2017 Volume 52 Issue 1 Pages 1-11
We discuss the issues about automobile related aerosols and the condensation dust in combustion sources. Measurements in a traffic intersection showed the long-term trend of a decreasing of PM2.5 due to the tightening of emission controls, while the number concentration did not. The spatial distribution of the particle number was also measured around the traffic intersection. It suggested that nanoparticles had a very short life which depended on the temperature and particle size. Due to cleaner diesel exhausts, soot generation from the direct ignition gasoline vehicle, generated secondary organic aerosols (SOAs) from exhausts, and generation of transition metals from non-combustion sources may be more important in the future.
The condensation dust included semi-volatile organic material, which is a candidate of the missing source of primary OAs as well as precursors of SOA. The emission factor of the condensation dust is changeable because it depends on the temperature and concentrations of the co-generated particulate matter. To prevent this problem, the new methodology of volatility distribution was used to indicate the emission factor of the condensation dust. To improve the PM2.5 prediction in the air quality model, development of a measurement method of the volatility distribution and the accumulation of data of various types of emission sources are needed.
