The Effect of Soot and Water Soluble on the Hygroscopicity of Urban Aerosols

Abstract

In this paper, the author investigated some microphysical and optical properties of urban aerosols from OPAC by varying the concentrations of soot and water soluble to determine the effect of hygroscopic growth at the spectral range of 0.25?m to 2.5?m and eight relative humidities (RHs) (0, 50, 70, 80, 90, 95, 98, and 99%).The microphysical properties extracted were radii, volume mix ratio, number mix ratio, mass mix ratio and refractive indices while the optical properties are optical depth and asymmetric parameters all as a function of RHs. Using the microphysical properties, hygroscopic growth factors of the mixtures were determined while using optical depths we determined the Angstrom coefficients, enhancement parameters and the relationship between optical depth and RHs. The growth factors and the enhancement parameters were then parameterized using some models to determine their relationships with RHs. The data fitted the models very well. The angstrom coefficients show that the mixture have bimodal type of distribution with the dominance of fine mode particles and the mode sizes increase with the increase in RH and soot and water soluble concentrations.

Keywords: microphysical properties, optical properties, hygroscopic growth, enhancement parameter, spectral range, Angstrom coefficients, bimodal.