Secondary Organic Aerosol Formation Potential from Vehicular Non-tailpipe Emissions under Real-World Driving Conditions

• Published in: Environmental science & technology Vol. 58; no. 12; pp. 5419 - 5429
• Main Authors: Zhang, Jinsheng, Peng, Jianfei, Song, Ainan, Du, Zhuofei, Guo, Jiliang, Liu, Yan, Yang, Yicheng, Wu, Lin, Wang, Ting, Song, Kai, Guo, Song, Collins, Don, Mao, Hongjun
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 26.03.2024
• Subjects: Aerosols; Aromatic compounds; Asphalt; Chemical compounds; Driving conditions; Dynamometers; Emission standards; Exhaust gases; Exhaust pipes; Fuels; Occurrence, Fate, and Transport of Contaminants in Indoor Air and Atmosphere; Oxidation; Photooxidation; Sublimation; Tunnels; Urban environments; Vehicle emissions; non-tailpipe emissions; non-exhaust; OFR; SOA; tunnel measurement; IVOCs
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.3c06475

Traffic emissions are a dominant source of secondary organic aerosol (SOA) in urban environments. Though tailpipe exhaust has drawn extensive attention, the impact of non-tailpipe emissions on atmospheric SOA has not been well studied. Here, a closure study was performed combining urban tunnel experiments and dynamometer tests using an oxidation flow reactor in situ photo-oxidation. Results show a significant gap between field and laboratory research; the average SOA formation potential from real-world fleet is 639 ± 156 mg kg fuel–1, higher than the reconstructed result (188 mg kg fuel–1) based on dynamometer tests coupled with fleet composition inside the tunnel. Considering the minimal variation of SOA/CO in emission standards, we also reconstruct CO and find the critical role of high-emitting events in the real-world SOA burden. Different profiles of organic gases are detected inside the tunnel than tailpipe exhaust, such as more abundant C6–C9 aromatics, C11–C16 species, and benzothiazoles, denoting contributions from non-tailpipe emissions to SOA formation. Using these surrogate chemical compounds, we roughly estimate that high-emitting, evaporative emission, and asphalt-related and tire sublimation share 14, 20, and 10% of the SOA budget, respectively, partially explaining the gap between field and laboratory research. These experimental results highlight the importance of non-tailpipe emissions to atmospheric SOA.