Modèle statistique pour la gestion de la qualité de lʹair

With 531 motor vehicles for 1000 inhabitants (1992), the Geneva area has one of the highest motorization rates of the world. The consequence of such a situation is that motor vehicle traffic is the main source of nitrogen oxide emissions, leading to excess immissions of nitrogen dioxide. The federal ordinance relating to air protection (OPair), defines limit values for immissions. A monitoring network for measurement of atmospheric pollution has been installed since 1986. It consists of eight fixed stations. It can evaluate and follow the evolution of air quality. We developed a statistical model, connecting calculated annual emissions of nitrogen oxides and average year immissions of nitrogen dioxide measured by the air pollution monitoring system in Geneva. Motor vehicle pollution is calculated using a traffic model for simulating traffic changes and assessing the consequences on air pollution emissions. The influence of weather conditions is estimated by means of a statistical model which weights nitrogen dioxide immissions as a function of typical meteorological situations. The relation between emissions and immissions can be expressed in the form NOx = A + B + C. Where A is in relation with the background immission, B with the emissions on a grid of 1 km × 1 km, and C with a translocal emission which depends of the distance from the townʹs center. The relation between NOx and NO2 can be expressed in the form NO2 = K·Noxα. The model is calibrated with the monitoring network measurement. The year 1988 is used as reference year.