Variations in the Mass Absorption Efficiency of Primary Carbonaceous Aerosols from Residential Solid Fuel Combustion

High uncertainty in aerosol radiative forcing assessment is closely associated with limited knowledge of the optical properties of carbonaceous aerosols in real environments. Residential fuel combustion is a major contributor to light-absorbing brown carbon (BrC) and black carbon (BC), yet their mass absorption efficiency (MAE) and association with complex chemical components remain poorly understood. This study investigated the MAE of BrC at λ = 370 nm (MAE_BrC) and BC at λ = 880 nm (MAE_BC), focusing on their variabilities attributed to organic chemical components through 131 burning tests involving various fuel-stove combinations. The MAE_BrC, with an average of 4.8 ± 2.2 m²/g and a range of 0.35 to 10 m²/g, was comparable to previously reported values from field-based experiments; however, MAE_BC (average: 8.7 ± 3.7 m²/g, range: 2.9–28 m²/g) was obviously lower than those field-based observations. This discrepancy was attributed to the greater dependence of MAE_BC on combustion efficiency and highlighted the need for appropriate methodologies for measuring MAE values. MAE_BC increased with the rise in organic carbon-to-element carbon ratios due to the lensing effect, which was a significant factor determining the MAE_BC and explaining 36–77% of its variations. While MAE_BrC mainly depended on the different BrC chromophores emitted during combustion with protein-like substances and humic-like substances being the predominant components of BrC derived from biomass and coal combustion, contributing 31% and 46% to the light absorption of extractable BrC from biomass and coal, respectively.