牛渡川(鳥海山系)の水質に関する研究

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キーワード：河川，水質分析，湧水，海塩成分，大気汚染物質　Ushiwatari river is located in the west side of Mount Choukai by Japan Sea in Yamagata prefecture. Itis one of the famous rivers for water quality in Japan.　We carried out the water analysis about pH, EC, TN, NO_3^--N, NH_4^-N, TP, cation (Na^+, K^+, Ca^, Mg^), anion (F^-, Cl^-, NO_3^-, SO_4^), BOD, COD and water temperature at nine sampling points in the river respectively from May 1997 to February 1998.　The results were as follows;　1. The pH value ranged from 6.34 to 6.75 in all sampling points and the value had a small increase from the upper to the lower stream gradually.　2. The EC value ranged from 4 to 14mS/m. The upper and middle steams were low concentration and suddenly increased at the spring in middle steam.　3. On nitrogen, we measured TN, NO_3^--N and NH_4^+-N. TN and NO_3^--N ranged 0.2-1.3 mg/l and 0.1-1.4mg/l respectively. They were low concentration in the upper and middle stream but suddenly increased in lower stream (rice land area). We could not almost find NH_4^+-N in the river.　4. TP ranged from 0.00 to 0.25 mg/l. The concentration was low in the upper and middle stream but suddenly increased at the spring in middle stream.　5. On cation, we measured Na^+, K^+, Ca^ and Mg^. They ranged 3-10mg/l, 0.4-4mg/l, 0.5-5 mg/l and 0.4-3 mg/l, respectively. Na^+ and Mg^ concentration increased from the upper to the lower stream gradually without influence of the spring. However K^+ and Ca^ were low concentration in the upper and middle without influence of the spring. However K^+ and Ca^ were low concentration in the upper and niddle stream but suddenly increased at the spring in the middle steam.　6. On anion, we measured F^-, Cl^-, NO_3^-, SO_4^. They ranged 0.5-5 mg/l, 6-20mg/l, 0.3-2mg/l, 1.8-3.3mg/l, respectively. These four constituents showed different fluctuations in the steam. F^- increased suddenly at the spring in the middle stream like EC, TP, K^+ and Ca^. Cl^- increased from the upper to the lower stream gradually like Na^+ and Mg^. NO_3^- increased in the lower steam (rice land area) like TN and NO_3^--N. SO_4^ had a small increase from the upper to the lower steam gradually like pH value.　7. The average water temperature was about 10℃ in the river. It was found to have a clear seasonable change. But the lower stream was influenced by the spring and had been kept at 7.2℃ more in the winter.　8. We could not find any clear seasonable change besides water temperature in this river.　9. BOD and COD value ranged under 1mg/l each. The value showed that the river was a good quality water.　10. Nine springs at surrounding Ushiwatari river were good quality waters. The high concentration for TP was characteristic of these springs in Mt. Choukai.　These results suggested that Ushiwatari river had kept a good quality water (BOD, COD) and had no seasonable change besides water temperature, and that the river was influenced by the spring (P, K, Ca and F), riceland (N), sea-salt (Na, Cl and Mg), and then the SO_4 in atmospheric pollution.　Key wards:river, water quality analysis, spring, sea salt, atmospheric pollution.
2004-02-16

牛渡川(鳥海山系)の水質に関する研究

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