Search

The partitioning of semi-volatile organic compounds (SVOCs) between gas and particle phases plays a crucial role in their long-range transport and health risk assessment. However, the accurate predicting of the gas/particle (G/P) partitioning quotient (K P') remains a challenge, especially for the light molecular weight (LMW) SVOCs due to their upward deviation from the equilibrium state. Based on the diurnal study of concentrations and K P' values for methylated polycyclic aromatic hydrocarbons (Me-PAHs), it was found that the diurnal variations of methylated naphthalenes (Me-Naps, one type of LMW SVOCs) were different from other Me-PAHs, that K P' values during daytime were higher than that during nighttime, and the regression lines of log K P' versus log K OA (octanol-air partitioning coefficient) for daytime and nighttime were non-overlap. It was found that the higher gaseous degradation of Me-Naps during daytime than that during nighttime should be responsible for their special diurnal variation of K P', which provided a new explanation for the non-equilibrium behavior of K P' of LMW SVOCs. Moreover, the influence of gaseous degradation on the deviation of K P' from the equilibrium state was deeply studied based on a theoretical model considering particulate proportion in emission (ϕ 0). It was found that the deviation occurred when ϕ 0 F GR (F GR, degradation flux of gas phase) cannot be ignored when compared with F GP (flux from gas phase to particle phase). It can be concluded that the deviation was not only related to the gaseous degradation rate (k deg), but also related to ϕ 0. Furthermore, an amplification of K P' ranging from 1 to 8.4 times under different ϕ 0 (0 to 1) in the temperature range of −50 to 50 °C was estimated based on the individual degradation rates of Me-Naps and three LMW PAHs. In summary, it can be concluded that the influence of gaseous degradation should also be considered for the G/P partitioning models of SVOCs, especially for the LMW SVOCs, which provided new insights into the related fields. [ABSTRACT FROM AUTHOR]

Gas–particle (G–P) partitioning is a crucial atmospheric process for semi-volatile organic compounds (SVOCs), particularly polycyclic aromatic hydrocarbons (PAHs). However, accurately predicting the G–P partitioning of PAHs has remained a challenge. In this study, we established a new steady-state G–P partitioning model based on the level-III multimedia fugacity model, with a particular focus on the particulate proportion (ϕ0) of PAHs in emissions. Similar to previous steady-state models, our new model divided the G–P partitioning behavior into three domains based on the threshold values of log⁡KOA (octanol–air partitioning coefficient), with slopes of 1, from 1 to 0, and 0 for the three domains. However, our model differed significantly from previous models in different domains. We found that deviations from the equilibrium-state G–P partitioning models were caused by both gaseous interference and particulate interference, with ϕ0 determining the influence of this interference. Different forms of the new steady-state model were observed under different values of ϕ0 , highlighting its significant impact on the G–P partitioning of PAHs. Comparison of the G–P partitioning of PAHs between the prediction results of our new steady-state model and monitored results from 11 cities in China suggested varying prediction performances under different values of ϕ0 , with the lowest root mean square error observed when ϕ0 was set to 0.9 or 0.99. The results indicated that the ϕ0 was a crucial factor for the G–P partitioning of PAHs. Furthermore, our new steady-state model also demonstrated excellent performance in predicting the G–P partitioning of PAHs with entirely gaseous emission and polybrominated diphenyl ethers with entirely particulate emission. Therefore, we concluded that the ϕ0 should be considered in the study of G–P partitioning of PAHs, which also provided a new insight into other SVOCs. [ABSTRACT FROM AUTHOR]

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 (K 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 (ϕ 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 K 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 K P of PAHs from the equilibrium state was caused by both the gaseous and particulate interferences, in which ϕ 0 determined the influence of the two interferences. Different forms of the new steady-state model were observed under different values of ϕ 0. The comparison with log K 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 ϕ 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 K P of PAHs with totally gaseous emission and PBDEs with totally particulate emission. Therefore, it can be concluded that the ϕ 0 should be considered in the study of G/P partitioning of PAHs, which also provided a new insight for other SVOCs. [ABSTRACT FROM AUTHOR]