A NEIGHBORHOOD-SCALE STUDY OF PM-10 SOURCE CONTRIBUTIONS IN RUBIDOUX, CALIFORNIA

The Rubidoux sampling site in California's South Coast Air Basin has measured one of the highest levels of PM10 mass and ammonium nitrate in the U. S. for several years. Basin-wide emissions reduction strategies are being developed based on the elevated PM10 concentrations measured at Rubidoux. There is concern that a portion of the PM10 at Rubidoux may originate in the neighborhood surrounding the sampling site, and that neighborhood controls may be needed to supplement the basin-wide controls if PM10 standards are to be attained. In 1988, PM10 sampling systems were located at Rubidoux, Riverside-Magnolia, and the University of California at Riverside to quantify the variability of both PM10 and its chemical composition on a neighborhood scale (< 5 km). By means of Chemical Mass Balance receptor modeling using source profiles obtained in the South Coast Air Basin, it was concluded that the Rubidoux site represents urban-scale source contributions from primary motor vehicle exhaust, secondary sulfate, and secondary nitrate. The Rubidoux site also represents a combination of neighborhood-scale and urban-scale source contributions from primary geological and lime/gypsum sources.