Accumulation of cesium-137 by useful mollusca

There are few data available on the radioactive contamination of marine mollusca, especially cephalopoda. Therefore, in this paper, data obtained on the radioactive contamination of cephalopoda were compared with those on pelecypoda and gastropoda. The uptake and elimination experiments were carried out by means of radioisotope tracer methods, and the concentration factors of 137Cs due to radioactive fallout were estimated. The contamination of cephalopoda was also compared with those of other marine organisms in terms of concentration factor. The activity ratios in the organs or tissues of octopus were in the range of 3.5 and 12.8 on the 14th day after the beginning of exposure and those of squid were in the range of 8.8 and 10.9 on the 6th day after the commencement of the experiment. The biological half time was 90 days for octopus from the observation over 75 days, while it was 31 days for clam from the results of 75 days' experiment. The concentration factors of 137Cs due to radioactive fallout were in the range of 3 and 23 for cephalopoda, 7 and 28 for pelecypoda and 24 and 30 for gastropoda, respectively. It was concluded that no difference in the concentration factors was clearly observable among the classes of mollusca, but the values were substantially similar to those of crustaceans and slightly lower than those of marine fish. (auth.)