Effects of combustion condition and biomass type on the light absorption of fine organic aerosols from fresh biomass burning emissions over Korea

In this study, the light absorption properties of fine organic aerosols from the burning emissions of four biomass materials were examined using UV-spectrophotometry and Aethalometer-measurements, respectively. For wood chips and palm trees, the burning experiments were carried out with different combustion temperatures (200, 250, and 300 degrees C) in an adjustable, electrically heated combustor. The light absorptions of water and methanol extracts of aerosols, and smoke particles showed strong spectral dependence on the burning emissions of all biomass materials. However, the burning aerosols of wood chips showed stronger absorption than those of the other biomass burning (BB) emissions. For the burning aerosols of wood chips and palm trees, organic carbon/elemental carbon (OC/EC) decreased as the combustion temperature increased from 200 to 300 degrees C. Absorption Angstrom exponent (AAE) values tended to decrease when combustion temperature increased for smoke aerosols and methanol extracts in smoke samples. The mass absorption efficiency at 365 nm (MAE(365), m(2) g(-1).C-1) of water- and methanol-extractable OC fractions was highest in wood chip burning smoke samples. MAE(36)(5) values of methanol extracts for rice straw, pine needles, wood chips, and palm trees burning emission samples were 1.35, 0.92, 2.36-3.37, and 0.86-1.42, respectively. For wood chip and palm tree burning emissions, AAE(325)(-430nm) values of methanol extracts were strongly correlated with OC/EC (i.e., combustion temperature) with slopes of 0.11 (p < 0.001) and 0.02 (p < 0.001), and R-2 values of 0.87 and 0.74, respectively. Moreover, a linear regression between MAE(365)of methanol extractable OC and OC/EC showed slopes of -0.05 (p < 0.001) and -0.004 (p < 0.001) and R-2 of 0.72 and 0.74, respectively. The results of this study clearly demonstrate that burning condition and biomass type influence the light absorption properties of organic aerosols from BB emissions. (C) 2020 Elsevier Ltd. All rights reserved.