AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Impacts of Oxidation Processes on Complex Refractive Index of SOA Generated from Isoprene
TOMOKI NAKAYAMA, Kei Sato, Takashi Imamura, Yutaka Matsumi, ISEE, Nagoya University
Abstract Number: 658 Working Group: Effects of NOx and SO2 on BVOC Oxidation and Organic Aerosol Formation
Abstract Isoprene is the most abundant volatile organic compound emitted from the biosphere and is known as one of the important precursors of secondary organic aerosol (SOA) in the atmosphere. The formation yield of the isoprene-SOA is considered to be enhanced in the presence of acidic seed particles, such as sulfuric acid. Recently, we have reported the wavelength-dependent complex refractive index (RI) values for the SOA generated during photooxidation of isoprene in the presence of NOx and SO2 [Nakayama et al. (2015)]. However, the impacts of oxidation processes on the RI values of isoprene-SOA are still unclear. In this work, the wavelength-dependent complex RI values of the SOA generated in the oxidation of isoprene with OH, NO3, and O3 in the presence or absence of SO2 have been examined, based on smog chamber experiments with photoacoustic and cavity ring-down spectrometers. As results, significant imaginary part (k) values of RI at <532 nm are obtained for the SOA generated in the OH oxidation in the presence of SO2, while the k values are smaller for the SOA generated in the ozonolysis (in the presence of OH scavenger) and are negligible for the SOA generated in the NO3 oxidation, even in the presence of SO2. In the presentation, relationship with chemical properties will also be discussed.
Reference: Nakayama et al., "Complex refractive index of secondary organic aerosol generated from isoprene/NOx photooxidation in the presence and absence of SO2", J. Geophys. Res. Atmos., 120, 7777-7787 (2015).