AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
On-road Emission Factors of PM Pollutants for Light-duty Vehicles (LDVs) Based on Real-world Urban Street Driving Conditions
WINNIE KAM, James Liacos, James Schauer, Ralph Delfino, Constantinos Sioutas, University of Southern California
Abstract Number: 45 Working Group: Urban Aerosols
Abstract An on-road sampling campaign was conducted on two major surface streets (Wilshire and Sunset Boulevards) in Los Angeles, CA, to characterize particulate matter (PM) components including metals, trace elements, and organic species for three size fractions (PM$_(10-2.5), PM$_(2.5-0.25), and PM$_(0.25)). Fuel-based emission factors (EFs) (mass of pollutant per kg of fuel) were calculated to assess the emissions profile of a light-duty vehicle (LDV) fleet that is reflective of real-world urban driving. EFs for metals and trace elements were highest in PM$_(10-2.5) while EFs for polycyclic aromatic hydrocarbons (PAHs) and hopanes and steranes were highest in PM$_(0.25). PM$_(2.5) EFs were also compared to previous freeway, tunnel, and dynamometer studies based on an LDV fleet to determine how various environments and driving conditions may influence concentrations of PM components. The on-road sampling methodology deployed in the current study captured substantially higher levels of metals and trace elements associated with vehicular abrasion (Fe, Ca, Cu, and Ba) and crustal origins (Mg and Al) than previous LDV studies. The semi-volatile nature of PAHs resulted in higher levels of PAHs in the particulate phase for LDV tunnel studies and lower levels of PAHs in the particulate phase for freeway studies. With the exception of a few high molecular weight PAHs, the current study’s EFs laid in between the LDV tunnel and LDV freeway studies. In contrast, hopane and sterane EFs were generally comparable between the current study, the LDV tunnel, and LDV freeway, as expected given the greater atmospheric stability of these organic compounds. Overall, EFs from the dynamometer studies for metals, trace elements, and organic species are lower than the current study. Lastly, n-alkanes (C19-C40) were quantified and alkane carbon preference indices (CPIs) were determined to be in the range of 1-2, indicating substantial anthropogenic source contribution for surface streets in Los Angeles.