title: Phosphorus speciation in sequentially extracted agro-industrial by-products: evidence from X-ray absorption near edge structure spectroscopy.
abstract: The phosphorus (P) in agro-industrial by-products--a potential source of freshwater eutrophication but also a valuable fertilizer--needs to be speciated to evaluate its fate in the environment. We investigated to what extent X-ray absorption near edge structure (XANES) spectroscopy at the P K- and L2.3-edges reflected differences in sequentially extracted filter cakes from sugarcane (Saccharum officinarum L.) (FIC) and niger seed (Guizotia abyssinica Cass.; NIC) processing industry in Ethiopia. The P fractionation removed more labile (54%) and H2SO4-P (28%) from FIC than from NIC (18% labile, 12% H2SO4-P). For the FIC residues after each extraction step, linear combination (LC) fitting of P K-edge spectra provided evidence for the enrichment of Ca-P after the NaOH-extraction and its almost complete removal after the H2SO4-treatment. The LC-fitting was unsuccessful for the NIC samples, likely because of the predominance of organic P compounds. The different proportions of Ca-P compounds between FIC (large) and NIC (small) were more distinctive in L2-than in the K-edge XANES spectra. In conclusion, the added value of complementary P K- and L2.3-edge XANES was clearly demonstrated, and the P fractionation and speciation results together justify using FIC and NIC as soil amendments in the tropics.
authors.affiliation: Univ. of Rostock, Institute for Land Use, Justus-von-Liebig Weg 6, D-18051 Rostock, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Kruse
authors.forename: Wakene
authors.initials: W
authors.lastname: Negassa
authors.forename: Narayana
authors.initials: N
authors.lastname: Appathurai
authors.forename: Lucia
authors.initials: L
authors.lastname: Zuin
authors.forename: Peter
authors.initials: P
authors.lastname: Leinweber
mesh_terms: D015502:Absorptiometry, Photon; D000383:Agriculture; D005591:Chemical Fractionation; D004784:Environmental Monitoring; D007220:Industrial Waste; D010758:Phosphorus / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D007220:Industrial Waste; D010758:Phosphorus