Chapter 1 – The Chemical Structure of Humic Substances: Recent Advances

Publisher Summary This chapter discusses the precursors of humic substances (HS) and reviews the pyrolysis behavior of the most important biomacromolecules and humic substances. The pyrolysis products are not considered to be building blocks due to thermal reactions and rearrangements produced, which limits the usefulness of the pyrolysis technique for structural analyses. The chapter provides information on a novel pyrolysis method, that is, the simultaneous pyrolysis/methylation, which is able to alleviate limitations imposed by the technique to take pyrolysis data back to the genuine chemical structure from which it originated. The chemical composition of humic fractions is governed by extraction, fractionation, and purification procedures; humic fractions with different chemical compositions can be extracted from the same soils. This heterogeneity reflects the various inputs of organic matter to different soils and its different solubility behavior, and is one of the factors that incited scientists to propose standard procedures aiming at the reproduction of the chemical characteristics of humic fractions.