Phenolic Compounds in Soils of Hydrosequences and Developmental Sequences of Spodosols

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Abstract
The extraction of low molecular weight phenolic compounds from pedons of two hydrosequences and two developmental sequences was investigated. Seven phenolic compounds were identified in Na4P2O7 extracts: three benzoic acids—protocatechuic, p‐hydroxybenzoic, and vanillic acids; two aldehydes—p‐hydroxybenzaldehyde and vanillin; and two cinnamic acids—trans p‐coumaric and ferulic acids. Identification of the compounds was by cochromatography with authentic standards. In general, the total phenolic content increased going from the somewhat excessively drained to the somewhat poorlydrained members of the hydrosequences and from the least‐developed to the most‐developed members of the Spodosol developmental sequences. The substituted benzoic acids accounted for most of the phenolic compounds in all horizons. While p‐hydroxybenzoic and vanillic acids dominated in the surface horizons, protocatechuic acid was found in higher concentrations in the spodic horizons. Aluminum and Fe maxima also occurred within horizons that had protocatechuic acid as the prevalent phenolic compound. The results suggest that Al and Fe chelate complexes with protocatechuic acid may play a role in the formation of spodic horizons.