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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D03307, doi:10.1029/2006JD007350, 2007

Trace gas and particulate emissions from the 2003 southern California wildfires

J. Mühle

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

T. J. Lueker

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

Y. Su

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA

B. R. Miller

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

K. A. Prather

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, USA

R. F. Weiss

Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California, USA

Abstract

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 (CO₂), methane (CH₄), 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 CO₂ were calculated and showed a narrow age distribution, consistent with the short distance from the wildfires. ERs for N₂O and CH₃CCl₃ versus CO₂ were determined, but correlations were poor. No significant CH₂Cl₂ or CHCl₃ emissions were detected. CO₂ 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 CO₂ for the total burned area in southern California. Total CO₂, CH₄, C₂-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 CH₄, C₆H₆, 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.

Received 29 March 2006; accepted 3 October 2006; published 15 February 2007.

Keywords: biomass burning; trace gases; particle.

Index Terms: 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions (0426, 1610); 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry; 0428 Biogeosciences: Carbon cycling (4806); 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 1630 Global Change: Impacts of global change (1225).

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Citation: Mühle, J., T. J. Lueker, Y. Su, B. R. Miller, K. A. Prather, and R. F. Weiss (2007), Trace gas and particulate emissions from the 2003 southern California wildfires, J. Geophys. Res., 112, D03307, doi:10.1029/2006JD007350.

Copyright 2007 by the American Geophysical Union.