Trace gas and particulate emissions from the 2003 southern California wildfires

In October 2003, thirteen major wildfires in southern California burned more than 300,000 hectares of mainly chaparral biome. High‐precision in situ trace gas and particle measurements of the wildfire plumes in La Jolla, California, showed a high degree of correlation among carbon dioxide (CO 2 ), methane (CH 4 ), nonmethane hydrocarbons, and methyl halide mixing ratios, as well as with particle number concentrations (10–300 nm and 500–2500 nm aerodynamic diameter). Aerosol time‐of‐flight mass spectrometry of individual aerosol particles (50–2500 nm range) showed that 70–85% had typical biomass burning signatures (levoglucosan coupled with potassium). Only 5–18% of particles in the 50–300 nm range had vehicle signatures. Molar trace gas enhancement ratios (ERs) versus ethane and CO 2 were calculated and showed a narrow age distribution, consistent with the short distance from the wildfires. ERs for N 2 O and CH 3 CCl 3 versus CO 2 were determined, but correlations were poor. No significant CH 2 Cl 2 or CHCl 3 emissions were detected. CO 2 emissions from the nearby Cedar fire were estimated both with a simple Lagrangian atmospheric transport model and a burned area approach and extrapolated to 11 Tg CO 2 for the total burned area in southern California. Total CO 2 , CH 4 , C 2 ‐hydrocarbons, benzene, toluene, methyl chloride, methyl iodide, and PM 2.5 emissions were ∼0.2–3.5% of yearly global extratropical forest fire emissions and more than 28% of CH 4 , C 6 H 6 , and PM 2.5 2003 San Diego and South Coast Air Basins anthropogenic emissions. Particle distributions and single particle chemistry are discussed. PM 2.5 considerably exceeded the EPA short‐term exposure limit.