AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Chemical Composition Changes in Biomass Burning Organic Aerosol from FLAME-IV Perturbation Experiments
ELLIS SHIPLEY ROBINSON, Daniel S. Tkacik, Rawad Saleh, Adam Ahern, Albert A. Presto, Ryan Sullivan, Robert J. Yokelson, Allen Robinson, Neil Donahue, Carnegie Mellon University
Abstract Number: 685 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Biomass Burning Organic Aerosol (BBOA) is a major contributor to atmospheric primary fine particles, and gas-phase emissions from biomass burning are a significant source of to the global burden of trace gases. Despite their significance, however, the light absorbing properties, downwind chemical evolution, and secondary particulate mass enhancement of these emissions are poorly understood.
We present chemical composition measurements from a High-Resolution Aerosol Mass Spectrometer (HR-AMS) of two-chamber, smog chamber perturbation experiments at the FLAME-IV campaign in Missoula, Montana. In most experiments, we filled two smog chambers with emissions from the same fire, and then perturbed one chamber by adding an atmospheric oxidant (e.g. hydroxyl radical, ozone, HONO, lights). This allowed for a characterization of any changes (e.g. increase in O:C ratio, increase in organonitrates) in the primary emissions, as well as the composition change from the perturbation. Additionally, as burn-to-burn variability can be large, even between burns of the same fuel, the two-chamber method represents a way to control for this and focus on the changes in composition, mass enhancement, and light absorption for a given perturbation. We also present the absorptivity of BBOA as a function of the fraction of primary (fresh) OA to total OA, fraction of organonitrates to total OA, fraction of large molecular weight fragments (Th > 100) to total OA, and the OA-to-BC ratio.