Determination of urban volatile organic compound emission ratios and comparison with an emissions database. Journal of Geophysical Research, 112, D10S47

University of Colorado Boulder, Boulder, Colorado, United States
Journal of Geophysical Research-Atmospheres 05/2007; 112(D10):D10S47. DOI: 10.1029/2006JD007930


During the NEAQS-ITCT2k4 campaign in New England, anthropogenic VOCs and CO were measured downwind from New York City and Boston. The emission ratios of VOCs relative to CO and acetylene were calculated using a method in which the ratio of a VOC with acetylene is plotted versus the photochemical age. The intercept at the photochemical age of zero gives the emission ratio. The so determined emission ratios were compared to other measurement sets, including data from the same location in 2002, canister samples collected inside New York City and Boston, aircraft measurements from Los Angeles in 2002, and the average urban composition of 39 U.S. cities. All the measurements generally agree within a factor of two. The measured emission ratios also agree for most compounds within a factor of two with vehicle exhaust data indicating that a major source of VOCs in urban areas is automobiles. A comparison with an anthropogenic emission database shows less agreement. Especially large discrepancies were found for the C2-C4 alkanes and most oxygenated species. As an example, the database overestimated toluene by almost a factor of three, which caused an air quality forecast model (WRF-CHEM) using this database to overpredict the toluene mixing ratio by a factor of 2.5 as well. On the other hand, the overall reactivity of the measured species and the reactivity of the same compounds in the emission database were found to agree within 30%.

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    • "The possible explanations for the underestimation of carbonyl emissions included (1) underestimation of the carbonyl emission factors for vehicle exhaust and/or (2) underestimation of carbonyl emissions from other sources (Borbon et al., 2013; Warneke et al., 2007). In the inventory built by Li et al. (2014), the VOC emission factors and profiles for gasoline and diesel vehicular exhaust were measured in China (Liu et al., 2008), and thus the uncertainty of transportation-related VOC emissions was relatively low. "
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    • "ies carried out in urban areas and near streets with a heavy traffic flow ( Barletta et al . 2005 ; Hoque et al . 2008 ; Khoder 2007 ; Wang and Zhao 2008 ) , implying that traffic is the main source of these compounds . Nevertheless , other works in urban areas have reported even higher ratios of T / B ( Elbir et al . 2007 ; Gee and Sollars 1998 ; Warneke et al . 2007"
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