ABSTRACT
Natural materials in terrestrial and aquatic environments are closely related. Extensive research of the neutralization properties of fulvic and humic acids has been complicated by the physical complexities of these substances. The early emphasis of metal-humate interactions research centered on the determination of the so-called binding capacity of the natural organic acid. The fluorescence of humic substances has been used to study their complexation with a number of metal ions. Gel permeating/filtration has been employed in studies of metal-humate interaction. There are very weak acid groups present in humic-acid substances. Once correction for metal ion response to salt concentration levels is available the description of metal-ion binding by humic substances still remains subject to considerable uncertainty because of their functional site heterogeneity. The transport of metal ions in natural aquatic systems is significantly affected by their (metal ions) adsorption on oxide surfaces.
