Complex refractive index of secondary organic aerosol generated from isoprene/NOx photooxidation in the presence and absence of SO2. Issue 15 (10th August 2015)

• Record Type: Journal Article
• Authors: Nakayama, Tomoki; Sato, Kei; Tsuge, Masashi; Imamura, Takashi; Matsumi, Yutaka
• Is Part Of: Journal of geophysical research. Volume 120:Issue 15(2015:Aug.)
• Page Start: 7777
• Page End: 7787
• Publication Date: 2015-08-10
• Subjects: Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1002/2015JD023522
• Languages: English
• ISSNs: 2169-897X

Abstract

<abstract abstract-type="main" id="jgrd52340-abs-0001"> <title>Abstract</title> <p id="jgrd52340-para-0001">We report the first measurements of the complex refractive index (RI) at 375, 405, 532, and 781 nm for secondary organic aerosol (SOA) generated from isoprene/NO_x photooxidation. At all wavelengths studied, slightly greater real components of the RI were observed for the SOA generated in the absence of SO₂ compared with those generated in its presence. Considering the chemical properties, the differences in the oxidation state and/or ratio of particle density to molecular weight of compounds in the SOA are considered to be the main factors determining the real components. The imaginary components at ≤532 nm were found to increase with increasing initial SO₂ concentration. The highly conjugated oligomers are suggested to be plausible chromophore candidates. This study suggests that when large amounts of SOA are generated after mixing of isoprene with NO_x and SO_x, light absorption of these SOAs may compete with that of black carbon, especially at ultraviolet wavelengths.</p> </abstract>