Source apportionment in the town of La Spezia (Italy) by continuous aerosol sampling and PIXE analysis

We describe the results of an aerosol sampling campaign performed in 1999 in the medium-size industrial town of La Spezia, in the Northwest of Italy. We used two-stage continuous streaker samplers in three different sites and periods of the year. This kind of samplers allows the separation of the PM10 and PM2.5 fractions of the particulate matter. Moreover, the hourly resolution in the aerosol collection is particularly useful in an urban environment where, typically, many pollution sources with fast variations are present. Up to 1700 samples have been analysed by Particle Induced X-ray Emission (PIXE) at the INFN accelerator facility in Florence, obtaining hourly concentration for about 20 elements from Na to Pb, with a sensitivity ranging from below 1 to about 10 ng m(-3). The total hourly aerosol mass has been estimated with an optical analysis of the same samples performed (before the PIXE analysis) by an equipment designed and mounted in Genoa. An extensive statistical analysis of the data included standard and Absolute Principal Component Factor Analysis (PCFA and APCFA) to deduce the composition and the weight of the major aerosol sources in both fractions. Thorough different statistical approaches, we generally resolved contributions from vehicle emission, fossil fuel combustion, soil-road dust and sea salt aerosol.