Page 3: I agree with one of the reviewers that papers in preparation should not be cited (to be consistent with the accepted practices). Please remove reference to Lu et al.

Page 16, Line 33: missing parenthesis and comma

Figure 1: amu is an outdated unit for molecular weight; it is not used for the mass-to-charge ratio in mass spectrometry. The quantity m/z is typically viewed as dimensionless so I would change the X-axis label accordingly, as you did in other mass spectra figures. While you are changing this figure, the yellow font used for the COA factor label is very hard to see, a different color is recommended. Also this figure appears hazy on my screen (the rest of the figures do not have this problem). Perhaps there is a way to export it at a higher resolution.

Figure 3: The figure legend implies that this plot uses H:C ratios for the ions as opposed to neutral species. I think VK plots for the neutrals instead of ions are easier to interpret. Perhaps it is not even an issue given how few H+ adducts (just one?) you observe. Since you are providing formulas of the neutral compounds in the text, why not calculate the H:C for the neutral species? The same comment applies to the rest of the VK plots.

Figure 10: the labels is this figure are very small relative to the figure size, I am worried they will be invisible in the final print. IS there any way to increase them? (In general, labels in many of the figures in this paper are disproportionally small, but in this this figure it is extreme).

Figure 13 and Figure 14: I would fix capitalization in the Y-axis title (flux -> Flux)

Bozzetti et al. (2016) reference is missing page numbers

Veres et al. (2010) reference is missing page numbers

Zhang et al. (2017b) reference is missing page numbers

The use of DOI numbers is not very consistent – some have Doi in front of them, and some have nothing.

Figure S1, S3, S5: dat -> date

Figure S6: Hourly -> Hour of the Day

Table S2: I think the right column title should be “Molecular Weight of the Neutral (Da)”. I actually do not see how the calculated molecular weight is useful (because you can get it from the formula) – if you list values you should list the observed m/z values for the Na+ and H+ adducts. This way you could also include ions that you observed but could not assign.