Timing the onset of sulfate reduction over multiple subsurface acetate amendments by measurement and modeling of sulfur isotope fractionation

Jennifer Druhan, Carl I. Steefel, Sergi Molins, Kenneth H. Williams, Mark E. Conrad, Donald J. Depaolo

Research output: Contribution to journalArticle

Abstract

Stable isotope fractionations of sulfur are reported for three consecutive years of acetate-enabled uranium bioremediation at the US Department of Energy's Rifle Integrated Field Research Challenge (IFRC) site. The data show a previously undocumented decrease in the time between acetate addition and the onset of sulfate reducing conditions over subsequent amendments, from 20 days in the 2007 experiment to 4 days in the 2009 experiment. Increased sulfide concentrations were observed at the same time as δ34S of sulfate enrichment in the first year, but in subsequent years elevated sulfide was detected up to 15 days after increased δ34S of sulfate. A biogeochemical reactive transport model is developed which explicitly incorporates the stable isotopes of sulfur to simulate fractionation during the 2007 and 2008 amendments. A model based on an initially low, uniformly distributed population of sulfate reducing bacteria that grow and become spatially variable with time reproduces measured trends in solute concentration and δ34S, capturing the change in onset of sulfate reduction in subsequent years. Our results demonstrate a previously unrecognized hysteretic effect in the spatial distribution of biomass growth during stimulated subsurface bioremediation.

Original languageEnglish (US)
Pages (from-to)8895-8902
Number of pages8
JournalEnvironmental Science and Technology
Volume46
Issue number16
DOIs
StatePublished - Aug 21 2012
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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