Binding of mercury(II) to reduced sulfur in soil organic matter along upland-peat soil transects

Ulf Skyllberg, Kang Xia, Paul R. Bloom, Edward A. Nater, William F. Bleam

Research output: Contribution to journalArticlepeer-review

174 Scopus citations

Abstract

The binding of Hg2+ in organic matter of soils and waters controls the transport and transformations of Hg in terrestrial and aquatic ecosystems. We developed a competitive complexation method using the strong complexation of Hg2+ by Br- for determining the Hg2+ binding strength in organic soils at native and elevated Hg concentrations. The distribution coefficients determined in KBr suspensions for sorption of native Hg2+ to soil organic carbon (SOC) (K(soc)) are in the range of 1022 to 1023. The K(soc) significantly decreased with increased additions of Hg2+ and with decreasing pH. Using data for reduced organic S concentrations determined by x-ray absorption near-edge structure spectroscopy (XANES), we calculated surface complex formation constants on the order of 1032 for a model site having acidity constants of mercaptoacetic acid. This value is in fair agreement with the tabulated value of 1034.5 for Hg2+ binding in mercaptoacetic acid. At native Hg concentrations, formation constants and K(soc) values were similar for different types of soil organic matter along transects from uplands into wetlands, despite varying concentrations of Hg and reduced organic S. Our adsorption data are consistent with the conclusions from our previous extended x-ray absorption fine structure spectroscopy (EXAFS) study that in a humic acid and soil, Hg2+ ions bond in two-fold coordination involving one reduced S and one O or N.

Original languageEnglish (US)
Pages (from-to)855-865
Number of pages11
JournalJournal of Environmental Quality
Volume29
Issue number3
DOIs
StatePublished - Jan 1 2000

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