AVAILABILITY OF MOLLUSKS AS 'BIOLOGICAL MONITOR' TO MONITORING OF THE LONG -LIVED SILVER ISOTOPE RELEASED INTO THE MARINE ENVIRONMENT

摘要

The species of mollusks often show unique physiological properties and the elemental composition different from those of fishes as observed in the blood constituents. Much higher concentrations of metal elements such as cupper, zinc, cadmium and so on have been reported for squids and bivalves than other organisms. The present study reports the results of gamma spectrometry analyses for two species of gastropods (Buccinum isaotakii and Buccinum striatissimum), one of the important species of mollusks, inhabiting on the sea bottom at the depth of some hundreds meters off the coast and for squids (Todarodes pacificus,Thysanoteuthis rhombus, etc.) landed at several fishing ports in Japan. It would be noted that ~(108m)Ag (half-life time: 418.21 y) was commonly detected in the viscera of both gastropods and squids usually at the radioactivity level higher than ~(137)Cs. A discussion on the distribution and inventory of ~(108m)Ag in the water column was attempted on the basis of the data on its specific activity, which was derived from the data on stable silver for the samples of interest obtained by analyses using ICP-AES. Special attention was directed to the efficacy and applicability of the mollusks having an affinity for this element to the environmental monitoring as indices.