Pyrolysis gas chromatography-mass spectrometry of humic substances extracted from canadian lake sediments

摘要

Humic substances (HS) were extracted with the aid of 0.1 M Na_4P_2O_7 and 0.5 M NaOH solutions from the sediments of four lakes located in the Sudbury area in Ontario, Canada, namely, Tilton, Clearwater, Silver and Ramsey Lake. The humic acid (HA) and fulvic acid (FA) extracts, purified and characterized using classical methods i.e., ele-mental analysis, FTIR spectroscopy, and CPMAS ~(13)C NMR (see N. Beizile, H.A. Joly, and H. Li. (1997)). were sub-mitted to pyrolysis — gas chromatography — mass spectrometry (Py—GC—MS). The pyrolysates of the HA and FA extracts were found to be complex mixtures of at least 200 compounds. Results based on statistical analysis of the abundances of pyrolysis products (of known origin) revealed trends similar to those obtained from the classical bulk characterization techniques. The Py—GC—MS technique supported the observation, obtained from classical methods, that the chemical composition of HA extracts varied less significantly among the four lake sediments than for the FA ex-tracts. The abundances of lignin and carbohydrate pyrolysates showed the highest variation among the FA extracts. Py-rolysis products originating from lignin, carbohydrates, proteins, and fatty acids were identified.