Soils mineral composition

Bacteria and their composites with soil minerals or organic matter are capable of taking up a wide range and variety of toxic metals in soil environments. Research done over the last decade or so has greatly improved our understanding of the mechanisms on biosorption of metals and bacte-ria-metal-soil component interactions. However, more studies from molecular level are needed in order to enhance the ability of bacteria and their association with soil components to remediate toxic metals-contaminated soils. The focus of future investigations should be on the mechanisms by which metals are sorbed and bound by bacterial cell surfaces and bacteria-soil/mineral composites. In this connection, X-ray absorption spectroscopy (XAS) is a promising technique because it can provide information about... 

Shen, Y. H. (1999). Sorption of humic acid to soil The role of soil mineral composition. Che-mosphere 38, 2489-2499. 

The frozen hydrate-saturated media formed during these experiments were used for a study of the CO2 hydrate decomposition kinetics in the pore space. The influence of soil mineral composition, ice content and temperature on the CO2 hydrate self-preservation effect was established. It is revealed, that a temperature decrease slows down the CO2 hydrate dissociation low negative temperatures (below -13 C) cause a complete stop of the CO2 hydrate dissociation process. It is also shown that ice forming in the remaining pore space from freezing of unreacted water enhances the CO2 hydrate self-preservation effect. 

Root exudation and microbial action produce organic compounds with a range of composition and molecular weights. These compounds interact with the mineral particles, which also vary in size, shape, ciystallinity, and electric charge (Emerson et al. 1986). Interactions between soil mineral particles, organic matter and microbes can occur at many different size scales, because these materials have a large size range in soils (Fig. 7). 

Since the biogeochemical model PROFILE includes such important characteristics as mineral abundance, another model UPPSALA has been created that allows the researcher to calculate the soil mineralogical composition on the basis of total element content. The combination of these models (PROFILE and UPPSALA) gives the possibility to use existing soil and ecosystem databases for calculating critical loads of acidity in broad-scale regions. 

A further difficulty is the distinction between a concept and an operation, for example in the definition of ion exchange capacity. Operationally, "the ion exchange capacity of a soil (or of soil-minerals in waters or sediments) is the number of moles of adsorbed ion charge that can be desorbed from unit mass of soil, under given conditions of temperature, pressure, soil solution composition, and soil-solution mass ratio" (Sposito, 1989). The measurement of an ion exchange capacity usually involves the replacement of (native) readily exchangeable ions by a "standard" cation or anion. 

Kyuma K. 1978. Mineral composition of rice soils. In Soils and Rice. Manila International Rice Research Institute, 219-235. 

This equation relates the temporal concentration of a diffusing chemical to its location in space. In real soil and aquifer materials, the diffusion coefficient can be affected by the temperature and properties of the solid matrix, such as mineral composition (which affects sorption, a process that can be difficult to separate from diffusion), bulk density, and critically, water content. 

As noted in Sect. 10.1, heterogeneities play a dominant role in the migration of contaminants in the subsurface. Nonuniform, preferential patterns of flow and transport are ubiquitous. It is important to recognize that, at the field scale, contaminant movement generally is very difficult to anticipate. In natural soils and aquifer materials, macropores, soil cracks and aggregates, fissures, solution channels, root paths, and wormholes, as well as variable mineral composition (e.g., clay aggregates... 

Before the availability of artificial fertilizers in the mid-19th century, farms were traditionally organic, with recycling of animal waste, and perhaps with the application of lime on acid soils. Agricultural chemical analysis may have begun with Carl Wilhelm Scheele (1742-1786), the Swedish pharmacist who isolated citric acid from lemons and gooseberries and malic acid from apples. In France, Nicolas Theodore de Saussure (1767-1845) studied the mineral composition of plant ash, and in Britain, Sir Humphrey Davy... 

Many factors affect the mineral composition of potatoes, for example location, stage of development, soil type, soil pH, soil organic matter, fertilization, irrigation, and weather. Genotypic... 

The spring waters of the Sierra Nevada result from the attack of high C02 soil waters on typical igneous rocks and hence can be regarded as nearly ideal samples of a major water type. Their compositions are consistent with a model in which the primary rock-forming silicates are altered in a closed system to soil minerals plus a solution in steady-state equilibrium with these minerals. Isolation of Sierra waters from the solid alteration products followed by isothermal evaporation in equilibrium with the eartKs atmosphere should produce a highly alkaline Na-HCO.rCOA water a soda lake with calcium carbonate, magnesium hydroxy-silicate, and amorphous silica as precipitates. 

Earth resistance depends on the type of soil, its mineral composition, moisture content, and temperature. Table 5.2 provides the resistivity of various types of soils Table 5.3, the effect of moisture on soil resistivity and Table 5.4, the effect of temperature on soil resistivity. The information contained in the tables is used to illustrate the effect of various natural factors on soil resistivity. Table 5.5 shows the changes in earth resistance by using multiple ground rods. Note that, to realize the full benefits of multiple rods, the rods should be spaced an adequate distance apart. 

There is a need to resume studies of soil saccharides and peptides. These can compose as much as 30-40% (when account is taken of the compositions of humin materials). Much is known about how polysaccharides of known structures interact with soil colloids, but it has not been possible as yet to know in sufficient detail the structures of the polysaccharides that persist in the soil. Hence we do not know the mechanisms of their binding to soil mineral colloids. The same applies for the peptide materials, though it is clear that polysaccharides and peptides have important roles in soil structure formation and stabilization. 

Figure 2.2. Changes in particle size, C/N ratio, and chemical composition of organic matter in mineral soil with increasing extent of oxidative decomposition. Reprinted from Baldock, J. A., and Skjemstad, J. O. (2000). The role of soil mineral matrix in protecting natural organic materials against biological attack. Org. Geochem. 31, 697-710, with permission from Elsevier.

The temperature dependent algorithms used to predict natural sulfur emissions do not account for all of the variation in observed emissions. Other important environmental parameters may include, but are not limited to, tidal flushing, availability of sulfur, soil moisture, soil pH, mineral composition, ground cover, and solar radiation. A more accurate estimation of the national sulfur inventory will require a better understanding of the factors which influence natural emissions and the means to extrapolate any additional parameters which are determined to be important. 

Scanning electron microscopes (SEMs) and transmission electron microscopes (TEMs) are also frequently used to examine the morphology and chemical composition (via energy dispersive spectroscopy) of particles more than 100,000 times their original size, making them very useful. Soil minerals, fossils, and pollen spores that occur in soils and can be described and analyzed in detail by SEMs and TEMs and are very useful indicators when studying soil samples. All these techniques in combination achieve reliable, definite, and accurate results and provide additional information about the chemical and physical properties of the suspected material. 

A reaction that involves chemical species in more than one phase is termed heterogeneous.1 An example is the composite reaction describing the reductive dissolution of the common soil mineral hematite (a-Fe ) in the presence of visible light by oxalic acid (H2C204), a ubiquitous plant litter degradation product ... 

Garg, V.K., Singh, P.K. and Katiyar, R.S. (2004) Yield, mineral composition and quality of coriander (Coriandrum sativum) and fennel (Foeniculum vulgare) grown in sodic soil. Indian journal of Agricultural Sciences 74(4), 221-223. 

However, the excess of phosphates and PolyPs in soil due to technogenic pollution and the use of fertilizers has a great influence on the transformation of mineral and organic compounds in soil, the composition of soil microbial communities, and finally agriculture productivity (Kudeyarova, 1993). 

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