Semi-volatile organic compounds (SVOCs) were typical pollutants in atmosphere. The gas and particle partitioning of SVOCs is important for their long-range atmospheric transport and health to human. Therefore, the study of gas and particle partitioning has attracted more attentions recently. However, the mechanism of the gas and particle partitioning for some types SVOCs was not well clarified. In this study, the impact of gaseous degradation of SVOCs on the equilibrium state of gas and particle partitioning was comprehensively discussed and studied. Some new findings were provided for this topic, which will improve our understanding of the mechanism of gas and particle partitioning.

I have some comments and suggestions to the study:

(1)    In the title of the manuscript, semi-volatile organic compounds were used, however, in the main manuscript, only PAHs were studied and discussed. Therefore, semi-volatile organic compounds should be replaced by PAHs or Me-PAHs.

(2)    Abstract, what kind of theoretical model? More details should be added.

(3)    Introduction Section, the authors mentioned the scientific problem was the deviation between the prediction of models and monitoring for Kp with LMW SVOCs. The deviation or the problem needs to be quantified.

(4)    Section 3.1. for the comparison with other studies, the numbers and names of Me-PAHs should be mentioned. If different Me-PAHs were compared, the conclusion was not reasonable.

(5)    Fig.1, if different seasons were separated for discussion. I don’t think it is necessary for the figure of “All seasons”.

(6)    Section 3.2, the equations of (3)-(5) were not easily for understanding.

(7)    Section 3.3, for equation (6), more derivation process or steps are necessary for reading, or maybe in SI.

(8)    Section 3.3, the last two sentences: “It can be found that, the impact caused by the gaseous degradation on KP' deviation was in the range of 1 to 8.4 times under different ϕ0 (0 to 1) in the temperature range of −50 to 50℃. However, due to the limited consideration of the gaseous degradation (only reaction with hydroxyl radicals) in this study, the actual impact of the gaseous degradation on KP' deviation was expected to be higher than the range.” I have two questions here: first, the uncertainty analysis of results is needed for the model; second, the two appearances with “the gaseous degradation” between the first sentences and the second sentence were confused for me, please modify the writing. 

(9)    Fig. 4, the title of Y-axis is not clear.

(10)    This kind of writing was confused for reading: in the range of 0.429 to 0.887 (KP': 2.68 to 7.70 times increased). Pleased modify the writing for the similar problem through the manuscript.

In this manuscript, Zhu et al. reported their field observations, highlighting two interesting and important key findings: (1) significant diurnal variation in the gas-phase and particle-phase concentrations of methylated polycyclic aromatic hydrocarbons (Me-PAHs), and (2) remarkably higher gas-particle partitioning quotients (logKp') for lighter Me-PAHs during daytime compared to nighttime. To explain the latter observation, the authors propose that "the higher gaseous degradation of [Me-PAHs] during daytime than that during nighttime should be responsible for their special diurnal variation".

The authors arrived at this hypothesis as they investigated another hypothesis and found it insufficient for explaining the observed diurnal variation in logKp'. For another hypothesis, they assessed whether the logKp' observed for the same chemical at different temperatures correlates with the calculated logKOA at those temperatures, where logKOA at different temperatures were calculated using a simple regression (A/T + B). The authors found no significant correlation (Figure 3), which led them to conclude that the temperature-dependent variability in logKOA does not adequately explain the observed diurnal variation in logKp'. They then turned to an alternative hypothesis that the temperature-dependent variability in the gaseous degradation rate "should be responsible" for the observed diurnal variation in logKp', given that the temperature-dependent variability in the gaseous degradation rate can lead to a much more pronounced variation in logKp' (Figure 4).

Honestly, I do not believe the authors' reasoning is convincing. It is not logically sound to accept an alternative hypothesis as valid simply because another has been invalidated - unless the two hypotheses are mutually exclusive. So my first recommendation is that the authors reframe their argument to state that "the temperature-dependent variability in logKOA does not sufficiently explain the observed diurnal variation in logKp'", rather than asserting that "temperature-dependent variability in the gaseous degradation rate *should be responsible* for the observed diurnal variation in logKp'". This adjustment would present their conclusion as a more measured interpretation of the data, rather than a definitive explanation (actually, it is only a speculation).

In addition, I don't even think the observed absence of correlation between the observed logKp' and logKOA at different temperatures can lead to any meaningful conclusions, as many sources of uncertainties may contribute to the deviation of the logKp'-logKOA relationship. I just name a few:

(1) One critical assumption underlying the logKp'-logKOA relationship is that lipid-like organics predominantly control the partitioning of chemicals into the particle phase. Although this assumption may hold for a variety of organochlorines and organobromines, it may not be universally applicable to Me-PAHs. This is because, for PAHs, carbonaceous components (such as black carbon) can sometimes exceed lipid-like organics as the principal sorbents (Cornelissen et al., Environ. Sci. Technol. 2005, 39, 18, 6881–6895). Of course, Cornelissen et al. focused on the significant role of carbonaceous materials in the sorption of PAHs onto sediments and soils, but it also gives the possibility of sorption of PAHs by carbonaceous components in aerosol. So, it should not be unexpected to see significant deviations from the logKp'-logKOA relationship for Me-PAHs.

(2) Another potential reason for deviation is the uncertainties associated with the parameters in Equation 2. The values of A and B in this equation are derived from pp-LFER solute descriptors. However, Me-PAHs were not among the training chemicals used to develop these pp-LFER solute descriptors, and it is not sure whether these chemicals can be adequately predicted by these relationships.

(3) It has also been recognised that advection of air masses may also lead to deviation from the expected temperature dependence of logKp'. See Wania et al. Environ. Sci. Technol. 1998, 32, 8, 1013–1021.

Of course, we may also name another set of possibilities responsible for the absence of correlation between the observed logKp' and logKOA at different temperatures. Clearly, all of these indicate a need for cautious interpretation of the use of the logKp'-logKOA relationship, especially when applied to chemicals like Me-PAHs that may not align perfectly with the assumptions and parameters used in its derivation. As such, I do not think the manuscript has discussed and excluded these possible counterexamples to well justify the authors' interpretation of the deviation of the logKp'-logKOA relationship. So my second recommendation is that the authors just end the manuscript with the statement that "the temperature-dependent variability in logKOA does not sufficiently explain the observed diurnal variation in logKp'", stop overinterpreting its implications, and more importantly, acknowledge and discuss a wide array of possible reasons (including but not limited to those outlined above) that leads to such a deviation from the logKp'-logKOA relationship.

Overall, I believe the two key findings are very interesting and important and deserve publication. However, the authors' explanations and interpretations do not fully convince me. It may be beneficial for the authors to consider either dropping much of the speculative discussion in Section 3.2 and all of Section 3.3 or pivoting towards discussing the potential reasons behind these findings in a more thorough, comprehensive manner.