1d: Mercury cycling, bioaccumulation and health impacts in polar regions

Assessment of Mercury in Antarctica is important for many reasons: a. Antarctica is a pristine remote place which governs the climate of the southern hemisphere, and b. it has been decided in Minamata convention to reduce the risk of mercury pollution through research and monitoring. India is signatory to Minamata convention. Assessment of signature of mercury in remote location is also useful to understand the pathway of transportation so control mechanism can be derived by decision makers. Here, we present results of mercury monitoring in two Indian Antarctic Stations in years 2012, 2014-15 and 2015-16.

Maitri station is situated in Schirmacher hills in East Antarctica, around 80 km from the coast-line on rocky terrain. Schirmacher Hills cover approximate 35 km2 area with an average width of three km. It remains almost ice-free during austral summer; however, blizzards occasionally cover the rocky terrain with snow. Bharati station is located around 2500 km away from Maitri station in East Antarctica in the Larsemann Hills area. We recorded the Total Gaseous Mercury (TGM) in the atmosphere in Maitri by installing Tekran 2537-B mercury analyser during austral summer of 2012 during XXXII- Indian Scientific Expedition to Antarctica (ISEA). Observed values of TGM were in the range of 1 to 3.5 ng/m3. However, higher concentrations were recorded soon after after blizzard when concentration reached to nearly 10 ng/m3. During XXXIV- ISEA in austral summer of 2014-15 another instrument ( Gardis-5) had been operated, near Bharati station for nearly 20 days and observed value sown the results in the Range of 1-to 2.5 ng/m3. Same instrument has been installed at Maitri station during austral summer of XXXV-ISEA (2015-16) and results recorded in the in range of 0.5 to 2 ng/m3.

Abrupt change in the concentration of the mercury soon after blizzard is a particular phenomenon that has to be further explored through experiments and observations. We will also present mercury concentrations in moss, water and snow samples from Maitri station to cover the complete biogeochemical occurrence of mercury in the area. These results can be used as baseline for future assessment of trends.

Exposure of current levels of Hg in the Arctic can have adverse impacts on human health, particularly for the development fetus and children (AMAP, 2011). Long-range transported atmospheric Hg from sources in Asia, Russia, Europe and North-America, is recognized as one of the main antropogenic sources of this toxic pollutant in the Arctic, and especially focus has been on the impact of Atmospheric Mercury Depletion Events (AMDEs) as a means of delivering Hg to the ecosystems for now almost 20 years (Schroeder et al., 1998; AMAP, 2011). Mercury exist in the atmosphere mainly as gaseous elemental mercury (GEM) which has an atmospheric residence time of 6 months to 1 year. During AMDEs GEM can through a series of photochemically initiated reactions be oxidized to a more shorter lived species which is called reactive gaseous mercury (RGM). RGM can either stay in the air or if there are particles available be attached to these, and reported as particulate mercury (PHg). RGM and PHg can be deposited within hours to weeks. In the following presentation of five years of atmospheric speciation data for mercury from the Zeppelin station, Ny-lesund is presented. Speciated mercury have beens measured by automated Tekran mercury instrumentation. RGM was measured with a speciation unit (Model 1130) consisting of a KCl coated denuders while PHg was sampled on a particulate filter (Model 1135). In trying to find out what variables are driving the variations in concentrations of gaseous elemetal mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (pHg) during the year at the Zeppelin station five year of mercury speciation data together with meteorology data, aerosol data, UV data as well as correlation analysis have been studied.

Atmospheric deposition is the main input of mercury (Hg) to the ocean, even in remote locations such as the Arctic. Furthermore, evasion of elemental Hg (Hg(0)) is the major sink for oceanic Hg, resulting in air-sea exchange being an important part of the oceanic Hg cycle. Many factors influence gas exchange, and prior studies have suggested that some locations are net sources of Hg to the atmosphere, while others are sinks. To examine air-sea exchange in the Arctic Ocean we made high resolution measurements of Hg(0) in surface waters and Hg speciation in the atmosphere during the US GEOTRACES cruise in 2015 using sampling systems which continuously sampled surface water and the atmosphere. Additionally, samples were obtained for measurement of Hg in precipitation and aerosols, and for Hg profiles in sea ice. We use the measurements in water and the atmosphere to estimate fluxes of Hg(0) from the ocean to the atmosphere (these being potential rates for locations under ice). Overall, concentrations of Hg(0) were near saturation in ice free waters (21±12 fM), and resultant fluxes low, but Hg(0) was highly enriched under contiguous ice (120±101 fM, up to 450 fM), suggesting the continual formation of Hg(0) in waters even when ice covered. Predicted peaks in Hg(0) evasion, blocked by the sea ice barrier, were as high as 270 pmol/m^2/h. We compare our estimates of Hg(0) evasion with those of others and with models, and use these data, our measurements of atmospheric and ice concentrations, and the results of others to estimate potential deposition of Hg to the regions covered by the cruise. Based on these estimates, we can make predictions of the rate of response of the region to changes in ice cover and the potential impact of climate change on Hg dynamics and food web bioaccumulation in this important ocean region.

Due to climate change, the sea ice extents in the Arctic and in Antarctica are rapidly changing. Deposited atmospheric mercury onto surface snow and sea water that is not re-emitted back to air can enter the sea ice from the overlaying snow and/or the underlying seawater. Reported data on the concentration of total, elemental and methylated mercury species in polar sea ice is however scant.

Here we present concentrations of elemental mercury (Hg(0)) in various media in the Arctic and Antarctic sea ice environment. Samples of sea ice, snow, under ice water, brine, melt pond water, new ice and frost flowers were collected at 26 ice stations in the Eurasian and Amerasian Basins in the Arctic Ocean during the SWEDARCTIC 2016 campaign arranged by the Swedish Polar Research Secretariat (SPRS) aboard the IB Oden (8/8 – 20/9 2016). Corresponding samples were collected in Antarctica at 25 ice stations in the Weddell Sea aboard R/V Polarstern (ANTXXIX/6&7, June - October 2013) arranged by the Alfred Wegener Institute (AWI) and in the Amundsen and Ross’ Seas aboard IB Oden (OSO 10/11, SPRS, December – January 2010/2011).

The concentrations of Hg(0) in under ice water and in sea ice brine in the two polar regions were found to be comparable. However, the average concentrations of Hg(0) in sea ice were significantly higher in Antarctica (70 - 105 pg L-1) than in the Arctic (25 ± 10 pg L-1). The Hg(0) concentrations in the overlaying snow was also found to be considerably higher in Antarctica (250 - 730 pg L-1) than in the Arctic (10 ± 5 pg L-1), possibly due to spatial variations in atmospheric deposition and/or re-evasion.

A seasonal variation of the Hg(0) concentrations in the sea ice environment was found in Antarctica leading to the conclusion that factors such as solar radiation, temperature, brine volume and atmospheric deposition might be important for the transformation and transportation processes of mercury in sea ice in polar regions. The polar marine cryosphere, found to be a significant reservoir of mercury, is affecting the cycling of mercury in polar regions.Climate change and changing sea ice extent in the Arctic and Antarctica could lead to consequences for the global mercury budget.

The emperor penguin (Apenodytes forsteri) is unique in that they are the only species breeding on the fast sea ice during austral winter months. Given that sea ice conditions are deteriorating significantly due to climate change, emperor penguins have recently been listed as near threatened species by the IUCN (the International Union for Conservation of Nature). Additionally, emperor penguins are the deepest divers reaching up to 500 m, which allows them to forage in a relatively wide range of water column. Because Antarctica is no longer free from impacts of anthropogenic activities and diving seabirds (e.g., penguins) play an important role in transporting not only nutrients but also contaminants from the oceans, there have been many studies on accumulation of contaminants including mercury (Hg) in different penguin species. However, there is very little information on Hg accumulation in emperor penguins. To the best of our knowledge, this is the first study reporting both total mercury (THg) and MeHg in emperor penguins from Cape Washington in the western Ross Sea, Antarctica. Liver and muscle samples were obtained from a total of 24 chicks and 6 adult emperor penguins. Our results fell within the ranges of previously reported Hg levels in Antarctic and subantarctic seabirds including penguin species. Compared to the muscle, both THg and MeHg concentrations in the liver were significantly higher, indicating that Hg detoxification as protective mechanism occurred. We found significant correlations of THg and MeHg with selenium (Se) in the liver only, suggesting a potential role of Se in Hg detoxification. Additionally, average THg and MeHg in chick penguins appeared to be somewhat higher than adults, likely due to molting as one excretory pathway of Hg to feathers. Further studies are required to investigate Hg accumulation process in emperor penguins and its controlling factors.

Fish are an important source of essential micronutrients for many populations, and serve as a cultural staple in traditional food systems of subarctic First Nations communities in the Mackenzie Valley. However, mercury is a common environmental contaminant often found in traditional foods including fish, and can pose health risks. This study measured total mercury (HgT) and omega-3 fatty acid (n-3 FA) content in wild-harvested fish of the Northwest Territories, and designed a dose reconstruction model to estimate community profiles of mercury exposure and n-3 intake. In 2016, a multi-year contaminant biomonitoring study was conducted to investigate contaminant exposure among First Nations communities of the Mackenzie Valley region.

The aim of this work is to build a draft, probabilistic model that will help evaluate the risk-benefit balance associated with consumption of locally-harvested freshwater fish. To achieve this goal, this study evaluated HgT and n-3 levels in harvested fish, and defined probability distributions for the draft model using profiles for HgT and n-3 FAs in fish tissue.

Samples from eight fish species were harvested in lakes of the Mackenzie Valley from 2013-2015. HgT in fish tissue was measured using a Direct Mercury Analyzer, and FAs were measured by lipid extraction and analysis using a gas chromatograph. Weight and dietary intake data collected from the Contaminants Biomonitoring Study were incorporated into the model. Biomarkers for community exposure to mercury and n-3 FAs will be used to gauge model performance.

HgT concentrations in predatory fish, including Northern Pike (0.458ppm), Walleye (0.467ppm), and Lake Trout (0.224ppm) were up to 8.65-fold higher than levels observed in benthivorous and planktivorous fish species, such as Cisco (0.054ppm), and Lake Whitefish (0.094ppm). Lake Whitefish demonstrated n-3 FA levels (288.87 mg/100g) that were up to 3.06 times higher than in predatory fish. Interestingly, significant negative correlations were observed between mercury and nutrient content in particular fish species. Negative correlations were observed between HgT and n-3 FA content for Burbot, Northern Pike, and Walleye. These associations will be built into the probabilistic analysis to refine the models ability to generate estimates for contaminant exposure and nutrient intake.

This model will be used to inform public health organizations in the development of consumption advisories for Northern First Nations communities, with the goal of minimizing the risks from Hg exposure while promoting the nutritional benefits of fish in traditional food systems.

The toxicity of its methylated forms and its ability of dispersion through the atmosphere make mercury (Hg) of special concern in remote-pristine ecosystems, such as the Artic and Antarctica. We sampled a short sediment core in Limnopolar Lake (Livingston Island, South Shetland Islands), spanning the last ~1600 years. Sediments were sectioned at high resolution, 210Pb dated and analysed for total mercury, as well as mercury species by means of Hg-thermo desorption-CVAAS. The core shows sections of extreme mercury concentrations ranging between 1,141 and 11,286 ng g-1 compared to background concentrations between 13 and 155 ng g-1Hg-thermo-desorption analyses indicate that mercury is retained in the sediment by organic matter at different stages of degradation. To explain the large differences in concentrations and the extremely high values found, we proposed a combination of different natural processes such as volcanism, climate and Hg depletion events. The nearby (30 km) volcano at Deception Island appears to be the main source of mercury, while climatic conditions have controlled freezing and thawing of ice-cover and snowpacks on the surface of the lake and in the catchment, which likely caused event based fluxes of Hg to the lakes sediments. Moreoever, extreme mercury concentrations match with elevated Br/C ratios (a measure of bromine deposition independent of the organic matter), suggesting that atmospheric depletion events may have been involved in enhanced mercury atmospheric deposition. These also coincided with low Total Solar Irradiance (TSI) during known low insolation periods. No evidence of anthropogenic mercury pollution was found.

The global release of Hg to the environment has increased greatly as a result of human activities. Since Hg is subject to long-range atmospheric transport, its continued global use and emission poses risks to humans and ecosystems both at the point of use and in remote locations. Bjørnøya, a remote Norwegian island in the Barents Sea, is an ideal location for research on Hg transport to the Arctic, given the presence of lakes supporting Arctic char populations that can act as reference sites where inputs are limited to long-range atmospheric transport (e.g. Laksvatn and Øyangen), as well as sites with a high abundance of seabirds (e.g. Ellasjøen), which may act as a biological vector for transport and deposition of Hg.

This work aimed to combine contemporary data with existing historical data and analysis of an extensive collection of archival fish samples in order to assess long-term changes in Hg contamination on Bjørnøya.

Briefly, we carried out Hg analysis on archival frozen muscle tissue samples from Arctic char collected from Bjørnøya over the past two decades. The sample set consisted of more than 500 char collected from 3 lakes (Ellasjøen, Laksvatn, Øyangen) over an 18-year period. We found that length-adjusted Hg concentrations were significantly higher in Ellasjøen than in either Laksvatn or Øyangen, likely reflecting elevated Hg inputs to Ellasjøen from seabirds, similar to what has previously been observed for PCBs. Hg concentrations in char from all lakes exhibited considerable interannual variability. For Ellasjøen, we observed a statistically significant increase (P<0.00001) in length-adjusted Hg concentrations of approximately 1.6 % per year. We also took a generalized additive modelling (GAM) approach in order to explore several key drivers of Hg concentrations in fish from Ellasjøen (n=218 fish), including collection year, length, age and condition factor. Using a GAM, we were able to explain approximately 80% of the deviance in fish Hg concentrations for Ellasjøen, with increasing Hg over time, a bimodal relationship between length and Hg (due to the inclusion of two char morphotypes in the sample set), a positive relationship with age, and a negative relationship with condition factor. We also explore potential drivers of the interannual variability and long-term increase in fish Hg in Ellasjøen by comparing our results with paleolimnological records of Hg in Ellasjøen, and long-term data on climate and seabird population size on Bjørnøya.

Mercury deposition and re-emission from surface snow in the polar regions is an important part of the global mercury cycle. Mercury can be deposited during the polar winter and accumulate in the snow pack. During spring time the increasing solar radiation as well as the increase in oxidant species in the atmosphere can interact with the mercury present in the surface snow and increase emission of gas phase mercury from the surface. Dommergue et al. in 2014 suggested that atmospheric mercury above the Antarctic Plateau (Total gaseous mercury TGM) can undergo to a daily concentration cycle. Two 72 hours experiments were carried out in the proximity of Ny-Alesund research station, Svalbard. The two experiments were performed to evaluate the changes in concentration of Hg and other possible reactive elements in surface snow. The first experiment was conducted between the 27th and the 1st of May 2015 under 24h Sun irradiation conditions and the second was between the 7th and the 10th of April 2016 when a day and night cycle still occurred. The experiment was performed with high temporal resolution to investigate the possible changes in Hg, Br, major ions include nitrate, ammonia and I and trace elements. Surfaces samples have been collected every hour for 3 consecutive days, aimed at the study of the effect of solar radiation, snow events, deposition and meteorological conditions on surface snow chemical composition and evolution.

The results obtained were integrated with the meteorological data collected by the Amundsen-Nobile Climate Change Tower and compared with the TGM measured as part of the EMEP program at the Mt. Zeppelin Observatory in Ny-Alesund. The results show two different trends. During the period with continuous solar presence, no diurnal variations in surface snow were detected for Hg and other elements that can undergo photochemical processes. For the experiment conducted during the day and night cycle, Hg and I showed appreciable diurnal cycles with maximum concentrations during the night and lower concentrations during the daytime. During the 24h solar presence experiment, the surface snow mercury did not show any correlation with atmospheric mercury while with a cycle of light and dark conditions we detect a negative correlation between the two measurements. In both experiments snow deposition events occurred during the surface snow sampling. In both cases the Hg concentration in the snow increase markedly suggesting a primary role of snow deposition as a mercury scavenger from the atmosphere.

The remote Antarctic plateau receives significant inputs of mercury because this element is subject to long-range atmospheric transport and is readily cycled between surfaces and the atmosphere. Previous observational studies over the plateau have shown distinct diurnal and seasonal variations of mercury in near surface air, suggesting that a photochemically driven mercury cycle may occur at the air-snow interface. However, the controlling processes have not yet been well understood and quantified. In this study, we build a one-dimensional chemical and transport model and use it to simulate the mercury cycles over the year of 2013 at the inland French-Italian Concordia Research Station, in order to quantitatively explore the most important processes contributing to the mercury variabilities. The major chemical/physical processes in our model include the oxidation of gaseous elemental mercury (Hg0) by different oxidants (i.e. bromine, OH and ozone), the deposition of Hg0 and oxidized mercury (HgII) onto snow, the photo-reduction of HgII to Hg0 in surface snow, the reemission of Hg0 back into the atmosphere, and the exchange of boundary layer mercury with its free tropospheric pool. The transport is driven by vertical diffusion coefficients from a regional climate model which has been validated against meteorological observations at this station. Our model is constrained by in situ measurements of Hg0 and other chemical tracers at Dome Concordia in 2013. We find during the sunlit period that a bromine-initiated scheme oxidizes Hg0 quickly, favored by low temperature and high levels of nitrogen oxides. Sensitivity simulations suggest that the rate constant of Hg0 + Br and/or the mixing ratio of Br should be close to the upper uncertainty bound in order to match the observation. The recycling time for mercury in the surface snowpack is roughly one week but highly uncertain. During the austral winter, mercury levels in the shallow boundary layer are dominated by the exchange with the free troposphere. Our model simulations also reveal several specific research needs in order to obtain a better understanding of mercury cycling over the Antarctic plateau and other polar regions.

Glaciers, particularly alpine glaciers, have been receding globally at an accelerated rate in recent decades. The glacial melt-induced release of pollutants (e.g., mercury) and its potential impact on the atmosphere and glacier-fed ecosystems has drawn increasing concerns. During 15th to 20th August, 2011, an intensive sampling campaign was conducted in Qugaqie Basin (QB), a typical high mountain glacierized catchment in the inland Tibetan Plateau, to investigate the export and transport of mercury from glacier to runoff. The total mercury (THg) level in Zhadang (ZD) glacier ranged from < 1 to 20.8 ng L-1, and was slightly higher than levels measured in glacier melt water and the glacier-fed river. Particulate Hg (PHg) was the predominant form of Hg in all sampled environmental matrices. Mercury concentration in Qugaqie River (QR) was characterized by a clear diurnal variation which is linked to glacier melt. The estimated annual Hg exports by ZD glacier, the upper river basin and the entire QB were 8.76, 7.3 and 157.85 g, respectively, with respective yields of 4.61, 0.99 and 2.74 μg m-2 yr-1. Unique landforms and significant gradients from the glacier terminus to QB estuary might promote weathering and erosion, thereby controlling the transport of total suspended particulates (TSP) and PHg. In comparison with other glacier-fed rivers, QB has a small Hg export yet remarkably high Hg yield, underlining the significant impact of melting alpine glaciers on regional Hg biogeochemical cycles. Such impacts are expected to be enhanced in high altitude regions under the changing climate.