Open AccessAtmospheric mercury chemistry: Sensitivity of global model simulations to chemical reactions
Author(s) -
Seigneur Christian,
Vijayaraghavan Krish,
Lohman Kristen
Publication year - 2006
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005jd006780
Subject(s) - mercury (programming language) , chemistry , aqueous solution , atmospheric chemistry , chemical reaction , kinetics , radical , gas phase , redox , chemical kinetics , mercure , reaction rate , analytical chemistry (journal) , inorganic chemistry , environmental chemistry , catalysis , organic chemistry , ozone , physics , quantum mechanics , computer science , programming language
The effect of new mercury (Hg) chemistry information on Hg atmospheric concentrations is investigated in a systematic manner with a global chemical transport model, taking into account current uncertainties in Hg emission and removal rates. The reactions of interest include the gas‐phase oxidation of Hg(0) by O 3 , the gas‐phase oxidation of Hg(0) by OH, the aqueous‐phase reduction of Hg(II) by HO 2 radicals, a hypothetical gas‐phase reduction of Hg(II) by SO 2 , and a hypothetical pseudo‐first‐order gas‐phase reduction of Hg(II). The new kinetics of the oxidation of Hg(0) by O 3 is fast and would require balancing by a commensurate reduction reaction pathway that has not been identified; it may include some heterogeneous component and should be seen as an upper limit for atmospheric applications. Eliminating the gas‐phase oxidation of Hg(0) by both O 3 and OH does not lead to realistic Hg(0) concentrations even after eliminating the aqueous‐phase reduction of Hg(II) by HO 2 and having a greater dry deposition rate of Hg(0). Thus gas‐phase oxidation of Hg(0) by oxidants such as O 3 and/or OH is required to reproduce global Hg(0) concentration patterns. The reduction of Hg(II) by HO 2 (or a reaction with a similar overall rate) is needed to balance the oxidation of Hg(0) by OH and O 3 but is not needed if the gas‐phase oxidation of Hg(0) by OH is eliminated. The reduction of Hg(II) in power plant plumes can be represented by a reaction of Hg(II) with SO 2 ; such a reaction is consistent with the global cycling of Hg. However, a first‐order reaction for Hg(II) reduction in power plant plumes is not consistent with our current understanding of the atmospheric Hg chemistry. Additional laboratory studies are recommended to address the remaining uncertainties in the atmospheric chemistry of Hg.