Polonium-210 content of marine shrimp: Variation with biological and environmental factors

The concentrations of 210Po and 210Pb were determined in more than 30 species of marine shrimp. Samples were collected in the years 1977 to 1980; most were from the Mediterrancean Sea near Monaco, the remainder from Kuwait, South Africa, USA and Great Britain. The median 210Po concentration was 8.0 pCi g-1 dry wt in the whole shrimp and 85 pCi g-1 dry in the hepatopancreas; the corresponding 210Po:210Pb activity ratios were 77 and 138, respectively. The range of concentrations covered more than two orders of magnitude for both nuclides. The variations in the levels of 210Po, in particular, could be related to biological and environmental factors; thus, penaeid shrimp had 210Po at median concentrations some three to four times higher than carid shrimp, and there was a steady increase in the median 210Po concentration as one moved from estuarine to coastal to pelagic to deep-pelagic species. 210Po levels were highest in 3 species of deep-pelagic penaeids, where a median 210Po concentration in the whole shrimp of 43 pCi g-1 dry wt was found. The natural radiation dose received by the hepatopancreas of such individuals will be of the order of 100 rem per yr. Elevated 210Po was also found in 4 species collected near Kuwait. The 210Po data are interpreted as indicating changes in the food regime of different shrimp; specifically it is suggested that 210Po-rich items such as hepatopancreas, faecal pellets and organic particulates are likely to be important in the diet of shrimp which feed at depth in the ocean. It is suggested further that the ultimate availability of 210Po to the foodchain depends on its form in sea water, and the need for information concerning the degree of organic binding of 210Po in natural waters in stressed. © 1981 Springer-Verlag.