EXPERIENCE IN STUDYING AND CHARACTERIZATION OF SOIL HUMIC SUBSTANCE POLYDISPERSITY

Humic substances were sequentially extracted with carboxylic resin and 0.1 N NaOH. The extracts wer fractioned by the method of gel chromatography on Sephadexes G-100 and G-25 in distilled water with addition of NaOH (pH 7.0), with addition of Triton X-100, and in 6 M urea solution. Polydispersity of soil humic substances from different regions are compared. Space-and-time variability of the polydispersity is estimated. Formation of submolecular aggregates of humic substances is discussed. The influence of extraction method and of fractioning conditions on parameters measured is considered. The dependence is underlined if the polydispersity of humic substances on soil and ecologic conditions.