Characterization and source identification of trace elements in PM2.5 from Mira Loma, Southern California

Concentrations of thirty-five trace elements in ambient fine particulate matter (PM_2.5) were measured from September 2001 to January 2002 in Mira Loma, a semi-urban area in southern California. The most abundant species were found to be sulfur (S; 23% of the total trace element concentration), followed by Si, Fe, Ca, and Al (soil-related elements; 51% of the total). In general, total trace element concentrations were found to be significantly higher for the drier months of September and October, compared to December and January. Factor analysis, enrichment factor (EF) analysis, and ratio analysis (Al/Zn) revealed a significant contribution of soil-related sources to the ambient trace elements for PM_2.5 in the study area. Other important contributors to the trace elements in ambient PM_2.5 in Mira Loma included motor vehicle-related emissions (brake pads, lubricant oils, gasoline, and diesel combustion), secondary sulfates, sea salts, and biomass burning. The influence of sea salts on the study area was identified using a backward trajectory analysis.