Clay minerals organic matter

Like sediments, colloids are often important in sorbing and transporting arsenic in soils (Sadiq, 1997 Waychunas, Kim and Banheld, 2005). Colloids may consist of clay minerals, organic matter, calcium carbonate, and various aluminum, manganese, and iron (oxy)(hydr)oxides (Sadiq, 1997). Important iron (oxy)(hydr)oxides include goethite, akaganeite (/J-FeO(OH)), hematite, ferrihydrites, and schwertman-... 

The multireaction approach, often referred to as the multisite model, acknowledges that the soil solid phase is made up of different constituents (clay minerals, organic matter, iron, and aluminum oxides). Moreover, a heavy metal species is likely to react with various constituents (sites) via different mechanisms (Amacher et al 1988). As reported by Hinz et al. (1994), heavy metals are assumed to react at different rates with different sites on matrix surfaces. Therefore, a multireaction kinetic approach is used to describe heavy metal retention kinetics in soils. The multireaction model used here considers several interactions of one reactive solute species with soil matrix surfaces. Specifically, the model assumes that a fraction of the total sites reacts rapidly or instantaneously with solute in the soil solution, whereas the remaining fraction reacts more slowly with the solute. As shown in Figure 12.1, the model includes reversible as well as irreversible retention reactions that occur concurrently and consecutively. We assumed that a heavy metal species is present in the soil solution phase, C (mg/L), and in several phases representing metal species retained by the soil matrix designated as Se, S, S2, Ss, and Sirr (mg/kg of soil). We further considered that the sorbed phases Se, S, and S2 are in direct contact with the solution phase (C) and are governed by concurrent reactions. Specifically, C is assumed to react rapidly and reversibly with the equilibrium phase (Se) such that... 

Pearson V. K., Sephton M., Kearsley A. T., Bland P. A., Franchi 1. A., and Gilmour 1. (2002) Clay mineral-organic matter relationships in the early solar system. Meteorit. Planet. Sci. 37, 1829-1833. 

Sorption in aquifers takes place mainly on clay minerals, organic matter and oxides, and is differently modeled depending on the properties of the solid. Clay minerals such as smectite and illite carry a charge due to... 

In accordance with modern theories, the main mechanism of metal sorption in various soils is the heterogenic surface sorption of metals by soil particles. In the sorption process, the various metals react with different functional groups of various soil compounds, like clay minerals, organic matter, oxides of Fe, Mn, Al, Si, etc. Various mechanisms of Me sorption in soil and soil solution are connected with various forms of their existence in soil such as exchangeable, specifically sorbed, occluded by oxides and hydroxides, bounded with organic matter and included into interlayer spaces of silicon minerals. In this study Tessier et al (1979) s method has been... 

Phosphate ion exchange in soils In soils, phosphate and other ion exchange processes occur on the surfaces of the solid phases (clay minerals, organic matter, and mineral surfaces). Ion exchange reactions are important for maintaining an equilibrium between the solid phase and the solution (soil pore water). Thus, it is important that we understand the origin of surface charge of the solid phase. 

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. 

Birkel, U., Gerold, G., and Niemeyer, J. (2002). Abiotic reactions of organics on clay mineral surfaces. In Soil Mineral-Organic Matter-Microorganism Interactions and Ecosystem Health Dynamics, Mobility and Transformation of Pollutants and Nutrients. Violante, A., Huang, P. M., Bollag, J.-M. and Gianfreda, L., eds., Elsevier Science B.V., Amsterdam,The Netherlands, pp. 437 447. 

Soil Mg originates from the decomposition of minerals such as dolomite, biotite, olivine, serpentine, and chlorite. Soluble Mg may be held in the exchangeable form on soil clays or organic matter. 

Accompanying the release of carbon there also occurs a release of nitrogen as ammonia, as well as other mineral elements present. A portion of this ammonia may be immobilized biologically, may be sorbed by the organic and inorganic colloids present, or may be fixed chemically by the clays or organic matter present. However, the major portion of the nitrogen is normally oxidized to nitrites and nitrates. The various pro-... 

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