Plutonium in the Deep Layers of the Norwegian and Greenland Sea

This paper presents the analytical results of transuranium radionuclides from sea water samples taken on a research cruise of R.V. Gauss conducted in June/July 1995. Whereas surface samples were frequently taken in the Norwegian, Greenland and Barents Seas during the past decades, this is the first extensive set of large-volume sub-surface samples which were analysed for transuranium elements ( 238 Pu, 239,240 Pu, 241 Am). In comparison with recently published surface results, significantly increased concentrations of plutonium were found in the sub-surface layers of the Norwegian and Greenland Seas. The Pu concentrations show peaks at depths of 100-250 m and 1000-1500 m. The 238 Pu/ 239,240 Pu activity ratio found in both peaks shows a significant influence of the discharges from the Sellafield reprocessing plant. In contrast, Pu activity ratios of fallout origin, or even close to that, are found only in very few samples from the entire area, whether from surface or sub-surface. The geographical extent of the waters marked by Sellafield plutonium covers the area 60°-78° N and 020° W to 040° E in the Barents Sea. As the current releases from the Sellafield works do not correspond with the amount of plutonium found, other possible sources and transport pathways to the Nordic Seas are discussed.