Is PIXE still a useful technique for the analysis of atmospheric aerosols? The LABEC experience

At the 3-MV Tandetron accelerator of LABEC (INFN) an external beam facility is fully dedicated to particle-induced X-ray emission (PIXE) and particle-induced gamma -ray emission (PIGE) measurements of atmospheric aerosol elemental composition. All the elements with Z > 10 are simultaneously detected by PIXE in a few minutes and an automatic system for positioning, changing and scanning of the samples allows the analysis of the aerosol collected by different kinds of devices: long series of daily PMX samples can be measured in short times, as well as size-segregated and high time-resolution aerosol samples. Thanks to the capability of detecting all the crustal elements, PIXE-PIGE analyses are unrivalled in the study of mineral dust: as a consequence, they are very effective in the study of natural aerosols, like, for example, mineral dust archived in polar ice cores (for environmental and paleoclimatic studies) and Saharan-dust intrusions. Among the detectable elements, there are also important markers of anthropogenic sources, which allow effective source apportionment studies in polluted urban environments. Examples regarding recent monitoring campaigns, performed in urban and remote areas, both on a daily basis and with high-time resolution (hourly samples), are presented to evidence how PIXE can still provide unique information in aerosol studies or can play a complementary role to X-ray fluorescence or induced coupled plasma mass spectroscopy analysis.