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As with any environmental tracer, age applies to the date of introduction of the chemical substance into the water, and not to the water itself.
The accuracy of the determined age depends in part on how perfectly the CFCs are transported with the water.
These atmospheric substances, such as tritium (H) in water vapor from detonation of nuclear bombs in the 1950s and early 1960s,and chlorofluorocarbons (CFCs) from refrigeration and other uses from the 1950s through the 1980s, dissolve in precipitation, become incorporated in the Earths hydrologic cycle, and can be found in ground water that has been recharged within the past 50 years.
The detection of chlorofluorocarbons and tritium in ground water provides valuable information that can be used for dating and tracing young ground watertechniques that help water-resources managers develop management strategies for shallow ground-water systems.
CFCs have been increasingly used in oceanic studies since the late 1970s as tracers of oceanic circulation, ventilation, and mixing processes.
USGS scientists (Busenberg and Plummer, 1992) adapted analytical procedures developed by the oceanographic scientific community for ground-water studies and designed sampling equipment and procedures for collection and preservation of water samples in the field.
These problems can be overcome by using tritium in combination with its decay product He age formally calculated from equation (1) is an apparent age.
This increased reliance on the groundwater in concert with the strict regulation on water quality has led to a need by water managers and regulators to understand: Characterization of mean groundwater age and recharge temperature through the use of noble gas techniques provides information that is relevant to answering these questions and that is not accessible through traditional hydrogeologic approaches.In the early 1990s, USGS scientists (Busenberg and Plummer, 1992) developed a method to date ground water on the basis of chlorofluorocarbon (CFC) content of the water that is practical, cost-effective, and applicable to most shallow ground-water systems.Sampling for tracers The feasibility of using CFCs as tracers of recent recharge and indicators of ground-water age was first recognized in the 1970s (see Plummer and Busenberg, 1997 and references therein).Significant differences between the apparent tritium/ is mainly determined by the ratio of advection to dispersion in water parcels moving away from the water table.H), and other chemical and isotopic substances in ground water, can be used to trace the flow of young water (water recharged within the past 50 years) and to determine the time elapsed since recharge.