Abstract
A method for evaluation of the metal-binding ability of river water is reported. It involves a Cu titration and an ion-selective electrode detection. Scatchard's plot and two binding site model approximation was used for the analysis of data. The ability could be determined for river waters containing more than 3 mg/l of organic carbon. River waters measured at pH=6.3 in 0.1M KNO3 gave 1〜6 μmol/l with pK=6.1〜6.9 for strong binding sites and 3〜22 μmol/l with pK=4.6〜5.4 for weak binding sites. The complexing capacity of the strong binding sites apparently correlated well with dissolved organic carbon concentration. One mg of dissolved organic carbon gave 0.21〜0.55 μmol of the capacity. Dissolved Cu concentration was also proportional to the capacity. It accounted for about 1/10 of the capacity of the strong binding sites. Combination of the present method with an adsorption onto Amberlite XAD-2 resin suggested a possibility to specify organic fractions responsible for the complex formation.
