Inorganic Solid Phase

Soil consists of inorganic and organic solids, the soil solution, soil air, and living organisms. Soil chemistry is primarily concerned with the solid and liquid phases and their interactions. This chapter deals with the inorganic solid phase of soils, primarily the clay fraction, and its important properties. The clay fraction ( 2 jum in size) carries out most of soil chemistry. The larger sand (50-2000 /rm) and silt (2-50 /im) fractions are much less chemically active and are composed largely of quartz (SiC 2), which is rather inert. 

Minerals of the clay fraction of soils are largely secondary, that is, formed by low-temperature reactions and either inherited from sedimentary rocks or formed directly in the soil by weathering. These secondary (authigenic) minerals in soils commonly 

Other important constituents of the clay fraction are the so-called free oxides. These are Al, Fe, Mn, and Ti hydroxyoxides that accumulate in the soil as weathering removes silicon. The free oxides range from amorphous to crystalline and are often the weathered outer layer of soil particles. The hydroxyoxides, plus amorphous aluminosilicates such as allophane, are the most important clay-sized nonlayer minerals in soils. 

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Spacie A. 1994. Interactions of organic pollutants with inorganic solid phases are they important to bioavailability In Hamelink JL, Landrum PF, Bergman HL, Benson WH, editors. Bioavailability, physical, chemical and biological interactions. Boca Raton (FL) Lewis Publishers, p 12-31. 

The inorganic solid phase of any soil consists of a number of minerals displaying different degrees of weathering susceptibility. The extent of weathering of these minerals depends on the stabilities of the minerals and the physical and chemical environment in which the minerals are immersed in the soil, including the supply of water and the removal or transport of the products of weathering (see Chapter 6 Carrels and Christ, 1965 Kittrick, 1977 Colman and Dethier, 1986). 

The formation of biominerals is a complex phenomenon. In order to obtain a feeling for the conditions under which inorganic solid phases in biological systems are stable, it is of some interest to look at solubility products. Solubility products, A s°p, have a meaning only if the composition of the solid phase is specified. For a solid compound with the general composition the... 

Table 5.5. Summary of selected properties of inorganic solid-phase components... 

Stability of common polymers, and consequently, thermal degradation of mercaptide molecules ean be also carried out with the mercaptide dissolved into a polymeric medium. In this case, a finely dispersed inorganic solid phase, embedded in polymer, is generated. Materials based on clusters confined in polymeric matrices are called nanocomposites [Mayer, 1998 Caseri, 2000]. Both semiconductor-polymer and metal-polymer nanocomposites have unique functional properties that can be exploited for applications in several advanced technological fields (e.g., optics, nonlinear optics, magnetooptics, photonics, optoelectronics) [Caseri, 2000]. 

H. BiUnski, S. Kozar, M. Plavsic, Z. Kwokal, and M. Branica. Trace metal adsorption on inorganic solid phases imder estuarine conditions. Marine Chemistry 32 225-233,1991. 

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