Rapid transition in winter aerosol composition in Beijing from 2014 to 2017: response to clean air actions

Li, Haiyan; Cheng, Jing; Zhang, Qiang; Zheng, Bo; Zhang, Yuxuan; Zheng, Guangjie; He, Kebin

doi:https://doi.org/10.5194/acp-19-11485-2019

Articles | Volume 19, issue 17

https://doi.org/10.5194/acp-19-11485-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-19-11485-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 17

Research article

|

12 Sep 2019

Research article |

| 12 Sep 2019

Rapid transition in winter aerosol composition in Beijing from 2014 to 2017: response to clean air actions

Haiyan Li, Jing Cheng, Qiang Zhang, Bo Zheng, Yuxuan Zhang, Guangjie Zheng, and Kebin He

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Final revised paper (published on 12 Sep 2019)
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Preprint (discussion started on 14 May 2019)
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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'review of changes in Beijing winter aerosol composition', Rodney Weber, 06 Jun 2019
- AC1: 'Response to the comments of referee #1 (Rodney Weber)', Haiyan Li, 29 Jul 2019
SC1: 'Changes in Beijing PM composition', Cort Anastasio, 09 Jun 2019
- AC2: 'Response to the short comments of Cort Anastasio', Haiyan Li, 29 Jul 2019
RC2: 'Review comments', Anonymous Referee #2, 15 Jul 2019
- AC3: 'Response to the comments of referee #2', Haiyan Li, 29 Jul 2019

Peer-review completion

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

AR by Haiyan Li on behalf of the Authors (29 Jul 2019)

ED: Referee Nomination & Report Request started (13 Aug 2019) by Steven Brown

RR by Anonymous Referee #2 (18 Aug 2019)

Suggestions for revision or reasons for rejection

The authors have done a generally good job responding to review comments and revising the manuscript. However, there are two comments to which the authors' responses do not seem satisfactory.

For the comment that questioning the rationales for using SO4/BC and NO3/BC ratios in the analysis, the authors responded that “The absolute concentration of sulfate and nitrate in the atmosphere is not only controlled by atmospheric chemical reactions but also influenced by boundary layer developments. By using SO4/BC and NO3/BC in the analysis, we can see more clearly how the secondary formation of sulfate and nitrate varied compared to primary emissions.” This is assumption is not correct. Boundary layer height affects locally emitted primary pollutants and regionally formed secondary pollutants in different ways. Diel variation in BLH is also associated with changes in air temperature, which may affect semivolatile and nonvolatile species differently. Arguing for sulfate and nitrate formation based on variations in SO4/BC and NO3/BC ratios is misleading. For example, for a secondary species that has a flat diel profile, such as sulfate, its ratio to BC may show a daytime increase only because the dominator (i.e. BC) has a daytime decrease. Related discussions should be removed or revised.

For the comment that the incorrect usage of “nitate/(nitrate+NOx)” as an index for the oxidation ratio of nitrogen. The authors responded “According to the ISORROPIA calculations in this study, the fraction of particulate nitrate in total nitrate was higher than 0.99 for the average winter conditions in both 2014 and 2017. Therefore, it is meaningful to use nitrate/(nitrate+NOx) to evaluate the oxidation ratio of nitrogen without the consideration of gas-phase HNO3.” The issue is that oxidation of NOx produces not just HNO3 and nitrate. It also forms organic nitrates. Does the total nitrate from ISORROPIA include gaseous and particulate organic nitrates? This reviewer disagrees it is proper to use nitrate/(nitrate+NOx) in the discussions and request that discussions related to NOR be removed.

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ED: Publish subject to technical corrections (19 Aug 2019) by Steven Brown

AR by Haiyan Li on behalf of the Authors (19 Aug 2019) Author's response Manuscript

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Short summary

We combined the online observations of aerosol components and a regional chemical transport model to investigate the response of aerosol chemistry to the stringent clean air actions in Beijing. We found a rapid transition in winter aerosol composition from 2014 to 2017 with decreased sulfate contribution and increased nitrate fraction and evaluated the underlying drivers. The anthropogenic emission reductions in Beijing and its surrounding regions are identified to play a major role.