HR: 0800h
AN: A51C-0792    [Abstracts]
TI: Trace gas and Particulate Emissions From the 2003 Southern California Wildfires
AU: * M\"{u}hle, J
EM: jens@gaslab.ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244 United States
AU: Su, Y
EM: yxsu@ucsd.edu
AF: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0314 United States
AU: Lueker, T J
EM: tlueker@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244 United States
AU: Miller, B R
EM: brmiller@ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244 United States
AU: Prather, K A
EM: kprather@ucsd.edu
AF: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093-0314 United States
AU: Weiss, R F
EM: rfweiss@gaslab.ucsd.edu
AF: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0244 United States
AB: Thirteen major wildfires in Southern California, fanned by warm and dry Santa Ana winds in late October 2003, had a large impact on atmospheric chemistry and air quality in an urban area populated by $\sim$20 million people. To quantify some of the atmospheric effects of these wildfires, which burned over 300,000 hectares of mainly chaparral and woodlands, continuous in-situ trace gas and particle measurements were carried out at our laboratories in La Jolla. During the fires we observed elevated levels of non-methane hydrocarbons and methyl halides with up to $\sim$8 ppb C$_{2}$H$_{2}$, $\sim$25 ppb C$_{2}$H$_{4}$, $\sim$42 ppb C$_{2}$H$_{6}$, $\sim$9.2 ppb C$_{6}$H$_{6}$, $\sim$2 ppb C$_{7}$H$_{8}$, and $\sim$2.6 ppb CH$_{3}$Cl (all GC/MSD). In addition, up to $\sim$4 ppm CH$_{4}$ (GC/FID), $\sim$476 ppm CO$_{2}$ (NDIR), and a concomitant reduction of O$_{2}$/N$_{2}$ ratios (fuel cell oxygen analyzer) were observed together with a high degree of correlation among all species. The tightest correlations were observed for compounds typically emitted by the smoldering phase of a fire. Emission ratios relative to C$_{2}$H$_{6}$ ($\Delta$X/$\Delta$C$_{2}$H$_{6}$) in mol/mol were 0.64$\pm$0.01 for C$_{2}$H$_{4}$ (r$^{2}$ = 0.97), 0.172$\pm$0.003 for C$_{6}$H$_{6}$ (r$^{2}$ = 0.97), 0.0484$\pm$0.0006 for CH$_{3}$Cl (r$^{2}$ = 0.98), and 45.0$\pm$1.6 for CH$_{4}$ (r$^{2}$ = 0.91). Although correlations of these gases with CO$_{2}$ show more scatter, they provide a mechanism for quantifying trace gas fluxes relative to the amount of biomass burned. Additionally, on-line real-time measurements of the concentrations of particles with scanning mobility particle sizer (SMPS, 0.01-0.3 $\mu$m) and aerodynamic particle sizer (APS, 0.54-2.46 $\mu$m) showed a high degree of correlation with trace gases mixing ratios as well, pointing to the wildfires as the common source. The chemical compositions of individual aerosol particles determined by an aerosol time-of-flight mass spectrometer (ATOFMS) confirmed that $\sim$70 % of particles in the 0.05-1 $\mu$m aerodynamic diameter range had typical biomass burning signatures with levoglucosan and high potassium contents. Levels of particulate matter with aerodynamic diameters $\le$2.5 $\mu$m (PM$_{2.5}$), which are according to the EPA closely associated with the aggravation of heart and lung diseases, were determined from the concentration of particles assuming spherical particles of 1.2 g/cm$^{3}$, and the EPA 24-hour limit for PM$_{2.5}$ of 65 $\mu$g/m$^{3}$ was considerably exceeded during two 24 hour periods with values up to $\sim$250 $\mu$g/m$^{3}$.
DE: 1610 Atmosphere (0315, 0325)
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0315 Biosphere/atmosphere interactions
DE: 0345 Pollution--urban and regional (0305)
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting