A COPPER COMPLEXATION APPROACH FOR COASTAL SEAWATER INVOLVING CHELEX ION-EXCHANGE EQUILIBRIA AND POTENTIOMETRIC TECHNIQUES

Knowledge of organic complexation and metal ion speciation may be impo rtant in predicting the environmental behaviour of trace elements. In this paper a combined experimental approach based on three techniques is given: ion exchange, computerized potentiometric stripping metal de terminations (PSA) and potentiometry with ion selective electrode [CU( II)-ISE], to obtain information about the complexing capacity, L(T), t he conditional stability constants, K'(CuL), and the dissolved Cu(II) speciation in seawater. In coastal seawater the results agree quite we ll with those obtained by other methodologies. This permits to conclud e that free Cu2+ ion concentrations in the dissolved fraction of El Wa y and Santa Maria Island seawater samples, are controlled by organic l igands, presumably of humic and proteinaceous nature. Labile copper sp ecies are also present as minor but important fraction of the total di ssolved copper. In seawater subjected to overload of metallogenic wast es, the fraction containing labile copper species is predominant. In b oth these media the log K'(CuL) vs L(T) relationship is discussed.