Long range transport of dust originating from Arabian and African Deserts causes the transformations in the morphology and chemical composition of aerosols. Changes result from physical and chemical reactions occurring in the bulk or at the surface of single particles. Being an urban Mediterranean city, Beirut is subject to dust outbreaks from two desert sources between fall and summer seasons and hence, presents a typical case study of urban mixing with dust aerosols. In this study, particles collected during dust-rich episodes help to elucidate the different sources of long range transported aerosols. Elemental composition when coupled with specific morphological structures of single particles serves as markers to differentiate between these sources. (C) 2013 Elsevier Ltd. All rights reserved.