Characterization of freshly-emitted particles from poplar wood burning: OC/EC, morphology, and elemental analysis under varying ignition temperatures

Abstract

Biomass burning is a significant source of atmospheric pollution. While existing studies have largely focused on the comprehensive analysis of biomass burning particulate matter (PM), the variations in particle size, morphology, and mixing characteristics under different burning conditions remain to be thoroughly investigated. In this study, we collected PM emitted from poplar wood burning in a quartz tube furnace at three different ignition temperatures (400, 600, and 800 °C), aiming to analyze the chemical composition and single-particle characteristics of PM under varying ignition temperatures. OC/EC analysis revealed that the OC emission factor at 400 °C (35.05 ± 2.11 g/kg) was an order of magnitude higher than those at 600 °C (1.00 ± 0.21 g/kg) and 800 °C (1.57 ± 0.93 g/kg), while the EC emission factor increased by an order of magnitude with rising temperature, from 0.41 ± 0.03 g/kg at 400 °C to 4.03 ± 0.94 g/kg at 800 °C. Further observation under TEM-EDS showed that carbonaceous particles were the predominant components of PM emitted from poplar wood burning at all temperatures. At 400 °C, over 95 % of the particles were primarily amorphous organic matter, with only a small number of EC particles formed. At 600 °C, 72.6 % of the emitted particles were aggregated black carbon particles, 17.5 % were tar-balls, and the remaining 9.9 % were monomeric organic matter particles with extremely small particle sizes. At 800 °C, 93.8 % of the particles were two types of black carbon particles with varying monomer particle sizes and nearly bare surfaces. Our experimental results indicate that burning temperature is a crucial factor leading to differences in the composition, morphology, and elemental composition of biomass-emitted particles. Furthermore, they serve as a reminder that the significant variations caused by different burning temperatures should be considered when estimating biomass burning, especially the increasingly widespread wildfire burning.