AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
O3- and NO3-Initiated Aging of Toluene Secondary Organic Aerosol
SATHIYAMURTHI RAMASAMY, Tomoki Nakayama, Takashi Imamura, Kei Sato, National Institute for Environmental Studies, Japan
Abstract Number: 755 Working Group: Aerosol Chemistry
Abstract Formation of secondary organic aerosol (SOA) and aging by OH radicals are covered in the widely-used volatility-basis set (VBS) model. However, night time aging of SOA by NO3 radicals and O3 is excluded in this model. We examined the aging of aerosol formed from OH oxidation of toluene by NO3 radicals and O3. Laboratory experiments were carried out in a 6 m3 smog chamber. OH radicals required for toluene oxidation were generated either by the photolysis of H2O2 or by the ozonolysis of tetramethylethylene (TME). N2O5, O3 and NO2 were injected in dark condition after the level of formed SOA became stable to study the aging. From N2O5 injection NO3 radicals was produced along with NO2. During experiments, FT-IR spectrometer and proton transfer quadrupole ion guide time-of-flight mass spectrometer (PTR-QiTOF) were used to measure gaseous reactants and products in real time. AMS and SMPS were used to monitor the SOA formation. Our results showed that only after the injection of N2O5, SOA and nitrate aerosol increased. Similar results were obtained in both H2O2 photolysis and TME ozonolysis experiments. PTR-QiTOF result showed that cresol was degraded completely after the injection of N2O5 and gaseous methylbenzoquinones and nitorocresols were produced. No clear increase was observed in SOA concentration after the injection of ozone or NO2. From these results, it is obvious that night time aging by NO3 radical is important for toluene oxidation.