Comment on egusphere-2023-199

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Gas/particle (G/P) partitioning is an important atmospheric process for semi-volatile organic compounds (SVOCs). However, the exact prediction of the G/P partitioning coefficients (<em>K</em>_P) of polycyclic aromatic hydrocarbons (PAHs) was still a challenge. In this study, a new steady-state G/P partitioning model was established based on the level III multimedia fugacity model, with the introduction of the particulate proportion of PAHs in emission (<em>ϕ</em>₀) particularly. Same with the previous steady-state model, three different domains with different G/P partitioning behavior can be divided by the threshold values of log <em>K</em>_OA (octanol-air partitioning coefficient). The difference between the new steady-state model and previous G/P partitioning models was quite different in different domains. It was found that the deviation with the <em>K</em>_P of PAHs from the equilibrium state was caused by both the gaseous and particulate interferences, in which <em>ϕ</em>₀ determined the influence of the two interferences. Different forms of the new steady-state model were observed under different values of <em>ϕ</em>₀. The comparison with log <em>K</em>_P of PAHs between the prediction result of the new steady-state model and the monitored results from 11 cities in China indicated that the <em>ϕ</em>₀ was an important factor for the G/P partitioning of PAHs. In addition, the new steady-state model also showed good performance for the prediction of log <em>K</em>_P of PAHs with totally gaseous emission and PBDEs with totally particulate emission. Therefore, it can be concluded that the <em>ϕ</em>₀ should be considered in the study of G/P partitioning of PAHs, which also provided a new insight for other SVOCs.