Soils soluble salts

Fogliata, F. A., Aso, P. J., The Effects of Soil Soluble Salts on Sucrose Yield of Sugarcane, Proc. 12th Cong. ISSCT, Puerto Rico (1967) 682-694. 

Exchangeable ions are those ions replaced by neutral salt solutions flowing through soils. Soluble salts are removed by water alone. Salt solutions also exchange anions... 

Agriculture ndNutrition. Cobalt salts, soluble in water or stomach acid, are added to soils and animal feeds to correct cobalt deficiencies. In soil apphcation the cobalt is readily assimilated into the plants and subsequendy made available to the animals (56). Plants do not seem to be affected by the cobalt uptake from the soil. Cobalt salts are also added to salt blocks or pellets (see Feeds and feed additives). 

The oxidation products are almost insoluble and lead to the formation of protective films. They promote aeration cells if these products do not cover the metal surface uniformly. Ions of soluble salts play an important role in these cells. In the schematic diagram in Fig. 4-1 it is assumed that from the start the two corrosion partial reactions are taking place at two entirely separate locations. This process must quickly come to a complete standstill if soluble salts are absent, because otherwise the ions produced according to Eqs. (2-21) and (2-17) would form a local space charge. Corrosion in salt-free water is only possible if the two partial reactions are not spatially separated, but occur at the same place with equivalent current densities. The reaction products then react according to Eq. (4-2) and in the subsequent reactions (4-3a) and (4-3b) to form protective films. Similar behavior occurs in salt-free sandy soils. 

Soluble salts of the soil Water in the soil should most properly be considered as the solvent for salts of the soil the result being the soil solution. In temperate climates and moderate rainfall areas, the soil solution is relatively dilute, with total dissolved salts ranging from 80 to 1 500 p.p.m. Regions of extensive rainfall show lower concentrations of soluble salts as the result of leaching action. Conversely, soils in arid regions are usually quite high in salts as these salts are carried to the surface layers of the soil by water movement due to surface evaporation. 

The modern procedure to minimise corrosion losses on underground structures is to use protective coatings between the metal and soil and to apply cathodic protection to the metal structure (see Chapter 11). In this situation, soils influence the operation in a somewhat different manner than is the case with unprotected bare metal. A soil with moderately high salts content (low resistivity) is desirable for the location of the anodes. If the impressed potential is from a sacrificial metal, the effective potential and current available will depend upon soil properties such as pH, soluble salts and moisture present. When rectifiers are used as the source of the cathodic potential, soils of low electrical resistance are desirable for the location of the anode beds. A protective coating free from holidays and of uniformly high insulation value causes the electrical conducting properties of the soil to become of less significance in relation to corrosion rates (Section 15.8). 

The factors influencing the corrosion of metals in soil are more numerous than those prevailing in air or water, and the electrochemical effects are more pronounced. Moreover, soils vary widely in their composition and behaviour even over very short distances. It is difficult therefore to obtain reliable data. It is evident, however, that zinc has considerable resistance to corrosion when buried, and the greatest attack is caused by soils which are acid or contain large amounts of soluble salts. 

In tests carried out by the National Bureau of Standards in the USA specimens of copper alloys, lead, zinc and zinc alloys were buried at a number of different sites for periods varying from 11 to 14 years. The soils tested covered a pH range from 2-6 to 9-4 and resistivities ranged from 62 to 17 800 fi cm. The weight losses and maximum depths of pitting were recorded, and the results indicated that the most severe corrosion occurred in soils of poor aeration having high acid and soluble-salt contents. 

Buprofezin and its metabolites, p-OH-buprofezin and BF12, are hydrophobic under neutral conditions. Having the organic base part in their chemical structure, these compounds form water-soluble salts under strongly acidic conditions. The change in solubilities of these compounds influences the cleanup procedure. Four different residue analytical methods have been developed to measure buprofezin and its metabolites in plants (rice, citrus and tomato cucumber, pepper, tomato, squash and eggplant), soil and water ... 

Pore water extraction and determination of the soluble salt content of soils by refractometer... 

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. 

All soils contain soluble salts, but their concentration is low. The salt content of most arid soils is, however, much higher. Salts in desert soils are usually derived from three main sources (1) deposition of wind-blown salt spray or dust (2) in situ weathering of salt-containing rocks or sediments, and (3) upward movement with the capillary flow from a shallow salty groundwater. Along the coastline, some salinization may occur through intrusion and flooding by seawater. 

For understanding these tendencies, we will consider the values of the biogeo-chemical coefficient of aqueous migration. This coefficient Cw is the ratio between the content of an element in the sum of water-soluble salts and in geological rocks. The values of Cw for certain chemical species are smaller in Arid ecosystems than those in Forest ecosystems. We can suggest two explanations. First, soils of Forest ecosystems are enriched in water-soluble metal-organic complexes (see Chapter 7). Second, most chemical species are trapped in the transpiration barrier of upper soil layers of Arid ecosystems. 

Different conditions are typical for Dry Tropical Wood, Dry Savanna and Dry Woody Shrub ecosystems in areas with precipitation rates of 400-600 mm and a prolonged dry season. The microbial activity is suppressed during a dry season. The soils of these ecosystems have no even periodic leaching, the formation by transpiration of a biogeochemical barrier in the upper soil layer favors the alkaline reaction and accumulation of soluble salts. This decreases also the intensity of exposure to different pollutants for living organisms. 

King FH. Investigations in Soil Management Being Three of Six Papers Influence of Soil Management upon the Water-Soluble Salts in Soil and the Yield of Crops. Madison, WI Author 1904. 

Under low-rainfall and desert conditions, the lack of rainfall results in very different soil conditions. Figure 2.6 shows the profile description of an Aridisol (an arid, desert, region soil) (see Section 2.4 for the explanation of the naming system). All lower horizons contain a high content of sodium ions and most also contain other soluble salts of various kinds. 

In low-rainfall regions, salts are not readily washed out of soils and may even build up on the soil surface. This happens when rain dissolves salts in the soil surface and leaches them a little way into the soil. Subsequent evaporation of water from the soil surface causes water and dissolved salts to move to and be deposited on the soil surface. No salts or only the most soluble salts are leached out of the soil, in low-rainfall regions, and the pH is typically basic. 

Water that can easily be removed from soil is called gravitational water. Some of the water retained against the pull of gravity is called plant available water. Which of these two would be expected to have more soluble salts Why ... 

Janzen HH. Soluble salts. In Carter MR (ed.), Soil Sampling and Methods of Analysis. Ann Arbor, MI Lewis Publishers 1993, pp. 161-166. 

SESR is applicable for soils contaminated with petroleum hydrocarbons, polychlorinated biphenyls (RGBs), and pentachlorophenol (PCP). The technology has been demonstrated to fix heavy metals and remove hydrocarbon contaminants simultaneously. After treatment, soluble salts can be leached from the dried, agglomerated soil. 

Based on a study comparing N-Viro soil physical properties with those of mineral soils, the physical characteristics of N-Viro soils suggest that chemical characteristics (such as high initial pH, acid neutralizing capacity, and high soluble salt content), rather than physical attributes, are likely to limit the use of these materials as soil substitutes. 

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