GEOC 127 |
| Christopher C. Fuller1, John R. Bargar2, Samuel M. Webb2, Peggy A. O'Day3, Martha H. Conklin4, Aiko K. Condon5, Matthew A. Marcus6, and W.A. Caldwell6. (1) Water Resources Division, U.S. Geological Survey, 345 Middelfield Rd, Menlo Park, CA 94025, (2) Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road, MS 69, Menlo Park, CA 94025, (3) School of Natural Sciences, University of California Merced, Merced, CA 95344, (4) School of Engineering, University of California Merced, Merced, CA 95344, (5) Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721, (6) Advanced Light Source, Lawrence Berkeley National Laboratory, One cyclotron Rd, Berkeley, CA 94720 |
| The mechanisms responsible for dissolved Zn attenuation in a mining-impacted stream were investigated using bulk and micro EXAFS, synchrotron-source bulk and micro XRD, and micro XRF measurements of streambed sediments collected from the active hyporheic zone of Pinal Creek, AZ. Microbial Mn(II) oxidation has produced extensive Mn oxide coatings on streambed sediments that enhance attenuation of other dissolved metal contaminants (Co, Ni and Zn) via sorption reactions during hydrologic exchange of stream water into the streambed. Column experiments with streambed sediments indicate a high capacity of Mn oxide coatings for Zn. Micro-XANES and –XRD measurements indicate Mn is predominantly in the +4 oxidation state in the coatings, with a 7 Å phyllomanganate being the dominant crystalline phase. The spatial Zn distribution correlates highly with the sediment Mn-oxide coatings. These results suggest that natural attenuation of Zn contamination in Pinal Creek is dominated by sorption to birnessite. |
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Poster Session
6:00 PM-9:00 PM, Tuesday, March 30, 2004 Anaheim Convention Center -- Hall A, Poster
Division of Geochemistry |