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Nanoscale Biogeocomplexity of the Organomineral Assemblage in Soil

Application of STXM Microscopy and C 1s-NEXAFS Spectroscopy

^a Dep. of Crop and Soil Sci., Cornell Univ., Ithaca, NY 14853
^b Dep. of Physics and Astronomy, State University of New York, Stony Brook, NY 11794

View larger version (90K): [in a new window]   Fig. 1. Conceptual framework for the interplay between minerals, organic matter, and pore space determining the C stabilization in the soil organomineral assemblage.

View larger version (70K): [in a new window]   Fig. 2. STXM micrographs for an interior aggregate region taken (a) below 281 eV and (b) above 290 eV the carbon absorption edge. Contrast in the C and mineral density is shown in the ratio micrographs (c) calculated from–log [I/Io] where I = (281 eV – 282 eV) and Io = (290.6 eV – 291.5 eV).

View larger version (38K): [in a new window]   Fig. 3. STXM micrographs for an exterior aggregate region taken below (a) 281 eV and (b) above 290 eV the carbon absorption edge. Contrast in the C and mineral density is shown in the ratio micrographs (c) calculated from–log [I/Io] where I = (281 eV – 282 eV) and Io = (290 6 eV – 291.5 eV).

View larger version (40K): [in a new window]   Fig. 4. Cluster pixel plots of components 2 and 3 show spectral characteristics of mineral and organic matter, color-coded for each cluster (color legend on top axis). Yellow color represents mineral cluster pixels separated from cluster pixels of organic and organomineral complexes by the blue (a) and green (b) clusters of pore space pixels. Pixel separation with an optical density gradient (axis component 2), distinguishes C chemical species in the organic or organomineral matter, and is noticeable only in (a) but not (b) on the axis component 3.

View larger version (103K): [in a new window]   Fig. 5. Composition thickness maps of the main thematic regions in the interior of a micro-aggregate. Composition maps show (a) bright white regions of minerals, (b)organomineral complexes of carboxylic-C forms, (c) organomineral coatings of aromatic, (d)aliphatic-C forms, and particulate forms of aromatic-aliphatic-C. White arrows show small nanometer pores in mineral matrix. Grayscale arrows point at small nanometer pores in organomineral complex.

View larger version (41K): [in a new window]   Fig. 6. Composition thickness maps of the main thematic regions at the exterior of a micro-aggregate. Composition maps show (a) bright white regions of minerals, (b) organomineral complexes of carboxylic-C forms, and (c) organomineral coatings of aromatic, carboxylic-C forms. Black arrows show small nanometer pores in mineral matrix. Black arrows point at small nanometer pores in organomineral complex.

View larger version (33K): [in a new window]   Fig. 7. Spectral signatures of the composition thickness maps of the interior area shown in Fig. 5, with both (a, b, c, and d) uncorrected PS-Io and (e, f, g, and h) CM-Io corrected spectra. Spectra (a) and (e) refer to mineral and pore space signatures, respectively. Spectra b and c show elevated optical density as a result of absorbance by mineral matter. Residual errors for the fitted spectra e, f, g, and h are shown with their root variance, .

View larger version (21K): [in a new window]   Fig. 8. Spectral signatures of the composition thickness maps of the exterior area shown in Fig. 6, with both (a, b and c) uncorrected PS-Io and (d, e and f) CM-Io corrected spectra. Spectra (a) and (d) refer to mineral and pore space signatures, respectively. Spectra (b), (c), (e), and (f) show elevated optical density as a result of absorbance by mineral matter. Residual errors for the fitted spectra (d), (e), and (f) are shown with their root variance, .