There exists a plethora of pollutants of global concern for whom the ocean is a key part in their environmental cycle. Namely, mercury (Hg) and several persistent organic pollutants (POPs) which are subject to international treaties (e.g. Minamata Convention, Stockholm Convention) are actively exchanged between atmosphere and ocean and subsequently accumulated in the marine food web. Thus, modeling their environmental fate requires a numerical representation of atmospheric and marine physics, chemistry, and biology
Over the last 5 years 15 PhDs have been dedicated to unravel unknown processes in the global mercury cycle in the course of the EU project GMOS-Train. Many of these findings are now actively used for the ensemble modeling study performed in support of the Minamata Convention effectiveness evaluation. This multi-compartment Hg model and analysis project MCHgMAP is the first study dedicated to modeling the complete global cycle of mercuy.
In my presentation I will give an overview on recent findings on global Hg cycling in atmosphere, ocean and land and show first results of the MCHgMAP multi-compartment modeling study.
How to cite: Bieser, J.: Overview of recent advances modeling in the global mercury cycle, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21840, https://doi.org/10.5194/egusphere-egu25-21840, 2025.
Mercury (Hg) is a global pollutant with substantial risks to human and ecosystem health. By upward transport in tropical regions, mercury enters into the stratosphere, but the contribution of the stratosphere to global mercury dispersion and deposition remains unknown. Here, we find that between 5% and 50% (passing through the 400K adiabatic layer and tropopause, respectively) of the mercury mass deposited on Earth's surface is chemically processed in the lower stratosphere. Our results show the stratosphere as a unique chemical environment where elemental mercury is efficiently converted to long-lived oxidised species. Subsequent downward transport contributes substantially to the oxidised mercury burden in the troposphere. The results show that the stratosphere facilitates the global dispersion of large amounts of mercury from polluted source regions to Earth's remote environments. We find that stratospheric transport is as important as tropospheric transport in interhemispheric mercury dispersion. Future projections suggest that expected changes in atmospheric circulation will increase the transport of mercury into the stratosphere.
How to cite: Saiz-Lopez, A., Cuevas, C. A., Acuña, A. U., Añel, J. A., Mahajan, A. S., de la Torre, L., Sonke, J. E., Feinberg, A., Gomez Martin, J. C., Villamayor, J., Travnikov, O., Wang, F., Bieser, J., Francisco, J. S., and Plane, J. M. C. and the Et. al: Role of the stratosphere in the global mercury cycle , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9890, https://doi.org/10.5194/egusphere-egu25-9890, 2025.
India, as the second-largest global emitter of mercury, faces significant environmental challenges despite being a signatory to the Minamata Convention. Mercury’s toxic nature, coupled with its long-lasting presence and tendencies to bioaccumulate and biomagnify, underscores the urgency of monitoring its emissions and impacts. However, India lacks robust ground-based observation data to assess mercury's distribution and deposition comprehensively. In this study, we utilized the GEOS-Chem model with the latest inventory available at 0.25° × 0.3125° to simulate mercury dynamics over India (2015 to 2017). The results reveal that regions hosting coal-based thermal power plants and brick kilns exhibit the highest mercury deposition (100-140 µg m-2 a-1) and atmospheric concentrations (10-20 ng m-3). Sensitivity analyses further delineated the contributions of natural and Indian anthropogenic emissions to mercury deposition across India and Asia. Additionally, we evaluate the impact of Asian emissions on India’s mercury burden. This study provides insights into the spatial dynamics of mercury in India and highlights the regional interdependence of emissions. These findings can guide policymakers in formulating targeted mitigation strategies to reduce mercury emissions and their transboundary impacts effectively. Further research is needed to examine the transformation of deposited mercury into its bioaccumulative form, methylmercury, and its implications for human health.
How to cite: Bhatt, H. and Qureshi, A.: Mercury Emission Dynamics in India: Insights from Sensitivity Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15007, https://doi.org/10.5194/egusphere-egu25-15007, 2025.
Mercury (Hg) is a neurotoxic element that can bioaccumulate in aquatic food webs, posing risks to high trophic level species, including humans. While continental-scale gradients of atmospheric Hg concentration and deposition can be evaluated using national monitoring networks, regional gradients of Hg loadings remain poorly defined. Evaluation of regional Hg gradients has been limited by coarse spatial coverage of observations along with differences in standard operating procedures between measurement sites, hindering quantitative inter-site comparison.
Here, we use Hg observations in the northeastern United States coordinated by the National Atmospheric Deposition Program (NADP) to identify regional variability in Hg loadings and quantify the range of surface, chemical, and physical fluxes that can explain observed seasonal and diurnal trends. Elemental Hg (Hg0) concentration measurements between 2014 and 2020 at four key sites are used, two representing the New York City (NYC) metropolitan area (Bronx, NY and New Brunswick, NJ), and two representing rural conditions approximately 350 km north of NYC (Huntington Wildlife Preserve NY and Underhill VT). These measurements are supplemented by wet deposition measurements at several sites throughout the region along with two sites that have directly quantified Hg0 surface fluxes over northern forests for greater than one year. We construct a box model representing the NYC metropolitan area that accounts for horizontal advection, boundary layer entrainment, and wet deposition to evaluate the range of surface, chemical, and meteorological fluxes required to reproduce observed diel and seasonal Hg variability. These updated fluxes are then implemented in the GEOS-Chem-Hg chemical transport model, and its impact on regional and global deposition are evaluated.
We find that Hg0 concentrations were consistent at rural (1.22 and 1.30 at Huntington and Underhill, respectively) and urban (1.67 and 1.72 at New Brunswick and Bronx, respectively) sites but demonstrated a noteworthy difference across the urban to rural gradient. Interestingly, we find that diel variations differed across region type, with maximum summertime concentrations at urban (rural) sites occurring during the night (day). Furthermore, despite the large average gradient between sites, concentrations at urban and rural sites approached one another during turbulent daylight hours, suggesting a synoptic scale forcing on atmospheric concentrations. Despite obvious spatial and temporal gradients in observations, we find that these patterns are absent from current versions of the GEOS-Chem chemical transport model, underscoring the need to reevaluate surface, chemical, and meteorological fluxes controlling regional gradients of Hg atmospheric loadings.
How to cite: Roy, E. M., Gay, D. A., and Selin, N. E.: Regional drivers of Hg loadings informed by spatially and temporally dense observations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4562, https://doi.org/10.5194/egusphere-egu25-4562, 2025.
Significant knowledge gaps exist in the fate of mercury (Hg) and its isotopic fractionation in forests and limit the understanding of the global Hg mass budget. This study, for the first time, conducted a whole-ecosystem Hg isotope study to depict the Hg biogeochemical processes in a subtropical evergreen forest. Results show that atmospheric Hg0 is the primary source of Hg in foliage, woody biomass, throughfall water, runoff water and the food chains of birds. The studied subtropical evergreen forest is an atmospheric Hg0 sink of 57.6±43.9 μg m-2 year-1, and an atmospheric Hg2+ sink of 11.5± 6.2 μg m-2 year-1. The Hg mass-dependent fractionation Hg0 driven by the biogeochemical processes leads to a -0.69±0.58‰ in δ202Hg of atmospheric Hg0 but an insignificant shift for Δ199Hg. This study provides a protocol for quantifying the atmospheric Hg0 and Hg2+ sink over the whole forest ecosystem and the impact of vegetation on Hg0 isotopic shift; and demonstrates the use of stable Hg isotopes in tracing atmospheric Hg cycle in terrestrial ecosystems.
How to cite: Feng, X., Wang, X., Yuan, W., and Lin, J.: Cycling of elemental mercury vapor controls the sink and isotopic fractionation of atmospheric mercury in forest ecosystems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-4610, https://doi.org/10.5194/egusphere-egu25-4610, 2025.
The management options for historical drainage to improve forest productivity are highly politicized in many high latitude regions, often related to potential climate and biodiversity values. However, important consequences of this legacy and current management to mercury (Hg) mobilization and the microbial formation of methylmercury (MeHg) should also be considered. As the historical ditches age, ditch cleaning could be an option to maintain forest growth rates. However, reducing the drainage capacity by rewetting peatlands are also a viable option, to increase water holding capacity, carbon sequestration and biodiversity. While ditch cleaning may cause erosion influencing Hg mobilization, flooding of peat soil during rewetting may increase the microbial formation of MeHg. Here, we studied how both recent rewetting and ditch cleaning influence MeHg and total Hg (THg) in stream runoff across Sweden.
We used two field infrastructures, (a) a spatial study where 25 rewetted wetlands and 25 cleaned ditches distributed from north to south of Sweden were sampled during two (rewetting) or three (ditch cleaning) campaigns and (b) a temporal study where two rewetted wetlands and two cleaned ditches located in Trollberget Experimental Area in the north of Sweden that were sampled at a monthly basis both before (>1 year) and after (>2 years) rewetting or ditch cleaning. All sites at both (a) and (b) had nearby references, i.e. non-restored and non-cleaned ditches.
In the spatial study (a) THg concentrations, but not MeHg concentrations, were elevated in rewetted wetlands compared to references. Concentrations of MeHg were lower in cleaned ditches than in non-cleaned, but only in those located in forests, and not in clear-cuts. THg concentrations did not differ between cleaned and non-cleaned ditches. In the temporal study in Trollberget (b), rewetting and ditch cleaning had more pronounced effects. Both THg and MeHg increased after rewetting in one of the two wetlands, and decreased after ditch cleaning.
We suggest that the observed changes on MeHg and THg concentrations were largely driven by changes in groundwater levels, where rewetting resulted in higher levels and ditch cleaning in lower levels, which resulting in altered redox conditions stimulating or inhibiting MeHg formation. Also, altered groundwater levels affected dominating hydrological flowpaths, which influenced MeHg and THg mobilization from soils to water.
Although MeHg and THg concentrations may increase initially after rewetting, these sites may also benefit from enhancing other important ecosystem services, such as promoting carbon sequestration and providing a diversity of plants, animals, and microorganisms. This research will be an important contribution when forming guidelines concerning where and how wetlands can be restored to maximize benefits and reduce potential negative impacts.
How to cite: Eklöf, K., Zannella, A., Sikström, U., Wang, M., Maher Hasselquist, E., Laudon, H., and Wallin, M.: Effects of rewetting and ditch cleaning on total- and methylmercury concentrations in surface water , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8515, https://doi.org/10.5194/egusphere-egu25-8515, 2025.
Since humans began utilizing mercury, pollution has increased atmospheric Hg seven-fold. Mercury (Hg) contamination is the single largest cause of waters in the European Union failing to meet the standards of the EU Water Framework Directive. Peatlands, which have accumulated a legacy of past atmospheric Hg pollution, are major sources of Hg contamination in downstream aquatic ecosystems. Despite peatlands having accumulated Hg for millennia, independent lines of research indicate that some northern peatlands are now returning Hg to the atmosphere. This raises questions about what controls the fate of the pollution legacy Hg stored in peatlands. We hypothesize that legacy Hg accumulated in peat during earlier periods of higher atmospheric Hg pollution is no longer in balance with the lower Hg levels of the contemporary atmosphere, leading to net Hg evasion. Several methodological advances were applied to test this hypothesis on a 2000-year chronosequence of mires created by isostatic uplift along the northern coast of Sweden as well as the nearby Degerö peatland that is even older. Despite uniform climate and atmospheric Hg concentrations across the 15 km extent of the chronosequence, the stock of Hg differs by a factor of two. Novel Hg eddy covariance quantified the Hg exchange between the land and atmosphere. Distributed measurements of dissolve gaseous elemental mercury (GEM) in shallow peat groundwater quantified seasonal variation in a potential source of the evading Hg. Natural abundance of Hg isotopes and community-level expression profiling of microbial metabolisms identified the role of specific processes in the transformation of Hg within peat profiles along the chronosequence. This paper reports on puzzle pieces that have fallen into place, such as isotopic evidence for the role of photoreduction in producing GEM, and the challenges that remain to complete the picture.
How to cite: Bishop, K., Li, C., and Osterwalder, S.: The fate of industrial-era mercury in peatlands revealed with micrometeorology, isotopes, paleoecology, genomics, and an ice-age, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13151, https://doi.org/10.5194/egusphere-egu25-13151, 2025.
Catchment properties may influence the mercury (Hg) cycle by affecting Hg speciation, transport, and bioavailability, though their role is not fully understood. In aquatic systems, the bioaccumulation of methylmercury (MeHg) poses significant risks to wildlife and human health. Despite its importance, our understanding of the relationships between catchment properties and the concentrations of total Hg and MeHg in the environment and at the base of the aquatic food web remains incomplete.
In this study, we explore how catchment properties relate to Hg concentrations and speciation in high-latitude Swedish catchments encompassing tundra, birch, and boreal forest ecosystems. Sampling was conducted in August 2020 across 18 streams and 8 lakes distributed along a climatic and vegetation gradient (67.5°–68.5°N, 18°–21.5°E). We measured Hg species and over 60 ancillary parameters and employed a PARAFAC model to examine the role of dissolved organic matter (DOM) characteristics in aquatic Hg dynamics.
Using multivariate analysis, we found distinct differences in water type and catchment systems based on the ancillary parameters. Total Hg and MeHg concentrations followed the trend boreal > birch > tundra for both lakes and streams, with lakes generally showing higher MeHg levels and MeHg% compared to streams. Our findings suggest that terrestrial humic-like DOM plays a key role in transporting Hg from terrestrial systems to and within aquatic environments, thereby influencing aquatic Hg concentrations. Microbial and algal DOM, on the other hand, appears to promote Hg methylation processes.
How to cite: Gindorf, S., Baptista-Salazar, C., Liem-Nguyen, V., Giesler, R., Mörth, C.-M., and Jonsson, S.: Catchment Properties control Mercury Speciation in Streams and Lakes across a Sub-Arctic Climate Gradient , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-928, https://doi.org/10.5194/egusphere-egu25-928, 2025.
Oxygen deficiency is increasing in coastal zones and the global ocean, potentially promoting methylmercury (MeHg) formation. Intensive work has been done to understand the factors controlling the methylation of Hg(II) to MeHg in open seas and oceans, but these processes are understudied in fjord systems which also undergo oxygen decreases. We hypothesized that in oxygen-deficient fjords, MeHg formation is influenced by (i) the Hg(II) bioavailability, as mainly controlled by Hg(II) complexes with sulfide and, (ii) the presence of microorganisms able to do Hg methylation (i.e., carrying and expressing hgcAB genes). We studied a fjord in northern Norway with a 40 m deep redox stratified water column to better understand the underlying factors/processes driving MeHg concentrations in zones affected by oxygen deficiency. Along the 40 m depth water column, O2 concentrations decreased from 440 µM to non-detectable, and H2S concentrations increased with depth from non-detectable to >600 µM concentrations. Total Hg and MeHg concentrations, methylation (km) /demethylation (kd) rate constants and hgcAB gene abundance were determined at several depths along the vertical redox gradient. MeHg concentrations varied from 0.1 to 5.1 pM with a peak at 10 m depth, after the redox transition zone (6 – 10 m). The MeHg production, determined as the Hg(II) methylation rate constant (km), followed a similar vertical pattern with negligible km in the oxic zone and an increase with depth up to a maximum of ≈0.0001 h-1 under anoxic condition. Statistical analysis showed a positive relationship between km and the concentration of dissolved Hg(II)-sulfide complexes revealing the importance of these compounds in regulating the Hg(II) availability for MeHg formation in this environment. Metagenomic analysis detected hgcAB genes in samples with low oxygen concentrations, highlighting the possible presence of Hg methylators in this ecosystem. Coupling the chemical and microbial analyses, both Hg(II) availability and the presence and abundance of hgcAB-carrying microorganisms suggest the in-situ MeHg formation in this redox stratified fjord system. The spread of oxygen-deficient coastal zones, e.g. due to global warming and nutrient inputs, is expected to increase Hg(II) bioavailability and expand the niches for Hg methylators. Both these consequences are expected to promote higher MeHg concentrations in coastal areas.
How to cite: Cossart, T., Dordal-Soriano, J., Zhong, M., Bratthäll, T., Capo, E., G. Bravo, A., and Björn, E.: Methylmercury formation in an ice-covered fjord system with redox stratified water column, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15520, https://doi.org/10.5194/egusphere-egu25-15520, 2025.
Understanding the mechanisms governing mercury (Hg) bioavailability to marine phytoplankton is crucial for evaluating its ecological and biogeochemical impacts. Dissolved organic matter (DOM) plays a central role in modulating the mobility, complexation, and bioavailability of monomethylmercury (MMHg), a highly toxic Hg species. This study investigates how the origin of DOM (terrestrial, marine, and phytoplankton-derived exudates) affects MMHg complexation and cellular uptake by marine phytoplankton under controlled laboratory conditions.
Using a single phytoplankton culture and enriched stable Hg isotopes, we simultaneously tracked the uptake dynamics of MMHg complexed with different DOM sources as well as uncomplexed MMHg ions. Our results revealed that total MMHg uptake decreased with increasing dissolved organic carbon (DOC) concentrations, regardless of DOM origin. Notably, no significant differences were observed in MMHg uptake dynamics when comparing DOM of different origins at similar MMHg concentrations. However, we observed increased internalization of MMHg when complexed with both terrestrial and marine DOM. Specifically, organic complexation with DOM from both terrestrial and marine sources reduced MMHg's ability to bind to ligands on the algal surface (phycosphere) but did not hinder its passage across the cell membrane, ultimately enhancing its bioavailability.
These findings offer novel insights into the interaction between DOM composition and MMHg bioavailability, advancing our understanding of mercury dynamics in marine ecosystems. The study underscores the critical role of DOM characteristics in influencing MMHg bioaccumulation and provides valuable data for refining models of mercury cycling in aquatic environments.
How to cite: Garcia Arevalo, I., Gindorf, S., Bérard, J. B., Thomas, B., Jonsson, S., and Knoery, J.: Using enriched stable isotopes to elucidate marine phytoplankton cellular uptake mechanisms and bioavailability of MMHg bound to different natural DOM composition, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20239, https://doi.org/10.5194/egusphere-egu25-20239, 2025.
Posters on site: Fri, 2 May, 08:30–10:15 | Hall X1
Over recent decades, Svalbard's climate has undergone significant transformation, driven by Arctic Amplification. Rising temperatures, retreating sea ice, and the intensification of extreme events have become increasingly prevalent. However, within this nearly consistent trend of warming, 2020 emerged as an anomaly, marked by unusually low temperatures, a strong polar vortex, and extensive sea ice coverage throughout the year. Two sampling campaigns were conducted during the snow season in Ny-Ålesund (Svalbard): one during a “warm” year (November 2018 to May 2019) and the other during a “cold” year (November 2019 to May 2020). These campaigns aimed to investigate the potential effects of the distinct climatic conditions of the “cold year” on the biogeochemical cycle of mercury (Hg) in surface snow. Mercury, a toxic element, has been extensively studied in polar regions. While many studies have sought to address changes in the Hg biogeochemical cycle under shifting climatic and atmospheric conditions, uncertainties remain—particularly regarding how variations in sea ice extent and duration may influence Hg deposition in the Svalbard archipelago and the Arctic as a whole. It is well known that sea ice releases reactive bromine species during spring, which can directly influence Hg deposition through atmospheric mercury depletion events (AMDEs) or, more broadly, by promoting Hg oxidation and deposition. Using the “warm” and “cold” years as case studies, we explored whether the significant increase in sea ice extent observed in the Kongsfjord during the cold year influenced Hg deposition. Although we observed an increase in ozone depletion events (which are primarily linked to bromine release from sea ice) during the cold year, we found no direct evidence of a corresponding increase in Hg content in snow. This suggests either that the sea ice increase during the cold year was insufficient to enhance Hg deposition through bromine emissions or that sea ice and its associated emissions do not play a primary role in controlling the Hg biogeochemical cycle.
How to cite: amoruso, V., spagnesi, A., scoto, F., and spolaor, A.: Evaluation of mercury concentrations in Svalbard surface snow based on meteorological parameters, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-642, https://doi.org/10.5194/egusphere-egu25-642, 2025.
The investigation of mercury photoreduction in snow can be challenging due to the complex nature of the snowpack and of the surrounding environment from both physical proprieties and chemical composition1. The mercury air-snow interaction and exchange driven by the photoreduction in snow plays a central role in its geochemical cycling. Experiments in natural world snowpack have clearly demonstrate the occurrence of mercury re-emission2. However, the influences from different physical proprieties and chemical composition is virtually impossible to be disentangle in studies carried out in the natural environment. Laboratory studies in a closed photochemical reactor provide valuable proof of concept to better understand the photoreduction process and its reaction kinetics in a controlled environment where chemical and physical parameters can be (semi)controlled and modified1–3. Here we propose an experimental scheme to simulate the photochemical emission of gaseous mercury from urban snow at cold temperatures, using a custom-made LED solar simulator. Multiple factors such as the irradiating wavelengths were examined and their role in affecting the determined mercury photoreduction process was studied. Specific attention was made in the cleanliness of the experimental set-up and on the air flow above the snow to optimise the condition in which experiment will be perform. The system development was tested at the University of Manitoba (Winnipeg, Canada) for multiple experiments. They showed the role of the UV radiation in the mercury photoreduction activation, with an increase in GEM concentration when the light was on and a decrease over time, supporting that the experiment set up is valid to evaluate the UV driven mercury photoreduction in the snow, and the collection and measurement of the produced GEM. The estimation of a preliminary reduction rate constant (kr) was also possible, finding a rate constant ranging from 0.712 h-1 to 0.757 h-1. The system represents the technical base to further mercury laboratory snow photochemical experiment in different conditions including the possibility to modify the chemical composition of the snow, the inlet air composition (for ex. by implementing an ozone producer system) and physical parameters (temperature, solar radiation, relative humidity).
- Dommergue, A., Bahlmann, E., Ebinghaus, R., Ferrari, C. & Boutron, C. Laboratory simulation of Hg0 emissions from a snowpack. Anal Bioanal Chem 388, 319–327 (2007).
- Lalonde, J. D., Poulain, A. J. & Amyot, M. The Role of Mercury Redox Reactions in Snow on Snow-to-Air Mercury Transfer. Environ. Sci. Technol. 36, 174–178 (2002).
- Mann, E. A., Mallory, M. L., Ziegler, S. E., Tordon, R. & O’Driscoll, N. J. Mercury in Arctic snow: Quantifying the kinetics of photochemical oxidation and reduction. Science of The Total Environment 509–510, 115–132 (2015).
How to cite: Celli, G., Spolaor, A., Cairns, W., Armstrong, D., Gao, Z., and Wang, F.: Developing a method for measuring mercury photoreduction in snow with a LED Solar Simulator , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-31, https://doi.org/10.5194/egusphere-egu25-31, 2025.
Studying atmospheric mercury (Hg) isotopic composition is crucial for understanding the complex biogeochemical cycling of mercury, a global pollutant with significant environmental and health impacts. Mercury isotopes provide valuable information about the sources, transformation processes, and deposition pathways of Hg in the environment, allowing researchers to trace its movement and identify the contributions from natural versus anthropogenic sources. Studies of atmospheric Hg isotopic composition have gained significant momentum in recent years, with over 80% of the relevant literature published within the past 7 years. While the analytical capabilities of multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) for Hg isotopic measurements have been extensively investigated and reviewed, certain analytical challenges remain, particularly related to the preconcentration methods used prior to MC-ICP-MS analysis. Our study investigates these constraints, focusing on which preconcentration techniques are optimal for measuring isotopic compositions of various atmospheric Hg forms. The results indicate that direct gold sampling, which is typically used to measure gaseous elemental mercury (GEM), also captures 20-80% of gaseous oxidized mercury (GOM) unintentionally. Thereby, a fraction between GEM and total gaseous mercury (TGM) is measured. Similarly, particulate-bound mercury (PBM) membrane sampling not only measures PBM but also inadvertently captures over 50% of GOM. These findings suggest that many current datasets may not represent pure end-members but rather mixed samples of GEM/TGM or PBM/GOM, potentially leading to inaccuracies in isotopic mixing models. Based on our findings, we offer several recommendations for future analyses to improve the accuracy and reliability of atmospheric Hg isotope studies.
How to cite: Gačnik, J., Živković, I., and Horvat, M.: Instights from Atmospheric Mercury Isotopes: Analytical Considerations, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1297, https://doi.org/10.5194/egusphere-egu25-1297, 2025.
Speciation of atmospheric gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) controls the rate of deposition of these two forms to the land and oceans. What chemicals lurk behind the acronyms GOM and PBM? What processes interconvert these forms between each other and gaseous elemental mercury (Hg)? These questions cannot be answered independently of each other, as they are tightly coupled. Even in the case of GEM, in addition to direct emissions from land and oceans it can be formed directly in the atmosphere, e.g., by thermal dissociation of labile Hg(I) intermediates and photochemical dissociation of relatively stable Hg(II) compounds, GOM and PBM, whose chemical makeup is still poorly known.The challenge of chemically speciating Hg(II), in addition to its ultra-trace concentration levels, is compounded by its labile nature. Furthermore, it is highly likely that there are two kinds of GOM in the atmosphere: the first comes directly from the photochemical oxidation of GEM while the second is a result of volatilization of PBM. In essence, GOM of the second kind is formed when the first kind, taken by aerosol particles, undergoes particle-phase processing and then re-enters the gas phase in a different chemical form. For instance, following this scheme, BrHgOH from the photochemical oxidation of GEM mediated by Br, ozone, and volatile organic compounds can be taken by sea-salt aerosol and converted to mercuric chloride, which would re-enter the gas phase to be identified as GOM. A similar uptake-reemission process to form mercuric chloride might be even possible on continental urban aerosols, depending on the values of rate constants and equilibrium constants of relevant reactions, not all of which have been fully identified. This presentation will provide an overview of the above mentioned processes and their roles in controlling the speciation of atmospheric mercury in all of its forms.
How to cite: Khalizov, A.: Speciation and interconversion of atmospheric mercury, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3218, https://doi.org/10.5194/egusphere-egu25-3218, 2025.
Mercury (Hg) emissions into the atmosphere have significant environmental and health impacts, making accurate measurement and calibration of Hg crucial for effective monitoring and mitigation strategies. Measuring the different forms of atmospheric mercury, such as gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM), and their behavior in both emissions and ambient air is essential for developing comprehensive approaches to control mercury pollution. Currently, common calibrations for GOM in emissions rely on liquid evaporative calibrators, such as HovaCal and Optoseven. However, new calibration methods are emerging to address the limitations of existing approaches. The challenges associated with GOM calibration become even more pronounced at ambient GOM concentrations, where accurate calibration is essential for reliable measurements. In our work, we validated and compared multiple GEM and GOM calibration sources over several years. We also developed a novel nonthermal plasma source that can be used for GOM calibration at both ambient and emission concentrations of Hg. Our research highlights the importance of precise calibration techniques to enhance the comparability of Hg measurement results across different studies and regions. By improving calibration accuracy, we can better evaluate the effectiveness of the Minamata Convention and other efforts aimed at reducing mercury emissions globally.
How to cite: Zivkovic, I., Gacnik, J., and Horvat, M.: Comparison of Calibration Approaches for Mercury in Emissions and Ambient Air, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1167, https://doi.org/10.5194/egusphere-egu25-1167, 2025.
Concentrations of gaseous elemental mercury (GEM) have been monitored at the Lulin Atmospheric Background Station (LABS; 120.87ºE, 23.47ºN, 2862 m a.s.l.), a high mountain forest site in central Taiwan, since April 2006. A significant decreasing trend in GEM at a rate of -1.1% yr-1 (-0.018 ng m-3 yr-1) was found between 2007 and 2022, comparable to the decreasing trends observed in other regions. Multiscale temporal variations of GEM concentrations were studied and distinguished by the application of the Hilbert-Huang transformation (HHT). Diurnal, monthly, annual, and inter-annual GEM cycles were identified. Daily GEM variability at the LABS is controlled by the local upslope movement of boundary layer air, whereas seasonal variability is driven by regional air mass origins and transport paths. The amplitude of the GEM concentration inter-annual variability (IAV) is greater than those of diurnal and seasonal variabilities, highlighting the importance of GEM IAV and the associated driving factors. The IAV cycles for the SOI were similar in frequency to the GEM IAV cycles but negatively correlated, revealing the dependency of GEM IAV on climatology variations (e.g., ENSO). Large-scale atmospheric circulation played an important role in modulating GEM IAV. In El Niño years, the westerly was enhanced with more air masses passing India, northern Indochina Peninsula, and southwest and southeast China before arriving LABS, causing elevated levels of atmospheric Hg. On the other hand, the westerly weakened and deviated from Taiwan in La Niña years. This caused more air masses from the Pacific Ocean, resulting in lower atmospheric Hg concentrations. Furthermore, the relationship between ENSO and GEM is sensitive to extreme events (e.g., 2015−2016 El Niño), resulting in perturbation of the long-term trend and atmospheric Hg cycling. Future climate change will likely increase the number of extreme El Niño events and, hence, could alter atmospheric Hg cycling and influence the effectiveness evaluation of the Minamata Convention on Mercury.
How to cite: Sheu, G.-R., Hsiao, P.-T., Nguyen, L. S. P., and Yen, M.-C.: Trend and inter-annual variability of atmospheric mercury concentrations at a mountain site in Taiwan, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3061, https://doi.org/10.5194/egusphere-egu25-3061, 2025.
Accurate emissions estimation is essential for the impact evaluation and for designing effective mitigation actions. The Emissions Database for Global Atmospheric Research (EDGAR) provides independent estimates of speciated mercury emissions by sector at global and national levels, and emissions gridmaps of 0.1 x 0.1 degree resolution for the period 1970-2022. The trend analysis shows that in this period mercury emissions increased by 123% reaching the level of 1863 tonnes in 2022. At sectorial level, the emissions from chlor-alkali, which had a great share in 1970 (14%), decreased by 96% whereas the emissions from cement production, which had a share of 4% in 1970 increased by 421% contributing to the total global emissions in 2022 by 10%. Special attention is given to the artisanal small-scale gold mining (ASGM) sector due to its significant share of 16% in 1970 and of 47% in 2022; we will provide an insight on the uncertainty related to the methodology and data availability, the drivers leading to an increase of 567%, and on global spatial distribution of mercury emissions.
The impact of increases in fuel consumption (303%) together with the implementation of mitigation technologies on the levels of mercury emissions is investigated for power generation sector, which showed an increase of 100% in the period 1970-2022. We developed a “no end-of-pipe (EoP) ex-post scenario” to analyse the impact of the mitigation of mercury emissions by end-of-pipe abatement measures in the power generation sector. Figure 1 illustrates the global mercury emissions from fuel combustion in power generation over five decades together with the levels of emissions in the “no end-of-pipe (EoP) ex-post scenario”. The mitigation measures implementation in this sector accounted for 437 tonnes of avoided mercury emissions in 2020.
The trend analysis will be extended to look at the regional particularities focusing on the ten IPCC Continental Regions. The relevant findings will be presented together with the uncertainties for each sector.
Figure 1. Mercury emissions from fuel combustion in power generation: a) mercury emissions over five decades are represented in green and the emissions from no end-of-pipe (EoP) ex-post scenario are represented in blue; the bars on the graph illustrate the fuel share by type, b) emissions shares by sector in 2020 for the three continents for which the contribution from power generation sector is important.
How to cite: Muntean, M., Crippa, M., Guizzardi, D., Pagani, F., Becker, W., Banja, M., Schaaf, E., and Simonati, A.: Mercury emissions trends over five decades in a technology-based global inventory., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8960, https://doi.org/10.5194/egusphere-egu25-8960, 2025.
Mercury (Hg) is a strong neurotoxin with substantial dangers to human health. Hg undergoes active global cycles, and the emission
sources there of can also be geographically relocated through economic trade. Through investigation of a longer chain of the global
biogeochemical Hg cycle from economic production to human health, international cooperation on Hg control strategies in Minamata
Convention can be facilitated. In the present study, four global models are combined to investigate the effect of international trade on
the relocation of Hg emissions, pollution, exposure, and related human health impacts across the world. The results show that 47% of
global Hg emissions are related to commodities consumed outside of the countries where the emissions are produced, which has
largely influenced the environmental Hg levels and human exposure thereto across the world. Consequently, international trade is
found to enable the whole world to avoid 5.7 × 105 points for intelligence quotient (IQ) decline and 1,197 deaths from fatal heart
attacks, saving a total of $12.5 billion (2020 USD) in economic loss. Regionally, international trade exacerbates Hg challenges in less
developed countries, while resulting in an alleviation in developed countries. The change in economic loss therefore varies from the
United States (−$4.0 billion) and Japan (−$2.4 billion) to China (+$2.7 billion). The present results reveal that international trade is a
critical factor but might be largely overlooked in global Hg pollution mitigation.
How to cite: Chang, R. and Zhang, Y.: International trade shapes global mercury–related health impacts, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1284, https://doi.org/10.5194/egusphere-egu25-1284, 2025.
Rewetting of previously drained wetlands is a strategy to mitigate the effects of climate change via increased carbon sequestration as well as improve water holding capacity and biodiversity in the forest landscape. The damming of watercourses by beavers creates similar water retention features. In both cases, the inundation of forest soils may affect the mobilization of mercury (Hg), and subsequent production of toxic and bioavailable methylmercury (MeHg), due to the generation of anoxic conditions where microbial methylators can proliferate. Elevated MeHg concentrations in water may accumulate in the food web and increase the already high Hg levels in inland fishes in Sweden. Here, we studied the impacts of rewetting and beaver ponds on total Hg (THg) and MeHg concentrations in runoff water collected throughout Sweden.
A total of 72 sites were sampled, comprising rewetted sites (n=15), beaver dams (n=15), and pristine wetlands (n=12). Each of the inundated sites was paired with a nearby reference, i.e. rewetted sites were compared to drained wetlands (n=15) and beaver ponds to watercourses without beaver dams (n=15).
Concentrations of MeHg were higher in runoff from both rewetted and beaver-impacted sites compared to natural wetlands, but only beaver ponds exhibited significantly higher MeHg concentrations relative to their reference sites. Meanwhile, THg concentrations were significantly higher in rewetted sites compared to drained sites. A critical difference between rewetted sites and inundations caused by beavers is that the latter will be found on a wide variety of land types, whereas the former typically represent previously drained wetlands, often peatlands. These results indicate that rewetting drained wetlands increases the mobilization of THg but does not promote the formation of MeHg to the same extent as inundation of other terrestrial soils, including upland soils, by beavers.
How to cite: Wang, M., Andersson, K., Wallin, M., Ecke, F., and Eklöf, K.: Methylmercury in surface runoff from beaver- and human-induced inundations in the forest landscape, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8361, https://doi.org/10.5194/egusphere-egu25-8361, 2025.
Peatlands are long-term sinks of mercury (Hg) and hotspots of neurotoxic methyl-Hg production. Dissolved gaseous mercury (DGM or Hg0aq) is a key component in peatland Hg cycling due to its high volatilization and potential oxidation to HgII, the precursor of neurotoxic methyl-Hg (MeHg). Despite the importance of DGM in Hg cycling, DGM dynamics in peatlands remain poorly understood. Here, we present temporal changes in porewater DGM concentrations in six different boreal peatlands with a gradient of trophic levels and chronologies. DGM concentrations are significantly higher in older, more oligotrophic ones (> 2500 years) than in younger, more mesotrophic peatlands (< 1500 years). There is also a more pronounced seasonal variation in older, more oligotrophic peatlands, with a marked DGM peak in summer. The lower DGM concentrations in younger, more mesotrophic peatlands are likely due to stronger oxidation capacity in the presence of chloride and more nutrients, leading to less DGM production in the porewater and more bioavailable HgII for methylation. Our study suggests that older, more oligotrophic peatlands with lower MeHg concentrations likely have the potential to evade more Hg0 into the atmosphere in the boreal landscape.
How to cite: Li, C., Zhu, W., Osterwalder, S., Skyllberg, U., and Bishop, K.: Dissolved gaseous mercury in peat porewater increases as trophic status decreases, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12800, https://doi.org/10.5194/egusphere-egu25-12800, 2025.
Mercury (Hg) progressively accumulates in soils through processes such as vegetation uptake, litterfall, throughfall, and direct deposition. Soils constitute the largest reservoir of Hg, with surface soil stocks estimated at 235 to 1150 Gg. Despite its significance as a toxic neuropollutant, current environmental policies often overlook the remobilization of legacy Hg stocks stored in soils. However, the stability of soils Hg stocks, as well as the pathways and magnitudes of potential remobilization, remain poorly quantified. Due to the strong affinity of Hg for organic carbon (OC), their cycles are tightly coupled. Consequently, changes affecting OC stability have direct implications for soil Hg stocks. This is particularly critical for permafrost soils, which hold substantial amounts of OC and of Hg (72 Gg in the top 0-30 cm) but are highly vulnerable to climate change-driven thawing.
To address this gap, we are extending the ORCHIDEE-MICT-PEAT-LEAK land surface model, which mechanistically represents the production, transport, and transformation of OC in soils and permafrost, by integrating the Hg cycle. The model will be evaluated against observational data, such as regional surface Hg stock maps and vertical soil core profiles.
Once validated, the model will enable quantification of Hg fluxes emitted into the atmosphere or leaching into rivers. Additionally, simulations under various CMIP6 climate change scenarios will assess the stability of soil Hg stocks across temperate and permafrost regions. This work aims to improve understanding of Hg dynamics in a warming climate and inform strategies for managing Hg risks.
How to cite: Sereni, L., Guenet, B., and Angot, H.: Modeling the stability and remobilization of mercury in temperate and permafrost soils under climate change with ORCHIDEE-MICT-PEAT-LEAK, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-2710, https://doi.org/10.5194/egusphere-egu25-2710, 2025.
Mercury is one of the most problematic elements in the environment due to its persistence, bioaccumulation, and transfer across different trophic levels of the food chain. One of the environments where this element poses the greatest challenges is the coastal-marine ecosystem, owing to its rich biodiversity. Within these environments, anthropized estuarine areas, such as port zones, present increased issues because of the significant accumulation of sediments that act as reservoirs for this contaminant.
In Asturias (northern Spain), the Port of Llanes, located in a small town in the eastern part of the region, has shown elevated mercury concentrations in sediments over the last 20 years, requiring detailed monitoring and investigation. This study provides an initial approach to the issue, examining mercury concentrations, dispersion, associations, and speciation in sediments collected from the port.
The results revealed that mercury concentrations in the sediments ranged from 0.07 to 2.98 µg g⁻¹, with higher concentrations associated with finer-grained sediments and increased organic matter content. These concentrations exceed contamination thresholds established by Spanish legislation regarding port dredging, and certain samples tested exhibited toxicity levels harmful to organisms. Granulometric fractionation of the samples showed that 70% of the mercury was associated with particle sizes <63 µm, while up to 85% was associated with particles <125 µm.
Thermal speciation analysis was conducted to identify the predominant mercury species and their potential association with the observed toxicity. The results indicated three main mercury species in the sediments. Mercury associated with oxides was the most abundant, followed by mercury bound to organic matter. Finally, mercury associated with sulfur (e.g., cinnabar) was the least abundant of the three.
These findings validated the results of mercury granulometric fractionation, as the identified species were closely linked to finer sediment fractions. Furthermore, they allowed the formulation of a hypothesis regarding the origin of mercury in these sediments. In this context, since there is no identifiable local source of mercury release into the coastal environment, the hypothesis of a natural origin for these mercury concentrations gains relevance. Studies on groundwater in the area have reported significant mercury levels, suggesting that the geological substrate is the most likely source of these anomalous concentrations.
Future research should focus on conducting a more detailed study of the immediate coastal strip surrounding the port to validate these preliminary findings.
How to cite: García Ordiales, E., Barquero, J. I., Morales Laurente, J. A., Navarro Murillo, E., Rico Fernandez, P., Cienfuegos Suarez, P., and Higueras, P.: Mercury in Coastal-Marine Environments: A Case Study in the Port of Llanes, Asturias (Northern Spain), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9059, https://doi.org/10.5194/egusphere-egu25-9059, 2025.
Mercury accumulates in the deep sea, but its ecological impact on deep-sea ecosystems remains poorly understood. We conducted an analysis of 32 sediment cores, comprising 101 layers for the study of metagenomes, and additional 41 global reference sediment metagenomes. These sediment cores were collected from two deep-sea regions: the South China Sea (SCS) and Mariana Trench (MT), followed by revealing high mercury accumulation in the SCS. In these metagenomes, we found that the mercury methylation genes hgcA/B as detoxification regulators were abundant in marginal seas but negligible in open oceans. Instead of taking the Wood-Ljungdahl pathway as methyl group donor, some Hg-methylating microorganisms affiliated with Desulfobacterota, Spirochaetota, and Zixibacteria in the deep-sea sediments have the potential to utilize osmolyte-derived trimethylamine for methylation. The demethylation gene merB was widely distributed and exhibits higher abundance in the open ocean. Moreover, we identified a large number of novel Hg demethylating taxa that are associated with horizontal transfer of the merB gene potentially involving methane generation. Our results expand the diversity of Hg-metabolizing taxa and reveal their unique ecophysiological adaptations in deep-sea sediments.
How to cite: Li, Z., Qian, H., Zhu, Y.-G., and Wang, Y.: Potential biotransformations of mercury in marine sediments across marginal slope to hadal zone, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9385, https://doi.org/10.5194/egusphere-egu25-9385, 2025.
