Tundra uptake of atmospheric elemental mercury drives Arctic mercury pollution

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Anthropogenic activities have led to large-scale mercury (Hg) pollution in the Arctic1,2,3,4,5,6. 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 questioned2,7. Furthermore, wet-deposition measurements in the Arctic showed some of the lowest levels of Hg deposition via precipitation worldwide8, 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 Ocean9,10,11.

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We thank Toolik Field Station and Polar Field Services staff for their support in setting up the field site and maintaining its operation for two years, with special thanks to J. Timm. We thank O. Dillon and C. Pearson for support with laboratory analyses; A. Steffen and S. Brooks for providing additional instrumentation; J. Chmeleff for support with inductively coupled plasma mass spectrometry; and R. Kreidberg and J. Arnone for editorial and technical assistance in manuscript preparation. The project was funded primarily by a US National Science Foundation (NSF) award (PLR 1304305), with additional support provided by further NSF (CHN 1313755) and US Department of Energy (DE-SC0014275) awards. The Hg isotope work was funded by H2020 Marie Sklodowska-Curie grant agreement no. 657195 to M.J., and European Research Council grant ERC-2010-StG_20091028 and CNRS-INSU-CAF funding (PARCS project) to J.E.S.

Author information


  1. Department of Environmental, Earth and Atmospheric Sciences, University of Massachusetts, Lowell, Massachusetts 01854, USA

    • Daniel Obrist
  2. Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, Nevada 89512, USA

    • Daniel Obrist
    • , Yannick Agnan
    • , Christine L. Olson
    •  & Christopher W. Moore
  3. Milieux Environnementaux, Transferts et Interactions dans les Hydrosystèmes et les Sols (METIS), UMR 7619, Sorbonne Universités UPMC-CNRS-EPHE, 4 place Jussieu, F-75252 Paris, France

    • Yannick Agnan
  4. Géosciences Environnement Toulouse, CNRS/OMP/Université de Toulouse, 14 Avenue Edouard Belin, 31400 Toulouse, France

    • Martin Jiskra
    •  & Jeroen E. Sonke
  5. Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, 4001 Discovery Drive, Boulder, Colorado 80309, USA

    • Dominique P. Colegrove
    • , Jacques Hueber
    •  & Detlev Helmig
  6. Gas Technology Institute (GTI), 1700 South Mount Prospect Road, Des Plaines, Illinois 60018, USA

    • Christopher W. Moore


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D.O. and D.H. initiated and designed this project, and M.J., J.E.S. and D.O. designed and developed the isotope component. All authors were involved in all field sampling and/or laboratory analyses. Y.A. led data analysis of flux data, and M.J. led stable isotope sampling and analysis with support from J.E.S. D.O. led manuscript writing with major support from M.J., Y.A., J.E.S. and C.W.M.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Daniel Obrist or Detlev Helmig.

Reviewer Information Nature thanks J. Blum and the other anonymous reviewer(s) for their contribution to the peer review of this work.

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