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
- 1State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Resources Utilization and Protection, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China
- 2South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, PR China
- 3Graduate University of Chinese Academy of Sciences, Beijing 100049, PR China
- 4State Environmental Protection Key Laboratory of Regional Air Quality Monitoring, Guangdong Environmental Monitoring Center, Guangzhou 510308, PR China
- 5Atmospheric Environment Institute of Safety and Pollution Control, Jinan University, Guangzhou 510632, PR China
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.