Anthropogenic ²³⁶U and Pu at remote sites of the South Pacific

Abstract

Anthropogenic radionuclides, like ²³⁶U and ²³⁹,²⁴⁰Pu, are present in the environment as a result of global fallout from nuclear weapons tests conducted in the 1950s and 1960s and can potentially be used as tracers in soil erosion and sediment movement studies. Here, we report data on ²³⁶U and ²³⁹,²⁴⁰Pu in soil samples from the Motueka Valley (New Zealand) and for the first time from two remote islands Rarotonga and Atiu (Cook Islands) in the South Pacific. ²³⁶U and ²³⁹,²⁴⁰Pu were measured using Accelerator Mass Spectrometry (AMS) at the Australian National University. The ²³⁶U and ²³⁹Pu isotope concentrations versus soil depth and the ²⁴⁰Pu/²³⁹Pu and ²³⁶U/²³⁹Pu isotope ratios are discussed for each site. The radionuclide depth dependence revealed any soil disturbance, whereas the isotopic signatures indicated the source of the radionuclides’ origin.