Abstract
Copper(II) complexing capacity (CuCC) of the Watarase river water was determined by dithizone extraction technique. The CuCC values obtained at the upper stream were in a range of 10-7-10-6 mol dm-3, which corresponded to the values obtained at the middle reaches. Total and free copper(II) concentrations in the river water were also determined by thenoyltrifluoroacetone (TTA) extraction technique. The total copper(II) concentration was higher in the upper stream than in the middle one. However, they were significantly low for the CuCC of the water. This result indicates that most of the copper(II) in the river water exists as complexes bound to naturally occurring ligands that contribute to the CuCC. From the evaluation of the side-reaction coefficient in the TTA extraction，it was found that the free copper(II) concentration in the river water was lower than 10-11 mol dm-3.
