10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Ultraviolet and Visible Complex Refractive Indices of Secondary Organic Aerosol Produced by Photooxidation of β-pinene and Naphthalene in the Presence of Nitrogen Oxides
QUANFU HE, Chunlin Li, Yinon Rudich, Weizmann Institute of Science
Abstract Number: 990 Working Group: Aerosol Chemistry
Abstract Atmospheric aerosols strongly influence Earth’s energy budget by aerosol-radiation interactions and aerosol-cloud interactions. A large fraction of the submicron aerosols in the troposphere consists of organic aerosol components, of which a large portion is secondary organic aerosols (SOA) originated from biogenic and anthropogenic volatile organic compounds (VOCs). However, the optical properties of SOA are still poorly constrained.
The optical properties of SOA can vary as a function of wavelength, and change with SOA chemical composition. In the real ambient, VOCs are typically mixed with anthropogenic pollutants (e.g. nitrogen oxides, NOx). The addition of NOx during SOA formation introduces alternative oxidation mechanisms, thus modifies the SOA chemical composition and potentially changes the SOA optical properties.
In this study, we produced SOA from β−pinene and naphthalene in the presence of NOx with controlled exposure time in an oxidation flow reactor. The chemical composition of the SOA was characterized by a high-resolution time-of-flight aerosol mass spectrometer. Light extinction data in the ultraviolet-visible range (315-650 nm) measured by a broadband cavity enhanced spectroscopy (BBCES) were obtained. Changes in the complex refractive index due to chemical composition evolution caused by different NOx/VOCs ratios will be investigated. Moreover, the influence of photochemical aging on the SOA optical properties for SOA produced in the presence of NOx will be addressed.