Field measurement, laboratory modeling and Quick Urban and Industrial Complex (QUIC) simulations were performed to investigate the flow and dispersion of PM2.5 in urban areas. In this study, five Southern Californian urban areas with different building configurations were selected: Anaheim, Pasadena, Long Beach, Los Angeles and Huntington Beach. The representative building geometries in these cities are low density settlement, low-rise settlement, mid-rise settlement, high-rise settlement, and a relatively open area, respectively. The major arterials in these cities are subject to heavy traffic.

The field measurements were conducted in June and July of 2008. Each area was equipped with one sonic anemometer (CSAT3, Campbell Sci.), measuring mean wind, turbulence and virtual temperature, six DustTraks (TSI Inc.), measuring PM2.5 concentration, and three digital cameras (JVC), recording traffic flow, the volume of which is counted via tape reading. Three days measurements were performed in each area and three rush-hour periods for each day were covered. Rush hour periods were: morning 7am-9am, lunch/midday 11am-1pm, and afternoon 4pm-6pm. The correlation between turbulence level, traffic loading and concentration of PM2.5 was investigated. Scale models of urban areas were setup in a water channel facility. Particle image velocimetry (PIV) and planar laser induced fluorescence (PLIF) were applied to measure the velocity vectors and concentration distributions on both horizontal and vertical plane. All five urban areas were also created in the QUIC model. The meteorological data collected by sonic anemometer and emission rate of each road calculated based on the traffic count were input to the model. Both velocity field and concentration field were simulated. The results of modeling and laboratory simulation are validated with field measurements.