Alkalinity, weathering

Marah is an area of desert located near the Red Sea on the Sinai Peninsula. The desert water is bitter due to high alkalinity. Weathering of wood on the desert by the sun causes the alcohol groups of cellulose and hemicellulose to be oxidized to carboxyl groups. By throwing a piece of weathered wood into the alkaline water, an acid-base reaction takes place in which the alkalinity of the water is reduced. Thereby, the water becomes sweet. 

Fig. 2. Flow sheet for the acid circuit processing and recovery of mica from weathered granodiorite ore. An alkaline—cationic circuit may be used by inserting a second conditioner containing lignin sulfonate, adjusting the pH to 8.0, and adding NaOH and DRL (distilled tall oil) fatty acid to the first...

In all cases, water and carbonic acid, the latter of which is the source of protons, are the main reactants. The net result of the reaction is the release of cations (Ca " ), Mg ", K", Na" ) and the production of alkalinity via HCO. When ferrous iron is present in the lattice, as in biotite, oxygen consumption may become an important factor affecting the weathering mechanism and the rate of dissolution. 

Vinyl neodecanoate [26544-09-2] is prepared by the reaction of neodecanoic acid and acetjiene in the presence of a catalyst such as zinc neodecanoate. Physical properties of the commercially available material, VeoVa 10 from Shell, are given in Table 4. The material is a mobile Hquid with a typical mild ester odor used in a number of areas, primarily in coatings, but also in constmction, adhesives, cosmetics, and a number of misceUaneous areas. Copolymerization of vinyl neodecanoate with vinyl acetate gives coating materials with exceUent performance on alkaline substrates and in exterior weathering conditions. 

There are different concrete replacement systems available for renovating reinforced concrete structures. They range from sprayed concrete without polymer additions to systems containing conducting polymers (PCC-mortar). Since with the latter alkalinity is lower, more rapid carbonization occurs on weathering [59] and the increased electrical resistivity has to be taken into account, so that with cathodic protection only sprayed concrete should be used as a repair mortar. 

Titanium dioxide used for adhesive applications should contain an inorganic coating to control polarity, improve its ease of dispersion, and improve its weather resistance. The inorganic coating (zirconium dioxide, silica, alumina) is applied in the aqueous sluny by precipitation of one or more hydrated metal oxides and by neutralization of acidic and alkaline compounds. 

Gays are an essential component of soils, to which we owe our survival, and they are also the raw materials for some of mankind s most ancient and essential artefacts pottery, bricks, tiles, etc. Clays are formed by the weathering and decomposition of igneous rocks and occur typically as very fine panicles e.g. kaolinite is formed as hexagonal plates of edge. 1-3 p m by the weathering of alkaline feldspar... 

Soil reaction (pH) The relationship between the environment and development of acid or alkaline conditions in soil has been discussed with respect to formation of soils from the parent rock materials. Soil acidity comes in part by the formation of carbonic acid from carbon dioxide of biological origin and water. Other acidic development may come from acid residues of weathering, shifts in mineral types, loss of alkaline or basic earth elements by leaching, formation of organic or inorganic acids by microbial activity, plant root secretions, and man-made pollution of the soil, especially by industrial wastes. 

The influence that variations of temperature and levels of atmospheric CO2 and O2 have on chemical weathering are more subtle. Temperature appears to have a direct effect on weathering rate (White and Blum, 1995). The silica concentration of rivers (Meybeck, 1979, 1987) and the alkalinity of ground waters in carbonate terrains (Harmon et al., 1975) are both positively correlated with temperature variations. It is not clear, however, whether temperature-related variations in weathering rates are largely due to variations in vegetational activity that parallel temperature variations. 

Coarse-sized particles dominate the particle size distribution of arid soils. Some soils are also quite gravelly. The subsurface horizons commonly exhibit accumulation zones of carbonates, gypsum and more soluble salts. Many arid zone soils are shallow and gravelly, some are alkaline. Their structure is weak. From most soils, clay accumulation horizons (argillic horizons) are absent, or are only weakly developed, and so are minerals that indicate an advanced degree of weathering. 

Class 5 (the least sensitive) soil include Kashtanozem, Brown soil and Sierozem soil zones in the Plateau of Inner Mongolia and the Loess Plateau, Desert soil zones in He-xi-zou-lang and the Talimu River Basin, Subalpine Steppe soil, Alpine Steppe soil and Alpine Desert soil in the Plateau of Tibet. These kinds of soils, belonging to the soil class of Xerosol or Alpine soil, consist of easy weathering minerals such as carbonate. They show alkaline reactions, with weak leaching and sparse vegetation. Those kinds of soils are insensitive to acid deposition. 

Sorption depends on Sorption Sites. The sorption of alkaline and earth-alkaline cations on expandable three layer clays - smectites (montmorillonites) - can usually be interpreted as stoichiometric exchange of interlayer ions. Heavy metals however are sorbed by surface complex formation to the OH-functional groups of the outer surface (the so-called broken bonds). The non-swellable three-layer silicates, micas such as illite, can usually not exchange their interlayer ions but the outside of these minerals and the weathered crystal edges ("frayed edges") participate in ion exchange reactions. 

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