The role of PIXE in the AIRUSE project "testing and development of air quality mitigation measures in Southern Europe"

The European AIRUSE LIFE+ project aims at testing existing and future mitigation measures and developing new strategies for the improvement of air quality in Southern European countries. The project involves public and private institutions of Spain, UK, Portugal, Italy and Greece. PM10 and PM2.5 daily samplings have been scheduled for one year (from January 2013) in four urban sites, Barcelona (Spain), Porto (Portugal), Athens (Greece), and Florence (Italy). The daily data set gives an overall representative picture of the PM composition in these urban sites. The project includes also samplings with hourly resolution for limited periods. Hourly samples give an easier identification of the different aerosol sources due to the capability of tracking rapid changes as the ones occurring in many particulate emissions as well as in atmospheric transport and dilution processes. The role of PIXE technique within the project has been described in this paper. The comparison of data obtained by different techniques (e.g. PIXE, IC and ICP) assured a quality assurance control on the huge quantity of data obtained in the project. PIXE data together with those obtained by other analytical techniques have been used to reconstruct the average aerosol chemical composition and in Positive Matrix Factorization (PMF) analysis to determine the aerosol sources and their impact on PM10 and PM2.5 mass. In particular the high sensitivity of PIXE for all the crustal elements (including Si which is not easily detected by ICP) allows the direct determination of the Saharan dust contribution. Finally, the 1-h resolution data, which can be obtained only by PIXE, confirmed and reinforced the identification of the aerosol sources obtained by the daily concentrations.