Analysis of pollutants exchange between the Po Valley and the surrounding European region

The Po Valley is a major populated area including different conurbations, with a population density among the highest in Europe. The region is an air pollution hot spot, where the European air quality standards are exceeded for PM10, NO2 and O3. The pollutants exported from the Po Valley to the surrounding areas have been investigated through the application of a chemical transport model. Emission sensitivity simulations have been performed to identify the Po Valley footprint and to quantify its influence on the atmospheric composition. Simulation results suggest that the Po Valley emissions impact extends up to 500 km, affecting Italy, the northern Mediterranean sea and the western Balkan peninsula. The outflow directions are determined by meteorological and topographic forcing. The surface area affected is larger during the winter, while the mass injected in the free troposphere is larger during the summer for pollutants with longer lifetime. Secondary PM components show an impact area wider than the other pollutants. NO2 footprint and its contribution to local concentration are relevant especially during wintertime. The Po Valley emissions contribute to the production of ozone at regional scale during the summer, although this contribution remains limited to few percentage points of local concentration levels.