GEOC 177 |
| Juraj Majzlan and Satish C.B. Myneni. Department of Geosciences, Princeton University, Princeton, NJ 08544 |
| Acidic waters originate from weathering of sulfides and contain high concentrations of sulfate, nitrate, and metals. These ions deteriorate water quality and are toxic to biota. Using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and X-ray absorption near edge structure (XANES) spectroscopy, we studied interaction of sulfate with ferric iron species. The equilibrium constants for reactions of these aqueous ions indicate their tendency to form dominantly inner-sphere complexes in solutions. ATR-FTIR spectra suggest marked distortion of the sulfate ion, confirming that iron and sulfate in the solution interact strongly. However, the XANES data indicate that the inner-sphere complexes comprise no more than 15 % of total sulfate in these solutions. Our results imply that there exists a strong interaction between iron oligomers and sulfate, but via hydrogen bonds. These results also provide a simple and logical link between solution speciation and structure of solid precipitates. In acid soils and acidified sediments, the availability and solubility of sulfate and metals is likely controlled by solids with dominantly hydrogen-bonded interaction between iron and sulfate, such as schwertmannite, not goethite or jarosite, as commonly assumed and modeled. |
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Vibrational Spectroscopy in the Earth and Environmental Sciences
8:00 AM-11:40 AM, Thursday, April 1, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |