AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Size-segregated Composition of Particulate Matter (PM) in Major Roadways and Surface Streets
WINNIE KAM, James Liacos, James Schauer, Ralph Delfino, Constantinos Sioutas, University of Southern California
Abstract Number: 44 Working Group: Urban Aerosols
Abstract A sampling campaign was conducted to assess on-road particulate matter (PM) composition for three size fractions (PM$_(10-2.5),PM$_(2.5-0.25), and PM$_(0.25)) on three representative roadways in Los Angeles: 1) the I-110, a high-traffic freeway composed mostly of light-duty vehicles (LDVs), 2) the I-710, a major freeway for heavy-duty vehicles (HDVs) travelling to and from the Ports of Los Angeles and Long Beach, and 3) Wilshire/Sunset Boulevards, two major surface streets. Concurrent sampling was conducted at the University of Southern California (USC), which was used as an urban background site. Two sets of PM samples were collected for each roadway, and were analyzed for inorganic ions, elemental carbon (EC), organic carbon (OC), water-soluble OC (WSOC), and trace elements and metals. Results showed that the PM$_(0.25) fraction is heavily influenced by on-road vehicular emissions, as indicated by average roadway PM concentrations that were 48.0±9.4% higher than those observed at USC (p<0.05), while the PM$_(10-2.5) fraction is mostly influenced by resuspension of road dust and the PM$_(2.5-0.25) fraction is mainly composed of secondary species. Overall, the composition of inorganic ions (%) was relatively consistent across the three roadway environments. With very low EC levels in PM$_(10-2.5), the most notable difference among the three roadway environments was the PM$_(2.5) EC levels observed on the I-710, which are 2.0±0.2 micro-gram/m$^3 and 4.1 times greater than USC, while levels on the I-110 and Wilshire/Sunset were 1.0±0.2 micro-gram/m$^3 and 0.6±0.01 micro-gram/m$^3 and 2.1 and 1.2 times greater, respectively. Results from this study have major public health implications for passengers who commute frequently on high-traffic roadways. Finally, a comparison of EC levels to previous studies conducted at fixed sites near the I-110 and I-710 showed substantial decreases in EC concentrations over the past years, which may be a result of the recent Port of Los Angeles Clean Truck Program.