Using highly time-resolved online mass spectrometry to examine biogenic and anthropogenic contributions to organic aerosol in Beijing

Mehra, Archit and Canagaratna, Manjula and Bannan, Thomas J. and Worrall, Stephen D. and Bacak, Asan and Priestley, Michael and Liu, Dantong and Zhao, Jian and Xi, Weiqi and Sun, Yele and Hamilton, Jacqueline F. and Squires, Freya and Lee, James and Bryant, Daniel J. and Hopkins, James R. and Elzein, Atallah and Budisulistiorini, Sri Hapsari and Cheng, Xi and Chen, Qi and Wang, Yuwei and Wang, Lin and Stark, Harald and Krechmer, Jordan E. and Brean, James and Slater, Eloise and Whalley, Lisa and Heard, Dwayne and Ouyang, Bin and Acton, Joe and Hewitt, C N and Wang, Xinming and Fu, Pingqing and Jayne, John and Worsnop, Douglas R. and Allan, James and Percival, Carl J. and Coe, Hugh (2021) Using highly time-resolved online mass spectrometry to examine biogenic and anthropogenic contributions to organic aerosol in Beijing. Faraday Discussions, 226. pp. 382-408. ISSN 1359-6640

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Organic aerosols, a major constituent of fine particulate mass in megacities, can be directly emitted or formed from secondary processing of biogenic and anthropogenic volatile organic compound emissions. The complexity of volatile organic compound emission sources, speciation and oxidation pathways leads to uncertainties in the key sources and chemistry leading to formation of organic aerosol in urban areas. Historically, online measurements of organic aerosol composition have been unable to resolve specific markers of volatile organic compound oxidation, while offline analysis of markers focus on a small proportion of organic aerosol and lack the time resolution to carry out detailed statistical analysis required to study the dynamic changes in aerosol sources and chemistry. Here we use data collected as part of the joint UK–China Air Pollution and Human Health (APHH-Beijing) collaboration during a field campaign in urban Beijing in the summer of 2017 alongside laboratory measurements of secondary organic aerosol from oxidation of key aromatic precursors (1,3,5-trimethyl benzene, 1,2,4-trimethyl benzene, propyl benzene, isopropyl benzene and 1-methyl naphthalene) to study the anthropogenic and biogenic contributions to organic aerosol. For the first time in Beijing, this study applies positive matrix factorisation to online measurements of organic aerosol composition from a time-of-flight iodide chemical ionisation mass spectrometer fitted with a filter inlet for gases and aerosols (FIGAEROToF-I-CIMS). This approach identifies the real-time variations in sources and oxidation processes influencing aerosol composition at a near-molecular level. We identify eight factors with distinct temporal variability, highlighting episodic differences in OA composition attributed to regional influences and in situ formation. These have average carbon numbers ranging from C5–C9 and can be associated with oxidation of anthropogenic aromatic hydrocarbons alongside biogenic emissions of isoprene, apinene and sesquiterpenes.

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Journal Article
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Faraday Discussions
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07 Dec 2020 15:50
Last Modified:
16 Sep 2023 02:14