Chemical composition and sources of fine and coarse aerosol particles in the Eastern Mediterranean

Size-segregated aerosol samples have been collected at a coastal site on Crete Island, Eastern Mediterranean, during the period July 2004–July 2006. In total, 180 samples have been collected and analyzed for the main anions, cations, elements, OC and EC at both fine ( D a < 1.3 μm) and coarse (1.3 μm < D a < 10 μm) fractions. The fine and coarse mode OC and EC values reported in this work are the first long-term data published for the Eastern Mediterranean basin. A significant part of OC in the coarse mode (up to 20%) originates from carbonates, and subsequently particulate organic matter (POM) concentration would be overestimated without carbonate exclusion. The carbonate corrected, coarse mode OC correlates significantly with the dust content, indicating that mineral dust particles can serve as reaction surfaces for different species, including those of man-made origin. In the coarse mode the relative contribution of ionic mass, dust and POM are 50%, 39% and 11%, respectively. In the fine mode up to 60% of the total mass is due to ionic mass and about 30% is due to POM. Factor analysis has identified three components/sources in the coarse mode namely crustal, photochemical and marine while two additional groups were discriminated in the fine mode, residual oil and secondary/combustion aerosols. In particular, natural sources (dust and sea salt) account for up to 60% of the coarse mode variance (versus 20% of the man-made sources), whereas in the fine fraction these two components have almost equal contribution (about 40%).