Carbon-13 NMR and chemical characterization of particle-size separates of peats differing in degree of decomposition

Abstract

Solid-state 13C CPMAS NMR was used to examine particle-size fractions of six peats varying in degree of decomposition. With decreasing particle size, the chemical shift region attributed to O-substituted carbon decreased relative to that of aliphatic carbon, while changes in the aromatic, phenolic and carboxyl regions were small. These effects were similar to those previously seen with increasing decomposition with depth, and were more pronounced for the more decomposed peats. They were also consistent with chemical indications of increased decomposition in the smaller particle size fractions. It was also noted that carbohydrate content determined by chemical analysis was considerably lower than indicated by the relative intensity of the O-substituted region of the spectra (60–105 ppm). Principal component and factor analysis were applied to the NMR and pyrophosphate data. The principal components so derived reflected the empirical observations noted, but provide a more objective means of sample comparison.