Primary minerals soils

Standard cations used for measuring cation exchange capacity are Na+, NHJ, and Ba2+. NH is often used but it may form inner-sphere complexes with 2 1 layer clays and may substitute for cations in easily weathered primary soil minerals. In other words, one has to adhere to detailed operational laboratory procedures these need to be known to interpret the data and it is difficult to come up with an operationally determined "ion exchange capacity" that can readily be conceptualized unequivocally. 

Table 3 Structures of common primary soil minerals...

Mineralogical investigations of soils may be undertaken with a number of different objectives in view. Analysis of primary minerals can show whether a soil is sedentary or transported, and if the latter, it can indicate the rock formations from which the parent material was derived. The nature and the extent of pedological weathering, and hence the age, of soils can be deduced from the secondary minerals produced as well as from the primary minerals that have survived. It is mainly in the study of the primary soil minerals that heavy mineral analysis is of importance. 

The inorganic component of soil is dominated by four elements O, Si, Al, and Fe (Jackson, 1964). Together with Mg, Ca, Na, and K they constitute 99% of the soil mineral matter (see Table 8-2). Minerals in soil are divided into primary and secondary minerals. Primary minerals, which occur in igneous, metamorphic, and sedimentary rocks, are inherited by soil... 

Bloesch, P.M. Bell, L.C. Hughes, J.D. (1987) Adsorption and desorption of boron by goethite. Aust. J. Soil Res. 25 377-390 Blomiley, E.R. Seebauer, E.G. (1999) New approach to manipulating and characterising powdered photo adsorbents. NO on Cl treated Ee20j. Langmuir 15 5970-5976 Bloom, P.R. Nater, E.A. (1991) Kinetics of dissolution of oxide and primary silicate minerals. In Sparks, D.L. Suarez, D.L. (eds.) Rates of soil chemical processes. Soil Sci. 

Little is known concerning the chemistry of nickel in the atmosphere. The probable species present in the atmosphere include soil minerals, nickel oxide, and nickel sulfate (Schmidt and Andren 1980). In aerobic waters at environmental pHs, the predominant form of nickel is the hexahydrate Ni(H20)g ion (Richter and Theis 1980). Complexes with naturally occurring anions, such as OH, SO/, and Cf, are formed to a small degree. Complexes with hydroxyl radicals are more stable than those with sulfate, which in turn are more stable than those with chloride. Ni(OH)2° becomes the dominant species above pH 9.5. In anaerobic systems, nickel sulfide forms if sulfur is present, and this limits the solubility of nickel. In soil, the most important sinks for nickel, other than soil minerals, are amorphous oxides of iron and manganese. The mobility of nickel in soil is site specific pH is the primary factor affecting leachability. Mobility increases at low pH. At one well-studied site, the sulfate concentration and the... 

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. 

We have chosen to study the genesis of the spring waters of the Sierra Nevada because of the availability of a careful set of analyses of the waters plus determinations of the primary igneous rock minerals and of the soil minerals derived from them (3). As we will demonstrate, the Sierra system emerges as one in which a few primary igneous rock... 

The primary soil components responsible for pesticide sorption are clay minerals and, especially, humic materials. Pesticides can be divided into cationic, basic, acidic, and nonionic classes (Saltzman and Yaron, 1986). 

A cold early climate and a thin CO2 atmosphere are consistent with the ubiquity of primary igneous minerals and the apparent absence of secondary minerals and copious carbonates on the surface. Aqueous eruptions introduced soluble chloride and sulfate salts into Martian soils, leaving clays and carbonates within the crust. If the Martian crust hosts a deep biosphere, aqueous eruptions could bring organisms or their chemical signature to the surface. The biotic component of any recent eruptions may be preserved in transient ice in cold traps on the surface. 

Ferrous corrosion products do not have a biocidal effect however, iron corrosion tends to form a much more extensive and encapsulating matrix. This corrosion matrix, which is principally formed of iron oxides, hydroxides, and soil minerals, will encapsulate any organic materials. This usually takes the form of a negative cast (Keepax 1975), provided that the primary layer of corrosion product has been laid down prior to any extensive degradation of the organic material, then fine surface detail will be preserved in the corrosion cast. Because the iron corrosion will not inhibit degradation... 

The inorganic minerals of soil are classified into (a) primary minerals and (b) secondary minerals (Table 3.3). Primary minerals are minerals with the chemical composition and structure obtained during the crystallization process of molten lava, whereas secondary minerals are those that have been altered from the original structure and chemical composition by weathering, a process referred to as the geomorphic cycle (Fig. 3.2). Generally, the size of soil mineral particles varies from clay-sized colloids (< 2 pm) to gravel (< 2 mm) and rocks. 

Hydrous Oxides. This term is generally taken to include the oxides, hydroxides, and oxyhydroxides of aluminium, iron and manganese, which form in soil when these elements are released from primary minerals by weathering. They exist mainly as small particles in the claysized fraction of a soil (<2 pm), and also as coatings on other soil minerals or as components of larger aggregates. 

Mass-balance studies are widely considered to be the most reliable means of making quanta-tive determinations of elemental transfer rates in natural systems. Garrels (1967) and Garrels and Mackenzie (1967) pioneered the use of mass-balance calculations for mineral weathering in their classic study of Sierra Nevada springwaters. These waters were chosen because a careful set of water analyses and associated primary igneous rock minerals and the soil mineral alteration products were known. Since the actual compositions of the minerals were not known, Garrels and Mackenzie used the theoretical formulas for the minerals. 

Figure 12 Surface area parameters (a) surface area of primary silicate minerals contained in soils of the Merced chronosequence (after White et al., 1996). (b) Surface roughness of sihcate minerals as functions of the duration of experimental and natural weathering (source White and Brantley, 2003).

Alexandre et al. (1997) found that the biogenic sihca input into the biogeochemical silica cycle from the dissolution of phytoliths is twice as large as silica input from primary silicate mineral weathering in the tropical Congo rainforest. Biogenic (opaline) silica dissolves faster than sihcate minerals. While most of the phytoliths dissolve rapidly with a mean residence time of 6 months (Alexandre et al., 1994), and the sihca is recycled by the forest, a small part (7.5%) does not dissolve and is preserved in the soil. 

Source After H. Sverdrup and P. Warfvinge. Weathering of primary silicate minerals in the natural soil environment in relation to a chemical weathering model. Water, Air and Soil Pollution 38 387-408. 1988 by Kluwer Academic Publ. Used by permission. 

The availability of reliable measurements or estimates of water solubility, octanol-water partition coefficient, bioconcentration factor, rate constants and the like allows one to make qualitative judgements or, through the use of mathematical simulation models such as EPA s EXAMS (19), quantitative calculations of environmental distribution and persistence. In the qualitative use, Swann and coworkers (20) classified chemical mobility in soil based upon reversed-phase HPLC retention data which in turn is related to S. The approximate water solubility equivalents in this first-estimate classification, with chemical examples, are in Table II. This classification holds for chemicals whose primary adsorption in soil is to organic matter, and excludes those chemicals (such as paraquat) which bind ionically to the soil mineral fraction. A recent tabulation of pesticides found in groundwater had 11 entries, 8 of which represented compounds with water solubilities in excess of 200 ppm with the remaining three falling in the range of 3.5 to 52 ppm (21). 

Layer silicates, sheet-like phyllosilicates such as the familiar micas, are in primary rocks and in soils. The soil minerals are often called clay minerals. Since other components can also be in the clay fraction, layer silicates is a mom accurate term. A typical layer silicate is a combination of a layer of Al-, Mg-, or Fe(II)-0 octahedra plus one or two layers of Si-0 tetrahedra. The tetrahedral and octahedral sheets bond together by sharing oxygens at the corners of the tetrahedra and octahedra. Layer silicate minerals are differentiated by (1) the number and sequence of tetrahedral and octahedral sheets, (2) the layer charge per unit cell, (3) the type of interlayer bond... 

Table 7.6. Common primary (residual) minerals present in soil environments in order of increasing stability3...

Fig. 15.4. Simulated plant production (a), soil carbon (0-50 cm depth) and soil respiration (b), and nitrogen and phosphorus soil mineralization (c) for Hawaii humid tropical forest systems during 4.1 million years of soil development. Observed data are plotted on the graphs, and observed net primary production is assumed to be equal to 0.7 times annual soil respiration.

Soil mineral matter consists of 50-90% of the dry weight of marsh soils (Nyman et al., 1990). Storm passage including hurricanes is a primary mechanism that delivers mineral sediments to Louisiana marshes (Reed, 1989 Roberts et al., 1989 Turner et al., 2006). Increased water levels and wave action in bays and lakes prior to frontal passage transport sediments from water bottoms to... 

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