A flow-through cell experiment was conducted to evaluate Zn isotope fractionation during ZnS precipitation under microbially-mediated sulfate-reducing conditions. Synthetic groundwater containing 0.90 mM Zn was pumped through a cell containing creek sediment that was biostimulated to promote sulfate reducing conditions. Real-time, in situ X-ray absorption spectroscopy (XAS) was applied at the Zn K-edge to collect spectra via a Kapton® window in the front of the cell over the course of the experiment. Aqueous effluent samples were collected and analysed to determine concentrations of anions and cations, and Zn isotope ratios. The flow rate was increased step-wise during the experiment to modify the residence time and produce changes in the extent of sulfate reduction, which in turn controlled the extent of ZnS precipitation. Greater enrichment in the heavier isotope in the aqueous phase relative to the input solution was associated with more extensive Zn removal. A Rayleigh curve was fit to the isotope data, where ε = −0.27 ± 0.06‰ (2σ). Evaluation of Zn isotope fractionation under controlled flow conditions is critical to improve the efficacy of this powerful analytical technique when applied to natural systems or remediation projects in the field.
Jamieson-Hanes, J. H., Shrimpton, H. K., Veeramani, H., Ptacek, C. J., Lanzirotti, A., Newville, M., & Blowes, D. W. (2017). Evaluating zinc isotope fractionation under sulfate reducing conditions using a flow-through cell and in situ XAS analysis. Geochimica et Cosmochimica Acta, 203, 1–14. https://doi.org/10.1016/j.gca.2016.12.034