Predictive Models of Gas/Particulate Partition Coefficients (K(P)) for Polycyclic Aromatic Hydrocarbons and Their Oxygen/Nitrogen Derivatives

Polycyclic aromatic hydrocarbons (PAHs) and their oxygen/nitrogen derivatives released into the atmosphere can alternate between a gas phase and a particulate phase, further affecting their environmental behavior and fate. The gas/particulate partition coefficient (K(P)) is generally used to characterize such partitioning equilibrium. In this study, the correlation between log K(P) of fifty PAH derivatives and their n-octanol/air partition coefficient (log K(OA)) was first analyzed, yielding a strong linear correlation (R(2) = 0.801). Then, Gaussian 09 software was used to calculate quantum chemical descriptors of all chemicals at M062X/6-311+G (d,p) level. Both stepwise multiple linear regression (MLR) and support vector machine (SVM) methods were used to develop the quantitative structure-property relationship (QSPR) prediction models of log K(P). They yield better statistical performance (R(2) > 0.847, RMSE < 0.584) than the log K(OA) model. Simulation external validation and cross validation were further used to characterize the fitting performance, predictive ability, and robustness of the models. The mechanism analysis shows intermolecular dispersion interaction and hydrogen bonding as the main factors to dominate the distribution of PAH derivatives between the gas phase and particulate phase. The developed models can be used to predict log K(P) values of other PAH derivatives in the application domain, providing basic data for their ecological risk assessment.