Detailed hydrocarbon and aldehyde mobile source emissions from roadway studies

Zweidinger, Roy B.; Sigsby, John E.; Tejada, Silvestre B.; Stump, Fred D.; Dropkin, D.; Ray, William D.; Duncan, John W.

doi:10.1021/es00173a015

Cited by 86 publications

(58 citation statements)

References 7 publications

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“…It is shown that the concentration ratios for BTEX compounds measured at every monitoring station bear some resemblance to the ratios reported in the roadside study. The concentration ratios of the BTEX compounds--benzene/ethylbenzene (2.26-2.88), toluene/ ethylbenzene (3.62-5.63), o,m,p-xylene/ethylbenzene (4.32-5.97)--reported by other roadside studies and dynamometer studies (Zweidinger et al, 1988;Westerholm et al, 1996;Zielinska et al, 1996;Staehelin et al, 1998) are also comparable with the values in Fig. 3.…”

Section: Resultssupporting

confidence: 85%

Volatile organic compounds in some urban locations in United States

2002

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Importance of this paper: Air pollution in urban locations contains many components that originate from a wide range of industrial, motor vehicle, and natural emissions sources. Some of these components include compounds known or suspected to be carcinogenic, and some of them play important roles in atmospheric chemistry such as tropospheric ozone pollution and stratospheric ozone depletion. Therefore, it is essential to characterize the composition, magnitude, and the distribution of urban air pollution through extensive ambient air monitoring and assess the impact of these components on human health and global atmospheric chemistry. AbstractVolatile organic compounds (VOCs) have been determined to be human risk factors in urban environments, as well as primary contributors to the formation of photochemical oxidants. Ambient air quality measurements of 54 VOCs including hydrocarbons, halogenated hydrocarbons and carbonyls were conducted in or near 13 urban locations in the United States during September 1996 to August 1997. Air samples were collected and analyzed in accordance with US Environmental Protection Agency-approved methods. The target compounds most commonly found were benzene, toluene, xylene and ethylbenzene. These aromatic compounds were highly correlated and proportionally related in a manner suggesting that the primary contributors were mobile sources in all the urban locations studied. Concentrations of total hydrocarbons ranged between 1.39 and 11.93 parts per billion, by volume (ppbv). Ambient air levels of halogenated hydrocarbons appeared to exhibit unique spatial variations, and no single factor seemed to explain trends for this group of compounds. The highest halogenated hydrocarbon concentrations ranged from 0.24 ppbv for methylene chloride to 1.22 ppbv for chloromethane. At participating urban locations for the year of data considered, levels of carbonyls were higher than the level of the other organic compound groups, suggesting that emissions from motor vehicles and photochemical reactions strongly influence ambient air concentrations of carbonyls. Of the most prevalent carbonyls, formaldehyde and acetaldehyde were the dominant compounds, ranging from 1.5-7.4 ppbv for formaldehyde, to 0.8-2.7 ppbv for acetaldehyde. Ó

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Section: Resultssupporting

confidence: 85%

Volatile organic compounds in some urban locations in United States

2002

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“…Transient tracer experiments have been used in roadway studies. 15 The steady SF 6 release technique has been used in earlier studies. 3,16 Several features of the transient and steady tests were the same.…”

Section: Description Of the Tracer Experimentsmentioning

confidence: 99%

Use of Tracer Gas for Direct Calibration of Emission-Factor Measurements in a Traffic Tunnel

Rogak

Green

Pott

1998

Journal of the Air & Waste Management Association

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Pollutant measurements in traffic tunnels have been used to estimate motor-vehicle emissions for several decades. The objective in this type of study is to use the traffic tunnel as a tool for characterizing motor vehicles rather than seeking a tunnel design with acceptably low pollutant concentrations. In the past, very simple aerodynamic models have been used to relate measured concentrations to vehicle emissions. Typically, it is assumed that velocities and concentrations are uniform across the tunnel cross section. In the present work, a vehicle emitting a known amount of sulfur hexafluoride (SF 6 ) was driven repeatedly through a 730-m-long traffic tunnel in Vancouver, Canada. Comparing the measured SF 6 concentrations to the known emission rates, it is possible to directly assess the accuracy of the simple tunnel aerodynamic models typically used to interpret tunnel data. Correction factors derived from this procedure were then applied to measurements of carbon monoxide and other pollutants to obtain gram-per-kilometer emission factors for vehicles. Although the specific correction factors measured here are valid only for the tunnel tested, the magnitude of the factors (up to two or more) suggests that the phenomena observed here should be considered when interpreting data from other tunnels. IMPLICATIONSFor several decades, vehicle emissions have been inferred from traffic-tunnel measurements. Although ratios of pollutants (e.g., CO/NO x ) can typically be measured quite accurately in the tunnel environment, it is often difficult to measure rates in gram per mile or gram per kilometer, partly because of uncertainties in the aerodynamic behavior of the tunnel. In the Cassiar tunnel, aerodynamic factors can bias measured emission factors by up to a factor of 2. The direct calibration technique developed here allows more accurate measurement of g/km emissions. This can make tunnel studies an even more powerful tool for assessing the performance of emission models and air-quality management measures.

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“…Alkenes can be found in a variety of fuels and automobile exhaust, as well as in other industrial and agricultural (biomass burning) processes [20,21]. Biogenic sources of alkenes include emissions from vegetation, soils and the ocean [22].…”

Section: Introductionmentioning

confidence: 99%