[Model for calculation of fish contamination by 137Cs and its application for Lake Kozhanovskoe (Bryansk Region)].

A dynamic model was developed for evaluation of the fish contamination by 137Cs. The dynamics of the accumulation of the radionuclide and the elimination is calculated taking into account the ecological and physiological characteristics of the fish, such as growth and metabolic rates, its position in the food chains of the aquatic ecosystem. The biological elimination of 137Cs from the freshwater fish is proportional to the metabolic rate of the fish. The dimensionless coefficient of the proportionality is equal to epsilonA = 0.3 +/- 0.1. The model was applied for the reconstruction of the long-term dynamics of 137Cs in the food chain "goldfish-pike" from Lake Kozhanovskoe (Bryansk Region, Russia). In 1990-1999 the specific activity of 137Cs in goldfish (generation of 1990) varied in range about 5-20 kBq/kg, whereas the specific activity of 137Cs in pike (generation of 1989) varied in range about 20-40 kBq/kg. The comparison with the data of the observations confirmed that the presented method allows to evaluate adequately the levels and the dynamics of 137Cs accumulation by the freshwater fish.