Pollution from automobile emission

Nonpoint sources of pollution are more difficult to measure because they often cover large areas or are a composite of numerous point sources. Examples of nonpoint sources include pesticide and fertilizer runoff from agricultural fields, and urban runoff contaminated with pollutants from automobile emissions. Nonpoint sources may not be directly located next to a surface water body pollutants may be transported to surface waters by runoff from the land, by groundwater inflow, or by atmospheric transport. 

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. 

Hexane may be expected to comprise around 2% of the VOCs in urban air polluted with hydrocarbons from automobile emissions or other combustion byproducts (Barrefors and Petersson 1993). The -hexane concentrations in urban air will typically be approximately 60% of the concentrations of benzene (Daisey et al. 1994). Close proximity to the exhaust systems of cars or other gasoline-powered vehicles can lead to exposures to increased concentrations of -hexane. Under rush-hour conditions, the concentrations in the interior air of buses will tend to be lower (55 g/m3 or 19.8 ppbv) than the interior levels in cars (69 g/m3 or 24.9 ppbv) or the air around persons riding motorcycles (106 g/m3 or... 

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 ... 

The main application of rhodium is the production of catalytic alloys with other platinum metals. These alloys are used to reduce the emission of pollutants from automobile exhausts and to catalyze the formation of nitric acid from ammonia. 

In areas where photochemical air pollution is a serious problem, the olefins and other more reactive hydrocarbons are major concerns rather than just with the total organic emissions. Using factors mainly derived by the Bay Area Air Pollution Control District in San Francisco (5), the total emissions of organic materials have been broken down to give an estimate of the reactive hydrocarbon emissions. About one-third, or about 27 X 10 tons, are considered reactive out of the 88 X 10 total tons of organic materials over half of the estimated reactive emissions result from automobile emissions. 

Reduction of pollutant gases of CO, HCs and NO c from automobile emissions is currently achieved by the use of three-way catalysts (TWC), which can oxidise CO and HCs into CO2 and H2O, while simultaneously reducing NO into N2, provided the TWC is operated at stoichiometric air/fuel ratio, as shown in figs. 32 and 33. The air/fiiel ratio is normally defined in terms of lambda (A) ... 

Carbon monoxide in auto exhaust is the result of incomplete combusting of gasoline in the engine. The removal of this major pollutant from auto emissions by conversion to CO2 via this reaction is one of the primary functions of catalytic converters in automobiles.)... 

Reduction in the amount of pollutant gases from automobile emissions is a worldwide concern. To decrease the amount of pollutant gases, a catalytic converter is installed into the exhaust gas stream of automobiles. The catalyst is called a three-w catalyst. The gases which cause air pollution in the exhaust are hydrocarbons, carbon monoxide and nitric oxides. The catalyst oxidizes both hydrocarbons and carbon monoxide into CO2 and H2O, and also reduces nitric oxides into nitrogen. Decrease of these three main pollutant gases is presented in fig. 1 (Oohata 1990, Adachi 1991). 

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 Clean Air Act of 1990 establishes tighter pollution standards for emissions from automobiles and trucks. These standards will reduce tailpipe emissions of hydrocarbons, carbon monoxide, and nitrogen oxides on a phased-in basis beginning in model year 1994. Automobile manufacturers will also be required to reduce vehicle emissions resulting from the evaporation of gasoline during refueling. 

Minimization of pollutants from the combustion chamber. This approach consists of designing the engine with improved fuel-air distribution systems, ignition timing, fuel-air ratios, coolant and mixture temperatures, and engine speeds for minimum emissions. The majority of automobiles sold in the United States now use an electronic sensor/control system to adjust these variables for maximum engine performance with minimum pollutant emissions. 

At the local level, air pollution concerns a region within a 5-km radius. It is characterized by high concentrations of specific pollutants that may come from automobiles or industrial activities in that region. For example, emissions from vehicles can lead to high concentrations of carbon monoxide near traffic-jammed roads. High buildings and the terrain can also contribute to high local concentrations of pollutants. 

Her predecessor on the chair as Minister of Environment and Energy, Birgitta Dahl (now speaker for the Parliament), had shown the way almost a decade earlier. In April 1989, in front of an audience from the Stockholm Worker s Commune, Mrs. Dahl claimed that automobile emissions had passed cigarette smoking as the main cause of lung cancer in Sweden The SCC appointed by Mrs. Dahl s own party comrades had found that air pollution accounted for not more than about one percent of all cancers in the Swedish population. But why should a Minister of Environment bother about checking scientific information ... 

Several working groups have analyzed platinum group elements (PGEs) as possible markers of anthropogenic pollution in aerosols (in airborne particulates from automobile exhaust to check the emission of catalysts), mainly by ICP-MS.49 50 Airborne particles were also investigated with respect to selected element species (e.g., of Hg and Pb) by GC-ICP-MS.51,52... 

Tremp, J., P. Mattrel, S. Fingler, and W. Giger, Phenols and nitrophenols as tropospheric pollutants Emissions from automobile exhausts and phase transfer in the atmosphere , Water Air Soil Pollut., 68,113-123 (1993). 

Indoor air quality is an important determinant of health and well-being. To maintain better indoor air quality, we have to understand the mechanism of indoor air pollution. For this purpose, the measurement of indoor air concentration and use of chemical analysis methods are essential. To estimate indoor air concentration, we have to know the emission and ventilation rates. Emission takes place not only from building products but also from automobile parts, electric appliances, office equipment such as printers, household consumer products, and even printed materials like newspapers. This book serves as a useful guide for chemists, architects, mechanical engineers, constructors, and manufacturers of electronic products. It emphasizes a holistic and multidisciplinary approach toward the indoor environment. 

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