Secondary organic aerosol formation from the OH-initiated oxidation of guaiacol under different experimental conditions

Abstract

Guaiacol (2-methoxyphenol) has a high emission rate from wood burning and mainly exists in the gas phase, but the formation potential of secondary organic aerosol (SOA) from the atmospheric oxidation of guaiacol has not been well determined yet. In this work, SOA formation from the gas-phase reaction of guaiacol with OH radicals was investigated using an oxidation flow reactor (OFR) under different experimental conditions. The results showed that SOA yield was dependent on guaiacol concentration, OH exposure, and the presence of SO2 and NO2. SOA yield firstly increased and then decreased as a function of OH exposure. The maximum SOA yield (0.28–0.54) obtained at different guaiacol concentrations could be well-expressed by a one-product model. The SOA oxidation degree was represented by the carbon oxidation state (OSC) and f44/f43 (the ratio of organic mass fractions of m/z 44 to m/z 43), which both increased linearly and significantly with the increase of OH exposure. In addition, SO2 and NO2 promoted SOA formation, for which the maximum yield enhancements were 13.38% and 10.69%, respectively. The N/C ratio (0.034–0.045) indicated that NO2 participated in the OH-initiated reaction of guaiacol, consequently resulting in the formation of organic nitrates. The experimental results would be helpful to further the understanding of SOA formation from the atmospheric oxidation of guaiacol and its subsequent impacts on air quality and climate.