Microbial U Isotope Fractionation Depends on the U(VI) Reduction Rate

Anirban Basu, Christoph Wanner, Thomas M. Johnson, Craig C. Lundstrom, Robert A. Sanford, Eric L. Sonnenthal, Maxim I. Boyanov, Kenneth M. Kemner

Research output: Contribution to journalArticle

Abstract

U isotope fractionation may serve as an accurate proxy for U(VI) reduction in both modern and ancient environments, if the systematic controls on the magnitude of fractionation (ϵ) are known. We model the effect of U(VI) reduction kinetics on U isotopic fractionation during U(VI) reduction by a novel Shewanella isolate, Shewanella sp. (NR), in batch incubations. The measured ϵ values range from 0.96 ± 0.16 to 0.36 ± 0.07‰ and are strongly dependent on the U(VI) reduction rate. The ϵ decreases with increasing reduction rate constants normalized by cell density and initial U(VI). Reactive transport simulations suggest that the rate dependence of ϵ is due to a two-step process, where diffusive transport of U(VI) from the bulk solution across a boundary layer is followed by enzymatic reduction. Our results imply that the spatial decoupling of bulk U(VI) solution and enzymatic reduction should be taken into account for interpreting U isotope data from the environment.

Original languageEnglish (US)
Pages (from-to)2295-2303
Number of pages9
JournalEnvironmental Science and Technology
Volume54
Issue number4
DOIs
StatePublished - Feb 18 2020

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ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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