Impact of parking duration on tailpipe VOCs emissions from light-duty gasoline vehicles

Vehicle parking duration is closely related to fuel vaporization efficiency, oil temperature, and the operating temperature of the three-way catalytic converter (TWC) during restart, thereby influencing tailpipe emissions. To investigate the impact of parking duration on VOCs emissions from gasoline vehicles, this study performed chassis dynamometer tests on representative China Ⅵ light-duty gasoline vehicles under three parking conditions (t<0.5 h, 1.5 h<t<4 h, and t>6 h). Tailpipe VOCs were sampled, the components were analyzed, and their ozone formation potential (OFP) was calculated using the Maximum Incremental Reactivity (MIR) method. The results showed that as parking duration increased from under 0.5 h to over 6 h, the average VOCs emission factor increased from 10.9 mg/km to 30.6 mg/km, and the OFP rose from 26.1 mg/km to 109.4 mg/km. The proportion of highly reactive species such as olefins and aromatics also increased significantly. When parking duration exceeded 1.5 h, VOCs emitted during the first 589 s (start-up phase) accounted for over 75% of total emissions in the 1800 s test cycle, and contributed more than 85% of the total OFP. It was recommended to develop a refined VOCs emission inventory that incorporated parking duration parameters based on typical vehicle usage patterns in China, and to develop accurate emission control technologies for cold-start conditions following long parking duration.