Radioactive contamination of the north-western Black Sea sediments

The paper deals with the input and deposition of the man-made radionuclides Cs-137, Pu-238, Pu239+240 and Am-241. introduced to the north-western Black Sea, over the last few decades, as the result of atmospheric nuclear weapons testing and the Chernobyl nuclear accident. One approach taken was to retrieve the deposition records of these radionuclides in the sediments. The deposition chronology was compared with monitoring data of the post-Chernobyl input of Cs-137 to the NW Black Sea sediments from the Danube River. The partitioning of Cs-137 between suspended matter and water was traced along the salinity gradient in the Danube mixing zone. In sediments deposited in the vicinity of the Danube delta and the Dniepr estuary, the activity of Chernobyl Cs-137 had reached its maximum 5 and 10 years after the accident, respectively. The activity ratio of Cs-137 to Pu239+240 and Am-241 revealed a higher mobility of Cs-137 in the Danube River basin compared to plutonium and americium. The percentage of particulate Cs-137 and its distribution coefficient vs salinity have allowed the estimation of sedimentary scavenging and desorption of caesium in the Danube mixing zone. Comparison of the post-Chernobyl Cs-137 input from the Danube to the Cs-137 inventory in the adjacent Black Sea sediments showed that more than 70% of this radionuclide was deposited in the Danube-Black Sea mixing zone. (C) 2002 Elsevier Science Ltd. All rights reserved.