H031-0013
Climate Change Precipitation Impacts on Residual in situ Groundwater Contaminants
Tuesday, 8 December 2020
Poster
Rebecca Serata1, Zexuan Xu1, Haruko M Wainwright2, Sergi Molins3, Bhavna Arora4, John D Moulton5, Miles E Denham6 and Carol A Eddy-Dilek6, (1)Lawrence Berkeley National Laboratory, Climate and Ecosystem Sciences Division, Berkeley, CA, United States, (2)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (3)Lawrence Berkeley National Laboratory, Earth and Environmental Sciences, Berkeley, CA, United States, (4)Lawrence Berkeley National Laboratory, Energy Geosciences Division, Berkeley, CA, United States, (5)Los Alamos National Laboratory, Los Alamos, NM, United States, (6)Savannah River National Lab, Aiken, SC, United States
Abstract:
It is very important to evaluate how vulnerable contamination sites are to climate change and to make them more resilient. The climate in the next one hundred years will test the vulnerability of our sites. Therefore, it is important for us to develop predictive capabilities and adapt our management strategies. In cases where waste is left in place and remediation techniques such as pump and treat or cap-in-place are used, effects of flooding from extreme precipitation can lead to elevation of the water table. This can then lead to surfacing of contaminants and mobilization depending on the geochemistry. Previous studies in our group examined the impacts of the same climate change scenarios on non-reactive tracers. Cases with extreme precipitation and cap-failure are found to have increased contaminants through a pattern of dilution and then mobilization. In this study, we are using the same climate projection scenarios but in order to examine more reactive contaminants, our models take into account more complex reactive geochemistry, mineral reactions, and sorption.
In the case of low-level nuclear waste, remediation requires long-term solutions and monitoring. For Region 3, where Savannah River Site is located, the Environmental Protection Agency (EPA) predicts average temperature and rainfall will increase, as well as the frequency of extreme precipitation events. This makes it important for us to model how different precipitation scenarios will change plume conditions and the behavior of reactive tracers in the system. In this study, we address these challenges by using a reactive transport code, Amanzi, jointly developed by multiple DOE national laboratories. With Amanzi, we are able to run scenarios that describe extreme precipitation, slight increases in precipitation, and decreases in precipitation, by changing the infiltration rates. From this, we are able to determine how nitrate, tritium, uranium dioxide, and pH among other variables, change in each 100-year simulation. These simulations allow us to fully understand the complex effects of increased infiltration and what mechanisms control pH and UO2+. From our simulations, we aim to determine whether dilution is the driving force behind a pH increase and uranium decrease, or whether immobilization of uranium from pH neutralization is the main driver.
