Stable Isotopic Investigation of the Hydrological Cycle of West-Central Florida

Author

Toedsit Netratanawong, University of South FloridaFollow

Graduation Year

1995

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Materials Science

Degree Granting Department

Marine Science

Major Professor

William M. Sackett, Ph.D.

Committee Member

Sam B. Upchurch, Ph.D .

Committee Member

Robert H . Byrne, Ph .D.

Committee Member

Kent A. Fanning, Ph.D.

Committee Member

Edward S. VanVleet, Ph .D.

Abstract

Stable isotopic compositions of oxygen, carbon, and hydrogen were used to identify the sources of water and of organic matter, pathway reactions, evaporation processes, and transfer mechanisms among various water types as well as the extent of water-rock reactions. An attempt to understand the isotopic compositions of the hydrological cycle of west-central Florida, their variations, baseline levels and controlling mechanisms constitutes parts of this dissertation.

A comparison of δ¹⁸O in rainwater (weighted mean = -4.4 o/oo) and surficial ground water (mean = -4.1 o/oo) indicates that rainwater recharges the surficial aquifer with only a minor isotopic change. δ¹⁸O vs δD plots of rainwater and ground waters suggest that recently recharged water in the upper Floridan aquifer is similar to today's rainwater. As shown by calculations, carbonate aquifers react extensively with the ground waters in the upper Floridan aquifer through time to cause a shift of δ¹⁸O from -4.4 to -2.8 o/oo. Changes in δ¹⁸O and δ₁₃C_DIC in ground waters of the upper Floridan aquifer in two flow paths suggest that the confined nature of the aquifer causes the difference. Parts of the upper Floridan aquifer supply freshwater to rivers discharging into Tampa Bay as evidenced by similarities in δ¹⁸0 and δ¹³C_DIC of both freshwater types. Evaporation may play a role in shifting the δ¹⁸O of rivers from ground-water source of -2.8 o/oo to -2.3 o/oo.

δ¹⁸O and δ¹³C in Tampa-Bay water correlate linearly with salinity. Based on isotopic mass balance calculations, the replacement time of Tampa-Bay water is about 67 days. Mirror Lake has invariant δ¹⁸O during a one-year study, and has a calculated replacement time for its water of 43 days.

Scholar Commons Citation

Netratanawong, Toedsit, "Stable Isotopic Investigation of the Hydrological Cycle of West-Central Florida" (2023). USF Tampa Graduate Theses and Dissertations.
https://digitalcommons.usf.edu/etd/9837