The focus of this research was the examination of the emission and transformation of nitrogen oxides emitted from vehicles. Measured data for this experiment were collected from May 1 thru May 31, 2002, and were compared to values modeled with CALINE4. CALINE4 is a photochemical and dispersive model used to predict concentrations of NOX (NO+NO2) from line sources. The measurement campaign was coincident with the Bay Regional Atmospheric Chemistry Experiment (BRACE). An ambient air quality monitoring site was constructed adjacent to Gandy Boulevard, in Tampa, FL. When comparisons of measured and modeled NO and NO2 values were made it was found that CALINE4 underpredicted NO2; i.e., underpredicted the conversion of NO, for both daytime and nighttime conditions. Possible causes of this bias were investigated and it was found that the simple kinetic mechanism present in CALINE4 was not sufficient to account for all of the reactions occurring. A simulation was run with a more comprehensive NO conversion mechanism and it was found that the reactions containing peroxy radicals affected the conversion rate but were not present in the simple CALINE4 mechanism. The simulation runs suggested that the ratio of radicals to O3 remained nearly constant during the course of the reaction. This pointed to an improved mechanism where the photolytic rate constant in CALINE4 could be replaced with a new constant, keff. This brought theday time calculations within reasonable agreement of the measured values, including an unexpected improvement in nighttime concentrations. Specifically, this modification eliminated the negative fractional bias in calculated daytime NO2 concentrations, moving it from -0.16 to 0.043. The fractional bias in nighttime calculations was improved from -0.17 to -0.036. Average hourly traffic counts were then used as inputs to the model to compare to the entire month of May 2002 data and it was found that the daytime fractional bias was improved from -0.27 to -0.06 and the nighttime from -0.35 to -0.24

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De nos jours, la pollution atmosphérique particulièrement issue du trafic routier en milieu urbain dans l’Union Européenne, a été associée à une augmentation de la prévalence des maladies respiratoires. Parmi ces maladies associées, l’asthme constitue aujourd’hui un réel problème de santé publique particulièrement chez les enfants. Cracovie, ville inscrite au patrimoine mondial de l’UNESCO, est un terrain d’étude pertinent dans la mesure où la source de pollution du trafic routier est prédominante et où des relations ont été établies entre la mauvaise qualité de l’air et le développement de l’asthme chez les enfants. Une démarche méthodologique pluridisciplinaire d’évaluation du risque sanitaire, combinant des approches de statistiques, de modélisation CALINE4 et d’épidémiologie à l’aide du système d’Information Géographique, a été élaborée afin de mettre en exergue des relations significatives entre la pollution issue du trafic routier et l’asthme infantile. Les plus forts Risques Relatifs Sanitaires ont été mis en évidence jusqu’à 300 m de la chaussée et particulièrement au niveau des axes routiers stratégiques de Cracovie, tels que les axes reliant les deux centres-villes historique et moderne de Cracovie ou ceux constitutifs de la rocade. Ces axes routiers traversent les quartiers les plus densément peuplés où résident aussi les plus fortes proportions d’enfants les plus vulnérables face à l’asthme. Ce résultat pourrait inciter le gestionnaire à intervenir pour améliorer le plan de déplacement urbain de Cracovie et d’autres villes avec des problématiques semblables afin de limiter l’impact de la pollution issue du trafic routier sur le développement de l’asthme infantile. / Nowadays, the air pollution particularly emitted from road traffic in urban areas in the European Union, was associated with an increased prevalence of respiratory diseases. Among these associated pathologies, asthma is now a real public health issue particularly among children. Cracow, a city declared as a UNESCO World Heritage, is a relevant field study insofar as the source of air pollution, the road traffic is predominant and insofar as relevant relationships were shown between poor air quality and the development of asthma among children. A multidisciplinary methodological approach of health risk assessment, combining statistical, modeling CALINE4 and epidemiological approaches using Geographic Information System was developed to highlight relevant relationships between air pollution generated by road traffic and childhood asthma. The strongest Health Relative Risks have been highlighted up to 300 m from the roadway and particularly on the strategic roads of Cracow, i.e. the roads linking the two historic and modern downtowns of Cracow or the constitutive road of the bypass. These roads pass through the most densely districts where also lives the highest proportion of children most vulnerable to asthma.These results could encourage the planner to review the urban transport plan of Cracow and other cities with similar problems, in order to limit the impact of road traffic air pollution on the development of childhood asthma.