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Modeling the OH-Initiated Oxidation of Mercury in the Global Atmosphere Without Violating Physical Laws

preprint
revised on 02.11.2019, 11:11 and posted on 07.11.2019, 22:30 by Theodore Dibble, Hanna Tetu, yuge jiao, Colin Thackray, Daniel J. Jacob
We present a way for modelers to include the OH + Hg reaction while accounting quantitatively for the dissociation of HOHg•. We use high levels of quantum chemistry to establish the HO-Hg bond energy as 11.0 kcal/mole, and calculate the equilibrium constant for OH + Hg = HOHg•. Using the measured rate constant for association of OH with Hg, we determine the rate constant for HOHg• dissociation. Theory is also used to demonstrate that HOHg• forms stable compounds, HOHgY, with atmospheric radicals (Y = NO2, HOO•, CH3OO•, and BrO). We then present rate constants for use in in modeling OH-initiated oxidation of Hg(0). We use this mechanism to model the global oxidation of Hg(0) in the period 2013-2015 using the GEOS-Chem 3D model of atmospheric chemistry. Because of the rapid dissociation of HOHg•, OH accounts for <1% of the global oxidation of Hg(0) to Hg(II), while Br atoms account for 97%.

Funding

National Science Foundation awards 1609848 and 1643217

History

Email Address of Submitting Author

tsdibble@esf.edu

Institution

State University of New York College of Environmental Science and Forestry

Country

United States of America

ORCID For Submitting Author

0000-0002-0023-8233

Declaration of Conflict of Interest

No conflict of interest

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