Influence of mineral dust transport on the chemical composition and physical properties of the Eastern Mediterranean aerosol

Bulk aerosol samples were collected from three different coastal rural sites located around the Eastern Mediterranean, (i) Erdemli (ER), Turkey, (ii) Heraklion (HR), Crete, Greece, and (iii) Tel Shikmona (TS), Israel, during two distinct mineral dust periods (October, 2007 and April, 2008) in order to explore the temporal and geographical variability in the aerosol chemical composition. Samples were analyzed for trace elements (Al, Fe, Mn, Ca, Cr, Zn, Cu, V, Ni, Cd, Pb) and water-soluble ions (Cl ^-, NO ₃ ^-, SO ₄ ^2-, C ₂O ₄ ^2-, Na ⁺, NH ₄ ⁺, K ⁺, Mg ²⁺ and Ca ²⁺). The dust events were categorized on the basis of Al concentrations >1000 ng m ^-3, SKIRON dust forecast model and 3-day back trajectories into three groups namely, Middle East, Mixed and Saharan desert. ER and TS were substantially affected by dust events originating from the Middle East, particularly in October, whilst HR was not influenced by dust transport from the Middle East. Higher AOT values were particularly associated with higher Al concentrations. Contrary to the highest Al concentration: 6300 ng m ^-3, TS showed relatively lower AI and AOT. Al concentrations at ER were similar for October and April, whilst OMI-AI and AOT values were ∼2 times higher in April. This might be attributed to the weak sensitivity of the TOMS instrument to absorbing aerosols near the ground and optical difference between Middle East and Saharan desert dusts. The lowest enhancement of anthropogenic aerosol species was observed at HR during dust events (nssSO ₄ ^2-/nssCa ²⁺ ∼ 0.13). These species were particularly enhanced when mineral dust arrived at sites after passing through populated and industrialized urban areas.