Chemical and optical properties of biomass burning and diesel emissions and their atmospheric aging

Emissions from biomass burning (BB) and diesel combustion significantly impact air quality, health and climate by releasing pollutants. However, due to variability in combustion sources and efficiency, and emission aging, their aerosol's composition and optical properties remain poorly understood and underrepresented in climate and air quality models. This study investigated the chemical and physical properties of BB aerosol emissions using advanced instrumentation in the EUPHORE simulation chamber. Emissions from different wood types (including mixtures with diesel exhaust) were analyzed, considering flaming and smoldering combustion, and their evolution under day and night conditions. Results indicated that combustion phase had a greater influence on emissions than wood type. Flaming combustion and diesel exhaust produced similar elemental carbon (EC) emissions (0.55 g/kg fuel and 0.46–0.73 g/kg fuel, respectively) while smoldering yielded lower EC (0.1–0.37 g/kg fuel) and higher organic carbon (OC), leading to higher OC/EC ratios (53 ± 20 g/kg fuel) than flaming and diesel fumes (1.5 ± 0.8 and 0.6 ± 0.1 g/kg fuel, respectively). Smoldering emissions contained more complex, higher molecular weight organics, with more harmful effects than flaming. Daytime aging promoted formation of highly-oxidized organic compounds, while nighttime aging, driven by nitrate radicals, formed nitro-aromatic compounds, associated with genotoxicity and carcinogenicity. Both aging processes also increased aerosol absorption and scattering, affecting climate-relevant properties. This study provides one of the most comprehensive chamber-based analyses of BB and diesel-related emissions and their atmospheric evolution, integrating aerosol chemical composition and optical properties. The results contribute to understanding the impact of BB on air quality, health and climate, enhancing models and informing effective mitigation strategies.