الخميس، 29 سبتمبر 2011

pollution

      

    The phenomenon of pollution of the environment has increased in many countries of the world to the extent that it threatens the continuity and survival of the human race. The main sources of pollution are : remains of combustion, refuse of industry, human wastes, pesticides, fertilizers, and radioactive substances. All of these give off products into biosphere and so living organisms are affected in one way or another. In addition, sound pollution caused by factories and huge aircrafts, as well as noise in the cities and bad habits of some people, all cause harm to man.
    Traces of pollutants may remain in the biosphere for a long time.
    They may also be transmitted to other places which means that their harm is not restricted to their sources, but may extend to other places.
    Pollution of the environment includes the change in its characteristics due to both quantitative and qualitative changes affecting that environment. Polluted air , for example, differs in its properties from pure air. These changes may be due to human interference. 
    Pollution can be defined as the presence of any substance or energy in the wrong place, the wrong time or the wrong quantity.
    Water is considered as pollutant if it is added to the soil in amounts that displace the soil air. Salts, accumulated  in the cultivable soil due to an inefficient drainage system, are also considered as pollutants.
    Petroleum, may become a pollutant  if it percolates to seawater. Sound, when it increases in intensity above a certain level is considered as pollutant. These may be annoying and lead to deafness.

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