CHEMICAL CHARACTERIZATION OF THE ORGANIC-MATTER IN FOREST SOILS BY CURIE-POINT PYROLYSIS GC MS AND PYROLYSIS FIELD-IONIZATION MASS-SPECTROMETRY

The chemical composition of three different forest humus layers (mull, moder, mor) was studied by flash pyrolysis-gas chromatography/electron impact mass spectrometry (Py-GC/EIMS) and by temperature-programmed, direct pyrolysis-field ionization mass spectrometry (Py-FIMS) in order to evaluate the relevance of individual humus constituents for geoecological and geochemical processes. Pyrolysis products with a molecular weight up to 430 Dalton that derive from carbohydrates, intact and degraded lignins, proteins, lipids, polyphenols, and aliphatic polymers were identified by accurate mass measurements in the FI mode and by GC/EIMS. However, the pyrolysis products that caused the main differences between the Py-FI mass spectra of the three humus types in the mass range above m/z 300 were not recorded by Py-GC/EIMS. Their assignments are based on in-source pyrolysis and high resolution FIMS. They derive mainly from biphenyl-, diarylpropane-, phenylcoumaran-, and resinol-type subunits from lignin, and phytosterols and their dehydration products. Furthermore, free and bound lipids such as homologous series of n-fatty acids (C22-C32), alkyl monoesters (C40-C52), and aromatic esters (C27-C34) are found. © 1990.