Source-Based Size-Resolved Optical Properties of Carbonaceous Aerosols

Abstract

In this study, the source-based optical properties of polydisperse carbonaceous aerosols were determined from PM2.5 concentrations measured at a Global Atmospheric Watch station in South Korea. The extinction and absorption coefficients of carbonaceous aerosols were calculated using the Mie theory and assuming a lognormal size distribution. Based on the mass concentration from the EPA's Positive Matrix Factorization (PMF) receptor model, which considers five source identification and apportionment factors (biogenic source, local biomass burning, secondary organic aerosol, transported biomass burning, and mixed sources), the source-based size-resolved mass extinction and absorption efficiencies were estimated for each source using a multilinear regression model. The results show that the source-based optical properties depend on the aerosol size and physicochemical characteristics of the chemical compounds. The long-range transport of biomass burning (LBB) aerosol, which has a mass concentration of 20%, holds a 12.1-23.1% total extinction efficiency-depending on the size and refractive index-in the range of 0.1-0.5 mu m in geometric mean diameter and humic-like substances (HULIS) imaginary refractive index of 0.006-0.3. Biogenic sources of aerosols with small diameters have higher mass absorption efficiencies (MAE) than other sources, depending on the size and refractive index.