Title: Stepwise Reduction Approach Reveals Mercury Competitive Binding and Exchange Reactions within Natural Organic Matter and Mixed Organic Ligands

Abstract

The kinetics of mercuric ion (Hg²⁺) binding with heterogeneous naturally dissolved organic matter (DOM) has been hypothesized to result from competitive interactions among different organic ligands and functional groups of DOM for Hg²⁺. However, an experimental protocol is lacking to determine Hg²⁺ binding with various competitive ligands and DOM, their binding strengths, and their dynamic exchange reactions. In this study, a stepwise reduction approach using ascorbic acid (AA) and stannous tin [Sn(II)] was devised to differentiate Hg(II) species in the presence of two major functional groups in DOM: the carboxylate-bound Hg(II) is reducible by both AA and Sn(II), whereas the thiolate-bound Hg(II) is reducible only by Sn(II). Using this operational approach, the relative binding strength of Hg²⁺ with selected organic ligands was found in the order dimercaptopropanesulfonate (DMPS) > glutathione (GSH) > penicillamine (PEN) > cysteine (CYS) > ethylenediaminetetraacetate > citrate, acetate, and glycine at the ligand-to-Hg molar ratio < 2. Dynamic, competitive ligand exchanges for Hg2+ from weak carboxylate to strong thiolate functional groups were observed among these ligands and within DOM, and the reaction depended on the relative binding strength and abundance of thiols and carboxylates, as well as reaction time. These results provide additional insights into dynamicmore » exchange reactions of Hg²⁺ within multicompositional DOM in controlling the transformation and bioavailability of Hg(II) in natural aquatic environments.« less

Authors:

Liang, Xujun ^[1]; Lu, Xia  ^[2];

• Search DOE PAGES for author "Lu, Xia"
• Search DOE PAGES for ORCID "0000-0003-2150-7575"

Zhao, Jiating ^[3]; Liang, Liyuan ^[3]; Zeng, Eddy Y.  ^[4];

• Search DOE PAGES for author "Zeng, Eddy Y."
• Search DOE PAGES for ORCID "0000-0002-0859-7572"

Gu, Baohua  ^[5]

• Search DOE PAGES for author "Gu, Baohua"
• Search DOE PAGES for ORCID "0000-0002-7299-2956"

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+ Show Author Affiliations

1. Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, China, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
2. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
3. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
4. Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou 511443, China
5. Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States, Department of Biosystems Engineering and Soil Science, University of Tennessee, Knoxville, Tennessee 37996, United States

Publication Date:

Thu Aug 15 00:00:00 EDT 2019

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

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

OSTI Identifier:

1559375

Alternate Identifier(s):

OSTI ID: 1562875; OSTI ID: 1564196

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Published Article

Journal Name:

Environmental Science and Technology

Additional Journal Information:

Journal Name: Environmental Science and Technology Journal Volume: 53 Journal Issue: 18; Journal ID: ISSN 0013-936X

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY