizing published data on N cycling in the plant-soil-microbe system of permafrost ecosystems we show that gross ammonification and nitrification rates in active layers were of similar magnitude and showed a similar dependence on soil organic carbon (C) and total N concentrations as observed in temperate and tropical systems. Moreover, high protein depolymerization rates and only marginal effects of C:N stoichiometry on gross N turnover provided little evidence for N limitation. Instead, the rather short period when soils are not frozen is the single main factor limiting N turnover. High gross rates of mineral N cycling are thus facilitated by released protection of organic matter in active layers with nitrification gaining particular importance in N-rich soils, such as organic soils without vegetation. Our finding that permafrost-affected soils show vigorous N cycling activity is confirmed by the rich functional microbial community which can be found both in active and permafrost layers. The high rates of N cycling and soil N availability are supported by biological N fixation, while atmospheric N deposition in the Arctic still is marginal except for fire-affected areas. In line with high soil mineral N production, recent plant physiological research indicates a higher importance of mineral plant N nutrition than previously thought.

Our synthesis shows that mineral N production and turnover rates in active layers of permafrost-affected soils do not generally differ from those observed in temperate or tropical soils. We therefore suggest to adjust the permafrost N cycle paradigm, assigning a generally important role to mineral N cycling. This new paradigm suggests larger permafrost N climate feedbacks than assumed previously.

How to cite: Dannenmann, M., Ramm, E., Liu, C., Ambus, P., Butterbach-Bahl, K., Hu, B., Martikainen, P. J., Marushchak, M. E., Mueller, C. W., Rennenberg, H., Schloter, M., Siljanen, H. M. P., Voigt, C., Werner, C., and Biasi, C.: A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11621, https://doi.org/10.5194/egusphere-egu22-11621, 2022.

EGU22-13309 | Presentations | BG1.3

Low atmospheric nitrogen deposition in southern central Siberia does not trigger any nitrogen limitation in the growth of mountain lake phytoplankton 

Daniel Diaz-de-Quijano, Aleksandr Vladimirovich Ageev, Nikolay Vladimirovich Moshkin, Elena Anatolevna Ivanova, Yulia Dmitrievna Anishchenko, Olesia Valerevna Anishchenko, and Nadezhda Nikolaevna Sushchik

Anthropogenic disturbances of the nitrogen cycle are one of the most important issues for world ecology. Increased fluxes of atmospheric nitrogen deposition, including ammonium, nitrates, nitrites and other nitrogen oxides characterize the current state of nitrogen cycle. Scientists have found that this process might provide unproductive lakes with nitrogen enough for phytoplankton to turn from nitrogen to phosphorus limitation of growth. Nevertheless, atmospheric nitrogen deposition and its effect on phytoplankton primary production have not been uniformly studied around the world and significant areas remain understudied.

In this study, we measured the winter atmospheric deposition of nitrogen and phosphorus in the snow cover of an understudied region: the Ergaki Natural Park in the south of central Siberia. The concentrations in winter precipitation (40±16 mg of NO3-N m-2 0.58±0.13 mg of total P m-2) were used to estimate yearly yields (119±71 mg of NO3-N m-2 year-1 and 1.71±0.91 mg of total P m-2 year-1). These values approximately corresponded to the forecasts of worldwide mathematical models in the literature and were notably low for terrestrial sites, especially in the case of phosphorus. Measurements of d15N, total N and P in lake sediment cores confirmed the minor role of eventual atmospheric N deposition in the studied lakes, as compared to terrestrial inputs.

The atmospheric nitrogen deposition on the Ergaki mountain ridge was slightly lower than in northern Sweden, where the low atmospheric nitrogen deposition had been found to trigger nitrogen (instead of phosphorus) limitation of phytoplankton growth in unproductive lakes. Nevertheless, atmospheric phosphorus deposition in the study site was among the lowest ones on the mainland, if not the lowest. Due to this extremely low content of atmospheric nutrient deposition, the stoichiometry of N:P in snow and lake water did not correlate, so our lakes did not belong to the group of lakes in the world that are influenced by atmospheric deposition of nutrients. According to our observations, both nitrogen and phosphorus can periodically be limiting factors of phytoplankton in Ergaki lakes.

In conclusion, firstly, the Ergaki Natural Park is an ideal place to study the effects of global warming with a minimal interference of atmospheric nitrogen deposition. Secondly, even at low levels of atmospheric nitrogen deposition in places where atmospheric phosphorus deposition is very low, nitrogen is not necessarily the limiting factor of phytoplankton growth, which may contradict the general character of the currently accepted paradigm. Further studies should check the year-round deposition of nutrients and expand the number of lakes and regions in Siberia, where a significant part of the lakes is not subject to severe anthropogenic pollution.

This study was funded by the Russian Foundation of Basic Research grant number 20-04-00960.

How to cite: Diaz-de-Quijano, D., Ageev, A. V., Moshkin, N. V., Ivanova, E. A., Anishchenko, Y. D., Anishchenko, O. V., and Sushchik, N. N.: Low atmospheric nitrogen deposition in southern central Siberia does not trigger any nitrogen limitation in the growth of mountain lake phytoplankton, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13309, https://doi.org/10.5194/egusphere-egu22-13309, 2022.

EGU22-1203 | Presentations | BG1.4 | Highlight

Deforestation and climate change: The multiple pressures over Amazonian forests 

Paulo Artaxo, Luiz Augusto Toledo Machado, Marco Aurélio Menezes Franco, Itiara Mayra Barbosa de Albuquerque, Luciana Varanda Rizzo, Julia Shimbo, Ane Alencar, Susan Trumbore, and José Reinaldo Silva

Amazonia is under significant stress from both deforestation and climate change. Multiple pieces of evidence show that the links between the hydrological and carbon cycles are fast changing. Deforestation is increasing in Amazonia, and in 2021, about 13,35 km² of forests were converted, a value 22% larger than 2020. On the deforestation side, the government's recent public policies favor illegal occupation of public lands and invasion of indigenous territories protected by the Brazilian constitution. Deforestation brings forest degradation to the edges of deforested areas, increasing carbon emissions. The impact of climate change is less clear, with changes in the hydrological cycle and increased temperature, promoting forest degradation that makes parts of the Amazon Forest become a carbon source.

The Amazonian forest is a very complex system with multiple anthropogenic and climate change pressures. It is hard to know where a possible Amazonian tipping point could be and which variables or values could be the indicators for this possible tipping point. The role of intensified climate extremes is another critical variable, with Amazonia under increased intense droughts/inundation cycles in the last 30 years. Remote sensing measurements show that vapor pressure deficit is increasing for both perturbed Eastern and at the pristine Northern Amazonia. Several different studies show that the carbon uptake by undisturbed forests is not equilibrating the carbon emissions by deforestation for parts of Amazonia. CO2 emissions associated with deforestation are increasing. The MapBiomas system provides detailed land-use change maps linked to meteorological information to apportion carbon emissions to forest degradation or deforestation. The role of soil emissions is not fully quantified for the overall Amazonia. We are developing a basin-wide system using big data strategies with machine learning, artificial intelligence, and other advanced techniques to address drivers for land-use changes in Amazonia and carbon and methane emissions and sinks. Flooded areas in Amazonia show significant methane emissions, and the effects of increasing floods and droughts cycles have an important impact on methane emissions. First results will be presented, with CO2 and CH4 ground-based and remote sensing measurements in Amazonia, coupled with MapBiomas land-use change maps.

How to cite: Artaxo, P., Toledo Machado, L. A., Menezes Franco, M. A., Barbosa de Albuquerque, I. M., Rizzo, L. V., Shimbo, J., Alencar, A., Trumbore, S., and Silva, J. R.: Deforestation and climate change: The multiple pressures over Amazonian forests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1203, https://doi.org/10.5194/egusphere-egu22-1203, 2022.

EGU22-2592 | Presentations | BG1.4

The ATTO Micrometeorological Intercomparison Experiment (ATMIX) 

Luca Mortarini, Nelson Dias, Cleo Quaresma Dias, Daiane Brondani, Otavio Acevedo, Antônio Manzi, Pablo de Oliveira, Anywhere Tsokankunku, Fernando Rossato, Alessandro Araújo, Mathias Soergel, and Carlos Alberto Nobre Quesada

A central constituent of the ATTO project  is the deployment of an array of sonic anemometers to measure vertical profiles of means and second-order moments of the wind velocity vector. The two instruments used are the Campbell Scientific Instruments CSAT-3B and the Thies Ultrasonic Anemometer 3D. The accuracy of the vertical profiles of turbulent quantities critically depensds on an absence of bias between the measurement levels; however, dedicated intercomparisons of the sonic anemometers used in ATTO have not been previously performed.  The main objective of the experiment was to check how close the sonic anemometers designated to be installed respond to the same atmospheric conditions, and to develop confidence in interpreting the measured data. 

How to cite: Mortarini, L., Dias, N., Quaresma Dias, C., Brondani, D., Acevedo, O., Manzi, A., de Oliveira, P., Tsokankunku, A., Rossato, F., Araújo, A., Soergel, M., and Nobre Quesada, C. A.: The ATTO Micrometeorological Intercomparison Experiment (ATMIX), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2592, https://doi.org/10.5194/egusphere-egu22-2592, 2022.

EGU22-2703 | Presentations | BG1.4

The effects of elevated CO2 and phosphorus limitation shaping fine root functioning in Central Amazon forests 

Laynara F. Lugli and Carlos Alberto Quesada and the AmazonFACE team

One of the most important questions that remain open in terrestrial ecology refers to how the Amazon rainforest, the largest tropical forest in the world, will respond to elevated atmospheric CO2. Since a large part of the Amazon grows in soils with very low phosphorus (P) availability, understanding how potential nutrient limitation could impact forests in a changing world becomes crucial. There is strong evidence for a positive effect of elevated CO2 on plant growth but sustaining such a response in the Amazon would require plants to increase their access to P, making it important to understand the effects of elevated CO2 on root P-uptake strategies. To this end, we installed eight Open Top Chambers (OTC) in an understory forest in Central Amazon in Manaus, Brazil, being four control with ambient CO2 (aCO2) and four treatment with +200 ppm CO2 (eCO2). Inga edulis, a common N-fixing tree in the area, was chosen as study species. In each OTC, I. edulis was grown in six pots, three containing control soil from the study area and three containing control soil with 600 mg/kg of P added as triple super phosphate. After two years, plants were harvested and total soil respiration, total root dry mass, root nodulation, root morphological traits (mean diameter, specific root length – SRL, specific root area – SRA and root tissue density – RTD) and potential root phosphatase activity were measured. Total soil respiration was significantly higher in both treatments with eCO2 when compared to treatments with aCO2. Total dry root biomass followed a similar pattern, and root biomass in the eCO2 and P+eCO2 treatments were twice that of the other two aCO2 treatments. Plants invested in more fine roots (< 1 mm diameter) than in coarse roots with eCO2-only, whilst in P+eCO2, both fine and coarse roots biomass increased. No nodules were detected in control plants, whilst almost 75% of plants growing in P+eCO2 and 30% of plants growing in eCO2-only and P-only displayed nodulation. Mean fine root diameter for plants growing in eCO2-only was significantly higher than all other treatments, leading to a significant decrease in SRL and RTD, with no changes in SRA. In both treatments with eCO2, fine root phosphatase activity (expressed per root dry mass and specific area) significantly decreased in comparison to aCO2. However, when extrapolating root phosphatase activity for total fine root biomass, pot-level phosphatase exudation was twice as high in eCO2 than in aCO2 treatments. Our results clearly point to a shift in plant belowground strategies, suggesting an even stronger control of nutrient acquisition mechanisms by eCO2 than P addition. With eCO2, plants allocated much more biomass to fine roots and nodules, rather than increased phosphatase exudation per root-unit. Such trade-off suggests that in this scenario, plants might acquire P directly by exploring higher soil volumes, whilst allocating extra C to N-fixing bacteria. We demonstrate how eCO2 and P availability can shape belowground plant traits pointing to important trade-offs that could determine ecosystem-scale changes in future climate scenarios.

How to cite: F. Lugli, L. and Quesada, C. A. and the AmazonFACE team: The effects of elevated CO2 and phosphorus limitation shaping fine root functioning in Central Amazon forests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2703, https://doi.org/10.5194/egusphere-egu22-2703, 2022.

EGU22-2869 | Presentations | BG1.4

An open-top chamber system for exposing Amazon understory vegetation to elevated atmospheric CO2 

Iokanam Pereira, Bruno Takeshi, Alacimar Guedes, Crisvaldo Souza, Carlos Quesada, and David Lapola

Tropical forests play a key role in the flux of terrestrial carbon (C). However, recent studies show tropical forest are losing over the years the ability to sink C from the atmosphere, one of the best explanations for that is the climate change caused by humanity in the last centuries and accelerating slightly every year. One of the ways to understand the changes in C fluxes in forest ecosystems in the short, medium, and long term are the Earth system models (ESMs). Nevertheless, simulations demonstrate that ESMs are not able to represent the decline in C sink by tropical forests in recent decades. Experiments that fertilize the atmosphere with carbon dioxide (eCO2) are essential to reduce uncertainties in future ESM projections about the possible effects of eCO2 on the carbon cycle. Open top chamber (OTC) allow the exposure of understory vegetation to eCO2 allowing the control and monitoring of the microenvironment in which they are inserted. Here, we describe the OTC system currently operating in the Amazon Free-Air CO2 Enrichment research program (AmazonFACE) in a mature forest in Central Amazonia, the analysis period is from 01/01/2020 to 12/31/2020. Each OTC is 2.40 m in diameter by 3.00 m in height, in which the concentration of CO2 ([CO2]) is monitored minute-by-minute using infrared gas analyzers, allowing the spatial and temporal control of [CO2]. The operation consists of keeping the [CO2] in the treatment OTCs (i.e., with eCO2) ≈ 200 µmol. mol1 above the [CO2] of the control OTCs (i.e., without eCO2) in the daytime (between 6:00 am - 6:00 pm). The [CO2] measurements on the treatment and control OTCs show that the desired concentration was successfully delivered, +262.4 ± 25.5 µmol / mol (mean ± SD) of the desired setpoint, i.e., 31 % above setpoint target. The eCO2 in the treatment OTCs worked 91% of the analyzed operational time, the remaining time was wasted with engineering failures (3%) and problems with the supply of CO2 (6%). The system was able to maintain the [CO2] above the setpoint, showing that the system configuration is capable of exposing understory vegetation even in a highly complex environment. The results demonstrate that the in-situ OTC system presented can be reproduced in different types of ecosystems, allowing better knowledge about metabolic processes that occur between atmosphere-plant-soil.

How to cite: Pereira, I., Takeshi, B., Guedes, A., Souza, C., Quesada, C., and Lapola, D.: An open-top chamber system for exposing Amazon understory vegetation to elevated atmospheric CO2, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2869, https://doi.org/10.5194/egusphere-egu22-2869, 2022.

EGU22-3731 | Presentations | BG1.4

Determination of OH radical concentrations between 80-325 m over the Amazon rainforest using BVOC measurements 

Akima Ringsdorf, Achim Edtbauer, Jordi Vila-Guerau de Arellano, Jonathan Williams, and Jos Lelieveld

The tropical rainforest is the largest source of VOCs to the global atmosphere [1], where they are oxidized primarily by the hydroxyl radical (OH) [2]. In-situ measurements of OH are rare, especially from tropical forests, but indirect OH estimates can be made using VOC concentrations measured from aircraft or towers. For this it is necessary to measure the vertical change in concentration of a specific VOC with a known OH rate coefficient, within a known reaction time. In this study volatile organic compounds (VOC) were measured on the Amazon Tall Tower Observatory (ATTO) from 3 heights (80, 150 and 325 m) above the Amazon rainforest with a PTR-TOF-MS 4000 (IONICON Analytik GmbH). Typically to estimate OH, the convective timescale of the boundary layer is taken as the approximate reaction time. However, here we have developed a new method to determine the vertical transport based on the dynamic time warping technique. Median averaged transport times from 80 m to 325 m ranged from 105 to 15 minutes with decreasing values throughout the day from 06:00 to 15:00 as thermal and shear driven convection increases. We apply this method to determine effective OH concentrations between 80-325 m using isoprene and its oxidation products (methyl vinyl ketone, methacrolein and ISOPOOH) and compare these empirically derived values to values from the large-eddy simulation DALES [3]. The timescales of turbulent mixing and OH chemistry are similar, so both govern the vertical change in concentration.

[1] Guenther, Alex. “Biological and Chemical Diversity of Biogenic Volatile Organic Emissions into the Atmosphere.” ISRN Atmospheric Sciences 2013 (2013): 1–27. https://doi.org/10.1155/2013/786290.

[2] Lelieveld, Jos, Sergey Gromov, Andrea Pozzer, and Domenico Taraborrelli. “Global Tropospheric Hydroxyl Distribution, Budget and Reactivity.” Atmospheric Chemistry and Physics 16, no. 19 (2016): 12477–93. https://doi.org/10.5194/acp-16-12477-2016.

[3] Vilà-Guerau de Arellano, J., X. Wang, X. Pedruzo-Bagazgoitia, M. Sikma, A. Agustí-Panareda, S. Boussetta, G. Balsamo, et al. “Interactions Between the Amazonian Rainforest and Cumuli Clouds: A Large-Eddy Simulation, High-Resolution ECMWF, and Observational Intercomparison Study.” Journal of Advances in Modeling Earth Systems 12, no. 7 (2020): 1–33. https://doi.org/10.1029/2019MS001828.

How to cite: Ringsdorf, A., Edtbauer, A., Vila-Guerau de Arellano, J., Williams, J., and Lelieveld, J.: Determination of OH radical concentrations between 80-325 m over the Amazon rainforest using BVOC measurements, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3731, https://doi.org/10.5194/egusphere-egu22-3731, 2022.

EGU22-8810 | Presentations | BG1.4

Amazonas Rainfall Modifying Gas Concentration and Forming Nucleation Particles Near the Surface 

Luiz A. T. Machado, Christopher Pöhlker, Hartwig Harder, Meinrat O. Andreae, Paulo Artaxo, Santiago Botia, Yafang Cheng, Marco A. Franco, Leslie Kremper, Shujiro Komiya, Jost Lavric, Jos Leliveld, Su Hang, C. Alberto Quesada, Mira Pöhlker, Susan Trumbore, David Walter, Jonathan Williams, Stefan Wolff, and Ulrich Pöschl

This study combines ground-based gas phase, particle, and rainfall measurements at the ATTO site to study the impact of rainfall events on greenhouse and reactive gas concentrations and discuss how this process is relevant for producing new particles. Measurements of CO2, CH4, CO, O3, NO, and NO2 concentrations were collected from the surface to 79m using a tower at the ATTO site in the central Amazon forest northeast of Manaus, Brazil. Particle size distribution was measured by an SMPS and rainfall by a rain gauge at the top of the tower. Data collection started in 2012, and this analysis covered the period up to 2020. The 30-minute interval dataset was used to study how convective events modify the concentration of these gases. During the rainfall events, CO2, CO, and CH4 concentrations decrease, though CH4 varies less with height than CO and CO2. The daily cycle of NO2 presents an interesting characteristic showing distinct daily evolution for the concentration in the upper and lower levels. The decrease in NO2 concentration in the upper level and the increase near the surface in the afternoon, which is the typical time of rainfall events, indicate that a specific process occurs near the surface. With the joint analysis of gas-phase observations with ultrafine particles and rainfall data, it was possible to evaluate the interesting physical-chemical processes occurring during the rainfall events that might be important for particles nucleation. The time of rainfall events was defined as the first-time rain rate reaching 3 mm/hours, a typical value of the beginning of convective rainfall events. Interestingly, during rainfall events, there is a significant injection of O3 above and inside the canopy, and at this moment, its concentrations can increase by 300%. At the same time, NO decreases, and NO2 increases its concentration, suggesting a reaction between NO and O3 forming NO2. The concentration of NO2 follows the increase in particle concentration smaller than 20nm. This result opens new perspectives on the role of new particle formation related to rain and vertical mixing in the Amazon.

How to cite: Machado, L. A. T., Pöhlker, C., Harder, H., Andreae, M. O., Artaxo, P., Botia, S., Cheng, Y., Franco, M. A., Kremper, L., Komiya, S., Lavric, J., Leliveld, J., Hang, S., Quesada, C. A., Pöhlker, M., Trumbore, S., Walter, D., Williams, J., Wolff, S., and Pöschl, U.: Amazonas Rainfall Modifying Gas Concentration and Forming Nucleation Particles Near the Surface, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8810, https://doi.org/10.5194/egusphere-egu22-8810, 2022.

EGU22-8935 | Presentations | BG1.4 | Highlight

Two decades of forest monitoring shows instability in the rainforests 

Chandrakant Singh, Ruud van der Ent, Lan Wang-Erlandsson, and Ingo Fetzer

The tropical terrestrial ecosystems naturally exist as alternative stable states, commonly referred to as forest and savanna ecosystems. However, these ecosystems, especially forests, are currently threatened by the risk of drought-induced forest-to-savanna transitions across the tropics and subtropics. Therefore, a better understanding of ecosystem dynamics and characteristics behind these alternative stable states is crucial in predicting their response to future hydroclimatic changes. Previous studies have analyzed these alternative stable states against precipitation predominantly based on space-for-time substitution. However, such a substitution provides a partial picture of ecosystem adaptation dynamics and associated ecosystem structural change over time. 

Here, we empirically study the transient state of tropical ecosystems and their hydroclimatic adaptations by examining remotely sensed tree cover and root zone storage capacity over the last two decades in South America and Africa. Tree cover represents the above-ground ecosystem structure's density, and is derived directly from MODIS satellite data. Whereas root zone storage capacity is the maximum amount of soil moisture that the vegetation can access for transpiration is derived using daily precipitation and evaporation data. 

We found that ecosystems at high (>75%) and low (<10%) tree cover adapt to changing precipitation by instigating considerable subsoil investment while experiencing limited tree cover change over time. For these ecosystems, the below-ground investment does not come at the cost of changing the above-ground ecosystem structure. Thus, we deem these ecosystems as stable since ecosystems' adaptive dynamics keep the structural characteristics intact. In contrast, unstable ecosystems at intermediate (30-60%) tree cover were unable to exploit the same level of adaptation as stable ecosystems, thus showing considerable changes to their above-ground ecosystem structure. We also found that ignoring this adaptive capacity of the ecosystem can underestimate the resilience of the forest ecosystems, which we find is largely underestimated in the case of the Congo rainforests. The results from this study emphasize the importance of the ecosystem's temporal dynamics and adaptation in inferring and assessing the risk of forest-savannah transitions under rapid hydroclimatic change.

How to cite: Singh, C., van der Ent, R., Wang-Erlandsson, L., and Fetzer, I.: Two decades of forest monitoring shows instability in the rainforests, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8935, https://doi.org/10.5194/egusphere-egu22-8935, 2022.

EGU22-8966 | Presentations | BG1.4

Seasonal and interannual variations of carbon fluxes at the Amazon Tall Tower Observatory site in 2014-2019 

Shujiro Komiya, Alessandro Carioca de Araújo, Jost V. Lavric, Bruce Nelson, Matthias Sörgel, Bettina Weber, Santiago Botia, Eliane Gomes-Alves, David Walter, Marta de Oliveira Sá, Stefan Wolff, Davieliton M. Pinho, Fumiyoshi Kondo, and Susan Trumbore

The vegetation and soils of the Amazon contain large amounts of carbon that may be vulnerable to loss given ongoing climate and land use change in the Amazon basin. Previous studies predicted that the Amazon rainforest would start to act as a net carbon source to the atmosphere by 2030-2040, and that it has switched from being a sink to source over the last decade. Using data from eddy covariance and vertical carbon dioxide profile measurement systems installed at the 80 m walk-up tower in the Amazon Tall Tower Observatory (ATTO) site, located in well-preserved central Amazon upland rainforest, we assessed net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (Reco) for the period 2014-2019. The NEE results indicate that the central Amazon upland rainforest was carbon neutral or a source during this 6-year period. Seasonal GPP variations were related to soil water availability and vapor pressure deficit. The strong 2015-2016 El Niño event decreased both GPP and Reco due to the unusually long dry period, but also contributed to carbon flux dynamics in post El Niño periods. In the 2017-dry season, we measured higher dry-season GPP compared with the other years, which we hypothesize was triggered by photosynthesis activation in sub-canopy and understory trees. This is supported by the minimum green crown fraction at upper canopy trees, indicating more light availability in lower canopy trees, and the higher fraction of absorbed photosynthetically active radiation, both recorded during the dry-season of 2017. Our results show that the ground-based measurement setup at ATTO is well suited to investigate the local carbon fluxes on seasonal to interannual time scales.

How to cite: Komiya, S., Carioca de Araújo, A., V. Lavric, J., Nelson, B., Sörgel, M., Weber, B., Botia, S., Gomes-Alves, E., Walter, D., de Oliveira Sá, M., Wolff, S., M. Pinho, D., Kondo, F., and Trumbore, S.: Seasonal and interannual variations of carbon fluxes at the Amazon Tall Tower Observatory site in 2014-2019, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8966, https://doi.org/10.5194/egusphere-egu22-8966, 2022.

EGU22-8975 | Presentations | BG1.4

Short-term responses of Inga edulis Mart. seedlings growing under elevated CO2 and phosphorus addition: understanding potential phosphorus constraints on plant responses to elevated CO2 in the understory of a central Amazon forest     

Gabriela U. Neves, Vanessa R. Ferrer, Sabrina Garcia, Vinicius F. de Souza, Tomas Domingues, Izabela Aleixo, Henrique Tozzi, Pedro A. C. L. Pequeno, Nathielly P. Martins, Alacimar Guedes, Iokanam S. Pereira, Juliane C. G. Menezes, Amanda R. M. Damasceno, Yago R. Santos, Maquelle N. Garcia, Anna C. M. Moraes, Ana Caroline M. Pereira, Bart Kruijt, and Carlos A. N. Quesada and the AmazonFACE Team

The increase in atmospheric CO2 concentration positively affects plant carbon assimilation and carbon stock in different biomes. However, there are uncertainties regarding how plants in tropical forests, especially in the Amazon rainforest, will respond to this increase, since a large part of the soils in the region present natural low phosphorus (P) availability, which could constrain positive effects of elevated CO2. Here, we investigated if P addition would interfere on leaf primary carbon metabolism and aboveground development responses under elevated CO2. For that, we used 46  seedlings of Inga edulis Mart., a native leguminous nitrogen-fixing species, exposed for 10 months (November 2019 - September 2020) to CO2 and P treatments. Plants grew in pots - half with natural P availability (-P) and half with P addition (+P) -, inside CO2 enrichment chambers - half with ambient CO2 (aCO2) and half with elevated CO2 (aCO2 + 200 ppm; eCO2), - in the understory of a primary forest in Central Amazonia, Manaus, Brazil.  A factorial experimental design was used, with 11-12 plants for each treatment: aCO2-P (control), aCO2+P, eCO2-P and eCO2+P. To assess the carbon metabolism, we measured light-saturated net CO2 assimilation (Asat), leaf respiration in the light (Rlight), leaf respiration in the dark (Rdark) and photorespiration (PR). To assess aboveground development, we measured plant height and diameter, crown height and diameter,  number of leaves and total leaf area. We found that eCO2, regardless of P availability, significantly increased Asat and Rlight, while decreasing Rdark and Asat:Rdark ratio, but it did not affect PR . Those results suggest that seedlings indeed assimilated more carbon under eCO2. However, irrespective of CO2 treatment, +P significantly increased aboveground responses. Under P addition, plants showed greater height and greater crown development (higher crown height and diameter and larger leaves) compared to control or eCO2-only. Plant diameter and number of leaves did not respond to any treatment. We did not find differences between +P seedlings under different CO2 treatments (aCO2+P and eCO2+P), indicating that only P had an effect on these responses. Still, there were substantial changes on some of the aboveground responses between these treatments, particularly in total leaf area which increased 60% (aCO2+P) and 126% (eCO2+P) compared to control. Overall, we observed a distinguished pattern, in which eCO2 mainly affected physiological responses, while P addition consistently affected aboveground development. The lack of response of aboveground components under eCO2 suggests that the extra carbon assimilated was not necessarily used to aboveground development as shown by many studies. Our findings indicate that, in the short-term, eCO2 is highly important in determining changes in plant metabolism whereas it has little impact on growth, even when nutrient limitation is alleviate. However there is still need to understand if such responses will persist in the long-term and in other species, as these processes are key factors in determining forest responses to climate change.  

How to cite: U. Neves, G., R. Ferrer, V., Garcia, S., F. de Souza, V., Domingues, T., Aleixo, I., Tozzi, H., A. C. L. Pequeno, P., P. Martins, N., Guedes, A., S. Pereira, I., C. G. Menezes, J., R. M. Damasceno, A., R. Santos, Y., N. Garcia, M., C. M. Moraes, A., M. Pereira, A. C., Kruijt, B., and A. N. Quesada, C. and the AmazonFACE Team: Short-term responses of Inga edulis Mart. seedlings growing under elevated CO2 and phosphorus addition: understanding potential phosphorus constraints on plant responses to elevated CO2 in the understory of a central Amazon forest    , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8975, https://doi.org/10.5194/egusphere-egu22-8975, 2022.

EGU22-9067 | Presentations | BG1.4 | Highlight

AmazonFACE – Assessing the response of Amazon rainforest functioning to rising atmospheric CO2 concentration 

Anja Rammig and David Lapola and the AmazonFACE team

The rapid rise in atmospheric CO2 concentration over the past century is unprecedented. It has unambiguously influenced Earth’s climate system and terrestrial ecosystems. Plant responses to rising atmospheric CO2 concentrations are thought to have induced an increase in biomass and thus, increased the carbon sink in forests worldwide. Rising CO2 directly stimulates photosynthesis (the so-called CO2-fertilization effect) and tends to reduce stomatal conductance, leading to enhanced water-use efficiency, which may provide an important buffering effect for plants during adverse climate conditions. For these reasons, current global climate simulations consistently predict that tropical forests will continue to sequester more carbon in aboveground biomass, while several lines of evidence point towards a decreasing carbon sink strength of the Amazon rainforest in the coming decades, potentially driven by nutrient limitation, droughts or other factors. Mechanistically modelling the effects of rising CO2 in the Amazon rainforest are hindered by a lack of direct observations from ecosystem scale CO2 experiments. To address these critical issues, we have been developing a free-air CO2 enrichment (FACE) experiment in an old-growth, highly diverse, tropical forest in the Brazilian Amazon and we present our main hypotheses that underpin the AmazonFACE experiment.  We focus on possible effects of rising CO2 on carbon uptake and allocation, phosphorus cycling, water-use and plant-herbivore interactions, and discuss relevant ecophysiological processes, which need to be implemented in dynamic vegetation models to estimate future changes of the Amazon carbon sink. We also report recent results from the open-top chamber experiments on understorey saplings under rising CO2 and phosphorus fertilization, recently conducted at the AmazonFACE site. We give an overview over phosphorus uptake strategies and potential modelling approaches.

How to cite: Rammig, A. and Lapola, D. and the AmazonFACE team: AmazonFACE – Assessing the response of Amazon rainforest functioning to rising atmospheric CO2 concentration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9067, https://doi.org/10.5194/egusphere-egu22-9067, 2022.

EGU22-10939 | Presentations | BG1.4 | Highlight

Effects of soil fertilization on aboveground biomass in an old-growth forest in Central Amazon 

Bárbara Brum, Carlos A. Quesada, Rafael Assis, Juliana Schietti, Izabela Aleixo, Raffaello di Ponzio, Iain Hartley, Kelly Andersen, Hellen F. Cunha, Laynara Lugli, Nathielly Martins, Renata Almeida, Maria Pires, Nívia Pinheiro, Anna C. Moraes, José L. Camargo, Gyovanni Ribeiro, Bruno Takeshi, Lara Siebert, and Felipe Andrade

The Amazon covers an extensive area of tropical rainforest that directly affects global water and Carbon cycles. The biomass stored in this forest is a result of the dynamic balance between rates of mass gain due to productivity, and losses due to respiration and mortality. In general, these forests concentrate about 70-80% of biomass in the aboveground part, and the regional variation of AGB (aboveground biomass) can be explained by the compositional, structural, climatic and by differences in soil propriety and fertility between East-West gradient in the Amazon basin. This gradient drives a large set of variations in tree growth and mortality, resulting in differences on the forest structure and dynamics. In this context, direct manipulation of nutrients in soils is a powerful tool to investigate which elements limit tree growth and forest productivity. While nitrogen (N) is accumulated along soil development and age, the availability of rock-derived phosphorus (P) and cations may limit the ecosystems' functioning, including the potential increase in the productivity in response to elevation on CO2 concentrations in the atmosphere. To understand these patterns, a long-term, large-scale soil fertilization experiment in Amazonian forests (AFEX) was implemented in the Central Amazon. In 2017, 32 permanent plots were installed in areas of old-growth continuous forest belonging to the Biological Dynamics of Forest Fragments Project (PDBFF), in a full factorial design, with four blocks chosen at random, where 8 plots (each with a size of 50x50 m) were installed with different fertilization treatments for each block. The treatments are: P, N, cations, Control (no fertilization), N+P, N+cations, P+cations and N+P+cations. To estimate the effects of soil fertilization on AGB, we calculated the difference between biomass before and after four years of fertilization (2017 to 2021), using allometric equations performed data from diameter about 5,000 individuals (DAB ≥ 10 cm) measured annually and wood density. We analyzed the data with two different approaches, at the community and at genus level, considering three most abundant genera: Eschweilera, Pouteria and Protium. At community level, our results showed only non-significant trends between AGB in plots where N, P and cations were added. At genus level, we observed that Eschweilera and Protium had a negative relationship to N and Pouteria had a positive trend.  Conversely, only Protium increased AGB with P addition.  Pouteria and Protium was negatively affected by cations, while Eschweilera showed no response. These results indicate that, although overall positive or negative trends in biomass increment appear at the community level, the highly diverse forest studied does not have a homogeneous response to nutrient addition, and that each taxonomic group could potentially be limited by different nutrients. In the long term, we expect that these patterns may change the forest structure, dynamics and composition and, consequently, the stocks of biomass, impacting the functionality of these forests. These results improve our understanding of the role of nutrients affecting forest biomass, and may reduce uncertainties in vegetation dynamics models and predictions on environmental changes.

How to cite: Brum, B., Quesada, C. A., Assis, R., Schietti, J., Aleixo, I., di Ponzio, R., Hartley, I., Andersen, K., Cunha, H. F., Lugli, L., Martins, N., Almeida, R., Pires, M., Pinheiro, N., Moraes, A. C., Camargo, J. L., Ribeiro, G., Takeshi, B., Siebert, L., and Andrade, F.: Effects of soil fertilization on aboveground biomass in an old-growth forest in Central Amazon, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10939, https://doi.org/10.5194/egusphere-egu22-10939, 2022.

EGU22-11505 | Presentations | BG1.4

Extreme droughts and floods in the Amazon forest 

Gerbrand Koren, Santiago Botía, Lucas G. Domingues, Liesbeth Florentie, Luciana V. Gatti, Manuel Gloor, Shaun Harrigan, Maarten C. Krol, Ingrid T. Luijkx, John B. Miller, Stijn Naus, and Wouter Peters

In recent years, the Amazon forest has experienced several major droughts (2010, 2015/16) and floods (2012, 2014, 2021). Extreme events represent a threat to the Amazons important functions, but these perturbations also provide valuable insights into the underlying mechanisms. Here we studied the most recent massive drought and flood events in detail, and quantified their severity and spatiotemporal extent relative to a multi-year baseline.

First, we describe the anomalous hydrological status of these events, by bringing together a large variety of data sets, including in-situ observations and reanalysis products for precipitation, discharge, vapor pressure deficit and soil moisture. During the strong El Niño conditions following the dry season of 2015, the precipitation fell below its climatological values. This was soon reflected in low discharge rates and soil moisture levels, persisting far into the year 2016 for some regions. In contrast, we find anomalously high precipitation over the northern Amazon during the first months of 2021, resulting in high discharge rates,  and  rising river levels that have led to massive floods in downstream regions.

Finally, we quantified the impact of the 2015/16 drought on vegetation using the inverse model CarbonTacker South America (CT-SAM) and remote sensing proxies for photosynthesis. To address the uncertainty in prior emission estimates, we have used a range of different biosphere models (SiBCASA, SiB4), including a biosphere model linked to a detailed hydrological model (PCR-GLOBWB). For the fire flux we used multiple data sets (GFAS, SiBCASA-GFED4), including a modified version based on CO inversions performed with the TM5-4DVAR system. We find that photosynthesis was reduced during the 2015 drought, especially in the drier, southern part of the Amazon. This was followed by a recovery in the first months of 2016, but during the subsequent dry season a secondary impact on photosynthesis was found. The inversely derived net CO2 fluxes do not have the same high resolution as the satellite products, but when assessed over larger scales, a consistent drought signal is derived.

How to cite: Koren, G., Botía, S., Domingues, L. G., Florentie, L., Gatti, L. V., Gloor, M., Harrigan, S., Krol, M. C., Luijkx, I. T., Miller, J. B., Naus, S., and Peters, W.: Extreme droughts and floods in the Amazon forest, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11505, https://doi.org/10.5194/egusphere-egu22-11505, 2022.

EGU22-11693 | Presentations | BG1.4

Tropical forest CH4 budget: the importance of local hotspots 

Hella van Asperen, Thorsten Warneke, Alessandro De Araújo, Bruce Forsberg, Sávio Ferreira, João Alves-Oliveira, Leonardo Ramos de Oliveira, Thiago de Lima Xavier, Marta Sá, Paulo Teixeira, Elaine Pires, Veber Moura, Shujiro Komiya, Santiago Botia, Sam Jones, Jost Lavrič, Susan Trumbore, and Justus Notholt

Methane (CH4) is one of the most important anthropogenic greenhouse gases. Despite its importance, natural sources of methane, such as tropical wetlands and termites, are still not well understood and a large source of uncertainty in the tropical CH4 budget. The Amazon rainforest is a key region for the (global) CH4 budget but, due to its remote location, local CH4 concentration and flux measurements are still rare.

Fieldsite ZF2 (60 km NW of Manaus, Brazil) is located in pristine tropical rain forest. At this fieldsite, a Spectronus FTIR-analyzer (measuring CO2, CO, CH4, N2O & δ13CO2) was installed at the foot of the K34 tower, set up to measure different heights above and below the canopy continuously. In addition, by use of a Los Gatos portable analyzer (measuring CO2 & CH4), additional semi-continuous concentration measurements were performed at the valley tower (studying the nighttime build up of valley CH4), above the igarapé  (capturing the CH4 ebullition bubbles leaving the water surface), and on the plateau (studying the spatial horizontal heterogeneity of CH4 concentrations within the canopy). Furthermore, the portable analyzer was used for soil, water, termite mound, and termites flux measurements.

By combining tower and flux chamber measurements, the role and magnitude of different ecosystem sources could be assessed. We observed that, while soils in the valley are a small source of CH4 (0.1 to 0.2 nmol CH4 m-2 s-1), overall the soils of this ecosystem are expected to be a net CH4 sink (-0.3 to -0.5 nmol m-2 s-1 ). Estimated total ecosystem CH4 flux, based on nighttime concentration analyses of the tower data, indicate that the ecosystem is a net CH4 source (~1 to 2 nmol CH4 m-2 s-1). We propose that the net CH4 emission of the ecosystem is driven by local emitting hotspots, such as the valley stream and standing water, termites and termite mounds (~1 nmol CH4 m-2 s-1), anoxic soil spots and decaying dead wood.

 

How to cite: van Asperen, H., Warneke, T., De Araújo, A., Forsberg, B., Ferreira, S., Alves-Oliveira, J., Ramos de Oliveira, L., de Lima Xavier, T., Sá, M., Teixeira, P., Pires, E., Moura, V., Komiya, S., Botia, S., Jones, S., Lavrič, J., Trumbore, S., and Notholt, J.: Tropical forest CH4 budget: the importance of local hotspots, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11693, https://doi.org/10.5194/egusphere-egu22-11693, 2022.

EGU22-12016 | Presentations | BG1.4 | Highlight

Assessing social and ecological drivers of fire regimes in the Brazilian Amazon in the context of changing forest governance 

Michel Valette, Morena Mills, Jem Woods, Yiannis Kountouris, and Minerva Singh

Whilst the deforestation rate of the Brazilian Amazon has decreased drastically over the 2005-2015 period, thanks to an ambitious program to fight deforestation, since then, forest degradation resulting from logging and wildfires became the major source of aboveground biomass losses and the Brazilian Amazon turned into a net carbon source. This could be partially explained by a decoupling of fire occurrence and deforestation, historically one of the key drivers of the fire regime in the region. Moreover, since 2015, deforestation rates and associated fires are rising again, and new deforestation frontiers are opening in previously unaffected areas in the central and western Amazon.

Fires in the Brazilian Amazon are closely related to climate and agriculture: fires are used to transform forests into pastures or cropland, and subsequent burns are used to maintain grass productivity. When nearby rainforests are sufficiently dry, deforestation and agricultural fires escape and can cause large wildfires. Local communities’ fire management practices impact greatly the likelihood of these escaping fires, but also bear a cost. High mortality rates after even low-intensity fires lead to fuel accumulation and canopy damage, increasing the vulnerability of forests to subsequent burnings. Coupled with a regional reduction of precipitations due to climate change and deforestation, the Amazon forest could be threatened by a cycle of massive dieback and increased fire activity. Thus, it is crucial to understand the drivers of different types of fires in the region and how to prevent them. Of particular interest is the role played by the policies deployed after 2004 to reduce deforestation rates in the region and their recent weakening.

Building on previously published literature on the drivers of fire regimes and deforestation in the region, data were collected on potential drivers of fire regimes related to climate, agricultural expansion, ecosystem integrity, infrastructure, populations, environmental policies and land conflict. MODIS Active-Fire dataset was used as a response variable, and also classified into deforestation fires, agricultural fires and forest fires thanks to deforestation and land use data in a second step of the study. A spatiotemporal modelling approach, relying on the Log Gaussian Cox process and R-INLA package, has been adopted to assess the relative influence of different drivers of fire regimes in the Brazilian Amazon for the 2006-2020 period. Preliminary results on the drivers of fire regime in the state of Para for the last four years show a powerful influence of drivers related to agricultural expansion (especially ranching), integrity of the forest cover, presence of rural settlements and environmental policies. Different protection regimes have varying influences on the fire regime, with sustainable use areas being the less efficient. Law enforcement efforts seem to have an inhibitory effect on fire occurrence and protected area downgrading, downsizing and degazettement favour them.

How to cite: Valette, M., Mills, M., Woods, J., Kountouris, Y., and Singh, M.: Assessing social and ecological drivers of fire regimes in the Brazilian Amazon in the context of changing forest governance, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12016, https://doi.org/10.5194/egusphere-egu22-12016, 2022.

EGU22-13294 | Presentations | BG1.4

Ecosystem nutrient budget in a Central Amazon forest: the role of nutrient stocks and flows in biogeochemical cycling 

Pâmella Assis, Laynara F. Lugli, Izabela Aleixo, Luciana R. Bachega, Sabrina Garcia, Flavia Santana, and Carlos A. Quesada

Soils of tropical forests generally have low fertility, therefore nutrient cycling has great importance in these ecosystem functions, once these soil elements are essential for vegetative tissue and plant metabolic processes. Understanding and quantifying the processes that involve nutrient acquisition, storage, and output in plants, and their relationship with forest productivity and biomass, is essential to characterize the ecosystem nutrient dynamics and understand how global environmental changes, such as the increase in CO2 can affect forest processes. Therefore, we investigated the nutrient dynamics of a terra firme forest in Central Amazonia, near Manaus, Brazil through the quantification of stocks, flows, and nutrient use efficiency in different compartments to estimate forest nutritional balance. We quantified the biomass stocks in the forest compartments – fine root, leaves, litterfall and stems – and their macro (N, P, Ca, Mg e K) and micronutrients (Fe, Mn e Zn) content. We estimated the nutrient fluxes through productivity rates, the nutrient stocks, and the nutrient efficiency, the inverse of nutrients concentration. Most of this information was available from the AmazonFACE (Free-Air CO2 Enrichment) baseline data. The study area has 8 permanent plots monitored since 2015 with periodic field collections and monitoring. We hypothesized that the macronutrient that cycles more efficiently in the ecosystem will potentially be the most limiting element to forest net primary productivity, adding to a better understanding of nutrient allocation and cycling, and greater accuracy in predictions from global vegetation dynamics models. The total forest biomass (above and belowground) in our study site was 200.85±0.52 Mg C ha-1 and the productivity 9.79±0.22 Mg C ha year-1. These results are higher than previous studies reported in the amazon forest. Ecosystem nutrient flow was greater in leaves > litter standing crop > fine roots > stems. On the other hand, ecosystem nutrient stocks were greater in stems > leaves > fine root > litter standing crop.  Our preliminary results show that phosphorus stock and flow are lower than other macronutrients, being, therefore, cycled more efficiently than other elements studied here. This suggests that phosphorus is potentially the macronutrient that most limits net primary productivity. For nitrogen, we observe a low-efficiency use, which was expected since this element is abundant in Central Amazon soils;  for potassium an intermediate efficient use, so the order of stocks and flows is N > K > P. For micronutrients nutrient efficiency use was as follows: zinc > magnesium > iron. These results suggest that phosphorus could be considered the most limiting macro nutrient to forest net primary productivity while zinc availability could also play a role. Our estimates of nutrient stocks and flows for a Central Amazon forest would improve our understand different nutrient dynamics and demands that impact biogeochemical cycles and functioning of these forests.

How to cite: Assis, P., Lugli, L. F., Aleixo, I., R. Bachega, L., Garcia, S., Santana, F., and Quesada, C. A.: Ecosystem nutrient budget in a Central Amazon forest: the role of nutrient stocks and flows in biogeochemical cycling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13294, https://doi.org/10.5194/egusphere-egu22-13294, 2022.

EGU22-13341 | Presentations | BG1.4

How does leaf phenology define upper canopy functional structure in a central Amazon upland forest? 

Pedro Ivo Lembo Silveira de Assis, Giordane A. Martins, Izabella Sanches, Bruce W. Nelson, Marta Sá, Jurgen Kesselmeier, and Antonio O. Manzi

Leaf phenology impacts carbon, nutrient, and hydrological cycles from local to global scales. In central Amazon rainforest, the timing of leaf flush and abscission promotes a seasonal change in leaf age composition of the upper canopy. It has been singled out as the most important driver of photosynthetic capacity (PC) seasonality. However, limitations concerning on two important issues must be raised: 1) canopy leaf age temporal variation has not been directly assessed and 2) this approach has an empirical assumption that canopy leaf area should be fully replaced after 12 months. The first issue implies PC to be obtained by flux-towers measurements to estimate leaf age composition of the upper canopy. So, it is not a reliable representation of age distribution of the upper canopy. The concerning about the second issue relies on that tropical rainforest trees are known to present different leaf phenological patterns (e.g. deciduousness and evergreenness) which are correlated to leaf lifespan (LL), like for a year or more. Besides, leaves presenting higher LL show differences on PC compared to those of short ones, both in their maximum PC and its decay rate while aging. That means if leaves from plants with different leaf phenological pattern have the same age (e.g. in months), they will differ on their PC. Therefore, there is a necessity to elucidate leaf phenological patterns and unravel temporal changes on leaf age composition of upper canopy and LL variability. From August 2016 to November 2019 at the Amazon Tall Tower Observatory (ATTO), tagged leaves were censused monthly on ten upper canopy branches per tree (n = 36 trees). Temporal variation of storage, flush and abscission of leaves were recorded. Chronological ages were only possible for leaves flushing during the study period. Similarly, LL was obtained from leaves when both flush and abscission date were observed throughout the monitoring period. Around 80% of the trees flushed new leaves massively during the dry season. Eight of them (22%) fell into brevi-deciduous category while twenty-eight (78%) into evergreenness. Canopy leaf quantity proved to be nonseasonal as expected. On the other hand, seasonal change in leaf age composition of the upper canopy was confirmed. Still, it sheds light on its complex and diverse stratification. In the last month of monitoring, leaf age ranged from 0 to 43 months with only half of the leaves being younger than a year. Thus, leaf flush and leaf abscission present a seasonality. However, at least almost half of them have a lifetime longer than a year. This result suggests that half of the leaves from upper canopy are being neglected by the models. The LL presented a bimodal distribution (n = 2552 leaves) with two peaks around one year and two years, respectively. This suggest there are annual and biannual leaf phenological patterns between upper canopy trees. However, individual trees still show a bimodal distribution of LL frequency. This implies LL should not be used as a leaf functional trait to define plant functional groups.

How to cite: Lembo Silveira de Assis, P. I., Martins, G. A., Sanches, I., Nelson, B. W., Sá, M., Kesselmeier, J., and Manzi, A. O.: How does leaf phenology define upper canopy functional structure in a central Amazon upland forest?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13341, https://doi.org/10.5194/egusphere-egu22-13341, 2022.

EGU22-183 | Presentations | BG1.6

Disentangling the overlapping zonation of dissimilatory iron and sulfate reduction in a carbonate-buffered sulfate-rich and ferruginous lake water column 

Daniel A. Petrash, Ingrid M. Steenbergen, Astolfo Valero, Travis B. Meador, Stefan V. Lalonde, and Christophe Thomazo

In the oligotrophic bottom waters of a post-mining lake (Lake Medard, Czechia), ferruginous conditions occur without quantitative sulfate depletion. The dissolved organic matter supply to the deep waters is small and, accordingly, sulfate reduction promoting precipitation of stable ferrous sulfides is limited. In line with these observations, an isotopically constrained estimate of the rates of planktonic sulfate reduction (SRR) suggests that despite a high genetic potential—as determined by genome analyses, SRR are limited by substrate competition exerted by nitrogen and iron respiring prokaryotes. The microbial succession across the nitrogenous and ferruginous zones of the bottom water column also indicates a sustained genetic potential for chemolithotrophic sulfur oxidation, probably accompanied by disproportionation of S intermediates[1].

The bottom waters displayed dissolved Fe concentrations (~0.1 to 33 µM) and δ56Fe values (-1.77 ± 0.03 ‰ to +0.12 ± 0.05 ‰) that increase across the redoxcline and towards the anoxic sediment-water interface (SWI). These parameters pinpoint diffusive transport and partial oxidation of dissolved ferrous iron (Fe(II)) sourced from the lakebed, depletion of the residual Fe(II) in heavy isotopes at the redoxcline and enrichment near the SWI linked to monosulfide precipitation. In the carbonate-buffered lake sediments, however, sulfur re-oxidation appears to prevent substantial stabilization of iron monosulfides as pyrite, but it enables the interstitial precipitation of small proportions of equant microcrystalline gypsum. This gypsum isotopically fingerprints sulfur oxidation proceeding at near equilibrium with the ambient anoxic waters, whilst authigenic pyrite-sulfur displays a 38 to 27 ‰ isotopic offset from ambient sulfate, suggestive of incomplete sulfate reduction and indicative of the openness of the system[1].

Overall, our results demonstrate that under transitional redox states producing the meromictic stability described here, the simple biogeochemical zonation models based on energetic considerations of pure phases at standard conditions may not accurately describe the overlapping zonation of dissimilatory iron and sulfur reduction. Vigorous sulfur and iron co-recycling in the water column can be fuelled by ferric and manganic particulate matter and notably by the redeposited siderite stocks of the upper anoxic sediments. In the absence of ferruginous coastal zones today, the current water column redox stratification in the post-mining Lake Medard has scientific value for (i) testing emerging hypotheses on how a few interlinked biogeochemical cycles operated in low productivity nearshore paleoenvironments during transitional states between ferruginous and euxinic conditions; and (ii) to acquire insight on potential avenues for early diagenetic overprinting of redox proxy signals in ferruginous-type sediments.

[1] Petrash, D. A., Steenbergen, I. M., Valero, A., Meador, T. B., Pačes, T., and Thomazo, C.: Aqueous system-level processes and prokaryote assemblages in the ferruginous and sulfate-rich bottom waters of a post-mining lake, Biogeosciences Discuss. [preprint], https://doi.org/10.5194/bg-2021-253, in review, 2021.

How to cite: Petrash, D. A., Steenbergen, I. M., Valero, A., Meador, T. B., Lalonde, S. V., and Thomazo, C.: Disentangling the overlapping zonation of dissimilatory iron and sulfate reduction in a carbonate-buffered sulfate-rich and ferruginous lake water column, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-183, https://doi.org/10.5194/egusphere-egu22-183, 2022.

EGU22-680 | Presentations | BG1.6

Iron rich glauconite sand as an efficient phosphate immobilising agent in river sediments 

Lei Xia, Mieke Verbeeck, Yaana Bruneel, and Erik Smolders

The reductive dissolution of iron (Fe) (oxy)hydroxides in sediments releases phosphorus (P) to the overlying water and may lead to eutrophication. Glauconite sands (GS) are rich in Fe and may be used as readily available P sorbents. This study was set up to test effects of dose and type of GS on the P immobilisation in sediments under hypoxic conditions. Three different GS were amended to a P-rich river sediment at doses of 0% (control), 5% and 10% (weight fractions) and incubated with overlying water in batch laboratory conditions. Glutamate was added to the solution after 15 days to deplete any residual dissolved oxygen from the sediment-water interface. In the first 15 days, the P concentration in the overlying water peaked to 1.5 mg P L-1 at day 9 in the control and decreased to 0.9 mg P L-1 at lowest Fe-dose and to 0.03 mg P L-1 at the highest Fe-dose, the effects of GS type and dose were explained by the Fe dose. After 15 days, the added glutamate induced a second, and larger peak of P in the overlying water in sediment, that peak was lower in amended sediments but no GS dose or type related effects were found. This suggests that freshly precipitated P species at the sediment-water interface can be remobilised. This study highlights the potential for using this natural mineral as a cheap and easily available sediment remediation material, but its longevity under rare extreme conditions needs to be further investigated.

How to cite: Xia, L., Verbeeck, M., Bruneel, Y., and Smolders, E.: Iron rich glauconite sand as an efficient phosphate immobilising agent in river sediments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-680, https://doi.org/10.5194/egusphere-egu22-680, 2022.

EGU22-2654 | Presentations | BG1.6

Rhenium geochemistry in hypoxic and euxinic marine lakes of the Eastern Adriatic Sea 

Igor Zivkovic, Lucija Knezevic, Dario Omanovic, Marta Jagodic Hudobivnik, Leja Rovan, and Elvira Bura Nakic

Rhenium (Re) is known as one of the rarest elements at Earth’s surface. Re enrichment in sediments deposited beneath anoxic and sulfidic water columns can be few orders of magnitude greater in comparison to the average crustal concentration of Re. The exact mechanism of Re transformation and transport from dissolved phase in oxic environments to anoxic sediments is still poorly understood. The hypothesis of Re enrichment involves the reduction of perrhenate to an insoluble Re(IV) product within the sediment-water interface or progressive thiolation of perrhenate anion that leads to the formation of particle-reactive thioperrhenates. Like molybdenum (Mo) and uranium (U), the analysis of vanadium (V) and Re enrichment covariations within anoxic sediments may also be potentially used as an important paleoredox tool. To broaden our understanding of Re geochemistry in hypoxic and euxinic marine lakes, we have performed sampling of seawater and sediments in two marine lakes in the Eastern Adriatic Sea (Small Lake on the Island of Mljet and Dragon Eye Lake near the town of Rogoznica). Samples were collected in April 2020 and November 2020 at the Small Lake, while those in the Dragon Eye were collected in July 2020. Seawater profiles were collected from the surface to near-bottom layer. Sediments were sampled using core-sampler and cut in 2-cm layers under nitrogen atmosphere. Porewater was separated from the sediment by centrifugation and filtered under nitrogen atmosphere. Re in sediments was determined using ID-ICP-MS following acid digestion, matrix substitution, and preconcentration on Dowex resin. Re in seawater and porewater was determined using ID-ICP-MS after preconcentration on Dowex resin. Multi-elemental analyses in waters and sediments were also performed to obtain insights into Re behavior in these compartments. The first results for the Small Lake (April sampling) showed that Re concentration in seawater is rather uniform (about 8 ng/L). Further on, Re concentrations in sediments were increasing with depth (from 3.5 to 9.7 ng/g), while the corresponding Re concentrations in porewater were decreasing (from 4.6 to 1.8 ng/L). Principal component analyses showed different behavior of Re in porewaters and sediments when compared to other redox sensitive elements. In sediments, Re was highly correlated with Mo and U, and usually without correlations with Mn or Fe. On the contrary, Re in porewaters was highly correlated to Mn and Fe, and negatively correlated with Mo and U. Regarding correlations between Re in V: in cores in which Re was negatively correlated with V in porewater, there were no significant correlations in sediments, and vice versa. Re in porewaters did not show correlations with sulfide. These first results indicate different geochemistry of Re in hypoxic and euxinic marine lakes when compared to Mo, U, and V. The appropriate data analysis will be evaluated following the analysis of other samples.

How to cite: Zivkovic, I., Knezevic, L., Omanovic, D., Jagodic Hudobivnik, M., Rovan, L., and Bura Nakic, E.: Rhenium geochemistry in hypoxic and euxinic marine lakes of the Eastern Adriatic Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2654, https://doi.org/10.5194/egusphere-egu22-2654, 2022.

EGU22-6209 | Presentations | BG1.6

Stability of Al-substituted jarosite in the presence of Fe(II) 

Andrew Grigg, Luiza Notini, Ralf Kaegi, Laurel ThomasArrigo, and Ruben Kretzschmar

Jarosite is a ferric iron sulfate mineral [(KFe3(SO4)2(OH)6] that is commonly formed in acidic environments that are rich in iron and sulfate, such as acid-sulfate soils or acid mine drainage. The stability of jarosite is important because the mineral contains embodied acidity and may scavenge trace elements by sorption and co-precipitation. Although stable under high Eh and low pH conditions, previous studies have shown that jarosite is prone to transformation by hydrolysis at circumneutral pH, or may undergo Fe(II)-catalysed transformation where ferrous ions are present [1-3]. Jarosite may be exposed to Fe(II) at circumneutral pH in reducing environments, such as in flooded acid-sulfate soils [2]. Jarosite is a member of the alunite supergroup and forms a solid solution series with alunite by substitution of Al for Fe. However, the effect of Al substitution on the stability of jarosite in the presence of Fe(II) has not previously been investigated. Here, we performed batch experiments using samples of a synthetic jarosite without aluminium substitution, and synthetic jarosite containing 7.3% Al-for-Fe substitution. Mineral samples were reacted with 0.5 mM and 5 mM Fe(II) at pH 7.1 (50 mM MOPS buffer) for up to 24 hours. Rietveld analysis of X-ray diffraction patterns was used to quantify mineral transformations and to determine the crystallinity of, and Al substitution in, product phases. Complete transformation of jarosite to mixtures of ferrihydrite, goethite and lepidocrocite occurred within several hours for all jarosite samples and Fe(II) treatments. The 10-fold increase in Fe(II) concentration resulted in a 50% increase in jarosite transformation rate, and pure jarosite transformed 110% to 280% faster than Al-substituted jarosite. The transformation products of Al-substituted jarosite contained a smaller proportion of lepidocrocite than the products of pure jarosite transformation, and the unit cell size of the lepidocrocite that initially formed from Al-substituted jarosite indicates that Al was substituted into the structure. These results demonstrate that structural Al can stabilise jarosite against transformation, which has implications for understanding the longevity of jarosite, and its importance to trace element cycling, in reducing environments.

1. Welch, S. A., et al. (2008) Chem. Geol. 254: pp. 73-86
2. Karimian, N., et al. (2017) Environ. Sci. Technol. 51: pp. 4259-4268
3. Whitworth, A. J., et al. (2020) Chem. Geol. 554 

How to cite: Grigg, A., Notini, L., Kaegi, R., ThomasArrigo, L., and Kretzschmar, R.: Stability of Al-substituted jarosite in the presence of Fe(II), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6209, https://doi.org/10.5194/egusphere-egu22-6209, 2022.

EGU22-9099 | Presentations | BG1.6

Preliminary studies on V(III) determination in the form of picnolate complex using HR ICP-MS 

Lucija Knežević, Jelena Mandić, Igor Živković, Dario Omanović, and Elvira Bura Nakić

In the environment vanadium(V) is found in three oxidation states (III, IV and V) depending on physicho-chemical conditions (pH, Eh, ionic strength, its concentration, biology, organic matter content ect.) of certain environmental medium [1]. Knowledge of V species distribution is to this date very scarce due to its complex aquatic chemistry as well as modern analytical intrumentation constraints [2,3]. Especially, methods on accurate V(III) species determination in complex environmental matrices are poorly developed which makes estimation of V biogeochemical cycle uncomplete. It is known that V(III) is expected to be stable in strongly anoxic or euxinic conditions, such as sulphide-containing water samples or sediments. Furthermore, high affinity towards adsorption on various colloids found in natural aquatic systems as well as formation of strong complexes with various organic ligands is presumed. Possible formation of V(III) in certain aquatic environments can contribute to removal of V into sediments [2]. Therefore, determination of V(III) in natural environmental samples is highly needed for accurate estimation of V bioavailability, mobility and toxicitiy.

Method developed by Yatirajam et al. (1979) was used in order to establish V(III) stability in various model solutions [4]. Procedure is based on the formation of selective complexes of V(III) and picnolic acid in respect to V(IV) and V(V) species present in samples. Upon complexation, V(III) species are then extracted into chloroform. Extracts were evaporated to dryness and the remaining content was dissolved in 2% HNO3. Samples were then measured using HR ICP-MS analytical intrumentation. For measurements using spectrophotometry, samples were measured immidiately upon extraction. Studies so far show good selectivity, reproducibility and accuracy which offers a promising method for V(III) determination in natural samples. Stated findings are planned to be further applied on natural anoxic sediment samples of Mljet and Rogoznica lakes (Croatia).

Literature:

  • Huang, J.H.; Huang, F.; Evans, L.; Glasauer, S. Vanadium: Global (bio)geochemistry. Chem. Geol. 2015, 417, 68–89, doi:10.1016/j.chemgeo.2015.09.019.
  • Gustafsson, J.P. Vanadium geochemistry in the biogeosphere –speciation, solid-solution interactions, and ecotoxicity. Appl. Geochemistry 2019, 102, 1–25, doi:10.1016/j.apgeochem.2018.12.027.
  • Costa Pessoa, J. Thirty years through vanadium chemistry. J. Inorg. Biochem. 2015, 147, 4–24, doi:10.1016/j.jinorgbio.2015.03.004.
  • Yatirajam. V, Arya, S.P. EXTRACTION DETERMINATION AS VANADIUM ( II1 ) OF VANADIUM. Talanta 1978, 26, 60.

How to cite: Knežević, L., Mandić, J., Živković, I., Omanović, D., and Bura Nakić, E.: Preliminary studies on V(III) determination in the form of picnolate complex using HR ICP-MS, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9099, https://doi.org/10.5194/egusphere-egu22-9099, 2022.

EGU22-9462 | Presentations | BG1.6 | Highlight

Who controls Fe cycling below the SMTZ of the Mediterranean Sea? 

Alice Bosco Santos and Orit Sivan

Microbial metabolisms that attain close together different biogeochemical cycles, such as Fe, C, and N, introduce complexity to the traditional redox electron acceptors cascade in sediments, leading to spatial overlap between geochemical gradients. A good example of overlap when considering Fe geochemistry is the oftentimes peaks in dissolved Fe2+ observed below the sulfur-methane transitional zone (SMTZ) in different environments. While anaerobic methane oxidation mediated by Fe reduction (Fe-AOM) might explain the feature in deep lacustrine sediments, our preliminary data indicate that Fe-AOM is not significant in oligotrophic marine sediments. We described Fe speciation, nutrients, and microbiota composition in various sedimentary profiles from the Levantine Basin, Eastern Mediterranean Sea, Israel and observed coupled Fe and N cycling. In the ammonium-rich (2000 µmol L-1) deep methanic sediments, strongly positive correlated increases in dissolved Fe2+ and NO2- (and/or NO3-) via microbe-mediated ammonium oxidation coupled to Fe(III) reduction (Feammox) is proposed. In this environment, the deep availability of Fe2+ favors precipitation of authigenic Fe minerals below the SMTZ.

How to cite: Bosco Santos, A. and Sivan, O.: Who controls Fe cycling below the SMTZ of the Mediterranean Sea?, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9462, https://doi.org/10.5194/egusphere-egu22-9462, 2022.

EGU22-9601 | Presentations | BG1.6 | Highlight

Seafloor iron mobilization across the deep-water redox gradients of the Black Sea and the Sea of Marmara 

Nimet Alımlı and Mustafa Yücel

Iron is one of the most important redox-sensitive elements in marine systems. A better understanding of the marine iron cycle is urgently needed for many scientific questions, including the evolution of ancient co-factors under changing redox conditions, marine primary production, and global climate change. Given the scarcity of iron in oceans, the interplay between different iron pools in various redox settings is analytically challenging and poorly understood. In this study, we report on new downcore profiles of pore water iron species along with their size distributions across the oxic, suboxic, and sulfidic regions of the Black Sea and in the recently deoxygenated areas of the Sea of Marmara. The vertical distribution of dissolved iron (<0.45 µm) in sediment pore water showed strong subsurface iron peaks reaching maximum concentrations around 87 µM in the Sea of Marmara, resulting in high benthic iron fluxes and indicating high rates of bacterial iron mineral respiration under hypoxia. In the Black Sea, highly sulfidic sediment conditions appeared to limit dissolved iron mobility, with iron concentrations in pore water ranging from 0.3 to 0.05 µM.  We also performed additional experiments at selected sites to understand the nature of the colloidal fraction. Size fractions were obtained by sequential filtering and filtered samples were analyzed by the spectrometric ferrozine method. To achieve the low detection limits required for the water column samples, the spectrometer was used in conjunction with a 50cm liquid waveguide capillary cell, allowing rapid on-board detection of iron at nanomolar levels. The partitioning between soluble (<0.02 µm) and colloidal (0.02-0.2 µm) iron pools in the pore water showed that the dissolved iron was mainly dominated by the soluble fraction, while colloidal fraction behaved differently. The results suggest that the colloidal fraction may be more dependent on other biogeochemical characteristics of the environment in addition to redox conditions. We also applied to colloidal fraction a revised sequential acid leaching scheme originally developed for hydrothermal iron fractions. Preliminary results suggest that the characteristics of the colloidal iron pool in the pore waters of the Sea of Marmara and Black Sea sediments differ from the nanomineral-dominated vent iron, and that organic fractions may play a greater role in mobilizing iron colloids from sediments of deoxygenated basins.  

How to cite: Alımlı, N. and Yücel, M.: Seafloor iron mobilization across the deep-water redox gradients of the Black Sea and the Sea of Marmara, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9601, https://doi.org/10.5194/egusphere-egu22-9601, 2022.

EGU22-10643 | Presentations | BG1.6

Dissimilatory nitrate reduction to ammonium by benthic microbial mats fuels rapid sulfur oxidation and sediment ferrous iron release in the anoxic Santa Barbara Basin 

David Yousavich, De'Marcus Robinson, Sebastian J. E. Krause, Jonathon Tarn, Na Liu, Felix Janssen, Frank Wenzhoefer, David L. Valentine, and Tina Treude

Sulfate reduction, a crucial metabolic pathway for organic matter remineralization in marine sediments, produces hydrogen sulfide that can be subsequently utilized by chemoautotrophic organisms. When the water column above marine sediments becomes anoxic, microbial metabolisms at the sediment-water interface shift to take advantage of the electron donors and acceptors available in the new redox conditions. These processes were examined In November 2019 during the AT42-19 expedition aboard RV Atlantis. Samples were collected using ROV Jason at different depths along a transect traversing the Santa Barbara Basin between 440 and 600 m depth. Deeper parts of the basin experience transient deoxygenation that is sometimes associated with a nitrate-depleted zone. Under these conditions, large benthic microbial mats of sulfur-oxidizing bacteria form in the basin. To analyze the effect of these mats on the basin geochemistry, sulfur and nitrogen (SO42-, H2S, NO3-, NO2-, NH4+) consumption and production were examined using sediment push cores and benthic flux chambers. Other redox sensitive compounds (e.g. Fe and PO43-) were also measured using these methods. Areal sulfate reduction rates measured in push cores using the 35S-Sulfate radiotracer method were highest in the deepest, anoxic part of the basin (~4 mmol m-2 d-1) where microbial mats were most prevalent and the sediment-water interface was anoxic and low in nitrate (7.3 µM). Sulfate reduction was noticeably lower at shallow stations (~2 mmol m-2 d-1) with oxygenated water, signs of bioturbation, and without mats. Sulfate reduction below the sediment-water interface (0-1 cm sediment depth) was also an order of magnitude higher at deep stations (~120 nmol cm-3 d-1) compared to shallow stations (~18 nmol cm-3 d-1). Despite high sulfate reduction activity in areas covered by mats, sulfide concentrations were near-zero in the uppermost 2 cm of sediment. Nitrate flux into the sediment and ammonium flux out of the sediment was highest where mats were present (-2.93 mmol m-2 d-1 and 11.19 mmol m-2 d-1 respectively). Additionally, the anoxic depocenter of the basin contains a flux of ferrous iron (4.10 mmol m-2 d-1) and phosphate (3.18 mmol m-2 d-1) out of the sediment into the water column. Our results provide a direct comparison of redox cycling at the sediment-water interface under vastly different redox conditions within the same oceanic basin. These results also provide strong evidence that chemoautotrophic sulfur-oxidizing bacteria in sediments of the anoxic Santa Barbara Basin perform dissimilatory nitrate reduction to ammonium and are responsible for rapid sulfur cycling near the sediment-water interface with a concurrent flux of ammonium, iron, and phosphate into the water column.

How to cite: Yousavich, D., Robinson, D., Krause, S. J. E., Tarn, J., Liu, N., Janssen, F., Wenzhoefer, F., Valentine, D. L., and Treude, T.: Dissimilatory nitrate reduction to ammonium by benthic microbial mats fuels rapid sulfur oxidation and sediment ferrous iron release in the anoxic Santa Barbara Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10643, https://doi.org/10.5194/egusphere-egu22-10643, 2022.

EGU22-12143 | Presentations | BG1.6 | Highlight

Vertical distribution and aerobic degradation at the sediment-water interface in two urbans estuaries in Normandy, France 

Amonda El Houssainy, Isabelle Poirier, Martine Bertrand, Laure Verdier, and Florian Cesbron

In the current context of climate change, the coastal area is exposed to an increasing pressure from hydrodynamic agents such as tide, flood and storm (Parry et al., 2007) and to enormous anthropogenic activities due to urbanization and industrialization of the coastline, which weakens the coastal ecosystem. In France, the Manche department presents more than a half of the Normandy coastline (330 km) and a great diversity of its shores. It is a key player in the preservation of the coastal environment. Among its conservation areas, two estuaries in Saint-Vaast-La-Hougue interested us: the Saire Estuary and Cul-de-Loup Bay, which both subjects to the impact of human activities (agriculture, shellfish farming, tourism, modification of the coastline, etc.). In order to quantify the chemical and biological exchanges in the mudflat of these two sites, we performed dissolved oxygen profiles in the sediment using a benthic microprofiler system (Unisense®). Moreover, sediment cores were collected and sliced under inert atmosphere, in order to measure diagenetic tracers (NH4+, PO43-, Fe2+ and ΣHS-) and trace metals levels, and to identify bacterial communities. The results of sediment cores and oxygen microprofiles taken from each of the mudflat indicate a greater dynamic degradation of organic matter in the superficial sediments of Saire estuary and in deep sediment of Cul-de-Loup Bay. The benthic microprofiler results show that oxygen penetration depth is around 1 mm and 1.4 mm respectively in Saire estuary (n=3) and Cul-de-Loup bay (n=5). This difference is marked by (i) an intense reduction of Fe (oxy)hydroxides at 4 cm of sediment depth in the Saire estuary, (ii) the appearance of ΣHS- from ~ 12 cm of sediment depth against 5 cm of sediment depth in the Cul-de-Loup Bay and (iii) a slight Fe(oxy)hydroxide zone at 3 cm of sediment depth. Metagenomics analysis confirm major differences between the two study sites.

How to cite: El Houssainy, A., Poirier, I., Bertrand, M., Verdier, L., and Cesbron, F.: Vertical distribution and aerobic degradation at the sediment-water interface in two urbans estuaries in Normandy, France, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12143, https://doi.org/10.5194/egusphere-egu22-12143, 2022.

EGU22-13482 | Presentations | BG1.6

Identification of Desulfuromonas carbonis sp. nov. Metabolites that are Secreted in Response to Different Electron Acceptors 

Zohar Tik, Hanni Vigderovich, Orit Sivan, and Michael M. Meijler

Anaerobic respiration is being observed in many aquatic environments as an outcome of oxygen depletion. Chemical profiles in porewater of organic-rich sediments indicate that various microbes use several electron acceptors in the anaerobic dissimilatory respiration. These electron acceptors are used in the order of decreasing chemical potential, beginning with nitrate, then manganese and iron oxides, then sulfate and finally carbon dioxide .1 During respiration, organisms consume and produce metabolites and thus are changing their environment. 
Some bacteria are capable of using various compounds as final electron acceptors (EA). One of those bacteria is Desulfuromonas carbonisis sp. nov., a Gram-negative, obligatory anaerobic, rod-shaped bacterium. This bacterium is closely related to bacteria from the Geobacter genus, which is well known as a major iron reducer through dissimilatory anaerobic respiration. Species from this genus are found in natural anaerobic systems and are capable of reducing Fe(III)-oxides, S0, and Mn(IV)-oxides. Here we investigated the change in Desulforomonas metabolites as a result of available EA. 
Bacterial cultures were extracted, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) data were analyzed using the global natural products social molecular networking (GNPS) online platform.2 Our results indicate that unique metabolites are produced by the bacteria depending on the presence of different EA in the culture, while some of the metabolites were shared by two groups or more. Indole-3-carboxaldehyde (I3C) was found almost exclusively in the iron-oxide containing cultures. This compound is known as part of tryptophan metabolism and is known to affect chemical communication of bacteria. To the best of our knowledge, I3C was not identified in the Desulfuromonas genus until now. 
We were able to detect this compound not only in pure cultures but also in cultures containing the bacterium, natural anoxic lake sediment and iron oxides. That establishes the potential of I3C to be involved in natural processes specific to dissimilatory iron reduction. We will continue to investigate these processes and the connection between I3C signaling and iron. 

1. Froelich, P. N. et al. Early oxidation of organic matter in pelagic sediments of the eastern equatorial Atlantic: suboxic diagenesis. Geochim. Cosmochim. Acta 43, 1075–1090 (1979). 
2. Wang, M. et al. Sharing and community curation of mass spectrometry data with Global Natural Products Social Molecular Networking. Nature Biotechnology vol. 34 828–837 (2016). 

How to cite: Tik, Z., Vigderovich, H., Sivan, O., and Meijler, M. M.: Identification of Desulfuromonas carbonis sp. nov. Metabolites that are Secreted in Response to Different Electron Acceptors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13482, https://doi.org/10.5194/egusphere-egu22-13482, 2022.

Mercury is a persistent and bioaccumulative environmental pollutant, entering the atmosphere mostly in elemental form and leaving in a variety of oxidized forms. However, current detection methods distinguish only three operationally defined forms: elemental, gaseous oxidized, and particulate mercury. The knowledge of molecular speciation is limited and comes mostly from computational studies, hindering our understanding of atmospheric mercury chemistry and global cycling. Achieving molecular speciation of oxidized mercury (Hg(II)) in atmospheric measurements is a major challenge because of its extremely low abundance, requiring pre-concentration on adsorbents. There is a concern that the speciation of adsorbed Hg(II) can be altered in exchange reactions with itself and with co-adsorbed atmospheric chemicals. Here we present the results of our experimental investigation of gas-surface reactions and exchange reactions involving Hg(II) and several other chemical species. These reactions were studied in aqueous solutions and on surfaces, and the products were analyzed at a molecular level in gaseous, dissolved, and solid forms. Molecular-level detection was made possible by using chemical ionization and electrospray ionization mass spectrometries, which provided sufficiently high sensitivity for direct detection of Hg(II) in laboratory experiments, avoiding the pre-concentration step. In all cases, we observed binding of gaseous Hg(II) to surfaces, followed by rapid formation of exchange products, some of which could be readily volatilized back into gas phase. We propose that a similar exchange may occur both on the surfaces of aerosols in the atmosphere and on adsorbents during sample collection, scrambling the actual and perceived speciation of atmospheric Hg(II).

How to cite: Khalizov, A. and Mao, N.: Surface reactions can alter both perceived and actual composition of atmospheric Hg(II), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-33, https://doi.org/10.5194/egusphere-egu22-33, 2022.

EGU22-180 | Presentations | BG1.7

Changes in mercury volatilization flux induced by water vapor generation in soils under dynamic temperature 

Monami Kondo, Ryota Tanaka, Yasuhide Sakamoto, Yoshishige Kawabe, Kengo Nakamura, Noriaki Watanabe, and Takeshi Komai

With the entry into force of the Minamata Convention from 2017, anthropogenic mercury emissions into the atmosphere have been regulated, and therefore global mercury management has become an important issue. It should be noted that the amounts of anthropogenic mercury emissions and natural emissions from terrestrial sources such as soil and vegetation are almost the same based on the Global Mercury Assessment Model by UNEP (2013). Previous studies have clarified that various environmental factors such as temperature, soil porosity and water content, and pH of the water influence mercury volatilization flux from soils. In order to understand and predict transport phenomena of mercury in soils including the emission to the atmosphere, it is necessary to consider in detail not only static factors such as soil porosity but also dynamic factors such as temperature including their spatial variations.

In this study, continuous measurements of mercury volatilization flux were conducted for dynamic temperature, different soil water contents and pH-dependent dissolved mercury species. The results showed that the flux values under dynamic temperature were different from those under static temperature even at the same temperature. Additionally, changes in the flux under dynamic temperature depended on the soil water content. We have found that it is difficult to predict mercury volatilization flux under dynamic condition based on the knowledges obtained under static condition probably due to large influence of water vapor generation under dynamic temperature. It is therefore necessary to understand advection and diffusion in soils in the presence of volatilization and condensation of water and dissolved mercury for better understanding mercury flux emission from the soils.

How to cite: Kondo, M., Tanaka, R., Sakamoto, Y., Kawabe, Y., Nakamura, K., Watanabe, N., and Komai, T.: Changes in mercury volatilization flux induced by water vapor generation in soils under dynamic temperature, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-180, https://doi.org/10.5194/egusphere-egu22-180, 2022.

EGU22-363 | Presentations | BG1.7

Does climate change affect mercury inflow to periglacial regions? (King George Island, Antarctica) 

Aleksandra Cichecka, Dominika Saniewska, and Michał Saniewski

Mercury (Hg) is considered as a global pollutant. It is persistent in the environment and in organic compounds, mainly as methylmercury (MeHg), is accumulated in living organisms and it biomagnifies up the trophic chain. Periglacial areas in Antarctica have had the highest temperature rise in the southern hemisphere over the past fifty years (+3 ˚C). The loss of the ice cover and the exposure of larger and larger ground surfaces caused by the increasing temperature, enable the initiation of rock erosion and soil formation processes. The King George Island is formed by rocks of volcanic origin. Therefore, this material could be a source of many compounds in the Antarctic coastal zone. In turn, these new periglacicl areas are places where more life (flora and fauna) appears. Both of these factors disturb the circulation of many elements in the polar region. The aim of the study was to determine the impact of periglacial regions formation on the inflow of Hg to the Antarctic ecosystem. The bioavailability of Hg contained in rocks and soil in the study area was also tested.

Sampling took place in December 2018 and January 2019 in the King George Island. The samples of soil, lichen, moss, vascular plant and algae were collected and stored at -20 °C until analysis. The concentration of total mercury (THg) was measured by pyrolysis with the technique of atomic absorption spectroscopy on a direct mercury analyser DMA-80. To measure the concentration of methylmercury samples were extracted, MeHg concentration was measured using Automated Methtlmercury System MERX-M.

Research carried out on the King George Island has shown that mercury concentrations in soil and in rocks were slightly higher than those measured in continental Antarctica, but lower than in other parts of the world. However, concentrations of mercury in lichens were similar to those in urbanized regions worldwide. The research confirmed the correlation between the weathering processes of volcanic rocks in the studied area and the concentration of THg in the soil. Measured concentration of THg and MeHg in plants and lichens on King George Island indicated that bioavailable Hg was present in soil and rocks but weathering of rocks was only one of mercury sources. Methylmercury accounted for, on average, 15% of total mercury in lichens and plants samples but 0.1% in soil samples. The presence of animals - penguins and sea elephants had an impact on the increased concentration of THg and MeHg both in soil and in plant/lichen samples. 

This study has been performed within the framework of a National Science Center projects No. 2019/33/B/ST10/00290 and No. 2017/27/N/ST10/02230.

How to cite: Cichecka, A., Saniewska, D., and Saniewski, M.: Does climate change affect mercury inflow to periglacial regions? (King George Island, Antarctica), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-363, https://doi.org/10.5194/egusphere-egu22-363, 2022.

EGU22-365 | Presentations | BG1.7

Mercury and methylmercury in the benthic organisms of Admiralty Bay (Antarctica). 

Małgorzata Jarzynowska, Dominika Saniewska, Michał Saniewski, and Piotr Bałazy

There are only few studies on the concentration of mercury in organisms inhabiting the polar regions, in particular those living in Antarctica. Therefore, it is difficult to accurately illustrate the toxic effects of mercury on the local fauna. The aim of this study was to recognize the concentration of total mercury and methylmercury in organisms inhabiting the Antarctic coastal zone and compare these results with organisms from the Arctic. An attempt was made to determine the potential for mercury and methylmercury to accumulation and biomagnification in the benthic food web depending on the trophic level and the size of the organism. In addition, the effect of melting glaciers on the concentration of total mercury in marine organisms was investigated. The research was carried out on samples of benthic organisms collected directly by divers from the Admiralty Bay during austral summer 2018/2019.The concentration of total mercury and methylmercury was analyzed in 3 representatives of Antarctic benthos - gastropod Nacella concinna, sea urchin Sterechinus neumayeri and starfish Odontaster validus using the method of atomic absorption spectrometry. The obtained results confirmed the existence of processes such as accumulation and biomagnification of mercury in marine organisms from the Admiralty Bay. However, mercury concentration in Antarctic zoobenthos were lower than those measured in the Arctic, as well as methylmercury concentration. The problem of high mercury and methylmercury concentration in organisms inhabiting the polar regions is particularly important due to the characteristics of the local fauna, which is slow metabolism and longevity. In addition, the endemic nature of the Antarctic fauna and the relatively short trophic chain mean that these animals, and especially the organisms at the top of the food pyramid, may be particularly endangered on many contaminants. Research on benthic organisms can be an important part of polar monitoring, due to their relatively limited movement. This study has been performed within the framework of a National Science Center projects No. 2019/33/B/ST10/00290 and No. 2017/27/N/ST10/02230.

How to cite: Jarzynowska, M., Saniewska, D., Saniewski, M., and Bałazy, P.: Mercury and methylmercury in the benthic organisms of Admiralty Bay (Antarctica)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-365, https://doi.org/10.5194/egusphere-egu22-365, 2022.

EGU22-1108 | Presentations | BG1.7

Fractionation of mercury stable isotopes in lichens over a period of one year 

Dominik Božič, Igor Živković, Jože Kotnik, Marta Jagodic Hudobivnik, Darja Mazej, Marko Štrok, and Milena Horvat

Biomonitoring of mercury (Hg) in the air using transplanted and in-situ lichens were studied at three locations in Slovenia: 1) the former Hg mine Idrija, with known Hg contamination; 2) vicinity of a Hg point source of pollution near the cement production plant in Anhovo, and 3) a noncontaminated reference site at Pokljuka. Total Hg concentrations and Hg isotopic composition were measured. Lichens were transplanted from Pokljuka, exposed at different sites in three locations and sampled four times, once per season. Lichens were exposed under tree branches, on fences and also under cover, allowing them different exposure to natural light. Additionally, the in situ lichens were sampled at the beginning and the end of the one year sampling period. As expected, the trend of concentrations in transplanted lichens increased over time, especially in the area of Idrija, and significantly less in the area of Anhovo, which is consistent with previous research. Significant mass dependent fractionation has been observed in transplanted lichens. δ202Hg changed from winter to summer from -2.5 to -0.5 ‰ and dropped again to -2.5 in autumn/winter of the following year. The most likely mechanism for this is Hg reduction (biotic or abiotic) and / or Hg evaporation in summer due to elevated temperatures, leaving heavier isotopes on the lichen thalli. The in situ lichens that were sampled one year apart show no major changes in isotopic composition. Such a trend has been observed in all of the samples apart from the ones from the most polluted Idrija sampling site directly above the former smelting plant. This is probably due to the new Hg constantly being deposited to the lichen with local isotopic fingerprint. Small mass independent fractionation was observed, likely due to photo-reduction as was concluded in similar foliage studies, but no trends in its change over time were seen.

How to cite: Božič, D., Živković, I., Kotnik, J., Jagodic Hudobivnik, M., Mazej, D., Štrok, M., and Horvat, M.: Fractionation of mercury stable isotopes in lichens over a period of one year, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1108, https://doi.org/10.5194/egusphere-egu22-1108, 2022.

EGU22-2081 | Presentations | BG1.7

Melting glaciers as a potential source of methylmercury in the first chains of Antarctic pelagic food web (Admiralty Bay) 

Dominika Saniewska, Ewa Korejwo, Michał Saniewski, and Piotr Bałazy

Recent studies have found that the Antarctic is a sink for mercury (Hg). The unique atmospheric mercury depletion events stimulate Hg deposition and its incorporation in the marine food web. This metal can also be sequestrate in the snowpack along all Antarctica. Therefore, this region should be considered as a giant cold trap of mercury. The ice sheet in West Antarctica is now in a state of dynamical imbalance and the rate of ice loss is five times greater than was thought. Therefore melting ice sheet and glaciers should be considered as an important secondary mercury source for the Antarctic, which can result in an increase of Hg concentration in marine biota. The aim of the research was to identify methylmercury (MeHg) sources in Antarctica and determine their potential for accumulation in the marine trophic chain. Sampling was conducted in the Admiralty Bay in December 2018. As part of the research marine samples (water, suspended particulate matter, phyto- and zooplankton) were collected. Total mercury, methylmercury and labile Hg concentration were determined in the samples.

Mean MeHg concentration in Admiralty Bay was 15 pg/dm3, and the highest values were measured in the vicinity of melting glaciers. MeHg in water occurred mainly in dissolved form (>70%), thus promoting the accumulation of Hg for plankton. Higher values of MeHg concentration were measured in phytoplankton (mean 204 pg/dm3) than in zooplankton (mean 143 pg/dm3). Different factors influence the accumulation of MeHg in both groups of plankton.

This study has been performed within the framework of a National Science Center projects No. 2019/33/B/ST10/00290 and  No. 2017/27/N/ST10/02230.

How to cite: Saniewska, D., Korejwo, E., Saniewski, M., and Bałazy, P.: Melting glaciers as a potential source of methylmercury in the first chains of Antarctic pelagic food web (Admiralty Bay), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2081, https://doi.org/10.5194/egusphere-egu22-2081, 2022.

EGU22-3662 | Presentations | BG1.7

Recent spatial and seasonal variations of mercury in suspended particulate matter of the legacy contaminated river Elbe (Germany) 

Jan G. Wiederhold, Harald Biester, Alexandra Alten, Jens Hahn, and Lars Duester

The Elbe is historically one of the most contaminated rivers in central Europe [1]. Together with its tributaries, it drains a heavily industrialized and densely populated area including e.g., Praha, Dresden, Berlin, and Hamburg. For many decades, the river Elbe has been strongly affected by contaminants from diverse sources (e.g., industry, mining). Mercury (Hg) is one of the priority pollutants and, despite decreasing inputs and Hg contents in river water and suspended particulate matter (SPM) over the last decades, Hg concentrations remain elevated and the environmental quality standard of the EU Water Framework Directive for Hg in biota is still clearly exceeded in all parts of the river. Riverine Hg transport is dominated by strong binding to SPM. However, the biogeochemical controls and seasonal variations of Hg binding to riverine SPM and its speciation are still poorly understood.

Here, we present recent investigations on Hg concentrations and binding forms in SPM collected at multiple sites along the river Elbe throughout different seasons. SPM was collected monthly from sedimentation boxes and different preservation methods were tested (e.g., on-site freezing with liquid N2 in the framework of sampling for the German environmental specimen bank [2]). Total Hg contents were measured by a direct Hg analyzer. Pyrolytic thermodesorption (PTD) was used to determine Hg binding forms in SPM by continuous heating up to 650°C in a N2 gas flow and comparison to Hg release curves of reference compounds [3]. Moreover, public data from federal monitoring programs [4] was used to evaluate long term trends in comparison to our new results.

Total Hg concentrations in SPM generally ranged from about 300 to 1700 µg kg-1. While these concentrations are much lower than historical values >50 mg kg-1 [1, 4], they are still elevated compared with estimated natural background values <200 µg kg-1. Higher concentrations were generally observed after the confluence of the tributaries Mulde and Saale, but also further downstream in the Hamburg region. Seasonal variations were apparent at most sampling sites with fluctuations up to a factor of 2-3. Several sites exhibited higher Hg concentrations in winter, which could be potentially explained by dilution with more organic matter in SPM during summer, but an additional control by hydrological fluctuations is likely. The PTD results revealed a dominance of “matrix-bound” Hg(II), likely associated with organic matter and/or oxide minerals, while elemental Hg(0) and sulfidic Hg were not detected in riverine SPM. Future work will include methyl-Hg analysis as well as the characterization of microbial communities in SPM and sediments to further elucidate the complex biogeochemical Hg cycling in such dynamic riverine environments.

[1] Wilken R.D., Wallschläger, D. (1996) The Elbe river: a special example for a European river contaminated heavily with mercury. In Global and Regional Mercury Cycles: Sources, Fluxes and Mass Balances (pp. 317-328). Springer, Dordrecht.

[2] German Environmental Specimen Bank (https://www.umweltprobenbank.de/en)

[3] Biester H., Scholz C. (1996) Determination of mercury binding forms in contaminated soils: Mercury pyrolysis versus sequential extractions. Environ. Sci. Technol. 31, 233-239.

[4] https://www.elbe-datenportal.de; https://www.ikse-mkol.org; https://undine.bafg.de

How to cite: Wiederhold, J. G., Biester, H., Alten, A., Hahn, J., and Duester, L.: Recent spatial and seasonal variations of mercury in suspended particulate matter of the legacy contaminated river Elbe (Germany), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3662, https://doi.org/10.5194/egusphere-egu22-3662, 2022.

EGU22-4060 | Presentations | BG1.7

Hourly resolution measurement of gaseous oxidized mercury using a membrane-coupled sampling system 

Qingru Wu, Yi Tang, Shuxiao Wang, Guoliang Li, Deming Han, Kaiyun Liu, and Zhijian Li

Temporal variation trend of gaseous oxidized mercury (Hg2+) in air is significant to understand global mercury cycling and is urgent to evaluate the effectiveness of the Minamata Convention on Mercury. However, Hg2+ monitoring is still one of the largest challenges in atmospheric mercury research field, where existing methods cannot simultaneously satisfy the measurement requirements of both accuracy and time precision. Here, we developed a hourly resolution gaseous oxidized mercury sampling system (HGOMS) which coupled a cation exchange membrane (CEM)-based sampling system with the Tekran 2537/1130/1135 equipment. The two stage CEM coupled in our system can capture almost all Hg2+ under high HgBr2 exposure (1.45±0.05 ng m-3) in laboratory experiment. During the field observation, the breakthrough percentage of the first stage is approximately 10% and the time resolution of Hg2+ concentration measurement is 2 h. The 3-week measurement using HGOMS showed an hour-average Hg2+ concentration of 0.46±0.36 ng m-3, which is approximately 23 times higher than the measurement using KCl-coated denuder at urban Beijing. In addition, enhanced Hg2+ concentrations was observed during the daytime with diurnal amplitude of 0.37 ng m-3, indicating the strong photochemical production of Hg2+. Given the current prevalent low bias of Hg2+ in observation and model simulation, our study indicates the urgency to re-evaluate global Hg2+ measurement and air mercury reaction mechanism in the atmospheric mercury transport model.  

How to cite: Wu, Q., Tang, Y., Wang, S., Li, G., Han, D., Liu, K., and Li, Z.: Hourly resolution measurement of gaseous oxidized mercury using a membrane-coupled sampling system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4060, https://doi.org/10.5194/egusphere-egu22-4060, 2022.

EGU22-5161 | Presentations | BG1.7

Mercury Life Cycle in the Dental Office 

William Purves

Amalgam is the primary source of mercury entering the aqueous environment. According to the US EPA 46% of the total mercury entering the environment.  The US EPA has established a regulatory category for dental discharge (40 CFR 441). It focuses on amalgam separators and ISO 11143 standard as the primary process for amalgam removal as a solid.  The ISO standard does not address the more serious issue of dissolved mercury.

Amalgam dissolves slowly in the separator generating soluble mercury levels up to part per million concentrations which are difficult to remove.  This process defeats the purpose of the separator. The US regulation is seriously flawed as it does not address this issue by establishing a total mercury discharge limit or allow innovation to develop to reduce total mercury by allowing Best Available Technology.

Removal of amalgam from the dental waste stream can be done as a pretreatment process at the dental chair.  All dental chairs have a feature called a chair side trap.  This trap is designed to capture large particles to protect the vacuum system lines from clogging.  A proper trap design can be the most effective pretreatment step in the overall amalgam removal process and mercury reduction.

The new chair side trap design removes up to 99% of the amalgam solids at the chair as compared to <5% with current traps.  This trap simply replaces the old design and requires no change in dental office operation or equipment.  Removal of amalgam solids before the separator effectively reduces the concentration of both solid and dissolved mercury entering the environment.  The trap along with an activated carbon style separator have seen reductions of as much as 99.9%.  This paper addresses the problem and provides real time data proving the effectiveness of the system.

How to cite: Purves, W.: Mercury Life Cycle in the Dental Office, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5161, https://doi.org/10.5194/egusphere-egu22-5161, 2022.

EGU22-5866 | Presentations | BG1.7

The importance of the ecosystem in marine mercury modelling 

David Amptmeijer and Johannes Bieser

Mercury is a pollutant of global concern due to its ability for long-range atmospheric transport, combined with its capability to be methylated into the neurotoxin methylmercury in the marine environment. The consumption of methylmercury in seafood is the primary hazard of mercury to humans, but most mercury emissions are in the form of atmospheric inorganic mercury. The link between inorganic atmospheric mercury and organic mercury in biota is poorly understood.  Here we present our newly developed mercury bioaccumulation model for the North and Baltic Sea based on a fully resolved biogeochemical hydrodynamic model. The modelled bioaccumulation falls well in the range of observations and works by combining a new bioaccumulation model combined with the MERCY Hg speciation model and the ECOSMO ecosystem model. In phytoplankton, bioaccumulated mercury is mostly inorganic. In zooplankton inorganic and organic mercury is roughly equal and it originates in similar amounts from direct uptake from the water column and dietary interactions. In planktivorous fish organic mercury originating from trophic interactions is by far the dominant contaminant, interestingly omnivorous have a higher fraction (~20%) of methylmercury from passive uptake than planktivorous fish, this likely due to the longevity (10~15 years) of these high trophic predatorial fish. Notable interactions between bioaccumulation and Hg speciation in the model are that the cyanobacterial uptake of Hg2+ and MMHg on the shallow sea surface layer decreased mercury release into the atmosphere and lead to a higher buildup of both organic and inorganic mercury throughout the water column, additionally, POC is a major factor transporting Hg to deep anoxic bottom water increasing the amount of methylmercury. Our results indicate that the ecosystem plays an essential role in marine Hg cycling and should not be carelessly ignored in models. 

How to cite: Amptmeijer, D. and Bieser, J.: The importance of the ecosystem in marine mercury modelling, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5866, https://doi.org/10.5194/egusphere-egu22-5866, 2022.

EGU22-5986 | Presentations | BG1.7

Methylmercury in thawing peatlands on a trophic gradient in boreal Western Canada 

Lauren Thompson, Renae Shewan, Lorna Harris, Vaughn Mangal, and David Olefeldt

Ongoing permafrost thaw in the extensive peatlands of boreal western Canada may mobilize previously frozen mercury (Hg) and result in enhanced production of the neurotoxin methylmercury (MeHg). The often waterlogged conditions in thermokarst wetlands may represent ideal environments for Hg methylation to MeHg, but methylation potential could vary across distinct wetland types (i.e., nutrient-poor bogs and nutrient-rich fens) that emerge after the thawing of drier peat plateaus, depending on landscape position and groundwater connectivity. Here, we examined MeHg concentrations in twelve wetlands of varying nutrient richness in the Taiga Plains of western Canada across a 500 km permafrost gradient. We analyzed peat porewater chemistry (Hg, MeHg, dissolved organic matter composition), inferred the degree of groundwater connection (electrical conductivity, ions), and assessed the vegetation composition at each wetland. The key research objectives of this study were to 1) determine how methylmercury concentrations vary amongst wetland types in the Taiga Plains and amongst permafrost zones, and 2) understand how physicochemical characteristics and groundwater connectivity may influence methylation potential. Through this, we hope to understand the factors that lead to hotspots of MeHg production in the rapidly thawing peatlands of the Taiga Plains.

How to cite: Thompson, L., Shewan, R., Harris, L., Mangal, V., and Olefeldt, D.: Methylmercury in thawing peatlands on a trophic gradient in boreal Western Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5986, https://doi.org/10.5194/egusphere-egu22-5986, 2022.

EGU22-6902 | Presentations | BG1.7

Real-time air mercury response from sediment-covered, volcanogenic massive sulphide mineralization on southern Vancouver Island, British Columbia, Canada. 

Alexei S. Rukhlov, Nikolay R. Mashyanov, Pavel V. Pitirimov, Adrian S. Hickin, Maksym Golovetskyy, and Ben Coats

New data from the Lara-Coronation polymetallic occurrence, southern Vancouver Island, British Columbia, Canada confirm that direct and continuous analysis of gaseous elemental mercury (GEM) concentrations in near-surface air using a portable RA-915M Zeeman Hg analyzer can instantly delineate mineralized zones that are buried beneath overburden 10s of m thick. Real-time grid sampling of air 1 cm above ground across steeply dipping, massive sulphide zones in volcanic rocks of the McLaughlin Ridge Formation (Sicker Group; Middle to Late Devonian) reveals a pattern of northwest-trending GEM haloes that reflect bedrock structure, including a 224 by 30 m halo above the polymetallic Coronation zone, covered by up to 22 m of overburden. Measured GEM concentrations range from 0.61 to 251 ng·m-3 in this study, with the strongest halo (206x background Hg) above exposed mineralization. Weak haloes (1.7x background Hg) mark sediment-covered mineralized zones. Before sampling GEM above overburden, we disturbed surface sediment mechanically with a hoe pick to release Hg0 adsorbed in soils and vegetation. Measuring gaseous mercury using a portable device is simple, effective, and more efficient than standard geochemical surveys that collect sediment, soils, and vegetation. The method will become increasingly useful to the mineral industry as exploration shifts into areas covered by overburden.

How to cite: Rukhlov, A. S., Mashyanov, N. R., Pitirimov, P. V., Hickin, A. S., Golovetskyy, M., and Coats, B.: Real-time air mercury response from sediment-covered, volcanogenic massive sulphide mineralization on southern Vancouver Island, British Columbia, Canada., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6902, https://doi.org/10.5194/egusphere-egu22-6902, 2022.

EGU22-7647 | Presentations | BG1.7

Methylmercury build-up in above ground logging residues 

Karin Eklöf, Haiyan Hu, Ulf Sikström, Andrea Garcia Bravo, Axel Blomgren, Mikael Dooha, Staffan Åkerblom, Linnea Hansson, Stefan Bertilsson, Joel Segersten, Claudia Cascone, Maidul Choudhury, and Erik Björn

Forest harvest might mobilize mercury (Hg) retained in soils and promote the transformation of inorganic Hg to its more bioavailable and toxic form methyl-Hg (MeHg). Previous studies, however, have revealed considerable variation in effects of forest harvest on the runoff of total Hg (THg) and MeHg between sites. This study addresses one factor that may influence the forestry effect: the impacts of logging residues left on site after forest harvest. The availability of labile organic matter (OM) as electron donors for Hg methylators has previously been proposed as a central factor causing higher MeHg formation in forest harvested areas. However, to the best of our knowledge, there are no studies that have evaluated the processes associated with a possible increase in MeHg production under and/or in piles of logging residues.

In this field-based experiment at Skogforsks´ test site in south-central Sweden (303 Tobo), we have evaluated mechanisms that may cause enhanced MeHg production in biofilms associated with logging residues and/or in soils underlying piles of such residues. The experimental setup included 12 sample plots, half with soil covered with residues and half without residues. Residues samples consisting of Norway spruce needles, were collected from upper and lower part of the pile, and soil samples were collected from soil covered and not covered with residues. Temperature and moisture were registered continuously using sensors. Soil water, for OM quality measures, were collected using lysimeters. Microbial communities were analyzed using DNA extracted from soils and residues to assess the relative abundance of Hg methylating microorganisms. Three sampling occasions (spring, summer and autumn) covered a variation in temperature and soil moisture.

Contrary to our hypothesis, there was no difference in MeHg concentrations or the ratio of MeHg (%MeHg) in soils covered (n=18) or not covered (n=18) with logging residues. Instead, the piles of above ground logging residues accumulated high concentrations of MeHg. The %MeHg was significantly higher in the residue piles, both in the top and bottom (n=32), compared to the underlying soils (n=32). The concentrations of MeHg were slightly higher at the bottom of the pile compared to the top, possibly because of reduced temperature amplitudes, higher moisture, and larger pool of THg at the bottom of the pile. Microbial analyses also indicated a higher overall bacterial abundance and interestingly also a higher abundance of archaeal hgcA genes in above ground residue samples compared to underlying soil samples, implying methanogenic conditions in the biofilm with possible influence on MeHg production. These results suggest that MeHg are formed in suboxic/anoxic microenvironments favored by access of OM from decomposing logging residues in the biofilms of the substrate itself.

In summary, we show that hotspots of MeHg are not only found in soils and waters but also in biofilms above-ground. Logging residues left on site after forest harvest can thereby be a source of MeHg. However, the presence of logging residues can also protect the soil from disturbances by off-road traffic and thereby prevent the potential mobilization of MeHg in ruts.

How to cite: Eklöf, K., Hu, H., Sikström, U., Garcia Bravo, A., Blomgren, A., Dooha, M., Åkerblom, S., Hansson, L., Bertilsson, S., Segersten, J., Cascone, C., Choudhury, M., and Björn, E.: Methylmercury build-up in above ground logging residues, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7647, https://doi.org/10.5194/egusphere-egu22-7647, 2022.

EGU22-7823 | Presentations | BG1.7

Mercury distribution and reactivity in the Siberian Shelf: preliminary data from the Arctic Expedition ISSS-2020 

Alyssa Azaroff, Örjan Gustafsson, Igor Semiletov, and Sofi Jonsson

Despite the remote location of the Arctic Ocean (AO), mercury (Hg) level in some Arctic species has increased due to the global anthropogenic Hg emissions. Methylmercury (MeHg), the form of Hg known to bioaccumulate in biota to levels of concern, is a neurotoxin that is mainly produced by microbial methylation of inorganic mercury (iHg) in sediments and natural waters. While huge efforts are made to better understand the Hg cycling of the AO, observational data is still missing for many areas. This is especially true for the largest continental shelf on earth, the Siberian continental shelf.

Here we present the first data on mercury speciation from the international Russian-Swedish Arctic expedition “International Siberian Shelf Study 2020” (ISSS-2020). During the expedition, onboard the research vessel Akademik Mstislav Keldysh, water and sediment were collected from the Barents Sea, Kara Sea, Laptev Sea, and the East Siberian Sea. In addition to samples collected for Hg speciation analysis, experimental incubations of water and sediment using isotopically enriched stable mercury were performed to estimate potential mercury transformations rates. Microbial samples were also collected to determine the microbial diversity associated with mercury transformation.

How to cite: Azaroff, A., Gustafsson, Ö., Semiletov, I., and Jonsson, S.: Mercury distribution and reactivity in the Siberian Shelf: preliminary data from the Arctic Expedition ISSS-2020, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7823, https://doi.org/10.5194/egusphere-egu22-7823, 2022.

EGU22-8047 | Presentations | BG1.7

Evaluation of sampling and sample preparation methodologies for multi-elemental analysis in foliage samples 

Saeed Waqar Ali, David Kocman, Marta Jagodic Hudobivnik, and Milena Horvat

Several approaches exist in literature for sample collection, preparation, and quantification of mercury concentration in foliage samples. Comparability of results from studies with varying methodological approaches are therefore critical for accurate estimation of vegetation control on Hg intercompartmental exchanges. To this end, field visits were carried out for the collection of foliar samples of Carpinus betulus in two forest sites in Slovenia having contrasting Hg source (Ljubljana as urban site and Idrija as Hg contaminated site). Foliage samples collected from different locations on the tree crown were then prepared to test the effect of washing on overall Hg foliar content. Each sample was then allowed to dry using selected procedures during their preparation for the determination of Hg content using ICP-QQQ-MS. Results show that the effect of sample treatment procedures on mercury concentration in foliar samples exhibit contrasting pattern with varying Hg source. Whereas the effect of washing was not evident on foliar samples collected from Ljubljana at mean Hg concentration of 9.85 ± 2.21 ng g-1, washing of foliar samples significantly decreased Hg concentration in foliar samples from Idrija (washed: 254.26 ± 120.30 ng g-1, unwashed: 392.94 ± 210.47 ng g-1, p=0.028). Variation in foliar Hg concentration within tree crown was evident both in Ljubljana (upper: 8.50 ± 1.16 ng g-1, outer: 8.85 ± 1.93 ng g-1, inner: 12.28 ± 1.04 ng g-1, p=0.005) as well as in samples from  Idrija (upper: 239.32 ± 201.76 ng g-1, outer: 390.62 ± 208.40 ng g-1, inner: 336.30 ± 85.70 ng g-1, p=0.04) with mean concentration of 322.34 ± 184.18 ng g-1, several folds higher than those reported in foliar samples from Ljubljana. Overall, different drying procedures did not cause significant change in foliar Hg concentration from Ljubljana however, foliar samples from Idrija that were dried in the oven at 60°C had lower Hg concentration possibly indicating Hg loss during the drying procedure. Our results demonstrate that the choice of sampling and sample preparation methodologies for determination of foliar Hg concentration are strongly influenced by the presence of Hg source in the studied area which is critical consideration for future studies.

How to cite: Ali, S. W., Kocman, D., Hudobivnik, M. J., and Horvat, M.: Evaluation of sampling and sample preparation methodologies for multi-elemental analysis in foliage samples, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8047, https://doi.org/10.5194/egusphere-egu22-8047, 2022.

EGU22-8139 | Presentations | BG1.7

Mercury isotope composition in living corals 

Rui Zhang, Yi Liu, and Ruoyu Sun

    Coral reef ecosystem is characterized by rich biodiversity, high primary productivity and rapid material cycling. Up until now, Hg research in coral reef ecosystems is extremely limited, limiting our knowledge about Hg cycling in this important system. The aim of this study is to trace the source, migration and transformation of Hg in living corals by measuring their stable mercury isotope ratios in corals.

    In this study, 27 coral samples from different species were collected from Luhuitou coral reef area, Hainan Island, China. The living coral tissues and symbiotic zooxanthellae were separated by centrifugation, and measured for concentrations of total mercury (THg) and methylmercury (MeHg) and mercury isotope ratios.

    The average THg of all zooxanthellae samples (n=27) was 18.72 ± 13.98 ng/g, almost twice that of tissues samples (n=23) of 10.38 ± 9.06 ng/g. The MeHg/THg ratios in the samples of tissues (n=3) and zooxanthellae (n=3) were both very low, but this ratio in zooxanthellae was generally higher than that in tissue for the same coral sample. Our observations thus suggest that there is a difference in Hg enrichment efficiency between zooxanthellae and coral tissues, or that there is a detoxification mechanism in coral tissues.

    δ202Hg (representing mass dependent fractionation, MDF) ranged from 0.00‰ to -1.99‰ and 0.10‰ to -1.15‰ for coral tissues (n=13) and zooxanthellae (n=20), respectively Δ199Hg (representing odd number isotope mass independent fractionation, odd-MIF) ranged from 0.01‰ to -1.28‰ and 0.07‰ to -1.37‰ for coral tissues (n=13) and zooxanthellae (n=20), respectively. Both δ202Hg and Δ199Hg values of zooxanthellae were close to those of coral tissues in the same sample.

    It is interesting to note that most of coral tissues and zooxanthellae have negative odd-MIF values, and Δ199Hg and Δ201Hg are highly correlated with a linear Δ199Hg/Δ201Hg slope of 1.8. Given that coral reefs are located in shallow sea waters with very high light transmission, the negative odd-MIF might be produced during photoreduction of Hg(II) binding to sulfur-containing ligands. Although a small fraction of MeHg exists in coral tissues and zooxanthellae, MeHg photodegradation only produces positive odd-MIF in the aqueous MeHg. Thus, the odd-MIF observed in tissues and zooxanthellae is unlikely produced by MeHg photodegradation. An experimental study shows that gaseous Hg(0) photooxidation process by halogen radicals could produce Hg(II) with more negative MIF than Hg(0), with a Δ199Hg/Δ201Hg slope of 1.64 for Br radical and 1.89 for Cl radical[1]. However, it is unknown if similar Hg(0) oxidation processes operate in coral ecosystem.

    The work was supported by the National Science Foundation of China (41922019). 

[1] Sun, G. Y., J. Sommar, X. B. Feng, et al. Mass-Dependent and -Independent Fractionation of Mercury Isotope during Gas-Phase Oxidation of Elemental Mercury Vapor by Atomic Cl and Br[J]. Environmental Science & Technology: 2016, 50 (17): 9232-9241.

How to cite: Zhang, R., Liu, Y., and Sun, R.: Mercury isotope composition in living corals, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8139, https://doi.org/10.5194/egusphere-egu22-8139, 2022.

EGU22-8253 | Presentations | BG1.7

Mercury released from newly formed volcano influence concentrations in the surrounding ocean 

Isabel Garcia Arevalo, Joël Knoery, Bastien Thomas, Natalia Torres Rodriguez, Lars-Eric Heimbürger Boavida, Cecile Cathalot, and Emmanuel Rinnert and the Geoflamme shipboard scientific party

Volcanic and geothermal areas are important natural sources of mercury, with mercury concentrations in volcanic gases above the atmospheric background. Individual volcanoes exhibit variable degassing features and behavior, leading to considerable uncertainty in global geogenic mercury fluxes estimations. Likewise, studies on mercury emissions from submarine volcanic and hydrothermal sites are scarce. Nevertheless, information on those natural inputs is needed to better estimate the anthropogenic mercury enrichment, and thus for the implementation of the Minamata convention.

During Spring 2021, the GEOFLAMME campaign took place at the northern end of the Mozambique channel, where we examined the influence of volcanic inputs from a volcano that had formed less than 2 years ago near Mayotte Island.  Water samples were obtained with a trace metal-clean CTD rosette and all-titanium high-pressure samplers using the remotely operated vehicle Victor 6000 on board R/V Pourquoi pas?. Total mercury was measured on board via Cold Vapour Atomic Fluorescence Spectroscopy (CV-AFS) following the EPA method 1631. Exhaled fluid samples from titanium samplers followed the same analytical scheme, but at the shore laboratory.

Mercury levels measured from water column showed increased concentrations near the seafloor.  Total mercury measured in fluid samples from the different venting sites showed concentrations 3 to 60 times higher than surrounding seawater.

Our study provides new insight to the understanding for mercury biogeochemistry, the interactions between magmatism, tectonics and fluids circulation processes, as well as the implications on the physical-chemical properties of the water column. It also improves our knowledge on present-day mercury cycling in the marine environment usingfield-based data. Ongoing work will attempt to quantify seafloor mercury inputs to the vicinity of the Mayotte Island.

How to cite: Garcia Arevalo, I., Knoery, J., Thomas, B., Torres Rodriguez, N., Heimbürger Boavida, L.-E., Cathalot, C., and Rinnert, E. and the Geoflamme shipboard scientific party: Mercury released from newly formed volcano influence concentrations in the surrounding ocean, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8253, https://doi.org/10.5194/egusphere-egu22-8253, 2022.

EGU22-8265 | Presentations | BG1.7

Identification of the co-localisation of Hg with Se and Fe by NanoSIMS in sperm whale liver.   

Lhiam Paton, Maria Angels Subirana, Dirk Schaumlöffel, and Jörg Feldmann

The biological pathway by which MeHg undergoes detoxifications in some mammals and birds has yet to be fully elucidated. The current understanding is that HgSe nanoparticles (NPs) are formed in vivo as the end point of a detoxification process. Presented, is a contribution to the body of work already present in the field based on recent insights into the existence of HgSe NPs after Hg was detected by NanoSIMS, for the first time, in the liver of a sperm whale that was beached in Ardersier, Scotland. Analysis by NanoSIMS found heterogenous distribution and co-localisation of Hg with other elements including Se and Fe, giving a possible insight into the complex biological mechanism that ends in tiemannite NPs being stored in the livers of whales. 

 

 

How to cite: Paton, L., Angels Subirana, M., Schaumlöffel, D., and Feldmann, J.: Identification of the co-localisation of Hg with Se and Fe by NanoSIMS in sperm whale liver.  , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8265, https://doi.org/10.5194/egusphere-egu22-8265, 2022.

Graphitic carbon nitride (g-CN) is emerging as a new research hot topic because of its unique electronic band structure, high physicochemical stability, large surface area, non-toxic nature, and is “earth-abundant”. These and other properties have made it a highly researched material especially for visible light photocatalysis and photodegradation applications and as the starting material from which to develop novel electrochemical sensing platforms, adsorbent materials for environmental and biomedical applications. The proposed work reports the development of a 2 dimensional (2D) nanostructure material-based passive sampler, which binds trace concentrations of mercury (Hg2+) by employing ultrathin graphitic carbon nitride (g-CN) nanosheet as an effective adsorbent. The g-CN nanosheets were obtained by exfoliating the bulk g-CN which was synthesized via a thermal polycondensation process. The as-prepared samples were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transforms infrared (FTIR) spectroscopy, and atomic force microscopy (AFM), which confirmed graphite-like structure. The results showed high recovery capacities for Hg2+ in different matrices in the following order: Sea < River < Rain < Mili Q water of 89%, 93 %, 97 and 100 %, respectively. Ion interference studies (Co2+,  Ca2+,  Zn2+, Fe2+, Mn2+, Ni2+, Bi3+, Na+, and K+) were also performed to check the specificity and selectivity of g-CN towards Hg2+. There was minimum or no effect of the presence of ions on the binding efficiency of Hg2+ on g-CN nanosheets. The effect of pH (2, 4, 6, 7, 8, and 10) on the binding efficiencies of Hg2+ on g-CN was also studied.  It was found that g-CN nanosheets showed enhanced binding response to Hg2+ in comparison to its bulk counterpart, which could be ascribed to the strong affinity between g-CN and Hg2+ through its -NH and -NH2 groups. This allows the detection of Hg2+ in aqueous solutions with high sensitivity and selectivity. A mercury analyzer was used in the present work to quantify Hg2+ retained on g-CN and supernatant. Such a sampling material reported an efficiency of adsorption that was equal to ~99%. Temperature and relative humidity only mildly affected the material performances. These defined nano-interwoven structures “knitting” seem to be promising candidates for mercury samplers. The nano-knitting structures seem to be promising candidates for mercury samplers, due to the strong affinity with Hg2+, and the wide adsorbing surface. These results demonstrated that the g-CN can be used as a potential candidate for detecting trace levels of Hg2+ in water and can be used as reference material for inter-laboratory comparisons.

How to cite: Chouhan, R., Gačnik, J., and Horvat, M.: Nanostructure Two Dimensional Graphitic carbon nitride as emerging passive sampler adsorbent material for efficient monitoring of Hg2+ in different matrices, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8308, https://doi.org/10.5194/egusphere-egu22-8308, 2022.

EGU22-8538 | Presentations | BG1.7

How Hg isotope source signatures can be overprinted by biogeochemical processes in the subsurface of contaminated legacy sites 

Lorenz Schwab, David S. McLagan, Lu Chen, Jan Pietrucha, Stephan M. Kraemer, Harald Biester, and Jan G. Wiederhold

Contaminated legacy sites can represent a long-term source from which mercury (Hg) is released to waterbodies, soils and the air and present a potential risk to local human and environmental health. The understanding of Hg biogeochemistry at such sites, and in the environment in general, still poses large challenges using the currently available and established analytical methods. This holds especially true for the investigation of Hg species transformation processes. The combination of multiple methods allows for a more in-depth characterization of environmental samples and can help to overcome weaknesses of individual methods and therefore improve the interpretation of mechanisms involved in the (re-)mobilization of Hg. Our recently published dataset [1] from two contaminated legacy sites demonstrates the benefit but also some limitations of integrating Hg stable isotope analysis as an additional dimension to complement analyses of Hg concentrations and binding forms. The isotopic composition of Hg can be characteristic for distinct source material as well as the extent of mass-dependent and mass-independent fractionation processes which have affected the investigated environmental sample, opening up the possibility to trace certain sources and biogeochemical processes.

In our study we present Hg stable isotope data for solid-phase digests and extracts from drill cores, complemented by analyses of Hg binding forms determined by sequential extractions and pyrolytic thermal desorption, as well as groundwater analyses downgradient from the site.

The results show that the initially highly soluble source of Hg from timber treatment by HgCl2 (kyanization) transforms to more recalcitrant Hg forms during the leaching through the soil column and the transport of Hg to groundwater. In a first step the initial sorption of Hg to the soil matrix leads to kinetic fractionation and with ongoing filling of sorption sites to equilibrium fractionation. Both processes lead to a preferential sorption of lighter isotopes. The labile Hg transported downwards in the soil column therefore has a more positive δ202Hg and thus the underlying layers exhibit a more positive δ202Hg than the highly contaminated top layers. This is supported by isotopic results of sequential extracts which show a general trend of more positive δ202Hg values for easily leachable Hg (F1+F2) compared to more tightly bound forms of Hg (F3+F4).

The transport in the groundwater contamination plume is reflected in progressively more positive liquid phase δ202Hg values compared to the solid phase as Hg is transported away from the source area. This indicates the importance of sorption of liquid phase Hg to solid phase Hg for the retention of Hg in the aquifer and the retardation of the Hg contamination plume even in matrices with very low organic matter content (<1%). The findings of our study emphasize the importance of carefully considering the overprinting of Hg isotope source signatures by biogeochemical processes in the interpretation of data from legacy sites.

[1] McLagan, D.S., Schwab, L., Chen, L., Pietrucha, J., Kraemer, S.M., Biester, H., 2022. Demystifying mercury geochemistry in contaminated soil–groundwater systems with complementary mercury stable isotope, concentration, and speciation analyses. Environ. Sci. Process. Impacts. https://doi.org/10.1039/D1EM00368B

How to cite: Schwab, L., McLagan, D. S., Chen, L., Pietrucha, J., Kraemer, S. M., Biester, H., and Wiederhold, J. G.: How Hg isotope source signatures can be overprinted by biogeochemical processes in the subsurface of contaminated legacy sites, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8538, https://doi.org/10.5194/egusphere-egu22-8538, 2022.

EGU22-12226 | Presentations | BG1.7

Total mercury and fractionation in benthic organisms from Isfjorden, Svalbard 

Ewa Korejwo, Dominika Saniewska, Jacek Bełdowski, Piotr Balazy, and Michał Saniewski

Polar regions are important in the mercury cycle. In these regions, mercury is readily deposited on the land and sea surface during a springtime Atmospheric Mercury Depletion Event (MADE). Svalbard is a system in transition, it is a region where the effects of global climate change are the most prominent. This area is also interesting because of possible mercury sources, e.g. a complex pattern of surface currents, varying geological bedrock, and recent glaciers melting. Benthic organisms, especially starfish, can be valuable bioindicators of heavy metal contamination. For that reason, in July 2018, selected benthic organisms: algae, brittle star, sea urchins, sea snails, and starfish were collected in Spitsbergen fjord. Two of the sampling stations were located in the Isfjorden, while one was outside the entrance to the fjord. Total mercury (HgTOT) was present in all organisms. The results showed that starfish are the most contaminated with mercury. Total mercury concentrations in these organisms were at least 10 times higher than in other organisms. However, they deal with harmful mercury by transporting it to the carapace. Of all the research material, starfish and sea urchins were the most effective at removing total mercury from their soft tissues (above 60% mercury in their carapace). The obtained results also show that the dominant fractions were the labile factions that are bioavailable to organisms. The largest share of these forms occurred in predatory organisms.

How to cite: Korejwo, E., Saniewska, D., Bełdowski, J., Balazy, P., and Saniewski, M.: Total mercury and fractionation in benthic organisms from Isfjorden, Svalbard, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12226, https://doi.org/10.5194/egusphere-egu22-12226, 2022.

EGU22-12477 | Presentations | BG1.7

Assessing the spatial and temporal variability of MeHg biogeochemistry and bioaccumulation in the Mediterranean Sea with a coupled 3D model 

Ginevra Rosati, Donata Canu, Paolo Lazzari, and Cosimo Solidoro

Previous research highlighted that Mediterranean tunas, as well as other edible fish species, are particularly enriched in mercury (Hg) due to a combination of physical, biogeochemical, and ecological factors that include a shallower occurrence of the MeHg concentrations maxima compared to the Ocean, likely resulting in higher phytoplankton exposure and bioaccumulation.
We developed a numerical model to simulate the fate of Hg species in the ocean, coupled with hydrodynamic transport and with the biogeochemical dynamics of nutrients, plankton, and detritus already implemented in the OGSTM-BFM model. The model is applied to a 3D domain of the Mediterranean Sea with a 1/16° horizontal resolution (~6 km) to investigate the spatial and temporal variability of MeHg distribution and bioaccumulation in the plankton food web. 
The model reproduced strong zonal gradients of MeHg concentrations related to primary production in agreement with the observations. Model results also highlight the role of winter deep convection and summer water stratification in shaping the vertical distribution of MeHg. The modeled bioaccumulation dynamics in the plankton food web are characterized by high spatial and temporal variability driven by plankton phenology. Plankton MeHg enrichment relative to water concentrations, expressed as BAF (bioaccumulation factor) is maximum for the smallest phytoplankton group (picophytoplankton) and for the group representative of carnivorous mesozooplankton. The overall content of MeHg in plankton is highest in areas of the Mediterranean Sea where picophytoplankton is abundant and MeHg water concentrations are relatively high, such as the Tyrrhenian Sea and Southern Adriatic Sea. Biomagnification is maximum in areas of higher primary production where the trophic web includes more carnivorous zooplankton, such as the Alboran Sea and the Southern Western Mediterranean Sea. 
The comparison among dynamics of different subbasins for the hindcast simulation suggests cascading effects of increasing water temperature through the decline of deep convection events in the Northern Western Mediterranean Sea that results in higher MeHg concentrations in the intermediate waters, and in turn in enhanced bioaccumulation. The model will be used to carry out long-term simulations under the climate change scenarios RCP4.5 and RCP8.5.

How to cite: Rosati, G., Canu, D., Lazzari, P., and Solidoro, C.: Assessing the spatial and temporal variability of MeHg biogeochemistry and bioaccumulation in the Mediterranean Sea with a coupled 3D model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12477, https://doi.org/10.5194/egusphere-egu22-12477, 2022.

EGU22-12959 | Presentations | BG1.7

1The 3D biogeochemical marine mercury cycling model MERCY – linking atmospheric Hg to methyl mercury in the marine food web. 

Johannes Bieser, David Amptmeijer, Ute Daewel, Joachim Kuss, and Corinna Schrum

Mercury (Hg) is a pollutant of global concern. Due to anthropogenic emissions, the global Hg burden has been ever
increasing since preindustrial times. Hg emitted into the atmosphere gets transported on a global scale and ultimately
reaches the oceans where it is transformed into highly toxic methylmercury (MeHg) that effectively accumulates along
the food chain. The international community has recognized this serious threat to human health and in 2017 regulated
Hg under the UN Minamata Convention.
Currently, the first effectiveness evaluation of the Minamata Convention on mercury is being prepared and besides
observations, models play a major role in understanding environmental Hg pathways and to predict the impact of policy
decisions and external drivers (e.g. climate, emission, and land-use change) on Hg pollution. Yet, the available model
capabilities are mostly focused on atmospheric models covering the Hg cycle from emission to deposition. With the
presented model for marine mercury cycling (MERCY) we want to contribute to the currently ongoing effort to further
our understanding of Hg and MeHg transport, transformation, and bioaccumulation in the marine environment with the
ultimate goal of linking atmospheric Hg emissions to MeHg in sea food. MERCY is the first fully resolved 3dbiogeochemical
model linking atmospheric Hg to MeHg in higher trophic levels. Most importantly, the MERCY model
is prgrammed in a way that allows for the coupling of the Hg chemistry, ecosystem, and bioaccumulation models with
most established hydrodynamic ocean models. This is achieved using the Framework for Aquatic Biogeochemical
Models (FABM).
In this talk we present the MERCY model and its application using different hydrodynamic drivers. Moreover, we
discuss its capabilities and shortcomings in reproducing the key Hg species Hg0, Hg2+, and MeHg as well as Hg loads
in biota. The presented model evaluation is a first step in establishing quality criteria for marine Hg modelling. We show
that the model can reproduce observed average concentrations of individual Hg species (normalized mean bias: HgT
(aq) -17%, Hg0 2%, MeHg -28%). Moreover, it is able to reproduce the observed seasonality and spatial patterns. We
find that the model error for HgT (aq) is mainly driven by the limitations of the physical model setup in the coastal zone
and the poor quality of data on Hg in rivers. Morover, the model error in calculating vertical mixing and stratification
contributes to the total Hg model error.
skill is in a range where further model improvements will be difficult to detect. Finally, for MeHg, we find that we are
lacking the basic understanding of the actual processes governing methylation and demethylation. Here, the model can
reproduce average concentrations but falls short in reproducing the observed value range. The results prove the
feasibility of developing marine Hg models with similar predictive capability as established atmospheric chemistry
transport models. Yet, there are still major knowledge gaps in the dynamics governing methylation and
bioaccumulation. Based on our findings we discuss these knowledge gaps and identify the major uncertainties in our
current understanding of marine Hg cycling from a modeller’s perspective.

How to cite: Bieser, J., Amptmeijer, D., Daewel, U., Kuss, J., and Schrum, C.: 1The 3D biogeochemical marine mercury cycling model MERCY – linking atmospheric Hg to methyl mercury in the marine food web., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12959, https://doi.org/10.5194/egusphere-egu22-12959, 2022.

EGU22-13296 | Presentations | BG1.7

Photochemical degradation of dimethylmercury in natural waters             

Johannes West, Sonja Gindorf, and Sofi Jonsson

Photochemical degradation of dimethylmercury (DMHg) could constitute an important source of monomethylmercury (MMHg) in surface waters, thus impacting Hg bioaccumulation and exposure risks. Despite this, few have studied this process, and no consensus has been reached on whether DMHg photodegradation occurs in nature. We used isotope labeling techniques to study DMHg and MMHg photodegradation in natural waters when exposed to artificial UV light. Our results confirm that DMHg degrades at rates comparable to those of MMHg for a variety of natural waters. We corroborated these findings in outdoor experiments, where samples containing DMHg and MMHg were exposed to natural sunlight. Comparison of the rates of photodecomposition for DMHg and MMHg in various water types imply differences in underlying reaction mechanisms for the species. To learn more about the factors controlling DMHg photodecomposition, we performed additional experiments where the effects of factors such as DOC, Cl- and O2 concentrations on DMHg and MMHg photodegradation rates were compared. Our findings indicate that the DMHg à MMHg flux through DMHg photodecomposition could represent a significant vector for MMHg production in surface oceans.

How to cite: West, J., Gindorf, S., and Jonsson, S.: Photochemical degradation of dimethylmercury in natural waters            , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13296, https://doi.org/10.5194/egusphere-egu22-13296, 2022.

EGU22-13320 | Presentations | BG1.7

Co-located ice core and sediment core records reveal climate-warming induced acceleration of mercury inputs to Lake Hazen, Nunavut, Canada 

Igor Lehnherr, Danielle Lemire, Alison Criscitiello, Cora Young, Jessica Serbu, Amila De Silva, Jane Kirk, and Stephanie Varty

Mercury (Hg) is a globally dispersed contaminant that can bioaccumulate and biomagnify in food-webs. This research uses a unique combination of measurements in an ice core and a sediment core collected within the same watershed (Lake Hazen, Nunavut, Canada) to determine how the relative importance of Hg inputs from atmospheric and terrestrial sources has changed over the last century. Hg accumulation in Lake Hazen sediment began increasing dramatically in the mid- 1990s, exhibiting a decoupling from atmospheric sources (as estimated from the ice core record), due to the increased importance of remobilized terrestrial Hg inputs to Lake Hazen. Increasing glacier melt and permafrost thaw slumping have increased the delivery of catchment Hg, via glacial rivers, into Lake Hazen. These results show that climate change is likely to slow the recovery of glacierized Arctic watersheds from Hg contamination, countering the anticipated benefit from recent international efforts to reduce anthropogenic Hg emissions.

How to cite: Lehnherr, I., Lemire, D., Criscitiello, A., Young, C., Serbu, J., De Silva, A., Kirk, J., and Varty, S.: Co-located ice core and sediment core records reveal climate-warming induced acceleration of mercury inputs to Lake Hazen, Nunavut, Canada, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13320, https://doi.org/10.5194/egusphere-egu22-13320, 2022.

In some areas of the Russian Arctic pronounced manifestations of thermal degradation of the permafrost are observed, which can cause an increase in the mercury input into the atmosphere of the Arctic and its further distribution in terrestrial and aquatic ecosystems. Wet scavenging by precipitation events is one of the main ways of Hg removing from the atmosphere. Here we present a study of Hg in wet precipitation on the territory of the Yamal-Nenets Autonomous Area (YNAA) based on the data obtained at the Nadym monitoring stations. Seasonal and annual volume-weighted concentrations (VWC) and fluxes of Hg were determined to assess differences in cold and warm periods and factors influencing these changes. The maximum values in wet precipitation samples were found in the spring, most likely associated with the AMDE phenomenon that contributed from 9.8% to 16.7% in the total annual wet precipitation.

The average annual VWC in wet atmospheric precipitations in Nadym is comparable with the values obtained for other urbanized regions of the world; however, it is much higher than the values reported for remote Arctic places. On the other hand, the annual flux of mercury deposition in Nadym is comparable to remote areas of the Arctic zone but less than annual fluxes in continental-scale monitoring networks of other parts of the world.

There are several main possible sources of mercury in the YNAA: transboundary transport with air masses, regional atmospheric emissions of mercury from fires, and significant regional and local inputs from gas and oil combustion by power plants and factories. In addition, since air temperature and the thickness of the seasonally thawed layers were raised substantially in 2018, the increase of Hg flux in the warm period might also reflect regional input due to the re-emission of Hg from soils.

Keywords: mercury; Arctic; atmospheric wet precipitation; deposition fluxes; AMDE; permafrost thawing.

How to cite: Eyrikh, S., Shol, L., and Shinkaruk, E.: Sources, concentrations and fluxes of mercury wet deposition on the territory of Russian Arctic (a case study in Yamal-Nenets Autonomous Area), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13492, https://doi.org/10.5194/egusphere-egu22-13492, 2022.

The samples of atmospheric precipitation were taken at the monitoring site on the roof of the Institute for Water and Environmental Problems, located within Barnaul city, at the height of 25 meters. Totally 578 samples of unfiltered atmospheric precipitation were analyzed. All sample preparation and analysis procedures were performed in a "clean room" using purified reagents to avoid pollution. The total mercury concentrations were determined in unfiltered samples by US EPA method 1631 using the analyzer "Mercur DUO Plus" (Analytik Jena, Germany). The limit of detection was 0.4 ng/L.

The widest range of Hg concentrations was observed in snow, the most narrow – in the rain. Comparison of average annual volume-weighted concentrations (VWC) demonstrated that minimum Hg concentrations were detected in 2015/2016; the maximum one – in 2018/19. Annual deposition fluxes ranged from 2.3 to 5.1 µg/m2; the average value for 5 years was 3.8 µg/m2. Average VWCs of Hg in atmospheric precipitation of Barnaul are on a comparable level with other urbanized areas of the world. However, annual Hg fluxes are lower than in other regions. There is a high positive correlation (0.87) of Hg fluxes with the amount of precipitation in cold periods, which indicates the constant pollution, primarily the emissions from coal combustion, one of the largest sources of Hg released into the atmosphere. In the warm periods, the correlation coefficient is 0.24 due to a wide variety of sources of mercury in these periods.

Keywords: mercury; atmospheric wet precipitation; deposition fluxes.

How to cite: Shol, L. and Eyrikh, S.: Mercury in atmospheric precipitation of Eastern Siberia: seasonal and interannual variability of concentrations and fluxes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13494, https://doi.org/10.5194/egusphere-egu22-13494, 2022.

EGU22-1532 | Presentations | BG1.8

The YAM seep area – an active carbonate-paved gas seep field at the accretionary margin SW offshore Taiwan 

Yiting Tseng, Miriam Römer, Thomas Pape, Tzu-Ting Chen, Saulwood Lin, Christian Berndt, and Gerhard Bohrmann

The YAM seep area is an active gas seep region among the widespread seep sites offshore south-western Taiwan. The seep area covers a seafloor region of 49,000 m2 at the northern crest of Four-Way Closure Ridge in 1,347 m water depth. During several research cruises (ORI-1163, SO266), shipborne and AUV-related hydro-acoustic investigations revealed that the area of seepage is well documented by high backscatter and a changing micro-bathymetry between rough and flat in the otherwise very flat seabed in the area. 
During expedition SO266, RV Sonne, gas emission sites were observed at the center and eastern flank of the area using ship-borne multi-beam data in the water column. Seawater methane concentrations above the seafloor were collected from the middle west to east of the central transect, revealing concentrations ranging 5.5-18.2 nmol/L with general higher methane concentrations at the rim of the area. Authigenic carbonate samples were collected during gravity coring and MeBo drilling. MeBo drilling was stopped below 5 mbsf because of continuous release of free gas out of the borehole. Carbon isotope measurements of the carbonates showed δ13C values between -38.25 to -52.17 ‰, indicating a mixing of biogenic and thermogenic gas in the methane-derived carbonates. Seismic investigations of the Four-Way Closure Ridge show a well-defined fault below the ridge crest which extends from below the gas hydrate stability zone to the seafloor and acts as a pathway for the methane ascent to the seafloor. 
Seafloor observation using a TV-sled showed a seafloor paved by carbonate rocks consisting of different featured crusts, slabs, and irregular build-ups. Thin-layered crusts were mainly observed at the paved area's rim, while thick-layered slabs and free-standing build-ups were the main features at the elevated region. Chemosynthetic communities, like mussels and clams, mainly were observed within certain carbonate fractures. At the same time, other animals, bacterial mats, and tube worms are presented generally along the whole survey path among the rough seep area. Hydro-acoustic data correlated with visual observation results indicate wide variation through the region of the seep area. Based on our interpretation, the YAM seep area developed over a longer time at the crest of the accretionary ridge, seepage, uplifting of the ridge, tectonic fracturing, and seafloor erosion highly influenced the seafloor manifestation.

How to cite: Tseng, Y., Römer, M., Pape, T., Chen, T.-T., Lin, S., Berndt, C., and Bohrmann, G.: The YAM seep area – an active carbonate-paved gas seep field at the accretionary margin SW offshore Taiwan, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1532, https://doi.org/10.5194/egusphere-egu22-1532, 2022.

EGU22-3932 | Presentations | BG1.8

Paleo-gas hydrate distribution associated with hill-hole pair formation in the SW Barents Sea 

Claudio Argentino, Kate Alyse Waghorn, Monica Winsborrow, Stefan Bünz, and Giuliana Panieri

Today, gas hydrates are predicted to be stable only in the deepest parts of the Barents Sea, however under past glaciations, low pressure, high temperature subglacial conditions would have been an ideal setting for their formation. Multiple studies have documented the storage of methane beneath the Late Weichselian Barents Sea Ice Sheet, and its subsequent release following deglaciation. Furthermore, it has been hypothesised that localised subglacial gas hydrate formation increases frictional resistance at base of the ice and thus may regulate the flow of overlying ice (Winsborrow et al. 2016). This hypothesis has however, never been tested against sedimentological records of paleo-fluid flow and sediment properties.  

Here we present preliminary results on sediment and pore fluid geochemistry from nine gravity cores collected from Ingøydjupet in the SW Barents Sea. These were collected around a hill-hole pair, a glacial landform indicative of variations in subglacial frictional resistance. One of several suggested formation processes is gas hydrate stiffening of subglacial sediments.  

At present, there is a clear difference in methane fluxes between the areas inside the seafloor hole (high fluxes) and the adjacent hill (low fluxes), matching the distribution of a localized subsurface shallow gas accumulation visible in seismic data. Sediment geochemistry revealed a past episode of enhanced upward methane fluxes only recorded in sediments from the hole, resulted in the shoaling of the sulfate-methane transition and precipitation of methane-derived authigenic carbonates (MDAC) with δ13C= -35 ‰. Although the oxygen isotopic composition (δ18O) of MDACs collected from a sediment core in the hole did not show direct evidence for past gas hydrate destabilization, the reconstructed history of methane fluxes as well as the present-day fluxes and subsurface gas distribution support the hypothesis of a differential distribution of subglacial paleo-gas hydrates across the hill-hole pair, possibly controlled by stratigraphic and structural preconditioning.

This research is part of the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) supported by the Research Council of Norway through its Centres of Excellence funding scheme grant No. 223259.

Winsborrow, M., Andreassen, K., Hubbard, A., Plaza-Faverola, A., Gudlaugsson, E. and Patton, H., 2016. Regulation of ice stream flow through subglacial formation of gas hydrates. Nat. Geosci., 9(5), 370-374.

How to cite: Argentino, C., Waghorn, K. A., Winsborrow, M., Bünz, S., and Panieri, G.: Paleo-gas hydrate distribution associated with hill-hole pair formation in the SW Barents Sea, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3932, https://doi.org/10.5194/egusphere-egu22-3932, 2022.

EGU22-4505 | Presentations | BG1.8

Slope instabilities and gas hydrates dissociation in the western Black Sea since the last glacial maximum 

Maud Fabre, Lies Loncke, Vincent Riboulot, Nabil Sultan, and Stephan Ker

Marine landslides, which are observed worldwide along continental slopes, constitute the most important processes reworking sedimentary deposits and a major geohazard for marine and coastal domains. They can generate potentially the destruction of marine infrastructures through the formation of turbidity currents and/or hazardous tsunamis. In the Romanian sector of the Black Sea, high amounts of methane are detected in the sediments and at the seafloor through the identification of gas seeps in the water column. They occur on the upper slope, mostly outside the large gas hydrates system occurring in the sediment below -660 m water depth, where methane is trapped in ice cages that act as a buffer zone hampering methane to reach the water column. New geophysical and geotechnical dataset acquired along the Romanian margin reveals that the active seepage zone is associated with numerous slope failures, which incised the continental upper slope. Is there a possible relationship between gas hydrate system and recent slope instabilities? Could intense free gas emissions and/or gas hydrates dissociation have triggered such geohazards? To answer these questions, we present (1) an high resolution mapping and, more important, dating of landslides since the last glacial maximum (35 ka), (2) results of numerical modelling showing the evolution of gas hydrates stability zone inside the sediments since the last 35 ka taking into account the environmental variations that occurred during this time lapse (geothermic gradient, temperature, salinity and sea level).

The models highlight the major effect of environmental changes and particularly the glacial/interglacial cycles and salinity variations on the extent of the gas hydrates. The confrontation of those models with slide extensions, depths and ages allows to better discuss the respective influences of gas hydrates dissociation, stratigraphic overpressure and seepage on slope instability since the last glacial maximum.

How to cite: Fabre, M., Loncke, L., Riboulot, V., Sultan, N., and Ker, S.: Slope instabilities and gas hydrates dissociation in the western Black Sea since the last glacial maximum, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4505, https://doi.org/10.5194/egusphere-egu22-4505, 2022.

EGU22-6546 | Presentations | BG1.8

The potential of Nd isotopes in disentangling fluid sources at hydrocarbon seeps: a recent perspective 

Michał Jakubowicz, Luis Agirrezabala, Steffen Kiel, James Goedert, Jolanta Dopieralska, and Zdzislaw Belka

In recent years, Nd isotopes have seen increasingly common use in studies of hydrocarbon seeps. Given the distinct Nd isotope signature of mafic igneous rocks, particular emphasis in these investigations has been on reconstructing former interactions between the seeping fluids and volcanic materials. The results of our case studies on ancient seeps underlain by mafic volcanic bodies, including Cretaceous seep carbonates of the Outer Carpathians (Czech Republic) and Basque-Cantabrian Basin (Spain), as well as Eocene seeps of the Cascadia convergent margin (Washington) consistently document their significant enrichment in volcanogenic Nd, reflected in their increased Nd isotope ratios (εNd values). The extent of this 143Nd-enrichment varies depending on the geological context of given seeps, most notably the εNd signatures and thickness of the volcanics and overlying sedimentary piles, and the Nd isotope signal of background local pore waters. The highest εNd values are observed in seep carbonates very shallowly underlain by thick mafic volcanics: the Cretaceous seep of the Carpathians and Eocene seeps of Cascadia. For the former, the εNd values are up to 7.5 units higher than the signature of coeval non-seep pore water, whereas for the latter the εNd values are as high as +1.9, close to the highest value ever recorded for seawater. More moderate 143Nd-enrichment typifies the Cretaceous seeps of Spain, for which the volcanic intrusions were emplaced at considerable depths below the seafloor. In such cases, the Nd isotope signature of the fluid-volcanic interactions was partially obscured by subsequent interactions between the fluids and the overlying sediments. Rather than focusing solely on exploring the new geochemical tool, the primary aim of our studies was to address broader questions regarding the tectonic architecture and geological history of the sedimentary basins that host given seep deposits. For the Eocene seeps of Washington, the Nd isotope data served to document interactions between the methane-rich fluids and the volcanic terrane of Siletzia, which underlies the Cascadia forearc; these results placed important stratigraphic and structural constraints on the activation and earliest history of convergence in Cascadia, following Siletzia accretion. For the studied Cretaceous seeps, all hosted by early, sediment-covered rifts, the studies demonstrated that Nd isotopes offer a valuable new tool of deconvolving methane fluxes from different organic matter alteration pathways for the very complex, sedimentary-magmatic systems of incipient rifts. At the same time, these studies emphasized important limitations of Sr isotopes, the system most commonly used to document interactions between the seeping fluids and igneous rocks. Because of the much higher Sr/Nd ratios observed in pore waters than in igneous rocks, the potential of Sr isotopes to record fluid-volcanic interactions is considerably lower than that of Nd isotopes. Thus, broader use of Nd isotopes can assist in identifying potential volcanogenic fluid endmembers for the numerous sedimented rifts for which evidence for magmatic involvement in the fluid expulsion remains equivocal.

This work was supported by the National Science Centre, Poland, grant No. 2016/23/D/ST10/00444

How to cite: Jakubowicz, M., Agirrezabala, L., Kiel, S., Goedert, J., Dopieralska, J., and Belka, Z.: The potential of Nd isotopes in disentangling fluid sources at hydrocarbon seeps: a recent perspective, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6546, https://doi.org/10.5194/egusphere-egu22-6546, 2022.

EGU22-7382 | Presentations | BG1.8

Methane emissions from abandoned wells? A German case study 

Sebastian F. A. Jordan, Stefan Schlömer, Martin Krüger, and Martin Blumenberg

Methane recently became the focus of attention as the target to slow global warming in the near future. Hence, measures to reduce anthropogenic methane emission are globally discussed and researchers test methods to actively reduce atmospheric methane levels. Complicating advancement in this field, there are still high uncertainties associated with methane sources and sinks. One example is the methane emission from abandoned oil and gas wells. The USA, with about 4,000,000 abandoned wells, is the only country worldwide to include emissions from these wells in their yearly greenhouse gas emissions inventory. Studies estimated that these emissions account for about 1–13% of the U.S. energy sector (Williams et al. 2021). In addition to the USA, only a few countries like Canada, the United Kingdom and the Netherlands collected data on methane emissions from abandoned gas wells. Currently Germany has about 20,000 abandoned wells (formerly productive and dry wells) of different ages, which were generally filled and buried and since 1950s officially have to be plugged, cut, and buried at the end of their lifecycle. It is unclear, whether they are emitting methane or not.

Here, we present our project to fill this knowledge gap for Germany and focus on onshore-abandoned oil & gas wells and their potential to emit methane. Therefore, we will measure soil-atmosphere methane fluxes at several abandoned wells exemplary in four regions of Lower Saxony (Federal State in Northern Germany). In case of methane emission to the atmosphere, we will determine the origin of the methane in soil gas at 1 m depth by isotopic analyses. In addition to these analyses in the direct vicinity of the boreholes, we will investigate the surrounding natural methane situation in groundwater and soil with the help of molecular-geomicrobiological methods and determinations of methane oxidation rates.

 

 

Williams, J. P., Regehr, A., & Kang, M. (2021). Methane Emissions from Abandoned Oil and Gas Wells in Canada and the United States. Environ Sci Technol, 55(1), 563-570. https://doi.org/10.1021/acs.est.0c04265

How to cite: Jordan, S. F. A., Schlömer, S., Krüger, M., and Blumenberg, M.: Methane emissions from abandoned wells? A German case study, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7382, https://doi.org/10.5194/egusphere-egu22-7382, 2022.

EGU22-7597 | Presentations | BG1.8

Biomarker evidence for bacterial oxidation of oil-derived hydrocarbons at seeps in the southern Gulf of Mexico 

Nicola Krake, Daniel Birgel, Daniel Smrzka, Jennifer Zwicker, Huiwen Huang, Dong Feng, Gerhard Bohrmann, and Jörn Peckmann

Hydrocarbon seepage is a widespread phenomenon at continental margins around the world. The composition of the ascending fluids can be variable, consisting of short- and long-chain hydrocarbons as well as crude oil. A prominent site of oil seepage is the Bay of Campeche in the southern Gulf of Mexico. The seepage of petroleum is known to have an inhibiting effect on life at seeps, but short- and long-chain hydrocarbons have been shown to be degraded by a range of heterotrophic sulfate-reducing bacteria. Here we present lipid biomarker and carbon isotope data from authigenic carbonates from the Campeche Knolls in the southern Gulf of Mexico. The Campeche carbonates display d13C values in the range of -31.3‰ to -21.9‰, which is in accord with carbon derived from oil-derived hydrocarbons. Interestingly, the Campeche carbonates contain particularly high amounts of bacterial non-isoprenoidal ether lipids (DAGEs) with a wide variety of alkyl chain lengths. The bacterial biomarkers show heavier carbon isotopic signatures than their counterparts at methane seeps. These data allow for the characterization of bacterial oxidation of oil-derived hydrocarbons in modern and, in cases of moderate to good biomarker preservation, ancient environments, permitting the assessment of the influence of different fluid chemistries on the composition of chemosynthesis-based communities at seeps.

How to cite: Krake, N., Birgel, D., Smrzka, D., Zwicker, J., Huang, H., Feng, D., Bohrmann, G., and Peckmann, J.: Biomarker evidence for bacterial oxidation of oil-derived hydrocarbons at seeps in the southern Gulf of Mexico, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7597, https://doi.org/10.5194/egusphere-egu22-7597, 2022.

EGU22-9510 | Presentations | BG1.8

Gas Flares of the Norwegian Arctic - Sources and distribution: A comprehensive mapping using MAREANO multibeam data 

Shyam Chand, Terje Thorsnes, Valérie Bellec, and Lilja Rún Bjarnadóttir

Gas flares from natural sources of hydrocarbon gases escaping through the seafloor to the water column is a phenomenon observed in many parts of the World’s Oceans. The occurrence of these acoustically and visually observed seepages have been recorded by using various sensors onboard different platforms. But the use of multibeam echosounder systems, with the capability of recording the whole water column acoustic backscattering, in recent years have given the opportunity to cover large areas in a short time span along with bathymetric mapping in a cost-effective way. Even though the data sizes are multiple orders of magnitude larger, the use of dedicated software’s and high-performance processing systems have given the opportunity to find acoustic anomalies resulting from the streaming of gas bubbles in water column.

The MAREANO programme which is aimed at mapping habitats through various methods has surveyed large areas of the Norwegian Arctic using multibeam systems. This has resulted in the acquisition of water column acoustic data covering a large area of Arctic Norway over in the last decade. These data have been interpreted and analysed together with other geological and ancillary data from other sensors such as photo/video observations, backscatter data, etc. leading us to relate these anomalies to various structural and geological formations. The database also gave us an opportunity to compare the differences between some of the multibeam systems in capturing these acoustic anomalies. More than approximately 5000 flares of varying magnitude and sizes were detected based on MAREANO water column data, in an area of about 139000 km2. We present the results from these comprehensive surveys and discuss various possibilities that such a database can provide for present and future understanding in the development of Arctic. 

How to cite: Chand, S., Thorsnes, T., Bellec, V., and Bjarnadóttir, L. R.: Gas Flares of the Norwegian Arctic - Sources and distribution: A comprehensive mapping using MAREANO multibeam data, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9510, https://doi.org/10.5194/egusphere-egu22-9510, 2022.

EGU22-13090 | Presentations | BG1.8

Significance of micro-and macrofauna from seeps along the Israeli coast (Palmahim Disturbance). 

Valentina Beccari, Daniela Basso, Giuliana Panieri, Ahuva Almogi-Labin, Yizhaq Makovsky, Irka Hajdas, and Silvia Spezzaferri

Cold seeps are important biodiversity hotspots, which support unique communities in the deep sea. The occurrence of living or fossil chemosymbiotic molluscs and low oxygen tolerant benthic foraminifera in the sediments, in association with other seepage related features (e.g. aragonite, authigenic carbonate crusts) are important indications of active or past fluid seepage.
The EU Eurofleets2 SEMSEEP Cruise on the R/V Aegaeo along the Israeli coasts (2016) provided sea floor data and sediments for this study.
Three deep-sea cores from representative environments from the Palmahim Disturbance, (coral-transition area, pockmark area and Gal-C channel area) spanning the last 5000 BP were investigated for pteropods, benthic foraminifera and molluscs and cross-analysed with ROV videos and surface samples.
The coral-transition core (AG16-20-BC1b) shows a sharp increase in low-oxygen benthic foraminifera (representing 100% of the faunal assemblage), no agglutinants, pyritized tubes and euhedral gypsum crystals in its bottom part. This evidence together with the low values of δ13C of C. oolina give indication that a short-lived advective fluid flux occurred approximatively at 3500 BP. Only few small individuals of the chemosymbiotic bivalve Isorropodon perplexum Sturany, 1896 have been observed above this interval, showing that the chemosynthetic environment was not conducive for the development of a full chemosymbiotic benthic community.
Similarly, evidences of methane emission have been observed in the pockmark core (AG16-23-BC2). Pteropods molds, composed by aragonite needles and High-Mg calcite crystals are present at the base of the core. Aragonite precipitates during advective emissions, when the Sulfate Methane Transition Zone (SMTZ) is located cm to dm below the seafloor, therefore the presence of pteropod molds recrystallized in aragonite is an important evidence that an advective emission occurred. However, these molds co-occur with authigenic carbonate crusts, shrimp claws, low-oxygen tolerant benthic foraminifera and a mature association of chemosymbiotic molluscs (including vesicomyids, lucinids, mytilids and thyasirids). Typically, these organisms are sustained by a moderate, diffusive, pervasive and persistent fluid flow. Therefore, we suggest that this environment was dynamic and supporting advective and diffusive emissions that were able to sustain recruitment and development of mature chemosymbiotic faunal assemblage. 

This research was funded by the Swiss National Science Foundation (SNSF) project Ref. 200021_175587, samples were collected during the EUROFLEETS2 SEMSEEP cruise that was funded by the European Union FP7 Programme under grant agreement n° 312762.

How to cite: Beccari, V., Basso, D., Panieri, G., Almogi-Labin, A., Makovsky, Y., Hajdas, I., and Spezzaferri, S.: Significance of micro-and macrofauna from seeps along the Israeli coast (Palmahim Disturbance)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13090, https://doi.org/10.5194/egusphere-egu22-13090, 2022.

EGU22-13267 | Presentations | BG1.8

Using ROV video photogrammetry to reconstruct seafloor landforms of Arctic cold seep environments 

Luca Fallati, Alessandra Savini, Claudio Argentino, Stefan Bünz, and Giuliana Panieri

Cold seeps are locations on the seafloor where reduced compounds from subsurface hydrocarbon reserves enrich sediment fluids or emanate freely as gas from the seabed. Associated with these spots, numerous underwater landscapes and various chemosynthetic communities were uncovered during the last decades of seafloor exploration. 

Arctic cold seeps offshore Svalbard were explored using Ægir6000, a work-class ROV (Remotely Operated Vehicle) equipped with three HD video cameras that filmed the ocean floor at different angles. The ROV, moving at a constant speed of 1 knot, followed predefined routes to guarantee optimal lateral overlap between adjacent transects. From the videos of the nadiral camera, a photogram every two seconds was automatically extracted. Then, the images were processed in Agisoft Metashape® following a well-established photogrammetry workflow. As final outputs, we obtained 3D mesh, orthomosaics and DTMs at ultra-high-resolution (mm) allowing us to obtain detailed morphometric maps.

These data allowed us to reconstruct accurate georeferenced 3D models representing a variety of small-scale (sub-cm) seabed features and provide essential information for a better understanding of the spatial pattern associated with submarine biogeochemical and physical processes at the seafloor. Moreover, the realized models present the locations where push corers were collected. This correspondence will allow us to integrate fine-scale habitat mapping and pore fluid datasets to quantify the areal methane fluxes.

This work was supported by the Research Council of Norway, for AKMA - Advancing Knowledge on Methane in the Arctic, project number 287869.

Keywords: Submarine geomorphology, ROV, Underwater 3D Photogrammetry, optical 3D models, Cold Seeps, Arctic Ocean

How to cite: Fallati, L., Savini, A., Argentino, C., Bünz, S., and Panieri, G.: Using ROV video photogrammetry to reconstruct seafloor landforms of Arctic cold seep environments, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13267, https://doi.org/10.5194/egusphere-egu22-13267, 2022.

Wet deposition has been identified as a critical impactor for the modelling of 137Cs in the Fukushima Daiichi Nuclear power plant (FDNPP) accident. However, it is difficult to simulate due to the involvement of close interaction between various complicated meteorological and physical processes during the wet deposition process. The limitation of measurement of the in-cloud and below-cloud scavenging also contribute to the uncertainty in wet deposition modeling, leading to the great variation of 137Cs wet deposition parameterization. These variations can be amplified further by inaccurate meteorological input, making simulation of radionuclide transport sensitive to the choice of wet scavenging parameterization. Moreover, simulations can also be influenced by differences between radionuclide transport models, even if they adopt similar parameterization for wet scavenging. Although intensively investigated, wet deposition simulation is still subject to uncertainties of meteorological inputs and wet scavenging modeling, leading to biased 137Cs transport prediction.

To improve modeling of 137Cs transport, both in- and below-cloud wet scavenging schemes were integrated into the Weather Research and Forecasting-Chemistry (WRF-Chem) model, yielding online coupled modeling of meteorology and the two wet scavenging processes. Overall, 25 combinations of different in- and below-cloud scavenging schemes of 137Cs, covering most wet scavenging schemes reported in the literature, were integrated into WRF-Chem. Additionally, two microphysics schemes were compared to improve the simulation of precipitation. These 25 models and the ensemble mean of 9 representative models were systematically compared with a previous below-cloud-only WRF-Chem model, using the cumulative deposition and atmospheric concentrations of 137Cs measurements. The findings could elucidate the range of variation among these schemes both within and across the five in-cloud groups, reveal the behaviors and sensitivities of different schemes in different scenarios.

The results revealed that the Morrison's double moment cloud microphysics scheme improves the simulation of rainfall and deposition pattern. Furthermore, the integration of the in-cloud schemes in WRF-Chem substantially reduces the bias in the cumulative deposition simulation, especially in the Nakadori and Tochigi regions where light rain dominated. For atmospheric concentration of 137Cs, those models with in-cloud schemes that consider cloud parameters showed better and more stable performance, among which Hertel-Bakla performed best for atmospheric concentration and Roselle-Apsimon performed best for both deposition and atmospheric concentration. In contrast, the in-cloud schemes that rely solely on rain intensity were found sensitive to the meteorological conditions and showed varied performance in relation to the plume events examined. The analysis based on the spatial pattern shows that the Roselle scheme, which considers cloud liquid water content and depth, can achieve a more balanced allocation of 137Cs between the air and the ground in these two cases than that achieved by the empirical power function scheme Environ. The ensemble mean achieves satisfactory performance except for one plume event, but still outperforms most models. The range of variation of the 25 models covered most of the measurements, reflecting the reasonable capability of WRF-Chem for modeling 137Cs transport.

How to cite: Zhuang, S., Dong, X., and Fang, S.: Sensitivity analysis on the wet deposition parameterization for 137Cs transport modeling following the Fukushima Daiichi Nuclear Power Plant accident, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-177, https://doi.org/10.5194/egusphere-egu22-177, 2022.

The nuclear emergency response for accidental release around the nuclear power plant site (NPPs) requires a fast and accurate estimate of the influence caused by gaseous hazardous pollutants spreading, which is critical for and preventing protecting lives, creatures, and the environment. However, as usual, the NPPs is consist of dense buildings and multi-type terrain, e.g. river and mountain, which poses challenges to atmospheric dispersion calculation for response tasks. Micro-SWIFT SPRAY (MSS) comprises both the diagnostic wind model and the dispersion model, which enables the airflows and atmospheric dispersion simulation with the meteorological and other inputs. For a small-scale scenario, especially, the separate module for obstacles influence modeling provides the potential capability of precise atmospheric dispersion. But the error behavior of such a scenario around a nuclear power plant site with complex topography remains to be further demonstrated. In this study, MSS is comprehensively evaluated against a wind tunnel experiment with a 1:600 scale for the small-scale (3 km × 3km) atmospheric dispersion modeling. Tens of buildings located in this scenario of a NPPs surrounded by a mountain and river. The evaluations for diagnostic wind modeling include the speed, direction, and distribution of horizontal airflows and vertical profile of speed at a representative site. And for the concentration calculation, horizontal distribution, axis profile, and vertical profile at a representative site. The results demonstrate the MSS can reproduce fine airflows near the buildings but overestimate the wind speed. The maximum deviation of vertical speed is around 2.09 m/s at the representative site. The simulated plume of concentration reproduces the highest concentration place and matches the observations well. The axis profile of concentration is underestimated and the vertical profile displays an increasing deviation with the height increase. Compared with the observations, the FAC5 and FAC2 of concentration simulation reach 0.945 and 0.891 in the entire calculation domain, which convinces the performance of MSS in small-scale modeling.

How to cite: Dong, X., Zhuang, S., and Fang, S.: Micro-SWIFT SPRAY modeling of atmospheric dispersion around a nuclear power plant site with complex topography, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-190, https://doi.org/10.5194/egusphere-egu22-190, 2022.

EGU22-666 | Presentations | GI2.3

Dry deposition velocity of chlorine 36 on grassland 

Sourabie Deo, Didier Hebert, Lucilla Benedetti, Elsa Vitorge, Beatriz Lourino Cabana, Valery Guillou, and Denis Maro

Chlorine 36 (36Cl, T1/2 = 301,000 years) is a radionuclide with natural and anthropogenic origin that can be rejected accidentally during decommissioning of nuclear power plants or chronically during recycling of nuclear waste. Once emitted into the atmosphere, 36Cl (gas and particles) can be transferred to the soil and vegetal cover by dry and wet deposition. However, knowledge of these deposits is very scarce. Because of its relatively high mobility in the geosphere and its high bioavailability, 36Cl fate in the environment should be studied for environmental and human impact assessments. So, the objective of this work is to determine the dry deposition rates of chlorine 36 on grassland. Grass is studied, as it is a link in the human food chain via cow's milk.

In order to achieve this objective, a method for extracting the chlorine contained in plant leaves has been developed. This method consists in heating the dried and grounded plant sample in presence of sodium hydroxide. A temperature gradient up to 450°C allows the extraction to be carried out in two stages: (i) The chlorides with a strong affinity for alkaline environments are first extracted from the plant and preserved in sodium hydroxide; (ii) The organic matter is then destroyed by combustion and the sodium hydroxide crystallised. Brought out from the oven, the dry residue is dissolved in ultrapure water and chemically prepared for the measurement of chlorine 36. This extraction method was validated by its application to NIST standards of peach and apple leaves. The average extraction efficiency of chlorides was 83 ± 3%.

For the determination of dry deposition rates, 1m2 of grass was exposed every 2 weeks at the IRSN La Hague technical platform (PTILH) located 2 km downwind from Orano la Hague, a chronic source of low-level chlorine 36 emissions. A mobile shelter with automatic humidity detection covered the grass during rainy episodes. In proximity to the grass, atmospheric chlorine was also sampled at the same frequency as the grass. Gaseous chlorine was sampled by bubbling in sodium hydroxide and by an AS3000 sampler containing activated carbon cartridge. Particulate chlorine was collected on a composite (teflon and glass fibre) filter. Chlorine 36 was measured by accelerated mass spectrometry ASTER (Accelerator for Earth Sciences, Environment and Risks) at CEREGE, Aix-en-Provence, France. All samples were subjected to a succession of chemical preparations in order to remove the sulphur 36 (an isobaric interferent) and to collect the chlorides in the form of AgCl pastilles. The results show a chlorine 36 deposition flux on the grass of 2.94.102 at/m2.s with a deposition velocity in dry weather vd(gas+particles) = 8.10-4 m/s for a contribution of 65.5% of particulate chlorine 36 and 34.5% of gaseous chlorine 36. Based on these experimental results, a modelling of the dry and wet deposits will be carried out considering the parameters related to the canopy and the atmospheric turbulence.

How to cite: Deo, S., Hebert, D., Benedetti, L., Vitorge, E., Lourino Cabana, B., Guillou, V., and Maro, D.: Dry deposition velocity of chlorine 36 on grassland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-666, https://doi.org/10.5194/egusphere-egu22-666, 2022.

EGU22-1235 | Presentations | GI2.3

Modeling the depth dependence of Cs-137 concentration in Lake Onuma 

Yuko Hatano, Kentaro Akasaki, Eiichi Suetomi, Yukiko Okada, Kyuma Suzuki, and Shun Watanabe

Lake Onuma on Mt. Akagi (Gunma Prefecture, Japan) is a closed lake with an average water residence time of 2.3 years. The activity concentration of radioactive cesium in the lake was high shortly after the Fukushima accident. According to Suzuki et al. [1] and Watanabe [2], after a filtration process, Cs-137 are separated into two groups: particulate form and dissolved form. These two forms appears to have very different concentration profiles with each other,  when the Cs-137 concentration plotted against the sampled water depths. In the present study, we are going to model those behavior of particulate/dissolved forms with an emphasis on the depth dependency.

We consider a creation-annihilation process of plankton for the model of the particulate form, since diatom shells are found to be a major constituent of the particulate Cs-137 [2]. We set  ∂P/∂t = f(x,t)  and  f(x,t) = χ(x) cos(ωt) (0 ≤ x ≤ L(water column height), t > 0),  where P=P(x,t) is the activity concentration of the particulate form. The term f(x,t) is the rate of the net production of the plankton at a specific location x at a specific time t. Seasonal cycle is also taken into account by the cosine function (we neglect the phase shift here). The function χ(x), depends solely on water depth x, is responsible for dynamics or inhomogeneity of lake water, such as circulation, stratification or a thermocline. We assume that such a water structure relates to the production rate of plankton through the function χ(x). Thus, we may obtain the concentration of particulate Cs-137. For the dissolved concentration S(x,t), we use the classical diffusion equation with the diffusivity K being dependent on both space and time (i.e. K(x,t)), namely ∂S/∂t =  ∇•(K(x,t) ∇S). Here S=S(x,t) is the activity concentration of the dissolved form. The total activity concentration C(x,t) is the sum of P(x,t) and S(x,t). Using the pair of the equations, we can reproduce the followings. (1) depth profiles of each of the soluble- and particulate activity concentration and (2) depth profiles of the total Cs-137 concentration.

 [1] Suzuki, K. et al., Sci. Tot. Env. (2018)

 [2] Watanabe, S. et al.,  Proc. 20th Workshop on Environmental Radioactivity (2019)

How to cite: Hatano, Y., Akasaki, K., Suetomi, E., Okada, Y., Suzuki, K., and Watanabe, S.: Modeling the depth dependence of Cs-137 concentration in Lake Onuma, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1235, https://doi.org/10.5194/egusphere-egu22-1235, 2022.

EGU22-3340 | Presentations | GI2.3

Factors controlling the dissolved 137Cs seasonal fluctuations in the Abukuma River under the influence of the Fukushima Nuclear Power Plant accident 

Yasunori Igarashi, Nanb Kenji, Toshihiro Wada, Yoshifumi Wakiyama, Yuichi Onda, and Shota Moritaka

The 2011 Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released large amounts of radioactive materials into the environment. River systems play an important role in the terrestrial redistribution of FDNPP-derived 137Cs in association with water and sediment movement. We examined the seasonal fluctuations in dissolved and particulate 137Cs activity concentrations and clarified the biological and physicochemical factors controlling 137Cs in the Abukuma River’s middle course in the region affected by the FDNPP accident. The results showed the water temperature and K+ concentration dominated the seasonality of the dissolved 137Cs activity concentration. We concluded that the 137Cs in organic matter is not a source of dissolved 137Cs in river water. The study also revealed the temperature dependence of Kd in riverine environments from a Van ’t Hoff equation. The standard reaction enthalpy of 137Cs in the Abukuma River was calculated to be approximately −19.3 kJ/mol. This was the first study to clearly reveal the mechanisms by which the dissolved 137Cs activity concentration and Kd are influenced by chemical and thermodynamic processes in the middle course of a large river, and it is expected to lead to an improved model of 137Cs dynamics in rivers.

How to cite: Igarashi, Y., Kenji, N., Wada, T., Wakiyama, Y., Onda, Y., and Moritaka, S.: Factors controlling the dissolved 137Cs seasonal fluctuations in the Abukuma River under the influence of the Fukushima Nuclear Power Plant accident, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3340, https://doi.org/10.5194/egusphere-egu22-3340, 2022.

EGU22-3442 | Presentations | GI2.3

A comparative study of riverine 137Cs dynamics during high-flow events at three contaminated river catchments in Fukushima 

Yoshifumi Wakiyama, Takuya Niida, Hyoe Takata, Keisuke Taniguchi, Honoka Kurosawa, Kazuki Fujita, and Alexei Konoplev

This study presents the temporal variations in riverine 137Cs concentrations and fluxes to the ocean during high-flow events in three coastal river catchments contaminated by the Fukushima Daiichi Nuclear Power Plant accident. River water samples were collected at points downstream in the Niida, Ukedo, and Takase Rivers during three high-flow events that occurred in 2019–2020. Variations in both the dissolved 137Cs concentration and 137Cs concentration in suspended solids appeared to reflect the spatial pattern of the 137Cs inventory in the catchments, rather than variations in physico-chemical properties. Negative relationships between the 137Cs concentration and δ15N in suspended sediment were found in all rivers during the intense rainfall events, suggesting an increased contribution of sediment from forested areas to the elevated 137Cs concentration. The 137Cs flux ranged from 0.33 to 18 GBq, depending on the rainfall erosivity. The particulate 137Cs fluxes from the Ukedo River were relatively low compared with the other two rivers and were attributed to the effect of the Ogaki Dam reservoir upstream. The ratio of 137Cs desorbed in seawater to 137Cs in suspended solids ranged from 2.8% to 6.6% and tended to be higher with a higher fraction of exchangeable 137Cs. The estimated potential release of 137Cs from suspended solids to the ocean was 0.048–0.57 GBq, or 0.8–6.2 times higher than the direct flux of dissolved 137Cs from the river. Episodic sampling during high-flow events demonstrated that the particulate 137Cs flux depends on catchment characteristics and controls 137Cs transfer to the ocean. 

How to cite: Wakiyama, Y., Niida, T., Takata, H., Taniguchi, K., Kurosawa, H., Fujita, K., and Konoplev, A.: A comparative study of riverine 137Cs dynamics during high-flow events at three contaminated river catchments in Fukushima, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3442, https://doi.org/10.5194/egusphere-egu22-3442, 2022.

EGU22-5397 | Presentations | GI2.3

Integrating measurement representativeness and release temporal variability to improve the Fukushima-Daiichi 137Cs source reconstruction 

Joffrey Dumont Le Brazidec, Marc Bocquet, Olivier Saunier, and Yelva Roustan

    The Fukushima-Daiichi accident involved massive and complex releases of radionuclides in the atmosphere. The releases assessment is a key issue and can be achieved by advanced inverse modelling techniques combined with a relevant dataset of measurements. A Bayesian inversion is particularly suitable to deal with this case. Indeed, it allows for rigorous statistical modelling and enables easy incorporation of informations of different natures into the reconstruction of the source and the associated uncertainties.
    We propose several methods to better quantify the Fukushima-Daiichi 137Cs source and the associated uncertainties. Firstly, we implement the Reversible-Jump MCMC algorithm, a sampling technique able to reconstruct the distributions of the 137Cs source magnitude together with its temporal discretisation. Secondly, we develop methods to (i) mix both air concentration and deposition measurements, and to (ii) take into account the spatial and temporal information from the air concentration measurements in the error covariance matrix determination.
    Using these methods, we obtain distributions of hourly 137Cs release rates from 11 to 24 March and assess the performance of our techniques by carrying out a model-to-data comparison. Furthermore, we demonstrate that this comparison is very sensitive to the statistical modelling of the inverse problem.

How to cite: Dumont Le Brazidec, J., Bocquet, M., Saunier, O., and Roustan, Y.: Integrating measurement representativeness and release temporal variability to improve the Fukushima-Daiichi 137Cs source reconstruction, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5397, https://doi.org/10.5194/egusphere-egu22-5397, 2022.

EGU22-6698 | Presentations | GI2.3

Vertical distribution of 137Cs in bottom sediments as representing the time changes of water contamination: Chernobyl and Fukushima 

Aleksei Konoplev, Yoshifumi Wakiyama, Toshihiro Wada, Yasunori Igarashi, Gennady Laptev, Valentin Golosov, Maxim Ivanov, Mikhail Komissarov, and Kenji Nanba

Bottom sediments of lakes and dam reservoirs can provide an insight into understanding the dynamics of 137Cs strongly bound to sediment particles. On this premise, a number of cores of bottom sediments were collected in deep parts of lakes Glubokoe, Azbuchin, and Cooling Pond in close vicinity of the Chernobyl NPP in Ukraine, in Schekino reservoir (Upa River) in the Tula region of Russia (2018) and in Ogaki reservoir (Ukedo River) in Fukushima contaminated area (2019). Each layer of bottom sediments can be attributed to a certain time of suspended particles sedimentation. With 137Cs activity concentration in a given layer of bottom sediments corresponding to 137Cs concentration on suspended matter at that point in time, we were able to reconstruct the post-accidental dynamics of particulate 137Cs activity concentrations. Using experimental values of the distribution coefficient Kd, changes in the dissolved 137Cs activity concentrations were estimated. The annual mean particulate and dissolved 137Cs wash-off ratios were also calculated for the period after the accidents. Interestingly, the particulate 137Cs wash-off ratios for the Ukedo River at Ogaki dam were found to be similar to those for the Pripyat River at Chernobyl in the same time period after the accident, while the dissolved 137Cs wash-off ratios in the Ukedo River were an order of magnitude lower than the corresponding values in the Pripyat River. The estimates of particulate and dissolved 137Cs concentrations in Chernobyl cases were in reasonable agreement with monitoring data and predictions using the semi-empirical diffusional model. However, both the particulate and dissolved 137Cs activity concentrations and wash-off ratios in the Ukedo River declined faster during the first eight years after the FDNPP accident than predicted by the diffusional model, most likely, due to greater natural attenuation and, to some extent, remediation measures implemented on the catchments in Fukushima.

This research was supported by Science and Technology Research Partnership for Sustainable Development (SATREPS), Japan Science and Technology Agency (JST)/Japan International Cooperation Agency (JICA) (JPMJSA1603), by bilateral project No. 18-55-50002 of Russian Foundation for Basic Research (RFBR) and Japan Society for the Promotion of Science (JSPS), and JSPS Project KAKENHI (B) 18H03389.

How to cite: Konoplev, A., Wakiyama, Y., Wada, T., Igarashi, Y., Laptev, G., Golosov, V., Ivanov, M., Komissarov, M., and Nanba, K.: Vertical distribution of 137Cs in bottom sediments as representing the time changes of water contamination: Chernobyl and Fukushima, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6698, https://doi.org/10.5194/egusphere-egu22-6698, 2022.

EGU22-7068 | Presentations | GI2.3

Seasonal variation of dissolved Cs-137 concentrations in headwater catchments in Yamakiya district, Fukushima Prefecture 

Taichi Kawano, Yuichi Onda, Junko Takahishi, Fumiaki Makino, and Sho Iwagami

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident occurred on March 11, 2011, and a large amount of Cs-137 was released into the environment. It is important to clarify the behavior of radioactive cesium-137 in headwater catchments because most of the Cs-137 falls and is deposited in forest areas and is transported in the environment through river systems.

The purpose of this study was to clarify the influence of water quality composition and organic matter on the seasonal variation of dissolved Cs-137 concentrations in stream water based on long-term monitoring since 2011 at four headwaters catchments in Yamakiya district, Fukushima Prefecture (Iboishiyama, Ishidairayama, Koutaishiyama, Setohachiyama), located about 35 km northwest of FDNPP.

Water temperature, pH, and EC were measured in the field, and SS and coarse organic matter were collected using a time-integrated SS (suspended sediments) sampler and organic matter net. The Cs-137 concentrations was measured in the laboratory using a germanium detector. Concentrations of cations (Na⁺,K⁺,Ca²⁺,Mg²⁺,NH₄⁺) and anions (Cl⁻,SO₄²⁻,NO₃⁻,NO₂⁻,PO₄²⁻) were measured by ion chromatography after 0.45μm filtration. In addition, dissolved organic carbon (DOC) concentrations was measured using a total organic carbon analyzer.

The results showed that K⁺, which is highly competitive with Cs-137, was detected at Iboisiyama, Ishidairayama, and Koutaishiyama, while NH₄⁺ was only detected in some samples at Iboishiyama. There was no obvious relationship between dissolved ion concentration and water temperature, and between dissolved ion concentration and dissolved ¹³⁷Cs concentration at all sites. However, a positive correlation between dissolved cesium concentration and water temperature and DOC and water temperature was observed at all sites regardless of the presence of K⁺ and NH₄⁺. On the other hand, there was no clear relationship between the cesium concentrations in SS and organic matter and water temperature. These results suggest that the seasonal variation in dissolved Cs-137 concentrations in stream water with water temperature could be caused by the seasonality of microbial decomposition of organic matter.

How to cite: Kawano, T., Onda, Y., Takahishi, J., Makino, F., and Iwagami, S.: Seasonal variation of dissolved Cs-137 concentrations in headwater catchments in Yamakiya district, Fukushima Prefecture, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7068, https://doi.org/10.5194/egusphere-egu22-7068, 2022.

A study of 137Cs distribution in a landscape cross-section characterizing the ELGS system (top-slope-closing depression) in the “Vyshkov-2” test site located in the Chernobyl abandoned zone, the Bryansk region, Russia, has been performed in 2015 and 2021. The test site (70×100 m) is located on the Iput’ river terrace in a pine forest characterized by the undisturbed soil-plant cover. Sod-podzolic sandy illuvial-ferruginous soils present the soil cover. The initial level of 137Cs contamination of the area varied from 1480 kBq/m2 to 1850 kBq/m2. Up to now, 89-99 % of the total 137Cs is fixed in the upper 20 cm soil layer with 70-96 % in the upper 8 cm. It allows field spectrometry data to study the structure of the 137Cs contamination field. The 137Cs activity was measured in the soil and moss cover along cross-sections with 1 m step by adapted gamma-spectrometer Violinist-III (USA). Cs-137 content in the soil cores’ and plant samples was determined in the laboratory by Canberra gamma-spectrometer with HPGe detector. It was shown that there is no unidirectional movement of 137Cs both in the soil and in the vegetation cover of the ELGS from the top to the closing depression. On the contrary, the data obtained allow us to state a pronounced cyclical variation of the 137Cs activity in ELGS, which can be traced in the soil and the vegetation. The variation appeared to be rather stable in space 29 and 35 years after the primary pollution. Cyclic fluctuation (variation) of 137Cs activity was described mathematically using Fourier-analysis, which was used to model the observed changes by the revealed three main harmonics. High and significant correlation coefficients obtained between the variation of 137Cs activity and the model for the soil-vegetation cover (r0,01= 0,868; n=17 - 2015; r0,01= 0,675; n=17 - 2021), soils (r0,01= 0,503-0,859; n=17) and moss samples (r0,01= 0,883; n=17 - 2015; r0,01= 0,678; n=17 - 2021) proved satisfactory fitting of models. The character of 137Cs variability in moss cover was generally similar to surface soil contamination, but the level of contamination and amplitude was specific.

The performed study confirmed specific features of 137Cs secondary migration in ELGS, which periodic functions describe. We infer that the observed cyclicity reflects elements’ migration in the ELGS system with water.

The reported study was funded by the Vernadsky Institute federal budget (research task #0137-2019-0006). The field works were supported partly by RFBR No 19-05-00816.

How to cite: Dolgushin, D. and Korobova, E.: Regularities of the 137Cs secondary distribution in the soil-moss cover of elementary landscape-geochemical systems and its dynamics within 6 years on the test site in the Chernobyl abandoned zone, Russia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8178, https://doi.org/10.5194/egusphere-egu22-8178, 2022.

EGU22-9022 | Presentations | GI2.3

Ten-year long-range transport of radiocaesium in the surface layer in the Pacific Ocean and its marginal seas 

Michio Aoyama, Yuichiro Kumamoto, and Yayoi Inomata

Radiocaesium derived from the Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident was observed across a wide area of the North Pacific, not only in surface seawater, but also in the ocean interior. In this presentation, we summarized the time scale of Lagrangian transport of the FNPP1 derived radiocaesium in surface water during the period from the time of the accident to March 2021 in the North Pacific and the Arctic Oceans and its marginal seas as shown below.

Initial observation results until December 2012 in the surface layer in the North Pacific Ocean by the global observations revealed that a typical feature within one year after the accident was a westward movement across the North Pacific Ocean, speed of which was reported at 7 km day-1 until August 2011. After that, the main body of FNPP1-derived radiocaesium moved east as 3 km day-1 and is separated from Japan in 2013. The arrival of the FNPP1 signal at the west coast of the American continent was reported in 2014. The elevation in the FNPP1 derived radiocaesium concentration in the Bering Sea in 2017 and in the Arctic Ocean in 2019 was reported. The northward bifurcation of the Kuroshio Extension made these obvious transport of the FNPP1 derived radiocaesium to the subarctic and arctic region while the transport by southward bifurcation was not observed. At Hawaii Islands in the subtropical gyre, there was no signal of the FNPP1 derived radiocaesium during the period from March 2011 and February 2017. At Yonaguni Island where the Kuroshio enters the East China Sea, the FNPP1 signal arrived at Yonaguni Islands eight years after the time of the accident, and these might be transported mainly from the subtropical gyre.

At the marginal seas of the North Pacific Ocean, the elevation in the FNPP1 derived radiocaesium concentration in the northern East China Sea in 2014, in the Sea of Japan in 2014/2015 were observed.

We also briefly summarize study results on nuclides other than radiocaesium (e.g., 90Sr, 239240Pu, and 129I).

How to cite: Aoyama, M., Kumamoto, Y., and Inomata, Y.: Ten-year long-range transport of radiocaesium in the surface layer in the Pacific Ocean and its marginal seas, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9022, https://doi.org/10.5194/egusphere-egu22-9022, 2022.

Radiocesium (137Cs) was one of the radioactive materials released from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011. Highly 137Cs contaminated water from groundwater to the sea was reduced after installation of the sea-side impermeable wall as a countermeasure against contaminated water in October 2015. As a result, 137Cs contamination in water from other sources became more prominent and the levels of 137Cs concentration in seawater was correlated with rainfall fluctuation. To determine the source of contamination, we estimated the fluctuation patterns of 137Cs concentration in seawater, groundwater level, and discharge from the channels using the Antecedent Precipitation Index (Rw) method.
The results indicated that the fluctuation in seawater collected near the 1-4 Units had strong agreement with the 3 day half-life of Rw. The half-life is shorter than that estimated by groundwater level (7 to 30 day). Therefore, the 137Cs concentration in seawater was influenced by relatively faster runoff than the deep groundwater flow. We also made the spatial distribution map of 137Cs concentration in seawater to determine the sources of contamination. It showed that the 137Cs contaminated area was the highest at “south- inside the intake of 1-4 Units” where the outlets of the K and BC discharge channels are located. In particular, the concentration of 137Cs in the channel K was found to correlate with the concentration of 137Cs in seawater near the 1-4 Units (average of R2 = 0.5). These results indicate that the concentration of 137Cs in seawater inside the FDNPP port can be estimated by the Rw method and that the source of the contamination could be determined using the half-life.

How to cite: Sato, H. and Onda, Y.: Determining sources of the 137Cs concentration in seawater at Fukushima Daiichi Nuclear Power Plant using Antecedent Precipitation Index, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9055, https://doi.org/10.5194/egusphere-egu22-9055, 2022.

European seas such as, Baltic, North, and Norwegian Seas are mostly affected areas by the accident at the Chernobyl nuclear power plant (CNPP) in 1986. Since Fukushima Daiichi nuclear power plant (FDNPP) is located on the coast of the North Pacific Ocean in east Japan, its accident resulted in the release of large amounts of radiocesium to the surrounding coastal marine environment (i.e. the waters off Fukushima and neighboring prefectures). The temporal change of radiocaesium concentration in seawater after both accidents was largely dependent on their submarine topography: The Baltic Sea is a semi-closed basin, while Norwegian and North Seas, and the waters off Fukushima and neighboring prefectures is directly connected to open-water. Although concentration of radioacesium (137Cs) in the surface water of the Baltic Sea (central part) continuously decreased, the values in 1996, ten years after the accident, were even higher than pre-accident level in 1985. On the other hand, in the waters off Fukushima and neighboring prefectures 137Cs concentrations in 2020, nine years after the accident, are approaching the pre-accident levels of 2010. The quick decrease is attributable to the intrusion or mixing of water masses with low 137Cs.

How to cite: Takata, H.: Temporal trends of radio-cesium concentration in the marine environment after the Chernobyl and Fukushima Dai-ichi Nuclear Power Plant accidents, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10644, https://doi.org/10.5194/egusphere-egu22-10644, 2022.

EGU22-10713 | Presentations | GI2.3 | Highlight

Decontamination and subsequent natural restoration processes impact on terrestrial systems in Niida River Catchment in Fukushima 

Yuichi Onda, Feng Bin, Yoshifumi Wakiyama, Keisuke Taniguchi, Asahi Hashimoto, and Yupan Zhang

For the Fukushima region in Japan, the large-scale decontamination in the catchments needed to require more attention because of their possible consequence in altering particulate Cs-137 flux from the terrestrial environment to the ocean. Here, combining the high-resolution satellite dataset and concurrent river monitoring results, we quantitively assess the impacts of land cover changes in large-area decontaminated regions on river suspended sediment (SS) and particulate Cs-137 dynamics during 2013-2018. We find that the decontaminated regions’ erodibility dramatically enhanced during the decontamination stage but rapidly declined in the subsequent natural-restoration stage. River SS dynamics show linear response to these land cover changes, where annual SS load (normalized by water discharge) at the end of decontamination increased by over 300% than pre-decontamination and decreased about 48% at the beginning of natural restoration. Fluctuations in particulate Cs-137 concentrations well reflect the process of sediment source alternation due to land cover changes in decontaminated regions. The “Fukushima decontamination experiment” can reveal the dramatic impact of decontamination-natural restoration processes, which highlights the need for quantitatively assessing human impacts on land use and resultant alternation in sediment transfer patterns in large scale catchments. 

How to cite: Onda, Y., Bin, F., Wakiyama, Y., Taniguchi, K., Hashimoto, A., and Zhang, Y.: Decontamination and subsequent natural restoration processes impact on terrestrial systems in Niida River Catchment in Fukushima, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10713, https://doi.org/10.5194/egusphere-egu22-10713, 2022.

EGU22-10817 | Presentations | GI2.3

Effects of stemflow on radiocesium infiltration into the forest soil 

Hiroaki Kato, Hikaru Iida, Tomoki Shinozuka, Yuma Niwano, and Yuichi Onda

Radiocesium deposited in the forest canopy is transferred to the forest floor by rainwater and litterfall. Among them, stemflow likely increases the radiocesium inventory by concentrating rainwater around the trunk. However, the effects of stemflow on the influx of radiocesium into forest soil have not been evaluated quantitatively. In this study, the fluxes of rainwater via stemflow, throughfall, and soil infiltration water were observed. The concentration of dissolved 137Cs was measured in a cedar forest in Fukushima Prefecture, Japan. Soil infiltration water was collected at 5 cm and 20 cm depths at the distant point from the tree trunk (Bt), and the base of the tree trunk (Rd), where the influence of stemflow was strong. The observations were conducted during the period from September 2019 to November 2021. During the observation period, an experiment was conducted to intercept the inflow of rainwater via the throughfall or stemflow, and the change in soil infiltration water was observed. The observation results showed that the infiltration flux of radiocesium into the forest soil was significantly higher at the Rd site and about three times larger than at the Bt site. Particularly at the 20 cm depth at the Rd site, the soil infiltration water flux increased with the stemflow. The stemflow exclusion resulted in the dcrease of radiocesium flux by about 70% at all depths at the Rd site. These results suggest that the stemflow increases the input of radiocesium to the base of the tree trunk and facilitates its transfer to the deeper soil layers.

How to cite: Kato, H., Iida, H., Shinozuka, T., Niwano, Y., and Onda, Y.: Effects of stemflow on radiocesium infiltration into the forest soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10817, https://doi.org/10.5194/egusphere-egu22-10817, 2022.

EGU22-11022 | Presentations | GI2.3

Estimation of 137Cs inventories in each ocean basin by a global ocean general circulation model for the global database interpolation 

Daisuke Tsumune, Frank Bryan, Keith Lindsay, Kazuhiro Misumi, Takaki Tsubono, and Michio Aoyama

Radioactive cesium (137Cs) is distributed in the global ocean due to global fallout by atmospheric nuclear weapons tests, releases from reprocessing plants in Europe, and supplied to the ocean by the Fukushima Daiichi Nuclear Power Plant (1F NPP) accident. In order to detect future contamination by radionuclides, it is necessary to understand the global distribution of radionuclides such as 137Cs. For this purpose, observed data have been summarized in a historical database (MARIS) by IAEA. The spatio-temporal density of the observations varies widely, therefore simulation by an ocean general circulation model (OGCM) can be helpful in the interpretation of these observations.

In order to clarify the behavior of 137Cs in the global ocean, OGSM simulations were conducted. Parallel Ocean Program version 2 (POP2) of the Community Earth System Model version 2 (CESM2) is employed. The horizontal resolution is 1.125 degree of longitude, and from 0.28 degree to 0.54 degree of latitude. There are 60 vertical levels with a minimum spacing of 10 m near the ocean surface, and increased spacing with depth to a maximum of 250 m. The simulated period was from 1945 to 2030 with the circulation forced by repeating (“Normal Year”) atmospheric conditions. As input sources of 137Cs to the model, global fallout from atmospheric nuclear tests, releases from reprocessing plants in Europe, and input from the 1F NPP accident were considered. It was assumed that the input conditions in 2020 would continue after 2020.

The simulated 137Cs activity agrees well with the observed data in the database, especially in the Atlantic and Pacific Oceans where the observation density is large. Since 137Cs undergoes radioactive decay with a half-life of 30 years, the inventory for each basin is the difference between the decay corrected cumulative input and flux. In the North Pacific, the inventory reached its maximum in 1966 due to the global fallout by atmospheric nuclear weapons tests. Fluxes from the North Pacific to the Indian Ocean, Arctic Ocean, and Central Pacific were positive, and the North Pacific was a source of supply for other ocean basins. The 1F NPP accident caused a 20% increase in the inventory in 2011. In the North Atlantic, the inventory reaches its maximum in the late 1970s, due to the releases from the reprocessing plant. The outflow flux from the North Atlantic to the Greenland Sea is larger than the other fluxes and is a source of supply to other ocean basins. After 2000, the inflow flux to the North Pacific from the Labrador Sea and the South Atlantic is larger than the outflow flux.

The time series of 137Cs inventory in each ocean basin and the fluxes among ocean basins were quantitatively analyzed by OGCM simulations, and the predictions for the next 10 years were made.  The 137Cs activity concentrations by global fallout can be detected in the global ocean after 2030. The OGCM simulations will be useful in planning future observations to fill the gaps in the database.

How to cite: Tsumune, D., Bryan, F., Lindsay, K., Misumi, K., Tsubono, T., and Aoyama, M.: Estimation of 137Cs inventories in each ocean basin by a global ocean general circulation model for the global database interpolation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11022, https://doi.org/10.5194/egusphere-egu22-11022, 2022.

EGU22-11502 | Presentations | GI2.3

Retrospective assessment of 14C aquatic and atmospheric releases from Ignalina Nuclear Power Plant due to exploitation of two RBMK-1500 type reactors 

Evaldas Maceika, Rūta Barisevičiūtė, Laurynas Juodis, Algirdas Pabedinskas, Žilvinas Ežerinskis, Justina Šapolaitė, Laurynas Butkus, and Vidmantas Remeikis

Considerable amounts of 14C in the nuclear reactor are generated by neutrons. It accumulates in reactor components, coolant, and cleaning systems, and partly is released into the environment as gaseous releases and as liquid effluents. Two RBMK-1500 type reactors were exploited at Ignalina NPP (Lithuania) 1983-2009. Releases from NPP radiocarbon accumulated in local biosphere by photosynthesis, including terrestrial and aquatic media, as INPP used Lake Drūkšiai as a cooling pond

Temporal variation of 14C in lake ecosystem was examined by analyzing measured radiocarbon concentration of the organic compounds (Alkali soluble-AS) and alkali insoluble-AIS) derived from the layers of the Drūkšiai lake bottom sediments. The lake sediment cores were sampled in 2013 and 2019, sliced to 1 cm layers and 14C concentration was measured of every layer. AS and AIS organic fractions of sediment samples were extracted by using the acid-base-acid method.

Tree ring cores were collected from Pinus Sylvestris pines around the Ignalina NPP site at different directions and distances. Cellulose extraction was performed with BABAB (base-acid-base-acid-bleach) procedure, and all samples were graphitized and measured by a single state accelerator mass spectrometry at Vilnius Radiocarbon facility. Tree rings 14C concentration analysis provides atmospheric radiocarbon concentration in locations around the nuclear object. This analysis provides an opportunity to evaluate the impact of a nuclear object on water and terrestrial ecosystems.

The results showed a pronounced increase of 14C above background up to 17.8 pMC in the tree rings during INPP exploitation as well during decommission (since 2010) periods. According to the recorded data in 2004-2017 of the local Ignalina NPP meteorological station, the prevailing wind direction was towards the North and East during warm and light time periods. The radiocarbon released from the INPP stack dilutes when it travels in a downwind direction from the INPP. However, even 6.6 km away from the INPP, the impact of the power plant is still clearly visible. By using our created Gaussian dispersion model, the estimated annual emissions of 14C activity from the Ignalina NPP to the air vary from year to year. When only the 1st INPP reactor Unit was operating in 1985-1987, average emissions were 1.2 TBq/year. Emissions almost doubled to 2.1 TBq/year in 1988, when the 2nd Unit became operational. Later, emission levels increased. It could be explained by the large amount of 14C accumulating in the graphite of the RBMK reactor and its gradual release.

14C concentration profile analysis of the lake bottom sediments core revealed a significant impact of the Ignalina NPP on the Drūkšiai lake ecosystem. An increase of 14C concentration in the layers of bottom sediments by 80 pMC in the AS fraction and only by 9 pMC in the AIS fraction was observed, corresponding to the period about years of 1998-2003. The maximum peak in AS of 189 pMC was reached approximately in 2001, followed by gradual lake recovery. This radiocarbon peak in the lake represents a large single one-time pollution release. The critical period was in 2000s when maintenance works of the reactors were performed.

How to cite: Maceika, E., Barisevičiūtė, R., Juodis, L., Pabedinskas, A., Ežerinskis, Ž., Šapolaitė, J., Butkus, L., and Remeikis, V.: Retrospective assessment of 14C aquatic and atmospheric releases from Ignalina Nuclear Power Plant due to exploitation of two RBMK-1500 type reactors, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11502, https://doi.org/10.5194/egusphere-egu22-11502, 2022.

EGU22-11571 | Presentations | GI2.3

Mapping of Post-Disaster Environments using 3D Backprojection and Iterative Inversion Methods Optimised for Limited-Pixel Gamma Spectrometers on Unoccupied Aerial Systems (UAS). 

Dean Connor, David Megson-Smith, Kieran Wood, Robbie Mackenzie, Euan Connolly, Sam White, Freddie Russell-Pavier, Matthew Ryan-Tucker, Peter Martin, Yannick Verbelen, Thomas Richardson, Nick Smith, and Thomas Scott

All radiological measurements acquired from airborne detectors suffer from the issues of geometrical signal dilution, signal attenuation and a complex interaction of the effective sampling area of the detector system with the 3D structure of the surrounding environment. Understanding and accounting for these variables is essential in recovering accurate dose rate maps that can help protect responding workforces in radiologically contaminated environments.

Two types of terrain-cognisant methods of improving source localisation and the contrast of airborne radiation maps are presented in this work, comprising of ‘Point Cloud Constrained 3D Backprojection’ and ‘Point Cloud Constrained Randomised Kaczmarz Inversion’. Each algorithm uses a combination of airborne gamma-spectrometry and 3D scene information collected by UAS platforms and have been applied to data collected with lightweight, simple (non-imaging) detector payloads at numerous locations across the Chornobyl Exclusion Zone (CEZ).

Common to both the algorithms is the projection of the photopeak intensity onto a point cloud representation of the environment, taking into account the position and orientation of the UAS in addition to the 3D response of the spectrometer. The 3D Backprojection method can be considered a relatively fast method of mapping of through proximity, in which the measured photopeak intensity is split over the point cloud according to the above factors. It is an additive technique, with each measurement increasing the overall magnitude of the radiation field assigned to the survey area, meaning that more measurements continues to increase the total radiation of the site. The total measured intensity of the solution is then normalised according to the time spent in proximity to each point in the scene, determined by splitting and projecting the nominal measurement time at each survey point over the point cloud according to the distance from the survey position. Thus accounting for sampling biases during the survey.

The inversion approach adapts algorithms routinely used in medical imaging for the unconstrained world in which the detector is no longer completely surrounding the subject/target. A forward projection model, based on the contribution of distant point sources to the detector intensity, is used to determine the relationship between the full set of measurements and the 3D scene. This results in a hypercube of linear equations where it is assumed every point in the scene contributes to the measured intensity. The algorithm randomly adds measurements from within the aerial set and back-projects this onto the point cloud, with the initial state of the solution set to emit no radiation. After a given number of iterations, the fit of the current solution to the original measurements is assessed though a least squares method and updated when this produces a fit better than the current best estimate. This continues to happen until a minimum value is reached before the divergence of the system, representing the most confident solution. Based on examples from both simulations and real world data, the improvement in contrast of airborne maps using this inversion method can make them equivalent to ground-based surveys, even when operating at 20 m AGL and above.

How to cite: Connor, D., Megson-Smith, D., Wood, K., Mackenzie, R., Connolly, E., White, S., Russell-Pavier, F., Ryan-Tucker, M., Martin, P., Verbelen, Y., Richardson, T., Smith, N., and Scott, T.: Mapping of Post-Disaster Environments using 3D Backprojection and Iterative Inversion Methods Optimised for Limited-Pixel Gamma Spectrometers on Unoccupied Aerial Systems (UAS)., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11571, https://doi.org/10.5194/egusphere-egu22-11571, 2022.

EGU22-11620 | Presentations | GI2.3

Methodology for estimating the emission of radionuclides into the atmosphere from wildfires in the Chernobyl Exclusion Zone 

Valentyn Protsak, Gennady Laptev, Oleg Voitsekhovych, Taras Hinchuk, and Kyrylo Korychenskyi

Most of the territory of the Chernobyl Exclusion Zone (CEZ) is covered by forest. Forest of CEZ have accumulated a significant part of the radioactive release and for many years have served as a barrier to the non spreading of the radionuclide contamination outside the CEZ.

According to the classification of wildfire danger, the forests of CEZ belong to high, above average and medium classes, making cases of wildfires as quite common.

Poor, sod-podzolic soils of Ukrainian Polesye contribute to the entry the activity of 90Sr and 137Cs in plant biomass. During wildfires some of the radionuclides contained in combustion products of biomass are emitted into the atmosphere. Biologically important radionuclides such as 90Sr, 137Cs, plutonium isotopes and 241Am bound to fine aerosols - combustion products - can be transported with atmospheric flows over the long range, causing secondary radioactive fallout and forming additional inhalation dose loads on the population.

Lack of the actual information on the source term (rate of emission of radionuclides) does not allow reliable modeling of the radiological impact of wildfires. To address this issue, we have proposed a methodology that allows for operational assessments of the dynamics of radionuclide emissions into the atmosphere from wildfires in the CEZ.

The basic parameters for the calculations are

  • cartographic data on the density of radionuclide contamination of the territory of the CEZ;
  • classification of the territory of the CEZ according to the distributive features of forests and meadows;
  • classification of CEZ forests according to taxa characteristics to estimate amount of stored fuel biomass (kg/m2);
  • experimental data on the transfer of radionuclides from soil to the main components of biomass for the calculation of radionuclide inventory in fuel biomass (Bq/m2). Thus, for meadows the main fuel component is grass turf, while for forest these are litter, wood, bark and pine needles.
  • experimental data on emission factors of radionuclides from fuel biomass.

Implementation of the proposed algorithm in the form of GIS application makes it possible to assess the dynamics of radionuclide emission into the atmosphere by delineation the fire areas on the CEZ map. The NASA WorldView interactive mapping web application can be used to estimate the temporal and spatial characteristics of the wildfire while it is being developed. The contouring of the area affected by fire is carried out according to the analysis of the cluster of thermal points. Also, operational contouring of wildfire can be carried out using data delivered from unmanned aerial vehicles.

The application of the proposed algorithm for the analysis of the dynamics of 137Cs emissions into the atmosphere from the April 2020 wildfire showed a good agreement with the data reported by various authors who used the method of inverse simulation. Improving the accuracy of calculations according to the proposed algorithm can be done by rectifying radionuclide emission factors and taking into account fire intensity data, which in turn can affect both the radionuclide emission factor and the degree of burnout of plant biomass.

How to cite: Protsak, V., Laptev, G., Voitsekhovych, O., Hinchuk, T., and Korychenskyi, K.: Methodology for estimating the emission of radionuclides into the atmosphere from wildfires in the Chernobyl Exclusion Zone, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11620, https://doi.org/10.5194/egusphere-egu22-11620, 2022.

Human activities such as mining and processing of naturally occurring radioactive materials have a potential to result in enhanced radioactivity levels in the environment. In South Africa, there has been extensive mining of gold and uranium which produced large mine tailings dams that are highly concentrated with radioactive elements. The purpose of this study was to carry out a preliminary survey on a large scale to assess the activity concentrations of 238U, 232Th and 40K in mine tailings, soils and outcropping rocks in the West Rand District in South Africa. This was done to better understand the impact of the abandoned mine tailings on the surrounding soil. This study employed in-situ gamma spectrometry technique to measure the activity concentrations of 238U, 232Th and 40K. The portable BGO SUPER-SPEC (RS-230) spectrometer, with a 6.3 cubic inches Bismuth Germanate Oxide (BGO) detector was used for in-situ measurements. In mine tailings the activity concentrations for 238U, 232Th and 40K were found to range from 209.95 to 2578.68 Bq/kg, 19.49 to 108.00 Bq/kg and 31.30 to 626.00 Bq/kg, respectively. In surface soil, the activity concentration of 238U for all measurements ranged between 12.35 and 941.07 Bq/kg, with an average value of 59.15 Bq/kg. 232Th levels ranged between 12.59 and 78.36 Bq/kg, with an average of 34.91 Bq/kg. For 40K the average activity concentration was found to be 245.64 Bq/kg, in a range of 31.30 - 1345.90 Bq/kg. For the rock samples analyzed, average activity concentrations were 32.97 Bq/kg, 32.26 Bq/kg and 351.52 Bg/kg for 238U, 232Th and 40K, respectively. The results indicate that higher radioactivity levels are found in mine tailings than in rocks and soils. 238U was found to contribute significantly to the overall activity concentration in tailings dams as compared to 232Th and 40K. It has been observed that the mine tailings have a potential to impact on the activity concentration of 238U in soil in the immediate vicinity. However, on a regional scale it was found that the radioactivity levels in surface soil mainly depend on the radioelement concentration of the underlying rocks. The contamination is only confined to areas where mine tailings materials are washed off and deposited on surface soils in close proximity to tailings sources. This serves as an indication that the migration of uranium from tailings dams is localized and occurs within short distances. It is recommended that further radiological monitoring be conducted in areas found to have elevated concentration of uranium-238.

Keywords-In-situ gamma-ray spectrometry, Mine tailings, Radioactivity, Soil.

How to cite: Moshupya, P., Abiye, T., and Korir, I.: In-situ measurements of natural radioactivity levels in the gold mine tailings dams of the West Rand District, South Africa., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11669, https://doi.org/10.5194/egusphere-egu22-11669, 2022.

The Mediterranean Basin (which includes the Mediterranean Sea and the countries bordering it) is often referred to as a hotspot for climate change and biodiversity. This image is used to illustrate the multiple risks for the region, its people and its ecosystems. These risks have been assessed by a new analysis of the scientific literature (MedECC 2020), concluding that it is the sum of climate change, pollution, unsustainable use of land and sea and the invasion of non-native species that induces these multiple risks, which are often underestimated. The Mediterranean territory is also a biodiversity hotspot with 25,000 plant species, 60% of which are endemic. It provided a “service” to plant and animal species as refuges during the last ice age (when the climate was much colder and the sea level was 120 m lower). These ecosystems are now under the triple threat of drought, rising sea level and intensified land use. Forest fires due to heat waves and droughts will be increasingly dramatic despite prevention efforts and fire response forces. Climate change, pollution and over-fishing are having a heavy impact on marine ecosystems, which contain 18% of known species and cover 0.82% of the global ocean. This talk will depict a picture of these present and future risks. A focus will be done on the viticulture which is iconic of the Mediterranean agricultural production and which is very vulnerable to climate change especially on its southern fringe where more intense and frequent droughts are projected. The methodology involves the use of a vegetation model offline coupled to earth system models. A shift of several degrees toward the north is projected for the vine area in case of a global warming larger than +2°C according to the pre-industrial period.

MedECC (2020) Climate and Environmental Change in the Mediterranean Basin – Current situation and Risks for the Future. First Mediterranean Assessment Report [Cramer, W., Guiot, J., Marini, K. (eds