10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

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Using a Mobile Laboratory Equipped with an Oxidative Flow Reactor to Study Oxidative Aging of In-use Motor Vehicle Emissions

KEREN LIAO, Qi Chen, Yan Zheng, Ying Liu, Tong Zhu, Peking University

     Abstract Number: 653
     Working Group: Oxidation Flow Reactor: Development, Characterization, and Application to Aerosols

Abstract
Vehicle emissions in megacities like Beijing contribute a large amount of gaseous precursors that can form secondary organic aerosol (SOA) via atmospheric oxidation. The contribution of SOA formation from vehicle exhaust to ambient particulate matter concentrations however remains unclear. Most of the current chemical transport models are unable to reproduce the magnitude and the variability of SOA mass in urban regions, suggesting large uncertainties in the emission inventories and/or in the SOA formation mechanism. For the transportation sector, it is important to investigate the SOA formation under actual driving conditions of traffic fleets which has not been studied before in China. We therefore deployed a Potential Aerosol Mass (PAM) flow reactor in a mobile laboratory to investigate the in situ SOA formation from in-use motor vehicle emissions on the major roads in Beijing in 2018. Vehicle exhaust is sampled and delivered into the PAM reactor periodically. The hydroxyl radical exposure in the PAM reactor is cycled from ~ 1 to 10 days of equivalent atmospheric oxidation. Concentrations of traffic-related gaseous precursors and some oxidation products are measured by gas analyzers and a proton transfer reaction mass spectrometer. Chemical composition of fine particles is measured by a time-of-flight aerosol chemical speciation monitor equipped with 2.5-µm lens and a capture vaporizer. The observations are discussed on the basis of the source apportionments of ambient particles from a long-term site. Potential contribution of mobile sources to fine-particle concentrations is estimated.