Potential Complexing Ability of Surface Water Organic Matter: I. Role of Various Groups in Metal Ion Binding

Abstract

The results of experimental studies of the potential complexing ability of dissolved organic matter (DOM) of surface water bodies with respect to Al3+, Fe3+, and Cu2+ ions are discussed. The concentrations of certain groups of natural organic substances, in particular, humic substances, carbohydrates, and protein-like compounds as the most probable complexing ligands, have been determined in water samples collected from the Kanev reservoir (upper section) and Lake Verbnoe (Kiev). The potential complexing capacity of DOM with respect to all bound metals has been estimated at 11.0–15.5 and 14.9–15.8 µmol/L for the Kanev Reservoir and Lake Verbnoe, respectively, without appreciable seasonal changes. A significant part of metal ions are bound into complexes during the first day of the experiment (total duration 28 days), and the equilibrium state is achieved mainly within 7 days. Humic substances as the largest component of DOM contribute most to the complexation of metal ions. Participation of carbohydrates in metal binding also increases in the summer–autumn period. Cationic metal complexes with proteinaceous compounds are minor components. Seasonal variations in the metal ion binding by particular groups of DOM are also considered.