Oxidative Dissolution of Biogenic Uraninite in Groundwater at Old Rifle, CO

详细信息    查看全文

• 作者：Kate M. Campbell ; Harish Veeramani ; Kai-Uwe Ulrich ; Lisa Y. Blue ; Daniel E. Giammar ; Rizlan Bernier-Latmani ; Joanne E. Stubbs ; Elena Suvorova ; Steve Yabusaki ; Juan S. Lezama-Pacheco ; Apurva Mehta ; Philip E. Long ; John R. Bargar
• 刊名：Environmental Science & Technology
• 出版年：2011
• 出版时间：October 15, 2011
• 年：2011
• 卷：45
• 期：20
• 页码：8748-8754
• 全文大小：821K
• 年卷期：v.45,no.20(October 15, 2011)
• ISSN：1520-5851

文摘

Reductive bioremediation is currently being explored as a possible strategy for uranium-contaminated aquifers such as the Old Rifle site (Colorado). The stability of U(IV) phases under oxidizing conditions is key to the performance of this procedure. An in situ method was developed to study oxidative dissolution of biogenic uraninite (UO₂), a desirable U(VI) bioreduction product, in the Old Rifle, CO, aquifer under different variable oxygen conditions. Overall uranium loss rates were 50鈥?00 times slower than laboratory rates. After accounting for molecular diffusion through the sample holders, a reactive transport model using laboratory dissolution rates was able to predict overall uranium loss. The presence of biomass further retarded diffusion and oxidation rates. These results confirm the importance of diffusion in controlling in-aquifer U(IV) oxidation rates. Upon retrieval, uraninite was found to be free of U(VI), indicating dissolution occurred via oxidation and removal of surface atoms. Interaction of groundwater solutes such as Ca²⁺ or silicate with uraninite surfaces also may retard in-aquifer U loss rates. These results indicate that the prolonged stability of U(IV) species in aquifers is strongly influenced by permeability, the presence of bacterial cells and cell exudates, and groundwater geochemistry.