Spéciation de radionucléides dans les suspensoides du Fleuve St. Laurent

Abstract

About forty radionuclides, some naturally occurring, others artificially produced, have been detected in the St. Lawrence River at the heights of Québec City. Speciation studies of the radionuclides present in the suspended matter transported by the river were carried out from samples collected with a swimming pool type sand filter. Speciation was done with the reagents commonly used for similar studies for trace metals in sediments. Four fractions have been characterized; one associated with the carbonates, another with the iron and manganese oxides, the organics and the residue. The distribution of the radionuclides on these different fractions gives useful information on the type of interaction between the radioactive species and the solid phase. For instance, 7Be, 106Ru, 144Ce and 210Pb are weakly retained on the solid phase whereas naturally occurring radionuclides like 228Th, 238U, 226Ra, 40K and 137Cs are strongly retained on it. Airborne 210Pb following the decay of 222Ra in the air is the most likely source for this nuclide since most of it is not supported by 226Ra. In many respects, 210Pb seems to behave like the airborne 7Be.