TRANSFER OF CO-60, ZN-65, TC-95, CS-134 AND U-238 FROM WATER TO ORGANIC SEDIMENT

Technetium-99 is a fission product that has entered the environment fr om diagnostic medical practice, nuclear facilities and weapons testing . Information on the behaviour of Tc-99 in aquatic ecosystems is limit ed primarily to marine environments (Aarkog et al., 1987; Rioseco C., 1987). An understanding of the transport and deposition behaviour of T c-99 in freshwater is important because of its potential to bioaccumul ate (Desmet et al., 1991; Higgo, 1987). In the present investigation t he transfer rate of Tc-95m was determined in the laboratory using natu ral organic sediment-water columns at 15 degrees C. Transfer rates of Co-60, Zn-65, Cs-134 and U-238 were also determined for comparative pu rposes and to compare their rates in the sediment-water columns with t hose in Canadian Shield lakes. Loss of the radionuclides from water wa s in the order Tc-95m < U-238 < Cs-134 < Co-60 < Zn-65 with mean trans fer rates of -0.019 d(-1) for (TC)-T-95m, -0.029 d(-1) for U-238, -0.0 37 d(-1) for Cs-134, -0.064 d(-1) for Co-60, and -0.110 d(-1) for Zn-6 5 being measured. Transfer rates for Tc-95m, Co-60 and Cs-134 were in close agreement with those measured in Canadian Shield lakes, whereas those for Zn-65 and U-238 were higher.