Chemists are trained and equipped to study pure compounds and relatively simple mixtures from which pure compounds can be isolated. The study of pure compounds leads ultimately to molecular structures, which provide much greater insight into reactivity and physicochemical properties of organic compounds.  Humic substances are a highly complex mixture of organic compounds whose overall reactivity and physicochemical properties are readily observed and lead quickly to difficult questions.  How can humic substances resist biodegradation for hundreds to thousands of years?  How can humic substances have measurable buffer capacity over the entire pH range of soils and natural waters?  How can humic substances absorb light over a continuous wavelength range of 200-700 nm?  How do humic substances interact with living organisms in soils, sediments, and natural waters, where non-living organic matter is much more abundant than living organic matter?  These questions have intrigued scientists for more than 200 years and have provided the impetus for much research on humic substances.  Chemists have followed a familiar path of fractionation of humic substances in their quest for pure compounds and molecular structures through which reactivity and physicochemical properties can be explained and understood.  This lecture will provide a broad overview of this quest.

Structural characterization of humic substances

248th National Meeting (2014)

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