Chemical composition of the fine and coarse fraction of aerosols in the northeastern Mediterranean

Two-stage aerosol samples (PM10–2.5 and PM2.5) were collected at a coastal rural site located in the northeastern Mediterranean, between April 2001 and 2002. A total of 562 aerosol samples were analyzed for trace elements (Fe, Ti, Mn, Ca, V, Ni, Zn, Cr) and water-soluble ions (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, Br−, NO3−, SO42−, C2O42− and MS−:methane sulfonate). PM10, crustal elements, sea salt aerosols and NO3− were mainly associated with the coarse mode whereas non-sea salt (nss)SO42−, C2O42−; MS−, NH4+, Cr and Ni were found predominantly in the fine fraction. Concentrations of aerosol species exhibited orders of magnitude change from day to day and the aerosol chemical composition is heavily affected by dust events under the influence of airflow from North Africa. During the sampling period, 11 specific mineral dust events of duration varying from 1 day to a week have been identified and their influence on the chemical composition of aerosols has been studied in detail. Ionic balance analysis performed in the coarse and fine aerosol fractions indicated anion and cation deficiency due to CO32− and H+, respectively. A relationship between nssSO42− and NH4+ denoted that sulfate particles were partially neutralized (70%) by ammonium. Excess-K/BC presented two distinct ratios for winter and summer, indicating two different sources: fossil fuel burning in winter and biomass burning in summer.