『(Abstract)
　Intensive manure application is an important source of diffuse phosphorus (P) pollution. Phosphorus availability from animal manure is influenced by its chemical speciation. The major objective of this study was to investigate the P speciation in raw and anaerobically digested dairy manure with an emphasis on the calcium (Ca) and magnesium (Mg) phosphate phases. Influent and effluent from an on-farm digester in Wisconsin were sampled and sieved, and the 25 to 53μm size fraction was dried for X-ray powder diffraction (XRD) and P K-edge X-ray absorption near edge structure (XANES) analyses. Struvite (MgNH4PO4・6H2O) was identified in both the raw (influent) and anaerobically digested (effluent) manure using XRD. Qualitative analysis of P K-edge XANES spectra indicated that the Ca orthophosphate phases, except dicalcium phosphate anhydrous (DCPA) or monetite (CaHPO4), were not abundant in dairy manure. Linear combination fitting (LCF) of the P standard compounds showed that 57.0 and 43.0％ of P was associated with DCPA and struvite, respectively, in the raw manure. In the anaerobically digested sample, 78.2％ of P was present as struvite and 21.8％ of P was associated with hydroxylapatite (HAp). The P speciation shifted toward Mg orthophosphates and least soluble Ca orthophosphates following anaerobic digestion. Similarity between the aqueous orthophosphate (aq-PO4), newberyite (MgHPO4・3H2O), and struvite spectra can cause inaccurate P speciation determination when dairy manure is analyzed solely using P K-edge XANES spectroscopy; however, XANES can be used in conjunction with XRD to quantify the distribution of inorganic P species in animal manure.』

Abbreviation
(Introduction)
Materials and methods
　Sample collection and characterization
　X-ray powder diffraction analysis
　X-ray absorption near-edge structure analysis
　　Phosphorus standards
　Data collection and pre-treatment
Results and discussion
　X-ray powder diffractograms of manure samples
　Qualitative XANES analysis of phosphorus standards and manure samples
　Least squares linear combination fitting of the XANES data
　Environmental implications of manure phosphorus speciation
　Probable improvements in the XANES and XRD methods
Conclusions
Acknowledgments
References