Oxidation of dissolved elemental mercury by thiol compounds under anoxic conditions

Journal Article · Tue Jan 01 04:00:00 EST 2013 · Environmental Science & Technology

DOI:https://doi.org/10.1021/es402697u· OSTI ID:1110863

Zheng, Wang ^[1]; Lin, Hui ^[1]; Mann, Benjamin F ^[1]; Liang, Liyuan ^[1]; Gu, Baohua ^[1]

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1. ORNL

Mercuric mercury, Hg(II), forms strong complexes with thiol compounds that commonly dominate Hg(II) speciation in natural freshwater. However, reactions between dissolved elemental Hg(0) and thiols are not well understood although these processes are likely to be important in determining Hg speciation and geochemical cycling in the environment. In this study, reaction rates and mechanisms between dissolved Hg(0) and a number of selected organic ligands with varying molecular structures and sulfur (S) oxidation states were determined to assess the role of these ligands in Hg(0) redox transformation. We found that all thiols caused oxidation of Hg(0) under anoxic conditions but, contrary to expectation, compounds with higher S-oxidation states (e.g., disulfide) than thiols exhibited little or no reactivity with Hg(0) at pH 7. The rate and extent of Hg(0) oxidation varied widely, with smaller aliphatic thiols showing the greatest degree of oxidation. The mechanism of the oxidation is attributed to a two-step process involving adsorption of Hg(0) to thiols followed by the charge transfer from Hg(0) to electron acceptors. These observations demonstrate a unique thiol-induced oxidation pathway of dissolved Hg(0), with important implications for the redox transformation, speciation, and bioavailability of Hg for microbial methylation in anoxic environments.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1110863
• Journal Information: Environmental Science & Technology, Journal Name: Environmental Science & Technology Journal Issue: 10 Vol. 47; ISSN 0013-936X
• Country of Publication: United States
• Language: English