Comparative migration behaviour of 90Sr, 239+240Pu and 241Am in mineral and organic soils of France

The vertical migration of 90Sr, 239+240Pu and 241Am has been studied in two types of soils in France (acid forest soil in the Vosges Mountains and organic-rich alkaline wetland in the Mercantour area). In order to interpret the different migration behaviour of radionuclides, the combination of two approaches are proposed – a statistical study of the evolution of radionuclide ratios (241Am/239+240Pu, 90Sr/239+240Pu) with depth and a calculation of the radionuclide migration rates. Migration behaviour of 90Sr, 239+240Pu and 241Am is significantly different in the Vosges and Mercantour soils. In the Mercantour soil 241Am was found to be less mobile than 239+240Pu. In both profiles 90Sr is more mobile than 239+240Pu. The high sand content (55–60%) and weathering processes of cations in the Vosges soil are thought to be responsible for the larger migration rates of radionuclides in depth, while the high organic matter content (>70%) of Mercantour soil is thought to be responsible for the stronger retention of 241Am in the first 10 cm of the soil.