抄録
The synthetic investigations of mercury contamination in the Agano River were carried out for two years from 1976 to 1977 spending over 40 million yen. Since, higher concentration of mercury than the temporary standard of elimination was detected in a bottom sediment near the place of the discharge of “Kanose Denko Corp.” factory on the periodical investigations of mercury in August, 1975.
From investigations, in general, distribution of mercury concentration in bottom sediment of Agano River seemed to be the level of other noncontaminated rivers. High concentrations of mercury were found out from soil and the industrial waste deposit near the factory, but there was no worry for influences of mercury on the river, because the mercury in soil was confined in soil, solubility seemed very small, and there was little amount of methyl-mercury.
The concentrations of mercury in the industrial waste water and the water of the Agano River were not beyond the effluent standard or the environmental quality standard. But locally, from the place of the discharge to 150m downstream on right hand shore, there were some effects of mercury contents on some biological groups by the discharge of the factory. However, after the settling tank newly established, the effects of mercury in the dischage on the organisms were becoming small and the water environment concentration of mercury was near the value of natural fluctuations.
In general, influences of artificial contamination of mercury seemed to be almost cancelled in the Agano River.
