Identification and particle sizing of submicron mineral dust by using complex forward-scattering amplitude data

An accurate observational dataset of the size-resolved concentration of mineral dust particles in the atmosphere, hydrosphere, and cryosphere is needed for investigating the effect of mineral dust on the climate with earth system models. However, automated measurements of dust particles remain challenging due to the complexities of the physicochemical properties (e.g., shape and mineralogy) of individual dust particles and the difficulties in discriminating dust from other particulate components (e.g., black carbon). Here, we suggest the use of complex forward-scattering amplitude data obtained by the single particle extinction and scattering (SPES) method as a low-cost optical approach for identification and quantification of silicate (aluminosilicates + quartz) particles, the major particulate component of desert dust. We focus here on the submicron particle-size range to challenge the robust identification of wavelength or smaller scale dust solely according to the principle of elastic light scattering. The two-dimensional nature of the complex scattering amplitude data allows us to identify silicate-dominant particles in waterborne dust samples and discriminate them from light-absorbing particulate components (e.g., hematite). We demonstrate that the two-dimensional dataspace of the complex amplitude allows an accurate retrieval of the particle-size distribution of silicate particles thanks to the simultaneous retrieval of the particle’s effective refractive index. We discuss some notable differences in our results from those retrieved from conventional elastic light scattering approaches.Copyright © 2022 American Association for Aerosol Research