Seasonal and weekly pattern of atmospheric particles in a urban background site in the Po valley, Italy

Combined measurements of number and weight particle concentration have been performed in an urban background site in the Po valley, Italy. Particle count measurements have been performed by Scanning Mobility Particle Sizer: number concentration for particles with diameter ranging between 10 to 700 nm are acquired each 120 seconds in the grounds of the University campus. PM2.5 is measured by TEOM-FDMS: the instrument estimates hourly particle weight concentration performing a correction for losses of semi-volatile particles collected on the sampling filter, whose temperature is kept at 30°C. The data analyzed in this study have been collected from February to August 2008. Daily and weekly pattern of total particle count, particle number size distribution and weight concentration have been investigated, along with meteorological data. Number concentration peaks resulted mostly related to morning and evening rush-hour traffic, particularly in winter; weight concentration resulted influenced both by anthropic activities and atmospheric dispersion conditions and shows a different diurnal pattern. Coagulation of finer particles occurs after evening rush-hour, mostly during wintertime. An analysis of the most and less polluted days of the investigated period has been performed, and the daily patterns of pollutants have been compared for both seasons.