Specific variation rates of substances in a creek located along the lower reaches of the Chikugo River

摘要

The creek network area along the lower reaches of the Chikugo River in Japan is facing serious water pollution problems. A model for water quality analysis is needed to prioritize possible countermeasures. The discharge load from paddy fields and changes in water quality in a creek seem to control the accuracy of the model in a study area which is bounded by the Ariake Sea, the Yabe, Okinohata, and Shiotsuka rivers. This paper focuses on the latter factor. This paper introduces the investigation methods and results of "specific variation rates of substances" (SVRS) in a creek. Several kinds of investigations and measurements were carried out. The results of previous research were also reviewed for reference. The SVRS in a creek were estimated to be a -1,000 approx -2,000 mg centre dot m~(-2) centre dot d~(-1) of COD, -200 approx 100 mg centre dot m~(-2) centre dot d~(-1) of T-N and -10 approx 120 mg centre dot m~(-2) centre dot d~(-1) of T-P. This study, which arrived at SVRS by combining severalmethods, demonstrated the difficulty of obtaining reliable results. It is desirable to develop a more appropriate method.