Airborne particulate matter (PM) in an urban atmosphere is a result of contribution from diverse range of source including domestic, industry and vehicles. PM emission is a matter a concern due to its multiple impacts on public health, air quality, and global climate. Ever increasing number of vehicles plying on the road is considered to be one of the major sources of PM. Particles in gasoline and diesel vehicle exhaust carry distinctive combinations of certain chemical compounds. Prominence of their chemical signature in ambient particulate matter can be considered as a direct indication of their relative importance as sources of emissions.
In this study, Chemical speciation data of vehicle exhaust PM is analyzed and vehicle category wise distribution of carbon fractions is presented for different engine technologies and fuel types. Thermal/Optical Carbon Analysis technique, which based on the preferential oxidation of organic carbon (OC) and elemental carbon (EC) at different temperatures, is utilized for analysis of exhaust particulate matter. Carbon fractions, based on temperature, like OC1, OC2, OC3, OC4 and EC1, EC2 and EC3 are separately analyzed. OC was found to vary from 48 to 57 % amongst the composite of different category gasoline vehicles. Similarly, EC was varied from 3% to 13%. OC and EC in composite of all gasoline vehicles was 52% and 6.6% respectively. Category wise composites for diesel vehicles show variation in OC from 46 % to 52% and in EC from 16% to 25%. All diesel vehicles composite shows OC and EC % as 49% and 22% respectively.
Important and inherent differences in the carbon fractions of the particulate matter emissions from various categories of vehicles were observed. This information on the temperature differentiated carbon fractions can be utilized for designing of PM emissions reduction methodology through optimization of internal or external measures.