Humin geochemistry

Humin has been regarded as the most intractable component of SOM. It must be considered to be a very important component, however, because typically it represents more than 50% of the organic carbon in a soil (Kononova, 1966 Stevenson, 1982,1994) and more than 70% of the organic carbon in unlithified sediments (Durand and Nicaise, 1980 Rice, 2001). The definition of humin (Section 1.3.3) is similar to that of a protokerogen (Calvin and Philip, 1976 Rice, 2001), which is often used in petroleum geochemistry to describe insoluble organic matter in unlithified sediments. 

Hue, A. Y., and Durand, B. (1973). Etudes des acides humiques et de L humine de sediments. Recents consideres comme precurseurs des kerogenes. In Advances in Organic Geochemistry 1973, Tissot, B., and Bienner, E, eds., Editions Technip, Paris, pp. 53-72. 

Publications on humic substances are dominated by discussions on humic acids and fulvic acids, with relatively little discussion of humin. The former two fractions can be dissolved in aqueous media which facilitates their isolation and study. The geochemistry of humin is discussed by Hatcher et al. in Chapter 11 the presence and nature of humin in various environments are also discussed in a number of other chapters in this book. For example, Stevenson (Chapter 2) discusses humin from soils, Ishiwatari (Chapter 6) provides a rather extensive discussion of humin from lake sediments, and Vandenbroucke et al. (Chapter 10) consider humin in marine sediments. 

The relationship of humin to kerogen, and the role of these substances as precursors to coal and petroleum are discussed by Hatcher et al. in Chapter 11. Schnitzer discusses the nature of nitrogen in humic substances in the last chapter (Chapter 12) of the geochemistry section. 

---