The Tritium-3He Groundwater Dating Method

The preceding sections dealt with a variety of hydrological applications of the manmade tritium signal. However, the tritium dating method has a number of shortcomings  

During the last decade a different track has been followed for the tritium dating method, namely, measurement of the decay product 3He (section 10.1) as a substitute for the initial tritium concentration. Tritium-derived 3He (tritiogenic helium) is built up in the groundwater as the contained tritium disintegrates hence, the 3H 3He ratio decreases with age. To facilitate the calculations both nuclides are expressed in TR (tritium ratio) units, that is, 3H H and 3He H ratios of 10-18. In principle, the age of groundwater can be determined by measuring the tritium concentration left 

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A major task in the tritium-3He dating method is the identification of 3He based on the background of the atmospheric helium, which has a 3He 4He ratio that varies from one place to another within a wide range of values. 

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