Ice Nucleation Abilities and Chemical Characteristics of Laboratory-Generated and Aged Biomass Burning Aerosol

Biomass burning aerosols (BBA) significantly contribute to the global aerosol burden, thereby influencing air quality and global climate. The chemical properties and ice nucleation activity of BBA remain poorly constrained due to the heterogeneity of biomass sources and the complexity of atmospheric aging processes. This study comprehensively investigates the chemical composition and ice nucleation of BBA generated from laboratory-controlled burns using various biomass types and burning conditions. Both freshly emitted and photochemically aged BBA exhibit distinct and reproducible chemical compositions. However, the ice nucleation activity of BBA shows substantial variability at mixed-phase cloud temperatures and cannot be predicted by the chemical variability of the organic and inroganic carbon content. This indicates that the carbonaceous components of BBA are not a predictor for ice nucleation activity of BBA.  Using laboratory data, we further evaluate the impact of BBA on atmospheric ice nucleation based on particulate matter mass concentration and equivalent spherical diameter. The estimated ice nucleating particle concentrations from laboratory-produced BBA are lower than those observed during BBA pollution in field studies. We hypothesize that the discrepancy likely arises from the co-lofting of mineral particles during real-world biomass burning events, such as ash or soil particles. These particles, which are absent in our experiments but abundant in field observations, may be an important source of atmospheric INPs, rather than carbonaceous-rich particles from combustion. The role of mineral particles in the INP concentrations of BBA is not quantified in this study, further research to address co-lofting of mineral particles with BBA is encouraged.