Integration of Innovative Techniques to Improve Prediction and Remediation of Groundwater Contamination

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The long-term goal of my research program is to develop improved techniques for the prediction, remediation, and prevention of groundwater contamination derived from mine sites, industrial sites, and other sources of contamination. My research includes determination of the physical and solute-transport characteristics of groundwater flow systems, measurements of the concentration and speciation of dissolved constituents, identification of primary and secondary phases controlling the concentrations of dissolved constituents, and characterization of the microbiological communities involved in metal and nutrient cycling. The systems we study are complex, making it challenging to develop well-constrained predictions. We are currently exploring the use of non-traditional isotope measurements, synchrotron-based spectroscopic techniques, next-generation sequencing of microbial populations, and reactive transport modelling to enhance our understanding of the hydrogeology and biogeochemistry of contaminated sites and remediation systems. Integrating these techniques will provide additional constraints on reactive transport simulations. We will conduct a series of highly-constrained (constant T, P, PO2, PCO2) laboratory experiments to determine the extent of isotope fractionation associated with adsorption, reduction-oxidation, and precipitation of carbonate, hydroxide, phosphate, and sulfide phases containing Cu, Fe, Ni, Se, and Zn, and hydroxide phases containing Cr. The reaction products from these experiments will be analyzed using synchrotron X-ray absorption spectroscopy (XAS) to determine oxidation state and structure. In addition, we will conduct flow-through cell experiments at synchrotron facilities to monitor changes in oxidation state and corresponding changes in isotope ratios under steady water-flow. This approach will provide measurements of the reaction mechanism, reaction rate, reaction progress, and isotope fractionation at an unprecedented level of detail. The microbial community present in the flow-through cell will be characterized using molecular approaches. Combining non-traditional isotope-ratio measurements, with synchrotron-based characterization of reaction processes and reaction products, and characterization of microbial community structure, will provide a strong foundation for numerical modelling, and improved assessments of the extent and duration of environmental contamination, and the effectiveness and longevity of remediation systems.