Studies on the sorption and release of radionuclides by river sediments.

Abstract

Factors affecting the sorption of various radionuclides by a river sediment sample in the fresh or saline water were examined, in addition, release of radionuclides in the sediments when it was exposed to the sea water was studied. Water and sediment samples were collected at several places along the Sagami River, and radionuclides employed in this experiments were 90Sr, 137Cs, 54Mn, 60Co, 51Cr and 59Fe. Cation exchange capacity of the river sediments less than 120 mesh fraction was 1 meq/100 g determined by CaCl2 method, and 2 meq/100 g by the tagged cesium method, and the capacity of acid treated river sediments by NaCl method was 1 meq/100 g, respectively. Uptakes of radionuclides by the sediments were much affected by various competing cations, and the rate of inhibition depends not only on the cationic species but also concentration of cations. The higher in the concentration of a competing cation, the more inhibitive to the uptake of radionuclides by river sediments. Release of radionuclides which had been sorbed by the river sediments in the filtered sea water was examined during 12 days storage. Both 60Co and 137Cs were released easily, and never were re-absorbed. The release of 90Sr, however, increased for the first 2 days, then gradually decreased, which might be due to the re-absorption of the nuclide by sediments in the sea water. The rate of release of 54Mn was rather low, in addition, the amount released in the sea water decreased gradually, which might be due to the precipitation in the form of MnO2.