Die Bodenkultur - Journal for Land Management, Food and Environment
A. S. M. Mohiuddin and O. H. Danneberg:
Characterization of humic substances from Austrian cambisols by chromatography on CPG
Humic substances from three Austrian Cambisols were exhaustively extracted with a chelating resin and water and grossly fractionated into fulvic acids (FA) and brown humic acids (BHA). These, together with the unfractionated extract, were further investigated chromatographically using a column packed with Controlled Pore Glass (CPG) having a pore diameter of 16,7 nm. The effluents of the column were continuously analysed for the concentrations of both colored material and carbon, which were both recorded against partitition coefficient (Kd). Specific extinctions per unit of C and at 400 nm were calculated in the course of the chromatograms and maximum values were taken as constants specific for ‘pure’ humic substances. Accompanying non humic substances were obtained by difference.
Results revealed that Dystric Cambisol and Calcaric Cambisol had the typical distribution pattern of humic fractions, i.e. a domination of BHA; in Eutric Cambisol, however, grey humic acids [GHA, obtained by the difference extract – (BHA + FA)] were unusually high. The specific extinctions obtained for the ‘pure’ humic substances were in the expected range and comparable to literature values. FAs always showed a single elution peak with a Kd of 0.7–0.75, BHA’s had double peaks at Kd values of 0.05 and 0.6, while GHA’s had a couple of peaks between 0 and 0.55. The color quotients of the different ‘pure’ humic fractions in the studied soils were shown to have usual ratios, i.e. inversely related with the molecular size of the humic substances. Non humic substances were, in general, characterized by different fractions as well low, medium and high in molecular size. The ratio of ‘pure’ humic substances to non humic substances was, as expected, approximately 2:1.
Key words: Cambisols, humic system, chromatography, Controlled Pore Glass, ‘pure’ humic substances, non humic substances.