PYROLYSIS-(GAS CHROMATOGRAPHY) MASS-SPECTROMETRY OF AGRICULTURAL SOILS AND THEIR HUMIC FRACTIONS

Curie-point pyrolysis-gas chromatography/mass spectrometry and temperature-programmed in-source pyrolysis-field ionization mass spectrometry have been used for the chemical characterization of the organic material in agricultural soils with organic carbon contents between 1 and 1.5%. The results obtained from whole-soil samples, extracetable humic substances and nonextractable humin by both techniques indicate for the Ap of a Gleysol thermal degradation products of carbohydrates, intact and/or biodegraded lignin, flavonoids, tannins and/or polyphenols, lipids, aliphatic polymers, and nitrogen-containing compounds. On a qualitative basis similar results have been obtained for the Ap of a Luvisol. The alkylbenzenes, alkylnaphthalenes, (di)alkylphenols, and alkyltoluenes identified are of special interest because these aryl-alkyl compounds demonstrate covalent linkages between aliphatic chains and aromatic subunits in soil organic matter. This type of linkage between individual subunits of the complex and polydisperse organic material enables the flexibility of rigid aromatic systems.