Measurement of Aerosol Optical Properties by Integrating Cavity Ring-Down Spectroscopy and Nephelometry

Abstract

Abstract : We measure scattering coefficient, extinction coefficient, scattering cross-section and single scattering albedo of 102, 203 and 296 polystyrene spheres by integrating cavity ring-down spectroscopy and nephelometery in order to calibrate the system for further studies of biomass aerosols. We compared experimental optical property measurements with Mie theory predicted values. The scattering coefficient and scattering cross-section measurements of the 203 and 296 nm polystyrene spheres agree with Mie theory predictions with uncertainty of 1% and 3% respectively. The optical property measurement for 102 nm polystyrene spheres however disagrees from 9-30%. Single scattering albedo values for the 203 and 296 nm polystyrene spheres are 0.8. The Single scattering albedo for the 102 nm polystyrene spheres ranges form 0.6 to 1. As the scattering measurements are done with less uncertainty for the 203 and 296 nm polystyrene spheres, possible cause for underestimation of the single scattering albedo could be the higher extinction coefficient measured by the CRD. The major sources of errors are discussed and recommendations made to improve accuracy for future measurements.