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PHOTOCHEMICAL smog (Los Angeles type smog)
Transcript of PHOTOCHEMICAL smog (Los Angeles type smog)
(Los Angeles TYPE SMOG) Smog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Modern smog comes from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. Smog is also caused by large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. In the 1950s a new type of smog, known as photochemical smog, was first described.
This forms when sunlight hits various pollutants in the air and forms a mix of inimical chemicals that can be very dangerous. A photochemical smog is the chemical reaction of sunlight, nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the atmosphere, which leaves airborne particles (called particulate matter) and ground-level ozone.
Nitrogen oxides are released by nitrogen and oxygen in the air reacting together under high temperature such as in the exhaust of fossil fuel-burning engines in cars, trucks, coal power plants, and industrial manufacturing factories. VOCs are released from man-made sources such as gasoline (petrol), paints, solvents, pesticides, and biogenic sources, such as pine and citrus tree emissions.
This noxious mixture of air pollutants can include the following:
•Nitrogen oxides, such as nitrogen dioxide
•Peroxyacyl nitrates (PAN)
•Volatile organic compounds (VOCs)
All of these chemicals are usually highly reactive and oxidizing. Photochemical smog is therefore considered to be a problem of modern industrialization. It is present in all modern cities, but it is more common in cities with sunny, warm, dry climates and a large number of motor vehicles. Because it travels with the wind, it can affect sparsely populated areas as well.