ИСТИНА

A Chernobyl-derived Cs-137 fallout became a reason of formation of non-uniform field of radionuclide contamination along vast territory of the Europe. It was assessed after detailed field investigation within few river basins located in areas with different level of Chernobyl contamination, that existing radioecological maps composed during last two decades are not enough detailed for evaluation of large-scale assessment of initial contamination field transformation by the lateral migration processes of the Chernobyl-derived Cs-137 . The only way for researcher to overcome of this problem is additional soil sampling for evaluation of Chernobyl-derived Cs-137 concentration in different locations within study catchment for following creation of detailed radioecological maps based on collected data. It is necessary to evaluate the optimal number of samples which should be taken in each sampling point for receiving statistically correct results of radionuclide concentration. Special investigation was undertaken in few catchments (S= 2-50 km2) of the Central Russia, located in areas with different levels of initial Chernobyl contamination, for evaluation the optimal number of samples, which should be taken in each sampling point for the determination of Cs-137 concentrations error not exceed 30 % on 95 % significance level. Results of investigation will be presented.