水銀を含む底質を懸濁させた海水中における魚体への水銀の蓄績
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概要
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Three species of fishes, red sea bream (Chrysophrys major), mejina (Girella punctata), and marbled rock fish (Sebasticus marmoratus) were reared in three kinds of sea water suspending the muds of Minamata Bay, whose total mercury concertra-tion levels were about 600 and 100 ppm-dry base-, and a reference mud (total mercury concentration: 0.1 ppm-dry base).The mercury in the muds was mainly in the form of insoluble compounds. The relationship between the rearing time in these sea waters and the increase in total and methyl mercury concentrations (T-Hg and M-Hg) of these fishes was traced. Very small increases of T-Hg and M-Hg were observed during the experiments, although the equilibrium values (y∞) were rather low (maximum value for T-Hg:0.278 ppm-in mejina-, for M-Hg: 0.144 ppm-in marbled rock fish). There was little difference in the rate or the extent of mercury accumulation from mud suspen-sions in which T-Hg (neary insoluble) varied from 600 to 0.1 ppm. When, in a reference experiment, the fishes were reared in aerated sea water irradiated by U.V. light, the y∞ values were 0.315 ppm (T-Hg) and 0.171 ppm (M-Hg), which were slightly larger than those values obtained without aeration and U.V. irradiation. From the results described above, it was concluded that there is little possibility of mercury accumulation into fish from mud suspensions containing the mercury in the form of insoluble compounds to such an extent as to exceed the maximum permissible levels established by the Ministry of Health and Welfare, Japanese Government.
- 日本水産學會の論文