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Fig. 6. Relationships between the proportions of total P in operational fractions of a sequential extraction vs. the proportion of total P in different P species determined by XANES linear combination fitting (biosolids and dairy manure samples only): (a) NH4Cl- and NH4F-extractable P vs. Al-hydroxide-bound P (Al-P); (b) NaOH-extractable P vs. ferrihydrite-bound P (Fe-P) and phytic acid (IHP; NPL = normal poultry litter); (c) H2SO4-extractable P vs. hydroxylapatite (HAP) and ß-tricalcium P (TCP); and (d) dithionite–citrate–bicarbonate (DCB)- and H2SO4-extractable P vs. HAP and TCP (APL = alum-treated poultry litter). *, **, and *** Significant at the 0.05, 0.01, and 0.001 probability levels, respectively.
