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Binding of mercury(II) to aquatic humic substances: Influence of pH and source of humic substances

Environmental Science and Technology

By:
, , and
DOI: 10.1021/es026291o

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Abstract

Conditional distribution coefficients (KDOM???) for Hg(II) binding to seven dissolved organic matter (DOM) isolates were measured at environmentally relevant ratios of Hg(II) to DOM. The results show that KDOM??? values for different types of samples (humic acids, fulvic acids, hydrophobic acids) isolated from diverse aquatic environments were all within 1 order of magnitude (1022.5??1.0-1023.5??1.0 L kg-1), suggesting similar Hg(II) binding environments, presumably involving thiol groups, for the different isolates. KDOM??? values decreased at low pHs (4) compared to values at pH 7, indicating proton competition for the strong Hg(II) binding sites. Chemical modeling of Hg(II)-DOM binding at different pH values was consistent with bidentate binding of Hg(II) by one thiol group (pKa = 10.3) and one other group (pKa = 6.3) in the DOM, which is in agreement with recent results on the structure of Hg(II)-DOM bonds obtained by extended X-ray absorption fine structure spectroscopy (EXAFS).

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Binding of mercury(II) to aquatic humic substances: Influence of pH and source of humic substances
Series title:
Environmental Science and Technology
DOI:
10.1021/es026291o
Volume
37
Issue:
11
Year Published:
2003
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
2436
Last page:
2441