Trace Element Geochemistry In Groundwater Flow Systems

This research focuses on trace element geochemistry in three groundwater flow systems: the Carrizo Sand, the Upper Floridan, and the Aquia aquifers. The focus is threefold: (i) studying the geochemical behavior, concentrations, and fractionation patterns of rare earth elements (REEs) along two flow paths by examination of both groundwater and sediment samples, (ii) investigating the behavior of arsenic (As) and antimony (Sb) and comparing these data to reveal the biogeochemical processes affecting As and Sb concentrations and speciation as well as determining correlations between As and Sb concentrations, and (iii) formulating adsorption isotherms to demonstrate the adsorption capacity of As onto sediments from the Carrizo Sand and Aquia aquifers. The investigation of the Aquia aquifer groundwaters and sediments indicated the chief source of REEs in the groundwater was due to the dissolution of carbonate minerals (i.e. shell fragments). A statistical relationship was found between As and Sb in the groundwaters of three well defined aquifers (the Carrizo Sand, the Upper Floridan, and the Aquia aquifers), with the best correlation occurring within the Aquia groundwaters. The adsorption isotherms indicate that As(V) strongly adsorbs to the Carrizo Sand aquifer sediments whereas As(III) more preferentially adsorbs to the Aquia aquifer sediments.