Figures

- Speciation of Phosphorus in Phosphorus-Enriched Agricultural Soils Using X-Ray Absorption Near-Edge Structure Spectroscopy and Chemical Fractionation

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Figure 1   Stacked P K-XANES (X-ray absorption near-edge structure) spectra for selected phosphate standards: (A) P related to Fe, (B) Ca phosphates, and (C) others. Data are background- and baseline-corrected and normalized to the P K-edge at 2149 eV.

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Figure 2  Least-squares fits of the P K-XANES (X-ray absorption near-edge structure) spectra of the five soil samples: (A) sb2.1-A, (B) Ma2-A, (C) PV2-A, (D) Ma3-B, and (E) AI2-B (P/ferrihydrite, P/goethite, and P/alumina = PO4 adsorbed on ferrihydrite, goethite, or alumina; octaCaPO4 = octacalcium phosphate; hydroxyap. = hydroxyapatite; NC FePO4 = noncrystalline FePO4). For PV2-A and AI2-B, the first best fit among the best solutions reported in Table 3 is illustrated. 

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Figure 3  Relationships between the proportions of different P species determined by X-ray absorption near-edge structure (XANES) fitting versus those obtained via sequential chemical fractionation for corresponding pools: (A) P associated with Ca; (B) P related to Fe or Al phase.