Inferring the Sources of Fine and Ultrafine Particulate Matter at Downwind Receptor Sites in the Los Angeles Basin Using Multiple Continuous Measurements Special Issue ofAerosol Science and Technologyon Findings from the Fine Particulate Matter Supersites Program

Abstract

Recent studies that have found increased health effects of atmospheric ultrafine particulate matter (PM) have refocused attention on particle number rather than particle mass concentrations as a relevant measurement of PM pollution. As part of the Southern California Supersite program, ambient particle characteristics were measured over 13 months at three different sites in the eastern portion of the Los Angeles Basin: Riverside, Rubidoux, and Claremont, CA. The sites represent receptor locations that are influenced by local particle sources as well as advection from the more intense particle sources upwind closer to Downtown Los Angeles. An SMPS/APS tandem system was employed to collect continuous particle size distributions, from which particle number and mass concentrations were calculated. An aethalometer provided continuous particulate elemental carbon (EC) concentrations. Results show no meaningful correlation between particle number and mass, indicating that fine particle standards may not be effective in controlling ultrafine concentrations. Diurnal patterns show a morning traffic peak indicated by increases in particle mass, number, and EC. Afternoon periods in the warmer months are characterized by high number counts while mass and EC remain low, suggesting the formation of new particles by photochemistry. Particle mode diameters range from 30 nm up to above 100 nm, a result not seen in most other studies of particle size distributions in other urban or rural areas where mode diameters are generally less than 50 nm. Evidence is presented that the observed ultrafine particle concentrations and size distributions are influenced by long-range advection and photochemical processes as well as vehicular emissions, which have been previously assumed to dominate day-to-day ultrafine particle levels.

Seasonal and spatial trends in particle number concentrations and size distributions at the children's health study sites in Southern California

“…The correlation between PN concentrations and PM 10 has been widely studied and weak-to-moderate correlations have been generally observed between the two (Morawska et al, 1998;Woo et al, 2001;Noble et al, 2003;Fine et al, 2004;Sardar et al, 2004). Since the fine to ultrafine particle counts are dominated by very small particles and the PM 10 mass is dominated by fewer, much larger particles, low correlation should be expected, especially in air masses dominated by fresher particles (either primary emission particles or freshly formed secondary particles).…”

“…Some recent continental sampling campaigns that measured size distributions include the Pittsburgh Air Quality Study (Stanier et al, 2004), the Atlanta PM Supersite program (Woo et al, 2001), and sampling campaigns in Los Angeles (Kim et al, 2002;Fine et al, 2004), Northern Europe (Ruuskanen et al, 2001), Tennessee (Cheng and Tanner, 2002), Brisbane, Australia (Morawska et al, 2002), the UK (Harrison et al, 2000), Estonia and Finland (Kikas et al, 1996) and Central Europe (Birmili et al, 2001). Most of these studies were con ducted in urban areas in which the vast majority of ultrafine PM originate from primary sources (Morawska et al, 1998;Harrison et al, 2000;Woo et al, 2001), thus their diurnal profiles match those of local vehicular sources.…”

“…Kim et al (2002) identified periods of photochemistry and long-range advection as sources of ultrafine PM at two sites in Los Angeles Basin in addition to local vehicular emissions. Fine et al (2004) inferred sources of ultrafine particles at two different locations in the eastern portion of Los Angeles Basin. Buzorius et al (1999) measured aerosol characteristics at a series of sites in Helsinki, Finland in order to investigate the transport of aerosol traveling from source sites to receptor sites.…”

Uncertainty Budget of the SMPS–APS System in the Measurement of PM1, PM2.5, and PM10

“…Literature studies on monitoring ambient aerosol, in fact, estimated particle density in the size range 1.5-1.8 g cm −3 (Morawska et al 1999a;Sioutas et al 2000;Shen et al 2002;Fine et al 2004;Barone et al 2006;Buonanno et al 2009). The density has to be directly measured in every aerosol characterization.…”

“…It measures the number size distribution and total number concentration over a wide range (from few nanometers up to 20 µm) and it is also able to estimate the mass distribution and its total concentration, after having determined particle density (Sioutas et al 1999;Fine et al 2004;Buonanno et al 2009). …”