Ambient fine aerosols and its sources were evaluated in an eastern Indian mega city, Kolkata, (KOL) in South Asia during September 2010 to August 2011. A submicron aerosol sampler (SAS) with two stage stacked filter units (SFU) was devised for simultaneous but discrete collection of water-soluble inorganic ions (WSII) and carbonaceous aerosols (CA, elemental carbon (EC) and organic carbon (OC)). Characteristics of WSII and CA were carried out using Ion Chromatography and OC-EC analyzer adopting Interagency Monitoring of PROtected Visual Environments (IMPROVE-A) protocol, respectively. Annual mean concentrations of WSII showed a relative predominance of cations (anions) consisting of Ca2+, Mg2+, and Na+ (Cl-, NO3- and SO42-), with secondary aerosols (NH4+, NO3-, and SO42-) and Ca2+ each constituting 25% and 30% respectively, of the total WSII (TWSII). The highest monthly mean concentration of SO42- and NO3- were observed respectively during the winter month of February and summer months of March and May. Pronounced peak in monthly mean of non-sea salt-K+ (nss-K+) concentration was noticed during October and April months implying the strong influence of biomass burning emissions in these months. Among the sea salt (SS), anthropogenic (AN) and dust (DT) sources of the TWSII, a relatively predominant contribution of DT in August and of AN in November, April and May was inferred. The annual mean concentration of OC was three times higher than EC with 43% of it being secondary OC. While the major sources of OC were inferred to be the paved dust, coal combustion, and biomass burning, these of EC were industrial/motor-vehicle emissions, coal combustion, and motor vehicle exhaust.