Soil distribution, lead compounds

The effectiveness of the BSWS as a volume reduction unit depends largely on the solubility of the lead compounds in the washing medium, the efficiency of density separation for removing discrete lead particles, and the particle size distribution in the feed soil. 

Oxides and hydroxides of Fe and Mn are ordinary components of black soils, but their impact on the behaviour of microelements is very important. These compounds can absorb microelements, because they form membranes in soil (Kabata-Pendias et al., 2003). High content of Fe and Mn oxides and hydroxides in soil may lead to significant changes in the geochemical balance. However, the environmental impacts are not equally distributed over the territory. It is a well-known fact, that impacts in certain industrial areas are higher than in others. Table 3 shows the concentrations of 15 elements in urban soils. 

The United States Public Health Services drinking water standards specify a 50 mg/1 maximum for lead, EPA [73] has shown that this limit is only infrequently exceeded in larger United States cities. The presence of lead in drinking water may result from the use of lead materials in the water distribution system. Naturally occurring lead in rocks and soils may be an important source of contamination in isolated instances but lead from industrial wastes represent a local and not a widespread problem. The disposition of lead compounds from gasoline is a major source of lead in water systems [73]. 

Sulphates, silicates, carbonates, colloids and certain organic compounds act as inhibitors if evenly distributed, and sodium silicate has been used as such in certain media. Nitrates tend to promote corrosion, especially in acid soil waters, due to cathodic de-polarisation and to the formation of soluble nitrates. Alkaline soils can cause serious corrosion with the formation of alkali plumbites which decompose to give (red) lead monoxide. Organic acids and carbon dioxide from rotting vegetable matter or manure also have a strong corrosive action. This is probably the explanation of phenol corrosion , which is not caused by phenol, but thought to be caused by decomposition of jute or hessian in applied protective layers. ... 

Unlike the situation with soil samples, it should be noted that the uranium content in sediments depends on many factors such as the organic matter content, the grain composition, and size distribution, as well as their chemical affinity to uranium. In some cases, the uranium compounds coat the grain surface and may be washed away, leading to an erroneous estimate of the uranium content... 

Abstract The soil as an adsorbent has various active sites leading to rather complicated adsorption mechanisms with environmental pollutants, like pesticides. According to earlier results the chloroacetani-lide type herbicides as solutes resulted in two-step isotherms on soils and quartz. This phenomenon has not been observed yet concerning trace compounds in the environment. In this case the so-called distributed reactivity model is used, suggesting that the total sorption is given as the sum of the local adsorption isotherms. The adsorption of isoproturon (urea-type herbicide) and prometryn (5-triazine type herbicide) was studied on quartz at different pH values. 

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