Use of a Mobile Instrument Platform to Measure On-Road Concentrations of Ultrafine Particles and Other Air Pollutants in Los Angeles

Speaker: 

Scott Fruin

Environmental Health Division Keck School of Medicine ,USC

Abstract:
Motor vehicles are the dominant source of oxides of nitrogen (NOx), particulate matter (PM), and many air toxics (e.g., benzene, 1,3-butadiene) in most urban areas. On roadways, motor vehicle-related pollutant concentrations are typically many times higher than ambient concentrations. Due to high air exchange rates typical of moving vehicles, this makes time spent in vehicles on roadways a major source of exposure. This talk presents on-road measurements for Los Angeles freeways and arterial roads taken from a zero-emission electric vehicle outfitted with real-time instruments. The objective was to characterize air pollutant concentrations on roadways and identify the factors associated with the highest concentrations. Our analysis demonstrated that on freeways, concentrations of ultrafine particles (UFP), black carbon, nitric oxide, and PM-bound PAH are generated primarily by diesel-powered vehicles, despite the relatively low average fraction (~6%) of diesel-powered vehicles on Los Angeles freeways. However, UFP concentrations on arterial roads appeared to be driven primarily by proximity to gasoline-powered vehicles undergoing hard accelerations from stops, and were roughly one-third the concentrations of freeways. By using a multiple regression model for the freeway measurements, we were able to explain 60 to 70% of the variability in concentrations of UFP, black carbon, nitric oxide, and PM-bound PAH using measures of diesel truck density and time of day. Freeway concentrations of these pollutants were also well correlated with readily-available annual average daily truck counts from CalTrans, potentially allowing improved population exposure estimates for epidemiology studies. Based on these roadway measurements and average driving time, it appears that about 40 to 50% of total UFP exposure for Los Angeles residents occurs due to time in vehicles.

Date: March 21, 2007
Time: 2:00pm - 3:00pm
Location: KAP203
Audiences: Graduate/Undergrad/Department Only/Everyone is Invited