2002 年 39 巻 p. 247-255
Inorganic ions as well as nitrogen and phosphorus affect the eutrophication in a closed water area. To investigate the runoff characteristics of inorganic ions in Uji river basin in Kochi prefecture, Japan, continuous surveyswere conducted every one or two weeks during from June 2000 to June 2001. It was found through the survey that Na+and Cl-were diluted according to the increase of flow rate, while NO3--N and PO43--P concentrations increased oppositely. Principal component analysis revealed that 80% of the information in the original data set was integrated into 3 principal components;(1) dilution due to the increase of flow rate, (2) photosynthesis, and (3) nitrification. The analysis also demonstrated that the influence of the dilution was detected particularly at the day having a larger flow rate, that the effect of photosynthesis appeared more significantly from July to the beginning of September, and that nitrification did notoccur perfectly from February to May.