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Electron flow in acidic subsurface sediments co-contaminated with nitrate and uranium

Title data

Edwards, Lainie ; Küsel, Kirsten ; Drake, Harold L. ; Kostka, Joel E.:
Electron flow in acidic subsurface sediments co-contaminated with nitrate and uranium.
In: Geochimica et Cosmochimica Acta. Vol. 71 (2007) Issue 3 . - pp. 643-654.
ISSN 0016-7037
DOI: https://doi.org/10.1016/j.gca.2006.09.017

Abstract in another language

The combination of low pH and high concentrations of nitrate and radionuclides in the subsurface is representative of many sites within the U.S. nuclear weapons complex managed by the Department of Energy (DOE), including the DOE’s Environmental Remediation Sciences Program Field Research Center (ORFRC), in Oak Ridge, Tennessee. In order to provide a further understanding of the coupled microbiological and geochemical processes limiting radionuclide bioremediation, we determined the rates and pathways of terminal-electron accepting processes (TEAPs) in microcosm experiments using close to in situ conditions with ORFRC subsurface materials. At the in situ pH range of 4–5, carbon substrate utilization and TEAP rates were diminished, such that nitrate was not depleted and metal reduction was prevented. Upon biostimulation by pH neutralization and carbon substrate addition, TEAPs were stimulated to rates that rival those measured in organic-rich surficial sediments of aquatic environments, and extremely high nitrate concentrations (0.4–0.5 M) were not found to be toxic to microbial metabolism. Metal reduction under neutral pH conditions started once nitrate was depleted to low levels in response to biostimulation. Acidity controlled not only the rates but also the pathways of microbial activity. Denitrification predominated in sediments originating from neutral pH zones, while dissimilatory nitrate reduction to ammonium occurred in neutralized acidic microcosms amended with glucose. Electron donors were determined to stimulate microbial metabolism leading to metal reduction in the following order: glucose > ethanol > lactate > hydrogen. In microcosms of neutralized acidic sediments, 80–90% of C equivalents were recovered as fermentation products, mainly as acetate. Due to the stress imposed by low pH on microbial metabolism, our results indicate that the TEAPs of acidic subsurface sediment are inherently different from those of neutral pH environments and neutralization will be necessary to achieve sufficient metabolic rates for radionuclide remediation.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER37712
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology > Chair Ecological Microbiology
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Biology
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 29 Jul 2015 05:53
Last Modified: 29 Jul 2015 05:53
URI: https://eref.uni-bayreuth.de/id/eprint/17394