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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.

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.

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.

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.

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.

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.

    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.

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.

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.

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.

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.

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.

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.

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.

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.

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.