大淀川水系の水質と微生物数の変動

概要

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It was feared the water quality of The Oyodo River in Miyakonojyo district had been made worse, so a water analysis of this river and 4 tributaries (branched rivers) were carried out periodically from July 1997 to November 1998. The average BOD was 2.68 mg/l, the average concentration of NO_3-N was 1.88mg/l, and that of PO_4 was 0.60mg/l. The NO_3-N of The Toshimi River that is one of the tributaries had the highest value, 2,55mg/l. The number of aerobic bacteria and E.coli group's bacteria in The Oyodo River were ca. 10^3-10^4 cells/ml cfu and ca. 10^1-10^2 cells/ml cfu, respectively. We supposed those results depended on agriculture. In August 1998,water analysis was carried out one point on each of The Tama River (Kanagawa Prefecture), The Yamato River (Osaka Metropolitan Prefecture), The Yodo River (ditto), and The Udji River (Kyoto Metropolitan area) that exist near large cities in Japan. The results of those analyses showed BOD and the concentration of NO_3-N in The Oyodo River were similar as those of The Yodo River and The Tama River, but the number of E.coli groupe's bacteria in The Oyodo River was the largest of them all.