AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
SOA Formation from Toluene Oxidation in the Presence of NOx: The Importance of Relative Humidity
DAO HUANG, Yunle Chen, Steve Kim, Nga Lee Ng, Zhejiang University
Abstract Number: 189 Working Group: Aerosol Chemistry
Abstract Toluene is one of the most important anthropogenic volatile organic compounds (VOCs). Many studies have shown that toluene is one of the most abundant aromatic VOCs in urban areas, and can contribute a large fraction of secondary organic aerosol (SOA) in urban areas and even some rural areas. However, in the past decade, knowledge about toluene SOA in the presence of NOx is limited to SOA yield curve under dry conditions and only scattered yields are available under humid conditions. Little is known about toluene SOA composition and the effects of relative humidity (RH) on SOA yields and composition. In the present work, a series of experiments on photo-oxidation of toluene under dry (RH<3%) and humid (RH=~40% and ~70%) conditions were performed in the Georgia Tech Environmental Chamber facility (GTEC) to investigate toluene SOA composition and RH effects. In situ photolysis of HONO was used as OH radical and NOx sources. Ammonium sulfate was used as seed aerosol. Particles were chemically characterized using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a high-resolution chemical ionization time-of-flight mass spectrometer coupled with a filter inlet for gas and aerosol (FIGAERO-CIMS). Simultaneously, gas-phase compounds were determined by CIMS. Based on experimental results, we obtained different yield curves as a function of organic aerosol (ΔMo) at various RH and compared particle-phase composition under dry and humid conditions. RH affects SOA formation and composition under specific reaction conditions. This study provides new insights for understanding SOA and haze formation in the polluted atmosphere under different humidity conditions.