THE INFLUENCE OF VEHICLE EMISSION CHARACTERISTICS AND METEOROLOGICAL CONDITIONS ON URBAN NO2 CONCENTRATIONS

A major fraction of nitrogen oxides released from traffic is commonly nitrogen monoxide (NO); however, the proportion of NO2 in exhaust emissions can range from less than 1% to more than 50%. The released NO is chemically transformed into the more harmful nitrogen dioxide (NO2); the reaction time-scale is typically a few minutes in urban daylight conditions. This paper presents numerical results concerning the influence of the tailpipe NO2/NOx fraction and meteorological conditions on the ambient air NO2 concentrations. We have applied the road network dispersion model CAR-FMI in the computations.