GEOC 19 |
| George R. Helz and Carla S. Neuberger. Chemistry and Biochemistry, University of Maryland, College Park, MD 20742 |
| In reduced aquatic environments, low HS- concentrations precipitate numerous biologically active trace metals. Higher HS- concentrations reverse this effect owing to complexing by HS-, S2- and Sn2- ligands. Here we argue that thioanions further promote solubility. The most abundant thioanion-forming elements in nature are probably MoVI and AsIII. Because thioanions of these elements act as multidentate ligands, which have large stability constants, they can be important in nature despite concentrations that rarely exceed 1 µM. Oxyanions of both elements are poor ligands; only when transformed to thioanions by H2S > 11 µM for MoVI and > 3 µM (pH 7) for AsIII (25oC) are they likely to be important metal complexers. Copper(I) binds strongly to both Mo and As thioanions. Current work suggests that thioarsenites are poor ligands for Pb but strong for Ag. Thiomolybdates bind Fe so strongly that Mo may be important in Fe-S diagenesis. |
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Chemistry of Metals in Terrestrial and Aquatic Systems
8:10 AM-11:30 AM, Monday, March 29, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |