Atmospheric Mercury Transfer to Peat Bogs Dominated by Gaseous Elemental Mercury Dry Deposition

Abstract. One of the most important processes in the global mercury biogeochemical cycling is the deposition of atmospheric mercury, including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM), to terrestrial surfaces. In this paper, methods for the observation of wet, dry, litterfall, throughfall, and cloud/fog deposition and models for mercury dry deposition are reviewed. Surrogate surface methods with cation exchange membranes are widely used for GOM dry deposition measurements, while observation methods for GEM dry deposition are more diverse. The methodology for Hg wet deposition is more mature, but the influence of cloud/fog scavenging is easy to neglect. Dry deposition models for speciated mercury have high uncertainties owing to the presence of sensitive parameters related to GOM chemical forms. Observation networks for mercury wet deposition have been developed worldwide, with the Global Mercury Observation System (GMOS) covering the northern hemisphere, the tropics, and the southern hemisphere. Wet deposition implies the spatial distribution of atmospheric mercury pollution, while GOM dry deposition depends highly on the elevation. Litterfall Hg deposition is crucial to forests. Urban areas have high wet deposition and PBM dry deposition because of high reactive mercury levels. Grasslands and forests have significant GOM and GEM dry deposition, respectively. Evergreen broadleaf forests bear high litterfall Hg deposition. Future research needs have been proposed based on the current knowledge of global mercury deposition to terrestrial surfaces.

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Simulation of atmospheric mercury depletion events (AMDEs) during polar springtime using the MECCA box model

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-7165-2008 ◽

2008 ◽

Vol 8 (23) ◽

pp. 7165-7180 ◽

Cited By ~ 35

Author(s):

Z.-Q. Xie ◽

R. Sander ◽

U. Pöschl ◽

F. Slemr

Keyword(s):

Aqueous Phase ◽

Ozone Depletion ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Box Model ◽

Rate Coefficients ◽

Mercury Species ◽

Phase Reaction ◽

Gaseous Elemental Mercury ◽

Sea Salt Aerosol

Abstract. Atmospheric mercury depletion events (AMDEs) during polar springtime are closely correlated with bromine-catalyzed tropospheric ozone depletion events (ODEs). To study gas- and aqueous-phase reaction kinetics and speciation of mercury during AMDEs, we have included mercury chemistry into the box model MECCA (Module Efficiently Calculating the Chemistry of the Atmosphere), which enables dynamic simulation of bromine activation and ODEs. We found that the reaction of Hg with Br atoms dominates the loss of gaseous elemental mercury (GEM). To explain the experimentally observed synchronous depletion of GEM and O3, the reaction rate of Hg+BrO has to be much lower than that of Hg+Br. The synchronicity is best reproduced with rate coefficients at the lower limit of the literature values for both reactions, i.e. kHg+Br≈3×10−13 and kHg+BrO≤1×10−15 cm3 molecule−1 s−1, respectively. Throughout the simulated AMDEs, BrHgOBr was the most abundant reactive mercury species, both in the gas phase and in the aqueous phase. The aqueous-phase concentrations of BrHgOBr, HgBr2, and HgCl2 were several orders of magnitude larger than that of Hg(SO3)22−. Considering chlorine chemistry outside depletion events (i.e. without bromine activation), the concentration of total divalent mercury in sea-salt aerosol particles (mostly HgCl42−) was much higher than in dilute aqueous droplets (mostly Hg(SO3)22−), and did not exhibit a diurnal cycle (no correlation with HO2 radicals).

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Speciated Atmospheric Mercury during Haze and Non-haze Days in an Inland City in China

10.5194/acp-2016-467 ◽

2016 ◽

Author(s):

Qianqian Hong ◽

Zhouqing Xie ◽

Cheng Liu ◽

Feiyue Wang ◽

Pinhua Xie ◽

...

Keyword(s):

Elemental Mercury ◽

Atmospheric Mercury ◽

Central China ◽

Mercury Emissions ◽

Gaseous Elemental Mercury ◽

Enhanced Production ◽

Mercury Transport ◽

Haze Pollution ◽

The Mean ◽

Haze Days

Abstract. Long-term continuous measurements of speciated atmospheric mercury were conducted at Hefei, a mid-latitude inland city in east central China, from July 2013 to June 2014. The mean concentrations (± standard deviation) of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particle-bound mercury (PBM) were 3.95 ± 1.93 ng m−3, 2.49 ± 2.41 pg m−3 and 23.3 ± 90.8 pg m−3, respectively, during non-haze days, and 4.74 ± 1.62 ng m−3, 4.32 ± 8.36 pg m−3 and 60.2 ± 131.4 pg m−3, respectively, during haze days. Potential source contribution function (PSCF) analysis suggested that the atmospheric mercury pollution during haze days was caused primarily by local mercury emissions, instead of via long-range mercury transport. In addition, the disadvantageous diffussion during haze days will also enhance the level of atmospheric mercury. Compared to the GEM and RGM, change in PBM was more sensitive to the haze pollution. The mean PBM concentration during haze days was 2.5 times that during non-haze days due to elevated concentrations of particulate matter. A remarkable seasonal trend in PBM was observed with concentration decreasing in the following order in response to the frequency of haze days: autumn, winter, spring, summer. A distinct diurnal relationship was found between GEM and RGM during haze days, with the peak values of RGM coinciding with the decline in GEM. Using HgOH as an intermediate product during GEM oxidation, our results suggest that NO2 aggregation with HgOH could explain the enhanced production of RGM during the daytime in haze days. Increasing level of NOx will potentially accelerate the oxidation of GEM despite the decrease of solar radiation.

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Gaseous mercury in coastal urban areas

Environmental Chemistry ◽

10.1071/en10088 ◽

2010 ◽

Vol 7 (6) ◽

pp. 537 ◽

Cited By ~ 3

Author(s):

Anne L. Soerensen ◽

Henrik Skov ◽

Matthew S. Johnson ◽

Marianne Glasius

Keyword(s):

Urban Areas ◽

Marine Boundary Layer ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Mercury Deposition ◽

Mercury Emissions ◽

Gaseous Elemental Mercury ◽

Gaseous Mercury ◽

Range Transport ◽

Aquatic Food

Environmental context Mercury is a neurotoxin that bioaccumulates in the aquatic food web. Atmospheric emissions from urban areas close to the coast could cause increased local mercury deposition to the ocean. Our study adds important new data to the current limited knowledge on atmospheric mercury emissions and dynamics in coastal urban areas. Abstract Approximately 50% of primary atmospheric mercury emissions are anthropogenic, resulting from e.g. emission hotspots in urban areas. Emissions from urban areas close to the coast are of interest because they could increase deposition loads to nearby coastal waters as well as contribute to long range transport of mercury. We present results from measurements of gaseous elemental mercury (GEM) and reactive gaseous mercury (RGM) in 15 coastal cities and their surrounding marine boundary layer (MBL). An increase of 15–90% in GEM concentration in coastal urban areas was observed compared with the remote MBL. Strong RGM enhancements were only found in two cities. In urban areas with statistically significant GEM/CO enhancement ratios, slopes between 0.0020 and 0.0087 ng m–3 ppb–1 were observed, which is consistent with other observations of anthropogenic enhancement. The emission ratios were used to estimate GEM emissions from the areas. A closer examination of data from Sydney (Australia), the coast of Chile, and Valparaiso region (Chile) in the southern hemisphere, is presented.

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A synthesis of atmospheric mercury depletion event chemistry linking atmosphere, snow and water

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-10837-2007 ◽

2007 ◽

Vol 7 (4) ◽

pp. 10837-10931 ◽

Cited By ~ 19

Author(s):

A. Steffen ◽

T. Douglas ◽

M. Amyot ◽

P. Ariya ◽

K. Aspmo ◽

...

Keyword(s):

Sea Ice ◽

Current Knowledge ◽

Kinetic Studies ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

The Arctic ◽

Polar Regions ◽

Environmental Media ◽

Gaseous Elemental Mercury ◽

History Of

Abstract. It was discovered in 1995 that, during the spring time, unexpectedly low concentrations of gaseous elemental mercury (GEM) occurred in the Arctic air. This was surprising for a pollutant known to have a long residence time in the atmosphere; however conditions appeared to exist in the Arctic that promoted this depletion of mercury (Hg). This phenomenon is termed atmospheric mercury depletion events (AMDEs) and its discovery has revolutionized our understanding of the cycling of Hg in Polar Regions while stimulating a significant amount of research to understand its impact to this fragile ecosystem. Shortly after the discovery was made in Canada, AMDEs were confirmed to occur throughout the Arctic, sub-Artic and Antarctic coasts. It is now known that, through a series of photochemically initiated reactions involving halogens, GEM is converted to a more reactive species and is subsequently associated to particles in the air and/or deposited to the polar environment. AMDEs are a means by which Hg is transferred from the atmosphere to the environment that was previously unknown. In this article we review the history of Hg in Polar Regions, the methods used to collect Hg in different environmental media, research results of the current understanding of AMDEs from field, laboratory and modeling work, how Hg cycles around the environment after AMDEs, gaps in our current knowledge and the future impacts that AMDEs may have on polar environments. The research presented has shown that while considerable improvements in methodology to measure Hg have been made the main limitation remains knowing the speciation of Hg in the various media. The processes that drive AMDEs and how they occur are discussed. As well, the roles that the snow pack, oceans, fresh water and the sea ice play in the cycling of Hg are presented. It has been found that deposition of Hg from AMDEs occurs at marine coasts and not far inland and that a fraction of the deposited Hg does not remain in the same form in the snow. Kinetic studies undertaken have demonstrated that bromine is the major oxidant depleting Hg in the atmosphere. Modeling results demonstrate that there is a significant deposition of Hg to Polar Regions as a result of AMDEs. Models have also shown that Hg is readily transported to the Arctic from source regions, at times during springtime when this environment is actively transforming Hg from the atmosphere to the snow and ice surfaces. The presence of significant amounts of methyl Hg in snow in the Arctic surrounding AMDEs is important because this species is the link between the environment and impacts to wildlife and humans. Further, much work on methylation and demethylation processes have occurred but are not yet fully understood. Recent changes in the climate and sea ice cover in Polar Regions are likely to have strong effects on the cycling of Hg in this environment; however more research is needed to understand Hg processes in order to formulate meaningful predictions of these changes. Mercury, Atmospheric mercury depletion events (AMDE), Polar, Arctic, Antarctic, Ice

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Measurement-based modeling of daytime and nighttime oxidation of atmospheric mercury

10.5194/acp-2017-39 ◽

2017 ◽

Cited By ~ 2

Author(s):

Maor Gabay ◽

Mordechai Peleg ◽

Erick Fredj ◽

Eran Tas

Keyword(s):

Lower Limit ◽

Rate Constant ◽

Field Measurements ◽

Elemental Mercury ◽

Chemical Oxidation ◽

Atmospheric Mercury ◽

Gaseous Elemental Mercury ◽

Measurement Results ◽

Kinetic Calculations ◽

First Time

Abstract. Accurate characterization of gaseous elemental mercury (GEM) chemical oxidation pathways and their kinetics is critically important for assessing the transfer of atmospheric mercury to bioaquatic systems. Recent comprehensive field measurements have suggested that the nitrate radical (NO3) plays a role in efficient nighttime oxidation of GEM, and that the role of the hydroxyl radical (OH) as a GEM oxidant has been underestimated. We used the CAABA/MECCA chemical box model and additional kinetic calculations to analyze these measurement results, in order to investigate the nighttime and daytime oxidation of GEM. We assumed a second-order reaction for the NO3 induced nighttime oxidation of GEM. Our analysis demonstrated that nighttime oxidation of GEM has to be included in the model to account for the measured variations in nighttime reactive gaseous mercury (RGM) concentration. A lower limit and best-fit rate constant for GEM nighttime oxidation are provided. To the best of our knowledge, this is the first time that a rate for nighttime oxidation of GEM has been determined based on field measurements. Our analysis further indicates that OH has a much more important role in GEM oxidation than commonly considered. A lower-limit rate constant for the OH–RGM reaction is provided.

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Atmospheric mercury deposition over the land surfaces and the associated uncertainties in observations and simulations: a critical review

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-15587-2019 ◽

2019 ◽

Vol 19 (24) ◽

pp. 15587-15608 ◽

Cited By ~ 4

Author(s):

Lei Zhang ◽

Peisheng Zhou ◽

Shuzhen Cao ◽

Yu Zhao

Keyword(s):

Dry Deposition ◽

Wet Deposition ◽

Quantitative Methods ◽

Experimental System ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Future Research ◽

Observation Data ◽

Mercury Deposition ◽

Land Surfaces

Abstract. One of the most important processes in the global mercury (Hg) biogeochemical cycling is the deposition of atmospheric Hg, including gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particulate-bound mercury (PBM), to the land surfaces. Results of wet, dry, and forest Hg deposition from global observation networks, individual monitoring studies, and observation-based simulations have been reviewed in this study. Uncertainties in the observation and simulation of global speciated atmospheric Hg deposition to the land surfaces have been systemically estimated based on assessment of commonly used observation methods, campaign results for comparison of different methods, model evaluation with observation data, and sensitivity analysis for model parameterization. The uncertainties of GOM and PBM dry deposition measurements come from the interference of unwanted Hg forms or incomplete capture of targeted Hg forms, while that of GEM dry deposition observation originates from the lack of a standardized experimental system and operating procedure. The large biases in the measurements of GOM and PBM concentrations and the high sensitivities of key parameters in resistance models lead to high uncertainties in GOM and PBM dry deposition simulation. Non-precipitation Hg wet deposition could play a crucial role in alpine and coastal regions, and its high uncertainties in both observation and simulation affect the overall uncertainties of Hg wet deposition. The overall uncertainties in the observation and simulation of the total global Hg deposition were estimated to be ± (25–50) % and ± (45–70) %, respectively, with the largest contributions from dry deposition. According to the results from uncertainty analysis, future research needs were recommended, among which a global Hg dry deposition network, unified methods for GOM and PBM dry deposition measurements, quantitative methods for GOM speciation, campaigns for comprehensive forest Hg behavior, and more efforts in long-term Hg deposition monitoring in Asia are the top priorities.

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Investigation of processes controlling GEM oxidation at mid-latitudinal marine, coastal, and inland sites

10.5194/acp-2015-829 ◽

2016 ◽

Author(s):

Z. Ye ◽

H. Mao ◽

C.-J. Lin ◽

S. Y. Kim

Keyword(s):

Marine Boundary Layer ◽

State Of The Art ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Chemical Mechanism ◽

Atmospheric Conditions ◽

Gaseous Elemental Mercury ◽

Mixing Ratios ◽

Marine Site ◽

Study Sites

Abstract. A box model incorporating a state-of-the-art chemical mechanism for atmospheric mercury (Hg) cycling was developed to investigate oxidation of gaseous elemental mercury (GEM) at three locations in the northeastern United States: Appledore Island (marine), Thompson Farm (coastal, rural), and Pack Monadnock (inland, rural, elevated). The chemical mechanism improved model's ability to simulate the formation of gaseous oxidized mercury (GOM) at the study sites. At the coastal and inland sites, GEM oxidation was predominated by O3 and OH, contributing 80–99 % of total GOM production during daytime. H2O2 initiated GEM oxidation was significant (~ 33 % of the total GOM) at the inland site during nighttime. In the marine boundary layer (MBL), Br and BrO were dominant GEM oxidants contributing ~ 70 % of the total GOM production during mid-day, while O3 dominated GEM oxidation (50–90 % of GOM production) over the remaining day. Following the production of HgBr from GEM + Br, HgBr was oxidized by BrO, HO2, OH, ClO, and IO to form Hg(II) brominated GOM species. However, under atmospheric conditions, the prevalent GEM oxidants in the MBL could be Br / BrO or O3 / OH depending on Br and BrO mixing ratios. Relative humidity and products of the CH3O2 + BrO reaction possibly affected significantly the mixing ratios of Br or BrO radicals and subsequently GOM formation. Gas-particle partitioning could be potentially important in the production of GOM as well as Br and BrO at the marine site.

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Evaluation of cation exchange membrane performance under exposure to high Hg<sup>0</sup> and HgBr<sub>2</sub> concentrations

Atmospheric Measurement Techniques ◽

10.5194/amt-12-1207-2019 ◽

2019 ◽

Vol 12 (2) ◽

pp. 1207-1217 ◽

Cited By ~ 7

Author(s):

Matthieu B. Miller ◽

Sarrah M. Dunham-Cheatham ◽

Mae Sexauer Gustin ◽

Grant C. Edwards

Keyword(s):

Cation Exchange ◽

High Efficiency ◽

Absolute Humidity ◽

Elemental Mercury ◽

Mercury Vapor ◽

Ambient Air ◽

Atmospheric Mercury ◽

Promising Alternative ◽

Gaseous Elemental Mercury ◽

High Concentrations

Abstract. Reactive mercury (RM), the sum of both gaseous oxidized Hg and particulate bound Hg, is an important component of the global atmospheric mercury cycle, but measurement currently depends on uncalibrated operationally defined methods with large uncertainty and demonstrated interferences and artifacts. Cation exchange membranes (CEMs) provide a promising alternative methodology for quantification of RM, but method validation and improvements are ongoing. For the CEM material to be reliable, uptake of gaseous elemental mercury (GEM) must be negligible under all conditions and RM compounds must be captured and retained with high efficiency. In this study, the performance of CEM material under exposure to high concentrations of GEM (1.43×106 to 1.85×106 pg m−3) and reactive gaseous mercury bromide (HgBr2 ∼5000 pg m−3) was explored using a custom-built mercury vapor permeation system. Quantification of total permeated Hg was measured via pyrolysis at 600 ∘C and detection using a Tekran® 2537A. Permeation tests were conducted over 24 to 72 h in clean laboratory air, with absolute humidity levels ranging from 0.1 to 10 g m−3 water vapor. GEM uptake by the CEM material averaged no more than 0.004 % of total exposure for all test conditions, which equates to a non-detectable GEM artifact for typical ambient air sample concentrations. Recovery of HgBr2 on CEM filters was on average 127 % compared to calculated total permeated HgBr2 based on the downstream Tekran® 2537A data. The low HgBr2 breakthrough on the downstream CEMs (< 1 %) suggests that the elevated recoveries are more likely related to suboptimal pyrolyzer conditions or inefficient collection on the Tekran® 2537A gold traps.

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A synthesis of atmospheric mercury depletion event chemistry in the atmosphere and snow

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-1445-2008 ◽

2008 ◽

Vol 8 (6) ◽

pp. 1445-1482 ◽

Cited By ~ 314

Author(s):

A. Steffen ◽

T. Douglas ◽

M. Amyot ◽

P. Ariya ◽

K. Aspmo ◽

...

Keyword(s):

Sea Ice ◽

Current Knowledge ◽

Kinetic Studies ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

The Arctic ◽

Polar Regions ◽

Environmental Media ◽

Gaseous Elemental Mercury ◽

Low Concentrations

Abstract. It was discovered in 1995 that, during the spring time, unexpectedly low concentrations of gaseous elemental mercury (GEM) occurred in the Arctic air. This was surprising for a pollutant known to have a long residence time in the atmosphere; however conditions appeared to exist in the Arctic that promoted this depletion of mercury (Hg). This phenomenon is termed atmospheric mercury depletion events (AMDEs) and its discovery has revolutionized our understanding of the cycling of Hg in Polar Regions while stimulating a significant amount of research to understand its impact to this fragile ecosystem. Shortly after the discovery was made in Canada, AMDEs were confirmed to occur throughout the Arctic, sub-Artic and Antarctic coasts. It is now known that, through a series of photochemically initiated reactions involving halogens, GEM is converted to a more reactive species and is subsequently associated to particles in the air and/or deposited to the polar environment. AMDEs are a means by which Hg is transferred from the atmosphere to the environment that was previously unknown. In this article we review Hg research taken place in Polar Regions pertaining to AMDEs, the methods used to collect Hg in different environmental media, research results of the current understanding of AMDEs from field, laboratory and modeling work, how Hg cycles around the environment after AMDEs, gaps in our current knowledge and the future impacts that AMDEs may have on polar environments. The research presented has shown that while considerable improvements in methodology to measure Hg have been made but the main limitation remains knowing the speciation of Hg in the various media. The processes that drive AMDEs and how they occur are discussed. As well, the role that the snow pack and the sea ice play in the cycling of Hg is presented. It has been found that deposition of Hg from AMDEs occurs at marine coasts and not far inland and that a fraction of the deposited Hg does not remain in the same form in the snow. Kinetic studies undertaken have demonstrated that bromine is the major oxidant depleting Hg in the atmosphere. Modeling results demonstrate that there is a significant deposition of Hg to Polar Regions as a result of AMDEs. Models have also shown that Hg is readily transported to the Arctic from source regions, at times during springtime when this environment is actively transforming Hg from the atmosphere to the snow and ice surfaces. The presence of significant amounts of methyl Hg in snow in the Arctic surrounding AMDEs is important because this species is the link between the environment and impacts to wildlife and humans. Further, much work on methylation and demethylation processes has occurred but these processes are not yet fully understood. Recent changes in the climate and sea ice cover in Polar Regions are likely to have strong effects on the cycling of Hg in this environment; however more research is needed to understand Hg processes in order to formulate meaningful predictions of these changes.

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