Behavior of phenolic substances in the decaying process of plants

Abstract

The relationship between the adsorption of phenolic substances In soils and the chemical structures of phenolics or the type of soil were Investigated by batch and column methods. Fifteen soil samples containing kaolinic, montmorillonltlc, and allophanic clay minerals and 6 phenolic acids, P-hydroxybenzolc, vanillic, p-coumaric, ferulic, protocatechuic, and a-resorcyllc acids were used for the study. The soil samples were collected from the plough layer of crop fields and the sublayer of uncultivated soils. The behavior of phenolic substances in liolls was also discussed. The results are as follows: 1) The adsorption of phenolic acids was influenced by the type of soil. In the case of both arable Bolls and subsoils, allophanic soils adsorbed more phenolic acids than kaolinic and montmorillonitic soils. 2) The adsorption of phenolic acids was also influenced by the chemical structures of the phenolic substances. Among the phenolic acids used, protocatechuic acid was adsorbed in the largest amount, and the importance of the catechol moiety for the adsorption of phenolics or humic acid was Indicated. 3) From these results, it was tentatively concluded that in mineral arable solis most phenolics exuded from plant residues or produced during the decomposition process were rapidly leached with water from the surface horizon of the soil, and that in humus-allophanic arable salls, these phenolics, especially polyphenolic compounds, were largely adsorbed, thus contributing to humus formation. 4) Among arable soils, organic matter content correlated highly with the adsorption of each phenolic acid. Subsoils with extremely low organic matter contents, however, adsorbed greater amounts of each phenolic acid than arable loils for all types of soils. 5) The other properties of soils such as pH value, clay and free iron contents were not closely related to the adsorption of phenolic acids.