Ground-based measurements of long-range transported aerosol at the rural regional background site of Monte Martano (Central Italy)

Abstract

Aerosol mass (PM10 and PM2.5) and chemical composition recorded in the 2009 at the rural background station of Monte Martano (MM, Central Italy) are presented in this work. The site, located at 1100m (asl), features relatively low aerosol mass levels, due to the little influence of local anthropogenic pressure, and is influenced mainly by long-range transport phenomena. Chemical composition of PM10 and PM2.5 at MM is characterized by high levels of organic matter (OM), sulfates and nitrates, followed by crustal material, and ammonia. Sea Spray and elemental carbon (EC) accounted for a minor part of the total PM mass. The mass trends (PM10 and PM2.5) and chemical characteristics (OC, EC, major ions, trace elements) are compared with those of other similar sites in Europe and discussed in the framework of an extensive analysis of back trajectories (BT). As a result, three main advection routes to Central Italy (Northern Africa, West Mediterranean and Eastern Europe) have been individuated on the basis of the BT analysis and show significantly different PM2.5/PM10 and OC/EC ratios. Major ions and trace elements trends are also discussed within this framework, showing that annual averages are more influenced by long-range transport from Eastern Europe, which is the prevalent advection route to MM (and Central Italy) also according to BT analysis. Finally, the data collected allowed to estimate the impact of Saharan dust on PM10 which amounted to 22μgm-3 per intrusion event (22 events). The impact on PM2.5 resulted in 11μgm-3 per intrusion event.