Automobile emissions ozone pollution from

Although the naturally occurring concentration of ozone at the earth s surface is low, the distribution has been altered by the emission of pollutants, primarily by automobiles but also from industrial sources which lead to the formation of ozone. The strategy for controlling ambient ozone concentrations arising from automobile exhaust emissions is based on the control of hydrocarbons, CO, and NO via catalytic converters. As a result, peak ozone levels in Los Angeles, for instance, have decreased from 0.58 ppm in 1970 to 0.33 ppm in 1990, despite a 66% increase in the number of vehicles. 

The most widespread and persistent urban pollution problem is ozone. The causes of this and the lesser problem of CO and PMjq pollution in our urban areas are largely due to the diversity and number of urban air pollution sources. One component of urban smog, hydrocarbons, comes from automobile emissions, petroleum refineries, chemical plants, dry cleaners, gasoline stations, house painting, and printing shops. Another key component, nitrogen oxides, comes from the combustion of fuel for transportation, utilities, and industries. 

Ozone is formed from automobile emissions and is an urban air pollutant, but it is also formed naturally in the stratosphere. At altitudes of 20 to 30 kilometers, high-energy ultraviolet (UV) radiation breaks diatomic oxygen down to atomic oxygen, which then reacts with additional Oz to form ozone ... 

Many gas-fired compressors that pump natural gas through millions of miles of pipelines are also equipped with exhaust catalysts to clean emissions at moderate conditions. Even fast-food restaurants are being equipped with catalysts to eliminate odors from the cooking process. The most widely used treatment of exhaust pollutants is that of the catalytic converter present in the exhaust manifold that cleans emissions from the internal combustion engines of gasoline- and diesel-fiieled automobiles and trucks. As modem commercial passenger jets fly above 30,000 feet there is a need to destroy the few ppm ozone that enters the airplane with make-up air to ensure passenger and crew comfort and safety. Radiators on select... 

The American 1970 Clean Air Act defined ambient air quality standards (NAAQS) in the United States for atmospheric ozone, NO, lead, carbon monoxide, sulfur oxides, and PM-10 (particulate matter less than 10 p.m). The strategy to reduce levels of lead, NOx, PM-10, and to some extent carbon monoxide was to control emissions from automobiles that included the phasing-out of leaded fuel. As previously noted, ozone is a product of the photochemical reaction of volatile organic compounds with NOx (photochemical smog), so the balance between organic compounds and NOx pollutants is important in meeting target ozone levels (e.g., 0.12 ppm). Emissions from stationary sources is an important factor, and limits have been set for them. Because of low pressure drop requirements, coated monolithic catalysts... 

Appreciable interest has been generated in the use of activated carbons for flue gas cleanup, especially for the removal of SOx and NO the adsorption of mercury from flue gases was discussed earlier. From the environmental point of view, emissions from the combustion of fossil fuels in power plants and similar industrial processes are major contributors to a lowering of air quality. The flue ga.ses carry traces of SOi and NO, which can be oxidized and converted to their acid forms in the presence of atmospheric water vapor, and they may also combine with other volatile organics to form ozone and smog. Similarly, low level SOj and NOx emissions from automobiles, while insignificant for individual vehicles, become a large source of pollution when multiplied by the millions of vehicles that are on the roads. 

The Clean Air Act Amendments of 1970, which followed the original Clean Air Act of 1967, set national air quality standards for six criteria air pollutants NOx, SOx, ozone, carbon monoxide (CO), particulates and lead. The result was the removal of lead from gasoline and the installation of emission control technologies, including baghouse filters for particulate control, wet and dry scrubbers for SOx control and automobile exhaust catalysts for controlling hydrocarbons (HC), CO and NOx. As a consequence, lead emissions have been dramatically reduced, SOx emissions are being controlled, and automobile CO, HC and NOx emissions have decreased by nearly a factor of 10 (over uncontrolled emissions). In spite of these dramatic improvements, in 1989 approximately 130 million people in the U.S. lived in 96 areas which did not meet air quality standards either in ozone, in carbon monoxide, or in both [2]. 

The most abundant hydrocarbon in the atmosphere is methane, CH4, released from underground sources as natural gas and produced by the fermentation of organic matter. Methane is one of the least reactive atmospheric hydrocarbons and is produced by diffuse sources, so that its participation in the formation of pollutant photochemical reaction products is minimal. The most significant atmospheric pollutant hydrocarbons are the reactive ones produced as automobile exhaust emissions. In the presence of NO, under conditions of temperature inversion (see Chapter 16), low humidity, and sunlight, these hydrocarbons produce undesirable photochemical smog, manifested by the presence of visibility-obscuring particulate matter, oxidants such as ozone, and noxious organic species such as aldehydes. 

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