Soil interactions organic matter effect

Sorption coefficients quantitatively describe the extent to which an organic chemical is distributed at equilibrium between an environmental solid (i.e., soil, sediment, suspended sediment, wastewater solids) and the aqueous phase it is in contact with. Sorption coefficients depend on (1) the variety of interactions occurring between the solute and the solid and aqueous phases and (2) the effects of environmental and/or experimental variables such as organic matter quantity and type, clay mineral content and type, clay to organic matter ratio, particle size distribution and surface area of the sorbent, pH, ionic strength, suspended particulates or colloidal material, temperature, dissolved organic matter (DOM) concentration, solute and solid concentrations, and phase separation technique. 

Soil is a combination of all of the major components of the surface environment the atmosphere, hydrosphere, lithosphere, and biosphere (Figure 2). It is the mix and interaction of these four components that result in the particular properties of a specific soil. The solid components (mineral and organic matter) make up approximately 50% of soil by volume. Air and water occupy the pore space between the solid phase, and their relative amounts can vary considerably, resulting in important effects on the chemical and biological processes in a soil. Various measurements can be made to express the air-water balance in a soil (Table 2). 

Metal mobility in soils is governed by interfacial processes, such as dissolution. The role of DOM in such processes will be determined by the nature t organic matter-surface associations. The surface complexation model pro-odes a conceptual framework for estimating the contributions of specific DOM components, particularly LMW organic ligands, to the mobilization f metals in soils. With this framework, the effects of humic substances on mineral dissolution can be interpreted to provide some insight into hu--mate-surface interactions. 

Organic materials, either soluble or insoluble, have proven to be effective in reducing the oxidation state of some trace elements (Fendorf, 1995 Hrumg and Germida, 2002 Bolan et al., 2003 Sparks, 2003). Details of the interactions between soil organic matter and trace elements are reported in Chapter 4. 

Rigol, A., Vidal, M., and Rauret, G. (2002). An overview of the effect of organic matter on soil-radiocaesim interaction implications in root uptake. J. Environ. Radioact. 58, 191-216. 

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