Origins and levels of artificial radionuclides within the Rhone river waters (France) for the last forty years. An analysis of the radioecological sensitivity of river systems

The Rhone watershed extends over one hundred thousands square kilometers, i.e. one fifth of the metropolitan French territory. The Rhone is the major River entering the Western Mediterranean Sea as it generates the main source of sediments and freshwater (50%) to the sea, with an average water discharge of 1700 m3 s-1. The River input affects primary production significantly in the north-western Mediterranean area and plays a leading role on the marine ecosystem functioning in the whole Gulf of Lion. Twenty nuclear reactors are situated along the Rhone valley, representing Europe's biggest concentration of nuclear power plants. Down flow all these installations the spent fuel reprocessing plant of Marcoule released over many years most of the liquid radioactive wastes including plutonium isotopes in the Rhone River. Artificial radionuclides also originate from the weathering of the catchment basin labeled by both the global and the Chernobyl accident atmospheric fallout. These radioactive inputs have led to a permanent contamination of the Rhone River waters. Long-term chronological series of artificial radionuclide activities within the waters at the lower reaches of the Rhone River were acquired from 1979 to 2002. These data give evidence for various radioecological responses of the aquatic system over years. Based on these observations several major radioecological sensitivity factors for river waters are identified. (author)