Evolution of the Complex Refractive Index of Secondary Organic Aerosols during Atmospheric Aging.
Environ Sci Technol
; 52(6): 3456-3465, 2018 03 20.
Article
em En
| MEDLINE
| ID: mdl-29461820
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 ß-pinene and p-xylene SOA produced and aged in an oxidation flow reactor, simulating daytime aging under NO x-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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Refratometria
Idioma:
En
Ano de publicação:
2018
Tipo de documento:
Article