Experimentally determined uranium isotope fractionation during reduction of hexavalent U by bacteria and zero valent iron

Laura K. Rademacher, Craig Campbell Lundstrom, Thomas Martin Johnson, Robert A Sanford, Juanzho Zhao, Zhaofeng Zhang

Research output: Contribution to journalArticle

Abstract

Variations in stable isotope ratios of redox sensitive elements are often used to understand redox processes occurring near the Earth's surface. Presented here are measurements of mass-dependent U isotope fractionation induced by U(VI) reduction by zerovalent iron (Fe 0) and bacteria under controlled pH and HCO 3 - conditions. In abiotic experiments, Fe 0 reduced U(VI), but the reaction failed to induce an analytically significant isotopic fractionation. Bacterial reduction experiments using Geobacter sulfurreducens and Anaeromyxobacter dehalogenans reduced dissolved U(VI) and caused enrichment of 238U relative to 235U in the remaining U(VI). Enrichmentfactors (ε) calculated using 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 of possible values for 238U/ 235U fractionation factors under a variety of experimental conditions before broad application of these results is possible. However, the measurable variations in δ 238U show promise as indicators of reduction for future studies of groundwater contamination, geochronology, U ore deposit formation, and U biogeochemical cycling.

Original languageEnglish (US)
Pages (from-to)6943-6948
Number of pages6
JournalEnvironmental Science and Technology
Volume40
Issue number22
DOIs
StatePublished - Nov 15 2006
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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