La pollution automobile à Paris influence du trafic et des conditions météorologiques

Abstract The improvement of urban air quality is a major challenge namely for NO 2 (nitrogen dioxide), a toxic pollutant controlled by the European Regulation EEC n o 85–203. We now know that eatalytic converters reduce car emissions and we believe that a reduction in traffic (already enforced in some cities) and the restriction of vehicle road traffic, applied to some European towns, is an area for further research. In Paris, the existance of periods of serious pollution (essentially due to NO 2 levels reaching >200 μg/m 3 in periods of several hours) has made the public and public administration aware of the importance of this problem. Thus, a commitment has been made to reduce these periods of severe pollution. The study being presented deals with the search for a correlation between vehicle traffic (vehicle flow/hour) and measured concentrations of NO, NO 2 and CO at two sites in Paris, in 1992. This relation has been established by plotting the traffic levels against concentrations of each gaseous effluent. When the pollutants are well dispersed it is possible to plot the concentrations of NO and NO 2 . The slope is much steeper for NO than for NO 2 . On the other hand, when meterological conditions are unfavourable (high pressure zone, stability of the atmosphere, temperature inversion or strong solar radiance) no significant correlation could be observed. This proves the predominance of meteorological conditions on NO 2 levels during high pollution periods. The study also confirmed that NO is a very good indicator of car pollution, taking into account the increasing number of diesel powered vehicles in France.