Radionuclide Contents in Suspended Sediments in Relation to Flood Types in the Lower Rhone River

The aim of this work was to study the influence of watershed heterogeneity on the radionuclide contents of suspended particulate matter (SPM) in a large Mediterranean river. As the Rhone River catchment is characterized by a high climatic and geological heterogeneity, floods can be distinguished according to their geographic origins. Long-term time series of particles associated with radionuclides acquired in the framework of radiological surveillance provide a relevant dataset to investigate the variability of radionuclide contents. The SPM exported during Mediterranean floods differ from other floods as they display higher 238U and 232Th contents and the lowest activity ratio 137Cs/(239+240)Pu; these properties could be related to bedrock type and erosion process characteristics and/or to source term differentiation.