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

Abstract

In this paper we present seven unsaturated zone profiles of 36 Cl and three 3 H 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 36 Cl have been found below a 2‐m depth. In this profile, 3 H and 36 Cl peaks coincide. In six of the seven profiles, total 36 Cl fallout was found to be between 1.2 and 2.4 × 10 12 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 3 H, 36 Cl, and chloride are briefly discussed.