Hg Concentrations In Precipitation Research Articles

Direct Measurement of Mercury Deposition at Rural and Suburban Sites in Washington State, USA

Because of mercury’s (Hg) capacity for long-range transport in the atmosphere, and its tendency to bioaccumulate in aquatic biota, there is a critical need to measure spatial and temporal patterns of Hg atmospheric deposition. Dry deposition of Hg is commonly calculated as the product of a measured atmospheric concentration and an assumed deposition velocity. An alternative is to directly assess Hg deposition via accumulation on surrogate surfaces. Using a direct measurement approach, this study quantified Hg deposition at a rural site (Pullman) and suburban site (Puyallup) in Washington State using simple, low-cost equipment. Dry deposition was measured using an aerodynamic “wet sampler” consisting of a Teflon plate, 35 cm in diameter, holding a thin layer (2.5 mm) of recirculating acidic aqueous receiving solution. In addition, wet Hg deposition was measured using a borosilicate glass funnel with a 20-cm-diameter opening and a 1 L Teflon sampling bottle. Hg deposition was estimated based on changes in total Hg in the aqueous phase of the samplers. Dry Hg deposition was 2.4 ± 1.4 ng/m2·h (average plus/minus standard deviation; n = 4) in Pullman and 1.3 ± 0.3 ng/m2·h (n = 6) in Puyallup. Wet Hg deposition was 7.0 ± 4.8 ng/m2·h (n = 4) in Pullman and 1.1 ± 0.2 ng/m2·h (n = 3) in Puyallup. Relatively high rates of Hg deposition in Pullman were attributed to regional agricultural activities that enhance mercury re-emission and deposition including agricultural harvesting and field burning. Hg concentration in precipitation negatively correlated with precipitation depth, indicating that Hg was scavenged from the atmosphere during the beginning of storm events. Because of their relative simplicity and robustness, direct measurement approaches such as those described in this study are useful in assessing Hg deposition, and for comparing results to less direct estimates and model estimates of Hg deposition.

Mercury and trace metal wet deposition across five stations in Alaska: controlling factors, spatial patterns, and source regions

Abstract. A total of 1360 weeks of mercury (Hg) wet deposition data were collected by the state of Alaska Department of Environmental Conservation and the U.S. National Park Service across five stations spanning up to 8 years. Here, we analyze concentration patterns, source regions, and seasonal and annual Hg deposition loadings across these five sites in Alaska, along with auxiliary trace metals including Cr, Ni, As, and Pb. We found that Hg concentrations in precipitation at the two northernmost stations, Nome (64.5∘ N) along the coast of the Bering Sea and the inland site of Gates of the Arctic (66.9∘ N), were statistically higher (average of 5.3 and 5.5 ng L−1, respectively) than those at the two lowest-latitude sites, Kodiak Island (57.7∘ N, 2.7 ng L−1) and Glacier Bay (58.5∘ N, 2.6 ng L−1). These differences were largely explained by different precipitation regimes, with higher precipitation at the lower-latitude stations leading to dilution effects. The highest annual Hg deposition loads were consistently observed at Kodiak Island (4.80±1.04 µg m−2), while the lowest annual deposition was at Gates of the Arctic (2.11±0.67 µg m−2). Across all stations and collection years, annual precipitation strongly controlled annual Hg deposition, explaining 73 % of the variability in observed annual Hg deposition. The data further showed that annual Hg deposition loads across all five Alaska sites were consistently among the lowest in the United States, ranking in the lowest 1 % to 5 % of over 99 monitoring stations. Detailed back-trajectory analyses showed diffuse source regions for most Hg deposition sites suggesting largely global or regional Hg sources. One notable exception was Nome, where we found increased Hg contributions from the western Pacific Ocean downwind of East Asia. Analysis of other trace elements (As, Cr, Cu, Ni, Pb, Se, Zn) from Dutch Harbor, Nome, and Kodiak Island showed generally higher trace metal concentrations at the northern station Nome compared to Kodiak Island further to the south, with concentrations at Dutch Harbor falling in between. Across all sites, we find two distinct groups of correlating elements: Cr and Ni and As and Pb. We attribute these associations to possibly different source origins, whereby sources of Ni and Cr may be derived from crustal (e.g., dust) sources while As and Pb may include long-range transport of anthropogenic pollution. Hg was not strongly associated with either of these two groups.

Primary effects of changes in meteorology vs. anthropogenic emissions on mercury wet deposition: A modeling study

In this study we investigated the respective contributions of changing meteorology and anthropogenic emissions to Hg wet deposition in New York State (NYS), which illustrated quantitatively how the variations in meteorological conditions modified the response of Hg wet deposition to anthropogenic emission reductions in NYS. A regional chemical transport model, CMAQ-newHg-Br (Ye et al., 2018), was employed driven by four sets of meteorological fields (2004, 2005, 2007, and 2010) and two anthropogenic emission inventories (NEI, 2005 and 2011). Four major findings emerged from this study. First, simulated Hg wet deposition flux in NYS was greatly affected by variation in meteorological conditions, ranging from a 91% decrease to a factor of 5 increase in monthly Hg wet deposition, whereas it hardly responded (2%) to a near doubling of emissions in the northeastern U.S. Second, the precipitation amount dominated interannual and seasonal variations of Hg wet deposition over all other meteorological variables, with total (= convective + non-convective) precipitation explained 60% of Hg wet deposition variance in an urban environment compared to convective precipitation alone explaining 65% in a rural area. Third, large-scale atmospheric circulation influenced regional transport greatly leading to out-of-state anthropogenic emissions explaining at least 80% of Hg wet deposition changes in a NYS urban environment. Fourth, higher Hg concentrations in precipitation and higher atmospheric reactive mercury concentrations in urban areas were related to calm conditions due likely to regional build-up of emissions, whereas in rural areas photochemical oxidation of gaseous elemental mercury was a more important source of reactive mercury. Solar radiation variance was found to explain 41–55% of the variance in simulated reactive mercury concentrations. Given that more than 95% of the US is rural lands and the majority of water bodies occur in rural areas, a realistic chemical mechanism for photochemical gaseous elemental mercury oxidation is paramount to accurate simulation of reactive mercury formation and Hg wet deposition in the US.

Characteristics of total and methyl mercury in precipitation in Seoul, Korea

To investigate the seasonal distribution of mercury (Hg) in precipitation in Seoul, Korea, event based total mercury (THg) and methyl mercury (MeHg) in precipitation samples were collected for one year. During sampling periods, volume weighted mean (VWM) concentration of THg and MeHg were 16.91 and 0.042 ng L−1, and wet deposition flux of THg and MeHg was 5.96 and 0.01 μg m−2, respectively. The proportion of MeHg in THg in the rainwater ranged from 0.01% to 2.22% with a mean value of 0.5%. The THg and MeHg concentration in precipitation was the highest in the winter, while wet deposition flux of THg and MeHg were highest in summer. There were significant negative correlations between THg and rain amount (p = 0.034), and between MeHg and the rain amount (p = 0.023), indicating that Hg concentrations in precipitation decreased as the amount of precipitation increased, especially in summer. THg concentration was higher when precipitation amount in one event was less than 20 mm, implying that 20 mm of precipitation can be a threshold value showing the Hg wash-out effect from the atmosphere. A significant correlation was observed between THg and NO3− (r2 = 0.65) and Cl− ion (r2 = 0.60), and between MeHg and SO42− ion (r2 = 0.52) concentrations in precipitation. We also found a weak relationship between MeHg and DOC concentrations in precipitation.

Mercury wet deposition and speciated mercury air concentrations at rural and urban sites across New York state: Temporal patterns, sources and scavenging coefficients

Measurements of ambient speciated mercury (Hg) concentrations and Hg wet deposition were made at two urban sites (Bronx, NY and Rochester, NY) and one rural site (Potsdam, NY) in New York State in 2013 and 2014 to: 1) determine the factors influencing Hg wet deposition concentrations, 2) identify the contribution of gaseous oxidized Hg (GOM) and particulate bound Hg (PBM) scavenging to Hg wet deposition concentrations, and 3) identify potential source areas associated with high concentration events. The Bronx had the highest mean gaseous elemental Hg (GEM) and GOM concentrations, Rochester had the highest mean PBM and the lowest GOM concentrations, and Potsdam had the lowest mean GEM and PBM concentrations. The annual volume weighted mean (VWM) Hg concentrations and Hg wet deposition fluxes in the Bronx, Rochester, and Potsdam were significantly different with mean values of 10.3 ± 8.16, 10.2 ± 9.06, and 5.07 ± 1.79 ngL−1 and 8.45 ± 0.64, 6.65 ± 0.21, and 5.25 ± 0.49 μg/m2 year−1, respectively. Hg wet deposition flux and precipitation depth were positively correlated at all three sites as were Hg concentration in precipitation and weekly GOM concentrations at the Bronx and Potsdam sites. Scavenging coefficients (SC) of 680, 630, 850 for GOM and 410, 320, and 410 for PBM at Bronx, Rochester, and Potsdam, respectively, suggest GOM is responsible for most of the scavenged Hg. Measured GOM and PBM concentrations were relatively constant before precipitation events and Hg concentrations in precipitation did not vary significantly during precipitation events implying the scavenging process mainly occurred in clouds. VWM Hg concentrations, monthly accumulated Hg flux, and SCs for GOM and PBM were higher at the urban sites and significantly different for non-snow and snow events. Local sources appeared more important at the rural site while regional sources affected high urban concentrations.

Spatio-temporal variation of total mercury in precipitation in the largest industrial base in China: impacts of meteorological factors and anthropogenic activities

A 12-month investigation of total mercury (Hg) in event-based precipitation was performed in China's biggest industrial base, Yangtze River Delta, a hotspot of anthropogenic Hg emissions. Concentrations of total Hg in precipitation were measured, and the spatial and temporal variations of Hg were addressed. The results show that Hg concentrations (median=92 ng L−1) are comparable to the reports of other cities in China, but higher than those of remote sites. In spatial, Hg levels are significantly higher in urban and suburban precipitation than in rural samples. The pH, precipitation depth and antecedent drying period appear to be potential factors influencing Hg concentrations in precipitation, but in general no strong correlation was found between Hg and individual parameters. A seasonal variation of Hg in precipitation was found, and the concentrations in winter are generally higher, possibly associated with fossil fuel combustion. In addition, the dominant wind direction was found to be a factor influencing seasonal pattern of Hg by atmospheric transport of air pollutants. The backward trajectories suggest that local sources, for example, emissions from coal combustion and industry activities, are possibly important contributors to Hg in precipitation.

Mercury in precipitation over the coastal zone of the southern Baltic Sea, Poland.

An investigation of atmospheric mercury was conducted in the urban coastal zone of the Gulf of Gdansk (Baltic Sea, Poland) in 2008. Rainwater samples were collected in bulk samplers and Hg concentration was determined using AAS method. Total mercury concentration ranged from 1.9 to 14.8 ng l−1 (the mean was 8.3 ng l−1 with standard deviation ±3.7), out of which about 34 % were water-soluble Hg(II) forms. Distribution of Hg species in rainwater was related to both the emission source and the atmospheric processes. During the sampling period, two maxima of Hg concentration in precipitation were observed: the first in the cold season and the second one in the warm season. Elevated concentrations of Hg in wintertime precipitation were generally the result of local urban atmospheric emission connected with the following anthropogenic sources: intensive combustion of fossil fuels in domestic furnaces, individual power/heat generating plants, and motor vehicles. During summertime, Hg° re-emitted from contaminated land and sea surfaces was photochemically oxidized by active atmospheric substances (e.g., hydroxyl radicals, hydrogen peroxide, halogens) and could be an additional source of atmospherically deposited Hg. The results presented in this work indicate that rainwater Hg concentration and deposition values are not much higher in comparison with other urban locations along the Baltic Sea basin and other coastal cities. However, the elevated mercury concentration in rainwater and, consequently, higher deposition ratio could appear occasionally as an effect of intensive anthropogenic emissions (domestic heating) and/or photochemical reactions.

Mercury in precipitation at an urbanized coastal zone of the Baltic Sea (Poland).

Wet deposition is an important source of metals to the sea. The temporal variability of Hg concentrations in precipitation, and the impact of air masses of different origins over the Polish coastal zone were assessed. Samples of precipitation were collected (August 2008–May 2009) at an urbanized coastal station in Poland. Hg analyses were conducted using CVAFS. These were the first measurements of Hg concentration in precipitation obtained in the Polish coastal zone. Since Poland was identified as the biggest emitter of Hg to the Baltic, these data are very important. In the heating and non-heating season, Hg concentrations in precipitation were similar. Hg wet deposition flux dominated in summer, when the production of biomass in the aquatic system was able to actively adsorb Hg. Input of metal to the sea was attributed to regional and distant sources. Maritime air masses, through transformation of Hg(0), were an essential vector of mercury in precipitation.

Mercury Wet Deposition and Speciated Air Concentrations from Two Urban Sites in New York State: Temporal Patterns and Regional Context

Since 2008, ambient speciated mercury (Hg) concentrations and weekly Hg wet deposition have been measured at two urban locations in New York-Rochester and New York City (borough of Bronx). These measurements were initiated to establish ambient Hg baselines ahead of anticipated emissions reductions, as well as characterize air concentrations and deposition at two different urban settings. In this paper seasonal and regional patterns in Hg wet deposition are presented, as well as seasonal, day of week and diurnal patterns in ambient Hg species at these two sites. The mean (and median) Hg concentration in precipitation was 9.56 ng/L (8.37 ng/L) at the Bronx site, and 9.95 ng/L (8.30 ng/L) at Rochester. Mean ambient air concentrations of gaseous elemental Hg (GEM), reactive gaseous Hg (RGM), and particle-bound Hg (PHM) at the Bronx and Rochester sites were 1.52 and 1.40 ng/m^3, 6.26 and 8.24 pg/m^3, and 7.96 and 13.48 pg/m^3, respectively. Conditional probability function analysis was used to examine potential source regions impacting these two sites. Using these data we were able to examine monthly and diurnal patterns in speciated ambient Hg; however, more research is needed to more fully characterize potential emission sources that impact these sites.

A Great Lakes Atmospheric Mercury Monitoring network: Evaluation and design

As many as 51 mercury (Hg) wet-deposition-monitoring sites from 4 networks were operated in 8 USA states and Ontario, Canada in the North American Great Lakes Region from 1996 to 2010. By 2013, 20 of those sites were no longer in operation and approximately half the geographic area of the Region was represented by a single Hg-monitoring site. In response, a Great Lakes Atmospheric Mercury Monitoring (GLAMM) network is needed as a framework for regional collaboration in Hg-deposition monitoring. The purpose of the GLAMM network is to detect changes in regional atmospheric Hg deposition related to changes in Hg emissions. An optimized design for the network was determined to be a minimum of 21 sites in a representative and approximately uniform geographic distribution. A majority of the active and historic Hg-monitoring sites in the Great Lakes Region are part of the National Atmospheric Deposition Program (NADP) Mercury Deposition Network (MDN) in North America and the GLAMM network is planned to be part of the MDN.To determine an optimized network design, active and historic Hg-monitoring sites in the Great Lakes Region were evaluated with a rating system of 21 factors that included characteristics of the monitoring locations and interpretations of Hg data. Monitoring sites were rated according to the number of Hg emissions sources and annual Hg emissions in a geographic polygon centered on each site. Hg-monitoring data from the sites were analyzed for long-term averages in weekly Hg concentrations in precipitation and weekly Hg-wet deposition, and on significant temporal trends in Hg concentrations and Hg deposition. A cluster analysis method was used to group sites with similar variability in their Hg data in order to identify sites that were unique for explaining Hg data variability in the Region. The network design included locations in protected natural areas, urban areas, Great Lakes watersheds, and in proximity to areas with a high density of annual Hg emissions and areas with high average weekly Hg wet deposition. In a statistical analysis, relatively strong, positive correlations in the wet deposition of Hg and sulfate were shown for co-located NADP Hg-monitoring and acid-rain monitoring sites in the Region. This finding indicated that efficiency in regional Hg monitoring can be improved by adding new Hg monitoring to existing NADP acid-rain monitoring sites.Implementation of the GLAMM network design will require Hg-wet-deposition monitoring to be: (a) continued at 12 MDN sites active in 2013 and (b) restarted or added at 9 NADP sites where it is absent in 2013. Ongoing discussions between the states in the Great Lakes Region, the Lake Michigan Air Directors Consortium (a regional planning entity), the NADP, the U.S. Environmental Protection Agency, and the U.S. Geological Survey are needed for coordinating the GLAMM network.

Evaluation of discrepancy between measured and modelled oxidized mercury species

Abstract. L. Zhang et al. (2012), in a recent report, compared model estimates with new observations of oxidized and particulate mercury species (Hg2+ and Hgp) in the Great Lakes region and found that the sum of Hg2+ and Hgp varied between a factor of 2 to 10 between measurements and model. They suggested too high emission inputs as Hg2+ and too fast oxidative conversion of Hg0 to Hg2+ and Hgp as possible causes. This study quantitatively explores measurement uncertainties in detail. These include sampling efficiency, composition of sample, interfering species and calibration errors. Model (Global/Regional Atmospheric Heavy Metals Model – GRAHM) sensitivity experiments are used to examine the consistency between various Hg measurements and speciation of Hg near emission sources to better understand the discrepancies between modelled and measured concentrations of Hg2+ and Hgp. We find that the ratio of Hg0, Hg2+ and Hgp in the emission inventories, measurements of surface air concentrations of oxidized Hg and measurements of wet deposition are currently inconsistent with each other in the vicinity of emission sources. Current speciation of Hg emissions suggests higher concentrations of Hg2+ in air and in precipitation near emission sources; however, measured air concentrations of Hg2+ and measured concentrations of Hg in precipitation are not found to be significantly elevated near emission sources compared to the remote regions. The averaged unbiased root mean square error (RMSE) between simulated and observed concentrations of Hg2+ is found to be reduced by 42% and for Hgp reduced by 40% for 21 North American sites investigated, when a ratio for Hg0 : Hg2+ : Hgp in the emissions is changed from 50 : 40 : 10 (as specified in the original inventories) to 90 : 8 : 2. Unbiased RMSE reductions near emissions sources in the eastern United States and Canada are found to be reduced by up to 58% for Hg2+. Significant improvement in the model simulated spatial distribution of wet deposition of mercury in North America is noticed with the modified Hg emission speciation. Measurement-related uncertainties leading to lower estimation of Hg2+ concentrations are 86%. Uncertainties yielding either to higher or lower Hg2+ concentrations are found to be 36%. Finally, anthropogenic emission uncertainties are 106% for Hg2+. Thus it appears that the identified uncertainties for model estimates related to mercury speciation near sources, uncertainties in measurement methodology and uncertainties in emissions can close the gap between modelled and observed estimates of oxidized mercury found in L. Zhang et al. (2012). Model sensitivity simulations show that the measured concentrations of oxidized mercury, in general, are too low to be consistent with measured wet deposition fluxes in North America. Better emission inventories (with respect to speciation), better techniques for measurements of oxidized species and knowledge of mercury reduction reactions in different environments (including in-plume) in all phases are needed for improving the mercury models.

Decreases in Mercury Wet Deposition over the United States during 2004–2010: Roles of Domestic and Global Background Emission Reductions

Wet deposition of mercury (Hg) across the United States is influenced by changes in atmospheric conditions, domestic emissions and global background emissions. We examine trends in Hg precipitation concentrations at 47 Mercury Deposition Network (MDN) sites during 2004–2010 by using the GEOS-Chem nested-grid Hg simulation. We run the model with constant anthropogenic emissions and subtract the model results from the observations. This helps to remove the variability in observed Hg concentrations caused by meteorological factors, including precipitation. We find significant decreasing trends in Hg concentrations in precipitation at MDN sites in the Northeast (−4.1 ± 0.49% yr−1) and Midwest (−2.7 ± 0.68% yr−1). Over the Southeast (−0.53 ± 0.59% yr−1), trends are weaker and not significant, while over the West, trends are highly variable. We conduct model simulations assuming a 45% decrease in Hg emissions from domestic sources in the modeled period and a uniform 12% decrease in background atmospheric Hg concentrations. The combination of domestic emission reductions and decreasing background concentrations explains the observed trends over the Northeast and Midwest, with domestic emission reductions accounting for 58–46% of the decreasing trends. Over the Southeast, we overestimate the observed decreasing trend, indicating potential issues with our assumption of uniformly decreasing background Hg concentrations.

Assessing the Emission Sources of Atmospheric Mercury in Wet Deposition Across Illinois, USA

From August 2007 to August 2009, we collected event-based precipitation samples for mercury (Hg) and trace element analysis at four sites in Illinois, USA. The objectives of these measurements were to quantify the levels of Hg wet deposition across the state, and to assess the contributions to Hg in precipitation from major local and regional emission sources. The measurement sites were located in Chicago, Peoria, Nilwood, and Carbondale, IL. We were not able to identify a clear spatial gradient in Hg wet deposition among the sites. At all four locations we frequently observed Hg concentrations in precipitation > 25 ng/L, while each site received > 10 μg/m2 of Hg wet deposition annually, suggesting a substantial impact from local and regional anthropogenic emission sources. We applied the multivariate statistical receptor model Positive Matrix Factorization (PMF) to the measured Hg and trace element wet deposition amounts at the four sites. The results suggested that 60-83% of total Hg deposition at each site could be attributed to coal combustion emissions. Although we identified other source signatures in the precipitation composition, including cement manufacturing, metal smelting / waste incineration, and iron-steel production, these sources contributed substantially less to the measured amounts of Hg wet deposition. We also applied the hybrid receptor model Quantitative Transport Bias Analysis (QTBA) to the Hg wet deposition data from each site to identify the major source regions associated with the measured values. Results suggested that sources in the Chicago/Gary, St. Louis, and Ohio River Valley urban/industrial areas had a substantial impact on Hg wet deposition, strongly supporting the conclusion that local and regional coal combustion was the largest source of Hg wet deposition in Illinois.

Mercury wet deposition in the eastern United States: characteristics and scavenging ratios

Wet deposition is an important atmospheric mercury (Hg) pathway between air and terrestrial ecosystems. It is measured at numerous locations in the United States (U. S.) as part of the Mercury Deposition Network (MDN). The annual Hg wet deposition flux in 2009 at four locations in the northeastern U. S. (MDN sites MD08, VT99, NY20, and NY43) ranged from 6.4 to 13.4 μg per m(2) year which is higher than modeled reactive Hg (RM) dry deposition for this region. The highest ambient RM concentrations were seen at MD08, which is closest to significant anthropogenic sources; however, the volume-weighted mean Hg concentrations in precipitation were similar at these four sites. Mass based scavenging ratios (SC) of RM ranged from 1700 to 4500. Differences in SCs were likely a result of differences in meteorological conditions, the forms of RM in the atmosphere, vertical concentration variations, and measurement uncertainties, including precipitation depth and RM concentrations. RM SCs were higher than those reported for other soluble species. Multiple linear regression suggests that gaseous oxidized Hg is responsible for the majority of the scavenged RM.

Wet deposition mercury fluxes in the Canadian sub-Arctic and southern Alberta, measured using an automated precipitation collector adapted to cold regions

This paper reports mercury (Hg) concentrations and fluxes in precipitation that was collected from 2006 to 2008 at three sites in Canada: sub-Arctic boreal forest, sub-Arctic coast, and southern Alberta, using cold-adapted precipitation collectors which operated reliably at temperatures below −30 °C during the study. The southern Alberta site (Crossfield) may be influenced by Calgary urban air, whereas the sub-Arctic coastal (Churchill, Manitoba) and boreal forest (Fort Vermilion, Alberta) sites are in more remote northern areas. Annual mean Hg concentrations in precipitation (5.0–9.2 ng L −1) at the study sites were in the lower half of the range reported for southern Canada and the USA by the Mercury Deposition Network (MDN). But owing to typically low precipitation rates, gross wet Hg fluxes (0.54–2.0 μg m −2 yr −1) were among the lowest reported by MDN, with Crossfield having about twice the flux in 2007 of the other two sites. Flux was significantly correlated with precipitation, and thus was highest in summer (June–August) and lowest during winter, a pattern typical of other temperate continental locations. There was no evidence of higher wet Hg fluxes or concentrations in springtime at Churchill where atmospheric mercury depletion events (AMDEs) occur. Measured gross deposition fluxes at the study locations were ∼2–8 times lower than estimated by GEOS-Chem and GRAHM atmospheric models. The largest discrepancy occurred for Churchill, which raises the question of how well Hg deposition from AMDEs is described by current models. Better agreement between measurements and models was obtained from MDN stations in Alberta and Alaska, where wet Hg fluxes were 2–10 times higher than the study sites either because of power plant emissions (Alberta), or because of high precipitation rates (Alaska).

대기 중 수은의 습식 침적 평가: 소양호를 중심으로

The important source of the mercury in water-column is the influx of atmosphere mercury, via dry and wet deposition. In this study, wet deposition of mercury was estimated to be during 15 months at the Lake Soyang, which is a little higher than those observed in the several rural US Mercury Deposition Network (MDN) sites with similar precipitation depth. The mercury concentration in precipitation did not show a positive correlation with atmospheric RGM (reactive gaseous mercury) concentration, while maintaining good correlation with atmospheric at Soyang Dam. This result suggests that the contribution of particulate Hg to the total Hg wet deposition should be more significant than that of RGM. In this study, both precipitation depth and precipitation type affected the amount of wet deposition and the concurrent mercury levels in precipitation. There was generally an inverse relationship between precipitation depth and Hg concentration in precipitation. Precipitation type was another factor that exerted controls on the Hg concentration in precipitation. As a result, the highest concentration of Hg was observed in snow, followed by in mixture (snow+rain) and in rain.

Methyl and total mercury in precipitation in the Great Lakes region

Methylmercury (MeHg) and total mercury (THg) concentrations were measured in precipitation collected from five US sites in the Great Lakes region: three sites on the southern shore of Lake Superior (Brule River, WI, Eagle Harbor, MI, and Tahquamenon Falls, MI), one at Isle Royale National Park (MI), and one in southern Wisconsin (Devil's Lake), between May 1997 and December 2003. MeHg and THg concentrations at these sites were compared to MeHg and THg concentrations in precipitation collected at the Experimental Lakes Area (ELA) in north-western Ontario, Canada. Detectable MeHg concentrations (>0.01 ng L −1) were found in the majority of rain and snow samples collected from all sites (range=0.01–0.85 ng L −1). In general, the lowest MeHg concentrations were observed in samples taken at Tahquamenon Falls and the ELA, and the highest MeHg concentrations in precipitation were observed in samples collected from Brule River and Eagle Harbor. Total Hg concentrations in precipitation were generally between 10 and 60 ng L −1, exceeding 60 ng L −1 in one precipitation event sampled from each of Brule River, Isle Royale, Tahquamenon Falls, and Devil's Lake. The proportion of THg that was MeHg (%MeHg), was less than 6% at all sites, with the exception of seven events at Tahquamenon Falls and two events at the ELA that were between 6% and 18% MeHg. Generally, the highest MeHg concentrations were found in low-volume precipitation events (<100 mL). At Tahquamenon Falls, meteorological analysis indicated that events with higher MeHg concentrations and %MeHg exceeding 6% were generally associated with lake effect precipitation and weak local winds.

Mercury Transport in a High-Elevation Watershed in Rocky Mountain National Park, Colorado

Mercury (Hg) was measured in stream water and precipitation in the Loch Vale watershed in Rocky Mountain National Park, Colorado, during 2001–2002 to investigate processes controlling Hg transport in high-elevation ecosystems. Total Hg concentrations in precipitation ranged from 2.6 to 36.2 ng/L and showed a strong seasonal pattern with concentrations that were 3 to 4 times higher during summer months. Annual bulk deposition of Hg was 8.3 to 12.4 μ g/m2 and was similar to deposition rates in the Midwestern and Northeastern U.S. Total Hg concentrations in streams ranged from 0.8 to 13.5 ng/L and were highest in mid-May on the rising limb of the snowmelt hydrograph. Stream-water Hg was positively correlated with dissolved organic carbon suggesting organically complexed Hg was flushed into streams from near-surface soil horizons during the early stages of snowmelt. Methylmercury (MeHg) in stream water peaked at 0.048 ng/L just prior to peak snowmelt but was at or below detection (< 0.040 ng/L) for the remainder of the snowmelt season. Annual export of total Hg in Loch Vale streams ranged from 1.2 to 2.3 μ g/m2, which was less than 20% of wet deposition, indicating the terrestrial environment is a net sink of atmospheric Hg. Concentrations of MeHg in stream water and corresponding watershed fluxes were low, indicating low methylation rates or high demethylation rates or both.

Mercury concentrations in coastal California precipitation: Evidence of local and trans‐Pacific fluxes of mercury to North America

Because of mercury's (Hg) relatively high vapor pressure and long (0.5–2 years) atmospheric residence, there is the potential for long‐range transport of contaminant Hg. Many studies have focused on that transport and deposition in central and eastern North America, Europe, and the Arctic, but there has been little research on the cycling of Hg in the western coast of North America. That deficiency is addressed in this preliminary study, which indicates there is long‐range transport of Hg across the North Pacific. This transport is evidenced by the elevated (relative to equatorial and theoretical baseline) Hg concentrations in rainwater collected on the coast of California, as well as by the positive correlation between North Pacific storm tracks and Hg concentrations, with maximum concentrations associated with storms from 20°–40° latitude. Those tracks trace air masses containing industrial emissions with peak O3 concentrations moving eastward off the Asian continent. The Asian fluxes appear to enhance Hg concentrations both directly, through the emission of particle‐bound Hg and reactive Hg2+, and indirectly, by increasing the rate of oxidation of Hg0 in the atmosphere. Superimposed on the trans‐Pacific background of industrial Hg is a local signal, with elevated concentrations at the urban site relative to the more pristine coastal site in California. This secondary enrichment is tentatively attributed to elevated local emissions of redox species, including O3 and its precursors, which increase oxidation rates of Hg0 in the atmosphere and Hg concentrations in precipitation.

Estimation of atmospheric input of mercury to South Lake and Jingyue Pool

Taking South Lake and Jingyue Pool in Changchun as examples, we determined particulate Hg in ambient air and Hg concentration in precipitation. Results indicated that particulate Hg in air and Hg concentration in precipitation in both sites in nonheating period were lower than that in heating period, which is influenced by coal combustion. The annual particulate Hg concentrations of South Lake and Jingyue Pool were 0.254ng/m3 and 0. 109ng/m3. The yearly average Hg concentrations in precipitation were 0.268µg/L(South Lake) and 0.108µg/L(Jingyue Pool). The higher particulate Hg concentration in air and Hg concentration in precipitation in South Lake than that of Jingyue Pool indicated that mercury deposition was influenced by anthropogenic sources (especially from coas combustion). Hg concentration in precipitation is related with particulate Hg in the atmosphere. Dry deposition fluxes were estimated by using dry deposition model on the base of particulate Hg concentrations in the atmosphere, they were 35.5µg/(m2. a) for South lake and 15.3µg/(m2. a) for Jingyue Pool. Combined with precipitation amount, wet deposition fluxes were estimated in these two sites, 152.2µg/(m2. a) for South Lake and 6.1.2µg/(m2. a) for Jingyue Pool. Atmospheric Hg deposition fluxes were 160.2g/a for South Lake and 328.62g/a for Jingyue Pool.