LONG-CORE PROFILES OF CS-137, CS-134, CO-60 AND PB-210 IN SEDIMENT NEAR THE RHONE RIVER (NORTHWESTERN MEDITERRANEAN SEA)

Various anthropogenic radionuclides and Pb-210 were analyzed in a 4.3- m-long core, sampled near the Rhone River mouth in March 1991, to eval uate the extent of industrial releases that accumulate in this area. T he whole core was significantly marked by radionuclide inputs from the nuclear facilities located along the river (Cs-137, Cs-134, Co-60). I rregular profiles in natural and artificial radionuclides should be re lated to variations in their respective inputs from the Rhone River to the Mediterranean Sea. Minimum concentrations were found during high flow periods. Using both the Cs-137/Cs-134 profile in the core and the range of this ratio in Rhone waters, mean apparent accumulation rates were estimated to range between 37 cm yr(-1) and 48 cm yr(-1). This c ore would then represent a sedimentary record over a 7-10 year period. However, the presence of a signal from the Chernobyl accident, which occurred on April 26, 1986, was not clearly observed in the core. Inve ntories of both artificial and natural radionuclides were greater than expected from atmospheric inputs. The increased sedimentation occurri ng in close vicinity to the mouth of the Rhone River is thus responsib le for trapping of elements transported by the river to the Mediterran ean Sea. In this area, inventories of artificial radionuclides are wel l in excess of aerial deposition from Chernobyl and atmospheric weapon s tests and are linked primarily to industrial releases.