Project at a Glance

Title: Fine-scale spatial and temporal variability of particle number concentrations within communities and in the vicinity of freeway sound walls

Principal Investigator / Author(s): Sioutas, Constantinos

Contractor: University of Southern California

Contract Number: 05-317

Research Program Area: Atmospheric Processes

Topic Areas: Environmental Justice, Field Studies, Health Effects of Air Pollution, Monitoring, Vulnerable Populations


A network of monitoring sites were established to assess ultrafine particle (UFP; diameter < 0.1Ám) concentrations and their variability. The study was conducted in two phases at two very diverse spatial scales. A cluster of 13 sites was studied in Phase I, distributed over a few miles in communities located in the port area of San Pedro and Long Beach, to understand intra-community variability. In Phase II, a cluster of five sites covering over 50 miles was set up in the eastern Los Angeles basin to assess inter-community variability. Additionally, a site common to both phases was situated in downtown Los Angles to provide a reference point with typical urban background particle number concentrations (PNC). Meaningful variability in particle number concentrations was observed over the limited geographical area from San Pedro to Long Beach. The PNC variability across this source area appears to be driven by proximity to heavily trafficked roadways. The PNC at the sites in eastern Los Angeles exhibited lesser divergence in comparison to the source area even though they were spread over a larger area. However, the greatest variability was associated with impacts of local emissions and certain meteorological conditions. The measurements made in this study help to characterize the variability but it is suggested, due to the dynamic and transient nature of ultrafine particles, that UFPs be studied/measured more closely.

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

Stay involved, sign up with CARB's Research Email Distribution List