Scattering Matrix for Typical Urban Anthropogenic Origin Cement Dust and Discrimination of Representative Atmospheric Particulates

Abstract

The complete scattering matrix for cement dust was measured as a function of scattering angle from 5° to 160° at a wavelength of 532 nm, as a representative of mineral dust of anthropogenic origin in urban areas. Other related characteristics of cement dust, such as particle size distribution, chemical composition, refractive index, and micromorphology, were also analyzed. For this objective, a newly improved apparatus was built and calibrated using water droplets. Measurements of water droplets were in good agreement with Lorenz‐Mie calculations. To facilitate the direct applicability of measurements for cement dust in radiative transfer calculation, the synthetic scattering matrix was computed and defined over the full scattering angle range from 0° to 180°. The scattering matrices for cement dust and typical natural mineral dusts were found to be similar in trends and angular behaviors. Angular distributions of all matrix elements were confined to rather limited domains. To promote the application of light‐scattering matrix in atmospheric observation and remote sensing, discrimination methods for various atmospheric particulates (cement dust, soot, smolder smoke, and water droplets) based on the angular distributions of their scattering matrix elements are discussed. The ratio −F12/F11 proved to be the most effective discrimination method when a single matrix element is employed; aerosol identification can be achieved based on −F12/F11 values at 90° and 160°. Meanwhile, the combinations of −F12/F11 with F22/F11 (or (F11 − F22)/(F11 + F22)) or −F12/F11 with F44/F11 at 160° can be used when multiple matrix elements at the same scattering angle are selected.

Assessing Superspheroids in Modeling the Scattering Matrices of Dust Aerosols

“…Laboratory measurements are an important approach for obtaining characteristics of realistic dust aerosols' scattering matrix properties. A number of experiments that have been conducted have addressed this subject (e.g., Liu et al, ; Muñoz et al, ; Volten et al, ; Wang et al, ). Although the shapes and structures of dust particles were too complicated and differed from region to region, the light scattering property results obtained from experiments may provide a valuable reference for building a dust aerosol model.…”

“…Particles with identical or close aspect ratios can have diverse shapes. Particularly, particles with a unity aspect ratio can be irregular (Gao & Anderson, 2001;Liu et al, 2018;Muñoz et al, 2001;Okada et al, 2001;Reid et al, 2003). The fact that the spheroid with a unity aspect ratio is a sphere makes it preferable to use large aspect ratios in modeling dust optical properties.…”

“…Journal of Geophysical Research: Atmospheres subject (e.g., Liu et al, 2018;Muñoz et al, 2012;Volten et al, 2006;Wang et al, 2015). Although the shapes and structures of dust particles were too complicated and differed from region to region, the light scattering property results obtained from experiments may provide a valuable reference for building a dust aerosol model.…”

An experimental study on light scattering matrices for Chinese loess dust with different particle size distributions

“…At last, whether measurement results of scattering matrix satisfy Cloude coherency matrix test should be examined (Hovenier and Van Der Mee, 1996). For more details, it can be referred to Muñoz et al (2010) and Liu et al (2018).…”

“…A dust generator (RBG 1000; Palas) was applied to disperse loess particles (Liu et al, 2018). Dust particles were 170 transmitted to scattering zone by airstream and some particles in each loess sample were sprayed to different vessels for subsequent size analyses.…”