Tritium 3he dating of shallow groundwater
Kaufman and Libby, 1954; Begemann and Libby, 1957; Giletti et al., 1958).Starting in the early 1950's tritium from anthropogenic sources (mainly nuclear weapon tests) was added to the atmosphere in considerable amounts.Most samples have the dissolved He concentration that is comparable to the equilibrium with the atmospheric He 4.5-6.6×10-8 (cc STP/g).The highest He concentration was observed to be 4.56×10-7 (cc STP/g) at Minato-Shinmachi.Generally, the contribution of the mantle He is greater than the radiogenic, because the mantle He has 1.05-1.25×10-5 for the ratio of 3He/4He and 1-10×10-9 is for the radiogenic 3He/4He ratio. The recharged zone is located at a high mountain area with an altitude of more than 1800 m, formed by the Median Tectonic Line as an active fault, rising at the back of Saijo Basin as like a wall. We estimated groundwater residence time by 3H 3He, which were the conventional methods and the proposed method that takes into consideration of accumulation effect from the mantle 3He.
The 3H 3He dating method is the most practical method to estimate the residence time of shallow groundwater, which is one of most indispensable water resources for human in the future.
Only sample was less than detection limit (0.3 TU) for tritium concentration. Therefore, most groundwater samples are expected to have a short residence time.
However, the correlation between the ratio of 3He/4He and 4He(At)/4He(smaple) suggests two different groups are in the Saijo Basin, which they are identified with crustal He with different ratio of 3He/4He (i.e. This result strongly suggests the mantle He emanation in depth of the Saijo Basin.
I believe that water will play an increasingly important role in our attempts to achieve a sustainable global development." 19, 237-247. R., Wolff-Boenisch, D., Stefansson, A., Oelkers, E. International Journal of Greenhouse Gas Control, , 4, 3, 537-545.
H., Gunnlaugsson, E., Holmfridur S., Sigfusson, B., Broecker, W.