Chemical concentrations and elements size distributions of aerosols in the eastern Mediterranean during strong dust storms

In 1993 three strong dust episodes occurred in the Eastern Mediterranean Basin during the rainy season September and October. During dust episodes, and at normal conditions in order to compare dust and non-dust period, daily PM-10 aerosol samples and weekly six stage size separated aerosol samples were collected at Antalya, an eastern Mediterranean location. Both PM-10 and impactor samples were analysed for 40 elements by instrumental neutron activation analysis. Wind trajectories were examined and the dust episodes classified according to their patterns into two types: (a) Saharan Dust episodes, and (b) Middle East Dust episodes. Among the three studied dust episodes, similar chemical composition were found for Saharan dust and Middle Eastern dust episodes. Although similar absolute concentrations of anthropogenic elements were observed during dust and non-dust periods, for crustal elements like Al, Sc, Fe, and rare earth elements concentrations during strong dust periods up to a factor of four higher concentrations were measured. According to the enrichment factor results three broad groups were identified; group I: no size dependency, no enrichment: Sc-like elements (rare-earth's, Mn, Fe, Ti, Sc), group II EFc's increase with particle size (Na, Cl, Mg), and group III EFc's decrease with particle size (As, Se, Sb, Cd, Zn).