Experimentally Determined Uranium Isotope Fractionation During Reduction of Hexavalent U by Bacteria and Zero Valent Iron
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- 作者：Laura K. Rademacher ; Craig C. Lundstrom ; Thomas M. Johnson ; Robert A. Sanford ; Juanzho Zhao ; Zhaofeng Zhang
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：November 15, 2006
- 年：2006
- 卷：40
- 期：22
- 页码：6943 - 6948
- 全文大小：127K
- 年卷期：v.40,no.22(November 15, 2006)
- ISSN：1520-5851
文摘
Variations in stable isotope ratios of redox sensitiveelements are often used to understand redox processesoccurring near the Earth's surface. Presented hereare measurements of mass-dependent U isotope fractionationinduced by U(VI) reduction by zerovalent iron (Fe0) andbacteria under controlled pH and HCO3- conditions. In abioticexperiments, Fe0 reduced U(VI), but the reaction failedto induce an analytically significant isotopic fractionation.Bacterial reduction experiments using Geobacter sulfurreducens and Anaeromyxobacter dehalogenans reduceddissolved U(VI) and caused enrichment of 238U relativeto 235U in the remaining U(VI). Enrichment factors (
) calculatedusing a Rayleigh distillation model are -0.31” and-0.34” for G. sulfurreducens and A. dehalogenans,respectively, under identical experimental conditions.Further studies are required to determine the range ofpossible values for 238U/235U fractionation factors under avariety of experimental conditions before broad applicationof these results is possible. However, the measurablevariations in 
238U show promise as indicators of reductionfor future studies of groundwater contamination, geochronology, U ore deposit formation, and U biogeochemicalcycling.
) calculatedusing a Rayleigh distillation model are -0.31” and-0.34” for G. sulfurreducens and A. dehalogenans,respectively, under identical experimental conditions.Further studies are required to determine the range ofpossible values for 238U/235U fractionation factors under avariety of experimental conditions before broad applicationof these results is possible. However, the measurablevariations in 238U show promise as indicators of reductionfor future studies of groundwater contamination, geochronology, U ore deposit formation, and U biogeochemicalcycling.