الفهرس 
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Abstract
Motor vehicles are consi dered one of the major ail’ pollution sources in urban residential areas. especially in large town$ . Compared with stationary sources, the type of combustion process that occurs in the eng i ne of a motor vehicle produces high concentrations of pollutants, and the exhaust gases from vehicles are discharged directly into the street, often near people. Vehicular emissions are also the predominant source of ail’ pollutants that affect people health and the environment. These pollutants are total suspended particulates (TSP>, lead (Pb>, hydrocarbons (HC> nitrogen dioxide (NO:z> and carbon monoxide (CO> . The levels of these pollutants in the street env i ronment are af-fected by several important factors including type of fuel (diesel or gasoline>, traffic density, mode of eng i ne operation, perpendicular and vertical distances from roads, and the meteorological conditions. Increasing urbanization and motorization is accompanied by increasing negative health effects not only from an ” increasing number of accidents, but also from the emissions of the eng i nes powering the vehicle;. Pollutants and their derivatives can cause adverse health ef-fects by interacting with, and impairing, molecules crucial to the biochemical or physiological processes of the human body. Also, the large amounts of traffic pollutants emitted into the atmosphere are of great and direct adverse effects on the envir-onmental elements such as vegetation, mater-ials , visibility, and climate. The pr-esent study was dir-ected towards the assessment of traffic pollutants including TSP, Pb, Benzene soluble organic matter (BSOM), or-ganic dust, sulfate (S04-2), ni trate (N03-), NO:z and CO in some main str-eets in the city of Alexandria dur i ng the per-iod fr-om October 1991 to February 1993 . It includes a description of geography, population, industrial commercial and traffic activities of Alexandria. Thirty air sampling stations were selected for the pr-esent study, representing most of the main streets in Alexandria. These stations were located on the side walks beside police, traffic and fire stations. Most of these stations were used for- collecting tr-affic pollutants for- two weeks, and some of them were visited more than once dur i ng the period of study for- evaluating the effect of seasonal var-iation. Three traffic air pollutants; TSP , N02 and CO were collected daily from the sampling stations, while sulfur d i 0 x i de (S02) was not considered a major traffic pollutant. Total suspended particulates were collected for 24 hours on fiber glass filter usi ng the standard high volume sampler. Nitrogen dioxide was determined by the Saltzman method, which is based on the formation of a stable pi nk calor after absorption of N02 i n Griess-Saltzman r-eagent . Samples of ca,-bo;””, mono,,: de wet’e c:ollected ft’om ~he sampling stations in plastic bags and tr-ansported to the laborator-y for- analysis. Arter the collection or TSP , the riber glass rilter was divided into rour quarters ror the determination or water soluble rraction (sulrate and nitrate) benzene soluble organic matter (BSOM) lead and organic dust. Sulrate content or the water soluble fraction is determi ned by the Turbidimetric Barium Sulfate Method, while nitrate is analyzed by the 2,4 Xylenol method. Lead is determined physically by atomic absorption spectrometry . BSOM are extracted rrom dust with redistilled benzene using a Soxhlet Extractor, while the organic dust is determined by, i g nit ion the samples at high degrees or temperature in a murrle rurnace. Arter absorption or N02, the rormed pink color is read in a spectrophotometer, and its concentration is determined using a standard curve. Samples or co were withdrawn rrom tf1e plastic bags and injected into an inrra red spectrophotometer, called MIRAN-IA Analyzer , where the absorbance values or the samples are read, and the corresponding concentrations of CO are determined rrom a standard curve. Results or the trarric pollutants including TSP and their constituents, N02 and CO oBtained rrom the thirty sampling stations were analyzed and discussed. It was round that the levels Or trarric pollutants dur i ng weekends and holidays were lower than that during the rest or weekdays. This mainly Due to -c.he reducIng of traffic oensity during the weekends (Fridays and Sundays) in the city or Alexandria. l The highest levels oT t~aTTic pollutants we~e Tound in sampling stations that located in nar~ow streets with poor pavement and cleanliness, rows oT tall buildings 0 n bo t h sides, and nea~ stop t~aTTic lights or inte~sections , while the lowest concent~ations were in ~be stations located in wide streets with open areas and near the sea. This means that the street conditions play an important role on the traTTic pollutant levels over Alexandria. The levels oT most traTTic pollutants obtained Trom , sampling stations t h’a t located near industrial areas, were higher than that oT the commercial or residential areas. This is because oT the large amounts oT pollutants emitted Trom the industrial sources that raise the level oT these pollutants in the street environment. Seasonal variations have no pronounced effect on the traffic pollutant levels in the city oT Alexandria. In general, most oT these levels increase during the Tall and spring seasons because oT the high percentage oT calm wind and inversion condi tions’ during the Tall season and the sandy storms during the spring seasons. In winter and summer, the levels oT pollutants decrease by the action oT rainTall in winter and the high percentage oT the wind blowing Trom the sea during the summer season. The comparison between -factors affecting the tra-f-fic pollutant levels in Alexandria showed that street condition are the major -factor, -followed by area activity (industrial, commer-cial or resi dential) , seasonal variation, and the lowest one is the weekend-weekday tra-f-fic variation. The levels o-f all pollutants in the str-eet environment (tra-f-fic air pollution) were twice or more the overall level of pollution in the air over the city o-f Alexandria. This means that large portion o-f the population, especially inhabitants of lower- -floor apartments looking onto streets o-f heavy tra-f-fic , shopkeepers, policemen, and pedestrians are exposed to levels o-f tra-f-fic pollutants higher than others. Except TSP , the levels of all tl~a-f-fic pollutants were below the U.S. National Ambient Air Quality Standards (NAAQS) in all streets of Alexandria. Levels of TSP were higher than the annual geomett~ i c mean (75 ~g/m3) in all streets o-f the city, and mosl: of these levels welre also above the maximum 24-hour- concentration (260 ~g/m3). ^leng