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ROLE OF IRON AND MANGANESE OXIDES IN BIOSOLIDS AND BIOSOLIDS-AMENDED SOILS ON METAL BINDING
Citation:
Hettiarachchi**, G. M., J A. Ryan*, AND K G. Scheckel*. ROLE OF IRON AND MANGANESE OXIDES IN BIOSOLIDS AND BIOSOLIDS-AMENDED SOILS ON METAL BINDING. Presented at American Chemical Society's 2002 National Meeting, Application of Synchrotron Radiation to Environmental Studies: Characterization of Trace Elements, Orlando, FL, 4/7-11/2002.
Description:
Biosolids contain high levels of Fe, Mn, and Al. Surfaces of freshly precipitated metal oxides, especially Fe and Mn, are known to be highly active sites for most dissolved metal ion species. We nw have metal sorption/desorption data that illustrate the importance of Fe and Mn fractions in biosolids-amended soils to toxic trace metal retention. Extgraction procedures used to separate Fe and Mn fractions in these experiments are not completely phase specific/selective and may not provide definitive information on either the phase(s) responsible for metals retention or the reaction "mechanisms". It is apparent that resolution of this issue can be accomplished by identification of the forms of metals in soil system. Previously researchers have attempted to characterize metals in biosolids using X-ray diffraction and scanning electron microscopy, after fractionation of samples using nondestructive physicochemical methods (particle size, density, and magnetic susceptibility). These studies however, were unable to provide definitive information regarding metal speciation most probably due to lack of quantity and/or crystallinity of the metal oxides in biosolids. Moreover, bulk XAS would also not be appropriate for Fe and Mn oxides in biosolids samples, which are complex and heterogeneous. We employed X-ray microprobe analysis and micro-X-ray adsorption spectroscopy (micro-XAS) at GSECARS, Advanced Photon Source, Argonne, IL to determine association and "mechanisms" of metals with biosolids Fe and Mn compounds. Results from elemental mapping, possible Fe and Mn phases, and association of metals of interest with Fe and Mn phases in the biosolids and biosolids-amended soils will be presented.