One TU (Tritium Unit) means a tritium to hydrogen ratio of 10.
Whereas the addition of bomb tritium to the environment practically eliminated the use of natural tritium as a tracer, it offered a new tool, i.e., the use of the bomb tritium peak (Fig.
It is independent of the initial tritium concentration of the water sample which is one of the advantages of the method because it eliminates the necessity to establish the exact time- dependent tritium delivery to the aquifer.
A potential problem for the quantitative interpretation of the tritium/He age is typically biased toward the age of the water component with the higher tritium concentration.
Tritium is produced naturally in the upper atmosphere by interaction of nitrogen, and, to a lesser extent, oxygen with cosmic rays.
After oxidation to HTO, it takes part in the natural water cycle.
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.
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.
For this reason, the term age is normally qualified with the word model or apparent, that is, model age or apparent age. USGS scientists have investigated some of the most important factors that can affect CFC concentrations in ground water and the resulting age interpretations (Busenberg and Plummer, 1992; Plummer and others, 1993; Dunkle and others, 1993; Ekwurzel and others, 1994; Cook and others, 1995; Plummer and others 1998a, 1998b; Plummer and Busenberg, 1999).
These include (1) uncertainty of the temperature at the water table during recharge, (2) entrapment of excess air during recharge, (3) uncertainty in recharge elevation, (4) thickness of the unsaturated zone, (5) effect of urban air where CFC values may exceed regional values, (6) contamination from a specific local source, (7) microbial degradation (in anaerobic environments), (8) sorption onto organic and mineral surfaces, and (9) mixing of younger and older water in a well. A., 1998, Chemistry of unsaturated zone gases sampled in open boreholes at the crest of Yucca Mountain, Nevada: Data and basic concepts of chemical and physical processes in the mountain: Water Resources Research, v. For additional information, see or contact: Niel Plummer (email: [email protected]) U.
Therefore, for quantitative studies, mixing has either to be ruled out as a major factor influencing the flow regime or it has to be accounted for in the data evaluation.
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.