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Phosphorus Speciation of Sequential Extracts of Organic Amendments Using Nuclear Magnetic Resonance and X-ray Absorption Near-Edge Structure Spectroscopies

^a Dep. of Soil Science, Univ. of Manitoba, Ellis Building, 13 Freedman Crescent, Winnipeg, MB, Canada R3T 2N2
^b Canadian Light Source Inc., Univ. of Saskatchewan, 101 Perimeter Rd., Saskatoon, SK, Canada S7N 0X4
^c current address, Canadian Light Source Inc., Univ. of Saskatchewan, 101 Perimeter Rd., Saskatoon, SK, Canada S7N 0X4

View larger version (9K): [in this window] [in a new window]   Fig. 1. Solution 31P nuclear magnetic resonance spectra of the selected extract with the highest Fe concentration (HCl extracts of hog manure) acquired using (A) 2-s relaxation delay and (B) 20-s relaxation delay and those of the selected extract with the least Fe concentration (HCl extracts of poultry litter) acquired using (C) 2-s relaxation delay and (D) 20-s relaxation delay. A total of 3000 scans were acquired in both cases. Spectra were processed with 3 Hz line broadening. The proportions of the identified peaks are listed in the figures.

View larger version (8K): [in this window] [in a new window]   Fig. 2. 31P nuclear magnetic resonance spectra of biosolids sequentially extracted with (A) water, (B) NaHCO3, (C) NaOH, and (D) HCl. All spectra were plotted with a line broadening of 2 Hz. Chemical shift (ppm) of the peaks at 6.2 ppm was assigned to orthophosphate. In Fig. 1C, peaks at 5.25 and 4.9 ppm were assigned to phosphatidic acid and ß-glycerophosphate, respectively, and –4.43 ppm assigned to pyrophosphate. In Fig. 3D, the peak at –3.74 ppm was assigned to pyrophosphate. Other peaks could not be assigned to any specific P species.

View larger version (8K): [in this window] [in a new window]   Fig. 3. 31P nuclear magnetic resonance spectra of hog manure sequentially extracted with (A) Water, (B) NaHCO3, (C) NaOH, and (D) HCl. All spectra were plotted with a line broadening of 2 Hz. Peaks at 6.2 to 6.28 ppm were assigned to orthophosphate P. In Fig. 2C, peaks at 6.12, 5.13, 4.74, and 4.64 ppm in the ratio 1:2:2:1 were assigned to C-2: C-4 + C-6: C-1 + C-3: C-5 positions of phytic acid. Peaks at 5.37 and 4.98 ppm were assigned to phosphatidic acid and ß-glycerophosphate, respectively. Peaks at 4.89, 4.54, and 4.47 ppm were unidentifiable. In (Fig. 2D), peaks at 5.75, 4.86, 4.44, and 4.3 ppm in the ratio of 1:2:2:1 were assigned to phytic acid.

View larger version (10K): [in this window] [in a new window]   Fig. 4. 31P nuclear magnetic resonance spectra of dairy cattle manure sequentially extracted with (A) water, (B) NaHCO3, (C) NaOH, and (D) HCl. All spectra were plotted with a line broadening of 2 Hz. Peaks at 6.2 ppm were assigned to orthophosphate, peaks at 5.35 or 5.28 ppm were assigned to phosphatidic acid, and peaks at 4.94 ppm were assigned to ß-glycerophosphate. In Fig. 3A, the small peak at 1.78 ppm was assigned to phospholipids. In Fig. 3C, peaks at 6.0, 5.1, 4.74, and 4.59 ppm assigned to phytic acid. Peaks at 4.87, 4.52, 4.49, and 4.27 ppm were unassignable. The peak at –4.4 ppm was assigned to pyrophosphate. In Fig. 3D, peaks at 5.81, 4.9, 4.51, and 4.39 ppm were assigned to phytic acid.

View larger version (8K): [in this window] [in a new window]   Fig. 5. 31P nuclear magnetic resonance spectra of beef cattle manure sequentially extracted with (A) water, (B) NaHCO3, (C) NaOH, and (D) HCl. All spectra were plotted with a line broadening of 2 Hz. The peaks at 6.2 ppm were assigned to orthophosphate. In Fig. 4C, peaks at 6.03, 5.31, 4.76, and 4.62 ppm were assigned to phytic acid. Peaks at 5.31 and 5.97 ppm were assigned to phosphatidic acid and ß-glycerophosphate, respectively. The peaks at 4.89 ppm were unassignable.

View larger version (11K): [in this window] [in a new window]   Fig. 6. 31P nuclear magnetic resonance spectra of poultry litter (manure + beddings) sequentially extracted with (A) water, (B) NaHCO3, (C) NaOH, and (D) HCl. All spectra were plotted with a line broadening of 1 Hz. Peaks at 6.2 ppm were assigned to orthophosphate. In Fig. 5A, the peak at 5.92 and 5.60 ppm were unassigned, and the peak at 5.36 ppm was assigned to phosphatidic acid. In Fig. 5B, peaks at 5.89, 4.98, 4.61, and 4.47 ppm were assigned to phytic acid, the peak at 5.69 ppm was unassignable, and the peak at 5.42 ppm was assigned to phosphatidic acid. In Fig. 5C, the peaks at 6.03, 5.13, 4.77, and 4.62 ppm were assigned to phytic acid. The peaks at 5.23 and 4.97 ppm were assigned to phosphatidic acid and ß-glycerophosphate, respectively. Other peaks were unassigned. In Fig. 5D, the peaks at 5.75, 4.85, 4.45, and 4.33 ppm were assigned to phytic acid.

View larger version (20K): [in this window] [in a new window]   Fig. 7. Linear combination (LC) fit showing proportion of identified P compounds in organic amendments: (a) biosolids, (b) hog manure, (c) dairy cattle manure, (d) beef cattle manure, and (e) poultry litters. The identified P compounds were VAR, variscite (AlPO4·2H2O); HAP, hydroxyapatite (Ca10(PO4)6(OH)2); PHYTIC, phytic acid; Ca salt (C6H6Ca6O24P6); DCPD, dicalcium phosphate dihydrate (CaHPO4·2H2O); and STRUV, struvite (MgNH4PO4·6H2O).

View larger version (15K): [in this window] [in a new window]   Fig. 8. P 1s XANES spectra of labile P (point-by-point difference between spectra of intact amendments and residues after NaHCO3 extraction) and those of matching reference compounds. The spectra were plotted with slight vertical displacement to aid comparison of the features. The vertical line represents (a) shoulder feature of dicalcium phosphate dihydrate (DCPD), (b) feature at 2162 eV peculiar to STRUVITE and VARISCITE, and (c) 2163 eV peak of DCPD.