Light absorption properties and absorption emission factors for indoor biomass burning

The optical properties of light-absorbing carbonaceous aerosols have caused increasing concerns due to their significant impacts on local and regional climates. In this study, particles from biomass burning in home stoves were collected and evaluated for their optical properties. The absorption Ångström exponent (AAE) values ranged from 1.17 to 2.92 and negatively correlated with the modified combustion efficiency, indicatinging more brown carbon in combustion emissions with relatively low combustion efficiencies. The average contribution of brown carbon to the total aerosol absorption at 370 nm was equally as important as that of black carbon (BC), with the average relative contribution fraction of 50% varying from 10% to 84% for different biomasses. The average value of the mass absorption efficiency (MAE) of BC (MAE_BC) at 880 nm was positively correlated with the ratio of organic carbon to elemental carbon, indicating the significant coating effects of organic aerosols. The MAE values of BrC at 370 nm were in the range of 1.1-11.3 m²/g, with an average of 5.1 ± 2.2 m²/g. The estimated absorption emission factors at 370 nm and 880 nm were 3.75 ± 3.45 and 0.84 ± 0.78 m²/kg, respectively. Optical property information of particles emitted from real-world biomass burning are imperative in future modeling studies of biomass burning impacts on climate. The limitation of the relatively small sample size for each subgroup fuel calls for more field- and lab-based emission characterization research.