Formation of organic tracers for isoprene SOA under acidic conditions |
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| Authors: | Mohammed Jaoui Eric W Corse Michael Lewandowski John H Offenberg Tadeusz E Kleindienst Edward O Edney |
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| Institution: | 1. Alion Science and Technology, P.O. Box 12313, Research Triangle Park, NC 27709, USA;2. National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA;1. Key Laboratory of Regional Climate-Environment for Temperate East Asia (RCE-TEA), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), Beijing, China;2. Fujian Meteorological Science Institute, Fuzhou, China;3. Key Laboratory of Aerosol, Institute of Earth Environment, Chinese Academy of Sciences, Xi''an, China;4. South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou, China;1. Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China;2. Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, 361021, China;3. University of Chinese Academy of Sciences, Beijing, 100049, China;4. Xiamen Institute of Environmental Science, Xiamen, 361021, China;1. College of Geographical Sciences, Inner Mongolia Normal University, Hohhot, 010022, China;2. Inner Mongolia Repair Engineering Laboratory of Wetland Eco-environment System, Inner Mongolia Normal University, Hohhot, 010022, China;3. Ecology and Environment Monitoring Center Station of Inner Mongolia, Hohhot, 010011, China;4. Hohhot Ecology and Environment Monitoring Branch Station of Inner Mongolia, Hohhot, 010030, China;5. Products Quality Inspection and Research Institute of Inner Mongolia, Hohhot, 010070, China |
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| Abstract: | The chemical compositions of a series of secondary organic aerosol (SOA) samples, formed by irradiating mixtures of isoprene and NO in a smog chamber in the absence or presence of acidic aerosols, were analyzed using derivatization-based GC–MS methods. In addition to the known isoprene photooxidation products 2-methylglyceric acid, 2-methylthreitol, and 2-methylerythritol, three other peaks of note were detected: one of these was consistent with a silylated-derivative of sulfuric acid, while the remaining two were other oxidized organic compounds detected only when acidic aerosol was present. These two oxidation products were also detected in field samples, and their presence was found to be dependent on both the apparent degree of aerosol acidity as well as the availability of isoprene aerosol. The average concentrations of the sum of these two compounds in the ambient PM2.5 samples ranged from below the GC–MS detection limit during periods when the isoprene emission rate or apparent acidity were low to approximately 200 ng m?3 (calibrations being based on a surrogate compound) during periods of high isoprene emissions. These compounds presently unidentified have the potential to serve as organic tracers of isoprene SOA formed exclusively in the presence of acidic aerosol and may also be useful in assessments in determining the importance and impact of aerosol acidity on ambient SOA formation. |
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