A new monitoring-simulation-source apportionment approach for investigating the vehicular emission contribution to the PM2.5 pollution in Beijing, China

In this study, a new approach combining the environment monitoring, model simulation and source apportionment methods was proposed to investigate the impact of vehicular emissions on the PM2.5 pollution. The method can identify the contributions of various emission sources to both the primary and secondary particles. A case application was conducted in Beijing, China. An intensive monitoring covering the period of December 2010 to January 2012 was conducted to obtain the detailed chemical components proportions in the total PM2.5. The vehicular emission contributions (VECs) to primary organic aerosols (POA), element carbon (EC), SO2, NOX, NH3, elements and VOC were estimated based on the MM5-CMAQ simulation, factor analysis and references investigation. The VECs to different components and to the total PM2.5 were then calculated. Results showed that there was no clear difference in the total VECs of different seasons. The annual average contribution ratio was approximately 22.5 ± 3.5%. Among all the chemical species, nitrate and SOA accounted for the highest contribution percentages. In addition, the influence of road dust on the PM2.5 pollution was also simulated using the MM5-CMAQ modeling system. It is indicated that the road dust contributed approximately 4.9 ± 1.3% of the total PM2.5 on an annual average. Considering both the contributions from motor vehicles and road dust emissions, the annual average direct contributions from road transport to the PM2.5 in Beijing was approximately 27.4 ± 4.8%.