5) Water purification in the Jinzu River water system

4,COUNTERMEASURES AT POLLUTION-GENERATING SOURCE

Much metabolic activity occurs between the river bed and river water. Judging from the relationship between the cadmium Judging from the relationship between the cadmium concentration found in river water and that found in the river bed of the Jinzu River water system, it was suggested that the cadmium concentration in the river bed and that at the foot of the From the relationship between the cadmium concentration found in river water and that found in the river bed of the Jinzu River water system, it was suggested that the cadmium concentration in the river bed in the Jinzu River water system and that at the foot of dams could be lowered to the point that concentration in river water would no longer be harmful, if proper countermeasures The fact is that cadmium concentration in the river bed at Jinzu River Dam No,1 was between 1.6 and 1.8 By 1975, the average concentration was 2.33 ppm, and eventually 1.39 ppm and 0.7 ppm by 1976 and 1992 respectively, showing the river to have been purified by the countermeasures. Futhermore, the cadmium concentration in the Gyugakubi water supply that brought agricultural water to the pollution-generating source has been purified by the countermeasures taken at the pollution-generating source. Futhermore, the cadmium concentration in the Gyugakubi water supply that brought agricultural water to the contaminated area was also improved at the same time, to the upstream level of 0,1 ppb (Table 4-1,Fig.4-4 and 4-5).