摘要：Samples collected from the municipal drinking water of Kyoto, Osaka and Kobe were analyzed by ion chromatography to clarify the ionic components of the tap water and to know how reflect the characteristics of the Lake Biwa-Yodo River water quality, because the domestic drinking water of these cities was supplied after various purification steps for the renovation of the water of the same basin of the Lake Biwa-Yodo River. Ions in the samples were found to exist reflecting both the pollution of the raw water near the intake points of the water purification plants, and the reagents used in the water treatment process of each plant. Correlation matrices of the components of the detected ions revealed that NO3- influenced by the human activities had high correlations with Na+ and K+. The increase of the amount of NO3- contained in the tap water of the cities in the lower part of the basin indicated that NO3- produced in the upper stream could not be removed by the usual purification process. It was also found in the present study that SO42- increased stepwise in the tap water after every treatment process at the respective purification plants. However, the levels of the detected ions were far lower in the light of the Waterworks Law of Japan and WHO Guidelines for the quality of drinking water, indicating that the water renovation of the Lake Biwa-Yodo River has been well controlled.
