The influence of sampling protocol on nonmethane hydrocarbon mixing ratios |
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Authors: | Lambert A Doezema Chris Bigley Gabriele Canzi Kylee Chang Andrew J Hirning Joyce Lee Nick Von der Ahe |
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Institution: | 1. School of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, China;2. Jiangsu Provincial Academy of Environmental Science, Nanjing 210036, China;1. Oak Ridge Institute for Science and Education, Oak Ridge National Laboratories, Oak Ridge, TN, United States;2. United States Environmental Protection Agency, Office of Research and Development, National Center for Environmental Assessment, Research Triangle Park, NC, United States;3. United States Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory, Research Triangle Park, NC, United States |
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Abstract: | The effect of sampling protocol on ambient air hydrocarbon mixing ratios was examined on eight sampling days in Los Angeles during 2007 and 2008. Four protocols, which were based on previously published multi-city urban hydrocarbon studies in the United States, were compared and differences were quantified. Whole air canister samples were collected and analyzed for nonmethane hydrocarbons (NMHCs). Differing sampling protocols resulted in large differences in mixing ratios, up to an order of magnitude, for certain NMHCs on the same sampling day. However, the magnitude of the variability between NMHC levels obtained by the four protocols was not consistent throughout the eight sampling days. It was found that sampling time, followed by sampling location, had the greatest influence on the magnitude of the mixing ratio. Ratios between hydrocarbons, often used in urban studies to gain information on emission sources, also varied depending on the protocol used. Comparison of absolute NMHC mixing ratios collected in urban environments using differing sampling protocols should be made with care. |
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