Preparation, Characterization, and Scattering Characteristics of Mixed Aerosol of Fly Ash and Ammonium Sulfate

The mixed aerosols formed by fly ash and ammonium sulfate have a vital impact on the scattering characteristics of the atmosphere. This paper proposes to investigate the scattering characteristics of an individual optically levitated mixed aerosol of fly ash and ammonium sulfate using a coupled laser levitation and scattering measuring apparatus. The mixed aerosols were first prepared and characterized by multiple techniques. The results demonstrated that mixed aerosol particles completely encapsulated ammonium sulfate crystals on the rough porous surface of fly ash, resembling the “core-shell” structure. Moreover, the surface formed columnar ammonium sulfate crystals that exhibit the highest regularity when the solid mass concentration of fly ash was 1000 mg/L. The scattering intensity of mixed aerosols was measured, and the comparisons among fly ash aerosol and mixed aerosols were made to evaluate the effect of fly ash concentration on scattering. The measurements demonstrated that the mixed aerosols exhibited a lower overall scattering intensity compared to fly ash alone. The higher regularity of ammonium sulfate crystals formed on the surface of mixed aerosols at different solid mass concentrations of fly ash corresponds to higher scattering intensity. These findings will be helpful for recognizing the scattering characteristics of real atmospheric aerosols in depth.