Bicarbonate Impact on U(VI) Bioreduction in a Shallow Alluvial Aquifer
Field-scale biostimulation and desorption tracer experiments conducted in a uranium (U) contaminated, shallow alluvial aquifer have provided insight into the coupling of microbiology, biogeochemistry, and hydrogeology that control U mobility in the subsurface. Initial experiments successfully tested the concept that Fe-reducing bacteria such as Geobacter sp. could enzymatically reduce soluble U(VI) to insoluble U(IV) during in situ electron donor amendment (Anderson et al. 2003, Williams et al. 2011). In parallel, in situ desorption tracer tests using bicarbonate amendment demonstrated rate-limited U(VI) desorption (Fox et al. 2012). These results and prior laboratory studies underscored the importance of enzymatic U(VI)-reduction and suggested the ability to combine desorption and bioreduction of U(VI). Here we report the results of a new field experiment in which bicarbonate-promoted uranium desorption and acetate amendment were combined and compared to an acetate amendment-only experiment in the same experimental plot. Results confirm that bicarbonate amendment to alluvial aquifer desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, that the rate of acetate-promoted enzymatic U(VI) reduction was greater in the presence of added bicarbonate in spite of the increased dominance of Ca-uranyl-carbonato aqueous complexes. A model-simulated peak rate of U(VI) reduction was ~3.8 times higher during acetate-bicarbonate treatment than under acetate-only conditions. Lack of consistent differences in microbial community structure between acetate-bicarbonate and acetate-only treatments suggest that a significantly higher rate of U(VI) reduction the bicarbonate-impacted sediment may be due to a higher intrinsic rate of microbial reduction induced by elevated concentrations of the bicarbonate oxyanion. The findings indicate that bicarbonate amendment may be useful in improving the engineered bioremediation of uranium in aquifers.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1184936
- Report Number(s):
- PNNL-SA-106900; 47984; 830403000
- Journal Information:
- Geochimica et Cosmochimica Acta, 150:106-124, Journal Name: Geochimica et Cosmochimica Acta, 150:106-124
- Country of Publication:
- United States
- Language:
- English
Fate of Adsorbed U(VI) during Sulfidization of Lepidocrocite and Hematite
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journal | February 2017 |
Spatial Distribution of an Uranium-Respiring Betaproteobacterium at the Rifle, CO Field Research Site
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journal | April 2015 |
| (Tab 1) Biogeochemistry of groundwater during acetate and bicarbonate amendment to an alluvial aquifer along the Colorado River in Rifle, Colorado, USA | dataset | January 2015 |
| (Tab 2) Average signal to noise ratio (SNR) for individual microarray probes in an alluvial aquifer along the Colorado River in Rifle, Colorado, USA | dataset | January 2015 |
| (Tab 3) Signal to noise ratio (SNR) by genus for microarray probes in an alluvial aquifer along the Colorado River in Rifle, Colorado, USA | dataset | January 2015 |
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