Review on Particulate emission in diesel engines. Characterization of particulate matter emissions Particulate matter emitted from diesel engine consist of both volatile and non volatile fraction. Kleeman et al after analyzing the motor vehicle emissions concluded the composition of organic and elemental carbon, dependent on the size of particle emitted[42]. Ion nucleation was not found to be a major mechanism in diesel engine exhaust[10]. Since the nucleation mode particles are formed from condenstion of volatile hc and sulfuric acid [kittelson 2006],[42] shell like structure is formed[1] Kwon et al and Sakurai et al. reported large volatile fraction in smaller sized particles using TDMA [42]. Kwon et al further reported the decreae in volatile fraction with particle size in small size particles and Park et al. also reported decrease in effective density of particle with particle size with mobility size. Diesel engine emissions consist of BCs and HC where solid core is formed by BC and multiring PAH[2]. [4] showed that increase in sulphur generally increased the smaller sized particles but not always. He reported about 97% of the volume of 12nm to 30nm particles of C24-C32 n alkanes based on the voltality. [15] also reported decrease nucleation rates when ULSD was used while [18],[19],[4] added dilution condtion as the contributing factors. Accumulation mode was found passive to dilution condtions. Soot particles- [6],[8]observed the core shell structure as well as