AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
SOA Formation from the Aqueous-phase Reactions of Phenolic Compounds
QI ZHANG, Lu Yu, Jeremy Smith, Cort Anastasio, Alexander Laskin, University of California, Davis
Abstract Number: 435 Working Group: Aerosol Chemistry
Abstract Phenolic compounds are emitted in significant amounts from biomass burning and can undergo fast aqueous-phase reactions to form secondary organic aerosol (SOA) with mass yields of ~ 100% (Smith et al., ES&T, 2014). In this study, we investigate the aqueous-phase reactions of three phenols (phenol, guaiacol and syringol) with two oxidants - excited triplet states of carbonyls (3C*) and hydroxyl radical (OH) under atmospheric relevant conditions. The low volatility products of these reactions were thoroughly characterized using high-resolution aerosol mass spectrometry (HR-AMS), ion chromatography (IC), and high resolution electrospray mass spectrometry (ESI-MS). The evolution of phenolic SOA as a function of photochemical age was studied using a newly developed online experimental approach. Our results indicate that aqueous-phase reactions of phenols mainly involve polymerization, hydroxylation, carbonylation, esterification, and various fragmentation processes including aromatic ring opening and loss of methoxy groups. The atomic oxygen-to-carbon ratio (O/C) of the SOA increased over the course of phototransformations, more rapidly at the beginning, and achieved a value of 1 - 1.2 after simulated sunlight illumination equivalent to multiple days of tropospheric exposure. The first generation products included dimers and hydroxylated monomers, which were later transformed to higher-order oligomers and highly oxygenated monomeric and oligomeric derivatives. As the photoreactions continued, ring opening processes became more dominant and the fragmentation was accompanied with a gradual decrease of SOA mass.