Flux measurements of volatile organic compounds by the relaxed eddy accumulation method combined with a GC-FID system in urban Houston,Texas |
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| Authors: | Changhyoun Park Gunnar W Schade Ian Boedeker |
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| Institution: | 1. DePaul University, Department of Environmental Science and Studies, 1110 W Belden Ave, Chicago, IL 60614, USA;2. University of Missouri, Department of Forestry, Columbia, MO 65211, USA;3. Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN 37831, USA;4. University of Innsbruck, Institute of Meteorology and Geophysics, A-6020 Innsbruck, Austria;5. U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Air pollution Prevention and Control Division, Research Triangle Park, NC 27711, USA;6. Pacific Northwest National Laboratory, Atmospheric Sciences and Global Change Division, Richland, WA 99352, USA;1. Chemical and Environmental Engineering Department, University College of Technical Mining and Civil Engineering, University of the Basque Country UPV/EHU, Rafael Moreno ''Pitxitxi'' 2, 48013 Bilbao, Spain;2. Chemical and Environmental Engineering Department, School of Engineering, University of the Basque Country UPV/EHU, Alameda de Urquijo s/n, 48013 Bilbao, Spain;1. National Institute of Legal Medicine and Forensic Sciences—Centre Branch, Largo da Sé Nova, 3000-213 Coimbra, Portugal;2. CENCIFOR—Forensic Sciences Centre, Largo da Sé Nova, 3000-213 Coimbra, Portugal;3. National Institute of Legal Medicine and Forensic Sciences—South Branch, Rua Manuel Bento de Sousa 3, 1150-219 Lisboa, Portugal;4. Faculty of Medicine—University of Coimbra, Largo da Sé Nova, 3000-213 Coimbra, Portugal;1. Institute of Environmental Studies, Pusan National University, Busan, 46241, South Korea;2. Department of Atmospheric Sciences, Texas A&M University, 3150 TAMU, College Station, TX 77843, USA;3. Department of Mechanical and Materials Engineering, Portland State University, Portland, OR 97207, USA;4. Department of Atmospheric Environmental Sciences, Pusan National University, Busan, 46241, South Korea;1. Hokkaido Research Center, Forestry and Forest Products Research Institute (FFPRI), Forest Research and Management Organization, 7 Hitsujigaoka, Sapporo, Hokkaido, 062-8516, Japan;2. Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Sapporo, Hokkaido, 060-8589, Japan;3. Department of Environmental Health Sciences, Morrill I, N344, University of Massachusetts, Amherst, MA 01003, USA |
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| Abstract: | A tall tower flux measurement setup was established in metropolitan Houston, Texas, to measure trace gas fluxes from emission sources in the urban surface layer. We describe a new relaxed eddy accumulation (REA) system combined with a dual-channel GC-FID used for VOC flux measurements, focusing on benzene, toluene, ethylbenzene and xylenes (BTEX) results. Ambient air sampled from 60 m above the ground next to a sonic anemometer was subsampled by a membrane pump and pushed into an REA valve system with two Teflon bag reservoirs, then transferred to two preconcentration units for thermal desorption. We discuss the performance of our system and the selected BTEX measurement results using approximately 8 weeks of data (May 22–July 22, 2008), presenting diurnal variations of concentrations and fluxes of these traffic tracers. The measured values exhibited diurnal cycles with dominant morning and midday peaks during weekdays related to rush hour traffic and additional weekday daytime toluene and xylenes emissions. Local evaporative emissions, likely from solvent usage, significantly contributed to the measured fluxes. We upscaled measured emissions to the county level using a high resolution land cover data set and compared the results with EPA’s National Emission Inventory (NEI). |
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