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PREDICTING CHEMICAL REACTIVITY OF HUMIC SUBSTANCES FOR MINERALS AND XENOBIOTICS: USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY AND VIRTUAL REALITY
Bailey, G W., L. G. Akim, AND S. M. Shevchenko. PREDICTING CHEMICAL REACTIVITY OF HUMIC SUBSTANCES FOR MINERALS AND XENOBIOTICS: USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY AND VIRTUAL REALITY. Chapter 2, Clapp, C.E., M.H.B. Hayes, N. Senesi, P.R. Bloom, and P.M. Jardine (ed.), Humic Substances and Chemical Contaminants. Soil Science Society of America, Madison, WI, , 41-72, (2001).
Elucidate and model the underlying processes (physical, chemical, enzymatic, biological, and geochemical) that describe the species-specific transformation and transport of organic contaminants and nutrients in environmental and biological systems. Develop and integrate chemical behavior parameterization models (e.g., SPARC), chemical-process models, and ecosystem-characterization models into reactive-transport models.
In this chapter we review the literature on scanning probe microscopy (SPM), virtual reality (VR), and computational chemistry and our earlier work dealing with modeling lignin, lignin-carbohydrate complexes (LCC), humic substances (HSs) and non-bonded organo-mineral interactions. Graphical representations of SPM images, VR images of the structure and morphology of minerals and HSs, outcome of molecular mechanics (MM), molecular dynamics (MD) and simulated annealing calculations of these surfaces are presented via a CD ROM. Significant findings from these simulations include: (1) SPM provides the capability to investigate the structure and morphology of environmental surfaces; (2) VR software and animated computer graphics enhance our capability to visualize and interpret 3-D surface structures; (3) flexible linear polymers were found to undergo drastic conformational changes when approaching the mineral surface; (4) MD simulations suggest high stability of the organic polymer coatings on mineral surfaces; (5) sorption energies are compound-specific and depend on the sorbate-sorbent orientation; (6) humic polyanions bind to mica surfaces via cation bridges; and (7) computational chemistry provides the capability to simulate the chemical reactivity and energetics of environmental surfaces for chemical contaminants.
We present an integrated methodology to simulate the chemical reactivity of minerals. HSs, organo-mineral aggregates and demonstrate an approach whereby we can study the interactions of xenobiotics with organo-mineral aggregate surfaces.
Record Details:Record Type: DOCUMENT (BOOK CHAPTER)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL EXPOSURE RESEARCH LABORATORY
ECOSYSTEMS RESEARCH DIVISION
PROCESSES & MODELING BRANCH