魚類における水銀の動向について (Hg Series No. 15)
第1報 河川の水銀汚染と魚類中水銀濃度
1974 年 28 巻 6 号 p. 574-581
詳細
1974 年 28 巻 6 号 p. 574-581
In the nation-wide survey of mercury levels in river fish conducted by the Ministry of Health and Welfare (later by the Environment Agency) since 1968, the authors have collaborated with the project by analysis of samples in several districts.
Unusually high levels of mercury around 1ppm were found in fish from the Jinzu River and Oyabe R. (Toyama), Muka R. and Shokotsu R. (Hokkaido), Hono R. (Nara), in addition to the notorious Minamata Bay and Agano R. where human poisoning has been reported.
1. In the Jinzu R., the extraordinary feature was the detection of ethylmercury in fish far above the level of methylmercury. Investigation of the source of pollution finally implicated a pharmaceutical factory synthesizing an antiseptic “Thimerosal” (Sodium ethylmercury thiosalicylate) which was discharging ethyl- and inorganic mercury into the river.
2. In the Muka R. (and also Hono R. and Shokotsu R.) which starts from and runs through mercury mine areas, the major component of mercury in fish was methylmercury, supporting the hypothesis of natural conversion of mercury, reported by Swedish researchers.
3. The variation of mercury levels in fish was large in the areas of industrial pollution by organic mercury (in the Jinzu R.), but small where natural contamination was caused by geological factors (in the Muka R.)
4. The correlation between mercury levels and fish size (fish age) was positive in case of natural contamination over a wide area, but insignificant in areas of localized industrial pollution.
