RADIOACTIVE CONTAMINATION OF THE YENISEI RIVER

Based on observational data in the period 1971-1993, radioactive conta mination of the Yenisei River ecosystem was analysed within 2000 km of the sire of discharges from the Krasnoyarsk Mining and Chemical Indus trial Complex. Data on the content of Na-24, P-32, (SC)-S-46, Cr-51, M n-54, Mn-56, Co-58, Ca-60, Fe-59, Zn-65, Sr-90, Zr-95, Nb-95, (103)RU, (106)RU, (CS)-C-134, (CS)-C-137, Ba-140, Ce-141, Ce-144 and Np-239 in the river ecosystem components were generalised. Radioactive contamin ation of water in the near zone of discharges (within 15km) was shown to be determined mainly by the short-lived nuclides, such as Na-24, (3 2)p, Mn-56 and Np-239, well as Cr-51. Outside the near zone the water contamination level decreased appreciably. According to observational data of 1973, the total contamination inventory of the river bottom in the near zone was as great as 5800 kBq m(-2). More than half was acco unted for by two radionuclides: Cr-51 and Zn-65. At a distance of1930 km from the site of discharges a tecknogenic activity of bottom sedime nts amounted to 5 kBq m(-2) and was accounted for by Cs-137 and Zn-65. Th, main radionuclide accumulated in fish was (32)p. Exposure doses t o aquatic organisms and population were assessed in the near and far z ones of the Krasnoyarsk radioactive contamination trace. Within 250 km of the site of discharges the exposure dose to the population from a consumption of I kg of fish was shown to amount to an average of 10 mu Sv(.)