抄録
Top shells were exposed to concentration gradients of cadmium, 0 (the control, 0.052μg/l of cadmium contained originally), 5, 10, 15, 20μg/l for 80 days. The specimens exposed were re-moved from aquaria five times to determine the metal taken up in viscera and muscular tissues.
In each experimental group except the 0μg-group, cadmium was taken up additionally in the viscera and the muscular tissues of the other groups. As days elapsed, the cadmium concentra-tions of two compartments and whole soft bodies increased clearly with the different rates de-pending on the concentration gradients of cadmium in rearing seawaters. Accumulation curves. were represented as follows: logY=logA+BlogX for whole soft bodies and the viscera, and Y=a+bX for the muscular tissues, in which Y's are cadmium concentrations in tissues, and X's are exposure times in days.
Distribution rates of cadmium in the viscera (99 to 45%) differed remarkably from those in the muscular tissues (1 to 5%)irrespective of the concentration gradients. The former decreased somewhat towards the end of the exposure period but on the contrary the latter increased slightly.
It was estimated that 1074 days for whole soft bodies and 625 days for viscera were necessary to attain to the availability rate of 10%'s from the regressive relations between the rates (Y) and exposure times in days (X), respectively.
The criteria of cadmium for human health (10μg/l) and for marine environment (5μg/l) are not adequate to top shells from the viewpoint of accumulation quantities of the metal by soft bodies during the long-term exposure, and also possibly to other sessile forms.
