title: Dust episodes in Beirut and their effect on the chemical composition of coarse and fine particulate matter.
abstract: Particles captured during dust episodes in Beirut originated from both the African and Arabian deserts. This particular air mixture showed an increase, over non-dust episodes, in particle volume distribution which was mostly noticed for particles ranging in sizes between 2.25 and 5 μm. It also resulted in an increase in average mass concentration by 48.5% and 14.6%, for the coarse and fine fractions, respectively. Chemical analysis of major aerosol components accounted for 93% of fine PM and 71% of coarse PM. Crustal material (CM) dominated the coarse PM fraction, contributing to 39 ± 15% of the total mass. Sea salt (SS) (11 ± 10%) and secondary ions (SI) (11 ± 7%) were the second most abundant elements. In the fine fraction, SI (36 ± 14%) were the most abundant PM constituent, followed by organic matter (OM) (33 ± 7%) and CM (13 ± 2%). Enrichment factors (EF) and correlation coefficients show that biogenic and anthropogenic sources contribute to the elemental composition of particles during dust episodes. This study emphasizes on the role played by the long-range transport of aerosols in changing the chemical composition of the organic and inorganic constituents of urban coarse and fine PM. The chemical reactions between aged urban and dust aerosols are enhanced during transport, leading to the formation of organo-nitrogenated and -sulfonated compounds. Their oligomeric morphologies are further confirmed by SEM-EDX measurements.
authors: American University of Beirut, Department of Chemistry, Beirut, Lebanon.
authors: Malek
authors: M
authors: Jaafar
authors: American University of Beirut, Department of Chemistry, Beirut, Lebanon.
authors: Rima
authors: R
authors: Baalbaki
authors: American University of Beirut, Department of Chemistry, Beirut, Lebanon; Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral-Côte d'Opale, France.
authors: Raya
authors: R
authors: Mrad
authors: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
authors: Nancy
authors: N
authors: Daher
authors: American University of Beirut, Department of Mechanical Engineering, Beirut, Lebanon.
authors: Alan
authors: A
authors: Shihadeh
authors: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
authors: Constantinos
authors: C
authors: Sioutas
authors: American University of Beirut, Department of Chemistry, Beirut, Lebanon. Electronic address: ns30@aub.edu.lb.
authors: Najat A
authors: NA
authors: Saliba
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D004391:Dust / Q000032:analysis*; D004784:Environmental Monitoring; D007861:Lebanon
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D004391:Dust
keywords: Beirut; Dust episodes; Eastern Mediterranean city; Organosulfates and organonitrates; PM mass closure; Particle volume distribution