Mass spectrometric study of secondary organic aerosol formed from the photo-oxidation of aromatic hydrocarbons |
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| Authors: | Kei Sato Akinori Takami Tasuku Isozaki Toshihide Hikida Akio Shimono Takashi Imamura |
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| Institution: | 1. National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan;2. Sanyu Plant Service Co., Ltd., 1-8-21 Hashimotodai, Sagamihara, Kanagawa 229-1132, Japan;1. Nagoya City Institute for Environmental Sciences, Nagoya, Japan;2. Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan;3. Faculty of Environmental Science and Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Japan;1. Department of Civil Engineering, Indian Institute of Technology, Kanpur, India;2. Centre of Environmental Science and Engineering, CESE, IIT Kanpur, India;1. Institute of Chemical Process Fundamentals, CAS, v.v.i., Rozvojová 135, Prague 6, Czech Republic;2. Institute for Environmental Studies, Faculty of Science, Charles University in Prague, Benátská 2, 12801 Prague 2, Czech Republic;1. State 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;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China;4. School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, China;5. Institut de Recherches sur la Catalyse et l''Environment de Lyon (IRCELYON), CNRS, UMR5256, Villeurbanne F-69626, France;1. State Key Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China;2. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | From measurements by an Aerodyne Aerosol Mass Spectrometer (AMS), secondary organic aerosol (SOA) formed in laboratory chambers is believed to be less oxidized than well-oxidized ambient organic aerosol (OA). However, the mass spectrum of SOA formed from the photo-oxidation of aromatic hydrocarbons has not been sufficiently studied by using AMS though these reactions are potential sources of urban SOA. In this study, we studied SOA formed from the photo-oxidation of seven aromatic hydrocarbons by using Time-of-Flight AMS. Strong mass signals from SOA were found at m/z 43 (m43) and 44 (m44) in all the experiments. The m44 to total organic aerosol mass ratio (m44/OA) increased with irradiation time. For example, the m44/OA ratio increased from 10.6% to 13.3% during irradiation for 11 h in an experiment with toluene. The average m44/OA ratios were determined to be 5.8–17.1% for all the experiments. The m44/OA decreased and the m43/OA increased with increasing number of alkyl substituents of precursor aromatic hydrocarbons. This is because low-reactive ketones are preferentially produced rather than aldehydes with increasing number of alkyl substituents. The m44/OA ratios of the benzene and monoalkylbenzene oxidation were 12.2–17.1% and were close to those of well-oxidized ambient OA. These findings are consistent with the hypothesis that the photo-oxidation of aromatic hydrocarbons is a potential source of urban SOA. In addition to oxygenated organic compounds, organic nitrogen oxides were also shown to be present in SOA by high-resolution mass spectra. |
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