Die Bodenkultur - Journal for Land Management, Food and Environment
S. A. MOHAMAD, O. H. DANNEBERG, K. SCHAFFER and M. H. GERZABEK:
Characterization of humic substances from town refuse and refuse-sewage sludge composts
Four samples of different age from the compost plants "Biomull" (Vienna) and "Traiskirchen" (Lower Austria) were collected for characterization of humic sub-stances. Humic substances were extracted from compost samples and fractionated into fulvic acid (FA) and brown humic acid (BHA). FA and BHA-extracts were investigated by exclusion chromatography on controlled pore glass (CPG) of 17 nm pore diametre. Elution was followed by on line measurements of extinction at 400 nm and of organic C distribution, specific extinctions were calculated as a measure of purity of humic substances. Maxima of specific extinctions were used for calculation of the organic C distribution of pure humic substances in the chromatograms. Differences to the measured organic C distribution were attributed to the accompanying non-humic substances.
Maximal specific extinctions were between 30-75 for "pure fulvic acids" and 80-280 for "pure brown humic acids'', Fresh compost showed a low BHA: FA-ratio. Polymerization of humic substances during ripening of the compost and thereafter depolymerization of the humic substances was observed.
Key-words: chromatography, humic substances, .refuse-sewage sludge compost, town refuse compost.