Smog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulphur dioxide.
In the 1950s a new type of smog, known as photochemical smog, was first described. This is a noxious mixture of air pollutants including the following:
* nitrogen oxides, such as nitrogen dioxide
* tropospheric ozone
* volatile organic compounds (VOCs)
* peroxyacyl nitrates (PAN)
* aldehydes (R'O)
All of these chemicals are usually highly reactive and oxidizing. Due to this fact, photochemical smog is considered to be a problem of modern industrialization.
Photochemical smog is a concern in most major urban centres but, because it travels with the wind, it can affect sparsely populated areas as well. Smog is caused by a reaction between sunlight and emissions mainly from human activity. Photochemical smog is the chemical reaction of sunlight, nitrogen oxides (NOx) and volatile organic compounds (VOC's) in the atmosphere, which leaves airborne particles (called particulate matter) and ground-level ozone. Nitrogen oxides are released in the exhaust of fossil fuel-burning engines in cars, trucks, coal power plants, and industrial manufacturing factories. VOC's are vapors released from antroprogenric sources (man made) like gasoline, paints, solvents, pesticides, and biogenic sources, such as pine and citrus tree emissions.
2007-03-14 05:12:23
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answer #1
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answered by hello 6
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