scholarly journals Development and Application of a Multipollutant Model for Atmospheric Mercury Deposition

2007 ◽  
Vol 46 (9) ◽  
pp. 1341-1353 ◽  
Author(s):  
Krish Vijayaraghavan ◽  
Christian Seigneur ◽  
Prakash Karamchandani ◽  
Shu-Yun Chen
Keyword(s):  
Atmospheric Deposition ◽  
Wet Deposition ◽  
Model Performance ◽  
The United States ◽  
Comprehensive Treatment ◽  
Precipitation Data ◽  
Mercury Deposition ◽  
Upper Midwest ◽  
Deposition Fluxes ◽  
Normalized Error

Abstract A multipollutant model, the Community Multiscale Air Quality model paired with the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (CMAQ-MADRID), is extended to include a comprehensive treatment of mercury processes and is applied to the simulation of the atmospheric deposition of sulfate and mercury over the United States during 1996. Model performance is evaluated first by comparison with annual sulfate wet deposition data from the National Atmospheric Deposition Program’s National Trends Network; the coefficient of determination r 2 is 0.77, and the model normalized error and bias are 53% and −8%, respectively. When actual precipitation data are used to scale the deposition fluxes, r 2 improves to 0.91 and the error and bias change to 42% and −41%, respectively. The scaled results underscore a tendency of the model to underestimate sulfate wet deposition. Model performance for mercury wet deposition is then evaluated by comparison with data from the Mercury Deposition Network. For annual mercury wet deposition, r 2 is 0.28 and the normalized error and bias are 81% and 73%, respectively, when the modeled precipitation data are used. Model performance improves when actual precipitation data are used to scale deposition fluxes: r 2 increases to 0.41 and the error and bias decrease to 40% and 29%, respectively. The model reproduces the spatial pattern of sulfate wet deposition adequately with an increasing gradient from the upper Midwest to the Northeast, that is, from upwind to downwind of large sulfur dioxide sources in the Ohio River Valley. However, the model tends to overestimate mercury wet deposition in the Northeast downwind of these sources that also emit significant amounts of mercury. This “Pennsylvania anomaly” may be due to a partial misrepresentation of the mercury reduction–oxidation cycle, uncertainties in the dry deposition of divalent gaseous mercury HgII, incorrect speciation of mercury emissions, and/or uncharacterized emissions in the upper Midwest.

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 Multi-model mean nitrogen and sulfur deposition from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP): evaluation historical and projected changes

2013 ◽  
Vol 13 (3) ◽  
pp. 6247-6294 ◽  
Author(s):  
J.-F. Lamarque ◽  
F. Dentener ◽  
J. McConnell ◽  
C.-U. Ro ◽  
M. Shaw ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Wet Deposition ◽  
Climate Model ◽  
Ice Core ◽  
The United States ◽  
Time Slice ◽  
Model Intercomparison ◽  
Deposition Fluxes ◽  
Continental Scale ◽  
Intercomparison Project

Abstract. We present multi-model global datasets of nitrogen and sulfate deposition covering time periods from 1850 to 2100, calculated within the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The computed deposition fluxes are compared to surface wet deposition and ice-core measurements. We use a new dataset of wet deposition for 2000–2002 based on critical assessment of the quality of existing regional network data. We show that for present-day (year 2000 ACCMIP time-slice), the ACCMIP results perform similarly to previously published multi-model assessments. For this time slice, we find a multi-model mean deposition of 50 Tg(N) yr−1 from nitrogen oxide emissions, 60 Tg(N) yr−1 from ammonia emissions, and 83 Tg(S) yr−1 from sulfur emissions. The analysis of changes between 1980 and 2000 indicates significant differences between model and measurements over the United States but less so over Europe. This difference points towards misrepresentation of 1980 NH3 emissions over North America. Based on ice-core records, the 1850 deposition fluxes agree well with Greenland ice cores but the change between 1850 and 2000 seems to be overestimated in the Northern Hemisphere for both nitrogen and sulfur species. Using the Representative Concentration Pathways to define the projected climate and atmospheric chemistry related emissions and concentrations, we find large regional nitrogen deposition increases in 2100 in Latin America, Africa and parts of Asia under some of the scenarios considered. Increases in South Asia are especially large, and are seen in all scenarios, with 2100 values more than double 2000 in some scenarios and reaching > 1300 mg(N) m−2 yr−1 averaged over regional to continental scale regions in RCP 2.6 and 8.5, ~30–50 % larger than the values in any region currently (2000). The new ACCMIP deposition dataset provides novel, consistent and evaluated global gridded deposition fields for use in a wide range of climate and ecological studies.

scholarly journals Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition

2012 ◽  
Vol 12 (1) ◽  
pp. 591-603 ◽  
Author(s):  
H. M. Amos ◽  
D. J. Jacob ◽  
C. D. Holmes ◽  
J. A. Fisher ◽  
Q. Wang ◽  
...  
Keyword(s):  
Gas Phase ◽  
Wet Deposition ◽  
Model Comparison ◽  
Fine Particulate Matter ◽  
Empirical Relationship ◽  
Mercury Deposition ◽  
Deposition Fluxes ◽  
The North ◽  
The Us ◽  
Snow Model

Abstract. Atmospheric deposition of Hg(II) represents a major input of mercury to surface environments. The phase of Hg(II) (gas or particle) has important implications for deposition. We use long-term observations of reactive gaseous mercury (RGM, the gaseous component of Hg(II)), particle-bound mercury (PBM, the particulate component of Hg(II)), fine particulate matter (PM2.5), and temperature (T) at five sites in North America to derive an empirical gas-particle partitioning relationship log10(K−1) = (10±1)–(2500±300)/T where K = (PBM/PM2.5)/RGM with PBM and RGM in common mixing ratio units, PM2.5 in μg m−3, and T in K. This relationship is within the range of previous work but is based on far more extensive data from multiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition Hg(II) between the gas and particle phases. The resulting gas-phase fraction of Hg(II) ranges from over 90 % in warm air with little aerosol to less than 10 % in cold air with high aerosol. Hg deposition to high latitudes increases because of more efficient scavenging of particulate Hg(II) by precipitating snow. Model comparison to Hg observations at the North American surface sites suggests that subsidence from the free troposphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associated with high aerosol loads. Simulation of RGM and PBM at these sites is improved by including fast in-plume reduction of Hg(II) emitted from coal combustion and by assuming that anthropogenic particulate Hg(p) behaves as semi-volatile Hg(II) rather than as a refractory particulate component. We improve the simulation of Hg wet deposition fluxes in the US relative to a previous version of GEOS-Chem; this largely reflects independent improvement of the washout algorithm. The observed wintertime minimum in wet deposition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).

scholarly journals Long-Term Trends in Regional Wet Mercury Deposition and Lacustrine Mercury Concentrations in Four Lakes in Voyageurs National Park

2021 ◽  
Vol 11 (4) ◽  
pp. 1879
Author(s):  
Mark E. Brigham ◽  
David D. VanderMeulen ◽  
Collin A. Eagles-Smith ◽  
David P. Krabbenhoft ◽  
Ryan P. Maki ◽  
...  
Keyword(s):  
Atmospheric Deposition ◽  
National Park ◽  
Total Mercury ◽  
The United States ◽  
Multimedia Data ◽  
Data Sets ◽  
Mercury Deposition ◽  
Continental Scale ◽  
Voyageurs National Park

Although anthropogenic mercury (Hg) releases to the environment have been substantially lowered in the United States and Canada since 1990, concerns remain for contamination in fish from remote lakes and rivers where atmospheric deposition is the predominant source of mercury. How have aquatic ecosystems responded? We report on one of the longest known multimedia data sets for mercury in atmospheric deposition: aqueous total mercury (THgaq), methylmercury (MeHgaq), and sulfate from epilimnetic lake-water samples from four lakes in Voyageurs National Park (VNP) in northern Minnesota; and total mercury (THg) in aquatic biota from the same lakes from 2001–2018. Wet Hg deposition at two regional Mercury Deposition Network sites (Fernberg and Marcell, Minnesota) decreased by an average of 22 percent from 1998–2018; much of the decreases occurred prior to 2009, with relatively flat trends since 2009. In the four VNP lakes, epilimnetic MeHgaq concentrations declined by an average of 44 percent and THgaq by an average of 27 percent. For the three lakes with long-term biomonitoring, temporal patterns in biotic THg concentrations were similar to patterns in MeHgaq concentrations; however, biotic THg concentrations declined significantly in only one lake. Epilimnetic MeHgaq may be responding both to a decline in atmospheric Hg deposition as well as a decline in sulfate deposition, which is an important driver of mercury methylation in the environment. Results from this case study suggest that regional- to continental-scale decreases in both mercury and sulfate emissions have benefitted aquatic resources, even in the face of global increases in mercury emissions.

scholarly journals Atmospheric wet and litterfall mercury deposition at urban and rural sites in China

2016 ◽  
Vol 16 (18) ◽  
pp. 11547-11562 ◽  
Author(s):  
Xuewu Fu ◽  
Xu Yang ◽  
Xiaofang Lang ◽  
Jun Zhou ◽  
Hui Zhang ◽  
...  
Keyword(s):  
Wet Deposition ◽  
Arid Zone ◽  
Influencing Factor ◽  
Urban Site ◽  
Cloud Base ◽  
Mercury Deposition ◽  
Subtropical Zone ◽  
Deposition Fluxes ◽  
Precipitation Depth ◽  
Rural Sites

Abstract. Mercury (Hg) concentrations and deposition fluxes in precipitation and litterfall were measured at multiple sites (six rural sites and an urban site) across a broad geographic area in China. The annual deposition fluxes of Hg in precipitation at rural sites and an urban site were 2.0 to 7.2 and 12.6 ± 6.5 µg m−2 yr−1, respectively. Wet deposition fluxes of Hg at rural sites showed a clear regional difference with elevated deposition fluxes in the subtropical zone, followed by the temporal zone and arid/semi-arid zone. Precipitation depth is the primary influencing factor causing the variation of wet deposition. Hg fluxes through litterfall ranged from 22.8 to 62.8 µg m−2 yr−1, higher than the wet deposition fluxes by a factor of 3.9 to 8.7 and representing approximately 75 % of the total Hg deposition at the forest sites in China. This suggests that uptake of atmospheric Hg by foliage is the dominant pathway to remove atmospheric Hg in forest ecosystems in China. Wet deposition fluxes of Hg at rural sites of China were generally lower compared to those in North America and Europe, possibly due to a combination of lower precipitation depth, lower GOM concentrations in the troposphere and the generally lower cloud base heights at most sites that wash out a smaller amount of GOM and PBM during precipitation events.

scholarly journals Gas-particle partitioning of atmospheric Hg(II) and its effect on global mercury deposition

2011 ◽  
Vol 11 (10) ◽  
pp. 29441-29477 ◽  
Author(s):  
H. M. Amos ◽  
D. J. Jacob ◽  
C. D. Holmes ◽  
J. A. Fisher ◽  
Q. Wang ◽  
...  
Keyword(s):  
Gas Phase ◽  
Wet Deposition ◽  
Model Comparison ◽  
Fine Particulate Matter ◽  
Empirical Relationship ◽  
Mercury Deposition ◽  
Deposition Fluxes ◽  
The Us ◽  
Snow Model

Abstract. Atmospheric deposition represents a major input of mercury to surface environments. The phase of mercury (gas or particle) has important implications for its removal from the atmosphere. We use long-term observations of reactive gaseous mercury (RGM), particle-bound mercury (PBM), fine particulate matter (PM2.5), and temperature at five sites in North America to derive an empirical gas-particle partitioning relationship log10(K-1) = (10 ± 1) − (2500 ± 300)/T where K = (PBM/PM2.5)/RGM with PBM and RGM in common mixing ratio units, PM2.5 in μg m−3, and T in Kelvin. This relationship is in the range of previous work but is based on far more extensive data from multiple sites. We implement this empirical relationship in the GEOS-Chem global 3-D Hg model to partition divalent mercury (Hg(II)). The resulting gas-phase fraction of Hg(II) ranges from over 90% in warm air with little aerosol to less than 10% in cold air with high aerosol. Hg deposition to high latitudes increases because of more efficient scavenging of particulate Hg(II) by snow. Model comparison to Hg observations at surface sites suggests that subsidence from the free troposphere (warm air, low aerosol) is a major factor driving the seasonality of RGM, while elevated PBM is mostly associated with high aerosol loads. This and other model updates, including the correction of an outstanding algorithm error, to wet deposition improve the simulation of Hg wet deposition fluxes in the US relative to the previous version of the model. The observed wintertime minimum in wet deposition fluxes is attributed to inefficient snow scavenging of gas-phase Hg(II).

scholarly journals Estimating chemical composition of atmospheric deposition fluxes from mineral insoluble particles deposition collected in the Western Mediterranean region

2017 ◽  
Author(s):  
Yinghe Fu ◽  
Karine Desboeufs ◽  
Julie Vincent ◽  
Elisabeth Bon Nguyen ◽  
Benoit Laurent ◽  
...  
Keyword(s):  
Trace Metals ◽  
Chemical Analysis ◽  
Atmospheric Deposition ◽  
Wet Deposition ◽  
Mediterranean Basin ◽  
Mineral Dust ◽  
Western Mediterranean ◽  
Dust Deposition ◽  
Deposition Fluxes ◽  
Western Mediterranean Basin

Abstract. In order to measure the mass flux of atmospheric insoluble deposition and to constrain regional models dust simulation, a network of automatic deposition collectors (CARAGA) has been installed throughout the western Mediterranean basin. Weekly samples of the insoluble fraction of total atmospheric deposition were collected concurrently on filters at 5 sites including 4 on western Mediterranean islands (Frioul and Corsica, France, Mallorca, Spain, and Lampedusa, Italy), and 1 in the southern French Alps (Le Casset), and a weighing and ignition protocol was applied in order to quantify their mineral fraction. Atmospheric deposition is both a strong source of nutrients and metals for marine ecosystems in this area. However, there is little data on trace metal deposition in the literature since their deposition measurement is difficult to perform. In order to obtain more information from CARAGA atmospheric deposition samples, this study aimed at testing their relevance to estimate elemental fluxes in addition to total fluxes. The elemental chemical analysis of ashed CARAGA filter samples was based on an acid digestion and an elemental analysis by inductively coupled plasma atomic emission spectroscopy (ICP-AES) and mass spectrometry (MS) in a clean room. The sampling and analytical protocols were tested to determine the elemental composition for mineral dust tracers (Al, Ca, K, Mg, and Ti), nutrients (P and Fe), and trace metals (Cd, Co, Cr, Cu, Mn, Ni, V and Zn) from simulated wet deposition of dust analogues and traffic soot. The relative mass loss by dissolution in wet deposition was lower than 1 % for Al and Fe, and reached 13 % for P due to its larger solubility in water. For trace metals, this loss represented less than 3 % of the total mass concentration, except for Zn, Cu and Mn for which it could reach 10 %, especially in traffic soot. The chemical contamination during analysis was negligible for all the elements except for Cd which is in very low concentration in dust. Tests allowed us to conclude that the CARAGA samples could be used to estimate contents of nutrients and trace metals in the limits of loss by dissolution. Chemical characterization of CARAGA deposition samples corresponding to the most intense dust deposition events recorded between 2011 and 2013 has been performed and showed elemental mass ratios consistent with the ones found in the literature for Saharan dust. However, the chemical analysis of CARAGA samples revealed the presence of some anthropogenic signatures, as for instance high Zn concentrations in some samples in Lampedusa, and also pointed out that mineral dust can be mixed with anthropogenic compounds in the deposition samples collected on the Frioul Island. Results showed that the chemical analysis of CARAGA ashed samples can be used to trace back origins of elemental deposition. The elemental atmospheric fluxes estimated from these chemical analyses of samples from the CARAGA network of weekly deposition monitoring constitute the first assessment of mass deposition fluxes of trace metals and P during intense dust deposition events at the scale of the western Mediterranean basin.

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 Multi-model mean nitrogen and sulfur deposition from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP): evaluation of historical and projected future changes

2013 ◽  
Vol 13 (16) ◽  
pp. 7997-8018 ◽  
Author(s):  
J.-F. Lamarque ◽  
F. Dentener ◽  
J. McConnell ◽  
C.-U. Ro ◽  
M. Shaw ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Wet Deposition ◽  
Climate Model ◽  
Ice Core ◽  
The United States ◽  
Time Slice ◽  
Sulfur Deposition ◽  
Model Intercomparison ◽  
Deposition Fluxes ◽  
Intercomparison Project

Abstract. We present multi-model global datasets of nitrogen and sulfate deposition covering time periods from 1850 to 2100, calculated within the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). The computed deposition fluxes are compared to surface wet deposition and ice core measurements. We use a new dataset of wet deposition for 2000–2002 based on critical assessment of the quality of existing regional network data. We show that for present day (year 2000 ACCMIP time slice), the ACCMIP results perform similarly to previously published multi-model assessments. For this time slice, we find a multi-model mean deposition of approximately 50 Tg(N) yr−1 from nitrogen oxide emissions, 60 Tg(N) yr−1 from ammonia emissions, and 83 Tg(S) yr−1 from sulfur emissions. The analysis of changes between 1980 and 2000 indicates significant differences between model and measurements over the United States but less so over Europe. This difference points towards a potential misrepresentation of 1980 NH3 emissions over North America. Based on ice core records, the 1850 deposition fluxes agree well with Greenland ice cores, but the change between 1850 and 2000 seems to be overestimated in the Northern Hemisphere for both nitrogen and sulfur species. Using the Representative Concentration Pathways (RCPs) to define the projected climate and atmospheric chemistry related emissions and concentrations, we find large regional nitrogen deposition increases in 2100 in Latin America, Africa and parts of Asia under some of the scenarios considered. Increases in South Asia are especially large, and are seen in all scenarios, with 2100 values more than double their 2000 counterpart in some scenarios and reaching > 1300 mg(N) m−2 yr−1 averaged over regional to continental-scale regions in RCP 2.6 and 8.5, ~ 30–50% larger than the values in any region currently (circa 2000). However, sulfur deposition rates in 2100 are in all regions lower than in 2000 in all the RCPs. The new ACCMIP multi-model deposition dataset provides state-of-the-science, consistent and evaluated time slice (spanning 1850–2100) global gridded deposition fields for use in a wide range of climate and ecological studies.

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.

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