| Abstract: | Anomalously uraniferous waters occur in a small (4.2 km2) drainage in the west-central Carson Range, Nevada, on the eastern side of Lake Tahoe. The waters transport uranium from local U-rich soils and bedrock to organic-rich valley-fill sediments where it is concentrated, but weakly bound. The dissolved U and the U that is potentially available from coexisting sediments pose a threat to the quality of drinking water that is taken from the drainage. The U concentration in samples of 6 stream, 11 spring and 7 near-surface waters ranged from <1 to 177 ??g l-1 with an average value of 17 ?? 14 ??g l-1 for stream and spring waters. This value significantly exceeds a reported regional average value of ~5 ??g l-1, and is comparable to proposed maximum contaminant levels of U in drinking water. Calculations that utilize chemical compositions of the waters and thermodynamic data indicate that uranyl-carbonate and uranyl-phosphate complexes are the major inorganic species of dissolved U. In addition, dialysis experiments suggest an association of at least some dissolved U with macromolecular organic matter, particularly in near-surface waters that are in contact with organic-rich sediments. Calculations of the saturation index for uranous and uranyl-bearing minerals indicate that all of the waters are undersaturated with uranium minerals as long as ambient Eh is oxidizing (i.e. > 0.1 V). Possible precipitation of U(IV) minerals is predicted under the more reducing conditions that are particularly likely in near-surface waters, but the inhibitory effects of sluggish kinetics or organic complexing are not considered. These combined results suggest that a process such as adsorption or ion exchange, rather than mineral saturation, is the most probable mechanism for uranium fixation in the sediments. -Authors |
| Genre: | Article |
| ProdID: | 70014340 |
| Citation Author: | Zielinski, R. A.; Otton, J. K.; Wanty, R. B.; Pierson, C. T. |
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| Citation End Page: | 305 |
| Citation Issue: | 4 |
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| Citation Language: | English |
| Citation Larger Work Title: | Uranium |
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| Citation Number Of Pages: | 25 |
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| Citation Search Results Text: | The aqueous geochemistry of uranium in a drainage containing uraniferous organic-rich sediments, Lake Tahoe area, Nevada, USA; 1988; Article; Journal; Uranium; Zielinski, R. A.; Otton, J. K.; Wanty, R. B.; Pierson, C. T. |
| Citation Start Page: | 281 |
| Citation Volume: | 4 |
| Citation Year: | 1988 |
| Type: | citation/reference |
| Text: | The aqueous geochemistry of uranium in a drainage containing uraniferous organic-rich sediments, Lake Tahoe area, Nevada, USA; 1988; Article; Journal; Uranium; Zielinski, R. A.; Otton, J. K.; Wanty, R. B.; Pierson, C. T. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| Date Other: | Fri, 1 Jan 1988 00:00 -0600 |
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