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.