TY - JOUR
T1 - Bicarbonate impact on U(VI) bioreduction in a shallow alluvial aquifer
AU - Long, Philip E.
AU - Williams, Kenneth H.
AU - Davis, James A.
AU - Fox, Patricia M.
AU - Wilkins, Michael J.
AU - Yabusaki, Steven B.
AU - Fang, Yilin
AU - Waichler, Scott R.
AU - Berman, Elena S.F.
AU - Gupta, Manish
AU - Chandler, Darrell P.
AU - Murray, Chris
AU - Peacock, Aaron D.
AU - Giloteaux, Ludovic
AU - Handley, Kim M.
AU - Lovley, Derek R.
AU - Banfield, Jillian F.
N1 - Funding Information:
This work was supported by the Director, Office of Science, Biological and Environmental Research, Subsurface Biogeochemistry Program of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231 . We thank the entire Rifle, Colorado Integrated Field Challenge (IFRC) team for their contributions to the Super 8 Experiment, including the U.S. Department of Energy, Grand Junction Office for their excellent field support. We also thank Jason Greenwood for assistance with Fig. 1 , Roelof Versteeg for help with uploading data to Pangaea, and anonymous Reviewer #2 for extensive, detailed and very helpful comments that significantly improved the manuscript.
Publisher Copyright:
© 2014 Elsevier Ltd.
PY - 2015/2/1
Y1 - 2015/2/1
N2 - 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 sediments desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, 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 in 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.
AB - 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 sediments desorbs U(VI) and increases the abundance of Ca-uranyl-carbonato complexes. At the same time, 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 in 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.
UR - http://www.scopus.com/inward/record.url?scp=84922702726&partnerID=8YFLogxK
U2 - 10.1016/j.gca.2014.11.013
DO - 10.1016/j.gca.2014.11.013
M3 - Article
AN - SCOPUS:84922702726
SN - 0016-7037
VL - 150
SP - 106
EP - 124
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -