Structural domains in peat as revealed by physical fractionation, sequential chemolysis and 15N and 13C CPMAS NMR spectroscopy

The NMR spectra suggested: (i) a lack of heterocyclic N forms in the coarsest peat granulometric fractions, and their highest concentration in fractions less than 100 μm in size; (ii) the preferential accumulation of heterocyclic N forms in the humic acid fraction isolated with a chelating extractant (Na4P2O7); (iii) the survival of amide N forms after acid hydrolysis indicating that only a portion of the amide N forms were present in hydrolyzable form; (iv) the fact that heating of the peat was the treatment which most significantly increased the heterocyclic N moiety.