9614920 Hesterberg The geochemical evolution of heavy metal speciation in the weathering environment of a contaminated soil determines the long-term fate of metals. The goal of this basic research program is to understand at the molecular level the binding of copper (II) and arsenate in an organo-mineral model system comprising an aqueous mixture of goethite and humic acid extracted from natural organic matter. Macroscopic solubility studies have shown that the adsorption of metals in organo-mineral systems is not always described by linearly combining contributions from each of the mineral adsorbents - humic acid and oxide mineral. Synchrotron XAS, particularly extended x-ray absorption fine structure (EXAFS) spectroscopy and x-ray absorption near edge (XANES) spectroscopy, will be used as a primary tool to determine the nature of Cu (II) and AsO4 binding on goethite containing surface-adsorbed humic acid.
