adult dating brooklyn ohio - Environmental tracers age dating young groundwater
Recognizing the limitations of these methods and driven, in part, by the need for more detailed age information, additional environmental tracers have been sought that can provide information on the age of "young groundwater".
Here, "young groundwater" refers to water recharged within approximately the past 50 years, a time scale defined largely by the dating range of a small group of environmental tracers that encompasses, at least in part, groundwater that has potentially been impacted by anthropogenic contamination.
The term "groundwater age" is used to refer to the time elapsed since recharge, and, although reference is often made to "dating of groundwater", it is important to recognize that what is actually being "dated" is a dissolved solute, or dissolved gas, or isotope that has an atmospheric origin, and has been transported through the unsaturated zone, into and through the aquifer to the point of sampling.
While it is often possible to measure reliably the concentrations of environmental tracers in groundwater samples, groundwater age is model-dependent, being based on an interpretation of the recharge mechanism, groundwater flow conditions and other physical and geochemical processes that may have affected the concentrations measured in the sample.
Environmental tracers that have proven most useful in providing groundwater age information can be grouped according to their systematics: (1) methods based on the measurement of the activity of a single radionuclide of atmospheric origin in groundwater, such as in applications of 3H, 85Kr, 39Ar, 32Si, and 35S in groundwater dating, (2) the 3H/3He method, which is based on measurement of the concentrations of both parent and daughter isotopes in groundwater, and (3) methods based on measurement of the concentrations of atmospheric gases of anthropogenic origin in groundwater, such as in applications of chlorofluorocarbons (CFCs) and sulphur hexafluoride (SF6).