Light absorption characteristics of primary brown carbon during a complete residential biomass combustion process and their links with aerosol composition

Abstract

Brown carbon (BrC) has been recognized as an important light-absorbing organic aerosol, and biomass combustion is the main source of BrC. Residential biomass burning is a heterogeneous process, and the dynamics of BrC optical properties during the burning process are still not well understood. Therefore, laboratory test equipped with online instruments (aerosol mass spectrometry and Aethalometer) of residential biomass burning was established to measure the optical properties of BrC. During a complete burn cycle, the light absorption characteristics at the flaming stage are generally similar for wood and crop straws, while it is distinctly different at the burnout stage. BrC contributes 0.141 to 0.609 to light absorption at UV region among different stages. The absorption emission factor and mass absorption cross section of BrC (MACBrC) at the flaming stage was significantly larger than that at the burnout stage. MACBrC was calculated and related to the aerosol composition, aromatic compounds (f77) and PAHs/OA were significantly positively related to MACBrC near the ultraviolet region, suggesting that aromatic compounds and PAHs are the vital contributors to the light absorption of BrC. This time-resolved study provides additional understanding of the dynamics of BrC optical properties during residential biomass burning processes. The results of this study will provide for more accurate assessment of the climate impact of BrC from residential biomass combustion.