種別 国内論文 No. 61 年度 2012
論文名 1970年代から2010年の渡良瀬川河川水の銅及びヒ素と濁度との関係
Relationship between Copper and Arsenic Concentrations and Turbidity in the Surface Water of Watarase River
著者名 齋藤陽一、森勝伸、角田欣一、板橋英之
掲載誌名 環境科学会誌
40年間にわたる渡良瀬川の検査から得られた銅及びヒ素の経年変移を統計学的に解析した。銅、ヒ素共に濃度は大きく減少していたことが明らかになった。銅については1976年度の草木ダム貯水開始により水質は大きく安定化した。ヒ素については、山元での発生源対策や鉱山の閉坑により、ダム貯水開始以前より減少傾向にあったことが判明した。特定の年度で高い数値を示すのは、台風の襲来により草木ダムの放流が行われ、上流の鉱山由来の濁質が下流に到達したためと推察された。
The aim of this study is to determine the relationship between the variation in copper and arsenic concentrations and the rurbidity in water samples collected from 1970 to 2010 at Akaiwa along Watarase River, including data from 1967 to 1969 for arsenic. The relationship between copper concentration and turbidity and that between arsenic concentration and turbidity were evaluated by testing the significance of the correlation coefficients obtained from their approximations of copper and arsenic concentrations in the river water samples for 40 years were related to the turbidity of the water. However, the reductions of the concentrations were somewhat different between copper and arsenic. Copper concentration had significantly reduced since Kusaki dam began storing water in 1976. In contrast, arsenic concentration had reduced before this event. From 1980 to 2010, the average copper and arsenic concentrations stable at values <0.014mg/L and <0.004 mg/L, respectively , and the turbidity has been less than 17. However, events of high turbidities and high copper and and arsenic concentrations have occurred irregularly in several years, especially in 1990. These events had been affected by discharge of water from Kusaki-dam after the typhoons that stuck in August and/or September in the corresponding years.