Variability of Atmospheric Aerosol and Ozone Concentrations at Marine, Urban, and High-Altitude Monitoring Stations in Southern Italy during the 2007 Summer Saharan Dust Outbreaks and Wildfire Episodes.

In order to evaluate the spatial variation of aerosol (parti- culate matter with aerodynamic diameter 10 m m [PM 10 ]) and ozone (O 3 ) concentrations and characterize the atmo- spheric conditions that lead to O 3 and PM 10 -rich episodes in southern Italy during summer 2007, an intensive sam- pling campaign was simultaneously performed, from mid- dle of July to the end of August, at three ground-based sites (marine, urban, and high-altitude monitoring stations) in Calabria region. A cluster analysis, based on the prevailing air mass backward trajectories, was performed, allowing to discriminate the contribution of different air masses origin and paths. Results showed that both PM 10 and O 3 levels reached similar high values when air masses originated from the industrialized continental Europe as well as under the influence of wildfire emissions. Among natural sources, dust intrusion and wildfire events seem to involve a marked impact on the recorded data. Typical fair weather of Mediterranean summer and persisting anticyclone sys- tem at synoptic scale were indeed favorable conditions to the arrival of heavily dust-loaded air masses over three periods of consecutive days and more than half of the observed PM 10 daily exceedances have been attributed to Saharan dust events. During the identified dust outbreaks, a consistent increase in PM 10 levels with a concurrent decrease in O 3 values was also observed and discussed