Letter | Published:

A global ocean inventory of anthropogenic mercury based on water column measurements

Nature volume 512, pages 6568 (07 August 2014) | Download Citation

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Abstract

Mercury is a toxic, bioaccumulating trace metal whose emissions to the environment have increased significantly as a result of anthropogenic activities such as mining and fossil fuel combustion1,2. Several recent models have estimated that these emissions have increased the oceanic mercury inventory by 36–1,313 million moles since the 1500s2,3,4,5,6,7,8,9. Such predictions have remained largely untested owing to a lack of appropriate historical data and natural archives. Here we report oceanographic measurements of total dissolved mercury and related parameters from several recent expeditions to the Atlantic, Pacific, Southern and Arctic oceans. We find that deep North Atlantic waters and most intermediate waters are anomalously enriched in mercury relative to the deep waters of the South Atlantic, Southern and Pacific oceans, probably as a result of the incorporation of anthropogenic mercury. We estimate the total amount of anthropogenic mercury present in the global ocean to be 290 ± 80 million moles, with almost two-thirds residing in water shallower than a thousand metres. Our findings suggest that anthropogenic perturbations to the global mercury cycle have led to an approximately 150 per cent increase in the amount of mercury in thermocline waters and have tripled the mercury content of surface waters compared to pre-anthropogenic conditions. This information may aid our understanding of the processes and the depths at which inorganic mercury species are converted into toxic methyl mercury and subsequently bioaccumulated in marine food webs.

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Acknowledgements

We thank the captains and crews of all cruises, as well as: P. Morton, J. Fitzsimmons, R. Shelley, A. Aguilar-Islas, R. Bundy, P. Morris, S. Owens, K. Wang, S. Rigaud and S. Pike for sample collection during the North Atlantic GEOTRACES cruise; L. Groot, D. Weiss, P. Laan, J. de Jong, R. Middag, L. Pena, A. Hartman, J. M. Godoy, L. Gerringa, M. Boyé and J. Dérot for sample collection during the South Atlantic GEOTRACES cruise; T. Goepfert, E. Bertrand and D. Moran for sampling during the Metalloenzyme cruise; and M. Rutgers van der Loeff and B. Galfond for providing samples from the 2011 Polarstern cruise ARK-XXVI/3–TransArc to the central Arctic Ocean. We are also grateful to D. Cossa and E. Sunderland for providing digital versions of their Southern Ocean and P16 data. We also thank H. Amos, L. Jaegle, B. Jonsson, R. Mason, E. Sunderland and Y. Zhang for discussions and D. Cossa for comments. This work was supported by NSF grant numbers OCE-0825108, OCE-0825157, OCE-0927274, OCE-0928191, OCE-1031271, OCE-1132480 and OCE-1132515. We thank co-Principal Investigators R. Mason and G. Gill. L.-E.H. thanks J. E Sonke for funding Arctic Ocean observations via research grant ERC-2010-StG_20091028 to JES.

Author information

Affiliations

  1. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA

    • Carl H. Lamborg
    • , Gretchen J. Swarr
    • , Kathleen M. Munson
    • , Daniel C. Ohnemus
    • , Phoebe J. Lam
    •  & Mak A. Saito
  2. Department of Earth and Environmental Sciences, Wright State University, Dayton, Ohio 45435, USA

    • Chad R. Hammerschmidt
    •  & Katlin L. Bowman
  3. Observatoire Midi-Pyrénées, Laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université Paul-Sabatier, 14, avenue Édouard Belin, 31400 Toulouse, France

    • Lars-Eric Heimbürger
  4. Department of Biological Oceanography, Royal Netherlands Institute for Sea Research, Den Burg, 1790 AB, The Netherlands

    • Micha J. A. Rijkenberg

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Contributions

C.H.L., C.R.H., K.L.B., G.J.S., D.C.O., L.-E.H., M.J.A.R. and M.A.S. participated in the GEOTRACES, Metalloenzyme cruises. C.H.L., C.R.H., K.L.B., G.J.S. and L.-E.H. performed Hg analyses. D.C.O. and P.J.L. designed the particulate sampling experiments and performed P analyses. C.H.L., C.R.H., M.J.A.R., M.A.S. and L.-E.H. designed the Hg-related experiments. C.H.L., C.R.H., K.L.B., G.J.S., K.M.M. and L.-E.H. interpreted the data. All authors contributed to manuscript preparation.

Corresponding author

Correspondence to Carl H. Lamborg.

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https://doi.org/10.1038/nature13563

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