Marine, 1979; Andrews and Lee, 1979; Torgersen, 1980; Stue et al., 1992).If the solid-to-liquid mass transfer rate is governed by the radioactive decay of U and Th, significant (i.e.Once water enters an aquifer, it becomes isolated from the atmosphere, and it carries a CFC signature (a distinctive chemical composition) as it travels through the aquifer.
In addition to dating waters, -decay of natural U- and Th-series elements in rocks and sediments.Mass transfer between aquifer solids and ground water occurs, resulting in a relationship between ground-water travel time (or contact time) and the He as a quantitative tracer of ground-water travel times (e.g.Groundwater age is usually defined as the time between recharge at the water table to the time when groundwater was sampled.Groundwater age estimates are based on concentrations of environmental tracers (i.e., tracers derived from the atmosphere, as opposed to artificial tracers) in groundwater.Hydrologists employ a variety of techniques to measure groundwater age.
For relatively young groundwater, chlorofluorocarbons (CFCs) often are used.
CFCs can be used to determine groundwater age because water that is in contact with the atmosphere picks up CFCs from the atmosphere.
Thus, CFCs are incorporated in the water before it enters an aquifer.
Once this water reaches the water table, it moves though the aquifer.
The time it takes to travel to a given location, known as the groundwater age, can vary from days to thousands of years.
In the case of a fluctuating water table, t = 0 is set at the seasonal low water table position (Solomon et al., 1993).