10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Secondary Organic Aerosol Formation from Methylfurans by Nitrate Radical Oxidation
TAEKYU JOO, Masayuki Takeuchi, Matthew Alvarado, Nga Lee Ng, Georgia Institute of Technology
Abstract Number: 1125 Working Group: Aerosol Chemistry
Abstract An important activity that contributes to both primary organic aerosol (POA) and secondary organic aerosol (SOA) formation is biomass burning. Recent studies about biomass burning SOA formation demonstrate that a large fraction of SOA is produced from an unidentified pathway. These studies suggest an important contribution of nontraditional precursors to SOA formation from biomass burning, such as furan derivatives. Methylfurans are one of the main furan derivatives that are emitted by biomass burning. However, our current understanding of SOA formation from methylfurans is extremely limited, and even less attention has been paid to nighttime oxidation of this class of compounds from biomass burning activities. Here, we investigate SOA formation from 2- and 3-methylfuran by nitrate radical (NO3) oxidation at the Georgia Tech Environmental Chamber (GTEC) facility. NO3 is formed from NO2 + O3 reaction, and NO3 subsequently reacts with NO2 to make N2O5. The VOC:N2O5 ratio was set around 1:4 to ensure peroxy radicals react with NO3. Oxidation products were measured in real-time with High Resolution Time-of-Flight Chemical Ionization Mass Spectrometer (HR-ToF-CIMS) coupled with a Filter Inlet for Gases and AEROsols (FIGAERO). This setup allows the measurement of both gas- and particle-phase composition during the oxidation process. A High Resolution-Time of Flight-Aerosol Mass Spectrometer (HR-ToF-AMS) was deployed to measure the bulk elemental composition of SOA. The VOC decay was measured with Gas Chromatography Flame Ionization Detector (GC-FID) and the increase of aerosol mass concentration was measured with a Scanning Mobility Particle Sizer (SMPS). Aerosol mass continued to increase after all 2- and 3-methylfuran were consumed, indicating a large contribution of higher-generation oxidation products to SOA. Organic nitrate (RONO2) contribution was around 10-15% to the total organics measured by HR-ToF-AMS. Multiple monomer and dimer species that contain an -ONO2 functional group were also detected by FIGAERO-ToF-CIMS. These results indicate that the RONO2 species are also important in terms of SOA formation, which have not yet been considered in 2- and 3-methylfuran SOA studies to date.