Evolution of the Complex Refractive Index of Secondary Organic Aerosols during Atmospheric Aging

Quanfu He, Nir Bluvshtein, Lior Segev, Daphne Meidan, J. Michel Flores, Steven S. Brown, William Brune, Yinon Rudich

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

The wavelength-dependence of the complex refractive indices (RI) in the visible spectral range of secondary organic aerosols (SOA) are rarely studied, and the evolution of the RI with atmospheric aging is largely unknown. In this study, we applied a novel white light-broadband cavity enhanced spectroscopy to measure the changes in the RI (400-650 nm) of β-pinene and p-xylene SOA produced and aged in an oxidation flow reactor, simulating daytime aging under NOx-free conditions. It was found that these SOA are not absorbing in the visible range, and that the real part of the RI, n, shows a slight spectral dependence in the visible range. With increased OH exposure, n first increased and then decreased, possibly due to an increase in aerosol density and chemical mean polarizability for SOA produced at low OH exposures, and a decrease in chemical mean polarizability for SOA produced at high OH exposures, respectively. A simple radiative forcing calculation suggests that atmospheric aging can introduce more than 40% uncertainty due to the changes in the RI for aged SOA.

Original languageEnglish (US)
Pages (from-to)3456-3465
Number of pages10
JournalEnvironmental Science and Technology
Volume52
Issue number6
DOIs
StatePublished - Mar 20 2018

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

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