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The PM 10 and particles of greater than 10 µm aerodynamic diameter (hence forth referred as PM >10 ) collected over Delhi exceeded the National Ambient Air Quality Standards (100 µg m -3 ) with an annual average of 215 µg m -3 and 495 µg m -3 , respectively. The water soluble inorganic ions (WSII) were higher throughout the year in PM 10 (13.5%) than in PM >10 (5%). SO 4 2-dominated over NO 3 -ions and contributed 54% to the total WSII in PM 10 . NO 3 -and Ca 2+ were dominant ions in PM >10 . NH 4 + during winter and autumn, and Ca 2+ in summer PM 10 samples were the major acid neutralizing species. The WSII showed monthly and seasonal changes. The total carbon (TC = EC + OC) constituted 8.8%-47.8% of total PM 10 mass, and OC and EC varied from 9.91 to 37.06 µg m -3 and 5.42 to 22.23 µg m -3 during the year long sampling period. The SOC contributed more to OC in summers and the char (EC1) dominated over soot (EC2 + EC3) in EC fractions throughout the year. In summer samples, secondary OC (SOC) contributed 81% to OC and the OC/EC ratio was 3.61 suggesting the possible role of mineral dust and high photochemical activity in SOC production. For the eight different fractions, three dominant sources were identified, coal combustion, biomass burning, and motor vehicle exhaust for OC1, OC2 and OC3; vehicle exhaust for OC4, OP, EC2 and EC3; and biomass and coal combustion for EC1. The seasonal changes in the WSII and carbon concentrations in PM 10 and PM >10 are attributed to both the sources and the meteorological conditions in and around the study area.