Stimulation of Microbially Mediated Chromate Reduction in Alkaline Soil-Water Systems

Abstract

Acetate was added to two closed soil-water systems that are representative of the subsurface environment close to chromium ore processing residue disposal sites; one had a pH of 7.7, the other 9.3. Cr(VI) reduction occurred in both systems as part of a cascade of microbially mediated terminal electron-accepting processes, occurring between nitrate and iron reduction. Cr(VI) and subsequently iron reduction took longer to start and were slower in the more alkaline system. At the point when Cr(VI) reduction was essentially complete, the microbial populations in both systems showed an increase in species closely related to β-proteobacteria that are capable of nitrate reduction.

Keywords:

• chromate
• biostimulation
• contaminated land
• nitrate-reduction
• iron-reduction
• alkaline COPR

Acknowledgments

This work was partially funded by a 2005/R2 Royal Society Research Grant. The authors would like to thank Dr. Alison Baker, Reader in the Faculty of Biological Sciences, University of Leeds, and all the members of her research group for their invaluable advice and assistance with the molecular biology work reported in this paper. The first author would also like to thank Dr. Julia Bailey-Serres, Professor of Genetics, Department of Botany and Plant Sciences, University of California Riverside, and all the members of her research group for generously giving their time and resources to teach him the basics of molecular biology.

Notes

⁺ After (Langmuir 1997).

* Calculated using thermodynamic data from (Stumm and Morgan 1996).

^× Calculated using thermodynamic data from (Thauer et al. 1977).

* The BLAST E-value indicates the likelihood that a match has arisen by chance.