Reactive Transport Modeling for Supporting Climate Resilience - 21276

Climate resilience is an emerging issue at contaminated sites or hazardous waste sites, since climate shift and extreme events (e.g., flooding, drought) are expected to impact ongoing remediation or closure strategies. In this study, we develop a reactive transport model of radionuclides (uranium, tritium and others) and evaluate how different precipitation scenarios under climate change will influence the contaminant plume conditions and groundwater well concentrations. The particular focus is to evaluate the two competing effects of dilution and remobilization of nitrate, tritium, uranium dioxide, and pH in the increasing precipitation and cap failure scenarios, as well as the effect of geochemistry and sorption with changing pH. In addition, we develop the workflow to include the downscaled climate projection data from CMIP5 (Coupled Model Intercomparison Project) climate model ensembles in to the models, and evaluate residual contamination evolves by the end of the 21. century under four climate Representative Concentration Pathway (RCP) scenarios. We demonstrate our approach using the two-dimensional reactive transport models of uranium and several radionuclides models developed for the Savannah River Site F-Area, including mineral reaction and sorption processes. We consider different precipitation scenarios, by perturbing the infiltration rate from the base case, representing increasing precipitation, cap failure and climate projection scenarios. We used the reactive transport simulation software Amanzi developed under the Department of Energy Office of Environmental Management, which provides a flexible and extensible parallel flow and reactive transport simulation capability for environmental applications using the high-performance computing platform. The integration of climate modeling data and hydro-geochemistry models enables us to quantify the climate change impacts, assist remediation efforts and guide site management. (authors)