|Review of Kang et al.|
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.