Mercury (Hg) is a toxic global pollutant of great environmental concern. The UNEP Minamata convention on mercury, a legally-binding international treaty aiming to reduce negative impacts of Hg on the environment, has entered into force in 2017. Anthropogenic activities have altered the global Hg cycle to a great extent and many ecosystems are threatened by exposure to elevated levels of Hg and its different species. For instance, neurotoxic and bioaccumulating methyl-Hg is formed under the influence of anaerobic microorganisms in a variety of natural systems but the controls on this key process are still far from being understood. Further active Hg research areas include exchange processes at the atmosphere-soil-plant interface and their importance for understanding atmospheric Hg deposition, the behavior and long-term fate of Hg at contaminated sites, as well as global cycling models assessing the evolution of historic Hg fluxes from different natural and anthropogenic sources. In the past few years, a number of novel research tools based on microbiological, spectroscopic, isotopic, and modelling techniques have been developed to improve our understanding of Hg cycling in the environment. This session presents new contributions on present-day Hg cycling in the environment using field-based, experimental, and/or modelling approaches on local to global scales, as well as contributions focusing on long- and short-term reconstruction of Hg as a pollutant over time using natural archives such as ice-cores, tree-rings, lake sediments and peat bogs. We particularly welcome research addressing the effects of the implementation of the Minamata convention on mercury levels in the environment and new approaches to assess its effectiveness.

Convener: Jan G. Wiederhold | Co-conveners: Sofi JonssonECSECS, Martin JiskraECSECS, Sophia HanssonECSECS
| Attendance Fri, 08 May, 08:30–10:15 (CEST)

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Chat time: Friday, 8 May 2020, 08:30–10:15

Chairperson: Jan Wiederhold, Sofi Jonsson, Sophia Hansson
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Stefan Osterwalder, Michelle Nerentorp, Wei Zhu, Erik Nilsson, Mats Nilsson, Anna Rutgersson, Anne Soerensen, Jonas Sommar, Marcus Wallin, Ingvar Wängberg, and Kevin Bishop

Ocean waters store approximately 400 Gg of mercury (Hg) and exchange it with the atmosphere at a high rate. Air-sea exchange of gaseous elemental mercury (Hg0) is a key process in global Hg cycling because evasion lowers the reservoir of Hg(II) available for methylation and subsequent bioaccumulation in marine fish and prolongs the atmospheric lifetime and subsequently global cycling of Hg. However, global estimates on the air-sea flux are not well constrained (1.9 to 4.2 Gg a-1) mainly because high-resolution measurements of Hg0 in seawater are largely lacking and parameterization of the Hg0 transfer velocity introduces uncertainties in Hg0 flux modelling. We present estimates of the net Hg0 flux for the Baltic Sea derived from land-based marine measurements of Hg0 in air and seawater as well as micrometeorological techniques. We found that coastal waters at the ICOS field station Östergarnsholm, located east of Gotland, Sweden, were typically supersaturated with seawater Hg0 (mean ± SD = 13.5 ± 3.5 ng m-3; ca. 10 % of total Hg) compared to ambient Hg0 (1.3 ± 0.2 ng m-3). The Hg0 flux calculated using gas-transfer wind speed relationships ranged from 0.1 to 1.3 ng m-2 h-1 over the course of the campaign (May 10 – June 20, 2017). The modeled Hg0 flux showed a distinct diel pattern with an average daytime flux of 0.6 ng m-2 h-1 and nighttime flux of 0.4 ng m-2 h-1, indicating that temperature and light induced production of seawater Hg0 was of significance in shallow waters. Preliminary calculations of the average coastal Hg0 flux simultaneously measured using direct, non-intrusive gradient-based, aerodynamic gradient and relaxed eddy accumulation techniques were 0.5 ± 1, 0.6 ± 3.8 and 0.6 ± 37 ng m-2 h-1, respectively. Although, these flux estimates were in good agreement, there were indications in the temporal patters of the observations, which suggest that there is a need to reconsider the modeled flux with the support of more direct flux measurements. Direct flux measurements revealed not only Hg0 evasion but also periods of Hg0 dry deposition. In addition, direct measurements indicated a stronger wind speed dependence of the Hg0 transfer velocity compared to CO2 which appears to coincide with whitecap formation in the open sea flux footprint (wind speed > 5 m s-1). Hence, we anticipate this study as a starting point for more land-based, marine, continuous measurements of seawater Hg0 concentration in combination with micrometeorological fluxes in order to improve Hg0 flux estimates in regional and global scale models. In this context, directly measured Hg0 fluxes will be pivotal to improve transfer velocity estimates of Hg0 especially during periods of high wind speed.

How to cite: Osterwalder, S., Nerentorp, M., Zhu, W., Nilsson, E., Nilsson, M., Rutgersson, A., Soerensen, A., Sommar, J., Wallin, M., Wängberg, I., and Bishop, K.: Determination of gaseous elemental mercury air-sea exchange in the Baltic Sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19867, https://doi.org/10.5194/egusphere-egu2020-19867, 2020.

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Meng Si, Michelle Feigis, Isabel Quant, Shreya Mistry, Melanie Snow, Knut Breivik, Melissa Lafreniere, Scott Lamoureux, Derek Muir, Alexandra Steffen, Geoff Stupple, Ying Duan Lei, Carl Mitchell, and Frank Wania

The specific properties of gaseous elemental mercury (GEM) allow it to undergo bidirectional exchange between the atmosphere and the Earth’s surface. Determining the direction and the magnitude of GEM’s atmosphere-surface flux is possible and has been accomplished using micrometeorological and chamber techniques, but (i) is complex and labor-intensive, and (ii) often only yields fluxes over relatively short time scales. A recently developed passive air sampler for GEM has the precision required for identifying and quantifying vertical concentration gradients above the Earth’s surface. The feasibility and performance of this approach is currently being tested in a number of field studies aimed at the: (i) measurement of GEM concentration gradients above both mercury-contaminated and background forest soils, (ii) quantification of vertical concentration gradients on a tower through a temperate deciduous forest canopy, and (iii) measurement of mercury concentration gradients over stable and thawing permafrost to determine the effect of permafrost degradation on GEM evasion. Contrasting with earlier flux studies, these investigations cover long time periods (up to 1.5 years) and have coarse temporal resolution (monthly to seasonally). Significant gradients of GEM air concentrations, both increasing and decreasing with height above ground, were observed, implying that at a minimum, the method is able to identify the flux direction of GEM. Under the right circumstances, this method can also be used to estimate the approximate magnitude of the GEM air-surface exchange flux. The measured gradients also reveal the impact of factors such as temperature, solar irradiance, and snow cover on air-surface exchange. The method holds promise for establishing the direction and size of exchange fluxes at long time scales of months to a year, especially in study areas where access, effort and cost are prohibitive to longer duration studies with existing approaches.

How to cite: Si, M., Feigis, M., Quant, I., Mistry, S., Snow, M., Breivik, K., Lafreniere, M., Lamoureux, S., Muir, D., Steffen, A., Stupple, G., Lei, Y. D., Mitchell, C., and Wania, F.: Assessing the atmosphere-surface exchange of gaseous elemental mercury using passive air samplers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11905, https://doi.org/10.5194/egusphere-egu2020-11905, 2020.

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Xinrong Ren, Winston Luke, Paul Kelley, Mark Cohen, Mark Olson, Michael Archer, and Ariel Stein

Atmospheric mercury species (including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM)), trace pollutants (including O3, SO2, CO, NO, NOY and black carbon), and meteorological parameters have been continuously monitored since 2007 at an Atmospheric Mercury Network (AMNet) site located on the northern coast of the Gulf of Mexico at the Grand Bay National Estuarine Research Reserve (NERR) in Moss Point, Mississippi. For the data collected between 2007 and 2018, the average concentrations and standard deviations were 1.39 ± 0.22 ng m-3 for GEM, 5.1 ± 10.2 pg m-3 for GOM, 5.9 ± 13.0 pg m-3 for PBM, and 309 ± 407 ng m-2 wk-1 for mercury wet deposition, with interannual trends of -0.009 ng m-3 yr-1 for GEM, -0.36 pg m-3 yr-1 for GOM, 0.18 pg m-3 yr-1 for PBM, and 2.8 ng m-2 wk-1 yr-1 for mercury wet deposition. The trends are statistically significant for GEM and GOM, but not statistically significant for PBM and mercury wet deposition. Diurnal variation of GEM shows lower concentrations in the early morning due to GEM depletion likely due to plant uptake in high humidity events and slight elevation during the day likely due to downward mixing of higher concentrations of GEM in the air aloft to the surface. Seasonal variation of GEM shows higher levels in winter and spring and lower levels in summer and fall. Diurnal variations of both GOM and PBM show broad peaks in the afternoon likely due to photochemical oxidation of GEM. Seasonally, PBM measurements exhibit higher levels in winter and early spring and lower levels in summer, while GOM measurements show high levels in late spring/early summer and late fall and low levels in winter. The seasonal variation of mercury wet deposition shows higher values in summer and lower values in winter due to higher precipitation amounts in summer than in winter. As expected, anticorrelation between Hg wet deposition and the sum of GOM and PBM but positive correlation between Hg wet deposition and rainfall were observed. Correlation among GOM, ozone, and SO2 suggests two possible GOM sources: direct emissions and photochemical oxidation of GEM with the possible influence of boundary dynamics and seasonal variability. This study indicates that the monitoring site, which is located in a coastal environment of the Gulf of Mexico, might experience impacts from mercury sources that are both local and regional in nature.

How to cite: Ren, X., Luke, W., Kelley, P., Cohen, M., Olson, M., Archer, M., and Stein, A.: Long-term Observations of Atmospheric Speciated Mercury at a Coastal Site in the Northern Gulf of Mexico during 2007–2018, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12156, https://doi.org/10.5194/egusphere-egu2020-12156, 2020.

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Wei Zhu, Xuewu Fu, Hui Zhang, Chen Liu, Ben Yu, and Xinbin Feng

Mercury (Hg) is a neurotoxic pollutant distributed globally via atmospheric transportation of elemental Hg (Hg(0)). Both anthropogenic and natural processes emit Hg to the atmosphere, where the later contributes up to approximately two thirds of the total emissions. Hg(II) in the Earth’s surface can be reduced chemically and biologically, resulted subsequent re-emission of Hg(0) back to the atmosphere. The Hg(0) exhibits bi-directional exchange (i.e., deposition and/or emission) between the land surface and atmosphere. Soil is the largest terrestrial Hg reservoir and its interaction with the atmosphere influences the atmospheric Hg cycling largely. Hg(0) emission from the terrestrial surfaces soil has been postulated to carry a negative MDF and positive MIF in the global Hg biogeochemical models. However, to date, no experimental evidence support that the complex terrestrial soil Hg(0) emission in accordance with this hypothetical simplification.

We coupled the in-situ Hg(0) dynamic flux chamber measurement and stable Hg isotope analysis to report a first dataset on the Hg isotope fractionation during the exchange of Hg(0) between the atmosphere and  8 soils and 1 cinnabar surfaces. The effect of air-soil/cinnabar exchange shifted Hg(0) concentrations in the flux chamber [i.e., (Hg(0)chamber-Hg(0)ambient)/Hg(0)chamber] by a factor of -0.29 – 0.90, corresponding to Hg(0) exchange fluxes ranging from -773 – 14457 ng m-2 h-1. Our results showed that the exchange of Hg(0) between the atmosphere and soil/cinnabar could lead to an enrichment of both light and heavy isotopes (δ202Hg signatures) in Hg(0), as well as depletion or enrichment of odd isotopes (Δ199Hg signatures). This highlighted that multiple processes controlled the land-atmosphere exchange of Hg(0) and affected Hg isotope fractionation. Using a conservative isotope mass balance model, we found urban soils Hg(0) emission exhibited large variations in both δ202Hg (-3.04 to -0.34‰) and Δ199Hg (-0.60 to 0.38‰), which might be controlled by the Hg isotopic signatures in soils and environmental factors. The isotope signatures of Hg(0) emitted from agricultural background soils (δ202Hg = -1.31 ± 1.09‰, Δ199Hg = -0.26 ± 0.16‰, 1σ, n=15) and Hg-enriched agricultural soils in Hg mining area (δ202Hg = 0.51 ± 1.09‰, Δ199Hg = -0.10 ± 0.11‰, 1σ, n=12) exhibited contrasting mass dependent fractionation (MDF). Photo-reduction of soil Hg(II) coordinated to sulfurless ligands likely dominated the MIF of Hg isotope during the exchange of Hg between the atmosphere and  both urban and agricultural soils. While the positive shift of δ202Hg in mining area suggested that other processes including sorption and oxidation were also important in controlling MDF of Hg isotope during air/soil exchange. In a line with Hg-enriched agricultural soils, the forest soil emitted Hg(0) in Hg mining area enriched in heavy isotopes relative to the soil but depleted in odd isotopes. Hg(0) emission from cinnabar ore waste exhibited significant negative δ202Hg (-2.21 to -1.67‰) but positive Δ199Hg (0.17 to 0.38‰). Our results demonstrate complex Hg isotope fractionation during air-soil/cinnabar Hg(0) exchange resulted contrasting enrichment or depletion effects on the atmospheric Hg isotope compositions, thus have important implications for understanding the atmospheric Hg isotope signatures and modeling the global Hg cycling.

How to cite: Zhu, W., Fu, X., Zhang, H., Liu, C., Yu, B., and Feng, X.: Mercury isotope fractionation during the exchange of Hg between the atmosphere and land surfaces: implications for atmospheric Hg cycles, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19103, https://doi.org/10.5194/egusphere-egu2020-19103, 2020.

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Johannes West, Andrew Graham, Liem Nguyen, and Sofi Jonsson

In marine systems, the methylated mercury pool is approximately evenly distributed between monomethylmercury (MMHg) and dimethylmercury (DMHg). While MMHg is well-studied due to its direct link with Hg accumulation in aquatic food webs, there is a general lack of knowledge of processes controlling DMHg formation or degradation. By acting as a net sink or source for MMHg, DMHg may exert control over marine MMHg concentrations and subsequent Hg bioaccumulation in fish and seafood in ways currently not understood. 

At present, recognized degradation pathways of DMHg in marine systems include photochemical demethylation (although this pathway has been debated). Degradation through protonolysis of the Hg-C bond by dissolved sulfide has also been suggested and supported by density function theory calculations (Ni et al, J. Phys. Chem. A, 2006). However, experimental support for this pathway is currently missing. Here, we present data from a series of experiments for the stability of DMHg in the presence of dissolved sulfide or sulfide minerals (e.g. FeS (s)). Our results show that degradation rates are dependent on the sulfide phase and DMHg:sulfide ratios. For dissolved sulfide, we observed a non-linear response between DMHg degradation and sulfide concentrations. Our results indicate that DMHg can be demethylated by sulfide at concentration ratios viable under natural marine conditions. As we found MMHg to be the first product of demethylation, this process could also constitute a significant MMHg source in marine systems.

How to cite: West, J., Graham, A., Nguyen, L., and Jonsson, S.: Dimethylmercury demethylation in the presence of sulfide, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17656, https://doi.org/10.5194/egusphere-egu2020-17656, 2020.

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Mareike Franziska Gutensohn, Jeffra K. Schaefer, Ulf Skyllberg, and Erik Björn

The formation of the neurotoxin methylmercury (MeHg) is a biotic process where anaerobic bacteria methylate inorganic divalent Hg (Hg(II)) intracellularly. The cellular uptake mechanisms are still not identified, but low molecular mass (LMM) thiols play an important role together with thiol groups on the outer membrane in controlling the chemical speciation of Hg(II). For example, increased concentration of specific LMM thiols, especially cysteine, is known to enhance the formation of MeHg. A recent study showed that metabolically active anaerobic microorganisms produced LMM thiols in vivo and exported them to concentrations up to 100 nM in the assay medium. The concentration range was sufficient to significantly affect the chemical speciation, uptake and methylation of Hg(II) without any external addition of LMM thiols.

In this study we investigate the kinetics of microbial formation and cellular export of LMM thiols by the iron-reducing bacterium Geobacter sulfurreducens and the sulfate-reducing bacterium Desulfovibrio sp. ND132 in high time resolution and the impact on the chemical speciation and methylation of Hg(II).

LMM thiols were separated by liquid chromatography and determined by electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Hg(LMM-RS)2 complexes were determined by thermodynamic modeling and by direct measurements using LC-Inductively coupled plasma MS (LC-ICPMS).

Results will be presented for the production of LMM thiol compounds, formation of Hg(LMM-RS)2 complexes and how this change in Hg speciation impacts the Hg(II) methylation rate in short-term washed cell assays. Characterizing the time-dependent molecular composition of LMM thiols associated with methylating microbes are important to further understand their multiple roles on Hg(II) uptake and MeHg formation in bacteria assays and in the environment. 

How to cite: Gutensohn, M. F., Schaefer, J. K., Skyllberg, U., and Björn, E.: Microbial formation of thiols control the chemical speciation and methylation of Hg(II), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9642, https://doi.org/10.5194/egusphere-egu2020-9642, 2020.

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Yu-Rong Liu and Qiaoyun Huang

Rice consumption is now recognized as an important pathway of human exposure to the neurotoxin methylmercury (MeHg), particularly in countries where rice is a staple food. Although the discovery of a two-gene cluster hgcAB has linked Hg methylation to several phylogenetically diverse groups of anaerobic microorganisms converting inorganic mercury (Hg) to MeHg, the prevalence and diversity of microbial communities associated with MeHg production and degradation in paddy soils remain unclear. Both Illumina and PacBio sequencing analyses revealed that Hg methylating communities were dominated by iron-reducing bacteria (i.e., Geobacter) and methanogens, with a relatively low abundance of hgcA+ sulfate-reducing bacteria in the soil. A positive correlation was observed between the MeHg content in soil and the relative abundance of Geobacter carrying the hgcA gene. Our structure equation modeling suggested a much stronger link between bacterial community composition and %MeHg, compared to the abundance of methylating gene (hgcA) and edaphic properties. More importantly, random forest models suggested a more important role of non-Hg methylators than Hg methylators in predicting variations of soil %MeHg.

Microbial demethylation was demonstrated by significantly more degradation of MeHg in the unsterilized soils than the sterilized controls, although more degradation was observed in water-saturated soils than the unsaturated soil. 16S rRNA Illumina sequencing and metatranscriptomic analyses consistently revealed that Catenulisporaceae, Frankiaceae, Mycobacteriaceae, and Thermomonosporaceae were among the most likely microbial taxa in influencing These findings provide new insights into microbial communities associated with MeHg accumulation in paddy soils, with important implications in mitigating the net production and bioaccumulation of MeHg in rice worldwide.

How to cite: Liu, Y.-R. and Huang, Q.: Methylmercury production and degradation by soil microbial communities , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6441, https://doi.org/10.5194/egusphere-egu2020-6441, 2020.

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Lena Wohlgemuth, Stefan Osterwalder, Günter Hoch, Christine Alewell, and Martin Jiskra

The deposition of gaseous elemental mercury, Hg(0), from the atmosphere to terrestrial surfaces remains poorly understood mainly due to difficulties in measuring net Hg(0) fluxes on the ecosystem scale. However, there is emerging evidence that vegetation uptake of atmospheric Hg(0) represents a major deposition pathway to terrestrial surfaces. We will present a novel bottom up approach to calculate Hg(0) deposition fluxes to aboveground foliage by combining foliar Hg accumulation rates on the basis of leaf area with species-specific leaf area indices. We analyzed Hg content in 583 foliage samples from major tree species at 10 European forested research sites along a latitudinal gradient from Switzerland to Northern Finland over the course of the 2018 growing season. Foliar Hg concentrations increased over time in all tree species at all sites. We found that foliar Hg accumulation rates normalized to leaf area increased with crown height and decreased with the age of multi-year old needles. We did not detect a clear latitudinal gradient in foliar Hg accumulation rates.

On an ecosystem scale we developed a simple bottom up approach for foliar Hg(0) uptake considering the systematic variations in crown height, needle age and tree species. We calculated species-specific average foliar Hg(0) dry deposition rates for the 2018 growing season of 22 ± 4 µg Hg m-2 for beech, 16 ± 8 µg Hg m-2 for oak, 3 ± 0.4 µg Hg m-2 for birch, 18 ± 10 µg Hg m-2 for spruce and 8 ± 4 µg Hg m-2 for pine. For comparison, the average Hg wet deposition flux measured at 4 of our 10 research sites during the same time period was 2.5 ± 0.2 µg Hg m-2.

Scaling up site-specific deposition rates to the forested area of Europe (EU28) resulted in a total aboveground Hg(0) deposition to foliage of approximately 20 Mg during the 2018 growing season. Our results confirm that vegetation uptake of atmospheric Hg(0) represents a major deposition pathway to terrestrial surfaces. The bottom up approach we used is a promising method to quantify Hg(0) deposition fluxes based on easy-to-do Hg concentration measurements in foliage.

How to cite: Wohlgemuth, L., Osterwalder, S., Hoch, G., Alewell, C., and Jiskra, M.: A bottom up approach to quantify foliar uptake of gaseous elemental mercury by European forests during the 2018 growing season, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9626, https://doi.org/10.5194/egusphere-egu2020-9626, 2020.

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Lorenz Gfeller, Andrea Weber, Isabelle Worms, Vera Slaveykova, and Adrien Mestrot

Soils in legacy sites of chlor-alkali and acetaldehyde production are point sources of mercury (Hg) to downstream eco-systems. Flooding and agricultural activities may influence the fate of Hg by altering redox conditions, microbial activity and carbon budgets. However, the complex interplay between these parameters is still not well understood. The aim of this work was to better understand the effect of flooding and fertilisation on the release/sequestration of Hg in a polluted  floodplain soil.

We conducted a flooding-draining incubation experiment on two Hg polluted fluvisols (2.4 ± 0.1 and 44.8 ± 0.5 mg.kg-1 Hg). The soils originated from an agriculturally used floodplain situated in the Rhone Valley (Valais, Switzerland) and were exposed to Hg pollution by an acetaldehyde producing plant until the 1970’s. They were incubated in triplicates for each treatment. During 56 days the soils were alternately flooded and drained in intervals of 14 days. For flooding, we used an artificial rain water and a 1:1.5 soil:water ratio. The influence of agricultural activites was studied by adding 0.6% (w/w) of liquid manure in a separate treatment. We monitored pore water Hgtotal, Eh, pH, DOC and relevant metals in daily time intervals. Further, the sampled pore water was filtered in distinct intervals (10µm / 5µm / 0.45µm / 0.020µm) at specific time points and analyzed for Hgtotal. Additionally, the 0.45µm fraction was sampled to study the evolution of colloidal Hg with AF4-ICP-MS.

We observed differences between soil treated with or without manure. In the microcosms (MCs) treated with manure, we observed a Hgtotal release along with reductive disolution of Mn-oxides peaking (Hgtotal: 20.8 µg.L-1) after 5 days of flooding. Subsequently, pore water Hgtotal decreased with a simultanous decrease in pore water SO42-. This is likely due to the onset of sulfate reduction. Additionally, we observed the increase of inorganic colloidal Hg in the range of 10nm hydro dynamic diameter in manure treated MCs with higher contaminated soil during the first 2 and 10 days of incubation.

In the MCs without manure addition, the onset of reductive dissolution of Mn oxides was 2 days later. Pore water Hgtotal  peaked only after 7 days of flooding (19.76 µg.L-1 Hg) and remained at the same levels until the end of the first flooding period. This is likely due to a lower microbial activity and a lower labile carbon pool in the untreated compared to the treated soils.

Flooding of our polluted fluvisol releases Hg after few days. The additional manuring accelerates this process. However, it as well accelerates the subsequent decrease of Hgtotal in the pore water. This is among others due to the formation of Hg nanoparticles. We plan to use electron microscopy in order to draw conclusions about the nature of these Hg nanoparticles.

How to cite: Gfeller, L., Weber, A., Worms, I., Slaveykova, V., and Mestrot, A.: Hg release and Hg nanoparticle formation upon flooding of an agriculturally used fluvisol., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13936, https://doi.org/10.5194/egusphere-egu2020-13936, 2020.

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Jacob Smeds

Dependence of Total Mercury in Superficial Peat With Nutrient Status: Implications for Stability of Peat as an Archive of Hg Deposition


Jacob Smeds1, Mats B. Nilsson2, Wei Zhu2, Kevin Bishop3

[1]Department of Earth Sciences, Uppsala University, Uppsala, Sweden

[2]Department of Forest Ecology, Swedish University of Agricultural Sciences, Umeå, Sweden

[3]Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden


Although Mercury (Hg) has decreased considerably in the atmosphere during recent decades, this potent neurotoxin still constitutes a threat to ecosystems globally through the Hg stored in soils. The mitigation of the risks related to this legacy Hg was a reason to implement the Minamata Convention. Subsequent work under the convention is dependent on assessments of the Hg stored in the environment. A way of doing this is to study environmental archives of atmospheric deposition such as ice cores, lake sediments, and peatlands. A previous study along a chronosequence of mires along the northern coast of Sweden showed Hg content differing by a factor of 2 and correlating strongly with mire age. This was hypothesized to indicate that differences in minerogenic water supply along the chronosequence influenced the stability of Hg after deposition from the atmosphere to the mire surface. Declining access of minerogenic elements with increasing peatland age results in a less nutrient demanding plant species composition as well as decreasing access to microbial electron acceptors. But that study looked at just one 10 cm layer at a depth with peat ca 50 years old. Here we present a more rigorous test of that hypothesis by presenting the total amount and vertical pattern of Hg accumulation during the last 200 years in the superficial peat along that peatland chronosequence.

Eleven peatlands along the northern coast of Sweden near Umeå were sampled. This is an area where isostatic rebound continues to raise the land above the sea level. Triplicate peat cores were collected from both lawns and hummocks, when present. A total of 54 peat cores, each 50 cm deep, were collected and frozen immediately. The cores were then sliced into 2 cm layers, and each slice was analysed for total Hg. Due to the land rising out of the sea, the different peatlands have ages ranging from 100-2000 years since establishment, despite being located within a distance of <10 km. The peatland age correlates with availability of mineral elements and pH. This is due to the fact that the underlying postglacial mineral soil is a source of elements. The distance to the mineral soil increases as peat accumulates with peatland age. Certain elements also leach from the peatlands over time. This documentation of the vertical distribution of Hg in all the peat laid down during the past 200 years in each mire tests the hypothesis that the propensity of Hg to evade back to the atmosphere in this area is related to the amount and composition of inorganic elements.

How to cite: Smeds, J.: Dependence of Total Mercury in Superficial Peat With Nutrient Status: Implications for Stability of Peat as an Archive of Hg Deposition, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9083, https://doi.org/10.5194/egusphere-egu2020-9083, 2020.

D344 |
Brittany Tarbier, Sofi Jonsson, Carluvy Baptista-Salazar, A. Britta K. Sannel, and Gustaf Hugelius

With ongoing climate change, temperatures in the northern latitudes are increasing more than twice as fast as the global mean. This causes thawing of permafrost and the release of carbon and contaminants, including mercury (Hg), which have thus far been immobilized in the frozen soil. The potential release of Hg, and microbial transformation of mobilized inorganic Hg to monomethylmercury (MeHg), presents a risk to ecosystems and human health. MeHg is a neurotoxic substance that is readily taken up and biomagnified in aquatic food webs to dangerous concentrations. Arctic communities are particularly vulnerable to Hg pollution as a result of a diet that often includes high trophic level fish and marine mammals. Despite the ecological and societal consequences of elevated Hg levels and the potential for increased Hg conversion to MeHg in post-thaw wetland environments, much of the Hg cycle in the high North is poorly understood.

While global and northern latitude Hg budgets have been estimated, the effect of permafrost thaw on MeHg formation has not yet been fully investigated. Here, we compared concentrations of total Hg (HgT) and MeHg in intact permafrost samples from palsas and peat plateaus with samples from recently thawed collapse fens and from peatlands unaffected by permafrost dynamics in order to investigate whether permafrost thaw impacts net MeHg formation in peatlands. Our study includes five subarctic permafrost peatland sites located in northern Sweden and Norway. Concentrations of HgT and MeHg in the soil cores ranges from 1.1 to 210 and 0.005 to 28 ng g-1 dry weight, respectively, with higher concentrations in the upper soil horizons. No differences were observed in average HgT and MeHg concentrations between the five sites, including both coastal and inland locations. Interestingly, we observe higher concentrations of MeHg and MeHg:HgT ratios in the collapse fens as compared to the permafrost cores, showing increased net methylation of Hg upon permafrost thaw.

How to cite: Tarbier, B., Jonsson, S., Baptista-Salazar, C., Sannel, A. B. K., and Hugelius, G.: Permafrost thaw increases methylmercury formation in sub-arctic Fennoscandia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18536, https://doi.org/10.5194/egusphere-egu2020-18536, 2020.

D345 |
Jessica A. Serbu, Vincent L. St.Louis, and Sydney J. A. Enns

Anthropogenic activities have resulted in increased mercury (Hg) emissions, and the deposition of inorganic and methyl Hg to watersheds, including those that are glaciated. Alpine glaciers are melting at unprecedented rates due to climate change, with glacier-fed rivers potentially transporting contaminants such as mercury historically archived in glacial ice to downstream proglacial environments. Hg in glacial rivers can also be derived from natural sources such as the erosion of subglacial and proglacial geologic material as glaciers melt and retreat. Furthermore, as inorganic Hg moves downstream, methylation can occur in regions of the watershed that contain wetlands, for example, transforming into it into toxic methyl Hg (MeHg) that can biomagnify in the watershed’s food web.

We conducted detailed monthly water quality surveys along three major glacial river transects (the Athabasca, North Saskatchewan, and Bow) in the Canadian Rocky Mountains (Banff and Jasper National Parks, Alberta), that included sampling for total and dissolved concentrations of total Hg (THg; all forms of Hg in a sample) and MeHg up to 100 km downstream of glacial termini. The resultant inter-seasonal data, spanning from May to December in this mid-latitude region, will be used to assess the amount of Hg originating from glacial melt in these systems and how it is transformed as it moves downstream. We will also examine contributions of Hg from the erosion of subglacial and proglacial bedrock material. Preliminary results show that THg and MeHg concentrations are very low in these rivers, consistently measuring at less that 3 ng/L. Additionally, as one moves downstream a larger proportion of THg is in the dissolved fraction. MeHg always measured around or below our laboratory’s detection limit (0.01 ng/L) regardless of the sampling location on our river transects.

The presence of contaminants such as Hg can have negative impacts on freshwater quality, organisms within the watershed, and downstream human populations. Quantifying the amount and speciation of Hg in the headwaters of three primary watersheds in Canada could have important implications for future research and the ongoing challenge of properly planning for drastic climate change effects in glaciated alpine regions despite concentrations of THg and MeHg being so low. 

How to cite: Serbu, J. A., St.Louis, V. L., and Enns, S. J. A.: Total and methylmercury concentrations in Canadian alpine proglacial freshwater rivers (Banff and Jasper National Parks), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10691, https://doi.org/10.5194/egusphere-egu2020-10691, 2020.

D346 |
Céline Lavergne, Lars-Eric Heimburger, Patricia Bovio-Winkler, Rolando Chamy, and Léa Cabrol

The methylmercury has the feature, in addition to its high toxicity for living organisms, to be easily incorporated, bioaccumulated and biomagnified through the food web in aquatic systems. Recently, the microorganisms implicated in the transformation of mercury to methylmercury have been found much more diverse than previously thought. Among them, 9 methanogenic Archaea strains are able to methylate the mercury in pure culture. However, few proofs exist in situ in polar aquatic systems. Antarctic polar regions receive atmospheric mercury through long-range transport of foreign emissions. In a context of increasing releases of heavy metals in aquatic environments and atmosphere, it is a crucial objective to elucidate the fate of mercury in Antarctic polar aquatic ecosystems and the role Archaea could play in mercury transformations. Hence, microbial diversity was investigated in pristine Antarctic lakes (South Shetland Islands, Antarctic, Chile) and continental sub-Antarctic beaver ponds (Tierra del Fuego, Chile) where benthic total mercury concentration was 14 ±6.5 and 89 ±13 ppm, respectively. Until 6.3% of the active community could be constituted by putative methylators and a positive significant correlation was found between total mercury concentration and putative methylator relative abundance (linear model, p-value=0.001). Putative methylator Archaea Methanoregula and Methanosphaerula have been detected but did not seem active in the studied ecosystems (RNA metabarcoding VS DNA metabarcoding).

Combined with these molecular data, mercury methylation and methylmercury demethylation activities were performed by addition of enriched stables isotopes of inorganic mercury and methylmercury, respectively and we expect to find highest methylation rates in the rich-organic matter ecosystems such as sub-Antarctic beaver ponds.

How to cite: Lavergne, C., Heimburger, L.-E., Bovio-Winkler, P., Chamy, R., and Cabrol, L.: Polar microbes and their implications in the aquatic mercury cycle, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19089, https://doi.org/10.5194/egusphere-egu2020-19089, 2020.

D347 |
Yanxu Zhang

The Minamata Convention is a legally-binding international treaty aimed at reducing the anthropogenic release of mercury, a potent neurotoxin. However, its human health benefit has not been quantified at a global scale. Here we evaluate the Convention’s benefit by a coupled climate-atmosphere-land-ocean-ecosystem model and a human mercury exposure component that considers all food categories. We find the mercury health risk decreases nonlinearly with emission reduction, and the most optimistic scenario leads to mercury level in marine biota half of the present-day level. Our results show that the accumulated benefits of the Convention are 660 billion USD avoided earn loss (3% discount rate, realized in 2010) and 1.2 million avoided deaths from fatal heart attacks over the period 2010-2100, with substantial global human health cost if delaying emission reduction actions. Such a comprehensive modelling approach helps parties to evaluate the effectiveness of implementation as required by the Convention.

How to cite: Zhang, Y.: Human Health Benefits of the Minamata Convention on Mercury, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6320, https://doi.org/10.5194/egusphere-egu2020-6320, 2020.

D348 |
Viktor Kalinchuk, Evgeny Lopatnikov, Anatoly Astakhov, Maksim Ivanov, Renat Shakirov, and Do Huy Cuong

Measurements of gaseous elemental mercury (GEM) in the marine boundary layer (MBL) and GEM evasion fluxes were carried out during the Russian-Vietnam cruise conducted from the Sea of Japan to the South China Sea from October 25 to December 7, 2019. All GEM measurements were performed using two RA-915M mercury analysers (Lumex LLC, Russia). Atmospheric GEM concentrations were measured at two levels (about 2 m and 20 m above the sea surface) with a time resolution of 30 minutes. GEM fluxes were measured in the South China Sea using a dynamic flux chamber.

GEM concentrations ranged between 0.56 ng/m3 and 25.47 ng/m3, and between 0.39 ng/m3 and 23.95 ng/m3 with medians of 1.38 ng/m3 and 1.45 ng/m3 for 2 m and 20 m measurements, respectively. GEM concentrations were significantly affected by air transport of GEM. Concentration Weighted Trajectory (CWT) analysis showed several source regions potentially influencing GEM concentrations in the ambient air during the cruise: the south of the South China Sea, Vietnam, the southeastern China, the south of Japan and the Korean peninsula. Maximum concentrations (up to 25 ng/m3) were registered in Haiphong (Vietnam).

Hg(0) fluxes measured at 7 stations in the South China Sea ranged from 1.1 ng/m2/h to 2.5 ng/m2/h, with median value of 2.07 ng/m2/h. These values were 1,5 times higher than those that were measured by the same method in the Sea of Japan and the Sea of Okhotsk a month earlier.

This work was supported by the Russian Science Foundation (RSF) (Project № 19-77-10011).

How to cite: Kalinchuk, V., Lopatnikov, E., Astakhov, A., Ivanov, M., Shakirov, R., and Cuong, D. H.: Measurements of atmospheric gaseous elemental mercury (GEM) and GEM fluxes in the seas of Southeast Asia in October-December 2019, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12394, https://doi.org/10.5194/egusphere-egu2020-12394, 2020.

D349 |
Evgeny Lopatnikov, Viktor Kalinchuk, Anatoly Astakhov, Yang Gang, and Jianjun Zou

Continuous measurements of gaseous elemental mercury (Hg(0)) in the marine boundary layer (MBL) and Hg(0) fluxes were conducted in the Sea of Japan and the Sea of Okhotsk from September 7 to October 17, 2019. All Hg(0) measurements were carried out using two RA-915M mercury analysers (Lumex LLC, Russia). Hg(0) concentrations in the air were measured at two levels (about 2 m and 20 m above the sea surface) with a time resolution of 30 minutes. Hg(0) fluxes were measured at five sample stations using a dynamic flux chamber.

During the cruise Hg(0) concentrations varied in the range from 0,47 ng/m3 to 1,55 ng/m3, and from 0,31 ng/m3 to 2,71 ng/m3 with medians of 0,92 ng/m3 for 2 m and 20 m, respectively. Atmospheric Hg(0) concentrations in measurements sites were strongly depended on the regions from where air masses came to the study areas. As a result of the Concentration Weighted Trajectory (CWT) analysis we established 2 regions that influenced the Hg(0) concentrations during the cruise: the Northeast China with the Yellow Sea region and the Kurile Islands sector of the Pacific Ocean. The arrival of air masses from China and the Yellow Sea region caused an increase in Hg(0) concentrations in the air in the Sea of Japan and the Sea of Okhotsk. Elevated concentrations were also observed In the Sea of Okhotsk during the periods air masses came from the Kurile Islands sector of the Pacific Ocean.

Hg(0) fluxes were measured at 3 stations in the Sea of Japan and at 2 stations in the Sea of Okhotsk. The values ranged from 0,57 ng/m2/h to 1,55 ng/m2/h, with median value of 1,32 ng/m2/h. A positive relationships between Hg(0) flux and air and water temperature were observed.

This work was supported by the Russian Science Foundation (RSF) (Project № 19-77-10011) and by the National Natural Science Foundation of China (Projects №: 41876065, 41420104005, U1606401) and National Program on Global Change and Air-Sea Interaction (Project № GASI-GEOGE-04).

How to cite: Lopatnikov, E., Kalinchuk, V., Astakhov, A., Gang, Y., and Zou, J.: Atmospheric mercury (Hg(0)) concentrations and Hg(0) fluxes in the Sea of Japan and the Okhotsk Sea in fall 2019, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12677, https://doi.org/10.5194/egusphere-egu2020-12677, 2020.

D350 |
Shaojian huang and Yanxu Zhang

The inter-annual variation of mercury(Hg) was spotted in monitoring stations, like the Alert and Mace Head. Nevertheless, the potential reason still lacks of studying. With periodic disturbance like ENSO, air-sea exchange flux, the largest flux between Earth system reservoirs, might greatly contribute to the inter-annual variation of Hg. Therefore, this study intended to explore the inter-annual variation of Hg0, a dominant evasion form of Hg, driven by MITgcm (ocean model). In general, the inter-annual variation of Hg evasion from global ocean was relatively stable in mid and high latitude, but a violent fluctuation was found in the tropical sea areas, especially equatorial Pacific. A distinct latitudinal difference was spotted that the fluctuation of Hg0 evasion was mainly attributed to wind speed in tropical sea areas, while in temperate zones were correlated with precipitation. Besides, air temperature variation seems to control the Hg0 evasion in the sea areas of South Temperate Zone (STZ) as well as South Frigid Zone (SFZ). Furthermore, an evident “seesaw” effect of Hg0 evasion anomaly was observed in equatorial Pacific, especially within Nino 3.4 and Nino 4, between El Niño(EN) and La Niña(LN) events. The increasing (decreasing) evasion anomaly in Nino 3.4 during the LN(EN) mainly attributed to the increase (decrease) of wind speed induced by stronger Walker circulation. While the increasing (decreasing) evasion anomaly in Nino 4 during EN(LN) was likely accounted for the rising (reducing) precipitation caused by the collapse of Walker circulation as well as the eastward shifting upward motion. Subsequently, the increasing anomaly of Hg0 evasion was simulated by GEOS-Chem model to further explore the potential impact. Results showed that countries, like American, China, India and Brazil. have occupied a large proportion of crops farming, but there spotted a relatively higher THg deposition anomalies, which might increase the human exposure to Hg. Finally, based on limited information, a hypothesis was put forward that there might be an indirect impact of ENSO-driven MeHg variation on the mass mortality of marine mammals.

How to cite: huang, S. and Zhang, Y.: A Diagnosis Analysis to inter-annual variation of air-sea Hg flux in global ocean and the “seesaw” effect in equatorial Pacific, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12787, https://doi.org/10.5194/egusphere-egu2020-12787, 2020.

D351 |
Toru Kawai, Takeo Sakurai, and Noriyuki Suzuki

Numerical modeling is useful for evaluating the international efforts, such as the Minamata Convention on Mercury, that are directed towards the reduction of anthropogenic emissions. We have developed a new global model for mercury, denoted FATE-Hg, which is based on a fully coupled atmosphere-ocean chemical transport model and low and high-order marine ecosystem models. The model considers methylated mercury production in the open ocean seawater, bioconcentration, and food-web biomagnification from particle organic matter to fish. In this study, we performed a long-term simulation over three centuries with changes in anthropogenic emission since the Industrial Revolution, and investigated the long-term evolution of total mercury (THg) in the ocean. The simulated oceanic THg showed a phase lag of 5–10 years from the anthropogenic emission in the surface-intermediate oceans. As of 2010, oceanic THg was 410 Gg, which is 1.6–16.9 times higher than that estimated by the previous model. The estimated overall turnover time of oceanic THg determined by our model was 320 years, which is significantly shorter than those estimated by previous model-based studies. Additionally, we estimated geographic THg sources in the upper ocean. The results showed that North America (NA), Europe (EU), and East Asia are the dominant source regions in most ocean sections in the Northern Hemisphere, though the emissions from NA and EU have fall considerably since the 1970s. This result indicated that a significant amount of mercury that had been emitted from NA and EU in the past persists in present-day seawater.

How to cite: Kawai, T., Sakurai, T., and Suzuki, N.: Investigation of long-term fate of mercury in the ocean using a new global model, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-13103, https://doi.org/10.5194/egusphere-egu2020-13103, 2020.

D352 |
Stefan Osterwalder, Werner Eugster, Iris Feigenwinter, and Martin Jiskra

Direct measurements of the net ecosystem exchange (NEE) of gaseous elemental mercury (Hg0) are crucial to improve our understanding of global Hg cycling and ultimately Hg exposure in humans and wildlife. The lack of long-term, ecosystem-scale measurements causes large uncertainties in Hg0 flux estimates. Today it remains unclear whether terrestrial ecosystems are net sinks or sources of atmospheric Hg0. Here, we present the first successful eddy covariance NEE measurements of Hg0 over natural, low-Hg soils (41 - 75 ng Hg g-1 topsoil [0-10 cm]) at a managed grassland site in Chamau, Switzerland. We present a detailed validation of the eddy covariance technique for Hg0 based on a Lumex mercury monitor RA-915AM. The flux detection limit derived from a zero-flux experiment in the laboratory was 0.22 ng m-2 h-1 (maximum) with a 50 % cut-off at 0.074 ng m-2 h-1. The statistical estimate of the Hg0 flux detection limit under real-world outdoor conditions at the site was 5.9 ng m-2 h-1 (50 % cut-off). Based on our analysis we give suggestions to further improve the precision of the system and pinpoint challenges and interferences that occurred during the 34-day pilot campaign in summer 2018. The data were obtained during extremely hot and dry meteorological conditions. We estimated a net summertime grassland-atmosphere Hg0 flux from -0.6 to 7.4 ng m-2 h-1 (range between 25th and 75th percentiles). The measurements revealed a distinct diel pattern with lower nighttime fluxes (1.0 ng m-2 h-1) compared to daytime fluxes (8.4 ng m-2 h-1). Drought stress during the campaign induced partial stomata closure of vegetation leading to a midday depression in CO2 uptake, which did not recover during the afternoon. We suggest that partial stomata closure dampened Hg0 uptake by vegetation as well, resulting in a NEE of Hg0 dominated by soil emission. The new Eddy Mercury system seems suitable to complement existing research infrastructures such as ICOS RI in Europe or NOAA Observing Systems in the US built to calculate greenhouse gas balances with direct Hg0 deposition and emission measurements. We anticipate our Eddy Mercury system to improve knowledge about Hg cycling between ecosystems and the atmosphere and to challenge model simulations on a regional and global scale.

How to cite: Osterwalder, S., Eugster, W., Feigenwinter, I., and Jiskra, M.: First eddy covariance flux measurements of gaseous elemental mercury over a grassland, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19753, https://doi.org/10.5194/egusphere-egu2020-19753, 2020.

D353 |
Jing Gu, Qiaotong Pang, Jinzhi Ding, Runsheng Yin, Yuanhe Yang, and Yanxu Zhang

Soil is one of the largest reservoir of mercury in the environment. Globally, most of the mercury in the soil is stored in permafrost, such as the Arctic and the Tibetan Plateau. Mercury in the soil is mainly derived from atmospheric deposition and tightly bound to the organic carbon. The mercury level in the permafrost over the Tibetan Plateau and its influencing factors have been less studied. This study analyzes soil total mercury (STHg) concentrations and its vertical distribution in meadow soil samples collected from the Tibetan Plateau. We adopt a nested-grid high-resolution GEOS-Chem model to simulate atmospheric mercury deposition. The relationship between STHg and soil organic carbon(OCD) as well as atmospheric deposition are explored. We also extend our analysis to data in the Tibetan Plateau and other regions of China in the literature. Our results show that the STHg concentrations in the Tibetan Plateau are 19.9±12.4 ng/g. The concentrations are higher in the south/east and lower in the north/west in the Tibetan Plateau, consistent with the previous results. Our model shows that the average deposition flux of Hg is 3.3 ug m-2 yr-1 with 57% contributed by dry deposition of Hg0, followed by dry deposition of HgII and HgP (19%) and wet deposition (24%). We calculate the Hg to carbon ratio (RHgC) of 5.52 ± 5.11 μg Hg/g C and the estimated STHg is 67.45 Gg in alpine grasslands in the Tibetan Plateau, contributing about 2.7% globally. We find a positive correlation between OCD and STHg in the Tibetan Plateau(Log(STHg) = 0.35log(OCD) + 0.99, R2 = 0.24) and a weak relationship between model residual (defined as the difference between model fitting values and observations) and atmospheric total Hg deposition. We conclude that soil organic carbon(SOC) and atmospheric deposition work simultaneously for STHg. Atmospheric deposition determines the potential levels of STHg in large spatial scales, while SOC and its characteristics modulate STHg locally by influencing the fate and transport of Hg.

How to cite: Gu, J., Pang, Q., Ding, J., Yin, R., Yang, Y., and Zhang, Y.: The storage and influencing factors of mercury in the permafrost of the Tibetan Plateau, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1598, https://doi.org/10.5194/egusphere-egu2020-1598, 2020.

D354 |
Yury Tatsiy

Studies of dated cores of bottom sediments from Arctic lakes to determine flows and the history of sedimentation of heavy metals have been carried out since the beginning of the 90s. This is largely due to the need to understand the spatial and temporal trends of pollution in the Arctic and the ways of influencing wildlife and people, especially in a changing climate. Arctic lakes are sensitive indicators of global changes in the environment and climate, as well as the effects of regional and transboundary transport of pollutants. Bottom sediments of Arctic lakes that are not subject to direct anthropogenic influences are a kind of paleoclimatic and paleogeochemical archives that contain information about biogeochemical processes on the catchment and in the reservoir itself, informatively reflect environmental changes.

Arctic mercury is of particular interest. Besides the fact that this metal is an element of the first hazard class, it is a global pollutant. Unfortunately, the published data on mercury in the bottom sediments of Arctic lakes are much less than for other heavy metals. To some extent, this is due to analytical problems in determining low mercury levels.

The aim of the research is to assess the dynamics of sedimentation of mercury and identify a possible anthropogenic contribution to the period of industrial activity.

The results of research of mercury distribution in sediments are presented for cores from five Arctic lakes – NARY_1-2 (Malozemelskaya tundra), NARY_2-4 and 9-1 (Lovetsky Island, the mouth of the Pechora River), Langtibejto (Yamal Peninsula) and Gol’tsovoe (Gydan Peninsula). Sedimentation rates were estimated using 210Pb and 137Cs geochronology. Chemical composition, granulometry and loss on ignition were determined layer by layer for all sediment cores.

The layer-by-layer analysis of all cores of bottom sediments showed that the distribution of mercury differs significantly from the distribution of other elements by a significantly stronger enrichment of the surface layers. The nature of this distribution in column NARY1_2 coincides with both the beginning of the industrial period (end of the 19th century) and the beginning of the work of the Norilsk industrial complex.

Enrichment of the surface layer of sediments can be caused not only by transboundary transport of mercury, but also by an increased content of organic matter in the upper horizons of sediments.

The nature of the distribution of mercury along the length of the columns and the distribution over fractions with different particle sizes showed that the finest fraction does not always determine the total concentration in the slice. At the same time, large particles (> 0.2 mm) with a high mercury concentration are present in the columns.

The data obtained show that, unlike other elements, the studied lakes are conditionally background for mercury.

This work was supported by the Russian Science Foundation (project 18-17-00184)

How to cite: Tatsiy, Y.: Bottom Sediments of Arctic Lakes as Indicators of Mercury Biogeochemical Migration, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11718, https://doi.org/10.5194/egusphere-egu2020-11718, 2020.

D355 |
Irene Gregory-Eaves, Marieke Beaulieu, Marc Amyot, Katherine Griffiths, and Alexandre Poulain

Strong measures have been taken since the 1970s to reduce mercury emissions in Canada. However, long-range transport of emissions continues and constitutes a large percentage of the total anthropogenic deposition of mercury in Canada. Natural sources of mercury are also heterogeneously distributed across the Canadian landscape.  As part of the LakePulse network (www.lakepulse.ca), we are quantifying mercury concentration in hundreds of lake sediment cores across 13 Canadian ecozones. Analyses from eastern Canada lakes showed that total mercury is significantly different among ecozones, and many ecozones showed higher total mercury concentrations in contemporary sediments.  Contemporary methyl mercury concentrations also differed among ecozones. Our overarching goals are to map the heterogeneity in mercury concentrations across the country and to identify the most parsimonious set of predictors considering a suite of physico-chemical and land-use variables from lakes and their watersheds set across the temperate to subarctic landscape.

How to cite: Gregory-Eaves, I., Beaulieu, M., Amyot, M., Griffiths, K., and Poulain, A.: Mercury dynamics from pan-Canadian survey of lakes: analyses of sediment cores, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5634, https://doi.org/10.5194/egusphere-egu2020-5634, 2020.

D356 |
Efrén García Ordiales, Mario Mangas, Lorena Sanz-Prada, Elena Pavoni, Stefano Covelli, Nieves Roqueñí, Jorge Loredo, and Pablo Cienfuegos

Aviles estuary is one of the most impacted estuaries of the north of Spain. In its margins, there are several heavy industries such as steel, zinc and aluminium factories together with other little factories dedicated to secondary metallurgical products. Because of the intense metallurgical activities developed in the area, sediments of the estuary show an important metal load. Among the different heavy metals present in the estuary, Hg in one of the most important due to its toxicity and potential transference to biota. To study the Hg concentrations present in the estuary, 52 scattered samples were collected. Samples were analysed for total Hg, and other parameters such as grain size, organic matter and sulphur have been determined. Total Hg concentration in the estuary sediments ranged between 0.1 to 18.3µg g-1 with an average of 4.3 µg g-1. The particle size of the sediment governed the mercury dispersion in the estuary. In the inner part where silt and clay fraction are predominant, Hg showed the highest values while in areas where sands predominate Hg concentrations decrease. The Hg concentration in a total of 36 samples exceed the probable effect level established by NOAA, which suggest that Hg may be transferred to the biota of the estuary and could be a problem for the health status of the area. On the other hand, concentrations of 26 samples were above the C level of the Spanish dredging regulations, limiting its management to encapsulation in non-vulnerable areas or its management as waste by an authorized manager.

How to cite: García Ordiales, E., Mangas, M., Sanz-Prada, L., Pavoni, E., Covelli, S., Roqueñí, N., Loredo, J., and Cienfuegos, P.: Spatial variations of mercury in sediments of Aviles Harbour and its implications on dredging, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7712, https://doi.org/10.5194/egusphere-egu2020-7712, 2020.

D357 |
Michal Hošek, Tomáš Matys Grygar, Jiří Štojdl, Jitka Elznicová, and Jan Svoboda

The catchments of the Kössein and the Röslau rivers (north-eastern Bavaria, Germany) was impacted by pollution from Chemical Factory Marktredwitz (CFM). The CFM produced Hg compounds for almost 200 years until the severe pollution of the factory surroundings and the Kössein River was revealed in the 1980s. The channel belt of the Kössein-Röslau rivers downstream the CFM is now one of the most severe Hg pollution hotspots in Central Europe. At the present days, more than 30 years after the factory abandonment, the Hg concentrations in fish muscles reach up to 6 mg/kg in the Skalka Reservoir, which acts as a sedimentary trap for that pollution.

The main vector for the actual fluvial recycling of Hg is suspended particulate matter (SPM) formed by the fluvial erosion of the channel belt. In previous work we found out that the Hg inventory in the Kössein-Röslau river system is approximately 20 t Hg deposited in a 22 km long channel belt, mainly as easily thermodesorbed form, perhaps natural organic matter bound Hg (NOM-Hg). Because the Kössein and the Röslau rivers still export SPM with mean concentrations of approximately 20 mg Hg/kg, revitalization options to stop Hg pollution recycling should be considered. We studied the Röslau River floodplain upstream the confluence with the Eger River, situated just upstream the inlet to the Skalka Reservoir. This locality is used for cattle grazing although Hg concentration up to 122 mg/kg can be found in some sediment strata and approximately 45 mg/kg is in topsoils. The locality has been investigated by geophysical methods ERT (electrical resistivity tomography) and DEMP (dipole electromagnetic profiling) to reveal the floodplain subsurface sedimentary architecture, because it is a key to find recent geomorphic traps for the polluted sediment. The floodplain was then sampled after drill coring, Hg analysis was performed by AMA-254 and element analysis by XRF. We found a close correlation between Zn and Hg concentrations, which facilitated the study of the pollution hotspot. We found three facies types of polluted sediments: channel belt (up to 122 mg Hg/kg), fills of shallow flood channels in floodplain (up to 73 mg Hg/kg), and top strata of overbank fines (up to 56 mg Hg/kg). The knowledge on the pollution distribution is essential for the future revitalization and protection measures.

How to cite: Hošek, M., Matys Grygar, T., Štojdl, J., Elznicová, J., and Svoboda, J.: Recycling of mercury pollution in the fluvial system - revitalize or not?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18549, https://doi.org/10.5194/egusphere-egu2020-18549, 2020.

D358 |
Jan G. Wiederhold, Harald Biester, Anna-Lena Gerloff, Jens Hahn, and Lars Duester

Mercury (Hg) is a priority pollutant in aquatic ecosystems. In Germany, the chemical status of all large rivers is classified as “not good” due to the exceedance of at least one environmental quality standard (EQS) of the EU Water Framework Directive [1], mostly due to the failure to meet the EQS for Hg in fish of 20 μg kg-1. Mercury has been introduced to rivers in Germany for more than a century from a variety of anthropogenic sources (e.g., industrial effluents, waste water treatment plants). Transport of Hg in river water occurs dominantly associated with suspended particulate matter, while dissolved Hg concentrations are low. Direct Hg releases to surface waters have been greatly reduced over the last decades and today inputs are dominated by diffuse sources (e.g., atmospheric deposition, soil erosion) and the remobilization of Hg previously deposited in bottom sediments. A key factor in controlling the remobilization and transfer of legacy Hg from sediments to water and ultimately into biota is the chemical form in which Hg is present in sediments and suspended particulate matter.

Here, we present (i) historical trends of Hg concentrations in suspended particulate matter in German rivers (e.g., Rhine, Elbe) over several decades compiled from public databases [2] and (ii) first results of a study aiming to characterize the chemical form of Hg in recently collected suspended particulate matter and contaminated sediment samples from German rivers using pyrolytic thermodesorption analysis [3]. The Hg release curves of samples during continuous heating up to 650°C were compared with those of reference compounds. Total Hg concentrations were determined by a direct Hg analyzer (Nippon MA-3000).

The historical records reveal that Hg concentrations in suspended particulate matter have decreased in the large German rivers from the beginning of the 1990s until today. For example, while yearly average values of 500-800 μg kg-1 Hg were still common in the lower reaches of the Rhine river in the early 1990s, most values in the last five years have been below 300 μg kg-1 Hg. However, the Elbe river, one of the most polluted rivers in Germany, still exhibits Hg values above 1000 μg kg-1 in some areas, despite a decreasing trend from even higher historical values. First results from pyrolytic thermodesorption analyses reveal that Hg in suspended particulate matter from Rhine and Elbe is released at temperatures around 300°C, suggesting a dominance of organically-bound and/or sulfide-bound Hg(II) species. Interestingly, a shift to lower Hg release temperatures was observed after aging of wet sample material and for freeze-dried compared with wet sediments, highlighting the importance of sample preparation and the dynamic nature of Hg binding forms in natural samples.

[1] European Environment Agency (2018) European waters - Assessment of status and pressures 2018.

[2] e.g., http://undine.bafg.de, http://fgg-rhein.bafg.de, https://www.umweltprobenbank.de

[3] Biester H., Scholz C. (1997) Determination of mercury binding forms in contaminated soils: Mercury pyrolysis versus sequential extractions. Environ. Sci. Technol. 31, 233-239.

How to cite: Wiederhold, J. G., Biester, H., Gerloff, A.-L., Hahn, J., and Duester, L.: Mercury contamination in German rivers: Historical trends and current situation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9735, https://doi.org/10.5194/egusphere-egu2020-9735, 2020.

D359 |
Alina Kleindienst, Lorenz Schwab, David McLagan, Stephan M. Krämer, Harald Biester, and Jan G. Wiederhold

Mercury (Hg) leaching from contaminated soils into groundwater or surface waters represents a serious environmental problem at industrial legacy sites, whereby Hg mobility strongly depends on its chemical form. For example, the water solubility of potentially relevant Hg compounds ranges over several orders of magnitude (HgCl2>HgO>Hg2Cl2>Hg(0)>>HgS). Water leaching experiments may provide important information on Hg mobility and help assess its fate at contaminated sites. However, single extraction steps are often not sufficient to extract the entire water-soluble Hg pool. Performing multiple consecutive water extracts on the same sample allows investigating the relative importance of kinetic and thermodynamic controls on Hg mobilization. Moreover, differences between the Hg isotope composition of water extracts and the bulk soil may offer novel insights into the transformation dynamics of Hg species as well as the evolution of Hg isotope signatures at contaminated sites [1].

Here, we present results of consecutive water extractions performed on three soil samples and one artificially-contaminated aquifer material from former industrial sites in Germany contaminated with highly soluble HgCl2 using three extraction solutions (oxygenated water, oxygen-depleted water, 2 mM CaCl2). Batch extractions were conducted with up to nine consecutive steps over timescales of up to three months. Aliquots of selected extracts were purged with argon to remove Hg(0) and to quantify the Hg(0)/Hg(II) ratio by comparison with unpurged extracts. Hg concentrations were measured by CV-AAS/AFS and Hg isotope ratios were determined using CV-MC-ICP-MS. Pyrolytic thermodesorption analysis was used on selected samples to investigate changes in the solid phase speciation.

Total Hg concentrations in extracts decreased after the first step (range: 17 to 1270 μg L−1) but remained surprisingly high until the ninth step (range: 3 to 263 μg L1) illustrating continuous slow Hg release from the contaminated soils in contact with water. The fraction of total soil Hg mobilized at the end of the experiments ranged from 5.6% to 30%. The extracts exhibited large δ202Hg variations from –0.75‰ to +0.94‰ relative to bulk soil indicating preferential mobilization of either light or heavy Hg isotopes for different samples and extraction conditions. Lower Hg concentrations in the purged extracts provided evidence for the presence of Hg(0) approaching its solubility in some extracts, particularly under oxygen-depleted conditions with up to 85% of total dissolved Hg, which is produced by reduction from Hg(II) in our HgCl2-contaminated samples. The isotopic mass balance between purged and unpurged extracts revealed an important control of the Hg(0)/Hg(II) ratio on δ202Hg extract values of some samples with Hg(0) being about 2‰ lighter than Hg(II), consistent with theoretical predictions for equilibrium isotope fractionation. Our results demonstrate that consecutive water extracts can leach large amounts of Hg from contaminated soils accompanied by significant Hg isotope fractionation during the mobilization from solid to solution phase, which is at least partly controlled by equilibrium isotope effects between Hg redox states in solution.

[1] Brocza FM, Biester H, Richard J-H, Kraemer SM, Wiederhold, JG (2019) Mercury isotope fractionation in the subsurface of a Hg(II) chloride-contaminated industrial legacy site. Environ. Sci. Technol. 53, 7296-7305.

How to cite: Kleindienst, A., Schwab, L., McLagan, D., Krämer, S. M., Biester, H., and Wiederhold, J. G.: Mercury concentrations, redox state, and isotope ratios in consecutive water extracts of Hg(II)-chloride contaminated soils, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10564, https://doi.org/10.5194/egusphere-egu2020-10564, 2020.

D360 |
Lorenz Schwab, David S. McLagan, Stephan M. Kraemer, Harald Biester, and Jan G. Wiederhold

For many metals, including mercury (Hg), the transformation between different redox states is an important process for stable isotope fractionation. Identifying fractionation factors for specific Hg redox transformations therefore enables stable Hg isotope techniques to be used as a tool to trace biogeochemical processes and improve our understanding of the transport and fate of Hg in the environment. Previous studies demonstrated that reduced iron (Fe) species and Fe(II)-bearing minerals such as magnetite, green rust, siderite or vivianite are capable of reducing Hg(II) to Hg(I) and Hg(0). These processes may be important in environments with low organic matter concentration and changing redox conditions such as groundwater aquifers or temporarily flooded soils.

In this study homogeneous and heterogeneous redox reactions of Hg(II) with dissolved Fe(II) and Fe(II)-bearing minerals are investigated in batch experiments under oxygen-free conditions in a glove bag. Mercury stock solutions prepared from NIST-3133 in a glass batch reactor are continuously stirred to minimize local reducing zones and wrapped in aluminum foil to prevent photoreduction. The reducing agents are added stepwise to reduce fractions of Hg until complete reduction is achieved. The produced Hg(0) is continuously purged into an oxidizing trap solution (40% inverse aqua regia with BrCl) with nitrogen gas at a low flow rate. After each reduction step solution aliquots are taken from the reactor and the trap is exchanged. Total Hg concentrations in reactor and trap samples are then measured with CV-AAS/AFS and isotopic compositions determined with CV-MC-ICP-MS.

Initially, different amounts of SnCl2 were used as reducing agent to test the experimental setup similar to [1]. For this experiment we observed consistent isotopic trends which could be described by a Rayleigh model fit with mass dependent fractionation (ε202Hg = -­2.75 ± 0.07‰) as well as mass independent fractionation of odd-mass Hg isotopes (Ε199Hg = ­0.32 ± 0.04‰). The slope of the linear regression of Δ199Hg/Δ201Hg of 1.52 ± 0.1 indicates that the MIF was likely caused by the nuclear volume effect. In subsequent experiments different amounts of a Fe(II) stock solution prepared from Fe(II)Cl2 are used as reducing agent. Additionally, experiments are carried out with Fe(II)-bearing minerals and Fe(II) adsorbed to mineral surfaces.

The results produced from this study will be very useful for the interpretation of field data from temporarily anoxic groundwater bodies at contaminated sites (e.g. [2]). The insights from the experiments will further contribute to the understanding of the interplay between Hg and Fe biogeochemical cycles and redox transformations. Most importantly, it will add much needed fractionation factors to the toolbox of Hg stable isotope fractionation as a tracer for biogeochemical transformations.

[1] Zheng, W., Hintelmann, H. (2010) Nuclear field shift effect in isotope fractionation of mercury during abiotic reduction in the absence of light. J. Phys. Chem. A, 114(12), 4238–4245.

[2] Richard, J.-H., Bischoff, C., Ahrens, C.G.M., Biester, H. (2016) Mercury(II) reduction and co-precipitation of metallic mercury on hydrous ferric oxide in contaminated groundwater. Sci. Tot. Environ. 539, 36–44.

How to cite: Schwab, L., McLagan, D. S., Kraemer, S. M., Biester, H., and Wiederhold, J. G.: Mercury isotope fractionation during dark abiotic reduction of Hg(II) by dissolved and surface-bound Fe(II) species, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-16024, https://doi.org/10.5194/egusphere-egu2020-16024, 2020.

D361 |
Carluvy Baptista-Salazar, Van Liem-Nguyen, and Sofi Jonsson

Methylation and demethylation of mercury (Hg) control the concentrations of monomethylmercury (MeHg) in natural environments, and thus the pool of Hg available for biological uptake and food web biomagnification. Typically, Hg methylation and demethylation are studied in short-term incubation experiments (< 24 h) using isotopically enriched Hg tracers. This approach has been successfully used to e.g. identify environmental hotspots of both of these processes. However, as the tracers are typically added as dissolved Hg complexes, while most ambient inorganic Hg and MeHg in e.g. sediments and soils are adsorbed onto particles, rates are recognised to not reflect true methylation and demethylation rates of ambient Hg. The traditional approach also overlooks the potential existence of refractory MeHg pools, i.e. pools of MeHg not readily available for demethylation. Previous work has, however, indicated the potential role of refractory MeHg concentrations. Jonsson et al. (Nature Com., 2014), for example, suggest up to 70% of the MeHg pool in a brackish sediment system to be in a refractory form. The occurrence of this fraction is also suggested as a key factor mediating MeHg availability in sediments by DiPasquale et al. (Environ. Sci. Technol., 2000).

We have conducted long-term incubation experiments aiming to quantify refractory MeHg pools. In short, isotopically enriched Hg tracers (Me201Hg and 198Hg, pre-equilibrated with natural waters) were incubated with lake, marsh and brackish sea water sediments and forest soils at a temperature of 10 °C for up to 6 weeks. These samples represent contrasting environments with initial MeHg concentrations ranging from 0.01 to 3.9 ng g-1 dry weight, and MeHg:Hg ratios of 0.01 to 31%. To quantify refractory pools of MeHg, we will compare steady state concentrations of MeHg:Hg ratios for added MeHg tracer with the MeHg:Hg ratio of ambient Hg. In this presentation, we will discuss the results from this study, as well as the role of refractory MeHg pools.

How to cite: Baptista-Salazar, C., Liem-Nguyen, V., and Jonsson, S.: Long-term incubations experiments: Insights about demethylation and role of methylmercury refractory pools , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18225, https://doi.org/10.5194/egusphere-egu2020-18225, 2020.

D362 |
Pablo Higueras, Karen Arroyo, JuanAntonio Campos, Jesus Peco, JoseMaria Esbrí, and Gilberto Hernández

Cinnabar mining, to obtain mercury, is still an important activity for the residents of the Sierra Gorda in Mexico, so this activity is currently source of mercury emission and possibly of other potentially toxic elements (PTE). In this work, seven study sites, located in areas with presence of exploitations of active or decommissioned mercury mines, have been studies with the aim of characterizing its occurrence and their effects on soil health.

Biogeochemical analyses have been carried out with the purpose of identifying the key factors related with nutritional and toxicological status of these soils, looking for possible relationships between mercury, PTEs and their impact on the enzymatic activity of the soil.

The values ​​obtained for total mercury ranged from 5 to 159 ppm; comparing these values with those from an uncontaminated area, we observe that all zones are above reference range (0.01 to 0.03 mg/kg) and that four of them exceed the maximum permissible limits (23 mg/kg), according to Mexican regulations. Other measured PTE elements were Pb, with a range between 18.7 to 814.1 mg/kg; Cu between 45.4 to 94.2 mg/kg; Zn between 145.1 to 555.8 mg/kg; As between 30.5 to 1590 mg/kg; and Sb between 18.3 to 169.6 mg/kg.  Comparing with other areas, anomalous concentrations of trace elements in soils with the following values are considered: Pb up to 10,000 mg/kg, Cu up to 2,000 mg/kg, Zn up to 10,000 mg/kg and As up to 2500 mg/kg; none of the determined elements exceeds these reference values. In the case of enzymatic activities, a range between 111.36 and 332.38 µgTPF g-1day-1 was obtained with dehydrogenase. These values are slightly higher compared to other Hg contaminated soils (110 µgTPF g-1day-1) described by this team. For the acid phosphatase, a range between 516.72 to 1606.34 µgPNF g-1h-1; and for alkaline phosphatase a range between 1624.92 to 4070.82 µgPNF g-1h-1. These values correspond to those measured in Sokolov, Czech Republic, ranging from 381 to 1510 µgPNF g-1h-1 for acid phosphatase and 455 to 4820 µgPNF g-1h-1 for alkaline phosphatase measured in topsoil layer from spoil heaps after brown coal mining.

Our results show that the soil has contents of PTE elements indicating low pollution degree, except for Hg, registering concentrations above the maximum permissible limits for non-industrial soils; however, the results of the enzymatic activity reflect a "good" activity. Therefore, the incidence of the presence of these metals in the soil health, as measured through enzymatic activity, does not have a significant impact and the studied soils can be considered as suitable for commercial, residential or agricultural uses.

How to cite: Higueras, P., Arroyo, K., Campos, J., Peco, J., Esbrí, J., and Hernández, G.: Mercury and other potentially toxic elements in the Sierra Gorda (Queretaro area, Mexico): affection to enzymatic activity in soils. , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18587, https://doi.org/10.5194/egusphere-egu2020-18587, 2020.

D363 |
Sergey Blagodatsky, Miriam Ehret, Frank Rasche, Imke Hutter, Regina Birner, Beloved Dzomeku, Oble Neya, Georg Cadisch, and Jens Wünsche

Unregulated surface gold mining contributes to deforestation and land degradation in Ghana and Burkina Faso (West Africa). In addition, small-scale gold mining uses a technology for gold amalgamation that pollutes the environment with mercury (Hg) and adversely affects human health. In the framework of the recently started Mercury-AMF-project we aim to reduce the environmental damage caused by mercury used in gold mining in Ghana and Burkina Faso. This will be achieved by developing and implementing novel arbuscular mycorrhizal fungi (AMF) - plant systems as a strategy to reclaim mercury-contaminated sites. The cultivation of pioneer plants on contaminated soils can reduce the mercury pollution. Symbiotic mycorrhizal associations of those plants may strengthen the potential to remediate Hg-contaminated soils.

The implementation of the project is based on the following specific activities:

  1. Characterization of the arbuscular mycorrhizal fungus (AMF) candidates in the soils of Ghana and Burkina Faso;
  2. Development of prototype AMF plant systems as an innovative strategy for the remediation of Hg-contaminated sites;
  3. Testing of mycophytoextraction methods to reduce the Hg soil concentration below threshold values;
  4. Examination of the return of Hg-contaminated sites to agricultural use and the promotion of sustainable land management in gold mining regions;
  5. Set-up of modelling approaches for the efficiency of mycophytoextraction methods and Hg plant uptake;
  6. Exploration and communication of institutional and socio-economic framework conditions for the introduction of AMF plant systems.

During the first year of the project soil and plant sampling campaigns in Ghana and Burkina Faso were organised for screening the AMF-candidates capable for symbiosis with local plant species and tolerant to the mercury pollution. Clarification of possible mechanisms of phytoremediation is the next essential component of the research: several pathways of decontamination are possible including phytostabilization, phytovolatilization and phytoextraction. Based on the first results, field experimental trials with new AMF-plant systems will be established.

How to cite: Blagodatsky, S., Ehret, M., Rasche, F., Hutter, I., Birner, R., Dzomeku, B., Neya, O., Cadisch, G., and Wünsche, J.: Myco-phytoremediation of mercury polluted soils in Ghana and Burkina Faso, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19583, https://doi.org/10.5194/egusphere-egu2020-19583, 2020.

D364 |
Nikolay Mashyanov, Sergey Pogarev, Vladimir Ryzhov, and Elena Panova

Shungite is a mineraloid consisting of up to 99 % of carbon. The first deposit was found near Shunga village (Karelia, Russia) within the Paleoproterozoic host rocks. Karelian shungites represent the greatest accumulations of carbon with reserves of up to one billion ton. Shungite matter is considered as a specific allotrope of carbon having complex globular supramolecular structure with the globules size of 5-10 nm and including 0.0001 – 0.001 % of natural fullerenes. There are two opposite opinions on the shungite origin: the deep metamorphism of the organic-rich sedimentary rocks and the pyrolysis of the mantle methane jets. In its properties, shungite occupies an intermediate position between anthracite and graphite. Mercury in coals is quite fairly studied: according to hundreds thousand analyses, the average mercury content varies in a range from ppb to few hundred ppm with a world average of 100 ppb. In contrast to coal, so far almost no data on mercury in shungites are available.

Zeeman AAS was used for determination of the total mercury concentration in shungites from Karelian shungite deposits. Surprisingly high concentration up to 12,000 ppb with an average of 2200 and median of 1100 ppb was found in all samples. That is much higher than world average value and even three times higher as compared with the mercury concentration in studied coals of the Donetsk basin (450 ppb) located within the mercury belt. The thermoscanning technique revealed a high-temperature form of mercury in shungites releasing at a temperature above 650 OC and comprising 40-45% of the total mercury. That drastically differs from the thermospectra of anthracite with the main portion of mercury being released at a temperature below 480 OC. The loss of mass for anthracite and shungite during heating to 900 OC is practically identical, whereas the loss of mercury from anthracite is much faster. As both substances consist mainly of carbon, the difference in mercury binding energy can be explained by a specific globular structure of the shungite matrix. Additional experiments on the shungite exposure to mercury in the liquid and gaseous phases showed the increased mercury release at a low temperature and no increase in the high temperature species. The occurrence of a significant portion of the uncommon high temperature species suggests that this mercury can be transported with the mantle methane jets and captured inside the stable carbon globules of the shungite.

Preliminary assessment of the mercury resources only for three proven deposits (54 million ton of shungite, Filippov, 2002) gives the value of 55 t Hg. Shungite is widely used in ferrous metallurgy, for water purification, in cosmetology, etc. Shungites have to be considered as a potential source of the mercury emissions in metallurgy. Also, shungite mercury behavior in other industrial, ecological, medical, and cosmetology applications should be studied.

How to cite: Mashyanov, N., Pogarev, S., Ryzhov, V., and Panova, E.: Mercury occurrence in shungite and coal, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5488, https://doi.org/10.5194/egusphere-egu2020-5488, 2020.

D365 |
Joan grimalt, Marco Capodiferro, Eva Junque, and Esther Marco

The Mediterranean Sea is a water body in which the concentration of mercury is much higher than in the other world seas and oceans. Most inputs of this metal originate from the general atmospheric fallout. However, in this semi-enclosed environment there are specific sources that should be identified to understand the causes of the high toxicity by this metal. A significant proportion of Mediterranean fish devoted to human consumption is above the mercury threshold set by the European Community as suitable for human consumption. The proportion is even much larger if the recommended World Health Organization threshold is considered.


Oily fish is known for containing mercury concentrations above these thresholds. Lean fish has been investigated in much fewer cases. The present study is devoted to this second fish type that constitutes a substantial component of human diet. Thus, the study of mercury and methylmercury in fish from local fishermen marketed in diverse Mediterranean sites has provided information on the exposure of diverse populations to this metal and has afforded a description of the Mediterranean areas that have received highest mercury spills.

1350 commercial seafood samples from the Western Mediterranean Sea were collected (Feb 2014-July 2019) in several sites such as Mallorca, Menorca, Eivissa, Alacant (Spain), Marseille (France), Genoa, Alguer, Civitavecchia (Italy). Samples from Egypt and the Atlantic Ocean (Senegal, Mauritania coasts) were also taken for comparison. Fish species were selected considering the most consumed by the population.

Comparison of the mercury concentrations in the specimens of the same fish species collected at different sites revealed where are the hot spots of introduction of the excess of this metal in comparison to the atmospheric fallout and allowed the identification of the source processes.

The fish species were grouped in three trophic levels, those feeding on plankton (first), on small fish and crustaceans (second) and on fish and cephalopods (third).

A considerable number of the analyzed fish species exceeded the maximum levels proposed by the European legislation, such as dusky grouper (100% of the examined specimens), common dentex (65%), conger (45%), common sole (38%), hake (26%) and angler (15%), among others. Representation of the Hg concentrations vs. weight of each specimen from the third trophic level showed a significant positive correlation, r = 0.78 (p < 0.01).

The average THg intake due to fish consumption, 0.61 µg/g ww, involved Hg estimated weekly intakes of 5.7 µg/kg bw for children aged 7-12 years and 4.4 µg/kg bw for adults. These values were higher than the provisional tolerable weekly intakes for total Hg intake recommended by FAO/WHO, 4 µg/kg bw, 140% and 110%, respectively.

How to cite: grimalt, J., Capodiferro, M., Junque, E., and Marco, E.: Mercury concentrations in diverse lean fish species of the western Mediterranean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-1702, https://doi.org/10.5194/egusphere-egu2020-1702, 2020.

D366 |
William Purves





Title: Amalgam and Dissolved Mercury Removal  A system not just a Separator




Packs Solutions LLC has developed an amalgam and dissolved mercury system that significantly reduces the mercury discharge from the dental practice. The US American Dental Association estimates that 50% of the mercury entering the waste treatment facility is from dental practices.  The system consists of an innovative chairside trap, use of pH neutral vacuum line cleaners and disinfectants, and advanced technology separator that removes the dissolved mercury from the office discharge.  The system is currently in use in the United States and is rapidly gaining popularity with wastewater treatment authorities.


The presentation provides data taken from dental offices and the affect of pH on the dissolving of amalgam in water. The average dental office generates over 14,000 ng/L of dissolved mercury that can not be removed by traditional waste treatment processes.  The system has proven to reduce the discharge to <1,000 ng/L on average.  The system requires no changes in office routine or equipment. The separator is maintenance free and the chairside trap is custom made to fit in any brand of trap.  The average annual cost in the United States is as low as $420 for one chair practice to $1300 for a 6 chair practice.




Bill Purves


Packs Solutions LLC

How to cite: Purves, W.: Amalgam and Dissolved Mercury Removal A system not just a Separator, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3069, https://doi.org/10.5194/egusphere-egu2020-3069, 2020.