Tritium activity in Australian rainwater 1962-1986

Abstract

Atmospheric tritirecipitated in rainfall has been measured since 1962 in samples from a network of Australian monitoring stations. Atmospheric thermonuclear bomb tests have injected into the atmosphere about 350 kg of tritium mostly into the northern hemisphere's troposphere and stratosphere causing atmospheric concentrations of tritium to reach peak values of 50 to 100 tritium units (TU) in the southern hemisphere. Tritium from underground testing has not contributed significantly to the amounts in the atmosphere or in surface waters. In Australia peak concentrations of precipitated tritium were observed in 1962, 1964 and 1969. The tritium activity in rainwater for all Australian stations decreased after 1969. Radioactive decay of bomb tritium will decrease the tritium budget to the natural level by the early 1990s in Australian precipitation.