Supporting Information Methylated Mercury Species In Canadian High Arctic Marine Surface Waters and Snowpacks (original) (raw)
Methylation of inorganic mercury in polar marine waters
Nature Geoscience, 2011
Monomethylmercury is a neurotoxin that accumulates in marine organisms, with serious implications for human health 1 . The toxin is of particular concern to northern Inuit peoples, for example, whose traditional diets are composed primarily of marine mammals and fish 2 . The ultimate source of monomethylmercury to marine organisms has remained uncertain, although various potential sources have been proposed, including export from coastal 3 and deep-sea 4 sediments and major river systems 5,6 , atmospheric deposition 7 and watercolumn production 8,9 . Here, we report results from incubation experiments in which we added isotopically labelled inorganic mercury and monomethylmercury to seawater samples collected from a range of sites in the Canadian Arctic Archipelago. Monomethylmercury formed from the methylation of inorganic mercury in all samples. Demethylation of monomethylmercury was also observed in water from all sites. We determined steady-state concentrations of monomethylmercury in marine waters by incorporating the rate constants for monomethylmercury formation and degradation derived from these experiments into a numerical model. We estimate that the conversion of inorganic mercury to monomethylmercury in the water column accounts for around 47% (±62%, standard deviation) of the monomethylmercury present in polar marine waters, with site-to-site differences in inorganic mercury and monomethylmercury levels accounting for most of the variability. We suggest that water-column methylation of inorganic mercury is a significant source of monomethylmercury in pelagic marine food webs in the Arctic, and possibly in the world's oceans in general.
THE FATE OF MERCURY IN ARCTIC TERRESTRIAL AND AQUATIC ECOSYSTEMS, A REVIEW
Environmental …, 2012
Environmental context. Mercury, in its methylated form, is a neurotoxin that biomagnifies in marine and terrestrial foodwebs leading to elevated levels in fish and fish-eating mammals worldwide, including at numerous Arctic locations. Elevated mercury concentrations in Arctic country foods present a significant exposure risk to Arctic people. We present a detailed review of the fate of mercury in Arctic terrestrial and marine ecosystems, taking into account the extreme seasonality of Arctic ecosystems and the unique processes associated with sea ice and Arctic hydrology.
Journal of Geophysical Research, 2007
Snow samples were collected in the seasonal snow cover of the low arctic tundra (Whapmagoostui-Kuujjuarapik, Que ´bec) during episodic atmospheric mercury depletion events (AMDEs) and in the snowmelt period, long after AMDEs had occurred. Total and methyl mercury analyses were done in order to investigate the critical factors influencing the fate of mercury once deposited in the snowpack. Following AMDEs, snow total mercury (THg) concentrations increased and were inversely proportional to the distance from Hudson Bay. The correlations between MeHg, sulfate (SO 4 2À ), and chlorine (Cl À ) snow concentrations implicated marine aerosols as a significant source of MeHg, independent of AMDEs. However, the newly deposited MeHg was unstable in the snow cover as 15-56% of the MeHg was demethylated or otherwise ''lost'' during the nighttime period. In contrast, during the snowmelt period, marine aerosols were not a significant source of MeHg. MeHg snow concentrations higher than 200 pg L À1 were observed when snow's heterotrophic plate counts, total suspended volatile solids, and total suspended solids were higher than 5.0 Â 10 5 CFU L À1 , 25 mg L À1 , and 90 mg L À1 , respectively. During the snowmelt, although the THg snow concentrations remained at 8-9 ng L À1 , the proportion of MeHg increased from 2.7 to 7.6%. This is the first report suggestive of the presence of mercury methylation activities within the snow cover of the low arctic tundra.
Environmental Chemistry, 2010
Environmental context. Mercury is a global contaminant that has entered Arctic food webs in sufficient quantity to put at risk the health of top predators and humans that consume them. Recent research has discovered a photochemical process unique to the Arctic that leads to mercury deposition on frozen surfaces after polar sunrise, but the connection between mercury deposition and entry into food webs remains tenuous and poorly understood. We propose here that the Arctic Ocean's sensitivity to the global mercury cycle depends far more on neglected post-deposition processes that lead to methylation within the ice-ocean system, and the vulnerability of these processes to changes occurring in the cryosphere.
Mercury in the sediments of freshwater lakes in Ny-Ålesund, Arctic
Environmental Monitoring and Assessment, 2020
Mercury and its speciation in aquatic ecosystems have been assessed globally. Even though previous studies were limited to Arctic freshwater lakes, they are highly significant in the context of the changing climate. The present study is based on sediment samples collected from three Arctic freshwater lakes over a period of 4 years (2015-2018). The samples were analysed for total mercury (THg), methyl mercury (MHg), and various mercury fractions. The observed mean THg and MHg concentrations were 22.23 ng/g and 0.41 ng/g respectively; these values were comparable with those for other Arctic freshwater lakes. The mercury content significantly varied among the years as well as among the lakes. Changes in snowdrift and meltwater inputs, which are the major sources of water for the lakes, may have influenced the sediment mercury content along with geographical location and increased productivity. The results of MHg indicated the susceptibility of lake sediments to methylation. The major fractions observed were the organo-chelated form of mercury, followed by the elemental and water-soluble forms. These results indicate the availability of mercury for methylation. Hence, it is necessary to conduct more studies on the influence of climate change, mercury release through permafrost melting, and atmospheric deposition.
Mercury in Arctic marine ecosystems: Sources, pathways and exposure
Environmental Research, 2012
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
Determination of mercury methylation potentials in the water column of lakes across Canada
Science of The Total Environment, 2006
A stable isotope technique was used to trace the formation of methylmercury in lake water incubation assays at in situ conditions in five lakes across Canada. Methylation activity was only detected in the anoxic hypolimnia of lakes. The stable isotope was methylated at varying rates between lakes and depths within lakes ranging from 0.56%/day to 14.8%/day. A peak in methylation potential was typically observed just below the oxycline, which decreased with increasing depth. The depth and rates of methylation potential changed seasonally with no methylation activity occurring after fall turnover. A decrease in the sulfate concentration was concomitant with the zone of mercury methylation potential indicating the likely involvement of sulfate reducing bacteria in the methylation process. A simple correlation test between DOC concentrations and methylation rates indicated a positive relationship (r 2 = 0.62; p = 0.006; n = 27). The demethylation rate constant in the anoxic hypolimnia was less than 0.12 d À 1 .