Carbohydrates natural organic matter

Due to variations in the soil, such as humic constituents, sand fractions, clay minerals, peat minerals, wood rests, algal toxins, and deposits of shell lime, different reactions take place. The natural organic matter (NOM) in an aquifer is a complex mixture of substances, such as humic acids, fulvic acids, amino acids, carbohydrates, lipids, lignin, and waxes. 

A further informative example is the organic matter—CO2 couple, which is the principal reductant in natural systems. Consider a solution in equilibrium with atmospheric CO2 at neutral pH and containing 10p,M CH2O , where CH2O represents average organic C in natural systems, whose composition is similar stoichiometrically to that of carbohydrates. The half reaction is... 

Methane fermentation in natural ecosystems is usually described as a two-stage system in which nonmethanogenic bacteria ferment organic matter such as carbohydrate yielding such products as acetate, formate, hydrogen, and carbon dioxide. The methanogenic bacteria are restricted... 

Many methods have been used for the isolation of polysaccharides from soil. Except for one case, < the maximum yield obtained accounts for only about 2% of the. soil organic matter. The average content of carbohydrate, however, is estimated to lie between 5 and 20% of soil organic matter. The nature and state of the remaining carbohydrate material is not known. So far, the primary aim of the various workers has actually been the isolation of an undegraded polysaccharide material free from inorganic and organic impurities, and the completeness of the extraction has only been of secondary interest. 

Use of the simple carbohydrate formula to represent organic matter has the advantage of simplifying reactions, but it also means the reactions are very approximate representations of the complexities found in nature (see e.g. Box 4.10). 

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