Photochemical smog

A form of smog that characterizes polluted atmospheres where high concentrations of nitrogen oxides and volatile organic compounds--often from gas-driven automobilesmixed with sunlight promote a series of photochemical reactions that lead to the formation of ozone and a range of oxidized and nitrated organic compounds. The smog turns brownish in color and lowers visibility towards the middle of the day as sunlight becomes intense. The smog also causes eye irritation and a range of less distinct short- and long-term health effects. Photochemical smog, though typified by the atmosphere of the Los Angeles Basin , is increasingly found in cities all over the world where volatile fuels are used.

photochemical smog A hazy condition of the atmosphere caused by the reaction of hydrocarbons with molecules of nitrogen oxide in sunlight, which produces complex organic molecules of peroxyacetyl nitrates (PAN). In humid conditions these molecules produce smog. Such phenomena are common in large urban areas (e.g. the Los Angeles basin and Athens) where there are stable atmospheric conditions and a high level of hydrocarbon input from incomplete combustion in car engines. Natural photochemical reactions occur in the high atmosphere with the absorption of radiation by oxygen to produce ozone. See also ozone layer.

photochemical smog Hazy condition of the atmosphere due to the reaction of hydrocarbons with molecules of nitrogen oxide in sunlight which produces complex organic molecules of peroxyacetyl nitrates (PAN). In humid conditions these molecules produce smog. Such phenomena are common in large urban areas (e.g. the Los Angeles Basin and Athens) where there are stable atmospheric conditions and a high level of hydrocarbon input from incomplete combustion in car engines. Natural photochemical reactions occur in the high atmosphere with the absorption of radiation by oxygen to produce ozone. See also OZONE LAYER.

photochemical smog A noxious smog produced by the reaction of nitrogen oxides with hydrocarbons in the presence of ultraviolet light from the sun. The reaction is very complex and one of the products is ozone. See also air pollution.