Radioactive contamination in the marine environment. Report No. 2 from the national surveillance programme

During 1995 and 1996 a large number of samples of different types, collected from various fishing grounds of interest for Norwegian commercial fishing, were measured. During these years 50 pooled fish samples from a total of 2525 fish have been measured for gamma emitting radionuclides. Of these eight samples have also been measured for plutoniumisotopes. Thirteen samples of shrimps have also been measured for various radionuclides. In addition 800 samples of fish have been measured for radiocaesium on routine monitoring equipment with higher detection limit. For all those samples the content of radiocaesium fell below the detection limit. The general levels of radioactive contamination in the ocean areas surrounding Norway are low. In fish and shrimps the concentration of 137Cs is in the order of 1 Bq/kg. This is in the same range as the lowest levels found in products from the terrestrial ecosystem and far below the intervention levels for radioactive contamination of foodstuff. For most of the samples of biota measured for plutonium, the level fell below the limit of detection, a maximum of 5.6 mBq/kg og alpha emitting plutonium isotopes was found. Measurements on a number of samples of seawater, sediments and seaweed further confirms the low levels of radioactive contamination in the North Sea, the Norwegian Sea and the Barents Sea. For biota the levels of concerned radionuclides were decreasing towards north. This is due to the main sources of artificial radionuclides being located south of Norway, in the Baltic (Chernobyl fallout) and in the Irish Sea (Sellafield releases). 18 refs., 4 figs., 5 tabs