Particulate Number Emissions from Road Traffic under Different Driving Condition

Vehicle particle number emission factor is considered by the latest coming EU6 regulation, for this reason, we study the vehicle particle number emission and its characterization in the real word under varying driving conditions. Emission factors are estimated based on the long-term field measurement data from both background and kerbsides stations near highway and urban street. The results show that the particle number emission factors of average fleet for highway and urban street is (215.4 +/- 5.3) 1012 km -1 and (187.1 +/- 3.1) 1012 km-1, respectively. NOx emission factor of average fleet is 1.41 g km-1 and 0.94 g km-1 for highway and urban street. Emission factors of heavy-duty and light-duty vehicle are also estimated. The ratio of heavy-duty vehicle to that of light-duty vehicle is around 20, both higher at urban site than them at highway site. Bi-dominating modes of particle number concentration appears at both sites, a 10 nm mode at highway site, a 20-30 nm mode at urban site and a common 50-80 nm mode at both sites. Particle number emission factors vary with size, which is at the range of 100 X 1012 km-1 to 1000 X 1012 km-1 for ale particles less than 100 nm in diameter, at the range of 100 X 1012 km-1 to 0.1 X 1012 km-1 for the particles larger than 100 nm in diameter. The uncertainty of estimating the emission factor caused by vehicle count of different types is also discussed in the paper.