Bioreduction of Uranium: Environmental Implications of a Pentavalent Intermediate

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• 作者：Joanna C. Renshaw ; Laura J. C. Butchins ; Francis R. Livens ; Iain May ; John M. Charnock ; and Jonathan R. Lloyd
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：August 1, 2005
• 年：2005
• 卷：39
• 期：15
• 页码：5657 - 5660
• 全文大小：201K
• 年卷期：v.39,no.15(August 1, 2005)
• ISSN：1520-5851

文摘

The release of uranium and other transuranics into theenvironment, and their subsequent mobility, are subjectsof intense public concern. Uranium dominates the inventoryof most medium- and low-level radioactive waste sitesand under oxic conditions is highly mobile as U(VI), thesoluble uranyl dioxocation {UO₂}²⁺. Specialist anaerobicbacteria are, however, able to reduce U(VI) to insoluble U(IV),offering a strategy for the bioremediation of uranium-contaminated groundwater and a potential mechanism forthe biodeposition of uranium ores. Despite the environmentalimportance of U(VI) bioreduction, there is little informationon the mechanism of this transformation. In the courseof this study we used X-ray absorption spectroscopy (XAS)to show that the subsurface metal-reducing bacteriumGeobacter sulfurreducens reduces U(VI) by a one-electronreduction, forming an unstable {UO₂}⁺ species. Thefinal, insoluble U(IV) product could be formed either throughfurther reduction of U(V) or through its disproportionation.When G. sulfurreducens was challenged with thechemically analogous {NpO₂}⁺, which is stable withrespect to disproportionation, it was not reduced, suggestingthat it is disproportionation of U(V) which leads to theU(IV) product. This surprising discrimination between Uand Np illustrates the need for mechanistic understandingand care in devising in situ bioremediation strategies forcomplex wastes containing other redox-active actinides,including plutonium.