Size Distribution of Trace Organic Species Emitted from Light-Duty Gasoline Vehicles

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• 作者：Sarah G. Riddle ; Michael A. Robert ; Chris A. Jakober ; Michael P. Hannigan ; Michael J. Kleeman
• 刊名：Environmental Science & Technology
• 出版年：2007
• 出版时间：November 1, 2007
• 年：2007
• 卷：41
• 期：21
• 页码：7464 - 7471
• 全文大小：336K
• 年卷期：v.41,no.21(November 1, 2007)
• ISSN：1520-5851

文摘

Size distributions for particulate hopanes+steranes andnonvolatile polycyclic aromatic hydrocarbons (PAHs) emittedfrom five classes of light-duty gasoline-powered vehicleswere measured using the federal test procedure (FTP),unified cycle (UC), and correction cycle (CC) driving cycles.17(H)-21(H)-29-norhopane, 17(H)-21(H)-hopane, -20R-stigmastane, and -20S-stigmastane were highlycorrelated and behaved consistently across samplingmethods. Coronene and benzo[ghi]perylene were the mostubiquitous heavy PAHs detected in the vehicle exhaust.The emission rates of hopanes, steranes, and PAHs containedin particles with aerodynamic diameters of less than 1.8m varied by 2 orders of magnitude between the lowest- andhighest-emitting vehicle classes. Hopane+sterane sizedistributions emitted from vehicles without an operatingcatalyst (including "cold-start" emissions from catalyst-equipped vehicles) were bimodal with one mode between0.10 and 0.18 m and the second mode >0.32 m particlediameter. Hopane+sterane emissions released fromvehicles with a catalyst at operating temperature had asingle mode between 0.1 and 0.18 m diameter.Hopane+sterane emissions from visibly smoking vehicleshad a single mode between 0.18 and 0.32 m diameter.Heavy PAH size distributions for all vehicle classesconsistently had a single mode between 0.10 and 0.18 mparticle diameter (0.1-0.32 m diameter for smokingvehicles). The geometric standard deviations for PAH sizedistributions were generally smaller than the correspondinghopane+sterane distributions. These trends suggestthat hopanes+steranes and heavy PAHs act as tracersfor separate processes of particulate organic carbonformation. PAH and hopane+sterane emissions shifted tosmaller sizes during the more aggressive UC and CCdriving cycles relative to the FTP. The fraction of PAHand hopane+sterane emissions in the ultrafine (D_p < 0.1m) range more than doubled during "warm-start" UC andCC cycles vs the FTP cycle. The enhancement of ultrafinePAHs during "cold-start" UC driving cycles was lesspronounced.