AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Composition and Volatility of the Aerosol Products of Reactions of Catechol, an Important Biomass Burning Emission, with Hydroxyl and Nitrate Radicals
ZACHARY FINEWAX, Paul Ziemann, Joost de Gouw, University of Colorado
Abstract Number: 469 Working Group: Aerosol Chemistry
Abstract Biomass burning emits a complex mixture of gas and particle phase organic compounds into the atmosphere that affect climate, visibility and air quality. Because biomass burning is not only a large source of primary organic aerosol, but also a potential source for secondary organic aerosol (SOA) precursors, it is important to determine the mechanisms by which SOA is formed from the volatile organic compounds emitted. Catechol, a dihydroxybenzene isomer, is emitted from wood burning (likely as a product of lignin pyrolysis), and although modeling studies have identified it as a potentially significant SOA precursor, its ability to form SOA had not yet been thoroughly investigated in the laboratory. In the studies described here, catechol was introduced into an 8000 L environmental chamber composed of PTFE Teflon and reacted with hydroxyl (OH) radicals in the presence of NOx and with nitrate (NO3) radicals, under dry conditions. Gas- and particle-phase products were analyzed using real-time and offline mass spectrometry as well as gas and liquid chromatography. Both reactions form SOA in high yields, with 4-nitrocatechol being the major product. Measurements of the vapor pressure of 4-nitrocatechol conducted using temperature-programmed thermal desorption particle beam mass spectrometry indicate that at typical atmospheric aerosol loadings this product will be semi-volatile and thus present in both the gas and particle phase, consistent with observations from biomass burning affected regions of the atmosphere. The mechanism of catechol oxidation differs from that of non-oxygenated aromatic compounds, as evidenced by the SOA composition and product yields.