The nucleus of tritium (sometimes called a triton) contains one proton and two neutrons, whereas the nucleus of protium (by far the most abundant hydrogen isotope) contains one proton and no neutrons.Naturally occurring tritium is extremely rare on Earth, where trace amounts are formed by the interaction of the atmosphere with cosmic rays.It is designed to permit plotting of ages and tracer concentrations in a variety of different combinations to facilitate interpretation of measurements.
Because the apparent age is a mixture of those from supra-permafrost and intra-permafrost groundwater, further analysis would be required to assess the contribution ratio of the two types of groundwater.
Excel workbooks for calculation and presentation of environmental tracer data for simple groundwater mixtures. In: IAEA Guidebook on the Use of Chlorofluocarbons in Hydrology. Atmospheric environmental tracers commonly used to date groundwater on time scales of years to decades include CFC-11, CFC-12, CFC-113, SF6, 85Kr, 3H, and 3H/3H(0), where 3H(0) refers to initial tritium (3H tritiogenic 3He) (Cook and Herczeg, 2000).
Interpretation of age from environmental tracer data may be relatively simple for a water sample with a single age, but the interpretation is more complex for a sample that is a mixture of waters of varying ages.
A mixture can be a natural result of convergence of flow lines to a discharge area such as a spring or stream, or it can be an artifact of sampling a long-screen well.
TRACERMODEL1 contains a worksheet that can be used to determine hypothetical concentrations of atmospheric environmental tracers in water samples with several different age distributions.