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Projecting Global Mercury Emissions and Deposition Under the Shared Socioeconomic Pathways
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  • Benjamin M. Geyman,
  • David G Streets,
  • Colin P Thackray,
  • Christine Olson,
  • Kevin M. Schaefer,
  • Elsie M. Sunderland
Benjamin M. Geyman
Harvard University

Corresponding Author:[email protected]

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David G Streets
Harvard University
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Colin P Thackray
Harvard University
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Christine Olson
University of Colorado Boulder
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Kevin M. Schaefer
University of Colorado Boulder
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Elsie M. Sunderland
Harvard University
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Abstract

Mercury (Hg) is a naturally occurring element that has been greatly enriched in the environment by activities like mining and fossil fuel combustion. Despite commonalities in some CO2 and Hg emission sources, the implications of long-range climate scenarios for anthropogenic Hg emissions have yet to be explored. Here, we present comprehensive projections of anthropogenic Hg emissions (2020-2300) and evaluate impacts on global atmospheric Hg deposition. Projections are based on four shared socioeconomic pathway (SSP) narratives ranging from sustainable reductions in resource and energy intensity to rapid economic growth driven by abundant fossil fuel exploitation. There is a greater than two-fold difference in cumulative anthropogenic Hg emissions between the lower-bound (110 Gg) and upper-bound (230 Gg) scenarios. Hg releases to land and water are approximately six times those of direct emissions to air (600-1470 Gg). At their peak, anthropogenic Hg emissions reach 2200-2600 Mg a-1 sometime between 2010 (baseline) and 2030, depending on the SSP scenario. Coal combustion is the largest determinant of differences in Hg emissions among scenarios. Decoupling of Hg and CO2 emissions sources occurs under low- to mid-range scenarios, though contributions from artisanal and small-scale gold mining remain uncertain. A projected future shift in speciation of Hg emissions toward lower gaseous elemental Hg (Hg0) and higher divalent Hg (HgII) will result in a higher fraction of locally-sourced Hg deposition. Projected re-emissions of previously deposited anthropogenic Hg follow a similar temporal trajectory to primary emissions, amplifying benefits of primary Hg emissions reductions under the most stringent mitigation scenarios.
Apr 2024Published in Earth's Future volume 12 issue 4. 10.1029/2023EF004231