I agree with the reviewer #2 that the paper still has a number of issues, so to avoid delay in publication please be sure to address every comment carefully.

In addition you did not really respond to one of the previous comments by reviewer #1. The reviewer stated: "Table 1 and elsewhere: The authors assume a density of 1.2 g cm - 3 . I think it would be better to calculate an effective density directly from the AMS and SMPS size distributions that would be more applicable to the data. See, for example, DeCarlo et al., 2004." This is a valid point and needs to be addressed.

EDITORIAL REVIEW BY SN:

Dear authors. I am sorry about the delay in reviewing your paper. As you have seen the reviewers have had a larger number of suggestions, and it takes time to review and re-review papers, which require major revisions. However, we are not converging to the “Minor Revision” stage. Please address the remaining minor comments and the paper will be accepted.

Your paper title “Photochemical aging of organic and inorganic ambient aerosol from the Potential Aerosol Mass (PAM) reactor experiment in East Asia” is too general in my opinion. I would choose a title that better reflects the primary finding of the paper, as opposed to the technical method used to achieve this result.

Last paragraph of the introduction section can be improved. This is usually where you explain the motivations for the study and summarize the main results. Good questions to discuss here: What is the hypothesis? Why was this particular location chosen? What makes it better than other possible locations for testing your research hypothesis? What are the main findings summarized in one sentence?


L37 and elsewhere: m/z is generally written in italic in ACP and other journals

L63: delete “(SA)” since you are not using this abbreviation anywhere in the paper

L43: replace “NO3” by “inorganic nitrate”

L179 and L292: there is no need to define “CS” twice and not use it in the paper – please remove this abbreviation

L187: replace “COO” by “CO2”

Figure 2: symbol for micro did not print correctly in the Y-axis labels. The size and X-axis labeling of panels c and d are not the same as size of panels a and b. Are these figures meant to be on the same packed stacked on top of each other?

Figures 3,4: same issue with the symbol for micro not printing. Perhaps it is only in my Adobe Acrobat program.

Figures 5, 6: very low image quality – need to be fixed for the final publication

L286: replace “formation of nuclei-mode particles” with “nucleation of particles”

L284 and L293: I would not use “nuclei-mode particles”, a more common term if “nucleation mode particles”. Perhaps you can say “freshly nucleated” on L284

Page 14: I think it is not accurate to use terms “organic m/z 43” and “organic m/z 44”. I would explain at the beginning that m/z correlates with less oxidized organics and m/z correlates with carboxylic acids and just use “m/z 43” and m/z 44” from then on.

Page 14: I also fine the use of terminology such as “m/z 43-like compounds” and “m/z 44-like compounds” in accurate. Please avoid such lose terms.

L425: It is not clear to me what microN refers to in the formula

Conclusion section: it is not clear that the conclusion section is needed since you have an atmospheric implication section before it. I think they should be merged together.


COPY OF REVIEWER COMMENTS:

This 2nd revision of the Kang et al. manuscript is improved vs. the previous one. I still disagree about a number of analyses and details (or e.g. leaving out PMF), but this is the authors’ paper and not mine, so we’ll leave it at that. I think it should be acceptable into ACP after the authors address a few remaining items:

- Abstract L45: referring to the volatility of the organics is not justified. This should just refer to the more oxidized organics. Oxidation was measured, volatility was not. And the two are not always correlated. Early studies found and reported a correlation, but more studies have accumulated since then that have shown that oxidation and volatility are often not correlated. This is also an issue around L272 and L347 and perhaps elsewhere.

For this reason the terms LO and MO OOA (less and more oxidized OOA) are must more commonly used now instead of SV and LV-OOA. I recommend that the authors adopt this terminology.

- The use of solenoid valves for switching, which get quite hot in operation, could have caused some evaporation of the aerosol, which should at least be mentioned in the methods section.

- Responses p4-5 (and relevant paper text and figures): the scatter plots of AMS vs SMPS do not look consistent with BC or soil at all. BC is typically a much smaller fraction of total PM1 at remote sites (more like 1-2%). Soil is highly variable and typically uncorrelated with secondary species, and would not explain the nearly constant slopes observed in many periods. Likely differences in particle transmission or remaining calibration uncertainties are the real reasons. The accuracy of both the AMS and the SMPS (for mass or volume) are ~35%, so perfect agreement is not expected. I suggest revising this text accordingly, as otherwise confusion can result since the reasons given are not plausible for experienced practitioners. Actually acknowledging the real limitations and uncertainties of the measurements inspires more confidence than blaming effects that are implausible causes of what’s observed.

- An important plot, which I had requested before, but it is still not shown, is a scatter plot of the added mass in the SMPS (SMPS_after_PAM – SMPS_ambient) vs the added mass in the AMS (AMS_after_PAM – AMS_ambient) using contiguous points in time. That plot is important for confidence on the quantification of the reactor enhancements.

- Responses p18: some text is quoted here (which I can’t find on the revised manuscript): “L144, added the sentence. “Contrary to other studies (Ortega et al., 2016; Palm et al., 2016), we designed the experiment as simple as possible with a single OH exposure considering the dynamic change of meteorological conditions in the study region, a remote island.”

This does not make sense. Time variations are slowest at remote sites such as the one in the current paper, and they are faster in forests and much faster in urban areas, due to much faster changes of emission sources and smaller spatial scales coupled with advection. So that should be revised (or just not included in the paper, which seems to be the case at present).

- Supp L 124: chlorine should be chloride

- The text in many of the figures (axis labels etc.) are often very small, and will be hard to read in the final ACP version. I strongly suggest making them larger.

I would recommend inserting the scatter plot of the added mass in the SMPS (SMPS_after_PAM – SMPS_ambient) vs the added mass in the AMS (AMS_after_PAM – AMS_ambient) using contiguous points in time as the reviewer suggested. You inserted it in the response but not in the SI section. The reviewer believed it was important to have included so I would include it.

L93: “sulfated-dominated” -> “sulfate-dominated”

L94: “The size, mass,” -> “The particle size, mass,”

L190: “discussion on single mass of m/z 43 and m/z 44 represent the entire organic classes” -> “discussion of ions observed at m/z 43 and m/z 44 should be broadly applicable to these two classes of organic compounds”

Please be sure to fix the issues with the “micro” symbol not showing up properly in figures (e.g., by saving figures as raster graphics (TIFF) before inserting them in the file).