COMPARISON BETWEEN CP MAS C-13-NMR AND PYROLYSIS-GC/MS IN THE STRUCTURAL CHARACTERIZATION OF HUMINS AND HUMIC ACIDS OF SOIL AND SEDIMENTS/

The chemical structure of humins (HUs) and humic acids (HAs) of terres trial and marine environments was investigated by cross-polarization m agic angle spinning C-13-nuclear magnetic resonance spectroscopy (CP/M AS C-13-NMR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC /MS). Samples of HUs and HAs were obtained from sediments of the Adria tic Sea, the Lagoon of Ravenna (Adriatic Sea) and the Bubano Lake as w ell as from an agricultural soil. HUs displayed pyrograms and NMR spec tra different from those of related HAs. According to NMR spectra HUs were more aliphatic and contained fewer carboxyl groups than HAs, whil e pyrolysates of HUs were characterized by higher levels of products a rising from carbohydrates and lower levels of lignin methoxyphenols wi th respect to HAs. The relative content of paraffinic carbons determin ed by NMR was in good agreement with the relative abundance of unbranc hed aliphatic hydrocarbons released by pyrolysis. Both techniques evid enced the importance of polymethylene structures in HUs.