Cs and 90Sr in water and suspended particulate matter of the Dnieper River-Reservoirs System (Ukraine)

Fallout from the Chernobyl accident caused extensive contamination in the drainage basin of the Dnieper cascade (Ukraine). From 1986, a radiological monitoring system has been established along the Dnieper system of reservoirs. Samples of water were regularly collected in the rivers feeding the Kiev reservoir and in the inflows and outflows of the six large artificial reservoirs (Kiev, Kanev, Kremenchug, Dniprodzerdzin, Zaporozhie, Kakhovka) composing the Dnieper cascade system. Measurements of radiocaesium and radiostrontium made from 1987 to 1993 showed that the radioactive contamination of the rivers is considerably influenced by the hydrological conditions. As expected, the data revealed a close relationship between 90Sr concentration in water and river flow levels. 137Cs appears to be less dependent on surface hydrology. The reservoirs were found to act as sinks for radiocaesium with extensive accumulation recorded in the first reservoir. About 43% of the dissolved form of 90Sr that entered the Dnieper system from 1987 to 1993, reached the Black Sea.