AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Near-Road Spatial Distribution of Ultrafine Particles and Black Carbon across the Los Angeles Metropolitan Area
ARIAN SAFFARI, Sina Hasheminassab, Farimah Shirmohammadi, Dongbin Wang, Mohammad Sowlat, Roel Vermeulen, Gerard Hoek, Rena Jones, Debra Silverman, Constantinos Sioutas, University of Southern California
Abstract Number: 24 Working Group: Urban Aerosols
Abstract Roadways are known as the major source of ultrafine and black carbon (BC) particulate emissions in southern California. To enhance our understanding of the small-scale spatial distribution of these parameters in the vicinity of major roadways, short-term measurements of BC and ultrafine particle (UFP) number concentration were carried out at nearly 200 locations across the Los Angeles metropolitan area, spanning from the county of Los Angeles in the west, to the counties of Riverside and Orange in the east and south of the basin. For each study location, 4 spots with different distances from the roadway (less than 50 meters, between 50 and 150 meters and more than 150 meters downwind, in addition to one spot upwind) were selected and monitored, using a mobile monitoring platform equipped with Discmini and micro aethalometer instruments. Measurements were performed for 30 minutes at each site, between 9am and 4pm, to avoid traffic spikes of the morning and afternoon rush hours. To correct the measurements for temporal variations across different sites, all concentrations were normalized by simultaneous measurements at a background stationary site, located sufficiently far from major roadways. Concentrations of BC and UFPs indicated a significant “within-site” spatial variability, with higher levels in the immediate vicinity of the freeway (i.e. less than 50 meters of distance) compared to the regions more than 150 meters from the edge of the freeway. Extent of “between-site” variability of BC and UFP concentrations, however, was proportional to the diversity of emission sources in each region. Specifically, the Port of Long Beach and the airport regions exhibited highest spatial variability compared to the rest of the basin. These measurements, along with air quality predicting variables such as traffic density and meteorological conditions, will be used for development of future land use regression models in the Los Angeles area.