Use of chemical and isotopic tracers to characterize the interactions between ground water and surface water in mantled karst

In the mantled karst terrane of northern Florida, the water quality of the Upper Floridan aquifer is influenced by the degree of connectivity between the aquifer and the surface. Chemical and isotopic analyses [¹⁸O/¹⁶O (δ¹⁸O), ²H/¹H (δD), ¹³C/¹²C (δ¹³C), tritium (³H), and strontium‐87/strontium‐86 (⁸⁷Sr/⁸⁶Sr)] along with geochemical mass‐balance modeling were used to identify the dominant hydrochemical processes that control the composition of ground water as it evolves downgradient in two systems. In one system, surface water enters the Upper Floridan aquifer through a sinkhole located in the Northern Highlands physiographic unit. In the other system, surface water enters the aquifer through a sinkhole lake (Lake Bradford) in the Woodville Karst Plain. Differences in the composition of water isotopes (δ¹⁸O and