Articles | Volume 16, issue 4
https://doi.org/10.5194/acp-16-2631-2016
https://doi.org/10.5194/acp-16-2631-2016
Research article
 | 
03 Mar 2016
Research article |  | 03 Mar 2016

The real part of the refractive indices and effective densities for chemically segregated ambient aerosols in Guangzhou measured by a single-particle aerosol mass spectrometer

Guohua Zhang, Xinhui Bi, Ning Qiu, Bingxue Han, Qinhao Lin, Long Peng, Duohong Chen, Xinming Wang, Ping'an Peng, Guoying Sheng, and Zhen Zhou

Abstract. Knowledge on the microphysical properties of atmospheric aerosols is essential to better evaluate their radiative forcing. This paper presents an estimate of the real part of the refractive indices (n) and effective densities (ρeff) of chemically segregated atmospheric aerosols in Guangzhou, China. Vacuum aerodynamic diameter, chemical compositions, and light-scattering intensities of individual particles were simultaneously measured by a single-particle aerosol mass spectrometer (SPAMS) during the fall of 2012. On the basis of Mie theory, n at a wavelength of 532 nm and ρeff were estimated for 17 particle types in four categories: organics (OC), elemental carbon (EC), internally mixed EC and OC (ECOC), and Metal-rich. The results indicate the presence of spherical or nearly spherical shapes for the majority of particle types, whose partial scattering cross-section versus sizes were well fitted to Mie theoretical modeling results. While sharing n in a narrow range (1.47–1.53), majority of particle types exhibited a wide range of ρeff (0.87–1.51 g cm−3). The OC group is associated with the lowest ρeff (0.87–1.07 g cm−3), and the Metal-rich group with the highest ones (1.29–1.51 g cm−3). It is noteworthy that a specific EC type exhibits a complex scattering curve versus size due to the presence of both compact and irregularly shaped particles. Overall, the results on the detailed relationship between physical and chemical properties benefits future research on the impact of aerosols on visibility and climate.

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Short summary
This paper first presents an estimate of the real part of the refractive indices and effective densities of chemically segregated aerosols in China. The results indicate the presence of spherical or nearly spherical shape for the majority of particle types. While sharing refractive index in a narrow range (1.47–1.53), they exhibited a wide range of effective density (0.87–1.51). Detailed relationship between physical and chemical properties benefits future research on visibility and climate.
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