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Binding of mercury(II) to dissolved organic matter: The role of the mercury-to-DOM concentration ratio

Environmental Science and Technology

By:
, ,
DOI: 10.1021/es025699i

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Abstract

The binding of Hg(II) to dissolved organic matter (DOM; hydrophobic acids isolated from the Florida Everglades by XAD-8 resin) was measured at a wide range of Hg-to-DOM concentration ratios using an equilibrium dialysis ligand exchange method. Conditional distribution coefficients (KDOM???) determined by this method were strongly affected by the Hg/DOM concentration ratio. At Hg/DOM ratios below approximately 1 ??g of Hg/mg of DOM, we observed very strong interactions (KDOM??? = 1023.2??1.0 L kg-1 at pH = 7.0 and I = 0.1), indicative of mercury-thiol bonds. Hg/DOM ratios above approximately 10 ??g of Hg/mg of DOM, as used in most studies that have determined Hg-DOM binding constants, gave much lower KDOM??? values (1010.7??1.0 L kg-1 at pH = 4.9-5.6 and I = 0.1), consistent with Hg binding mainly to oxygen functional groups. These results suggest that the binding of Hg to DOM under natural conditions (very low Hg/DOM ratios) is controlled by a small fraction of DOM molecules containing a reactive thiol functional group. Therefore, Hg/DOM distribution coefficients used for modeling the biogeochemical behavior of Hg in natural systems need to be determined at low Hg/DOM ratios.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Binding of mercury(II) to dissolved organic matter: The role of the mercury-to-DOM concentration ratio
Series title:
Environmental Science and Technology
DOI:
10.1021/es025699i
Volume
36
Issue:
16
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
3564
Last page:
3570
Number of Pages:
7