Evaluation of the biological transfer of 32P, 137Cs and 65Zn by fish in the Yenisei River.

The biological transfer of three radionuclides ((32)P, (137)Cs, (65)Zn) by fish in the Yenisei River (Central Siberia, Russia) was evaluated using a radioecological model. The modelling is based on the general ECOMOD methodology, where radionuclide behavior in an aquatic organism is linked with the processes of growth and metabolism, also with the concentrations of stable analogous elements in the organism, its food and the environment. The model was applied to explain the peculiarities of (32)P, (137)Cs and (65)Zn accumulation in different ecological groups of fish, including non-migratory and migratory fish, non-predatory and predatory fish species. The highest activity concentrations in non-migratory fish from the Yenisei River were found for (32)P. The accumulation of (32)P by fish was shown to depend on the fish size (age, weight); however, it did not depend on the trophic status of fish. The modelling approach was developed to evaluate the biological transfer of radionuclides by the migratory fish, which spend the most part of life in the Yenisei delta, inlet or bay, and go upstream the Yenisei River for spawning. The results of the ECOMOD model calculations are in good agreement with available measurement data.