The influence of vehicle emission characteristics and meteorological conditions on urban NO2 concentrations

A major fraction of nitrogen oxides released from traffic is commonly nitro gen 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 tra nsformed into the more harmful nitrogen dioxide (NO2); the reaction time-sc ale is typically a few minutes in urban daylight conditions. This paper pre sents numerical results concerning the influence of the tailpipe NO2/NOx fr action and meteorological conditions on the ambient air NO2 concentrations. We have applied the road network dispersion model CAR-FMI in the computati ons.