Biogeochemical studies of long-lived radionuclides in marine environments

At Eniwetok and Bikini lagoons, sup(239,240)Pu is always greater than fallout levels, in water samples, and this indicates that there is remobilisation from sediments. The respective water levels are 21 fCi 1-1 and 42 fCi 1-1, and lagoon inventories 0.96 and 1.2 Ci. This is 0.08% of sediment inventories. Small amounts of 241Am also dissociate. The soluble Pu is mostly Pusup(III,IV) when associated with particles and Pusup(V,VI) when truly soluble. Concentrations of 90Sr, 137Cs, sup(239,240)Pu, 241Am, 207Bi and 210Pb, 210Bi, 210Po in fish showed variation with trophic level in some cases. Values increased between levels 2 and 5 for 90Sr, sup(239,240)Pu, 241Am, but not 137Cs. Concentration factors varied, and a single generic value for all fish species was not possible. Extrapolation of results from contaminated lagoons to lesser contaminated lagoons was not possible because in the former, radionuclides were fused with CaCO3 and dissolve to some extent in the gut of fish. The speciation is different in lesser contaminated lagoons. Over 80% of the whole-activity of 207Bi in goatfish is associated with the muscle tissue, whereas less than 1% is found in the muscle of surgeonfish and mullet. Evidence was obtained that the isotope is translocating. Similarly 210Bi formed in fish bone translocates to liver. In the North-east Atlantic dumpsite, studies found concentrations no different from global fallout levels for radionuclides possibly leached from waste disposal practices there. (author)