An Improved Model for the Gas‐Particle Partitioning of Polycyclic Aromatic Hydrocarbons: Multiple Thermodynamic Interactions With Carbonaceous Aerosols

Abstract Gas‐particle partitioning is a crucial atmospheric process governing the cycle and fate of polycyclic aromatic hydrocarbons (PAHs). To clarify its mechanisms, we measured gaseous and particulate concentrations of PAHs in the East China Marginal Sea (ECMS) to develop an improved model integrating thermodynamic interactions between PAHs and distinct aerosol carbonaceous fractions. Aerosol samples were thermally divided into 6 carbonaceous fractions: OM 1 to OM 4 (organic matter), EC 1 and EC 2 (elemental carbon). A systematic surrogate method was employed to simulate the absorption/adsorption process of PAHs in each fraction, and a computational enumeration framework coupled with the Abraham solvation parameter model was implemented for model parameterization. Compared to conventional models, this model improved the prediction accuracy for logarithmic gas‐particle partitioning coefficient (log K P ) by 34%. It also clarified that OM 3 exhibits the strongest absorption capacity, likely driven by polar‐induced interactions between this fraction and PAHs, whereas PAH adsorption onto the EC 1 and EC 2 proceeded homogeneously. Additionally, the model identified adsorption onto elemental carbon as the dominant partitioning mechanism for 3‐ and 4‐ring PAHs, while for 5‐ring PAHs, the contribution of absorption into OM 3 becomes comparable to that of adsorption. The prediction deviations of log K P for 3‐ring PAHs by this model suggested that adsorption onto inorganic aerosol constituents may also influence their gas‐particle partitioning. This study elucidated the interactions between PAHs and different carbonaceous fractions in aerosols and advanced mechanistic understanding of the gas‐particle partitioning.