Comparison of Chernobyl power accident after-effects in the Baltic and Black seas

The measurement results of the radionuclide 137Cs volume activity (v.a.) in the waters of the Baltic and Black Seas are compared. In 1986 the radioactive pollution of these seas had a heterogeneous structure, and radionuclide 137Cs v.a. average values were equal to 148 and 152 Bq/m3 in the Baltic and the Black Seas accordingly. However, the average value of this radionuclide v.a. did not change in the surface water of the Baltic Sea in 1987-1989. At the same time radionuclide 137Cs v.a. in the Black Sea decreased, and in 1991-1992 its average values became almost the same, as before the Chernobyl Power Plant accident. A slow self-purifying process of the Baltic Sea waters is probably connected with hydrophysical peculiarities or with the action of radionuclide 137Cs additional sources action. (author)