title: Heterogeneity and liability of Pb(II) complexation by humic substances: practical interpretation tools.
abstract: The complexation of Pb(II) by natural organic matter (NOM) is better described by taking into account the dependence of the strength of binding on metal loading conditions. The utility of a linear differential equilibrium function for interpretation of metal ion binding data is demonstrated. This approach considers the binding intensity (log K*) as a function of metal ion loading (theta = bound metal/binding site concentration). Three methods for calculating this function are presented: -direct calculation from metal titration curves, -direct calculation from polarograms, and -compilation of data derived from interpretation of complexation in terms of one- or two- binding sites (e.g. Scatchard analysis), i.e. Cc (complexation capacity = effective site concentration)-K pairs. Heterogeneity also impacts on the apparent lability of complexes; complexes formed at the lowest metal loadings are the least labile.
authors.affiliation: Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, Switzerland. montserrat.filella@cabe.unige.ch
authors.forename: M
authors.initials: M
authors.lastname: Filella
authors.forename: R M
authors.initials: RM
authors.lastname: Town
mesh_terms: D001665:Binding Sites; D002614:Chelating Agents / Q000737:chemistry*; D006812:Humic Substances / Q000737:chemistry*; D007854:Lead / Q000737:chemistry*; D008024:Ligands; D011048:Polarography
chemical_list: D002614:Chelating Agents; D006812:Humic Substances; D008024:Ligands; D007854:Lead