Influence of synoptic meteorological conditions on particle size distributions collected in two urban street canyons in the city of Bologna

The Horizon H2020 iSCAPE (“Improving the Smart Control of Air Pollution in Europe”, GA No. 689954; www.iscapeproject.eu) project aims to study the interactions between urban climate and atmospheric pollution in some European cities. The city of Bologna was selected as pilot city due to its strategical location within the Po Valley, a recognized hot-spot in terms of air quality and climate change. The whole Po Valley is also characterized by high population density and heavily busy areas. During wintertime, poor ventilation conditions, strong thermal inversions and atmospheric pollution build-up frequently favors the formation of fogs in this region, even though fog events in the city of Bologna fog events are not as frequent as elsewhere in this region, where however they tend to occur less and less frequently. Two Optical Particle Counters were deployed within the winter 2018 intensive experimental campaign carried out in two different street canyons (Marconi and Laura Bassi Veratti Sts.) located in the city of Bologna, characterized by the same North-South geographical orientation and similar traffic volumes, but different geometric structures and presence of vegetation: in fact, while Laura Bassi Veratti St. presents a tree line along both sides of the street, vegetation is almost absent in Marconi St. This work presents the comparison between particle size distributions collected at the two experimental sites, as well as the influence of different synoptic meteorological conditions (clear sky, rain, snow) on particles number densities.