scholarly journals Characteristics of atmospheric mercury deposition and size-fractionated particulate mercury in urban Nanjing, China

2014 ◽  
Vol 14 (5) ◽  
pp. 2233-2244 ◽  
Author(s):  
J. Zhu ◽  
T. Wang ◽  
R. Talbot ◽  
H. Mao ◽  
X. Yang ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Fine Particles ◽  
Unit Area ◽  
Atmospheric Mercury ◽  
Anthropogenic Sources ◽  
Deposition Flux ◽  
Coarse Particles ◽  
Mercury Deposition ◽  
Particulate Mercury

Abstract. A comprehensive measurement study of mercury wet deposition and size-fractionated particulate mercury (HgP) concurrent with meteorological variables was conducted from June 2011 to February 2012 to evaluate the characteristics of mercury deposition and particulate mercury in urban Nanjing, China. The volume-weighted mean (VWM) concentration of mercury in rainwater was 52.9 ng L−1 with a range of 46.3–63.6 ng L−1. The wet deposition per unit area was averaged 56.5 μg m−2 over 9 months, which was lower than that in most Chinese cities, but much higher than annual deposition in urban North America and Japan. The wet deposition flux exhibited obvious seasonal variation strongly linked with the amount of precipitation. Wet deposition in summer contributed more than 80% to the total amount. A part of contribution to wet deposition of mercury from anthropogenic sources was evidenced by the association between wet deposition and sulfates, as well as nitrates in rainwater. The ions correlated most significantly with mercury were formate, calcium, and potassium, which suggested that natural sources including vegetation and resuspended soil should be considered as an important factor to affect the wet deposition of mercury in Nanjing. The average HgP concentration was 1.10 ± 0.57 ng m−3. A distinct seasonal distribution of HgP concentrations was found to be higher in winter as a result of an increase in the PM10 concentration. Overall, more than half of the HgP existed in the particle size range less than 2.1 μm. The highest concentration of HgP in coarse particles was observed in summer, while HgP in fine particles dominated in fall and winter. The size distribution of averaged mercury content in particulates was bimodal, with two peaks in the bins of < 0.7 μm and 4.7–5.8 μm. Dry deposition per unit area of HgP was estimated to be 47.2 μg m−2 using meteorological conditions and a size-resolved particle dry deposition model. This was 16.5% less than mercury wet deposition. Compared to HgP in fine particles, HgP in coarse particles contributed more to the total dry deposition due to higher deposition velocities. Negative correlation between precipitation and the HgP concentration reflected the effect of scavenging of HgP by precipitation.

scholarly journals Characteristics of atmospheric mercury deposition and size-fractionated particulate mercury in urban Nanjing, China

2013 ◽  
Vol 13 (11) ◽  
pp. 28309-28341 ◽  
Author(s):  
J. Zhu ◽  
T. Wang ◽  
R. Talbot ◽  
H. Mao ◽  
X. Yang ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Fine Particles ◽  
Unit Area ◽  
Atmospheric Mercury ◽  
Anthropogenic Sources ◽  
Deposition Flux ◽  
Coarse Particles ◽  
Mercury Deposition ◽  
Particulate Mercury

Abstract. A comprehensive measurement study of mercury wet deposition and size-fractioned particulate mercury (HgP) concurrent with meteorological variables was conducted from June 2011 to February 2012 to evaluate the characteristics of mercury deposition and particulate mercury in urban Nanjing, China. The volume weighted mean (VWM) concentration of mercury in rainwater was 52.9 ng L−1 with a range of 46.3–63.6 ng L−1. The wet deposition per unit area was averaged 56.5 μg m−2 over 9 months, which was lower than that in most Chinese cities, but much higher than annual deposition in urban America and Japan. The wet deposition flux exhibited obvious seasonal variation strongly linked with the amount of precipitation. Wet deposition in summer contributed more than 80% to the total amount. A part of contribution to wet deposition of mercury from anthropogenic sources was evidenced by the association between wet deposition and sulfates, and nitrates in rainwater. The ions correlated most significantly with mercury were formate, calcium and potassium, which suggested that natural sources including vegetation and resuspended soil should be considered as an important factor to affect the wet deposition of mercury in Nanjing. The average HgP concentration was 1.10 ± 0.57 ng m−3. A distinct seasonal distribution of HgP concentrations was found to be higher in winter as a result of an increase in the PM10 concentration. Overall, more than half of HgP existed in the particle size range less than 2.1 μm. The highest concentration of HgP in coarse particles was observed in summer while HgP in fine particles dominated in fall and winter. The size distribution of averaged mercury content in particulates was bimodal with two peaks in the bins of <0.7 μm and 4.7–5.8 μm. Dry deposition per unit area of HgP was estimated to be 47.2 μg m−2 using meteorological conditions and a size-resolved particle dry deposition model. This was 16.5% less than mercury wet deposition. Compared to HgP in fine particles, HgP in coarse particles contributed more to the total dry deposition due to higher deposition velocities. Negative correlation between precipitation and the HgP concentration reflected the effect of scavenging of HgP by precipitation.

scholarly journals Total atmospheric mercury deposition in forested areas in South Korea

2016 ◽  
Vol 16 (12) ◽  
pp. 7653-7662 ◽  
Author(s):  
Jin-Su Han ◽  
Yong-Seok Seo ◽  
Moon-Kyung Kim ◽  
Thomas M. Holsen ◽  
Seung-Muk Yi
Keyword(s):  
South Korea ◽  
Dry Deposition ◽  
Wet Deposition ◽  
Deciduous Forest ◽  
Atmospheric Mercury ◽  
Deposition Flux ◽  
Mercury Deposition ◽  
Temperate Deciduous Forest ◽  
Deposition Fluxes ◽  
Forested Areas

Abstract. In this study, mercury (Hg) was sampled weekly in dry and wet deposition and throughfall and monthly in litterfall, and as it was volatilized from soil from August 2008 to February 2010 to identify the factors influencing the amount of atmospheric Hg deposited to forested areas in a temperate deciduous forest in South Korea. For this location there was no significant correlation between the estimated monthly dry deposition flux (litterfall + throughfall – wet deposition) (6.7 µg m−2 yr−1) and directly measured dry deposition (9.9 µg m−2 yr−1) likely due primarily to Hg losses from the litterfall collector. Dry deposition fluxes in cold seasons (fall and winter) were lower than in warmer seasons (spring and summer). The volume-weighted mean (VWM) Hg concentrations in both precipitation and throughfall were highest in winter, likely due to increased scavenging by snow events. Since South Korea experiences abundant rainfall in summer, VWM Hg concentrations in summer were lower than in other seasons. Litterfall fluxes were highest in the late fall to early winter, when leaves were dropped from the trees (September to November). The cumulative annual Hg emission flux from soil was 6.8 µg m−2 yr−1. Based on these data, the yearly deposition fluxes of Hg calculated using two input approaches (wet deposition + dry deposition or throughfall + litterfall) were 6.8 and 3.6 µg m−2 yr−1, respectively. This is the first reported study which measured the amount of atmospheric Hg deposited to forested areas in South Korea, and thus our results provide useful information to compare against data related to Hg fate and transport in this part of the world.

scholarly journals Model analyses of atmospheric mercury: present air quality and effects of transpacific transport on the United States

2013 ◽  
Vol 13 (4) ◽  
pp. 9849-9893 ◽  
Author(s):  
H. Lei ◽  
X.-Z. Liang ◽  
D. J. Wuebbles ◽  
Z. Tao
Keyword(s):  
United States ◽  
Air Quality ◽  
Wet Deposition ◽  
Total Mercury ◽  
The United States ◽  
Atmospheric Mercury ◽  
Anthropogenic Sources ◽  
Mercury Deposition ◽  
Transpacific Transport ◽  
Mercury Cycle

Abstract. Atmospheric mercury is a toxic air and water pollutant that is of significant concern because of its effects on human health and ecosystems. A mechanistic representation of the atmospheric mercury cycle is developed for the state-of-the-art global climate-chemistry model, CAM-Chem (Community Atmospheric Model with Chemistry). The model simulates the emission, transport, transformation and deposition of atmospheric mercury (Hg) in three forms: elemental mercury (Hg(0)), reactive mercury (Hg(II)), and particulate mercury (PHg). Emissions of mercury include those from human, land, ocean, biomass burning and volcano related sources. Land emissions are calculated based on surface solar radiation flux and skin temperature. A simplified air–sea mercury exchange scheme is used to calculate emissions from the oceans. The chemistry mechanism includes the oxidation of Hg(0) in gaseous phase by ozone with temperature dependence, OH, H2O2 and chlorine. Aqueous chemistry includes both oxidation and reduction of Hg(0). Transport and deposition of mercury species are calculated through adapting the original formulations in CAM-Chem. The CAM-Chem model with mercury is driven by present meteorology to simulate the present mercury air quality during the 1999–2001 periods. The resulting surface concentrations of total gaseous mercury (TGM) are then compared with the observations from worldwide sites. Simulated wet depositions of mercury over the continental United States are compared to the observations from 26 Mercury Deposition Network stations to test the wet deposition simulations. The evaluations of gaseous concentrations and wet deposition confirm a strong capability for the CAM-Chem mercury mechanism to simulate the atmospheric mercury cycle. The results also indicate that mercury pollution in East Asia and Southern Africa is very significant with TGM concentrations above 3.0 ng m−3. The comparison to wet deposition indicates that wet deposition patterns of mercury are more affected by the spatial variability of precipitation. The sensitivity experiments show that 22% of total mercury deposition and 25% of TGM concentrations in the United States are resulted from domestic anthropogenic sources, but only 9% of total mercury deposition and 7% of TGM concentrations are contributed by transpacific transport. However, the contributions of domestic and transpacific sources on the western United States levels of mercury are of comparable magnitude.

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

2019 ◽  
Vol 19 (24) ◽  
pp. 15587-15608 ◽  
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.

Dispersion and dry and wet deposition of PAHs in an atmospheric environment

2006 ◽  
Vol 53 (2) ◽  
pp. 215-224 ◽  
Author(s):  
N. Ozaki ◽  
K. Nitta ◽  
T. Fukushima
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Fine Particles ◽  
Atmospheric Environment ◽  
Coarse Particles ◽  
Atmospheric Concentration ◽  
Dry And Wet Deposition ◽  
Total Pahs ◽  
Polycyclic Aromatic ◽  
Rainy Days

The atmospheric concentration and dry and wet deposition were measured for particulate matter (PM) and polycyclic aromatic hydrocarbons (PAHs) from August to December in Higashi-Hiroshima City, Japan. PM concentration of fine particles (0.6–7 μm) was 5.7–75.1 μg m−3, and coarse particles (&gt;7 μm) was 2.2–22.3 μg m−3. Total PAHs concentration of fine particles was 0.14–16.3 ng m−3, and coarse particles was 0.01–0.77 ng m−3. Their concentration increased on non-rainy days and decreased rapidly on rainy days. For seasonal fluctuations of PAHs, their concentrations decreased from summer to winter, and the rate of decrease was more distinct for fine particles. For total (dry+wet) depositions, the PM flux was 1.9–11.2 mg m−2 d−1, and the total PAHs flux was 1.9–97.2 ng m−3 d−1. From these measurements, the yearly total loading of PAHs was estimated for the particle phase. Total loading was 28 μg m−2 y−1 for the dry deposition and 52 mg m−2 y−1 for the wet deposition. The loading of the wet deposition was comparable to those of the dry deposition for all ring numbers.

scholarly journals Global deposition of speciated atmospheric mercury to terrestrial surfaces: an overview

2019 ◽  
Author(s):  
Lei Zhang ◽  
Peisheng Zhou ◽  
Shuzhen Cao ◽  
Yu Zhao
Keyword(s):  
Dry Deposition ◽  
Urban Areas ◽  
Wet Deposition ◽  
Current Knowledge ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Future Research ◽  
Observation System ◽  
Mercury Deposition ◽  
Gaseous Elemental Mercury

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.

scholarly journals Total Atmospheric Mercury Deposition in Forest Areas in Korea

2016 ◽  
Author(s):  
Jin-Su Han ◽  
Yong-Seok Seo ◽  
Moon-Kyung Kim ◽  
Thomas M. Holsen ◽  
Seung-Muk Yi
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Deciduous Forest ◽  
Atmospheric Mercury ◽  
Litter Production ◽  
Mercury Deposition ◽  
Temperate Deciduous Forest ◽  
Deposition Fluxes ◽  
Mercury Volatilization ◽  
High Precipitation

Abstract. Atmospheric mercury dry and wet deposition, mercury in throughfall and litterfall, and mercury volatilization from soil were measured during August 2008 to February 2010 in a temperate deciduous forest in Korea. The yearly estimated mercury budget was calculated using two input approaches. For this location the annual mercury accumulation was estimated to be 6.8 μg m-2 yr-1 or 3.9 μg m-2 yr-1 depending on the approach used. Cumulative wet and throughfall fluxes were 4.3 and 6.7 μg m-2 yr-1, respectively. The annual litterfall flux was 4.6 μg m-2 yr-1 and was highest from October to December due to the increased litter production during that period. The annual Hg emission flux from soil was 6.8 μg m-2 yr-1. The overall ratio of wet deposition, throughfall, and litterfall was 1 : 1.6 : 1.1. Cumulative dry deposition fluxes of gaseous oxidized mercury (GOM) were highest in spring 2009 (10.0 ± 2.0 μg m-2 yr-1), followed by summer 2009 (5.8 ± 4.2μg m-2 yr-1), winter 2008 (5.1 ± 5.0 μg m-2 yr-1), winter 2009 (4.6 ± 5.7 μg m-2 yr-1), fall 2008 (1.9 ± 1.0 μg m-2 yr-1) and fall 2009 (1.2 ± 1.4 μg m-2 yr-1) while dry deposition fluxes for particulate bound mercury (PBM) were highest in summer 2009 (9.6 ± 9.0 μg m-2 yr-1), followed by winter 2009 (5.3 ± 5.9 μg m-2 yr-1), winter 2008 (3.8 ± 2.0 μg m-2 yr-1), spring 2009 (3.3 ± 2.6 μg m-2 yr-1), fall 2008 (3.0 ± 1.7 μg m-2 yr-1) and fall 2009 (1.2 ± 0.4 μg m-2 yr-1). The VWM TM concentration in throughfall (14.4 ± 7.1 ng L-1) was about two times higher than that in wet deposition (5.9 ± 3.8 ng L-1). Wet deposition and throughfall fluxes were higher in summer than those in other seasons possibly due to a high precipitation depth.

scholarly journals Surface deposition of oxidized mercury dominated by production in the upper and middle troposphere

2017 ◽  
Author(s):  
Viral Shah ◽  
Lyatt Jaeglé
Keyword(s):  
Boundary Layer ◽  
Dry Deposition ◽  
Wet Deposition ◽  
Lower Troposphere ◽  
The United States ◽  
Atmospheric Mercury ◽  
Deposition Flux ◽  
Surface Deposition ◽  
Middle Troposphere ◽  
Wet Deposition Flux

Abstract. Oxidized mercury (Hg(II)) is chemically produced in the atmosphere by oxidation of elemental mercury and is directly emitted by anthropogenic activities. We use the GEOS-Chem global chemical transport model, with gaseous oxidation driven by Br atoms, to quantify how surface deposition of Hg(II) is influenced by Hg(II) production at different atmospheric heights. We tag Hg(II) chemically produced in the lower (surface–750 hPa), middle (750–400 hPa) and upper troposphere (400 hPa–tropopause), in the stratosphere, as well as directly emitted Hg(II). A two-year simulation (2013–2014) reproduces the spatial distribution and seasonal cycle of Hg(II) surface concentrations and Hg wet deposition observed at the Atmospheric Mercury Network (AMNet) and the Mercury Deposition Network (MDN) stations over the United States to within 21 %, but displays a 46 % underestimate of wet deposition observed at the European Monitoring and Evaluation Programme (EMEP) stations. We find that Hg(II) produced in the upper and middle troposphere constitutes 91 % of the tropospheric mass of Hg(II) and 91 % of the annual Hg(II) wet deposition flux. This large global influence from the upper and middle troposphere is the result of strong chemical production coupled with a long lifetime of Hg(II) in these regions. Annually, 77–84 % of surface level Hg(II) over the western U.S., South America, South Africa, and Australia is produced in the upper and middle troposphere, whereas 26–66 % of surface Hg(II) over the eastern U.S., Europe, East Asia, and South Asia is directly emitted. Over the oceans, 72 % of surface Hg(II) is produced in the lower troposphere, because of higher Br concentrations in the marine boundary layer. The global contribution of the upper and middle troposphere to the Hg(II) dry deposition flux is 52 %. It is lower compared to the contribution to wet deposition because dry deposition of Hg(II) produced aloft requires its entrainment into the boundary layer, while rain can scavenge Hg(II) from higher altitudes more readily. We find that 55 % of the spatial variation of Hg wet deposition flux observed at the MDN sites is explained by the combined variation of precipitation and Hg(II) produced in the upper and middle troposphere. Our simulation points to a large role of Hg(II) present in the dry subtropical subsidence regions, which account for 74 % of Hg(II) at 500 hPa over the continental U.S., and more than 60 % of the surface Hg(II) over high-altitude areas of the western U.S. During the Nitrogen, Oxidants, Mercury, and Aerosol Distributions, Sources, and Sinks (NOMADSS) aircraft campaign, the contribution of these dry regions was found to be 75 % when measured Hg(II) exceeded 250 pg m−3. Our results highlight the importance of the upper and middle troposphere as key regions for Hg(II) production and of the subtropical anticyclones as the primary conduits for the production and export of Hg(II) to the global atmosphere.

scholarly journals Atmospheric particle dry deposition of major ions to the South Atlantic coastal area observed at Baía de Todos os Santos, Brazil

2014 ◽  
Vol 86 (1) ◽  
pp. 37-55 ◽  
Author(s):  
STELYUS L. MKOMA ◽  
GISELE O. DA ROCHA ◽  
JOSÉ S.S. DOMINGOS ◽  
JOÃO V.S. SANTOS ◽  
MANUELA P. CARDOSO ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Urban Areas ◽  
Fine Particles ◽  
Major Ions ◽  
Salt Spray ◽  
Fine Fraction ◽  
Sea Salt ◽  
Water Soluble ◽  
Anthropogenic Sources ◽  
Coarse Particles

The coastal atmosphere adjacent to large urban areas can be strongly affected by the emission of air pollutants, among them, major ions species. In this study, the chemical composition and sources of carboxylates and other water-soluble ions in fine and coarse aerosols as well as estimates of particle dry deposition fluxes were studied at a tropical coastal site affected by an urban environment. The mean concentrations of the total carboxylates were 78 ng m–3 in fine fraction and 81 ng m–3 in coarse fraction of particulate matter (PM). The corresponding values for the total inorganic ions were 2143 ng m–3 and 4880 ng m–3 respectively. Main sources for fine particles were: (i) photochemical formation of carboxylic acids in vapor phase and a posterior gas-to-particle conversion onto sea salt particles; (ii) emissions from anthropic sources with long range transportation processes; and (iii) the interchanging of volatile species among atmospheric phases. In turn, for coarse particles, the predominant sources were: (i) gas-phase species and ab/adsorbed onto pre-existing particles afterwards; (ii) primary emission of coarse particles from anthropogenic sources; and (iii) sea salt spray and/or soil resuspension. Finally, particle dry deposition was a very important mechanism representing air-to-sea fluxes of major species.

scholarly journals Model analyses of atmospheric mercury: present air quality and effects of transpacific transport on the United States

2013 ◽  
Vol 13 (21) ◽  
pp. 10807-10825 ◽  
Author(s):  
H. Lei ◽  
X.-Z. Liang ◽  
D. J. Wuebbles ◽  
Z. Tao
Keyword(s):  
United States ◽  
Air Quality ◽  
Wet Deposition ◽  
Total Mercury ◽  
The United States ◽  
Atmospheric Mercury ◽  
Anthropogenic Sources ◽  
Mercury Deposition ◽  
Transpacific Transport ◽  
Mercury Cycle

Abstract. Atmospheric mercury is a toxic air and water pollutant that is of significant concern because of its effects on human health and ecosystems. A mechanistic representation of the atmospheric mercury cycle is developed for the state-of-the-art global climate-chemistry model, CAM-Chem (Community Atmospheric Model with Chemistry). The model simulates the emission, transport, transformation and deposition of atmospheric mercury (Hg) in three forms: elemental mercury (Hg(0)), reactive mercury (Hg(II)), and particulate mercury (PHg). Emissions of mercury include those from human, land, ocean, biomass burning and volcano related sources. Land emissions are calculated based on surface solar radiation flux and skin temperature. A simplified air–sea mercury exchange scheme is used to calculate emissions from the oceans. The chemistry mechanism includes the oxidation of Hg(0) in gaseous phase by ozone with temperature dependence, OH, H2O2 and chlorine. Aqueous chemistry includes both oxidation and reduction of Hg(0). Transport and deposition of mercury species are calculated through adapting the original formulations in CAM-Chem. The CAM-Chem model with mercury is driven by present meteorology to simulate the present mercury air quality during the 1999–2001 period. The resulting surface concentrations of total gaseous mercury (TGM) are then compared with the observations from worldwide sites. Simulated wet depositions of mercury over the continental United States are compared to the observations from 26 Mercury Deposition Network stations to test the wet deposition simulations. The evaluations of gaseous concentrations and wet deposition confirm a strong capability for the CAM-Chem mercury mechanism to simulate the atmospheric mercury cycle. The general reproduction of global TGM concentrations and the overestimation on South Africa indicate that model simulations of TGM are seriously affected by emissions. The comparison to wet deposition indicates that wet deposition patterns of mercury are more affected by the spatial variability of precipitation. The sensitivity experiments show that 22% of total mercury deposition and 25% of TGM concentrations in the United States result from domestic anthropogenic sources, but only 9% of total mercury deposition and 7% of TGM concentrations are contributed by transpacific transport. However, the contributions of domestic and transpacific sources on the western United States levels of mercury are of comparable magnitude.

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