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Dating of shallow groundwater: Comparison of the transient tracers 3H/3He, chlorofluorocarbons, and 85Kr

Brenda Ekwurzel·Peter Schlosser·William M. Smethie·Niel Plummer·Eurybiades Busenberg·Robert L. Michel·Ralf Weppernig·Martin Stute
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Abstract

This paper describes a direct comparison of apparent ages derived from 3 H/ 3 He, chlorofluorocarbons (CCl 3 F and CCl 2 F 2 ), and 85 Kr measurements in shallow groundwater. Wells chosen for this study are completed in the unconfined surficial aquifers in late Cenozoic Atlantic Coastal Plain sediments of the Delmarva Peninsula, on the east coast of the United States. Most of the apparent tracer ages agree within 2 years of each other for recharge dates between 1965 and 1990. Discrepancies in apparent tracer ages usually can be explained by hydrological processes such as mixing in a discharge area. Recharge rate calculations based on apparent tracer age gradients at multilevel well locations agree with previous recharge estimates. High recharge rates on the Delmarva Peninsula result in nearly complete dissolved-gas confinement in the groundwater. The remarkable agreement between the different tracer ages indicates negligible mixing of waters of different ages, insignificant dispersion, minimal gas loss to the atmosphere, and insignificant sorption-desorption processes at this location.

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Brenda Ekwurzel, Peter Schlosser, William M. Smethie, Niel Plummer, Eurybiades Busenberg, Robert L. Michel, Ralf Weppernig, Martin Stute. 2010-07-09. Dating of shallow groundwater: Comparison of the transient tracers 3H/3He, chlorofluorocarbons, and 85Kr. https://doi.org/10.1029/94wr00156

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