Diurnal cycles of gaseous mercury within the snowpack at Kuujjuarapik/Whapmagoostui, Québec, Canada

Mercury sources and physicochemical characteristics in ice, snow, and meltwater of the Laohugou Glacier Basin, China

In this work, samples of surface snow, surface ice, snow pit and meltwater from the Laohugou Glacier No. 12 on the northern edge of Tibetan Plateau (TP) were collected during the summer of 2015. The average concentration of Hg in surface snow/ice was 22.41 ng L^-1, while the percentage of dissolved mercury (Hg_D) was observed to be around 26%. An altitudinal magnification of Hg was not observed for surface snow; however, in contrast, a significant positive magnification of Hg with altitude was observed in the surface ice. A higher concentration of Hg corresponded with the dust layer of the snow pit. It was observed that about 42% of Hg was lost from the surface snow when the glacier was exposed to sunlight within the first 24 h indicating some Hg was emitted back to the atmosphere while some were percolated downwards. The result from the principal component analysis (PCA) showed that the sources of Hg in Laohugou Glacier No. 12 were from crustal and biomass burning. Finally, it was estimated that total export of Hg from the outlet river of Laohugou glacier No. 12 in the year 2015 was about 1439.46 g yr^-1 with yield of 22.77 μg m² yr^-1. This study provides valuable insights for understanding the behavior of Hg in the glacier of the northern Tibetan Plateau.

Hg in snow cover and snowmelt waters in high-sulfide tailing regions (Ursk tailing dump site, Kemerovo region, Russia)

Gold-bearing polymetallic Cu-Zn deposits of sulphur-pyrite ores were discovered in the Novo-Ursk region in the 1930s. The average content of mercury (Hg) was approximately 120 μg/g at the time. A comprehensive study of Hg distribution in waste of metal ore enrichment industry was carried out in the cold season on the tailing dump site and in adjacent areas. Mercury concentration in among snow particulate, dissolved and colloid fractions was determined. The maximal Hg content in particulate fraction from the waste tailing site ranged 230-573 μg/g. Such indices as the frequency of aerosol dust deposition events per units of time and area, enrichment factor and the total load allowed to establish that the territory of the tailing waste dump site had a snow cover highly contaminated with dust deposited at a rate of 247-480 mg/(m²∙day). Adjacent areas could be considered as area with low Hg contamination rate with average deposition rate of 30 mg/(m²∙day). The elemental composition of the aerosol dust depositions was determined as well, which allowed to reveal the extent of enrichment waste dispersion throughout adjacent areas. The amount of Hg entering environment with snowmelt water discharge was estimated. As a result of snowmelting, in 2014 the nearest to the dump site hydrographic network got Hg as 7.1 g with colloids and as 5880 g as particles. The results obtained allowed to assess the degree of Hg contamination of areas under the impact of metal enrichment industry.

Ratio of Methylmercury to Dissolved Organic Carbon in Water Explains Methylmercury Bioaccumulation Across a Latitudinal Gradient from North-Temperate to Arctic Lakes

We investigated monomethylmercury (MMHg) bioaccumulation in lakes across a 30° latitudinal gradient in eastern Canada to test the hypothesis that climate-related environmental conditions affect the sensitivity of Arctic lakes to atmospheric mercury contamination. Aquatic invertebrates (chironomid larvae, zooplankton) provided indicators of MMHg bioaccumulation near the base of benthic and planktonic food chains. In step with published data showing latitudinal declines in atmospheric mercury deposition in Canada, we observed lower total mercury concentrations in water and sediment of higher latitude lakes. Despite latitudinal declines of inorganic mercury exposure, MMHg bioaccumulation in aquatic invertebrates did not concomitantly decline. Arctic lakes with greater MMHg in aquatic invertebrates either had (1) higher water MMHg concentrations (reflecting ecosystem MMHg production) or (2) low water concentrations of MMHg, dissolved organic carbon (DOC), chlorophyll, and total nitrogen (reflecting lake sensitivity). The MMHg:DOC ratio of surface water was a strong predictor of lake sensitivity to mercury contamination. Bioaccumulation factors for biofilms and seston in Arctic lakes showed more efficient uptake of MMHg in low DOC systems. Environmental conditions associated with low biological production in Arctic lakes and their watersheds increased the sensitivity of lakes to MMHg.

Mercury in the Canadian Arctic terrestrial environment: an update

Contaminants in the Canadian Arctic have been studied over the last twenty years under the guidance of the Northern Contaminants Program. This paper provides the current state of knowledge on mercury (Hg) in the Canadian Arctic terrestrial environment. Snow, ice, and soils on land are key reservoirs for atmospheric deposition and can become sources of Hg through the melting of terrestrial ice and snow and via soil erosion. In the Canadian Arctic, new data have been collected for snow and ice that provide more information on the net accumulation and storage of Hg in the cryosphere. Concentrations of total Hg (THg) in terrestrial snow are highly variable but on average, relatively low (<5 ng L(-1)), and methylmercury (MeHg) levels in terrestrial snow are also generally low (<0.1 ng L(-1)). On average, THg concentrations in snow on Canadian Arctic glaciers are much lower than those reported on terrestrial lowlands or sea ice. Hg in snow may be affected by photochemical exchanges with the atmosphere mediated by marine aerosols and halogens, and by post-depositional redistribution within the snow pack. Regional accumulation rates of THg in Canadian Arctic glaciers varied little during the past century but show evidence of an increasing north-to-south gradient. Temporal trends of THg in glacier cores indicate an abrupt increase in the early 1990 s, possibly due to volcanic emissions, followed by more stable, but relatively elevated levels. Little information is available on Hg concentrations and processes in Arctic soils. Terrestrial Arctic wildlife typically have low levels of THg (<5 μg g(-1) dry weight) in their tissues, although caribou (Rangifer tarandus) can have higher Hg because they consume large amounts of lichen. THg concentrations in the Yukon's Porcupine caribou herd vary among years but there has been no significant increase or decrease over the last two decades.

Mercury in the marine environment of the Canadian Arctic: review of recent findings

This review summarizes data and information which have been generated on mercury (Hg) in the marine environment of the Canadian Arctic since the previous Canadian Arctic Contaminants Assessment Report (CACAR) was released in 2003. Much new information has been collected on Hg concentrations in marine water, snow and ice in the Canadian Arctic. The first measurements of methylation rates in Arctic seawater indicate that the water column is an important site for Hg methylation. Arctic marine waters were also found to be a substantial source of gaseous Hg to the atmosphere during the ice-free season. High Hg concentrations have been found in marine snow as a result of deposition following atmospheric mercury depletion events, although much of this Hg is photoreduced and re-emitted back to the atmosphere. The most extensive sampling of marine sediments in the Canadian Arctic was carried out in Hudson Bay where sediment total Hg (THg) concentrations were low compared with other marine regions in the circumpolar Arctic. Mass balance models have been developed to provide quantitative estimates of THg fluxes into and out of the Arctic Ocean and Hudson Bay. Several recent studies on Hg biomagnification have improved our understanding of trophic transfer of Hg through marine food webs. Over the past several decades, Hg concentrations have increased in some marine biota, while other populations showed no temporal change. Marine biota also exhibited considerable geographic variation in Hg concentrations with ringed seals, beluga and polar bears from the Beaufort Sea region having higher Hg concentrations compared with other parts of the Canadian Arctic. The drivers of these variable patterns of Hg bioaccumulation, both regionally and temporally, within the Canadian Arctic remain unclear. Further research is needed to identify the underlying processes including the interplay between biogeochemical and food web processes and climate change.

Mercury in Arctic snow: quantifying the kinetics of photochemical oxidation and reduction

Controlled experiments were performed with frozen and melted Arctic snow to quantify relationships between mercury photoreaction kinetics, ultra violet (UV) radiation intensity, and snow ion concentrations. Frozen (-10°C) and melted (4°C) snow samples from three Arctic sites were exposed to UV (280-400 nm) radiation (1.26-5.78 W · m(-2)), and a parabolic relationship was found between reduction rate constants in frozen and melted snow with increasing UV intensity. Total photoreduced mercury in frozen and melted snow increased linearly with greater UV intensity. Snow with the highest concentrations of chloride and iron had larger photoreduction and photooxidation rate constants, while also having the lowest Hg(0) production. Our results indicate that the amount of mercury photoreduction (loss from snow) is the highest at high UV radiation intensities, while the fastest rates of mercury photoreduction occurred at both low and high intensities. This suggests that, assuming all else is equal, earlier Arctic snow melt periods (when UV intensities are less intense) may result in less mercury loss to the atmosphere by photoreduction and flux, since less Hg(0) is photoproduced at lower UV intensities, thereby resulting in potentially greater mercury transport to aquatic systems with snowmelt.

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.

Gaseous elemental mercury (GEM) emissions from snow surfaces in northern New York

Snow surface-to-air exchange of gaseous elemental mercury (GEM) was measured using a modified Teflon fluorinated ethylene propylene (FEP) dynamic flux chamber (DFC) in a remote, open site in Potsdam, New York. Sampling was conducted during the winter months of 2011. The inlet and outlet of the DFC were coupled with a Tekran Model 2537A mercury (Hg) vapor analyzer using a Tekran Model 1110 two port synchronized sampler. The surface GEM flux ranged from -4.47 ng m(-2) hr(-1) to 9.89 ng m(-2) hr(-1). For most sample periods, daytime GEM flux was strongly correlated with solar radiation. The average nighttime GEM flux was slightly negative and was not well correlated with any of the measured meteorological variables. Preliminary, empirical models were developed to estimate GEM emissions from snow surfaces in northern New York. These models suggest that most, if not all, of the Hg deposited with and to snow is reemitted to the atmosphere.

Mercury in Arctic marine ecosystems: sources, pathways and exposure

Mercury in the Arctic is an important environmental and human health issue. The reliance of Northern Peoples on traditional foods, such as marine mammals, for subsistence means that they are particularly at risk from mercury exposure. The cycling of mercury in Arctic marine systems is reviewed here, with emphasis placed on the key sources, pathways and processes which regulate mercury levels in marine food webs and ultimately the exposure of human populations to this contaminant. While many knowledge gaps exist limiting our ability to make strong conclusions, it appears that the long-range transport of mercury from Asian emissions is an important source of atmospheric Hg to the Arctic and that mercury methylation resulting in monomethylmercury production (an organic form of mercury which is both toxic and bioaccumulated) in Arctic marine waters is the principal source of mercury incorporated into food webs. Mercury concentrations in biological organisms have increased since the onset of the industrial age and are controlled by a combination of abiotic factors (e.g., monomethylmercury supply), food web dynamics and structure, and animal behavior (e.g., habitat selection and feeding behavior). Finally, although some Northern Peoples have high mercury concentrations of mercury in their blood and hair, harvesting and consuming traditional foods have many nutritional, social, cultural and physical health benefits which must be considered in risk management and communication.

Mercury distribution and deposition in glacier snow over western China

Western China is home to the largest aggregate of glaciers outside the polar regions, yet little is known about how the glaciers in this area affect the transport and cycling of mercury (Hg) regionally and globally. From 2005 to 2010, extensive glacier snow sampling campaigns were carried out in 14 snowpits from 9 glaciers over western China, and the vertical distribution profiles of Hg were obtained. The Total Hg (THg) concentrations in the glacier snow ranged from <1 to 43.6 ng L(-1), and exhibited clear seasonal variations with lower values in summer than in winter. Spatially, higher THg concentrations were typically observed in glacier snows from the northern region where atmospheric particulate loading is comparably high. Glacier snowpit Hg was largely dependent on particulate matters and was associated with particulate Hg, which is less prone to postdepositional changes, thus providing a valuable record of atmospheric Hg deposition. Estimated atmospheric Hg depositional fluxes ranged from 0.74 to 7.89 μg m(-2) yr(-1), agreeing very well with the global natural values, but are one to two orders of magnitude lower than that of the neighboring East Asia. Elevated Hg concentrations were observed in refrozen ice layers in several snowpits subjected to intense melt, indicating that Hg can be potentially released to meltwater.

A synthesis of rates and controls on elemental mercury evasion in the Great Lakes Basin

Rates of surface-air elemental mercury (Hg(0)) fluxes in the literature were synthesized for the Great Lakes Basin (GLB). For the majority of surfaces, fluxes were net positive (evasion). Digital land-cover data were combined with representative evasion rates and used to estimate annual Hg(0) evasion for the GLB (7.7 Mg/yr). This value is less than our estimate of total Hg deposition to the area (15.9 Mg/yr), suggesting the GLB is a net sink for atmospheric Hg. The greatest contributors to annual evasion for the basin are agricultural (∼55%) and forest (∼25%) land cover types, and the open water of the Great Lakes (∼15%). Areal evasion rates were similar across most land cover types (range: 7.0-21.0 μg/m(2)-yr), with higher rates associated with urban (12.6 μg/m(2)-yr) and agricultural (21.0 μg/m(2)-yr) lands. Uncertainty in these estimates could be partially remedied through a unified methodological approach to estimating Hg(0) fluxes.

Total mercury and methylmercury in high altitude surface snow from the French Alps

Surface snow samples were collected weekly from the 31st of December 2008 to the 21st of June 2009 from Lake Bramant in the French Alps. Total mercury (THg), total dissolved mercury (THgD), methylmercury (MeHg) and particle distributions in surface snow were analyzed. Results showed that THg concentrations, MeHg concentrations and particle load increased with snow surface temperature, which is an indicator of rising temperatures as the season progresses. Significant correlations between MeHg and snow surface temperature and MeHg and total particles greater than 10 μm were observed. This suggests that the MeHg found in the snow originates from atmospheric deposition processes rather than in situ snowpack sources. This study suggests that an important post-winter atmospheric deposition of MeHg and THg occurs on summital zones of the French Alps and it is likely that this contamination originates from the surrounding valleys.

Diversity and characterization of mercury-resistant bacteria in snow, freshwater and sea-ice brine from the High Arctic

It is well-established that atmospheric deposition transports mercury from lower latitudes to the Arctic. The role of bacteria in the dynamics of the deposited mercury, however, is unknown. We characterized mercury-resistant bacteria from High Arctic snow, freshwater and sea-ice brine. Bacterial densities were 9.4 × 10(5), 5 × 10(5) and 0.9-3.1 × 10(3) cells mL(-1) in freshwater, brine and snow, respectively. Highest cultivability was observed in snow (11.9%), followed by freshwater (0.3%) and brine (0.03%). In snow, the mercury-resistant bacteria accounted for up to 31% of the culturable bacteria, but <2% in freshwater and brine. The resistant bacteria belonged to the Alpha-, Beta- and Gammaproteobacteria, Firmicutes, Actinobacteria, and Bacteriodetes. Resistance levels of most isolates were not temperature dependent. Of the resistant isolates, 25% reduced Hg(II) to Hg(0). No relation between resistance level, ability to reduce Hg(II) and phylogenetic group was observed. An estimation of the potential bacterial reduction of Hg(II) in snow suggested that it was important in the deeper snow layers where light attenuation inhibited photoreduction. Thus, by reducing Hg(II) to Hg(0), mercury-resistant bacteria may limit the supply of substrate for methylation processes and, hence, contribute to lowering the risk that methylmercury is being incorporated into the Arctic food chains.

The design and field implementation of the Detroit Exposure and Aerosol Research Study

The US Environmental Protection Agency recently conducted the Detroit Exposure and Aerosol Research Study (DEARS). The study began in 2004 and involved community, residential, and personal-based measurements of air pollutants targeting 120 participants and their residences. The primary goal of the study was to evaluate and describe the relationship between air toxics, particulate matter (PM), PM constituents, and PM from specific sources measured at a central site monitor with those from the residential and personal locations. The impact of regional, local (point and mobile), and personal sources on pollutant concentrations and the role of physical and human factors that might influence these concentrations were investigated. A combination of active and passive sampling methodologies were employed in the collection of PM mass, criteria gases, semivolatile organics, and volatile organic compound air pollutants among others. Monitoring was conducted in six selected neighborhoods along with one community site using a repeated measure design. Households from each of the selected communities were monitored for 5 consecutive days in the winter and again in the summer. Household, participant and a variety of other surveys were utilized to better understand human and household factors that might affect the impact of ambient-based pollution sources upon personal and residential locations. A randomized recruitment strategy was successful in enrolling nearly 140 participants over the course of the study. Over 36,000 daily-based environmental data points or records were ultimately collected. This paper fully describes the design of the DEARS and the approach used to implement this field monitoring study and reports select preliminary findings.

Critical review of mercury fates and contamination in the Arctic tundra ecosystem

Mercury (Hg) contamination in tundra region has raised substantial concerns, especially since the first report of atmospheric mercury depletion events (AMDEs) in the Polar Regions. During the past decade, steady progress has been made in the research of Hg cycling in the Polar Regions. This has generated a unique opportunity to survey the whole Arctic in respect to Hg issue and to find out new discoveries. However, there are still considerable knowledge gaps and debates on the fate of Hg in the Arctic and Antarctica, especially regarding the importance and significance of AMDEs vs. net Hg loadings and other processes that burden Hg in the Arctic. Some studies argued that climate warming since the last century has exerted profound effects on the limnology of High Arctic lakes, including substantial increases in autochthonous primary productivity which increased in sedimentary Hg, whereas some others pointed out the importance of the formation and postdeposition crystallographic history of the snow and ice crystals in determining the fate and concentration of mercury in the cryosphere in addition to AMDEs. Is mercury re-emitted back to the atmosphere after AMDEs? Is Hg methylation effective in the Arctic tundra? Where the sources of MeHg are? What is its fate? Is this stimulated by human made? This paper presents a critical review about the fate of Hg in the Arctic tundra, such as pathways and process of Hg delivery into the Arctic ecosystem; Hg concentrations in freshwater and marine ecosystems; Hg concentrations in terrestrial biota; trophic transfer of Hg and bioaccumulation of Hg through food chain. This critical review of mercury fates and contamination in the Arctic tundra ecosystem is assessing the impacts and potential risks of Hg contamination on the health of Arctic people and the global northern environment by highlighting and "perspectiving" the various mercury processes and concentrations found in the Arctic tundra.

Biological and chemical redox transformations of mercury in fresh and salt waters of the high arctic during spring and summer

It is well-established that atmospheric deposition transports Hg to Arctic regions, but the postdepositional dynamics of Hg that can alter its impact on Arctic food chains are less understood. Through a series of in situ experiments, we investigated the redox transformations of Hg in coastal and inland aquatic systems. During spring and summer, Hg reduction in streams and pond waters decreased across a 4-fold increase in salinity. This alteration of Hg reduction due to chloride was counterbalanced by the presence of particles, which favored the conversion of oxidized Hg to its elemental form. In saline waters, biogenic organic materials, produced by algae, were able to promote oxidation of Hg(O) even under dark conditions. Overall these results point to the vulnerability of marine/ coastal Arctic systems to Hg, compared to inland systems, with oxidation processes enhancing Hg residence times and thus increasing its potential to enter the food chain.

Laboratory simulation of Hg0 emissions from a snowpack

Snow surfaces play an important role in the biogeochemical cycle of mercury in high-latitude regions. Snowpacks act both as sources and sinks for gaseous compounds. Surprisingly, the roles of each environmental parameter that can govern the air-surface exchange over snow are not well understood owing to the lack of systematic studies. A laboratory system called the laboratory flux measurement system was used to study the emission of gaseous elemental mercury from a natural snowpack under controlled conditions. The first results from three snowpacks originating from alpine, urban and polar areas are presented. Consistent with observations in the field, we were able to reproduce gaseous mercury emissions and showed that they are mainly driven by solar radiation and especially UV-B radiation. From these laboratory experiments, we derived kinetic constants which show that divalent mercury can have a short natural lifetime of about 4-6 h in snow.

Mercury (micro)biogeochemistry in polar environments

The contamination of polar regions with mercury that is transported as inorganic mercury from lower latitudes has resulted in the accumulation of methylmercury in the food chain of polar environments, risking the health of humans and wildlife. This problem is likely to be particularly severe in coastal marine environments where active cycling occurs. Little is currently known about how mercury is methylated in polar environments. Relating observations on mercury deposition and transport through polar regions to knowledge of the microbiology of cold environments and considering the principles of mercury transformations as have been elucidated in temperate aquatic environments, we propose that in polar regions (1) variable pathways for mercury methylation may exist, (2) mercury bioavailability to microbial transformations may be enhanced, and (3) microbial niches within sea ice are sites where active microorganisms are localized in proximity to high concentrations of mercury. Thus, microbial transformations, and consequently mercury biogeochemistry, in the Arctic and Antarctic are both unique and common to these processes in lower latitudes, and understanding their dynamics is needed for the management of mercury-contaminated polar environments.

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.

A 2,000-year record of mercury and ancient civilizations in seal hairs from King George Island, West Antarctica

The concentrations of total mercury (Hg(T)) and three bio-essential elements (phosphor, potassium, sodium) were analyzed in Antarctic seal hairs from a lake core spanning the past 2,000 years and collected from King George Island (63 degrees 23'S, 57 degrees 00'W), West Antarctica. The Hg(T) concentration shows a significant fluctuation while the levels of the three bio-essential elements remain almost constant. The rise and fall of the Hg(T) concentration in the seal hairs are found to be closely coincided with ancient activities of gold and silver mining using Hg-amalgamation process around the world, especially in the Southern Hemisphere. Briefly, Hg(T) levels are high during five episodes of extensive gold and silver mining activities--Rome Empire and China Han Dynasty (approximately 18-300 A.D.), Maya period and China Tang (750-900 A.D.), Incas civilization and Christian Kingdom (1200-1500 A.D.), New world (1650-1800 A.D.), and modern industry period (1840 A.D.-present); they are low during four time periods of reduced gold and silver mining activities--the China Han and Rome fall (since 300 A.D.), Maya fall and Wartime period in China (1050-1250 A.D.), Pizarro coming (ca. 1532 A.D.) and Independence War of South America (1800-1830 A.D.). Two profiles of Hg(T) in other two lake cores, one affected by seal excrements and the other by penguin droppings, from the same region are similar to the one in seal hairs. The Hg concentration profile in the seal hairs is significantly correlated with the one in a peat bog of Southern Chile near King George Island. Since Hg is existent mainly at the form of methyl-mercury in seal hairs, this correlation supports a relationship and link between atmospheric mercury concentration and methyl-mercury production. Comparing with samples from American and European continents, the Antarctic seal hairs provide an archive of total mercury concentration in surface seawater of the South Ocean less affected by regional human activities, and this archive may provide a good reference for assessing the global Hg emissions, depositions and recycling in the past thousand years.

Some sources and sinks of monomethyl and inorganic mercury on Ellesmere Island in the Canadian High Arctic

We identified some of the sources and sinks of monomethyl mercury (MMHg) and inorganic mercury (HgII) on Ellesmere Island in the Canadian High Arctic. Atmospheric Hg depletion events resulted in the deposition of Hg(II) into the upper layers of snowpacks, where concentrations of total Hg (all forms of Hg) reached over 20 ng/L. However, our data suggest that much of this deposited Hg(II) was rapidly photoreduced to Hg(0) which then evaded back to the atmosphere. As a result, we estimate that net wet and dry deposition of Hg(II) during winter was lower at our sites (0.4-5.9 mg/ha) than wet deposition in more southerly locations in Canada and the United States. We also found quite high concentrations of monomethyl Hg (MMHg) in snowpacks (up to 0.28 ng/L), and at times, most of the Hg in snowpacks was present as MMHg. On the Prince of Wales Icefield nearthe North Water Polynya, we observed a significant correlation between concentrations of Cl and MMHg in snow deposited in the spring, suggesting a marine source of MMHg. We hypothesize that dimethyl Hg fluxes from the ocean to the atmosphere through polynyas and open leads in ice, and is rapidly photolyzed to MMHgCl. We also found that concentrations of MMHg in initial snowmelt on John Evans Glacier (up to 0.24 ng/L) were higher than concentrations of MMHg in the snowpack (up to 0.11 ng/L), likely due to either sublimation of snow or preferential leaching of MMHg from snow during the initial melt phase. This springtime pulse of MMHg to the High Arctic, in conjunction with climate warming and the thinning and melting of sea ice, may be partially responsible for the increase in concentrations of Hg observed in certain Arctic marine mammals in recent decades. Concentrations of MMHg in warm and shallow freshwater ponds on Ellesmere Island were also quite high (up to 3.0 ng/L), leading us to conclude that there are very active regions of microbial Hg(II) methylation in freshwater systems during the short summer season in the High Arctic.