Using fallout plutonium as a probe for erosion assessment

A study has been carried out to assess the potential of using fallout plutonium (Pu), which originated from atmospheric nuclear-weapons tests, as a tool to investigate recent erosional processes within the lower Cotter water-supply catchment in the Australian Capital Territory. This catchment, which was predominantly pine plantation, was severely affected by a major bush fire in 2003. Accelerator mass spectrometry has been used to measure Pu in soil samples collected from a number of sites across the catchment. The results indicate that less than 1 cm of surface soil had been lost since the early 1960s over much of the catchment. Areas of more erodible soil have, however, lost 2–4 cm of topsoil, and a loss of ∼6 cm of soil was identified at one particular site.