VOCs evaporative emissions from vehicles in China:Species characteristics of different emission processes

Vehicle evaporation is an essential source of VOCs in cities but is not well understood in China.Reported emission factors from previous studies are not enough for understanding the atmospheric chemical process of vehicular evaporative VOCs.In this work,a serious of detailed VOCs speciation profiles are developed based on test processes and emission processes.A mass balance method was used to divide different emission processes during diurnal tests.The results show that headspace vapor of gasoline cannot represent the real-world vehicle evaporation because of the significant differences in VOCs speciation profiles,especially for aromatics.To further distinguish emissions from evaporation and exhaust,only the ratios of MTBE/benzene and MTBE/toluene can serve as indicators when considering species from all evaporative processes.Besides,emissions from different sources change significantly with the seasons.To solve these problems,we developed a monthly comprehensive evaporation speciation profile.The individual profiles at the emission processes are weighted by the emission of the in-use vehicle fleet in Beijing to derive the comprehensive speciation profile of evaporative VOCs.Ozone formation potential(OFP)and secondary organic aerosol potential(SOAP)were used to evaluate the environmental impact.For SOAP,100 g evaporative emissions are equal to 6.05-12.71 g toluene in different months,much higher than that given using headspace vapors,especially in winter(7.2 times higher in December).These findings would improve our understanding of the evaporative VOCs emissions in China and their environmental impacts(e.g.,O3 and SOA formation).

Vehicular volatile organic compounds losses due to refueling and diurnal process in China: 2010–2050

Volatile organic compounds（VOCs） are crucial to control air pollution in major Chinese cities since VOCs are the dominant factor influencing ambient ozone level, and also an important precursor of secondary organic aerosols. Vehicular evaporative emissions have become a major and growing source of VOC emissions in China. This study consists of lab tests, technology evaluation, emissions modeling, policy projections and cost-benefit analysis to draw a roadmap for China for controlling vehicular evaporative emissions. The analysis suggests that evaporative VOC emissions from China＇s light-duty gasoline vehicles were approximately 185,000 ton in 2010 and would peak at 1,200,000 ton in 2040 without control. The current control strategy implemented in China, as shown in business as usual（BAU） scenario, will barely reduce the long-term growth in emissions. Even if Stage II gasoline station vapor control policies were extended national wide（BAU ＋ extended Stage II）, there would still be over 400,000 ton fuel loss in 2050. In contrast, the implementation of on-board refueling vapor recovery（ORVR） on new cars could reduce 97.5% of evaporative VOCs by 2050（BAU ＋ ORVR/BAU ＋ delayed ORVR）. According to the results, a combined Stage II and ORVR program is a comprehensive solution that provides both short-term and long-term benefits. The net cost to achieve the optimal total evaporative VOC control is approximately 62 billion CNY in 2025 and 149 billion CNY in 2050.