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TitleChanges in Arctic mercury levels - Processes affecting Hg transformations and biotic uptake
AuthorNerentorp, M; Wang, F; Jonsson, S; Cairns, W R L; Chetelat, J; Lescord, G; Ukonmaanaho, L; Outridge, PORCID logo; St Pierre, K; Obrist, D; Douglas, T A; Zdanowicz, C; Bravo, A G
SourceAMAP 2021 Arctic Mercury Science Assessment; Nature Reviews Earth & Environment 2022 p. 1-17,
Alt SeriesNatural Resources Canada, Contribution Series 20200697
PublisherArctic Monitoring and Assessment Programme, Tromso, Norway
Mediapaper; on-line; digital
File formatpdf
Lat/Long WENS-180.0000 -1.0000 90.0000 60.0000
Subjectsmercury; mercury geochemistry; mineral deposits; glaciers; oceanography; Arctic Basin
Illustrationsschematic diagrams; location maps; distribution diagrams; tables
ProgramEnvironmental Geoscience Program Management
Released2022 03 22
AbstractAnthropogenic mercury (Hg) emissions have driven marked increases in Arctic Hg levels, which are now being impacted by regional warming, with uncertain ecological consequences. This Review presents a comprehensive assessment of the present-day total Hg mass balance in the Arctic. Over 98% of atmospheric Hg is emitted outside the region and is transported to the Arctic via long-range air and ocean transport. Around two thirds of this Hg is deposited in terrestrial ecosystems, where it predominantly accumulates in soils via vegetation uptake. Rivers and coastal erosion transfer about 80?Mg?year?1 of terrestrial Hg to the Arctic Ocean, in approximate balance with modelled net terrestrial Hg deposition in the region. The revised Arctic Ocean Hg mass balance suggests net atmospheric Hg deposition to the ocean and that Hg burial in inner-shelf sediments is underestimated (up to >100%), needing seasonal observations of sediment-ocean Hg exchange. Terrestrial Hg mobilization pathways from soils and the cryosphere (permafrost, ice, snow and glaciers) remain uncertain. Improved soil, snowpack and glacial Hg inventories, transfer mechanisms of riverine Hg releases under accelerated glacier and soil thaw, coupled atmosphere-terrestrial modelling and monitoring of Hg in sensitive ecosystems such as fjords can help to anticipate impacts on downstream Arctic ecosystems.
Summary(Plain Language Summary, not published)
Large amounts of Hg, primarily as gaseous elemental Hg, are transported to the Arctic environment annually via the atmosphere, while even larger amounts of inorganic Hg are brought into the Arctic Ocean via ocean currents and rivers. Globally significant amounts of mostly natural Hg are also stored within the Arctic in permafrost soils. These permafrost stocks of Hg are now at risk of being remobilized into the modern biogeochemical cycle as the Arctic warms and thaws. Thus, the majority of Hg in the Arctic environment exists in inorganic forms. A small fraction of the inorganic Hg is converted to monomethylmercury (MeHg) in ocean waters, coastal sediments, and wetland soils. After uptake of MeHg at the base of aquatic food webs, MeHg can biomagnify up food webs to concentrations of toxicological concern. The potential risk Hg pollution poses to Arctic ecosystems is thus not only controlled by the amounts of inorganic Hg transported into the system and cycling within the Arctic environment, but also to what extent the Hg pool is methylated and accumulated in aquatic food webs. In this chapter, key processes are described that link the Hg transported to, and mobilized within, the Arctic environment to the Hg accumulated in Arctic biota, including the wildlife important as northern wild foods. Processes covered include Hg methylation pathways, methylating genes, the role of organic matter in controlling the amounts of Hg methylated, Hg demethylation pathways, and the potential role of dimethylmercury in the Arctic Hg cycle. Uptake and subsequent biomagnification of MeHg in aquatic food webs is then described. Finally, a first-order mass balance estimate of MeHg in the Arctic environment is provided.

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