Radionuclide sources in the Barents and Kara Seas

A study of radionuclide distributions in the Barents Sea sediments was carried out in 1992. The conclusions of the study are as follows: 1) Elevated levels of artificial radionuclides as great as 15,000 Bq/kg for 239,240Pu, 250 Bq/kg for 137Cs and 100 Bq/kg for 60Co were measured in sediments in Chermaya Bay which have been contaminated by several nuclear tests conducted in the 1950s. 2) Sediment-depth distributions of 239,240Pu and other artificial radionuclides are consistent with results from biodiffusion models that are constrained by 210Pb sediment-depth distributions. These results indicate that sedimentation rates in Chernaya Bay are low (<0.05 cm/y) and that downward transport of radioactive contaminants is governed mainly by sediments mixing or bioturbation with the entire inventory retained in the upper 20 cm of the sediments. 3) Chernaya Bay plutonium is distinguished by low initial 249Pu/239Pu and 241Pu/239Pu atom ratios of 0.030 and 0.0012, respectively and a 241Am/239,240Pu activity ratio of 0.05 (compared to 0.3 in fallout) which provides a method for tracking its dispersion over distances of 100 km into the Barents Sea. 4) Artificial radionuclide levels in sediments and seawater near a sunken barge loaded with radioactive wastes in the Novaya Zemlya trough are similar to background fallout levels in the Kara Sea and provide little evidence for the release of radioactive contaminants from the dumpsite. 7 refs., 4 figs