Knowledge of both the size distribution and elemental composition of different size fractions of aerosol particles is useful not only in providing information about the chemical composition and source apportionment of pollutants, but also in understanding the transformation chemistry of pollutants during transport in the atmosphere. We have used a low pressure-multistage inertial impactor and a double stage low volume sampler for particulate matter with aerodynamic diameter between 10 m, and 2.5 m respectively (PM10 and PM2.5) to collect both indoor and outdoor samples. We have integrated various spectroscopic techniques to obtain complementary information about the composition of various size fractions of pollutants, their transformation and their possible sources. Our results show that the coarse fraction of PM is mainly due to natural sources such as dust storms crustal matter and seas salts, while the fine and ultrafine fractions of PM matter contains compounds created through reactions of the natural coarse pollutants with anthropogenic emissions such as sulfur dioxide (SO2) and nitrogen oxides (NOx), during transport in the atmosphere. The major phase of such new compounds was ammonium sulfate.