Water Resources Research Act Program

Details for Project ID 2007KY90B

Chemical Evolution of Groundwater in the Wilcox Aquifer of the Mississippi Embayment

Institute: Kentucky
Year Established: 2007 Start Date: 2007-03-01 End Date: 2008-02-29
Total Federal Funds: $5,000 Total Non-Federal Funds: $11,058

Principal Investigators: Alan Fryar

Project Summary: Clastic sedimentary aquifers are major sources of groundwater in many parts of the USA, including the Jackson Purchase region of Kentucky. In general, water quality is good and yield is high from regional clastic aquifers. However, groundwater from confined clastic aquifers commonly has high iron concentrations, thus necessitating treatment, and these aquifers are also prone to overexploitation. Effective management depends in part on understanding the controls on water quality in these aquifers. We intend to assess the processes controlling water quality in the Wilcox aquifer of the northern Gulf Coastal Plain. The most rigorous studies of sodium bicarbonate waters, which have integrated isotopic data with geochemical modeling, have focused on aquifers in the Atlantic Coastal Plain. The proposed study would test whether the mechanisms inferred there occur in our region. We hypothesize that the following processes combine to drive chemical evolution: (1) dissolution of carbon dioxide and other solutes in the unsaturated zone; (2) weathering of feldspars to form clay minerals; (3) cation exchange; (4) bacterial oxidation of sedimentary organic matter (SOM) coupled to sequential reduction of dissolved oxygen, nitrate, Mn(IV), Fe(III), and sulfate along the flow path; (5) dissolution and precipitation of calcite; (6) precipitation of pyrite (iron sulfide); and (7) diffusion and advection of solutes from interbeds within the Wilcox and adjoining strata.