Polonium-210 and lead-210 in marine food chains
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210Po and 210Pb have been measured systematically in whole animals, muscle and hepatopancreas of crustaceans and of molluscan cephalopods representative of a pelagic and benthic food chain. The same nuclides were also measured in liver, pyloric caecum, stomach contents and muscle of tuna. The concentration factors from sea water to whole animals were approximately constant along both food chains, being of the order of 104 for 210Po and 102 for 210Pb. The highest concentration factors were found in shrimp of the genus Sergestes. In muscle, the concentration factors were an order of magnitude less; in the hepatopancreas, they were an order of magnitude higher, reaching 106 in shrimp of the genus Sergestes. Such concentrations imply alpha-radiation doses of the order of 10 rem per year and more in this organ, which contains about 50 to 90% of the 210Po in the whole animal in the 11 species analyzed. A detailed study of the intracellular behaviour of 210Po in the hepatopancreas is clearly indicated. 210Po can be used as a sensitive natural tracer in biological systems. Thus, feeding Meganyctiphanes norvegica in the laboratory on food low in 210Po led to an approximate value of about 61/2 days for the biological half-life of 210Po in the hepatopancreas of this euphausiid. Furthermore, the data on 210Po and 210Pb in the cephalopod hepatopancreas allowed the time of conservation of frozen squid which had been bought at the market to be estimated.
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