Cesium-137 in a Dysoligotrophic Lake. A Radioecological Field Study

摘要

The concentration of exp 137 Cs in water, sediment, and different species of fish have been studied in the dysoligotrophic Lake Ulkesjoen. A mathematical model is presented, which describes the turnover of exp 137 Cs in the lake. The model has been applied to calculate the fraction of the exp 137 Cs-activity introduced into the lake and which will be stored in the sediment. This fraction was calculated to be 0.38. The model also shows that 1.9 percent of freshly deposited exp 137 Cs and 0.7 percent per year of the cumulative deposition of exp 137 Cs will be removed from the drainage-area and introduced into the lake, indicating that the radionuclides is strongly bound to soil and vegetation in the drainage-area. The concentration of exp 137 Cs in muscle-tissue of pike has been studied during 1961 to 1974 and of perch, roach, and rudd during 1963 to 1974. The maximum values were observed in 1964 or 1965 depending on the species. Since then the concentration of the radionuclide has decreased and was in 1974 about one fifth of the maximum values. The apparent half-time of the decrease has been determined to about 2.5 years during 1965 to 1969 and about 6 years during 1969 to 1974 for all species of fish. Based on published data concerning the food of pike and experimental data on the concentrations of exp 137 Cs and potassium in the food, a mathematical model has been used to calculated the biological half-times of exp 137 Cs in pike. Assuming an assimilation of 1.00 the biological half-time has been calculated to 1.3 years for exp 137 Cs. The results are valid for a pike of weight 0.5 kg and at a water temperature of 8 to 10 exp 0 C. (Atomindex citation 08:343195)