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Dissolution of cinnabar (HgS) in the presence of natural organic matter

Geochimica et Cosmochimica Acta

By:
, , ,
DOI: 10.1016/j.gca.2004.09.029

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Abstract

Cinnabar (HgS) dissolution rates were measured in the presence of 12 different natural dissolved organic matter (DOM) isolates including humic, fulvic, and hydrophobic acid fractions. Initial dissolution rates varied by 1.3 orders of magnitude, from 2.31 ?? 10-13 to 7.16 ?? 10-12 mol Hg (mg C)-1 m-2 s-1. Rates correlate positively with three DOM characteristics: specific ultraviolet absorbance (R2 = 0.88), aromaticity (R2 = 0.80), and molecular weight (R2 = 0.76). Three experimental observations demonstrate that dissolution was controlled by the interaction of DOM with the cinnabar surface: (1) linear rates of Hg release with time, (2) significantly reduced rates when DOM was physically separated from the surface by dialysis membranes, and (3) rates that approached constant values at a specific ratio of DOM concentration to cinnabar surface area, suggesting a maximum surface coverage by dissolution-reactive DOM. Dissolution rates for the hydrophobic acid fractions correlate negatively with sorbed DOM concentrations, indicating the presence of a DOM component that reduced the surface area of cinnabar that can be dissolved. When two hydrophobic acid isolates that enhanced dissolution to different extents were mixed equally, a 20% reduction in rate occurred compared to the rate with the more dissolution-enhancing isolate alone. Rates in the presence of the more dissolution-enhancing isolate were reduced by as much as 60% when cinnabar was prereacted with the isolate that enhanced dissolution to a lesser extent. The data, taken together, imply that the property of DOM that enhances cinnabar dissolution is distinct from the property that causes it to sorb irreversibly to the cinnabar surface. Copyright ?? 2005 Elsevier Ltd.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Dissolution of cinnabar (HgS) in the presence of natural organic matter
Series title:
Geochimica et Cosmochimica Acta
DOI:
10.1016/j.gca.2004.09.029
Volume
69
Issue:
6
Year Published:
2005
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
First page:
1575
Last page:
1588
Number of Pages:
14