Chemical Variation in Groundwater Composition with Depth through a LithologicallyHeterogeneous Carbonate Aquifer System

摘要

Twenty-nine groundwater samples and a continuous rock core collected throughFlorida's Intermediate aquifer system (IAS) were studied to evaluate the influence of changing mineralogic and hydrologic properties on the water composition of a lithologically heterogeneous carbonate aquifer. Continguous clay units are common in the aquifer. The resulting mineralogic and permeability constrasts between these units and the enclosing carbonates creates significant variation in the groundwater composition. The rock core and water samples were collected from a Miocene coastal aquifer that overlies the Floridan aquifer in west-central Florida. At the sampling location in Osprey, Florida, in Sarasota County, the aquifer extends from 33 m to 159 m below land surface. The structure of the aquifer system is influenced by a 17-m thick clay unit that separates two thicker carbonate sequences.