Collaborative Research: Quantifying rare earth element transport in aquifers using field, laboratory, and numerical approaches

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0126222Johannesson Groundwater is the principal source of drinking water in the United States, and represents over 68% of the world's fresh water supply. Therefore, assuring the quality of groundwater for current populations and protecting it from future contamination is of great concern. Groundwater consumption can increase the loading of specific heavy metals to our bodies, and interaction of groundwaters with buried nuclear wastes is considered the most likely release mechanism of these materials to the environment. Understanding the geochemistry of heavy metals in aquifers is critical to developing accurate solute transport models, which can be employed to predict the fate and transport of heavy metals in aquifers over time and under different environmental conditions. We seek to quantify rare earth elements (REE) concentrations and behavior along groundwater flow paths in real aquifers, and develop a coupled groundwater flow and transport model for these heavy metals. The REEs are of interest because of their potential as geochemical tracers of water-rock reactions, and because their chemical similarities to transuranics makes them attractive natural analogs for studying radioactive contaminants in aquifer. Our research objectives are: (1) To elucidate the geochemical behavior of REEs along groundwater flow paths in well characterized aquifers emphasizing their concentrations, fractionation patterns, and speciation.(2) To develop a combined surface and solution complexation model for the REEs that is specific to each aquifer, but can also be broadly applied to other systems. (3) To assemble and implement a coupled groundwater flow and reactive transport simulation model for REEs in groundwater systems. To accomplish these objectives, we will implement an integrated field, laboratory, and numerical modeling study over a period of three years. We will utilize two well characterized aquifers (i.e., Carrizo Sand, Texas; Floridan aquifer, Florida) for the field component of the project. Both are typical drinking water aquifers that represent common, albeit, compositionally different systems. The data generated in the study will be crucial for "calibrating" reactive transport models for REEs in aquifer, and will improve our general understanding of reactive solute transpor