Journal
NATURE
Volume 547, Issue 7662, Pages 201-+Publisher
NATURE PUBLISHING GROUP
DOI: 10.1038/nature22997
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Funding
- US National Science Foundation (NSF) [PLR 1304305]
- NSF [CHN 1313755]
- US Department of Energy [DE-SC0014275]
- H2020 Marie Sklodowska-Curie grant [657195]
- European Research Council [ERC-2010-StG_20091028]
- CNRS-INSU-CAF (PARCS project)
- Marie Curie Actions (MSCA) [657195] Funding Source: Marie Curie Actions (MSCA)
- Directorate For Geosciences
- ICER [1313755] Funding Source: National Science Foundation
- Directorate For Geosciences
- Office of Polar Programs (OPP) [1739567] Funding Source: National Science Foundation
- Directorate For Geosciences
- Office of Polar Programs (OPP) [1304202] Funding Source: National Science Foundation
- U.S. Department of Energy (DOE) [DE-SC0014275] Funding Source: U.S. Department of Energy (DOE)
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Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic(1-6). It has been suggested that sea-salt-induced chemical cycling of Hg (through 'atmospheric mercury depletion events', or AMDEs) and wet deposition via precipitation are sources of Hg to the Arctic in its oxidized form (Hg(ii)). However, there is little evidence for the occurrence of AMDEs outside of coastal regions, and their importance to net Hg deposition has been questioned(2,7). Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide(8), raising questions as to the sources of high Arctic Hg loading. Here we present a comprehensive Hg-deposition mass-balance study, and show that most of the Hg (about 70%) in the interior Arctic tundra is derived from gaseous elemental Hg (Hg(0)) deposition, with only minor contributions from the deposition of Hg(ii) via precipitation or AMDEs. We find that deposition of Hg(0)-the form ubiquitously present in the global atmosphere-occurs throughout the year, and that it is enhanced in summer through the uptake of Hg(0) by vegetation. Tundra uptake of gaseous Hg(0) leads to high soil Hg concentrations, with Hg masses greatly exceeding the levels found in temperate soils. Our concurrent Hg stable isotope measurements in the atmosphere, snowpack, vegetation and soils support our finding that Hg(0) dominates as a source to the tundra. Hg concentration and stable isotope data from an inland-to-coastal transect show high soil Hg concentrations consistently derived from Hg(0), suggesting that the Arctic tundra might be a globally important Hg sink. We suggest that the high tundra soil Hg concentrations might also explain why Arctic rivers annually transport large amounts of Hg to the Arctic Ocean(9-11).
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