Humus classes

Nonhumic substances Compounds belonging to known classes of biochemistry, such as amino acids, carbohydrates, fats, waxes, resins, and organic acids. Humus probably contains most, if not all, of the biochemical compounds synthesized by living organisms... 

Approximately two-thirds of soil organic matter can be accounted for in the humified fraction, whereas the remaining exists in the nonhumified fraction. These two classes of compounds are not easily separated from one another, as some of the nonhumic materials such as carbohydrates may be covalently bound to the humic matter (Stevenson, 1986). Chemical characteristics of nonhumic and humic substances have been discussed in Section 5.4.3. In this section, the role and function of soil humus in biogeochemical cycling will be discussed. 

Marine polymeric DOC has often been given the special name of Gelbstoff (Ger., yellow material, after the name given it by Kalle cf. his review of the subject in 1966) it was first recognized in the 1930s as the basis for the color of seawater. On the basis of a cursory similarity to the humic substances of soils and freshwaters, it has been called marine humus, although it may actually bear practically no molecular resemblance to the other polymers of this type. In an early comparison of the two classes of material, Sieburth and Jensen (1968) concentrated both marine and freshwater Gelbstoff on nylon columns, eluted them with NaOH,... 

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