Measurements of trace gases and particles in fresh and aged smoke from a chaparral fire in California

Abstract

On November 17th 2009 we used a Twin Otter aircraft outfitted with an airborne Fourier transform infrared spectrometer (AFTIR), aerosol mass spectrometer (AMS), single particle soot photometer (SP2), nephelometer, Licor CO2 analyzer, and a chemiluminescence ozone instrument to measure the initial emissions from a 100 hectare prescribed fire in chaparral fuels on the central coast of California, U.S.A. We also measured the post emission chemical changes in the isolated downwind plume for a distance corresponding to about 4.5 hours of smoke aging. The light scattering to CO2 ratio increased by a factor of ~2.7 over 4 hours: similar to observations in a biomass burning plume in Mexico where significant secondary formation of organic aerosol (OA) was confirmed by AMS. However, in the California plume, a decrease in OA was observed by AMS along with a concurrent increase in the fraction of thickly coated particles as measured by the SP2. Decreasing OA accompanied by increased scattering/coating may be explained by a combination of coagulation and evaporation processes. The latter may have been promoted in the California plume because it diluted in a 'clean,' low relative humidity (11-26%) environment compared to the Mexican plume. AFTIR measured significant changes in gas phase constituents.

Citation

Akagi, S. K.; Craven, J. S.; Taylor, J. W.; McMeeking, G. R.; Yokelson, R. J.; Burling, I. R.; Alvarado, M. J.; Seinfeld, J.; Coe, H.; Urbanski, S. P. 2010. Measurements of trace gases and particles in fresh and aged smoke from a chaparral fire in California. American Geophysical Union. Fall Meeting: Abstract #A21B-0041.