Solubilization of Plutonium Hydrous Oxide by Iron-Reducing Bacteria

Abstract

The removal of plutonium from soils id challenging because of its strong sorption to soils and limited solubility, Microbial reduction of metals is known to affect the speciation and solubility of sparingly soluble metals in the environment, notably iron and manganese. The similarity in reduction potential for [alpha]-FeOOH(s) and hydrous PuO[sub 2](s) suggests that iron-reducing bacteria may also reduce and solubilize plutonium. Bacillus strains were used to demonstrate that iron-reducing bacteria mediate the solubilization of hydrous PuO[sub 2](s) under anaerobic conditions. Up to [approximately]90% of the PuO[sub 2] was biosolubilized in the presence of nitrilotriacetic acid (NTA) within 6-7 days. Biosolubilization occurred to a lesser extent ([approximately] 40%) in the absence of NTA. Little PuO[sub 2] solubilization occurred in sterile culture media or in the presence of a non-iron-reducing Escherichia coli. These observations suggest a potentially attractive, environmentally benign strategy for the remediation of Pu-contaminated soils. 26 refs., 5 figs., 2 tabs.