STRUCTURAL INVESTIGATION OF ISOLATED AQUATIC FULVIC AND HUMIC ACIDS IN SEEPAGE WATER OF WASTE DEPOSITS BY PYROLYSIS-GAS CHROMATOGRAPHY MASS-SPECTROMETRY

Fulvic and humic acids isolated from seepage waters of four municipal waste landfills and one hazardous waste landfill were analysed by Curi e point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Fur thermore, fulvic and humic acids were subjected to acid hydrolysis fol lowed by alkaline hydrolysis. The hydrolysis products were analysed by gas chromatography/mass spectrometry (GC/MS) and the residues by Py-G C/MS. Results show that the pyrolysis products of the fulvic and humic acids at a pyrolysis temperature of 770 degrees C are similar before and after acid/alkaline hydrolysis. The pyrolysis products are compose d mainly of aromatic compounds like alkylbenzenes, alkylnaphthalenes a nd higher condensed aromatic substances; aliphatic constituents are de tectable only in trace amounts. At a pyrolysis temperature of 510 degr ees C the pyroloysis products of the isolated fulvic and humic acids a re dominated by benzoic acids, phenols and straight chain acids. The c ompound composition is similar to the one obtained from GC/MS analysis of the soluble hydrolysis products. Results indicate that the fulvic and humic substances from leachate water of waste deposits are built u p of an aromatic nucleus, which is not completely decomposed upon pyro lysis at 510 degrees C. The nucleus seems to be surrounded by hydrolys able structural units composed of aromatic acids and phenols linked vi a ester and ether bonds to the fulvic respectively humic acid core. Co mparison with pyrolysis products obtained from soil humic substnaces i ndicates a higher degree of aromaticity and thermal stability of part of the macromolecular network. In addition results indicate that the s tructural composition of the fulvic and humic acids in leachate waters from waste deposits is independent from leachate quality. (C) 1997 El sevier Science Ltd.