title: Diurnal and seasonal trends in the apparent density of ambient fine and coarse particles in Los Angeles.
abstract: Diurnal and seasonal variations in the apparent density of ambient fine and coarse particulate matter (PM2.5 and CPM [PM2.5-10], respectively) were investigated in a location near downtown Los Angeles. The apparent densities, determined by particle mass-to-volume ratios, showed strong diurnal and seasonal variations, with higher values during the warm phase (June to August 2013) compared to cold phase (November 2012 to February 2013). PM2.5 apparent density showed minima during the morning and afternoon rush hours of the cold phase (1.20g cm(-3)), mainly due to the increased contribution of traffic-emitted soot particles, and highest values were found during the midday in the warm phase (2.38g cm(-3)). The lowest CPM apparent density was observed during the morning rush hours of the cold phase (1.41g cm(-3)), while highest in early afternoon during the warm phase (2.91g cm(-3)), most likely due to the increased wind-induced resuspension of road dust.
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, 3620 South Vermont Avenue, Los Angeles, CA 90089, USA.
authors.forename: Sina
authors.initials: S
authors.lastname: Hasheminassab
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, 3620 South Vermont Avenue, Los Angeles, CA 90089, USA.
authors.forename: Payam
authors.initials: P
authors.lastname: Pakbin
authors.affiliation: University of California, Department of Epidemiology, School of Medicine, 224 Irvine Hall, Irvine, CA 92697, USA.
authors.forename: Ralph J
authors.initials: RJ
authors.lastname: Delfino
authors.affiliation: University of Wisconsin-Madison, Environmental Chemistry and Technology Program, 660 North Park Street, Madison, WI 53706, USA.
authors.forename: James J
authors.initials: JJ
authors.lastname: Schauer
authors.affiliation: University of Southern California, Department of Civil and Environmental Engineering, 3620 South Vermont Avenue, Los Angeles, CA 90089, USA. Electronic address: sioutas@usc.edu.
authors.forename: Constantinos
authors.initials: C
authors.lastname: Sioutas
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data; D004391:Dust / Q000032:analysis; D004784:Environmental Monitoring; D015141:Los Angeles; D052638:Particulate Matter / Q000032:analysis*; D012621:Seasons; D053260:Soot / Q000032:analysis
chemical_list: D000393:Air Pollutants; D004391:Dust; D052638:Particulate Matter; D053260:Soot
keywords: Apparent density; Chemical composition; Material density; Morphology; Particulate matter (PM)