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

S Song. (1) , Ne Selin (2, 1) , A.L Soerensen (3, 4) , Hélène Angot (5) , R Artz (6) , S. Brooks (7) , E.-G. Brunke (8) , G Conley (9) , Aurelien Dommergue (5) , R. Ebinghaus (10) , T.M Holsen (11) , D. Jaffe (12) , S. Kang (13) , P. Kelley (14) , Wt Luke (14) , Olivier Magand (5) , K. Marumoto (15) , Ka Pfaffhuber (16) , X Ren (17, 14) , Gr Sheu (18) , F. Slemr (19) , T. Warneke (20) , A Weigelt (10) , P Weiss-Penzias (21) , Dc Wip (22) , Q. P. Zhang (23)

1 EAPS - Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge]
2 MIT - Massachusetts Institute of Technology
3 Harvard School of Public Health
4 Stockholm University
5 LGGE - Laboratoire de glaciologie et géophysique de l'environnement
6 ARL - NOAA Air Resources Laboratory
7 Department of Mechanical, Aerospace and Biomedical Engineering
8 SAWS - South African Weather Service
9 Ohio University
10 GKSS-Forschungszentrum Geesthacht GmbH
11 Clarkson University
12 University of Washington-Bothell
13 CAS - Chinese Academy of Sciences [Beijing]
14 NOAA - National Oceanic and Atmospheric Administration
15 National Institute for Minamata Disease
16 NILU - Norwegian Institute for Air Research
17 University of Maryland [College Park]
18 NTU - National Taiwan University [Taiwan]
19 MPIC - Max-Planck-Institut für Chemie
20 IUP - Institute of Environmental Physics [Bremen]
21 UC Santa Cruz - University of California [Santa Cruz]
22 UVS - Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo]
23 Institute of Tibetan Plateau Research

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.

Domaines: Sciences de l'environnement

S Song., Ne Selin, A.L Soerensen, Hélène Angot, R Artz, et al.. Top-down constraints on atmospheric mercury emissions and implications for global biogeochemical cycling. Atmospheric Chemistry and Physics, 2015, 15 (12), pp.7103-7125. ⟨10.5194/acp-15-7103-2015⟩. ⟨insu-01203657⟩