10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Secondary Organic Aerosol Formation of OH and NO3 Initiated Reactions of 1,3-Benzenediol
ZACHARY FINEWAX, Joost de Gouw, Paul Ziemann, University of Colorado
Abstract Number: 1609 Working Group: Aerosol Chemistry
Abstract Biomass burning is the second largest emission source of volatile organic compounds (VOCs) and largest of particulate matter (PM) globally. Previous studies measuring emissions from biomass burning have identified 1,3-benzenediol (resorcinol), a semi-volatile organic compound (SVOC) emitted as a pyrolysis product of lignin, a biopolymer found in wood. To date, there have been no studies on the gas-phase oxidation of this compound, which may be an important precursor for secondary organic aerosol (SOA) from biomass burning.
To study the reactions of resorcinol that could occur in a biomass burning plume, OH and NO3 radical-initiated reactions (simulating daytime and nighttime, respectively) of resorcinol in the presence of NOx were conducted in an 8 m3 FEP Teflon environmental chamber operated in batch mode. OH radical-initiated reactions were performed by photolysis of methyl nitrite (CH3ONO) in the presence of NO by blacklights, and NO3 radical-initiated reactions were performed by thermal decomposition of N2O5. Because of the low volatility of resorcinol and thus potential for loss to the chamber walls, studies of the gas-phase chemistry were conducted by adding resorcinol while photolysis of CH3ONO or thermal decomposition of N2O5 was already occurring in the chamber. This allowed for reaction to occur prior to wall loss because of the high reactivity of resorcinol with both oxidants. SOA produced by these reactions was measured with a thermal desorption particle beam mass spectrometer (TDPBMS) and scanning mobility particle sizer (SMPS), and was collected on Teflon filters to quantify the SOA yield. The gas-phase compounds were measured and quantified by Proton-Transfer-Reaction Mass Spectrometry (PTR-MS) and collection onto denuders to quantify VOCs, and SVOCs that exist in both the particle and gas-phase. Molecular identification and quantification was conducted by high-performance liquid chromatography (HPLC) and chemical ionization ion trap mass spectrometry (CI-ITMS) on SOA filter and denuder extracts through the use of commercially available and authentic standards collected from HPLC fractions.
SOA and molecular yield calculations assumed complete reaction of the added resorcinol, which is appropriate given the calculated kinetics of resorcinol reactions with OH and NO3 radicals, and the expected much longer timescale for vapor wall loss in the environmental chamber. The product distribution of the SOA from OH-initiated reactions is dominated by 1,2,3-benzenetriol and 1,2,4-benzenetriol, with minor contributions from benzenetetraols, 5-nitro-1,2,3-benzenetriol, and nitroresorcinol isomers. In the OH radical reaction, hydroxybenzoquinone and dihydroxybenzoquinone are generated as gas-phase products both by gas-phase reaction and multiphase chemistry involving oxidation of benzenetriols and benzenetetraols by nitric acid. This was determined through additions of ammonia, and monitoring the reduced loss of benzenetriols from the particle phase. The SOA mass yield of 0.61 for the OH radical-initiated reaction was over a factor of 2 higher than the yield of 0.27 from the NO3 radical-initiated reactions, while the products were 4-nitroresorcinol, 2-nitroresorcinol, and hydroxybenzoquinone. The presence of nitroresorcinol in both the gas-phase and particle-phase indicate that these compounds are semivolatile. The results of this study highlight the importance of resorcinol oxidation to SOA formation during the day compared to at night.