208Tl and 24Na Gamma Sources for Identifying Soil Water Tagged with Deuterium
1971
Hawkins, R. H. | Overman, R. F. | Corey, J. C.
In situ tracing of soil water movement with the D₂O-²⁴Na method has been limited by the need to reactivate the ²⁴Na gamma source frequently (half-life of 15 hours) in a nuclear reactor. Our laboratory study showed ²⁰⁸Tl produced the same neutron count rates from vials of D₂O in dry and moist soil as did ²⁴Na. The 1.9-year effective half-life of ²⁰⁸Tl in equilibrium with its parent nuclide ²²⁸Th is a significant advantage of ²⁰⁸Tl over ²⁴Na. Recent commercial availability of ²⁰⁸Tl sources now makes in situ D₂O tracing of soil water feasible for investigators not having access to a nuclear reactor.
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