Pollutants emissions in a urban area: definition of emission factors, atmospheric dispersion modelling and support of intervention policies

Within a urban context, the most important pollutants that should be studied and reduced in a urban context in order to ensure the sustainability of the metropolitan environment are NOx and PM10. While the emission factors for NOx are well known for all the sources, the PM emission from traffic are of two types, exhaust and nonexhaust. The latter type of emission is due to vehicle components’ wear (tyres, brakes), road abrasion and dust re-suspension and its quantification is not straightforward. In this paper we tried to calculate the total PM emission factors due to traffic by means of the measured PM concentrations for a 50,000 inhabitants town in NW Italy. Then we assessed the different contributions to air quality due to the different emission sources in two medium towns of NW Italy, both for PM10 and NOx. An important effort has been made in order to define the background concentration due to stagnation phenomena of pollutants within the urban contexts. The described approach should be applied in order to understand who is the main responsible of the existing critical condition of air quality and to get some general information on the positive effect obtainable through different intervention policy.