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Occupational exposure limits are the maximum allowable concentrations of hazardous elements in the air. They are defined by scientific laboratories in order to control the level of pollution in different areas. Among the main atmosphere pollutants are large-scale industry, domestic boilers and transport. The portion of each of these pollutants is different from place to place, but industrial companies are considered to be the worst pollutants. The major sources of artificial aerosol pollution of the atmosphere are thermal power plants that burn a large amount of coal with high ash content, concentrating mills, metallurgical, cement, magnesite and soot plants. |
Methods of removal of oil contamination
The problem of self-purification of sea waters from oil contamination has been studied insufficiently. In this complex process the biological factor has the key position. This factor leads to transformation of the oil contamination into simple compounds (carbon dioxides and others) as a result of activity of oil oxidizing organisms, as well as accumulation of the new organic substance as a result of growth of the biomass of the microorganisms.
However, the natural processes of self-purification are not able to process the large amounts of oil that are systematically spilled into the water as a result of crashes and accidents. New methods of removal of oil pollution have been developing lately. Let's take a closer look at them. Firs of all, oil products can be burned, but only right after the spill as oil loses its light fractions for the first two hours and forms a thin layer. The cooling effect of the water under such a layer leads to the extinction of fire. Oil and oil products can also be collected from the water surface in three ways: simple excochleation from small boats; limitation of the oil film with the help of booms with its further concentration by decreasing the area and approaching the booms; by complex automated complexes. Collection of oil can also be done by covering the oil film with an adsorbing agent. Another promising way of collecting oil is covering it with a layer of powder or a granulated substance that mixes with oil and drowns it. However, numerous experiments have shown that the drowned mass can become mobile in a few months leading to the possibility of its lifting when the water is rough.
