Metal Ion Humic Colloid Interaction

Abstract

Natural organic matter dissolved in natural water, such as humic and fulvic acids, is known to strongly interact with the polyvalent metal ions by complexation, colloid formation, and redox reactions. Aqueous speciation and thus bioavailability and mobility are significantly dominated by metal–humic/fulvic acid interaction. In order to study the impact of humic/fulvic acid on metal ion speciation, a broad variety of analytical methods are available. They range from physicochemical separation of complexed and noncomplexed species up to sophisticated spectroscopic methods, such as X‐ray spectroscopy, that allow insight into the coordination environment of humic/fulvic acid bound metal ions and the structure of those compounds. Based on available knowledge, geochemical models have been developed in order to predict metal ion speciation in humic/fulvic acid containing natural water. Still a matter of current research is the partly pronounced kinetic stability of humic/fulvic acid bound trace metal species. Very strongly delayed metal ion dissociation from humic colloids under natural groundwater conditions may have some impact on the assessment of humic colloid relevance on the transport of toxic metal ions such as nuclear waste derived radionuclides.