Dear authors. Please address the issues and concerns raised in report #2.

Dear authors. Thank you for addressing the reviewer concerns. The paper is close to the final acceptance, just a few things remaining. Thank you for your patience.

EDITORIAL SUGGESTIONS:

1. I would suggest mentioning in the introduction that there are several types of NOC in particulate matter: primary NOC formed by direct emissions from various sources such as biomass burning; organic nitrates and nitroaromatic compounds formed by the traditional gas-phase oxidation of VOCs, and believed to represent the major part of NOC; heterocyclic NOC compounds formed by reactions of carbonyls with ammonia and amines. The contribution of the last group to NOC is still uncertain but as described in some of the reviews cited in this paper they are likely to be minor in abundance. Right now, the most important type of NOC is mentioned in passing on lines 80-83, which is not ideal. I think distinguishing various types of NOC more clearly in the introduction will make it easier to discuss the results.

2. I find the references do not always directly support the statements. I encourage the authors to go through the reference list one more time carefully and update them as needed. Examples of references that do not correlate well with the statements:
Line 59 and line 67: Feng et al. (2013) does not mention any nitrogen containing organic compounds in their paper, so this reference does not support the statements on these lines. Feng paper is about the importance of BrC in general, not about NOC in BrC.
Line 60: Reference to Noziere et al. (2015) is the only one in this list that is not a review. It could be a better reference for supporting the previous statement about NOC in BrC.
Line 79: Mang et al. (2008) paper did not conclude that NH3 reactions lead to the formation of NOC. The authors may instead refer to Bones et al. (2010) paper, which they already cite.
Line 83 and 324: Paper by Lehtipalo et al. (2018) is not the best choice to support the importance of NOC formation through gas-phase mechanisms. The classic organonitrate formation in photooxidation of hydrocarbons is described in many old papers and books
Lin 98 and 226: Aiona et al. (2017) paper did not study effects of pH or RH on MOC formation. It looked the photodegradation of NOC once they formed. Perhaps a different paper should be cited here.
Line 239: Pure gas-phase formation of NOC was also demonstrated, for example, in [Duporte et al. 2017, Chemical Characterization of Gas- and Particle-Phase Products from the Ozonolysis of alpha-Pinene in the Presence of Dimethylamine. Environ. Sci. Technol. 2017, 51, (10), 5602-5610.]


TECHNICAL CORRECTIONS:

Line 56: (BrC), capable of a comparable level of light absorption-> (BrC). BrC has a comparable level of light absorption
Line 107: Sampling was constructed -> Sampling was done
Line 120: here and below "m/z" should be italicized
Line 136: distributing along their vacuum -> as a function of their vacuum
Line 140: 39 -> m/z 39
Line 136, 139, 142, 279, 760: NOCs-containing -> NOC-containing
Line 149: photochemical oxidation products of -> photochemical oxidation of
Line 225: enhanced -> affected
Line 332: unformatted citations
Line 409, 451, 607, 742: sub and superscripts in chemical formulas
Line 417: missing volume and page
Line 551: verify page number
Lin e576: missing page number
Figure 3 may benefit from a higher resolution
Figure 6 contains faint gridlines in the PDF version that should be removed. Figure 6 caption only mentions dependence on RH but dependence of NOx is shown also. The caption needs to be amended.


SUPPORTING INFORMATION:
I would recommend placing figures and table immediately next to whether they are mentioned and not at the end of the document.
Line 44: 14 -> Fourteen
Line 44: -97[HSO4]- -> m/z -97 [HSO4]- and similar edits in this paragraph
Line 64, 66: dependent -> dependence
Line 89: missing space before the Pratt reference
Figure S1 has low image quality
Line 113: there are earlier reports of making BrC by methyl glyoxal + AS reaction, I would use the original report.
Figure S2: In my opinion, this figure should be split into 4 panels, one for each season
Figure S5: the traces in the left panels are very hard to see
Lin 159: Acs -> ACS