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

Journal of Geophysical Research-Atmospheres 01/2007; 112:D10S47. DOI: 10.1029/2006JD007930

ABSTRACT 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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    • "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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    ABSTRACT: Diffusive samplers were used to measure the vertical concentrations of benzene, toluene, n-hexane, cyclohexane, ethylbenzene and o-, m- and p-xylenes on both sides of two NS-oriented street canyons in Murcia (Spain) during a 5-day period. Non-dimensional relationships of concentration and height were calculated in order to study the behaviour of their concentration vertical profiles. The results show that the vertical profiles of benzene, toluene, n-hexane and cyclohexane concentrations were similar in both streets and on both sides of each street. Some differences were found in vertical profiles between streets and sides for ethylbenzene and xylenes, probably due to their higher affinity for adsorption into building materials. The similarities found for the first set of VOCs suggest that the dynamics of the dispersion was the same for both streets and was mainly influenced by microscale thermal effects. Finally, the concentration measurements of benzene, toluene, n-hexane, cyclohexane, and ethylbenzene were adjusted to expressions in the form c = c (0)(h/h (0))( A ), and a regression coefficient R (2) = 0.962 (p = 0.0000) was obtained. The decreasing concentration of these compounds with height should be taken into account when assessing population exposure to these pollutants.
    Environmental Monitoring and Assessment 02/2012; 184(12). DOI:10.1007/s10661-011-2504-x · 1.68 Impact Factor
    • "Furthermore, VOCs from the road transport emissions sector have the highest ozone forming potential as an emissions sector (Derwent et al., 2007). Anthropogenic emissions databases used for modelling VOCs have previously been shown to underestimate VOC concentrations and have large uncertainties, especially for developing megacities (Karl et al., 2009; Lei et al., 2007; Warneke et al., 2007). Ratios of VOCs with respect to CO would be particularly useful for assessing the extent to which VOC emissions were dominated by traffic-related emissions, and possibly for applying this to improve VOC emissions databases for urban trafficdominated areas in Annex I countries. "
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    ABSTRACT: Since 2007, more than half of the world's population live in urban areas. Megacities, urban agglomerations with more than 10 million inhabitants, are rapidly increasing in number: in 1950 there were only two, New York and Tokyo with ~12 million, while by 2005 there were already 20, with Tokyo ranging the 35 millions. The urban atmospheres of these megacities are dominated by pollutants associated with vehicular emissions, as well as the formation of secondary pollutants responsible for photochemical smog. A comparative assessment of emissions and concentrations of volatile organic compounds (VOC) and carbon monoxide (CO) ratios in London (L) and Paris (P) is hereby presented. The work is based on three recent studies by Baker et al. (2008), Parrish et al. (2009) and von Schneidemesser et al. (in press) where concentrations of these compounds were analyzed for 28 US cities in the former and some global megacities in the second and third studies. Considering the fact that VOC provide information on the main emissions sources of cities, these studies found that even though concentrations of VOC varied greatly among cities, the ratio with the combustion tracer CO remained rather constant and was very useful for city comparison, as well as a good indicator of traffic emissions. VOC patterns in ambient air concentrations were observed to be similar in most cities, being able to consider that deviations from those patterns could be the result of measurement problems. Nevertheless, the representation of these emissions in global inventories has large uncertainties. The goal of our study is to compare and contrast emission inventory estimates with measured ambient concentrations of non-methane hydrocarbons (NMHC) and CO, as well as NMHC:CO ratios. Within the European CityZen project we have built an updated global emissions inventory with the best available datasets of anthropogenic, biomass burning and natural sources. As part of this research we will follow the same approach to compare emissions ratios between NMHC and CO for the megacities region of Paris and London and to compare these trends with measured ambient concentrations from three monitoring sites: Eltham (L) suburban station, Marylebone Road (L) kerbside station and Les Halles (P) urban station for the period 1997-2006.
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    • "Furthermore, VOCs from the road transport emissions sector have the highest ozone forming potential as an emissions sector (Derwent et al., 2007). Anthropogenic emissions databases used for modelling VOCs have previously been shown to underestimate VOC concentrations and have large uncertainties, especially for developing megacities (Karl et al., 2009; Lei et al., 2007; Warneke et al., 2007). Ratios of VOCs with respect to CO would be particularly useful for assessing the extent to which VOC emissions were dominated by traffic-related emissions, and possibly for applying this to improve VOC emissions databases for urban trafficdominated areas in Annex I countries. "
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