CS-137 AND SR-90 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 radi ological monitoring system has been established along the Dnieper syst em of reservoirs. Samples of water were regularly collected in the riv ers feeding the Kiev reservoir and in the inflows and outflows of the six large artificial reservoirs (Kiev, Kanev, Kremenchug, Dniprodzerdz in, Zaporozhie, Kakhovka) composing the Dnieper cascade system. Measur ements of radiocaesium and radiostrontium made from 1987 to 1993 showe d that the radioactive contamination of the rivers is considerably inf luenced by the hydrological conditions. As expected, the data revealed a close relationship between Sr-90 concentration in water and river f low levels. Cs-137 appears to be less dependent on surface hydrology. The reservoirs were found to act as sinks for radiocaesium with extens ive accumulation recorded in the first reservoir. About 43% of the dis solved form of Sr-90 that entered the Dnieper system from 1987 to 1993 , reached the Black Sea.