The particulate matter in the stack effluents of an oil-fired power plant at different loads was collected and fractionated with an in-stack cascade impactor and a particle inertial spectrometer. The concentration, the size distribution, and the particle density of the aerosols sampled have been determined. The elemental composition was measured as a function of particle size by means of proton induced x-ray emission (PIXE) and atomic absorption spectroscopy (AAS). The morphological characteristics (shape, surface feature) and the mineralogical compositions of single particles have been performed by scanning electron microscope (SEM), mineralogical microscope (MM), and x-ray diffractometer (XRD): spherical carbonaceous particles constitute the main typology observed; the presence of vanadate has also been observed. -- AATA