Evolution of trace gases and particles emitted by a chaparral fire in California
Atmospheric Chemistry and Physics Discussions
Biomass burning (BB) is a major global source of trace gases and particles. Accurately representing the production and evolution of these emissions is an important goal for atmospheric chemical transport models. We measured a suite of gases and aerosols emitted from an 81 hectare prescribed fire in chaparral fuels on the central coast of California, US on 17 November 2009. We also measured physical and chemical changes that occurred in the isolated downwind plume in the first ∼4 h after
... ∼4 h after emission. The measurements were carried out onboard a Twin Otter aircraft outfitted with an airborne Fourier transform infrared spectrometer (AFTIR), aerosol mass spectrometer (AMS), single particle soot photometer (SP2), nephelometer, LiCor CO 2 analyzer, a chemiluminescence ozone instrument, and a wingmounted meteorological probe. Our measurements included: CO 2 ; CO; NO x ; NH 3 ; non-methane organic compounds; organic aerosol (OA); inorganic aerosol (nitrate, ammonium, sulfate, and chloride); aerosol light scattering; refractory black carbon (rBC); and ambient temperature, relative humidity, barometric pressure, and three-dimensional wind velocity. The molar ratio of excess O 3 to excess CO in the plume ( O 3 / CO) increased from −5.13 (±1.13) × 10 −3 to 10.2 (±2.16) × 10 −2 in ∼4.5 h following smoke emission. Excess acetic and formic acid (normalized to excess CO) increased by factors of 1.73 ± 0.43 and 7.34 ± 3.03 (respectively) over the same time since emission. Based on the rapid decay of C 2 H 4 we infer an in-plume average OH Published by Copernicus Publications on behalf of the European Geosciences Union. 1398 S. K. Akagi et al.: Evolution of trace gases and particles and suggest that differences in environmental factors such as smoke concentration, oxidant concentration, actinic flux, and RH contribute significantly to the variation in plume evolution observations.