title: Long-term source apportionment of ambient fine particulate matter (PM2.5) in the Los Angeles Basin: a focus on emissions reduction from vehicular sources.
abstract: Positive Matrix Factorization (PMF) was utilized to quantify sources of ambient PM2.5 in central Los Angeles (LA) and Rubidoux, using the Speciation Trends Network data, collected between 2002 and 2013. Vehicular emissions (including gasoline and diesel vehicles) were the second major contributor to PM2.5, following secondary aerosols, with about 20% contribution to total mass in both sites. Starting in 2007, several major federal, state, and local regulations on vehicular emissions were implemented. To assess the effect of these regulations, daily-resolved vehicular source contributions from 2002 to 2006 were pooled together and compared to the combination of 2008 to 2012 datasets. Compared to the 2002-2006 dataset, the median values of vehicular emissions in 2008-2012 statistically significantly decreased by 24 and 21% in LA and Rubidoux, respectively. These reductions were noted despite an overall increase or similarity in the median values of the daily flow of vehicles after 2007, at the sites.
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
authors.forename: Sina
authors.initials: S
authors.lastname: Hasheminassab
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Daher
authors.affiliation: Air Pollution Epidemiology Section, Office of Environmental Health Hazard Assessment, State of California, Oakland, CA, USA.
authors.forename: Bart D
authors.initials: BD
authors.lastname: Ostro
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, Los Angeles, CA, USA. Electronic address: sioutas@usc.edu.
authors.forename: Constantinos
authors.initials: C
authors.lastname: Sioutas
mesh_terms: D000336:Aerosols / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D004784:Environmental Monitoring; D005742:Gasoline / Q000032:analysis; D015141:Los Angeles; D052638:Particulate Matter / Q000032:analysis*; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D005742:Gasoline; D052638:Particulate Matter; D001335:Vehicle Emissions
keywords: Los Angeles Basin; PM(2.5); Positive matrix factorization; Source apportionment; Vehicular emissions reduction