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Particulate matter with size less than or equal to 2.5 μm (PM 2.5 ) samples were collected from an urban site Pune, India, during April 2015 to April 2016. The samples were analyzed for various chemical constituents, including water soluble inorganic ions, organic carbon (OC), and elemental carbon (EC). The yearly mean total mass concentration of PM 2.5 at Pune was 37.3 μg/m 3 , which is almost four times higher than the annual WHO standard (10 μg/m 3 ), and almost equal to that recommended by the Central Pollution Control Board, India (40 μg/m 3 ). Measured (OC, EC) and estimated organic matter (OM) were the dominant component (56 ± 11%) in the total particulate matter which play major role in the regional atmospheric chemistry. Total measured inorganic components formed about 35% of PM 2.5 . Major chemical contributors to PM 2.5 mass were OC (30%), SO 4 2- (13%), and Cl - and EC (9% each). The high ratios of OC/EC demonstrated the existence of secondary organic carbon. The air mass origin and correlations between the various components indicate that long range transport of pollutants from Indo-Gangetic Plain (IGP) and Southern part of the Arabian Peninsula might have contributed to the high aerosol mass during the dry and winter seasons. To our knowledge, this is the first systematic study that comprehensively explores the chemical characterization and source apportionment of PM 2.5 aerosol speciation in Pune by applying multiple approaches based on a seasonal perspective. This study is broadly applicable to understanding the differences in anthropogenic and natural sources in the urban environment of particle air pollution over this region.