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Enhancing microbial iron reduction in hyperalkaline, chromium contaminated sediments by pH amendment

Whittleston, RA, Stewart, DI, Mortimer, RJG and Burke, IT (2013) Enhancing microbial iron reduction in hyperalkaline, chromium contaminated sediments by pH amendment. Applied Geochemistry, 28. pp. 135-144. ISSN 0883-2927


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Soil collected from beneath a chromite ore processing residue (COPR) disposal site contained a diverse population of anaerobic alkaliphiles, despite receiving a continuous influx of a Cr(VI) contaminated, hyperalkaline leachate (pH 12.2). Chromium was found to have accumulated in this soil as a result of an abiotic reaction of Cr(VI) with Fe(II) present in the soil. This sediment associated Fe(II) was therefore acting as a natural reactive zone beneath the COPR and thereby preventing the spread of Cr(VI). In anaerobic microcosm experiments soil microorganisms were able to reduce nitrate at pH 11.2 coupled to the oxidation of electron donors derived from the original soil organic matter, but progressive anoxia did not develop to the point of iron reduction over a period of 9 months. It is not clear, therefore, if Fe(II) can be actively replenished by microbial processes occurring within the soil at in situ conditions. Sodium bicarbonate was added to this soil to investigate whether bioreduction of iron in hyperalkaline chromium contaminated soils could be enhanced by reducing the pH to a value optimal for many alkaliphilic bacteria. The addition of sodium bicarbonate produced a well buffered system with a pH of ~9.3 and iron reducing conditions developed within 1 month once complete denitrification had occurred. Iron(III) reduction was associated with an increase in the proportion of genetic clone libraries that were from the phylum Firmicutes, suggesting that these species are responsible for the Fe(III) reduction observed. Amendment of the pH using bicarbonate may provide a suitable strategy for stimulating the bioreduction of Fe(III) in COPR leachate contaminated soils or other environments where microbial reduction is inhibited by elevated pH.

Item Type: Article
Copyright, Publisher and Additional Information: © 2012, Elsevier. This is an author produced version of a paper accepted for publication in Applied Geochemistry. Uploaded in accordance with the publisher's self-archiving policy.
Keywords: Chromium; alkaline
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds)
Depositing User: Symplectic Publications
Date Deposited: 15 Nov 2012 11:03
Last Modified: 13 Jul 2016 06:46
Published Version: http://dx.doi.org/10.1016/j.apgeochem.2012.10.003
Status: Published
Publisher: Elsevier
Identification Number: 10.1016/j.apgeochem.2012.10.003
URI: http://eprints.whiterose.ac.uk/id/eprint/74738

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