Microbially mediated kinetic sulfur isotope fractionation: reactive transport modeling benchmark

Yiwei Cheng, Bhavna Arora, S. Sevinç Şengör, Jennifer L. Druhan, Christoph Wanner, Boris M. van Breukelen, Carl I. Steefel

Research output: Contribution to journalArticlepeer-review


Microbially mediated sulfate reduction is a ubiquitous process in many subsurface systems. Isotopic fractionation is characteristic of this anaerobic process, since sulfate-reducing bacteria (SRB) favor the reduction of the lighter sulfate isotopologue (S32O42−) over the heavier isotopologue (S34O42−). Detection of isotopic shifts has been utilized as a proxy for the onset of sulfate reduction in subsurface systems such as oil reservoirs and aquifers undergoing heavy metal and radionuclide bioremediation. Reactive transport modeling (RTM) of kinetic sulfur isotope fractionation has been applied to field and laboratory studies. We developed a benchmark problem set for the simulation of kinetic sulfur isotope fractionation during microbially mediated sulfate reduction. The benchmark problem set is comprised of three problem levels and is based on a large-scale laboratory column experimental study of organic carbon amended sulfate reduction in soils from a uranium-contaminated aquifer. Pertinent processes impacting sulfur isotopic composition such as microbial sulfate reduction and iron-sulfide reactions are included in the problem set. This benchmark also explores the different mathematical formulations in the representation of kinetic sulfur isotope fractionation as employed in the different RTMs. Participating RTM codes are the following: CrunchTope, TOUGHREACT, PHREEQC, and PHT3D. Across all problem levels, simulation results from all RTMs demonstrate reasonable agreement.

Original languageEnglish (US)
Pages (from-to)1379-1391
Number of pages13
JournalComputational Geosciences
Issue number4
StatePublished - Aug 2021


  • Benchmark
  • Kinetic isotope fractionation
  • Microbial sulfate reduction
  • Reactive transport modeling
  • S isotopes

ASJC Scopus subject areas

  • Computer Science Applications
  • Computers in Earth Sciences
  • Computational Mathematics
  • Computational Theory and Mathematics


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