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In this paper, we have applied an extensive back-trajectory calculation to describe a complex atmospheric circulation pattern in the Central Mediterranean, registered in late spring 2013, which led to successive advections of biomass burning and Saharan dust aerosols over Italy. We based our study on chemical results obtained at the two background Italian sites of Monte Martano and Lampedusa. The two sites feature different local aerosol sources and are geographically distant. In order to distinguish the contribution of long-range sources associated with the advection event, we set up a potential source contribution function analysis of the chemical composition of PM10sampled at both sites. The main goal was to individuate the variability of the aerosol composition associated with the long-range transport and to trace back the source areas. We discussed the case of study in the context of the unusual synoptic meteorological conditions during the observational period. The wide geographical scale covered in this study allowed us to explore the extent to which an aerosol intrusion from Eastern Europe may impact on the Central Mediterranean. Also, we pointed out how a sudden shift of the synoptic meteorological conditions can induce, in a few days, a complete change in the chemistry of airborne dust, due to a contribution from Sahara, which was more significant in Central Italy with respect to lower latitudes.

Si dimostrano un teorema di unicità ed un teorema di esistenza per sistemi ellittici simmetrici a coefficienti costanti di equazioni alle derivate parziali del primo ordine semilineari in aperti di classe $ {C^1}$.