Get access
Global Biogeochemical Cycles

Legacy impacts of all-time anthropogenic emissions on the global mercury cycle

Authors

  • Helen M. Amos,

    Corresponding author
    1. Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
    • Corresponding author: H. M. Amos, Department of Earth and Planetary Sciences, Harvard University, 29 Oxford St., Cambridge, MA 02138, USA. (amos@fas.harvard.edu)

    Search for more papers by this author
  • Daniel J. Jacob,

    1. Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts, USA
    2. School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
    Search for more papers by this author
  • David G. Streets,

    1. Decision and Information Sciences Division, Argonne National Laboratory, Argonne, Illinois, USA
    Search for more papers by this author
  • Elsie M. Sunderland

    1. School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, USA
    2. Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
    Search for more papers by this author

Abstract

[1] Elevated mercury (Hg) in marine and terrestrial ecosystems is a global health concern because of the formation of toxic methylmercury. Humans have emitted Hg to the atmosphere for millennia, and this Hg has deposited and accumulated into ecosystems globally. Here we present a global biogeochemical model with fully coupled atmospheric, terrestrial, and oceanic Hg reservoirs to better understand human influence on Hg cycling and timescales for responses. We drive the model with a historical inventory of anthropogenic emissions from 2000 BC to present. Results show that anthropogenic perturbations introduced to surface reservoirs (atmosphere, ocean, or terrestrial) accumulate and persist in the subsurface ocean for decades to centuries. The simulated present-day atmosphere is enriched by a factor of 2.6 relative to 1840 levels, consistent with sediment archives, and by a factor of 7.5 relative to natural levels (2000 BC). Legacy anthropogenic Hg re-emitted from surface reservoirs accounts for 60% of present-day atmospheric deposition, compared to 27% from primary anthropogenic emissions, and 13% from natural sources. We find that only 17% of the present-day Hg in the surface ocean is natural and that half of its anthropogenic enrichment originates from pre-1950 emissions. Although Asia is presently the dominant contributor to primary anthropogenic emissions, only 17% of the surface ocean reservoir is of Asian anthropogenic origin, as compared to 30% of North American and European origin. The accumulated burden of legacy anthropogenic Hg means that future deposition will increase even if primary anthropogenic emissions are held constant. Aggressive global Hg emission reductions will be necessary just to maintain oceanic Hg concentrations at present levels.

Get access to the full text of this article

Ancillary