Emission characteristics and ozone formation potentials of VOCs from gasoline passenger cars at different driving modes

Vehicle emissions have adverse health effects and are major source of ozone precursors in urban environments. In this study, the emission factors (EFs) of nitrogen oxides (NOx) and eight high abundant volatile organic compounds (VOCs) including propene, 1,3-butadiene, 1-butene, benzene, 1-hexene, toluene, xylene, and trimethylbenzene from gasoline-fuel passenger cars were investigated at four typical driving modes using a chassis dynamometer method combined with the online ion molecule reaction mass spectrometer (IMR-MS), and ozone formation potentials (OFPs) of VOCs were further evaluated. Measured concentrations of NOx and VOCs markedly varied with vehicles and driving speeds. Change trends of NOx EFs and VOC EFs were opposite with varying driving speeds. The EFs of NOx had wide inter-vehicle variations and increased with driving speeds. The EFs of individual VOCs were markedly different at same driving mode and notably varied with driving modes, and the average EF of total VOCs at low speed mode (30 km/h) was the largest among the driving modes. The OFPs of individual VOC varied with different vehicles, different VOC species and driving modes, and the driving mode of 30 km/h had the largest total OFPs among the driving modes. The findings obtained in this study can provide valuable insight into to mitigating air pollution caused by vehicles in urban areas.