Proposal of evaluation of soil organic matter sorption capacity
2009
Barančíková, G., Soil Science and Conservation Research Institute, Bratislava (Slovak Republic)
It is well known that sorption capacity of humic substances (HS) is much higher in comparison to clay minerals. The two most important functional groups in this respect are the carboxyl and phenolic-OH groups. Since fulvic acids (FA) exhibit higher total acidity values than humic acids (HA), results of study on chelation and complexation analyses indicate that metal chelatation by humic acids (HA) appears more effective than by FA. The larger molecules and the more complex structures of HA are accepted to be the reason for more binding sites and higher binding capacity in contrast to FA, which are smaller and less complex. Humic acids are also higher in aromatic structures than fulvic acids. For this reason proposal of evaluation of SOM sorption capacity use basic quantitative and qualitative humus parameters - content of soil organic carbon (SOC), ratio of carbon of humic and fulvic acids (CHA/CFA) and optical parameter (Q46) but also such selected parameters of HA chemical structure, which the most effect its sorption capacity - content of carboxylic groups and aromatization degree (a), which take into account humification degree of HA. High sorption humus capacity is characterized by SOC content more than 2, CHA/CFA more than 1, Q46 less than 4.5, COOH more than 4 and a more than 50.
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