Title: Mechanistic Investigation of Dimethylmercury Formation Mediated by a Sulfide Mineral Surface

Abstract

Mercury (Hg) pollution is a global environmental problem. The abiotic formation of dimethylmercury (DMeHg) from monomethylmercury (MMeHg) may account for a large portion of DMeHg in oceans. Previous experimental work has shown that abiotic formation of DMeHg from MMeHg can be facilitated by reduced sulfur groups on sulfide mineral surfaces. In that work, a mechanism was proposed in which neighboring MMeHg moieties bound to sulfide sites on a mineral surface react through an S_N2-type mechanism to form DMeHg and incorporate the remaining Hg atoms into the mineral surface. Here, we perform density functional theory calculations to explore the mechanisms of DMeHg formation on the 110 surface of a CdS(s) (hawleyite) nanoparticle. We show that coordination of MMeHg substituents to adjacent reduced sulfur groups protruding from the surface indeed facilitates DMeHg formation and that the reaction proceeds through direct transmethylation from one MMeHg substituent to another. Coordination of Hg by multiple S atoms provides a transition-state stabilization and activates a C–Hg bond for methyl transfer. In addition, solvation effects play an important role in the surface reconstruction of the nanoparticle and in decreasing the energetic barrier for DMeHg formation relative to the corresponding reaction in vacuo.

Authors:

Lian, Peng  ^[1];

• Search DOE PAGES for author "Lian, Peng"
• Search DOE PAGES for ORCID "0000-0003-1701-5025"

Mou, Zhongyu  ^[2];

• Search DOE PAGES for author "Mou, Zhongyu"
• Search DOE PAGES for ORCID "0000-0003-2240-3129"

Cooper, Connor J.  ^[2];

• Search DOE PAGES for author "Cooper, Connor J."
• Search DOE PAGES for ORCID "0000-0002-5527-9948"

Johnston, Ryne C.  ^[2];

• Search DOE PAGES for author "Johnston, Ryne C."
• Search DOE PAGES for ORCID "0000-0002-6606-9401"

Brooks, Scott C.  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-8437-9788"

Gu, Baohua  ^[2];

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• Search DOE PAGES for ORCID "0000-0002-7299-2956"

Govind, Niranjan  ^[3];

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• Search DOE PAGES for ORCID "0000-0003-3625-366X"

Jonsson, Sofi  ^[4];

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• Search DOE PAGES for ORCID "0000-0002-6142-6983"

Parks, Jerry M.  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-3103-9333"

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Tennessee, Knoxville, TN (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
4. Stockholm Univ. (Sweden)

Publication Date:

Fri Jun 11 00:00:00 EDT 2021

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1809955

Grant/Contract Number:  

AC05-00OR22725; AC05-76RL01830

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory

Additional Journal Information:

Journal Volume: 125; Journal Issue: 24; Journal ID: ISSN 1089-5639

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY