Abstract
The analysis of aerosol size distributions is a useful tool for understanding the sources and the processes influencing particle number concentrations (N) in urban areas. Hence, during the one-month SAPUSS campaign (Solving Aerosol Problems by Using Synergistic Strategies, EU Marie Curie Action) in autumn 2010 in Barcelona (Spain), four SMPSs (Scanning Mobility Particle Sizer) were simultaneously deployed at four monitoring sites: a road side (RSsite), an urban background site located in the city (UBsite), an urban background site located in the nearby hills of the city (Torre Collserola, TCsite) and a regional background site located about 50 km from the Barcelona urban areas (RBsite). The spatial distribution of sites allows study of the aerosol temporal variability as well as the spatial distribution, progressively moving away from urban aerosol sources. In order to interpret the data sets collected, a k-means cluster analysis was performed on the combined SMPS data sets. This resulted in nine clusters describing all aerosol size distributions from the four sites. In summary there were three main categories (with three clusters in each category): "Traffic" (Traffic 1, "T-clus_1" - 8 %; Traffic 2, "T-clus_2" - 13 %; and Traffic 3, "T-clus_3" - 9 %) "Background Pollution" (Urban Background 1, "UBclus_1" - 21 %; Regional Background 1, "RBclus_1" - 15 %; and Regional Background 2, "RBclus_2" - 18 %) and "Special Cases" (Nucleation, "NUclus" - 5 %; Regional Nitrate, "NITclus" - 6 %; and Mix, "MIXclus" - 5 %).