Soil Alkalinity

Alkaline soils (pH 7) contain solid phase carbonate, and bicarbonate is the dominant anion in solution. Calcium and magnesium carbonates 

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LAS Sludge-amended soil Alkaline methanol HPLC-UV 17-155 [20]... 

LAS Soil Alkaline methanol Complexation/extraction Photometer [29]... 

Powdered limestone is most often used to neutralise acid soil (Figure 13.4) because it is cheaper than any form of lime (calcium oxide), which has to be produced by heating limestone (see p. 209), and because it is slow acting and an excess does not make the soil alkaline. The reaction of limestone with acidic soil can be shown by the following ionic equation. 

Wetlands of humid climatic zones often emit H2S, as is evident from the rotten-egg odor of marshes and swamps. As long as the dominant exchangeable base cations are Ca " and Mg ", which is the case in most freshwater wetlands, H2S formation should not cause the soils to become strongly alkaline. In these nonsodic soils, alkalinity generated by reduction forms precipitates of Ca (and Mg) carbonates. The low solubility of these carbonates prevents the pH from rising much above 8. In sodic soils, however, reaction 7.64 causes alkalinity to build up in the form of soluble Na carbonates (see Chapter 8, Section 8.1). 

Cobalt toxicity is occasionally found in high-Co soils formed from serpentinite and other ultrabasic rocks. Deficiency is most likely in coarse-textured, acid-leached soils alkaline or calcareous soils and humus-rich soils. Extractability by strong acids can range from very little (< 1%) to a large fraction (>30%) of the total Co, depending on the forms of Co in the soil. 

Cows fed with fodder from saline soils (alkaline soils) in Hungary produced urine containing 636 mg Na L whereas the... 

The presence of large amounts of basic salts can considerable shift the soil reaction into the alkaline region. Soil alkalinity is mostly caused by exchangeable sodium cations in soil colloids. 

Adsorption of Mo to hydrous Fe and A1 oxides is pH-dependent (Reisenauer, Tabikh, and Stout, 1962), and the rate of adsorption is highest at acidic pH. It decreases with increases in pH from 4.45 to 7.5. Compared with acid soils, alkaline soils are high in soluble or available Mo (Davis, 1956). As in any other soil, in alkaline soil the availability of Mo is also influenced by several other factors. The relative Mo content of the parent rock, the process of soil evolution, and the physicochemical attributes of the soil (pH, calcareousness, organic-matter content, cation-exchange capacity, texture, moisture, relative concentrations of other mineral elements) all influence the availability of Mo. 

Faulkner, Hopkinson, and Cundy, 2005). Because of the adverse effect of OH on soil remediation, due to the immobilization of many metal ions by precipitation in alkalinized soils, and the reduced efficiency of electrokinetic remediation when sacrificial iron-rich electrodes are employed (e.g. Leinz, Hoover, and Meier, 1998), noncorrosive electrodes and techniques to minimize soil alkalinization are generally employed for electrokinetic remediation (e.g. Rohrs, Ludwig, and Rahner, 2002 Virkutyte, Sillanpaa, and Latostenmaa, 2002). However, low adsorption of Cr(VI) in soils occurs in alkaline conditions, whereas high adsorption of Cr(VI) is favored in acidic conditions (Reddy et al, 1997). Furthermore, the reduction of Cr(VI) to Cr(III) by the delivery of iron (Fe°, Fe " ) is fairly well documented (Rai, Sass, and Moore, 1987 Eary and Rai, 1991 Haran et aL, 1995 Powell et aL, 1995 Pamukcu, Weeks, and Wittle, 1997 Batchelor et al., 1998 Reddy et /., 2003). Accordingly,under an applied direct current (DC) electric field, stabilization of Cr(VI)-contaminated soils may potentially be achieved where oxidative dissolution of iron-rich anodic electrodes provides Fe(j,q) to react with the anode-bound migration of Cr(VI). Hence, the use of iron-rich sacrificial electrodes and soil alkalinization may find application in the electrokinetic stabilization of Cr(VI)-contaminated soils. This concept is explained in this chapter based on the results of laboratory stabilization experiments on three Cr(VI)-impacted soils taken from three sites within the UK. 

Aid in emulsification and removal of greasy soils. Alkalinity plays a role in removing acidic, fatty, and oily soils. 

An alternative approach to the problem of characterising soil P has been to use P-nuclear magnetic resonance (nmr) to obtain both qualitative and quantitative estimates of the various forms of P in soil alkaline extracts. 

Other compounds used as nitrogen fertilizers include sodium nitrate (obtained largely from Chilean deposits, see Section 17.2), calcium nitrate, potassium nitrate, and ammonium phosphates. Ammonium sulfate, a by-product of coke ovens, used to be widely apphed as fertilizer. The alkali metal nitrates tend to make soil alkaline, whereas ammonium sulfate leaves an acidic residue. 

Correlating these results with corresponding pH data it can be affirmed that keeping a shorter difference in pH wells, as it hapvpens with bare RVC electrodes, it favors a soil alkaline condition which, even though produces a slower liquid movement, so far this is good enough for phenanthrene removal since it provides a higher residence time. 

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