Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona
Environmental Science & Technology
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Abstract
The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using extended X-ray absorption fine structure (EXAFS) and microfocused synchrotron X-ray fluorescence (μSXRF) mapping, and chemical extraction. μSXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and microfocused EXAFS spectra of Zn in the biogenic Mn oxide coating are indicative of Zn forming triple-corner-sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to the decrease in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in the solid/solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating that desorption is not controlled by dissolution of secondary Zn phases. In summary, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process of Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona |
| Series title | Environmental Science & Technology |
| DOI | 10.1021/es402576f |
| Volume | 48 |
| Issue | 4 |
| Year Published | 2014 |
| Language | English |
| Publisher | ACS Publications |
| Contributing office(s) | National Research Program - Western Branch, Toxic Substances Hydrology Program |
| Description | 8 p. |
| First page | 2165 |
| Last page | 2172 |
| Country | United States |
| State | Arizona |
| Other Geospatial | Pinal Creek |
| Google Analytic Metrics | Metrics page |