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

Mapping Intimacies ◽

10.5194/acp-2017-145 ◽

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.

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Subtropical subsidence and surface deposition of oxidized mercury produced in the free troposphere

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-8999-2017 ◽

2017 ◽

Vol 17 (14) ◽

pp. 8999-9017 ◽

Cited By ~ 9

Author(s):

Viral Shah ◽

Lyatt Jaeglé

Keyword(s):

Boundary Layer ◽

Dry Deposition ◽

Wet Deposition ◽

Transport Model ◽

Lower Troposphere ◽

Deposition Flux ◽

Surface Deposition ◽

Middle Troposphere ◽

Western Us ◽

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). We evaluate our 2-year simulation (2013–2014) against observations of Hg(II) wet deposition as well as surface and free-tropospheric observations of Hg(II), finding reasonable agreement. 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 US, South America, South Africa, and Australia is produced in the upper and middle troposphere, whereas 26–66 % of surface Hg(II) over the eastern US, Europe, and East Asia, and South Asia is directly emitted. The influence of directly emitted Hg(II) near emission sources is likely higher but cannot be quantified by our coarse-resolution global model (2° latitude  ×  2.5° longitude). 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 Mercury Deposition Network 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 the dry subtropical subsidence regions. Hg(II) present in these regions accounts for 74 % of Hg(II) at 500 hPa over the continental US and more than 60 % of the surface Hg(II) over high-altitude areas of the western US. Globally, it accounts for 78 % of the tropospheric Hg(II) mass and 61 % of the total Hg(II) deposition. During the Nitrogen, Oxidants, Mercury, and Aerosol Distributions, Sources, and Sinks (NOMADSS) aircraft campaign, the contribution of Hg(II) from the dry subtropical regions was found to be 75 % when measured Hg(II) exceeded 250 pg m−3. Hg(II) produced in the upper and middle troposphere subsides in the anticyclones, where the dry conditions inhibit the loss of Hg(II). Our results highlight the importance the subtropical anticyclones as the primary conduits for the production and export of Hg(II) to the global atmosphere.

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-14-2233-2014 ◽

2014 ◽

Vol 14 (5) ◽

pp. 2233-2244 ◽

Cited By ~ 42

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.

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Environmental effect of heavy metals deposition in arid city

Global NEST Journal ◽

10.30955/gnj.003143 ◽

2019 ◽

Keyword(s):

Heavy Metals ◽

Dry Deposition ◽

Arid Region ◽

Wet Deposition ◽

Environmental Effect ◽

Deposition Flux ◽

Rain Event ◽

Heating Period ◽

Deposition Fluxes ◽

Wet Deposition Flux

<p>This paper analysis the contents and variation of heavy metals in wet and dry deposition in Changji (Xinjiang, China) revealed their reducing regularity for heavy metals in atmosphere in arid area. Samples (including 84 dry deposition samples and 16 wet deposition samples) were collected from January 2016 to December 2016, and the contents of heavy metals (Ni, Cu, Cd and Pb) were analyzed by AA-7000 atomic absorption spectrophotometer. The dry deposition fluxes of Ni, Cu, Cd and Pb are 3.70 mg/( m2.a), 4.81 mg/( m2. a), 0.53 mg/( m2•a) and 22.74 mg/( m2•a), respectively; the wet deposition fluxes of Ni, Cu, Cd and Pb are 0.77mg/( m2•a), 3.25mg/( m2•a), 0.04mg/( m2•a) and 0.11mg/( m2•a), respectively. Each of the four heavy metals deposition fluxes during heating period was higher than non-heating period, especially for Pb and Cd, which is mainly due to the emission of coal combustion for heating. During sampling periods, the ratio of wet deposition flux to total for Ni, Cu, Cd and Pb are 17.21%, 40.33%, 7.67% and 0.48%, respectively; the wet deposition flux is far less than dry deposition, especially for Pb. The rate of dry deposition is lower than wet deposition, however dry deposition plays an important role in scavenging heavy metals in arid region. Arid region has a low intensity and frequency of rain event, heavy metals were mainly scavenging by dry deposition attribute to its continuous and dependable process. Dry deposition has much more environmental effect on heavy metal in arid region.</p>

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-28309-2013 ◽

2013 ◽

Vol 13 (11) ◽

pp. 28309-28341 ◽

Cited By ~ 1

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.

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Total atmospheric mercury deposition in forested areas in South Korea

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-7653-2016 ◽

2016 ◽

Vol 16 (12) ◽

pp. 7653-7662 ◽

Cited By ~ 12

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.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-9849-2013 ◽

2013 ◽

Vol 13 (4) ◽

pp. 9849-9893 ◽

Cited By ~ 2

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.

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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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Impacts of Anthropogenic Emissions and Meteorological Variation on Hg Wet Deposition in Chongming, China

Atmosphere ◽

10.3390/atmos11121301 ◽

2020 ◽

Vol 11 (12) ◽

pp. 1301

Author(s):

Yi Tang ◽

Qingru Wu ◽

Wei Gao ◽

Shuxiao Wang ◽

Zhijian Li ◽

...

Keyword(s):

Wet Deposition ◽

Warm Season ◽

Meteorological Condition ◽

Anthropogenic Emissions ◽

Deposition Flux ◽

Wet Deposition Flux ◽

Meteorological Variation ◽

Global Concern ◽

The Impact

Mercury (Hg) is a ubiquitous environmental toxicant that has caused global concern due to its persistence and bioaccumulation in the environment. Wet deposition is a crucial Hg input for both terrestrial and aquatic environments and is a significant indicator for evaluating the effectiveness of anthropogenic Hg control. Rainwater samples were collected from May 2014 to October 2018 in Chongming Island to understand the multi-year Hg wet deposition characteristics. The annual Hg wet deposition flux ranged from 2.6 to 9.8 μg m−2 yr−1 (mean: 4.9 μg m−2 yr−1). Hg wet deposition flux in Chongming was comparable to the observations at temperate and subtropical background sites (2.0–10.2 μg m−2 yr−1) in the northern hemisphere. Hg wet deposition flux decreased from 8.6 μg m−2 yr−1 in 2014–2015 to 3.8 μg m−2 yr−1 in 2016 and was attributed to a decrease in the volume-weighted mean (VWM) Hg concentration (−4.1 ng L−1 yr−1). The reduced VWM Hg was explained by the decreasing atmospheric Hg and anthropogenic emissions reductions. The annual Hg wet deposition flux further decreased from 3.8 μg m−2 in 2016 to 2.6 μg m−2 in 2018. The reduction of warm season (April–September) rainfall amounts (356–845 mm) mainly contributed to the Hg wet deposition flux reduction during 2016–2018. The multi-year monitoring results suggest that long-term measurements are necessary when using wet deposition as an indicator to reflect the impact of anthropogenic efforts on mercury pollution control and meteorological condition variations.

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Observed Evolution of Northward-Propagating Intraseasonal Variation over the Western Pacific: A Case Study in Boreal Early Summer

Monthly Weather Review ◽

10.1175/mwr-d-12-00011.1 ◽

2013 ◽

Vol 141 (2) ◽

pp. 690-706 ◽

Cited By ~ 4

Author(s):

Masaki Katsumata ◽

Hiroyuki Yamada ◽

Hisayuki Kubota ◽

Qoosaku Moteki ◽

Ryuichi Shirooka

Keyword(s):

Boundary Layer ◽

Large Scale ◽

Lower Troposphere ◽

Western Pacific ◽

Boreal Summer ◽

Intraseasonal Variation ◽

Middle Troposphere ◽

Inactive Period ◽

The Western Pacific

Abstract This report describes the in situ observed evolution of the atmospheric profile during an event of the boreal summer intraseasonal variation (BSISV) in the tropical western Pacific Ocean. The convectively active region of the BSISV proceeded northward over the sounding and radar network. Over the array, the situation changed from a convectively inactive period to an active period. Inspection of the sounding data revealed the gradual moistening of the lower troposphere during the convectively inactive period. The sounding-derived heat and moisture budget analyses indicated that both the convective- and large-scale processes caused moistening of the lower and middle troposphere where the radar echo tops were observed most frequently. This study is the first to identify such a “preconditioning” process for the BSISV in the western Pacific using detailed in situ observational data. During the preconditioning, an increase in CAPE was observed, as in previous studies of the MJO. An increase of moisture in the boundary layer was responsible for the increase of CAPE. The large-scale horizontal convergence in the boundary layer may be a key factor to moisten the boundary layer through the convective-scale processes, as well as through the large-scale processes to moisten the lower and middle troposphere.

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