Radioactive contamination of surface water

Following the Chernobyl accident (to 2000-2004), the 137Cs content in most Ukrainian rivers (lower reservoirs on the Dnipro River, the Desna River and the Danube River) reduced to the pre-accident levels of 0.5-1.5 Bq m-3, demonstrating the effects of natural attenuation processes such as radionu­clide vertical migration into soil and its irreversible fixation by soil particles. Relatively high levels of radionuclide activity are still observed in the Pripyat River and in other waterways within the ChEZ (50-300 Bq m-3 for 90Sr, 20-80 Bq m-3 for 137Cs). At the same time, ’0Sr content in the Pripyat River is about 1.0-1.5 orders of magnitude lower than allowable levels of radionuclides in drinking water (2000 Bq m-3) established in Ukraine.

During 2008-2009, the radionuclide concentrations in the water of the Kyiv Reservoir for 90Sr ranged from 40 to 100 Bq m-3 and for 137Cs from 10 to 20 Bq m-3’ while in the Kakhovka Reservoir (lowest in the cascade of

Dnieper reservoirs), the 137Cs activities varied from 0.5 to 1.0 Bq m-3. Radio­nuclide washout in the rivers is constantly decreasing. On a background of reduction of radionuclides by surface runoff, the annual infiltration outlet of contaminated water from the Chernobyl cooling pond remains more or less stable, making its relative contribution to the Pripyat River contamina­tion higher compared to surface runoff.

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