Tritium age dating groundwater
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.
Precisely measuring the concentration of CFC's dissolved in groundwater samples.These tests which were mainly performed in the early 1960s, led to an increase of tritium in precipitation over the continents of the northern hemisphere from roughly 5 TU to levels of the order of 1000 TU.One TU (Tritium Unit) means a tritium to hydrogen ratio of 10.After oxidation to HTO, it takes part in the natural water cycle.Before the full potential of natural tritium as a tracer for water movement in natural systems could be explored its distribution was masked by addition of large amounts of so-called ‘bomb tritium’ produced during the surface tests of nuclear weapons.With precise measurement, the parent and daughter isotopes can be quantified, providing a means to accurately date when water was recharged.
If you would like to know more about tritium/helium-3 dating, see the Tritium page, and for more information about helium and other noble gases, see the Dissolved & Noble Gas page.
The date of recharge can be determined using the atmospheric CFC records.
For more information about the use of chlorofluorocarbons for dating, see the Chlorofluorocarbons page.
GNS provides a number of complementary age tracer methods to date water samples.
These include tritium, CFCs, SF6, silicon-32, carbon-14, and stable isotopes, covering a range of ages from less than six months to tens of thousands of years.
During precipitation events this tritiated water enters groundwater and can be used as a dating tool for recharge.