Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 6 2005 10.5194/acpd-5-13053-2005 http://www.atmos-chem-phys-discuss.net/5/13053/2005/ http://www.atmos-chem-phys-discuss.net/5/13053/2005/acpd-5-13053-2005.html http://www.atmos-chem-phys-discuss.net/5/13053/2005/acpd-5-13053-2005.pdf 13053 13073 2005-12-21 Ion concentrations of PM_10–2.5 and PM_2.5 aerosols over the eastern Mediterranean region: seasonal variation and source identification H. Kouyoumdjian N. A. Saliba ns30@aub.edu.lb Department of Chemistry, American University of Beirut, P.O. Box 11-0236 Riad El Solh, Beirut, 1107 2020, Lebanon The annual averages of particulate matters (PM₁₀, PM_10–2.5 (coarse) and PM_2.5 (fine)) in a densely populated area of Beirut were measured and found to be 84±27, 53±20 and 31±9 μg m^−3, respectively. Ion Chromatography (IC) analysis of the collected PM Teflon filters showed that NaCl, CaSO₄ and Ca(NO₃)₂ were predominant in the coarse particles, while (NH₄)₂SO₄ was the main salt in the fine particles. Using the non destructive Fourier Transform Infra Red-Attenuated Total Reflection (FTIR-ATR) technique, CaCO₃ was determined in the coarse filter. In addition, ATR measurements showed that inorganic salts present in the coarse particles are mostly water insoluble while salts found in fine particles are soluble. Concentrations of nitrates and calcium higher than the ones reported in neighboring Mediterranean countries were good indication of high traffic density and crustal dust abundance in Beirut, respectively. The study of the seasonal variation showed that long-range transport of SO₂ from Eastern and Central Europe, sandy storms coming from Africa and marine aerosols are considered major sources of the determined inorganic ions. Considering the importance of the health and climate impacts of aerosols locally and regionally, this study constitutes a point of reference for eastern Mediterranean transport modeling studies and local regulatory and policy makers.