Tailpipe volatile organic compounds (VOCs) emissions from Chinese gasoline vehicles under different vehicle standards, fuel types, and driving conditions

Volatile organic compounds (VOCs) from vehicular exhaust are the key precursors of ozone formation in urban areas. However, few studies have comprehensively investigated the diverse factors affecting VOC emissions from motor vehicles. This study performed emission tests on a chassis dynamometer with 15 motor vehicles, covering China IV to China VI standards, using compressed natural gas (CNG), E10, and E0 fuels and under different driving conditions. Results showed that the average VOC emission factors (EFs) were 98.8 +/- 34.8 mg km-1, 55.8 +/- 13.4 mg km-1, 19.5 +/- 2.4 mg km-1 for China IV, China V, and China VI vehicles respectively, with an increasing proportion of oxygenated volatile organic compounds (OVOCs) with the upgrading of emission standards. Alkanes were the dominant component of VOCs emitted from natural gas vehicles, accounting for 84.5%-87.0% of the total VOC emissions; ethanol-containing gasoline reduced the VOC EFs by 16.8% but emitted more OVOCs. Driving conditions exhibited significant impacts on both EFs and VOC compositions. Notably, aromatics emissions decreased continuously with the increasing driving speeds, while alkenes and