Synchrotron X-Ray Absorption and Vibrational Spectroscopic Methods Assessing Metal-Organic Interactions.

Chemical speciation of metals in the environment is vital in assessing their toxicity, reactivity, and mobility.  Most important reactions of metals occur at the interface between the aqueous phase and both mineral and organic solids.  This project focuses on the role of metal-organic complexation in solutions containing Cu(II), as this important interaction can determine the environmental fate of copper in surface waters, soils, and sediments.  Furthermore, by using Cu(II) as a indirect probe we can gain access to the reactive sites of organic matter that are important for characterizing, not only organic matter in general, but more importantly, its reactivity to contaminants in the soil and environment.  Measurements at the Cu(II) L-edge were chosen for this study as they provide direct, core-level access to the bonding orbitals in metal-ligand complexes. Distinct shifts can be seen at the L₃-edge that corresponds to changes in the ligand field.  Measurements were taken on both humic materials and low molecular weight organic acids most relevant to environmental systems, i.e., those that contain carboxylic, alcohol, and amine function groups.