Formation mechanisms of atmospheric nitrate and sulfate during the winter haze pollution periods in Beijing: gas-phase, heterogeneous and aqueous-phase chemistry

Liu, Pengfei; Ye, Can; Xue, Chaoyang; Zhang, Chenglong; Mu, Yujing; Sun, Xu

doi:https://doi.org/10.5194/acp-20-4153-2020

Articles | Volume 20, issue 7

https://doi.org/10.5194/acp-20-4153-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Multiphase chemistry of secondary aerosol formation under...

https://doi.org/10.5194/acp-20-4153-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 7

Research article

|

07 Apr 2020

Research article |

| 07 Apr 2020

Formation mechanisms of atmospheric nitrate and sulfate during the winter haze pollution periods in Beijing: gas-phase, heterogeneous and aqueous-phase chemistry

Pengfei Liu, Can Ye, Chaoyang Xue, Chenglong Zhang, Yujing Mu, and Xu Sun

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Final revised paper (published on 07 Apr 2020)
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review', Anonymous Referee #1, 11 Dec 2019
RC2: 'Comment on acp-2019-994', Anonymous Referee #2, 12 Dec 2019
AC1: 'a point-by-point response to the reviews', PengFei Liu, 11 Feb 2020

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by PengFei Liu on behalf of the Authors (11 Feb 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (13 Feb 2020) by Veli-Matti Kerminen

RR by Anonymous Referee #2 (20 Feb 2020)

Suggestions for revision or reasons for rejection

The revised manuscript has been greatly improved. There is still one question that I want to ask. After revising, the correlation between [NO2]2 × [O3] and NOR was plotted in Fig. 3b. However, the correlation of them under RH<60% condition is very weak. Hence, I think maybe it is not necessary to address the significance of the heterogeneous hydrolysis of N2O5 under RH<60%. Discussion on the results at RH>60% in detail is enough. In addition, line 599-601“Considering that the formation of atmospheric NO3 radical is mainly via the oxidation of NO2 by O3, the heterogeneous hydrolysis of N2O5 occurs only at high O3 and NO2 levels during the nighttime (He et al., 2018;Wang et al., 2018b).” This sentence is a little incompatible with the result in Fig 3b. Because in Fig. 3b, the highest concentration of NO2 and O3 was shown at RH<30% and the lowest concentration of them was shown at RH>60%. However, the contribution of heterogeneous hydrolysis of N2O5 to nitrate was not consistent with that result. Hence, it is better to rethink the way of expression.The revised manuscript has been greatly improved. There is still one question that I want to ask. After revising, the correlation between [NO2]2 × [O3] and NOR was plotted in Fig. 3b. However, the correlation of them under RH<60% condition is very weak. Hence, I think maybe it is not necessary to address the significance of the heterogeneous hydrolysis of N2O5 under RH<60%. Discussion on the results at RH>60% in detail is enough. In addition, line 599-601“Considering that the formation of atmospheric NO3 radical is mainly via the oxidation of NO2 by O3, the heterogeneous hydrolysis of N2O5 occurs only at high O3 and NO2 levels during the nighttime (He et al., 2018;Wang et al., 2018b).” This sentence is a little incompatible with the result in Fig 3b. Because in Fig. 3b, the highest concentration of NO2 and O3 was shown at RH<30% and the lowest concentration of them was shown at RH>60%. However, the contribution of heterogeneous hydrolysis of N2O5 to nitrate was not consistent with that result. Hence, it is better to rethink the way of expression.

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RR by Anonymous Referee #1 (02 Mar 2020)

ED: Publish subject to minor revisions (review by editor) (05 Mar 2020) by Veli-Matti Kerminen

AR by PengFei Liu on behalf of the Authors (06 Mar 2020) Author's response Manuscript

ED: Publish as is (09 Mar 2020) by Veli-Matti Kerminen

AR by PengFei Liu on behalf of the Authors (10 Mar 2020)

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Short summary

A vast area in China is currently going through severe haze episodes with drastically elevated concentrations of PM_2.5 in winter. Nitrate and sulfate are main constituents of PM_2.5, but their formations via NO₂ and SO₂ oxidation are still not comprehensively understood. Our results found that the gas-phase reaction of NO₂ with OH and the heterogeneous hydrolysis of N₂O₅ play key roles in nitrate formation, and SO₂ aqueous-phase oxidation with H₂O₂ rather than NO₂ contributed greatly to sulfate.