1The University of Texas at Austin, Austin, Texas, USA
2Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
3Georgia Institute of Technology, Atlanta, Georgia, USA
4University of Patras, Patras, Greece
anow at: Phillips66®, Bartlesville, Oklahoma, USA
bnow at: TSI, Inc., Shoreview, Minnesota, USA
Received: 03 Nov 2014 – Discussion started: 12 Dec 2014
Abstract. Secondary organic aerosol (SOA) is transformed after its initial formation, but this chemical aging of SOA is poorly understood. Experiments were conducted in the Carnegie Mellon environmental chamber to form secondary organic aerosol (SOA) from the photo-oxidation of toluene and other small aromatic volatile organic compounds (VOCs) in the presence of NOx under different oxidizing conditions. The effects of the oxidizing condition on organic aerosol (OA) composition, mass yield, volatility, and hygroscopicity were explored. Higher exposure to the hydroxyl radical resulted in different OA composition, average carbon oxidation state (OSc), and mass yield. The OA oxidation state generally increased during photo-oxidation, and the final OA OSc ranged from −0.29 to 0.16 in the performed experiments. The volatility of OA formed in these different experiments varied by as much as a factor of 30, demonstrating that the OA formed under different oxidizing conditions can have a significantly different saturation concentration. There was no clear correlation between hygroscopicity and oxidation state for this relatively hygroscopic SOA.
Revised: 05 Jun 2015 – Accepted: 05 Jul 2015 – Published: 24 Jul 2015
Hildebrandt Ruiz, L., Paciga, A. L., Cerully, K. M., Nenes, A., Donahue, N. M., and Pandis, S. N.: Formation and aging of secondary organic aerosol from toluene: changes in chemical composition, volatility, and hygroscopicity, Atmos. Chem. Phys., 15, 8301-8313, doi:10.5194/acp-15-8301-2015, 2015.