Unravelling gas-particle partitioning dynamics in cooking aerosol oxidation through FIGAERO-CIMS analysis

Abstract

Cooking emissions are increasingly important sources of organic aerosol in densely populated urban areas as clean-air actions reduce emissions from industrial activities and fossil-fuel combustion. Their atmospheric evolution and environmental and health effects remain difficult to assess because of the complexity of their composition and transformation pathways. Here, we conducted a laboratory study of emissions from heated corn oil using a Go:PAM oxidation flow reactor. We investigated the evolution of composition, volatility, and gas-particle partitioning and evaluated discrepancies between FIGAERO-based measurements and thermodynamic estimates. FIGAERO-I-CIMS measurements combined with a 2-D VBS parameterization were used to characterize the composition and volatility distributions of primary and secondary cooking-originated organic aerosol. Kinetic calculations indicate molar-weight-dependent partitioning kinetic schemes with surface process as rate-limiting step. Partitioning of primary cooking aerosols is generally biased toward gas phase compared to the equilibrium state. In secondary aerosol, partition of compounds with molar mass under 120 g mol −1 favours gas phase, compounds between 120–220 g mol −1 exists in near-equilibrium state, species with molar mass over 220 g mol −1 favours aerosol phase. The thermodynamic comparison nevertheless reveals a substantial unresolved gap between FIGAERO-derived effective volatility and equilibrium thermodynamic estimates, reflecting combined measurement and model uncertainties. Results clarify the scope of kinetic limitations in gas-particle partitioning during cooking-emission and oxidation, identify priorities for improving the representation of cooking emissions in atmospheric studies.