Simultaneous measurement of light-scattering properties and particle size distribution for aerosols: Application to ammonium sulfate and quartz aerosol particles

An apparatus for measuring the scattering phase function and linear polarization of aerosol particles has been developed. The apparatus uses an elliptical mirror and CCD camera to image the full angular scattering range simultaneously. An in-line aerodynamic particle sizer (APS) in the particle flow stream provides for the simultaneous measurement of the aerosol particle size distribution. This apparatus allows for a comparison of measured optical properties with theoretical model calculations based on the measured aerosol size distribution. The system was calibrated and tested using monodisperse polystyrene latex (PSL) spheres and with ammonium sulfate (AS) aerosol. We have also used the apparatus for measuring the scattering phase function and linear polarization for light scattering from irregular quartz aerosol particles. Our results show that Mie theory substantially overestimates the backscattering cross-section for quartz particles in the size parameter range X∼2–4, in agreement with previous experimental work and theoretical modeling studies. We also present a normalized synthetic phase function for quartz dust aerosol in the accumulation mode size range (0.1–2.0 μm).