Dear Authors:
Thank you for your careful consideration of the referee reports. In general I find the responses satisfactory, but I have a few minor comments that I would like to see addressed prior to publication.
-line 372-373: I suggest moving the sentence "Details of this event..." before the previous sentence in order to improve readability.
-line 438: Organic nitrates can still form from photo-oxidation even at low NOx and thus this pathway cannot be completely ruled out. Organic nitrate measurements in the southeast US (Lee et al., 2016; Romer et al., 2016) albeit at slightly higher NOx concentrations (although not significantly higher) show that both NO3 and photo-oxidation pathways likely exist. References cited by those papers provide evidence at even lower NOx concentrations. Thus, although there may be reasons that NO3 chemistry may be favored (e.g., higher organic nitrate yields, the correlation with 3-hydroxygluraric acid), photo-oxidation cannot be ruled out and I suggest that this point is presented with a more nuanced view of the complex chemistry that is occurring.
-line 526: The 28% was due to a very specific local biomass burning events, correct? This should be stated here.
-line 544: I believe the identified ON/WSON values should be %, not ratio.

Lee et al; Proc. Natl. Acad. Sci., 201508108, doi:10.1073/pnas.1508108113, 2016.
Romer et al; Atmos Chem Phys, 16(12), 7623–7637, doi:10.5194/acp-16-7623-2016, 2016.