Microbially mediated kinetic sulfur isotope fractionation: reactive transport modeling benchmark

Cheng, Yiwei
Arora, Bhavna
Şengör, Sema Sevinç
Druhan, Jennifer L.
Wanner, Christoph
van Breukelen, Boris M.
Steefel, Carl
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 ((SO42-)-O-32) over the heavier isotopologue ((SO42-)-O-34). 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.


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Fate and transport of heavy metals is controlled by the biogeochemical processes in the environment. Reactive transport modeling is particularly important for capturing the complex interplay between the microbial community dynamics and redox-stratified environments. The focus of this study is to investigate the impacts of (i) multicomponent diffusion (MCD) and (ii) electrical double layer (EDL) on reactive diffusive transport of heavy metals at Lake Coeur d'Alene (LCdA) sediments. The solute benthic fluxes ...
Citation Formats
Y. Cheng et al., “Microbially mediated kinetic sulfur isotope fractionation: reactive transport modeling benchmark,” COMPUTATIONAL GEOSCIENCES, pp. 0–0, 2020, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/41007.