Molecular Dynamics Simulation of the Aggregation Behavior of Typical Aromatic Pollutants and Its Influence on the n-Octanol–Air Partition Coefficient

The aggregation behavior of typical aromatic pollutants in the <i>n</i>-octanol phase and its influence on the <i>n</i>-octanol-air partition coefficient (<i>K</i>_OA) were investigated using molecular dynamics simulation. The aggregate proportion of selected aromatic pollutants gradually increased with increasing simulation time and then reached a dynamic equilibrium state. It is interesting to find that the higher the concentration of aromatic pollutants, the more aggregates formed in the <i>n</i>-octanol phase. Log <i>K</i>_OA values of these aromatic pollutants were subsequently estimated based on the percentages of aggregates and the solvation free energy from the gas phase to the <i>n</i>-octanol phase. The log <i>K</i>_OA values were also found to gradually increase with increasing concentration. Therefore, the effect of concentration on <i>K</i>_OA should be taken into consideration during the analysis of the environmental behavior and transport of these aromatic pollutants. In addition, it was found that π-π interactions drive the formation of different numbers of aggregates for different aromatic pollutants, a phenomenon that affects the <i>K</i>_OA values of aromatic pollutants. The above results shed some light on the effects of aggregates and concentration on the partition behavior of aromatic pollutants and provide a theoretical basis for the correction of <i>K</i>_OA of aromatic pollutants in the environment.