APPLICATION OF PYROLYSIS-GAS CHROMATOGRAPHY-MASS SPECTROMETRY TO THE CHARACTERIZATION OF HUMIC SUBSTANCES RESULTING FROM DECAY OF AQUATIC PLANTS IN SEDIMENTS AND WATERS

Pyrolysis-GC-MS, elemental analysis and i. r. spectroscopy reveal major differences between humic substances from aquatic plants (algae and aquatic phanerogams) and lagoonal, marine and lacustrine deposits. Algae are enriched in proteins and their pyrolysis yields numerous nitrogenous by-products (alkylpyrroles, nitriles and alkylpyridines) along with aromatic compounds which are thought to reflect the decomposition of individual amino-acids (styrene, toluene, phenol and p-cresol). These compounds are less abundant in the pyrolysis products of humic substances from phanerogams with increasing amounts of methoxyphenols, characteristics of lignins. In the deposits of the Kerguelen Islands and of a 'blue lake' in Greenland, the importance of algal populations is emphasized by pyrolysis products corresponding to nitrogenous and carbohydrate derivatives.