Excess vehicular evaporative emissions for prolonged parking during the COVID-19 lockdown in China

Vehicular evaporative emissions are major sources of urban volatile organic compounds (VOCs), significantly contributing to secondary organic aerosols (SOA) and ozone (O₃) formation. While most anthropogenic emissions declined during the COVID-19 lockdowns, the potential rise in evaporative emissions has been largely overlooked. Here, we integrate emission tests, parking data, and field measurements to assess excess evaporative emissions in China. Long-term experiments reveal that prolonged parking vehicles (> 5 days) experience up to an 18-fold increase in evaporative emissions compared to the first day. During the lockdown, prolonged parking events surged dramatically, driving a substantial increase in evaporative emissions, strongly corroborated by VOC source apportionment analysis. We estimate that annual evaporative emissions across 36 Chinese megacities rose by up to 2.8-fold due to lockdown measures. These findings highlight prolonged parking as a critical yet underrecognized VOC source, emphasizing the need for improved regulatory control to mitigate urban air pollution.