TESTING A HUMIC SPECIATION MODEL BY TITRATION OF COPPER-AMENDED NATURAL-WATERS

Experiments were carried out in which samples of natural waters that h ad been acidified and amended with copper nitrate were titrated with b ase, and the activity of Cu2+ was monitored with an ion-specific elect rode. The results could be explained in terms of the interactions of C u2+ with inorganic and organic ligands, as calculated using the Winder mere Humic Aqueous Model (WHAM). Optimised fits were obtained by adjus ting the concentration of ''active'' fulvic acid. The active fulvic ac id represented about 80% of the total concentration of dissolved organ ic matter for upland pools and lakes, and about 40% for lowland rivers . (C) 1998 Elsevier Science Ltd.