Ground and Airborne Aerosol Composition Measurements of California Coastal Chaparral Smoke Emissions

Friday, 19 December 2014
Jill S Craven1, Armin Sorooshian2, Scott P Hersey3, Andrew R Metcalf4, Katherine Schilling-Fahnestock1, Sally Newman5, Sheryl K Akagi6, Jonathan Taylor7, Gavin McMeeking8, Hugh Coe9, Ping Tang10, David R Cocker III10, Robert J Yokelson11, Richard C Flagan12 and John Seinfeld13, (1)California Institute of Technology, Pasadena, CA, United States, (2)University of Arizona, Tucson, AZ, United States, (3)North-West University, Geography and Environmental Management, Mahikeng, South Africa, (4)University of Minnesota Twin Cities, Minneapolis, MN, United States, (5)Caltech, Pasadena, CA, United States, (6)University of Montana, Missoula, MT, United States, (7)University of Manchester, Manchester, United Kingdom, (8)Droplet Measurement Technologies, Boulder, CO, United States, (9)University of Manchester, School of Earth, Atmospheric and Environmental Sciences, Manchester, M13, United Kingdom, (10)University of California Riverside, Chino, CA, United States, (11)University of Montana, Department of Chemistry, Missoula, MT, United States, (12)California Inst Technology, Pasadena, CA, United States, (13)California Inst Of Technology, Pasadena, CA, United States
Wildfire smoke has large local to global pollution impacts. We present aerosol composition data from two fires in southern California. We measured organic aerosol (OA) of nascent and aged (4 h) smoke from the Williams Fire during the 2009 airborne San Luis Obispo Biomass Burning Campaign (SLOBB). The net ΔOA/ΔCO2 decreased by ~20%; however, positive matrix factorization (PMF) analysis of the organic mass spectra supports two factors that enable the OA emissions to be separated into fresh and oxidized OA. The Δfresh BBOA/ΔCO2 had a steeper decline than the ΔOA/ΔCO2 consistent with outgassing of semi-voltile organic compounds (SVOCs) due to dilution, whereas the Δoxidized BBOA/ΔCO2 increased from its initial value, consist with formation of secondary organic aerosol (SOA). We compare these fresh and oxidized mass spectral signatures, along with chaparral smoke samples measured in the Missoula Fire Lab, to ground-based aerosol measurements made during the Station Fire that occurred one month earlier than the Williams Fire during the Pasadena Aerosol Characterization Observatory Campaign (PACO). Night and daytime aerosol smoke emissions were sampled for one week during the Station Fire. Daytime organic aerosol smoke emissions exhibited larger variability both in mass concentration and composition than nighttime smoke emissions. Both levoglucosan and potassium, known biomass burning tracers, were measured and had distinct time series, supporting diversity in the flaming vs. smoldering initial burning conditions. Similar to the Williams Fire, PMF of the Station Fire mass spectra also reveal two biomass burning factors, one that is less oxidized and correlates strongly with levoglucosan measurements and one that is heavily oxidized and correlates in time with the potassium signal. These two campaigns have allowed us to probe fresh and oxidized smoke in both night and daytime conditions, and PMF results have revealed that at least two emission factors are useful to describe OA smoke emissions.