Abstract
This study was conducted to elucidate the changes of turbidity and concentrations of suspended solids (SSs) and heavy metals (Cu, Zn, As, and Pb) in Watarase River at Akaiwa during the rapid elevation in turbidity from 1971 to 2011, which was the result of typhoons and local heavy rainfalls. In this study, high-turbidity phenomena correspond to turbidity of over 100° in river water. In the Watarase River, high-turbidity phenomena observed 28 times from 1971 to 2011. The Kiryu City Waterworks Bureau of Waterworks measured the turbidity, and the concentrations of SSs and heavy metals in raw water samples collected every 2 h. The relationships between turbidity and SS concentration and between turbidity and heavy metal concentration during the high-turbidity phenomena were considerably stronger correlations than those at normal turbidity, although the slopes of approximate expressions from the relationships decreased with the passage of time. Moreover, the source of heavy metals were expected to mainly be waste materials from the Ashio mine sediment-disposal facility, because the elution of heavy metals as well as the turbidity and SS concentration reduced after the cleanup of the facility and upgrading of the surrounding environments by implementing administrative policies.
