Distribution of selected anthropogenic radionuclides (137Cs, 238Pu, 239,240Pu and 241Am) in marine sediments with emphasis on the Spitsbergen–Bear Island area

Measurements of anthropogenic radionuclides in marine sediments can provide good estimates of past and present radioactive contamination of the marine environment. The Barents Sea is one of the worldʹs richest ocean areas, and it is therefore of major interest for Norwegian fisheries to document the levels of radioactive contamination of this and adjacent ocean areas. In this study, concentrations of 137Cs, 238Pu, 239,240Pu and 241Am were measured in marine sediments collected mainly in the Spitsbergen–Bear Island region. Additional samples collected in the deep Norwegian Sea and near the Greenland ice-edge have been included for comparison. The highest radionuclide levels were found near Spitsbergen, reaching over 50% higher than in adjacent areas. Determinations of the mineral content and particle size distribution indicate a relation between the content of clay minerals and radionuclide levels. The present study confirms earlier observations of elevated levels of 137Cs in sediments in the Spitsbergen–Bear Island area and documents elevated levels of 238Pu, 239,240Pu and 241Am in these sediments. Using an exponential curve fit based on determinations of unsupported 210Pb in sediment cores, sedimentation rates of 0.28, 0.05 and 0.26 cm year−1 were calculated at locations south of Spitsbergen, near the Greenland ice-edge and in the deep Norwegian Sea, respectively.