ABSTRACT
A review on the application of several spectroscopic techniques, including visible-ultraviolet (UV-Vis), infrared (IR), fluorescence, electron spin reso nance (ESR), Mdssbauer, and nuclear magnetic resonance (NMR), to metalhumic substances studies in environmental and laboratory-modeled systems is provided. The discussion is focused on the molecular and mechanistic aspect of metal-humic substance complexation, i.e., on the physicochemical nature of sites involved and type of binding and formation mechanisms and stability of metal-humic substance complexes. Information generated by spectroscopic techniques, particularly fluorescence quenching spectroscopy, on quantitative aspects of metal-humic substance interactions, such as ligand complexing capacity and equilibrium constants of complexation, are discussed. Advantages and limitations of each technique are also considered. It is inferred that the simultaneous utilization of UV-Vis, IR, fluorescence, and ESR spectroscopies, in combination with chemical derivatization, along with fluorescence and/or ESR probes, and, where possible, with the support of Mossbauer and NMR
spectroscopies, represents the most advisable rationale in approaching the complicated chemical problems encountered in investigating metal-humic sub stance interactions in natural environments.
