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Phosphate speciation in excessively fertilized soil: a 31 P and 27 Al MAS NMR spectroscopy study
Author(s) -
LOOKMAN R.,
GEERTS H.,
GROBET P.,
MERCKX R.,
VLASSAK K.
Publication year - 1996
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.1996.tb01379.x
Subject(s) - chemistry , soil water , genetic algorithm , apatite , phosphate , nmr spectra database , extraction (chemistry) , goethite , nuclear magnetic resonance spectroscopy , oxalate , nuclear chemistry , dithionite , spectral line , mineralogy , adsorption , inorganic chemistry , geology , chromatography , stereochemistry , soil science , biochemistry , physics , organic chemistry , astronomy , evolutionary biology , biology , enzyme
Summary Both P and Al MAS NMR spectra of samples of excessively fertilized sandy soil provided information about the P and Al speciation. Peak deconvolution was used to interpret reliably and quantitatively the 31 P NMR spectra recorded. Most of the P was found to be associated with Al. Part of the P exhibited a chemical shift that could be attributed to octocalcium phosphate, amorphous calcium phosphate or apatite. Apatite has, however, never been reported to occur in sandy soils of temperate climates. A dithionite extraction used to remove interfering Fe from the samples also removed most of the octahedral Al‐P phase. After oxalate extraction more than 99% of the original P signal disappeared. About 7.5 to 11 % of the total oxalate extractable P of the excessively fertilized soil was present as a Ca‐P phase, even though these soils are slightly acid to acid. The estimated size of the Ca‐P phase roughly corresponds to the size of the labile P pool of these soils, as assessed in long‐term batch desorption experiments. It still remains unclear whether the labile P pool should be attributed solely to such a Ca‐P phase.