Sorption of watersoluble organic matter on kaolinite and muscovite in a laboratory model experiment

The interaction of water-soluble organic matter (DOM) in aqueous extracts obtained from H horizon samples of peaty-podzolic-gleyic soil on kaolinite and muscovite were studied. The extracts contained different amounts of water-soluble Corg. mainly with molecular masses of about 20 kDa, represented mainly by hydrophilic compounds, but with different ratios of hydrophobic and hydrophilic components and with different concentrations of compounds containing aromatic structures. It has been established that the sorption of DOM components under the experimental conditions depends on the Сorg. concentration in the extracts, on the ratio of hydrophilic and hydrophobic components, on the mineral : solution ratio and practically does not depend on pH. Hydrophobic components and aromatic compounds are more sorbed on kaolinite surface compared to muscovite. The observed decrease of C org. sorption on both minerals when sorption per unit area of external surface in the experiments with the mineral : solution ratio of 1:50 in comparison with the ratio of 1:10 may indicate both the heterogeneity of sorption centers on the surface of minerals and the competition for these centers between the components of DOM. No significant changes in the curves of molecular weight components of DOM after interaction with kaolinite and with muscovite were revealed.