Mohiuddin


Die Bodenkultur - Journal for Land Management, Food and Environment

A. S. M. Mohiuddin and O. H. Danneberg:

Controlled pore glass chromatography of humic substances from some organic soils of Austria and Bangladesh

Summary

Humic substances from three typical organic soils, two from Austrian Histosols and one from Bangladesh peat (Dystric Histosol), were exhaustively extracted with a chelating resin and water and subsequently fractionated into brown humic acids and fulvic acids, respectively. These gross humic fractions were chromatographically investigated using a column packed with controlled pore glass (CPG) of 16.7 nm pore diameter. Concentrations of both coloured material and carbon were simultaneously recorded in the chromatograms against partition coefficient (Kd). Specific extinctions at 400 nm were calculated and maximal values were taken as constants specific for ‘pure’ humic substances.

Accompanying non-humic substances were obtained by difference.

Results revealed that the Terric and Eutric Histosol of Austria and Dystric Histosol of Bangladeshwere typically dominated by brown humic acids (BHA). The percentages were 56.05, 56.68 and 85.05, respectively. The specific extinctions obtained for ‘pure’ gross humic fractions of these soils were: fulvic acids (FA) 82.2, 55.9 and 48.3; brown humic acids (BHA) 210.1, 173.9 and 251.1 and grey humic acids (GHA) 292.0, 242.4 and 345.2, respectively. The number of peaks and their corresponding Kd values in the different humic fractions as recorded in the elution curves were: FA with a characteristic single peak at 0.70–0,75, BHA with double peaks at 0.00–0.10 and 0.60–0.65 and GHA also with a couple of peaks at -0.05–0.00 and 0.35–0.45. The non-humic substances were characterized by three types of fraction, i,e, low, medium and high in molecular size, in which predominance of medium molecular sized non-humicmaterials was distinct. The humic to non-humic ratio’s were high, about 60:40. The ranges of colour quotients (E400/E600) for three studied soils were: FA 8.18–10.57, BHA 5.54–5.67 and GHA 3.57–3.95.

Key words: Humic substances, organic soils, Histosols, chromatography on Controlled Pore Glass, “pure” humic substances, specific extinction of “pure” humic substances, non-humic substances.