COPPER CONCENTRATION AND CU-II ACTIVITY IN SAN-DIEGO BAY

Copper ion activity and concentrations of voltammetrically defined dis solved, surface bound, and tightly bound colloidal copper in samples f rom San Diego Bay were measured independently using potentiometric and stripping voltammetric methods, respectively. 'Free' copper, calculat ed from activity, was approximately three orders of magnitude less tha n the concentrations of the dissolved, surface bound and tightly bound copper fractions (indicating a high degree of complexation) and over- all, was well correlated to them, suggesting a common, heterogeneous, copper matrix, of probable organic nature, whose distribution is contr olled by physical mixing. This finding supports the aggregate or 'onio n' model of copper speciation in seawater. Within the bay, we also enc ountered environments in which copper activity was not directly correl ated to concentration and we attribute this to local production of org anic ligands by microalgae.