1State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
2CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640, China
3Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
4University of Chinese Academy of Sciences, Beijing 100049, China
5Guangzhou Ecological and Environmental Monitoring Center of Guangdong Province, Guangzhou 510060, China
6Guangzhou Environmental Technology Center, Guangzhou 510180, China
7Guangzhou Tunnel Development Company, Guangzhou 510133, China
1State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
2CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640, China
3Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
4University of Chinese Academy of Sciences, Beijing 100049, China
5Guangzhou Ecological and Environmental Monitoring Center of Guangdong Province, Guangzhou 510060, China
6Guangzhou Environmental Technology Center, Guangzhou 510180, China
7Guangzhou Tunnel Development Company, Guangzhou 510133, China
Received: 09 Mar 2021 – Accepted for review: 24 Mar 2021 – Discussion started: 26 Mar 2021
Abstract. Intermediate-volatility organic compounds (IVOCs) emitted from vehicles are important precursors to secondary organic aerosols (SOA) in urban areas, yet vehicular emission of IVOCs, particularly from on-road fleets, is poorly understood. Here we initiated a field campaign to collect IVOCs with sorption tubes at both the inlet and the outlet in a busy urban tunnel (>30,000 vehicles per day) in south China for characterizing emissions of IVOCs from on-road vehicles. The average emission factor of IVOCs (EFIVOCs) was measured to be 16.77 ± 0.89 mg km-1 (Average ± 95% C.I.) for diesel and gasoline vehicles in the fleets, and based on linear regression the average EFIVOCs was derived to be 62.79 ± 18.37 mg km-1 for diesel vehicles and 13.95 ± 1.13 mg km-1 for gasoline vehicles. The EFIVOCs for diesel vehicles from this study was comparable to that reported previously for non-road engines without after-treatment facilities, while the EFIVOCs for gasoline vehicles from this study was much higher than that recently tested for a China V gasoline vehicle. IVOCs from the on-road fleets did not show significant correlation with the primary organic aerosol (POA) or total non-methane hydrocarbons (NMHCs) as results from previous chassis dynamometer tests. Estimated SOA production from the vehicular IVOCs and VOCs surpassed the POA by a factor of ~ 2.4, and IVOCs dominated over VOCs in estimated SOA production by a factor of ~ 7, suggesting that controlling IVOCs is of greater importance to modulate traffic-related OA in urban areas. The results demonstrated that although on-road gasoline vehicles have much lower EFIVOCs, they contribute more IVOCs than on-road diesel vehicles due to its dominance in the on-road fleets. However, due to greater diesel than gasoline fuel consumption in China, emission of IVOCs from diesel engines would be much larger than that from gasoline engines, signaling the overwhelming contribution of IVOC emissions by non-road diesel engines in China.
A tunnel test was initiated to measure the vehicular IVOCs emissions under real-world driving conditions. Higher SOA formations estimated from vehicular IVOCs than that from traditional VOCs emphasized the greater importance of IVOCs in modulating urban SOA. The results also revealed that non-road diesel-fueled engines greatly contributed to IVOCs in China.
A tunnel test was initiated to measure the vehicular IVOCs emissions under real-world driving...