Study of soil humic substances by cross-polarization magic angle spinning 13C nuclear magnetic resonance and pyrolysis-capillary gas chromatography Original Research Article

Two humic acids (HAs) and two fulvic acids (FAs) isolated from red earth soil and dark lossial soil were characterized using the cross-polarization magic angle spinning (CPMAS) 13C NMR spectra and pyrolysis-capillary gas chromatography electron impact mass spectrometry (Py-GC/MS) analyses. The aromaticities of four samples were obtained from the 13C NMR spectra. Up to 38 pyrolysis products were identified using a mass data base. Only 26 pyrolysis products were common to all four samples. No alkanes and only three olefins were formed, and almost all products during pyrolysis were aromatic compounds. The aromaticity of soil humic substances in question was clearly demonstrated; aromatic units with aliphatic chain substituents were important building blocks.