title: Long-term trends in California mobile source emissions and ambient concentrations of black carbon and organic aerosol.
abstract: A fuel-based approach is used to assess long-term trends (1970-2010) in mobile source emissions of black carbon (BC) and organic aerosol (OA, including both primary emissions and secondary formation). The main focus of this analysis is the Los Angeles Basin, where a long record of measurements is available to infer trends in ambient concentrations of BC and organic carbon (OC), with OC used here as a proxy for OA. Mobile source emissions and ambient concentrations have decreased similarly, reflecting the importance of on- and off-road engines as sources of BC and OA in urban areas. In 1970, the on-road sector accounted for ∼90% of total mobile source emissions of BC and OA (primary + secondary). Over time, as on-road engine emissions have been controlled, the relative importance of off-road sources has grown. By 2010, off-road engines were estimated to account for 37 ± 20% and 45 ± 16% of total mobile source contributions to BC and OA, respectively, in the Los Angeles area. This study highlights both the success of efforts to control on-road emission sources, and the importance of considering off-road engine and other VOC source contributions when assessing long-term emission and ambient air quality trends.
authors: Brian C
authors: BC
authors: McDonald
authors: Allen H
authors: AH
authors: Goldstein
authors: Robert A
authors: RA
authors: Harley
mesh_terms: D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D002140:California; D002244:Carbon / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D015141:Los Angeles; D053260:Soot / Q000032:analysis*; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D053260:Soot; D001335:Vehicle Emissions; D002244:Carbon