Modelling of PM10 concentrations over Milano urban area using two aerosol modules

Fine particulate air pollution represents one of the most relevant environmental concerns in Lombardia region (Northern Italy). PM10 concentrations overcome air quality limit values especially during wintertime, when frequently occurring thermal inversions and calm conditions tend to inhibit pollutants dispersion. To have a better understanding of the spatial distribution of PM10, a modelling system has been applied to a winter PM10 episode considering a computational domain centered on Milano metropolitan area. The modelling system software suite is based on an Eulerian photochemical model (FARM – Flexible Air quality Regional Model) and includes an emission pre-processor to apportion data from the regional emission inventory, a diagnostic meteorological model coupled with a micrometeorological module and data visualization and post-processing tools. FARM model has been applied with two aerosol modules: the aero3 modal aerosol module implemented in CMAQ framework and a bulk aerosol module (aero0), based on a simplified thermodynamic scheme. Both tested modules show a good agreement with observed concentrations. A performance analysis of modelling results by means of typical statistical measures has evidenced an acceptable model performance for both models and a better reproduction of PM10 levels using the more complete aerosol module (aero3). Furthermore, the application of the latter aerosol module provides a PM10 chemical composition that results in good agreement with data collected within Milano urban area.