Global warming accelerates uptake of atmospheric mercury in regions experiencing glacier retreat

Edited by Zhi-Sheng An, Institute of Earth Environment, Xi’an, China, and approved December 6, 2019 (received for review April 22, 2019)
January 13, 2020
117 (4) 2049-2055

Significance

In this study, we identify a process that recaptures atmospheric Hg in glacier-retreated areas driven by global warming. Melting of glaciers is known to release Hg originally locked in ice into the atmosphere and downstream ecosystems. Recession of glaciers promotes rapid establishment of vegetative ecosystems that capture more atmospheric Hg over the long run than the Hg released from glacier melting. The increased vegetative biomass driven by climate change can result in significant changes in global Hg cycling.

Abstract

As global climate continues to warm, melting of glaciers releases a large quantity of mercury (Hg) originally locked in ice into the atmosphere and downstream ecosystems. Here, we show an opposite process that captures atmospheric Hg through glacier-to-vegetation succession. Our study using stable isotope techniques at 3 succession sites on the Tibetan Plateau reveals that evolving vegetation serves as an active “pump” to take up gaseous elemental mercury (Hg0) from the atmosphere. The accelerated uptake enriches the Hg pool size in glacier-retreated areas by a factor of ∼10 compared with the original pool size in the glacier. Through an assessment of Hg source–sink relationship observed in documented glacier-retreated areas in the world (7 sites of tundra/steppe succession and 5 sites of forest succession), we estimate that 400 to 600 Mg of Hg has been accumulated in glacier-retreated areas (5‰ of the global land surface) since the Little Ice Age (∼1850). By 2100, an additional ∼300 Mg of Hg will be sequestered from the atmosphere in glacier-retreated regions globally, which is ∼3 times the total Hg mass loss by meltwater efflux (∼95 Mg) in alpine and subpolar glacier regions. The recapturing of atmospheric Hg by vegetation in glacier-retreated areas is not accounted for in current global Hg models. Similar processes are likely to occur in other regions that experience increased vegetation due to climate or land use changes, which need to be considered in the assessment of global Hg cycling.

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Acknowledgments

This work was funded by the Strategic Priority Research Programs of the Chinese Academy of Sciences; Pan-Third Pole Environment Study for a Green Silk Road Grant XDA2004050201; National Natural Science Foundation of China Grants 41977272, 41829701, 41703135, and 41771062; and the K. C. Wong Education Foundation. The contribution of F.W. was partially supported by the Canada Research Chairs program.

Supporting Information

Appendix (PDF)

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Information & Authors

Information

Published in

Go to Proceedings of the National Academy of Sciences
Go to Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
Vol. 117 | No. 4
January 28, 2020
PubMed: 31932430

Classifications

Submission history

Published online: January 13, 2020
Published in issue: January 28, 2020

Keywords

  1. global warming
  2. glacier retreat
  3. atmospheric mercury deposition

Acknowledgments

This work was funded by the Strategic Priority Research Programs of the Chinese Academy of Sciences; Pan-Third Pole Environment Study for a Green Silk Road Grant XDA2004050201; National Natural Science Foundation of China Grants 41977272, 41829701, 41703135, and 41771062; and the K. C. Wong Education Foundation. The contribution of F.W. was partially supported by the Canada Research Chairs program.

Notes

This article is a PNAS Direct Submission.

Authors

Affiliations

State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
Ji Luo
Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China;
Wei Yuan
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
University of Chinese Academy of Sciences, Beijing 100049, China;
Center for Advances in Water and Air Quality, Lamar University, Beaumont, TX 77710;
Department of Civil and Environmental Engineering, Lamar University, Beaumont, TX 77710;
Centre for Earth Observation Science, and Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada;
Chen Liu
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
University of Chinese Academy of Sciences, Beijing 100049, China;
Genxu Wang
Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China;
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
University of Chinese Academy of Sciences, Beijing 100049, China;
Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xian 710061, China

Notes

1
To whom correspondence may be addressed. Email: [email protected].
Author contributions: X.W. and X.F. designed research; X.W., J.L., W.Y., C.L., G.W., and X.F. performed research; X.W. and X.F. contributed new reagents/analytic tools; X.W., W.Y., C.-J.L., F.W., and X.F. analyzed data; and X.W., C.-J.L., and F.W. wrote the paper.

Competing Interests

The authors declare no competing interest.

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    Global warming accelerates uptake of atmospheric mercury in regions experiencing glacier retreat
    Proceedings of the National Academy of Sciences
    • Vol. 117
    • No. 4
    • pp. 1821-2227

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