Contribution of volatile components in exhaust to nanoparticles emission from urban vehicles

The evolution process of particulate matter in vehicle exhaust is still highly controversial, which restricts the traceability of atmospheric particulate matter and hinders the implementation of emission reduction policies. This study analyzes the volatilization characteristics of polydisperse and monodisperses particles in the exhaust of vehicles, through tunnel experiments and vehicle bench tests. In the tunnel, the number of particles (PN) emitted by the fleet increased by 52.8 % from when it was generated in the engine to when it entered the atmosphere, while the particle mass (PM) increased by a factor of 5.8. For gasoline vehicles, during the cooling process, the total PN more than doubled, whereas the total PM increased by approximately five times. In diesel engine exhaust, PN increased by 123 %, and PM increased by 70.3 %. Specifically, for gasoline vehicles, 60.5 % of 20 nm particulate matter is generated during the emission process, while 39.4 % of 100 nm particulate matter is produced. During the emission process of diesel vehicles, 43.6 % of 20 nm particulate matter and 19.1 % of 100 nm particulate matter are generated. Additionally, highly volatile components in exhaust contribute more to PN and PM than other components. Among the particulate matter emitted by gasoline vehicles, highly volatile components account for approximately 52.1 % of the number of volatile particulate matter and about 63.0 % of the mass increase. In contrast, for diesel vehicles, the contribution of highly volatile components to the number of volatile particles is approximately 54.5 %, while their contribution to the mass increase is around 37.5 %. • The volatility of particle in vehicle exhaust was studied by tunnel test and vehicle bench test. • Smaller particle sizes were associated with a higher proportion of volatile particles. • High-volatile components contribute the most to particle number and mass.