Size distribution of trace organic species emitted from light-duty gasoline vehicles

作者：Riddle Sarah G; Robert Michael A; Jakober Chris A; Hannigan Michael P; Kleeman Michael J^*

来源：Environmental Science & Technology, 2007, 41(21): 7464-7471.

DOI：10.1021/es070153n

Size distributions for particulate hopanes+steranes and nonvolatile polycyclic aromatic hydrocarbons (PAHs) emitted from five classes of light-duty gasoline-powered vehicles were measured using the federal test procedure (FTP), unified cycle (UC), and correction cycle (CC) driving cycles. 17 alpha(H)-21 beta(H)-29-norhopane, 17 alpha(H)-21 beta(H)-hopane, alpha beta beta-20R-stigmastane, and (alpha beta beta-20S-stigmastane were highly. correlated and behaved consistently across sampling methods. Coronene and benzo[ghi]perylene were the most ubiquitous heavy PAHs detected in the vehicle exhaust. The emission rates of hopanes, steranes, and PAHs contained in particles with aerodynamic diameters of less than 1.8 mu m varied by 2 orders of magnitude between the lowest- and highest-emitting vehicle classes. Hopane+sterane size distributions emitted from vehicles without an operating catalyst (including "cold-start" emissions from catalystequipped vehicles) were bimodal with one mode between 0.10 and 0.18 urn and the second mode >0.32 u mu m particle diameter. Hopane+sterane emissions released from vehicles with a catalyst at operating temperature had a single mode between 0.1 and 0.18 mu m diameter. Hopane+sterane emissions from visibly smoking vehicles had a single mode between 0.18 and 0.32 mu m diameter. Heavy PAH size distributions for all vehicle classes consistently had a single mode between 0.10 and 0.18 mu m particle diameter (0.1 -0.32 mu m diameter for smoking vehicles). The geometric standard deviations for PAH size distributions were generally smaller than the corresponding hopane+sterane distributions. These trends suggest that hopanes+steranes and heavy PAHs act as tracers for separate processes of particulate organic carbon formation. PAH and hopane+sterane emissions shifted to smaller sizes during the more aggressive UC and CCdriving cycles relative to the FTP. The fraction of PAH and hopane+sterane emissions in the ultrafine (D-p < 0.1,mu m) range more than doubled during "warm-start" UC and CC cycles vs the FTP cycle. The enhancement of ultrafine PAHs during "cold-start" UC driving cycles was less pronounced.

• 出版日期2007-11-1