11/22/2010

Interactions of Bacteria with Uranium in the Environment

Summary

Uranium in the 6+ oxidation state is quite soluble and can thus move rapidly in uranium-contaminated subsurface environments. In contrast, uranium in the 4+ state is highly insoluble, and is therefore less likely to move the subsurface environment. New research has identified important aspects of how bacteria reduce uranium 6+ to uranium 4+, showing that the latter is produced in a variety of forms, not just in the expected, simple form of uraninite (UO2). The authors of the new study used a variety of techniques at the Stanford Synchrotron Radiation Lightsource (SSRL) to characterize the products of uranium reduction in various microbial cultures, including x-ray absorption spectroscopy (XAS). The XAS experiments showed that many of the uranium 4+ products lacked the spectral peak characteristic of uraninite. Instead, a variety of complex solids involving uranium and phosphate, and in some cases also calcium were identified, as well as solids in which uranium 4+ is bound to the surface of the bacterial biomass. These results will be helpful in modeling the mobility of uranium species at contaminated DOE sites. The research was led by Rizlan Bernier-Latmani of the École Polytechnique Fédérale de Lausanne in Switzerland, and involved scientists at SSRL. It is just published online in Environmental Science & Technology.

References

Bernier-Latmani, R., et al. 2010. “Non-uraninite Products of Microbial U(VI) Reduction,” Environmental Science & Technology, online November 11, 2010. DOI: 10.1021/es101675a.