The Science of the Total Environment, 81/82 (1989) 447-457 447 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands GEL PERMEATION CHROMATOGRAPHY OF WATER-SOLUBLE ORGANIC MATTER WITH DEIONIZED WATER AS ELUENT II. SPECTROSCOPIC AND CHEMICAL CHARACTERIZATION OF FRACTIONS OBTAINED FROM AN AQUEOUS LITTER EXTRACT G. GUGGENBERGER, I. KOGEL-KNABNNR, L. HAUMAIER and W. ZECH Lehrstuhl ffir Bodenkunde und Bodengeographie, Universit~t Bayreuth, Postfach 10 12 51, D-8580 Bayreuth (F.R.G.) SUMMARY Water-soluble organic matter extracted from a mull litter horizon under ash and alder was fractionated on Fractogel TSK. With a single fractionation step six fractions could be obtained. The fractions were studied by IR and solution-state *~C NMR spectroscopy as well as by methanolysis. According to '3C NMR spectroscopy, carbohydrates are the dominant constituents of the bulk sample. Alkyl-carbon components are of minor importance and there is only little evidence of aromatic compounds. Data from gas chromatography of methanolysis products shows that sugar acids, sugar alcohols, and cyclitols considerably contribute to the carbohydrate proportion of some of the fractions. INTRODUCTION Water-soluble organic matter in forest soils exerts a profound influence on soil formation processes, e.g. mineral weathering and podzollzation (ref. I). The importance of dissolved organic matter in determining the availability and toxicity of trace metals in soils has also been recognized (ref. 2). Forest litter releases considerable amounts of water-soluble organic substances, ranging from 0.9 % (Plnus sylvestris) to 16.5 % (Fraxlnus excelsior) of dry weight of litter (ref. 8). Only few studies have been conducted on the chemical structure of water-soluble organic matter in soils. The water-soluble organic substances are complex mixtures of well defined low molecular weight compounds, e.g. carbohydrates, amino acids, and phenolic acids (refs. 3-6), and of high molecular weight polyelectrolytes of indefinite structure (humic compounds) (refs. 6-7). Better information on structure and composition is obtained from spectroscopic investigations of chemically more homogeneous fractions. Several authors have used GPC on Sephadex gels with deionlzed water as eluent to fractionate humic substances (refs. 8-I0) and aqueous extracts of forest soil horizons (ref. II). They have concluded that the fractions obtained differ chemically. In the present paper, GPC on Fractogel TSK with deionized water as eluent is used to fractionate the aqueous extract of a mull litter horizon. Compared to GPC 0048-9697/89/$03.50 © 1989 Elsevier Science Publishers B.V.