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 OVOCs had a rebound trend at the highest speeds due to the four-center reaction of alcohol and the oxidation of aromatics. Compared to evaporative VOC emissions measured with the same instrument, VOCs from tailpipe emissions have exhibited distinct features in the relative ratios among benzene, toluene, and ethylbenzene. In addition, OVOCs are becoming more important in terms of ozone formation potential for gasoline vehicle exhausts. Alkenes in high-cumulative mileage vehicles may also contribute significantly to ozone formation. This study enables a more comprehensive and accurate understanding of VOC emissions from vehicle exhausts and would be beneficial for mitigating urban O 3 pollution. [Display omitted] • The tailpipe VOC emissions under different factors were comprehensively and systematically investigated. • The proportion of OVOCs increased with the upgrading of emission standards. • Ethanol-containing gasoline could help to reduce the total VOC emissions but emit more OVOCs. • The cold-start condition has the highest VOC emissions. [ABSTRACT FROM AUTHOR]