Unsaturated zone tritium and chlorine 36 profiles from southern Australia: Their use as tracers of soil water movement

In this paper we present seven unsaturated zone profiles of ³⁶Cl and three ³H profiles from southern Australia. All profiles show single peaks corresponding to high radionuclide fallout from nuclear testing in the 1950s and 1960s. The profiles are used to estimate rates of water movement leading to recharge of the groundwater. Among these profiles is the first profile on which high concentrations of ³⁶Cl have been found below a 2‐m depth. In this profile, ³H and ³⁶Cl peaks coincide. In six of the seven profiles, total ³⁶Cl fallout was found to be between 1.2 and 2.4 × 10¹² atoms m⁻², and is of similar magnitude to that found at similar latitudes in the northern hemisphere. Comparisons of soil water fluxes estimated with ³H, ³⁶Cl, and chloride are briefly discussed.