Plutonium isotopes as a good tracer for environmental studies

    It is well-known that ¹³⁷Cs has been widely applied as a powerful tracer for soil erosion and sediment dating studies since the 1960s. However, due to its relatively short half-life (30.2 year), the concentrations of global fallout ¹³⁷Cs in the environment have decreased by a factor of more than 2 comparing to the levels in the 1960s due to its radioactive decay, and this declined trend will continue. This makes the applications of ¹³⁷Cs for investigations of soil erosion, transportation and sedimentation less sensitive at present and will become difficult in the future. ²³⁹Pu and ²⁴⁰Pu, because of the long half-lives (T_1/2=24100 year for ²³⁹Pu and T_1/2=6561 year for ²⁴⁰Pu), their dominating source of nuclear weapons testing fallout worldwide, as well as their high retention and low mobility in soil, they were suggested as an ideal substitute of ¹³⁷Cs for environmental tracing studies. In recent years, with the rapid development of sensitive measurement techniques using mass spectrometry especially the inductively coupled plasma mass spectrometry (ICP-MS), the application of Pu isotopes in environmental studies becomes more attractive and competitive. Here we presented some preliminary studies regarding Pu isotopes as tracers for soil erosion studies and lake sediment dating in China. Our results indicated that Pu isotopes are powerful and promising tracers in future environmental studies.