RGM Concentrations Research Articles

Annual ambient atmospheric mercury speciation measurement from Longjing, a rural site in Taiwan.

The main purpose of this study was to monitor ambient air particulates and mercury species [RGM, Hg(p), GEM and total mercury] concentrations and dry depositions over rural area at Longjing in central Taiwan during October 2014 to September 2015. In addition, passive air sampler and knife-edge surrogate surface samplers were used to collect the ambient air mercury species concentrations and dry depositions, respectively, in this study. Moreover, direct mercury analyzer was directly used to detect the mercury Hg(p) and RGM concentrations. The result indicated that: (1) The average highest RGM, Hg(p), GEM and total mercury concentrations, and dry depositions were observed in January, prevailing dust storm occurred in winter season was the possible major reason responsible for the above findings. (2) The highest average RGM, Hg(p), GEM and total mercury concentrations, dry depositions and velocities were occurred in winter. This is because that China is the largest atmospheric mercury (Hg) emitter in the world. Its Hg emissions and environmental impacts need to be evaluated. (3) The results indicated that the total mercury ratios of Kaohsiung to that of this study were 5.61. This is because that Kaohsiung has the largest industry density (~60%) in Taiwan. (4) the USA showed average lower mercury species concentrations when compared to those of the other world countries. The average ratios of China/USA values were 89, 76 and 160 for total mercury, RGM and Hg(p), respectively, during the years of 2000-2012.

Programmable Thermal Dissociation of Reactive Gaseous Mercury, a Potential Approach to Chemical Speciation: Results from a Field Study

Programmable Thermal Dissociation (PTD) has been used to investigate the chemical speciation of Reactive Gaseous Mercury (RGM, Hg2+). RGM was collected on denuders and analyzed using PTD. The technique was tested in a field campaign at a coal-fired power plant in Pensacola, Florida. Stack gas samples were collected from ducts located after the electrostatic precipitator and prior to entering the stack. An airship was used to sample from the stack plume, downwind of the stack exit. The PTD profiles from these samples were compared with PTD profiles of HgCl2. Comparison of stack and in-plume samples suggest that the chemical speciation are the same and that it is possible to track a specific chemical form of RGM from the stack and follow its evolution in the stack plume. Comparison of the measured plume RGM with the amount calculated from in-stack measurements and the measured plume dilution suggest that the stack and plume RGM concentrations are consistent with dilution. The PTD profiles of the stack and plume samples are consistent with HgCl2 being the chemical form of the sampled RGM. Comparison with literature PTD profiles of reference mercury compounds suggests no other likely candidates for the speciation of RGM.

Atmospheric transport of speciated mercury across southern Lake Michigan: Influence from emission sources in the Chicago/Gary urban area

Quantifying the local and regional impacts of speciated mercury (Hg) emissions from major urban and industrial areas is critical for understanding Hg transport and cycling in the environment. The Chicago/Gary urban area is one location where Hg emissions from industrial sources are significant and the regional transport of emissions may contribute to elevated ambient Hg concentrations at downwind locations. From July to November 2007, we collected semi-continuous measurements of gaseous elemental Hg (Hg0), fine particulate bound Hg (Hgp), and divalent reactive gaseous Hg (RGM) in Chicago, IL and Holland, MI to characterize the impact of Chicago/Gary source emissions on Hg concentrations in southwest Michigan and to improve our overall understanding of speciated Hg transport and deposition. The mean (and median) concentrations of Hg0, Hgp, and RGM in Chicago were 2.5ng/m3 (1.9ng/m3), 9pg/m3 (5pg/m3), and 17pg/m3 (6pg/m3), respectively. In Holland the mean (and median) concentrations were 1.3ng/m3 (1.3ng/m3), 6pg/m3 (6pg/m3), and 8pg/m3 (2pg/m3), respectively. Cluster analysis of 24-hour HYSPLIT back-trajectories associated with the semi-continuous Hg measurements indicated that southwest transport from Chicago/Gary to Holland occurred during approximately 27% of the study. In Holland, under this transport regime, we observed a five-fold increase in RGM relative to the median concentration of the other transport clusters. We applied the HYSPLIT dispersion model to two case study periods to further quantify the impact of Chicago/Gary sources on southeast Michigan and investigate the role of direct transport and dispersion of speciated Hg emissions. Results suggested that more than 50% of the maximum RGM concentrations observed in Holland during the selected periods could be attributed to direct transport of primary RGM emissions from Chicago/Gary. The remaining RGM fractions are believed to be associated with Hg0 oxidation during transport over Lake Michigan.

Speciated atmospheric mercury and its potential source in Guiyang, China

Abstract Speciated atmospheric mercury (Hg) including gaseous elemental mercury (GEM), particulate Hg (PHg), and reactive gaseous Hg (RGM) were continuously measured at an urban site in Guiyang city, southwest China from August to December 2009. The averaged concentrations for GEM, PHg, and RGM were 9.72 ± 10.2 ng m −3 , 368 ± 676 pg m −3 , and 35.7 ± 43.9 pg m −3 , respectively, which were all highly elevated compared to observations at urban sites in Europe and North America. GEM and PHg were characterized by similar monthly and diurnal patterns, with elevated levels in cold months and nighttime, respectively. In contrast, RGM did not exhibit clear monthly and diurnal variations. The variations of GEM, PHg, and RGM indicate the sampling site was significantly impacted by sources in the city municipal area. Sources identification implied that both residential coal burning and large point sources were responsible to the elevated GEM and PHg concentrations; whereas point sources were the major contributors to elevated RGM concentrations. Point sources played a different role in regulating GEM, PHg, and RGM concentrations. Aside from residential emissions, PHg levels was mostly affected by small-scale coal combustion boilers situated to the east of the sampling site, which were scarcely equipped or lacking particulate control devices; whereas point sources situated to the east, southeast, and southwest of the sampling played an important role on the distribution of atmospheric GEM and RGM.

Atmospheric mercury species measured in Guiyang, Guizhou province, southwest China

Atmospheric mercury (Hg) species were measured in Guiyang City, the capital of Guizhou province, southwestern China at the Guiyang Monitoring Station Agency (GMSA) from September to November 2008 and at the Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) during February, May, and July, 2009. Monitoring results found elevated concentrations of all three Hg species in ambient air in Guiyang. Large temporal and spatial variation patterns in the resulting data were also obtained. The overall average TGM concentrations at the GMSA and IGCAS sampling sites were 7.4±4.8ngm−3 and 6.2±5.1ngm−3, respectively. The average Hg(p) and RGM concentrations at GMSA were 1330pgm−3 and 24pgm−3, and at IGCAS were 250pgm−3 and 19pgm−3, respectively. It is hypothesized that local anthropogenic sources and the seasonal variability result in the high degree of spatial and temporal variability.

아연제련시설에서의 수은 배출특성

Stationary combustion sources such as coal-fired power plants, waste incinerators, industrial manufacturing, etc. are recognized as major sources of mercury emissions. Due to rapid economic growth, zinc production in Korea has increased significantly during the last 30 years. Total zinc production in Korea exceeded 739,000 tons in 2008, and Korea is currently the third largest zinc producing country in the world. Previous studies have revealed that zinc smelting has become one of the largest single sectors of total mercury emissions in the World. However, studies on this sector are very limited, and a large gap in the knowledge regarding emissions from this sector needs to be bridged. In this paper, Hg emission measurements were performed to develop emission factors from zinc smelting process. Stack sampling and analysis were carried out utilizing the Ontario Hydro method and US EPA method 101A. Preliminary data showed that <TEX>$Hg^0$</TEX> concentrations in the flue gas ranged from 4.56 to <TEX>$9.90\;{\mu}g/m^3$</TEX> with an average of <TEX>$6.40\;{\mu}g/m^3$</TEX>, Hg(p) concentrations ranged from 0.03 to <TEX>$0.09\;{\mu}g/m^3$</TEX> with an average of <TEX>$0.04\;{\mu}g/m^3$</TEX>, and RGM concentrations ranged from 0.23 to <TEX>$1.17\;{\mu}g/m^3$</TEX> with an average of <TEX>$6.40\;{\mu}g/m^3$</TEX>. To date, emission factors of 7.5~8.0 g/ton for Europe, North America and Australia, and of 20 or 25 g/ton for Africa, Asia and South America are widely accepted by researchers. In this study, Hg emission factors were estimated using the data measured at the commercial facilities as emissions per ton of zinc product. Emission factors for mercury from zinc smelting pross ranged from 4.32 to 12.96 mg/ton with an average of 8.31 mg/ton. The emission factors that we obtained in this study are relatively low, considering Hg contents in the zinc ores and control technology in use. However, as these values are estimated by limited data of single measurement of each, the emission factor and total emission amount must be updated in future.

Circumpolar measurements of speciated mercury, ozone and carbon monoxide in the boundary layer of the Arctic Ocean

Abstract. Using the Swedish icebreaker Oden as a platform, continuous measurements of airborne mercury (gaseous elemental mercury (Hg0), divalent gaseous mercury species HgIIX2(g) (acronym RGM) and mercury attached to particles (PHg)) and some long-lived trace gases (carbon monoxide CO and ozone O3) were performed over the North Atlantic and the Arctic Ocean. The measurements were performed for nearly three months (July–September 2005) during the Beringia 2005 expedition (from Göteborg, Sweden via the proper Northwest Passage to the Beringia region Alaska – Chukchi Penninsula – Wrangel Island and in-turn via a north-polar transect to Longyearbyen, Spitsbergen). The Beringia 2005 expedition was the first time that these species have been measured during summer over the Arctic Ocean going from 60° to 90° N. During the North Atlantic transect, concentration levels of Hg0, CO and O3 were measured comparable to typical levels for the ambient mid-hemispheric average. However, a rapid increase of Hg0 in air and surface water was observed when entering the ice-covered waters of the Canadian Arctic archipelago. Large parts of the measured waters were supersaturated with respect to Hg0, reflecting a strong disequilibrium. Heading through the sea ice of the Arctic Ocean, a fraction of the strong Hg0 pulse in the water was transferred with some time-delay into the air samples collected ~20 m above sea level. Several episodes of elevated Hg0 in air were encountered along the sea ice route with higher mean concentration (1.81±0.43 ng m−3) compared to the marine boundary layer over ice-free Arctic oceanic waters (1.55±0.21 ng m−3). In addition, the bulk of the variance in the temporal series of Hg0 concentrations was observed during July. The Oden Hg0 observations compare in this aspect very favourably with those at the coastal station Alert. Atmospheric boundary layer O3 mixing ratios decreased when initially sailing northward. In the Arctic, an O3 minimum around 15–20 ppbV was observed during summer (July–August). Alongside the polar transect during the beginning of autumn, a steady trend of increasing O3 mixing ratios was measured returning to initial levels of the expedition (&gt;30 ppbV). Ambient CO was fairly stable (84±12 ppbV) during the expedition. However, from the Beaufort Sea and moving onwards steadily increasing CO mixing ratios were observed (0.3 ppbV day−1). On a comparison with coeval archived CO and O3 data from the Arctic coastal strip monitoring sites Barrow and Alert, the observations from Oden indicate these species to be homogeneously distributed over the Arctic Ocean. Neither correlated low ozone and Hg0 events nor elevated concentrations of RGM and PHg were at any extent sampled, suggesting that atmospheric mercury deposition to the Arctic basin is low during the Polar summer and autumn.

Observations of speciated atmospheric mercury at three sites in Nevada: Evidence for a free tropospheric source of reactive gaseous mercury

Air mercury (Hg) speciation was measured for 11 weeks (June–August 2007) at three sites simultaneously in Nevada, USA. Mean reactive gaseous Hg (RGM) concentrations were elevated at all sites relative to those reported for locations not directly influenced by known point sources. RGM concentrations at all sites displayed a regular diel pattern and were positively correlated with ozone (O3) and negatively correlated with elemental Hg (Hg0) and dew point temperature (Tdp). Superimposed on the diel changes were 2‐ to 7‐day periods when RGM concentrations increased across all three sites, producing significant intersite correlations of RGM daily means (r = 0.53–0.76, p &lt; 0.0001). During these periods, enhanced O3 concentrations and lower Tdp were also observed. Back trajectories were applied to develop gridded frequency distribution (GFD) plots and determine trajectory residence times (TRT) in specific source boxes. The GFD for the upper‐quartile RGM daily means at one site showed a contributing airflow regime from the high‐altitude subtropics with little precipitation, while that developed for the lower‐quartile RGM concentrations indicated predominantly lower‐altitude westerly flow and precipitation. Daily mean TRT in a subtropical high‐altitude source box (&gt;2 km and &lt;35°N) explained a component of the daily mean RGM at two sites (r2 = 0.37 and 0.27, p &lt; 0.05). These observations indicate that long‐range transport of RGM from the free troposphere is a potentially important component of Hg input to rural areas of the western United States.

Atmospheric mercury concentrations and speciation measured from 2004 to 2007 in Reno, Nevada, USA

Atmospheric elemental, reactive and particulate mercury (Hg) concentrations were measured north of downtown Reno, Nevada, USA from November 2004 to November 2007. Three-year mean and median concentrations for gaseous elemental Hg (Hg 0) were 1.6 and 1.5 ng m −3 (respectively), similar to global mean Hg 0 concentrations. The three-year mean reactive gaseous Hg (RGM) concentration (26 pg m −3) was higher than values reported for rural sites across the western United States. Well defined seasonal and daily patterns in Hg 0 and RGM concentrations were observed, with the highest Hg 0 concentrations measured in winter and early morning, and RGM concentrations being greatest in the summer and mid-afternoon. Elevated Hg 0 concentrations in winter were associated with periods of cold, stagnant air; while a regularly observed early morning increase in concentration was due to local source and surface emissions. The observed afternoon increase and high summer values of RGM can be explained by in situ oxidation of gaseous Hg 0 or mixing of RGM derived from the free troposphere to the surface. Because both of these processes are correlated with the same environmental conditions it is difficult to assess their overall contribution to the observed trends.

Atmospheric Mercury (Hg) in the Adirondacks: Concentrations and Sources

Hourly averaged gaseous elemental Hg (GEM) concentrations and hourly integrated reactive gaseous Hg (RGM), and particulate Hg (Hg(p)) concentrations in the ambient air were measured at Huntington Forest in the Adirondacks, New York from June 2006 to May 2007. The average concentrations of GEM, RGM, and Hg(p) were 1.4 +/- 0.4 ng m(-3), 1.8 +/- 2.2 pg m(-3), and 3.2 +/- 3.7 pg m(-3), respectively. RGM represents < 3.5% of total atmospheric Hg or total gaseous Hg (TGM: GEM + RGM) and Hg(p) represents < 3.0% of the total atmospheric Hg. The highest mean concentrations of GEM, RGM, and Hg(p) were measured during winter and summer whereas the lowest mean concentrations were measured during spring and fall. Significant diurnal patterns were apparent in warm seasons for all species whereas diurnal patterns were weak in cold seasons. RGM was better correlated with ozone concentration and temperature in both warm (rho (RGM - ozone) = 0.57, p < 0.001; rho (RGM - temperature) = 0.62, p < 0.001) and cold seasons (rho (RGM - ozone) = 0.48, p = 0.002; rho (RGM - temperature) = 0.54, p = 0.011) than the other species. Potential source contribution function (PSCF) analysis was applied to identify possible Hg sources. This method identified areas in Pennsylvania, West Virginia, Ohio, Kentucky, Texas, Indiana, and Missouri, which coincided well with sources reported in a 2002 U.S. mercury emissions inventory.

Characterization and cycling of atmospheric mercury along the central US Gulf Coast

Abstract Concentrations of atmospheric Hg species, elemental Hg (Hg ∘ ), reactive gaseous Hg (RGM), and fine particulate Hg (Hg-PM 2.5 ) were measured at a coastal site near Weeks Bay, Alabama from April to August, 2005 and January to May, 2006. Mean concentrations of the species were 1.6 ± 0.3 ng m −3 , 4.0 ± 7.5 pg m −3 and 2.7 ± 3.4 pg m −3 , respectively. A strong diel pattern was observed for RGM (midday maximum concentrations were up to 92.7 pg m −3 ), but not for Hg ∘ or Hg-PM 2.5 . Elevated RGM concentrations (>25 pg m −3 ) in April and May of 2005 correlated with elevated average daytime O 3 concentrations (>55 ppbv) and high light intensity (>500 W m −2 ). These conditions generally corresponded with mixed continental-Gulf and exclusively continental air mass trajectories. Generally lower, but still elevated, RGM peaks observed in August, 2005 and January–March, 2006 correlated significantly ( p 2 concentration and corresponded to periods of high light intensity and lower average daytime O 3 concentrations. During these times air masses were dominated by trajectories that originated over the continent. Elevated RGM concentrations likely resulted from photochemical oxidation of Hg ∘ by atmospheric oxidants. This process may have been enhanced in and by the near-shore environment relative to inland sites. The marine boundary layer itself was not found to be a significant source of RGM. Size segregation determination, using a limited dataset from two different methods, suggested that a significant fraction of particulate Hg was bound to coarse particles (>2.5 μm). A potential source of the large fraction of coarse particulate Hg in the study area is sequestration of RGM within sea salt aerosols. The presence of rapidly depositing RGM and coarse particulate Hg may be important sources of Hg input along the Gulf Coast. However, the impact of these species on deposition rates is yet to be determined.

Atmospheric mercury at mediterranean coastal stations

Mercury in air has been measured at five coastal Mediterranean sites, involving measurements in Spain, France, Italy, Slovenia and Israel. Four two-weeks long measure- ments campaigns were performed at the five sites. The measurements were carried out during autumn 2003 and winter, spring and summer 2004. Total gaseous mercury/elemental gaseous mercury, particulate mercury and divalent gaseous mercury were measured in parallel at the five sites. The activities constituted a subtask of the EU funded MERCYMS research project, which also included Mediterranean Sea cruises where both mercury in air and water were measured. The result from an evaluation of all the coastal air data is presented. Mercury concentrations from the different sites are compared with similar data obtained in northern Europe and elsewhere. The result shows that the background concentration of mercury in Mediterranean coastal air is lower than earlier anticipated. Background concentrations of TGM, RGM and TPM corresponded to 1.75-1.80 ng m −3 , 1-13 and 3-23 pg m −3 , respec- tively. The measurements also showed that the mercury concentration occasionally can be

Local and regional factors affecting atmospheric mercury speciation at a remote location

Atmospheric concentrations of elemental (Hg0), reactive gaseous (RGM), and particulate (PHg) mercury were measured at two remote sites in the midwestern United States. Concurrent measurements of Hg0, PHg, and RGM obtained at Devil’s Lake and Mt. Horeb, located approximately 65 km apart, showed that Hg0 and PHg concentrations were affected by regional, as well as local sources, while RGM was mainly impacted by local sources. Plumes reaching the Devil’s Lake site from a nearby coal-fired power plant significantly impacted SO2 and RGM concentrations at Devil’s Lake, but had little impact on Hg0. Our findings suggest that traditional modeling approaches to assess sources of mercury deposited that utilize source emissions and large-scale grids may not be sufficient to predict mercury deposition at sensitive locations due to the importance of small-scale sources and processes. We suggest the use of a receptor-based monitoring to better understand mercury source–receptor relationships.

Rapid Reduction and Reemission of Mercury Deposited into Snowpacks during Atmospheric Mercury Depletion Events at Churchill, Manitoba, Canada

Mercury (Hg) in some Arctic marine mammals has increased to levels that may be toxic to Northern peoples consuming them as traditional food. It has been suggested that sunlight-induced atmospheric reactions called springtime atmospheric Hg depletion events (AMDEs) result in the loading of -150-300 tons of Hg to the Canadian Arctic archipelago each spring and that AMDEs are the ultimate source of Hg to Arctic foodwebs. AMDEs result from the oxidation of gaseous elemental Hg0 (GEM) in Arctic atmospheres to reactive gaseous Hg (RGM) and particulate Hg (pHg), both of which fall out of the atmosphere to snowpacks. We studied the springtime cycling of Hg between air and snowpacks near Churchill, Manitoba, for 2 years to determine the net input of Hg to Hudson Bay from AMDEs. In 2004, we monitored atmospheric concentrations of GEM, pHg, and RGM while simultaneously measuring concentrations of total Hg (THg) in surface snow collected over the sea ice on Hudson Bay. During numerous springtime AMDEs, concentrations of THg in surface snow increased, often to over 60 ng/L, demonstrating that AMDEs resulted in deposition of oxidized Hg (Hg(II)) to snowpacks. However, immediatelyfollowing AMDEs, average concentrations of THg in snow declined drastically from between 67.8+/-7.7 ng/L during AMDEs to only 4.25+/-1.85 ng/L four or more days following them. In 2003, we measured THg in surface snow collected daily over the sea ice and total gaseous Hg (TGM) concentrations in the interstitial airspaces of snowpacks. When concentrations of THg in the surface snow decreased, concentrations of TGM in interstitial airspaces of the snowpack increased sharply from between approximately 1.4-3.4 ng/m(3) to between approximately 20-150 ng/m(3), suggesting thatthere was a reduction of deposited Hg(II) to GEM, which then diffused out of snowpacks. At snowmelt in both 2003 and 2004, average concentrations of THg in meltwater collected over Hudson Bay were only 4.04+/-2.01 ng/L. Using concentrations of THg in meltwater and snow water equivalent, we estimated a net springtime loading of only 2.1+/-1.7 mg/ha of Hg to Hudson Bay from AMDEs, indicating that only a small portion of the Hg(II) deposited during AMDEs enters Hudosn Bay each spring.

Atmospheric mercury speciation in Yellowstone National Park

Atmospheric concentrations of elemental mercury (Hg0), reactive gaseous Hg (RGM), and particulate Hg (pHg) concentrations were measured in Yellowstone National Park (YNP), U.S.A. using high resolution, real time atmospheric mercury analyzers (Tekran 2537A, 1130, and 1135). A survey of Hg0 concentrations at various locations within YNP showed that concentrations generally reflect global background concentrations of 1.5–2.0 ng m−3, but a few specific locations associated with concentrated geothermal activity showed distinctly elevated Hg0 concentrations (about 9.0 ng m−3). At the site of intensive study located centrally in YNP (Canyon Village), Hg0 concentrations did not exceed 2.5 ng m−3; concentrations of RGM were generally below detection limits of 0.88 pg m−3 and never exceeded 5 pg m−3. Concentrations of pHg ranged from below detection limits to close to 30 pg m−3. RGM and pHg concentrations were not correlated with any criteria gases (SO2, NOx, O3); however pHg was weakly correlated with the concentration of atmospheric particles. We investigated three likely sources of Hg at the intensive monitoring site: numerous geothermal features scattered throughout YNP, re-suspended soils, and wildfires near or in YNP. We examined relationships between the chemical properties of aerosols (as measured using real time, single particle mass spectrometry; aerosol time-of-flight mass spectrometer; ATOFMS) and concentrations of atmospheric pHg. Based on the presence of particles with distinct chemical signatures of the wildfires, and the absence of signatures associated with the other sources, we concluded that wildfires in the park were the main source of aerosols and associated pHg to our sampling site.

Automated Speciated Mercury Measurements in Michigan

Automated speciated mercury measurements were made at a rural (Dexter, MI) and an urban (Detroit, MI) site in Michigan during selected times from 1999 to 2002 to assess the concentrations of elemental (Hg0), reactive gaseous (RGM), and particulate mercury (Hgp) in these environments. Here we present the first-ever reported values for RGM in Michigan. Median RGM concentrations were 2.21-2.93 pg m(-3) at Dexter and were 3-11 times higher in Detroit at 6.41-22.0 pg m(-3). Maximum RGM concentrations of 38.7 pg m(-3) and 270 pg m(-3) were observed in Dexter and Detroit, respectively. Measured RGM/Hg0 ratios were in the range of 0.04-11.60% indicating that at times RGM comprises greater than the currently held view of 5% of total gaseous mercury in the air. Well-pronounced diurnal patterns of RGM were observed at the rural site, whereas the urban site exhibited patterns that were influenced by nighttime emissions and regional transport. An analysis of RGM/Hgp ratios at the urban site when combined with trajectory analysis suggests that the site receives mercury inputs from both local and regional sources. Episodes of elevated ozone concentrations which were accompanied by increases in RGM concentrations were observed to occur in the late afternoon and overnight. These may be evidence of advection of ozone and RGM over long distances to the site.

Emissions, dispersion and human exposure of mercury from a Swedish chlor-alkali plant

Mercury in air near a mercury cell chlor-alkali plant in Sweden has been measured within the EU-project EMECAP. Based on the measurements and modelling the annual distributions of GEM and RGM have been calculated for the local area around the plant. The average concentration of GEM in residential areas near the plant was found to be 1–3.5 ng m −3 higher in comparison to the background concentration in this part of Sweden. The emission of RGM (0.55 kg year –1) results in elevated RGM concentrations close to the plant. The greatest impact on the local area is due to wet deposition of RGM. However, only a small fraction (0.4%) of all mercury being emitted was found to be deposited in the local area. No impact on urinary mercury could be demonstrated in the population living close to the plant.