Micro-PIXE and principal component analysis in a study of internal mixing phenomena in Antarctic coastal aerosol

Two thousand eight hundred aerosol particles belonging to the four supermicrometric stages of three size-segregated samples of Antarctic coastal aerosol were submitted to single particle (SAP) micro-PIXE analysis. In almost all particles at least the three elements Na, Mg and Cl are detected. The multielemental data corresponding to each individual size-segregated subsample were separately submitted to principal component analysis (PCA), using these elements. One principal component (PC) alone always explains at least 92% of the total variance and can be geochemically identified as sea-salt-PC (ssPC). The description by PCA of the important fraction of particles containing not only the three above elements, but also, at least, the crustal elements Al and Si, implies two modifications: the need for a second PC (crustal-PC) describing crustal materials; the appearance of covariant enrichments in crustal materials, in particular Al and Si, in ssPC. Both modifications imply an internal mixing of sea-salt and insoluble particulate crustal materials. Implications thereof for particles origin and interactions are considered