Soil organic matter colloidal property

Soil organic matter also has a strongly pH-dependent charge. The charge develops mostly by H+ dissociation from carboxylic and phenolic groups. Table 5.5 summarizes the colloidal properties of the major components of the soil s clay fraction. 

For other metals, such as Cd, Zn, Cu, and Ni, no simple sohd with properties simulating metal solubility in soils exists. Lindsay (1979) previously advocated the concept of a fictitious sohd phase called soil-Cu. There are a number of theoretical and semi-theoretical models that have been used to describe (ad)sorpfion of transition metals onto reactive surfaces (Fe, Mn or Al oxides soil organic matter). While probably more correct in a mechanistic sense than the solubility relations discussed below, these models have not proven to be particularly useful with intact soils because they contain a very complex assemblage of colloidal surfaces. Moreover, they do not seem to adequately predict increases in metal solubility with increases in total soil metal burden. This has led an increasing number of researchers to develop purely empirical models that describe trace-metal solubility as a function of simple soil parameters such as pH, organic matter content, and total metal content (e.g. McBride et al., 1997 Gray et al.,... 

Because of its colloidal properties, soil organic matter (particularly... 

Metal oxides have a significant role in influencing physical, chemical, and biological properties of soils. They may exist as ciystalline minerals, as short-range ordered (SRO) mineral colloids, or as surface coatings on clay minerals and organic matter. Organic compounds influence the formation, transformation, and surface properties of these metal oxides. The SRO A1... 

Choudri, M. B. and Stevenson, F. J. (1957). Chemical and physicochemical properties of soil colloids. III. Extraction of organic matter from soils. Soil Sci. Soc. Am. Proc. 21, 508-513. 

The mobility of contaminants and their subsequent removal depend also on their sorption capacity to soil components. Therefore, soil properties, particularly those related to the presence of mineral colloids (e.g. montmorillonite, chlorite, kaolinite) and organic matter, additionally challenge the remediation of mixed contaminated soils. 

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