Articles | Volume 15, issue 12
Atmos. Chem. Phys., 15, 7103–7125, 2015
Atmos. Chem. Phys., 15, 7103–7125, 2015

Research article 30 Jun 2015

Research article | 30 Jun 2015

Top-down constraints on atmospheric mercury emissions and implications for global biogeochemical cycling

S. Song1, N. E. Selin1,2, A. L. Soerensen3,4, H. Angot5, R. Artz6, S. Brooks7, E.-G. Brunke8, G. Conley9, A. Dommergue5, R. Ebinghaus10, T. M. Holsen11, D. A. Jaffe12,13, S. Kang14,15, P. Kelley6,16, W. T. Luke6, O. Magand5, K. Marumoto17, K. A. Pfaffhuber18, X. Ren6,16, G.-R. Sheu19, F. Slemr20, T. Warneke21, A. Weigelt10, P. Weiss-Penzias22, D. C. Wip23, and Q. Zhang24 S. Song et al.
  • 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 2Engineering Systems Division, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 3Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA
  • 4Department of Applied Environmental Science, Stockholm University, Stockholm, Sweden
  • 5Univ. Grenoble Alpes, CNRS, LGGE, Grenoble, France
  • 6Air Resources Laboratory, National Oceanic and Atmospheric Administration, College Park, MD, USA
  • 7Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee Space Institute, Tullahoma, TN, USA
  • 8South African Weather Service c/o CSIR, Stellenbosch, South Africa
  • 9Center for Air Quality, Ohio University, Athens, OH, USA
  • 10Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
  • 11Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY, USA
  • 12School of Science, Technology, Engineering and Mathematics, University of Washington, Bothell, WA, USA
  • 13Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
  • 14State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences (CAS), Lanzhou, China
  • 15CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing, China
  • 16Cooperative Institute for Climate and Satellites, University of Maryland, College Park, MD, USA
  • 17Environmental Chemistry Section, National Institute for Minamata Disease, Kumamoto, Japan
  • 18Norwegian Institute for Air Research (NILU), Tromsø, Norway
  • 19Department of Atmospheric Sciences, National Central University, Jhongli, Taiwan
  • 20Max Planck Institute for Chemistry, Air Chemistry Division, Mainz, Germany
  • 21Institute of Environmental Physics, University of Bremen, Bremen, Germany
  • 22Microbiology and Environmental Toxicology, University of California, Santa Cruz, CA, USA
  • 23Anton de Kom Universiteit van Suriname, Paramaribo, Suriname
  • 24Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China

Abstract. We perform global-scale inverse modeling to constrain present-day atmospheric mercury emissions and relevant physiochemical parameters in the GEOS-Chem chemical transport model. We use Bayesian inversion methods combining simulations with GEOS-Chem and ground-based Hg0 observations from regional monitoring networks and individual sites in recent years. Using optimized emissions/parameters, GEOS-Chem better reproduces these ground-based observations and also matches regional over-water Hg0 and wet deposition measurements. The optimized global mercury emission to the atmosphere is ~ 5.8 Gg yr−1. The ocean accounts for 3.2 Gg yr−1 (55 % of the total), and the terrestrial ecosystem is neither a net source nor a net sink of Hg0. The optimized Asian anthropogenic emission of Hg0 (gas elemental mercury) is 650–1770 Mg yr−1, higher than its bottom-up estimates (550–800 Mg yr−1). The ocean parameter inversions suggest that dark oxidation of aqueous elemental mercury is faster, and less mercury is removed from the mixed layer through particle sinking, when compared with current simulations. Parameter changes affect the simulated global ocean mercury budget, particularly mass exchange between the mixed layer and subsurface waters. Based on our inversion results, we re-evaluate the long-term global biogeochemical cycle of mercury, and show that legacy mercury becomes more likely to reside in the terrestrial ecosystem than in the ocean. We estimate that primary anthropogenic mercury contributes up to 23 % of present-day atmospheric deposition.

Short summary
A better knowledge of mercury (Hg) emission fluxes into the global atmosphere is important for assessing its human health impacts and evaluating the effectiveness of corresponding policy actions. We for the first time apply a top-down approach at a global scale to quantitatively estimate present-day mercury emission sources as well as key parameters in a chemical transport model, in order to better constrain the global biogeochemical cycle of mercury.
Final-revised paper