Project at a Glance

Title: Operation of SMPS and low temperature TEOM in locations of the USC Children's Health Study (CHS) and the Los Angeles supersite.

Principal Investigator / Author(s): Sioutas, Constantinos

Contractor: University of Southern California

Contract Number: 01-300

Research Program Area: Health & Exposure, Atmospheric Processes

Topic Areas: Health Effects of Air Pollution, Monitoring, Vulnerable Populations


Continuous measurements of particle number, particle size-distribution (14-700 nm) and particle mass (PM10) were obtained at thirteen sites (urban, suburban and remote) in Southern California during years 2002, 2003 and 2004 in support of University of Southern California Children’s Health Study (CHS). We report the spatial and temporal variation of particle mass, numbers and number size distributions within these sites. Scanning Mobility Particle Sizer monitors were used to measure particle number size data and low temperature Tapered Element Oscillating Microbalance monitors were used for PM10 mass measurement. Higher average total particle number concentrations are found in winter (November to February), compared to summer (July to September) and spring (March to June) in all urban sites. Contribution of local vehicular emissions is most evident in cooler months, whereas effects of long-range transport of particles are enhanced during warmer periods. The particle size profile is most represented by a combination of the spatial effects, e.g. sources, atmospheric processes and meteorological conditions prevalent at each location. Afternoon periods in the warmer months are characterized by elevated number concentrations, suggesting the formation of new particles by photochemistry. The results presented in this report indicate that location and season significantly influence particle number and size distributions in locations within Southern California. Strong diurnal and seasonal patterns in number concentrations are evident as a direct effect of the sources, formation mechanisms, as well as meteorological conditions prevalent at each location during different times of the day and year. These results will be used in the CHS as a first order indicator of not only human exposure, but also inhaled dose to ultrafine PM. They will also be used for the development and validation of predictive models for population exposure assessment to ultrafine PM in complex urban environments, such as that of the Los Angels Basin.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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