ArticleARE THE TRADITIONAL CONCEPTS OF THE STRUCTURES OF HUMIC SUBSTANCES REALISTIC?Burdon, J.Author Information School of Chemistry, The University, Birmingham B15 2TT, UK. E-mail: [email protected] Received April 16, 2001; accepted Aug. 21, 2001. Soil Science: November 2001 - Volume 166 - Issue 11 - p 752-769 Buy Abstract It is suggested that compounds with traditional structures for humic substances (HS) do not exist in soils but that soil organic matter consists instead of mixtures of plant and microbial constituents plus the same constituents in various stages of degradation. That is, HS are mixtures of plant carbohydrates plus microbial carbohydrates, plant proteins plus microbial proteins, plant lipids plus microbial lipids, etc., together with partially degraded lignins and tannins, etc., and with microbial materials such as melanins and other polyketides. Purely biological processes and abiotic reactions, such as the Maillard reaction, are discussed and rejected as major sources of HS. Factors such as the color of HS, their electron spin resonance spectra, fluorescence, molecular weight, the presence of mellitic acid, and others do not require compounds of the traditional type to be present in HS; they are entirely explicable on the basis of plant/microbial mixtures. Artifact formation is common in HS studies, and it can be seriously misleading. © 2001 Lippincott Williams & Wilkins, Inc.