The promotion effect of nitrous acid on aerosol formation in wintertime in Beijing: the possible contribution of traffic-related emissions

Liu, Yongchun; Zhang, Yusheng; Lian, Chaofan; Yan, Chao; Feng, Zeming; Zheng, Feixue; Fan, Xiaolong; Chen, Yan; Wang, Weigang; Chu, Biwu; Wang, Yonghong; Cai, Jing; Du, Wei; Daellenbach, Kaspar R.; Kangasluoma, Juha; Bianchi, Federico; Kujansuu, Joni; Petäjä, Tuukka; Wang, Xuefei; Hu, Bo; Wang, Yuesi; Ge, Maofa; He, Hong; Kulmala, Markku

doi:https://doi.org/10.5194/acp-20-13023-2020

Articles | Volume 20, issue 21

https://doi.org/10.5194/acp-20-13023-2020

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

https://doi.org/10.5194/acp-20-13023-2020

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

Articles | Volume 20, issue 21

Research article

|

07 Nov 2020

Research article |

| 07 Nov 2020

The promotion effect of nitrous acid on aerosol formation in wintertime in Beijing: the possible contribution of traffic-related emissions

Yongchun Liu, Yusheng Zhang, Chaofan Lian, Chao Yan, Zeming Feng, Feixue Zheng, Xiaolong Fan, Yan Chen, Weigang Wang, Biwu Chu, Yonghong Wang, Jing Cai, Wei Du, Kaspar R. Daellenbach, Juha Kangasluoma, Federico Bianchi, Joni Kujansuu, Tuukka Petäjä, Xuefei Wang, Bo Hu, Yuesi Wang, Maofa Ge, Hong He, and Markku Kulmala

Download

Final revised paper (published on 07 Nov 2020)
Supplement to the final revised paper
Preprint (discussion started on 21 Feb 2020)
Supplement to the preprint

Interactive discussion

Status: closed

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

- Printer-friendly version

- Supplement

RC1: 'Review of ‘The promotion effect of nitrous acid on aerosol formation in wintertime Beijing: possible contribution of traffic-related emission’ by Liu et al', Anonymous Referee #1, 06 Apr 2020
- AC1: 'The promotion effect of nitrous acid on aerosol formation in wintertime Beijing: possible contribution of traffic-related emission', Yongchun Liu, 18 May 2020
RC2: 'Review of Liu et al., “The promotion effect of nitrous acid on aerosol formation in wintertime Beijing: possible contribution of traffic-related emission”', Anonymous Referee #2, 07 Apr 2020
- AC4: 'The promotion effect of nitrous acid on aerosol formation in wintertime Beijing: possible contribution of traffic-related emission', Yongchun Liu, 18 May 2020
RC3: 'Review of "The promotion effect of nitrous acid on aerosol formation in wintertime Beijing: possible contribution of traffic-related emission" by Liu et al', Anonymous Referee #3, 09 Apr 2020
- AC3: 'The promotion effect of nitrous acid on aerosol formation in wintertime Beijing: possible contribution of traffic-related emission', Yongchun Liu, 18 May 2020
AC2: 'The promotion effect of nitrous acid on aerosol formation in wintertime Beijing: possible contribution of traffic-related emission', Yongchun Liu, 18 May 2020

Peer-review completion

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

AR by Yongchun Liu on behalf of the Authors (18 May 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (08 Jun 2020) by John Liggio

RR by Anonymous Referee #2 (16 Jun 2020)

RR by Anonymous Referee #3 (21 Jun 2020)

Suggestions for revision or reasons for rejection

A main problem with this paper is that the authors make use of many qualitative arguments based on previously published papers instead of using their observation data to quantitatively support their speculations. Despite my strong objections to these speculations in the first-round review, the long-winded response mostly re-stated what was in the original paper. Reviewing the original paper and reading the responses are painful exercises because the authors’ arguments are mostly based on some “beliefs” seemingly garnered from incorrectly reading other papers. Their observations were often either ignored or misused. My concerns are not properly addressed and I cannot find good reasons to change my original recommendation.

(1) In response to my first comment, they cited several previously published papers and corrected a mistake I pointed out in the first-round review. A larger primary radical source from HONO photolysis does not mean that OH increases in the same proportion as the primary source increase. The question, which they did not answer in the response, is how much OH increase can be sustained by the photolysis of HONO. The response ran around in circles of this question.

The newly added statement, “These results mean that the photolysis of HONO should play an important role in the initiation of the daytime HOx and ROx chemistry on polluted days in winter, while photolysis of O3 becomes more important from April to June.”, did not answer the question on the quantitative effect of HONO photolysis on OH. The statement itself is meaningless. What does “more important” mean? Is “more” for comparison between April-June and winter or between HONO and O3 photolysis? The understanding of chemistry is also flawed. The primary radical source from O3 photolysis is not JO1D*CO3. It is much smaller because most O1D reacts with N2 and O2. JO1D*CO3 cannot be compared to the photolysis rate of HONO directly (which was done in this paper).

The response did not address my comment of “There are many reasons that HONO/CO correlates with OA/CO. For example, CO is primary in winter in Beijing. If HONO and OA variations are from secondary sources, there will be high correlations as shown.”

The statement, “It should be noted that the daytime lifetime of HONO is very short due to photolysis. This means regional transport should has little influence on local HONO concentration.”, is also incorrect. The lifetime of HONO at night is long and transport affects HONO concentrations. In daytime, if a substantial fraction of HONO is from NO2, transport certainly affects NOx and therefore HONO.

In the statement, “As the meteorological condition was stagnant during these cases as indicated by the low wind speed (< 1.0 m s-1, Fig. S5D), it was reasonable to mainly ascribe the increase of OA concentration to local secondary formation initiated by OH radical from HONO photolysis”, how could the authors know that the increase of OA is from “local secondary formation initiated by OH radical from HONO photolysis”?

The new statement, “We explained the increased ammonium as the result of enhanced neutralization of HNO3 by NH3 (Wang et al., 2018;Wen et al., 2018;Sun et al., 2018) because NH4+ was adequate to neutralize both sulfate and nitrate as shown in Fig.S8” is incorrect. In Beijing winter, higher HNO3 does not necessarily convert more NH3 to ammonia. The authors appear to have a limited understanding of aerosol chemistry.

(2) In response to my comments on the HONO budget, Table S3 is useful. However, looking at Fig. S9, could some of the HONO measured with ~100 ppb NOx be a result of inlet conversion of NO2 to HONO? Some dirty vehicles may have high HONO/NO2 emission ratios, but I find it puzzling why no measurements seem to have HONO/NO2 ratio < 1% for the selected “fresh emission” data points.

The response did not answer my comment “No discussion was given on what volume was used and how it varied in a day.” The response states “The hourly NOx emission inventory from vehicles in Beijing, with an annual emission rate of 109.9 Gg yr-1 (Yang et al., 2019), was used when calculating the Evehicle in this work.” The authors need to state what area is used for Beijing. The Beijing metropolitan area is very large. Vehicle emission rates can be extremely low in the rural regions of Beijing, the area of which is much larger than the urban core. A further statement “…the PBL height as described in Section 2.2. Thus, the calculated emission rate reflected the diurnal variation of both the emission inventory and the PBL height” does not provide useful information. I cannot find where they got the PBL data and their calculation on the effects of diurnally varying PBL on the budget of HONO. For example, the nighttime PBLH is usually 10-50 times less than the daytime. Therefore, the nighttime vehicle HONO source is 10 times or more than daytime (after accounting for lower emissions at night). The diurnal variation for the vehicle source in Figure 3 is too small.

The only information of PBLH data used in this study I can find is Fig. S4A. The figure shows that PBLH varies from 20 to 3500 m. The distribution does not seem to show that PBLH increases from winter to summer. It provides no useful information on answering my question of diurnal HONO budget variation.

The newly added statement, “In the daytime, we assume a zero concentration gradient”, is wrong. If the PBLH is 3 km, how can HONO be constant from the surface to 3 km? At night, PBLH is usually low. Vertical mixing is not even a sink of HONO for a budget analysis that extends from the surface to the PBL top. (Eqs. (12) and (13) cannot even be used to estimate the vertical loss of HONO when the vehicle emission source is estimated as emission rate/PBLH). The statement “In the night, 79 % of the wind speed was lower than 1.0 m s-1 in winter” is likely based on surface wind measurements at a site where wind is blocked by buildings in the city. Looking at any meteorological data, wind speed is stronger in winter than summer in Beijing and the average wind speed in Beijing in winter is much higher than 1 m/s.

The authors assume that ground level gamma values are the same as dust aerosols and calculated a low surface HONO source. What is the justification? The assumption is arbitrary.

I do not follow the reasoning from “If both the rNO2,BET (1x10-6) and surface roughness are increased to the values used in modeling studies, the nighttime production rate of HONO via heterogeneous reaction of NO2 on ground surface will be 2.9 ppb h-1. This means a large sink missed if this number is reasonable” to the conclusion statement “These results mean that heterogeneous reaction might not be a major HONO source. This is consistent with a recent work that found heterogeneous reaction being unimportant when compared with traffic emission during haze events in winter in Beijing (Zhang et al., 2019c)”. The authors found that the surface source can be much larger (a factor of 10) than the vehicle source. However, because they or previous publications believe that the vehicle HONO source is most important, the authors concluded that the vehicle HONO source is the most important in their dataset too. The argument is circular and meaningless.

The HONO budget analysis is flawed for several reasons. The methodology has errors. There is no closure on the (hourly) budget. Each source and sink terms have very large uncertainties and some arbitrary decisions were made on the parameter values to justify that vehicle emissions are the largest HONO source. The analysis results in this paper are not scientifically credible.

Hide

ED: Reconsider after major revisions (14 Jul 2020) by John Liggio

AR by Yongchun Liu on behalf of the Authors (25 Aug 2020) Author's response Manuscript

ED: Publish subject to technical corrections (24 Sep 2020) by John Liggio

Dear Dr. Liu,

I am satisfied with your response and addressing of issues from the second round of reviewer comments (from reviewer #2). While the paper has become more qualitative as a result, I believe that it is better to err on the side of caution in this case rather than attempting to be overly quantitative. I also appreciate the relevance of this work and understand its worth in the context of other published literature on the topic.

Having said that, parts of the manuscript continue to have some language/grammatical issues which makes it difficult to read at times. Some examples of these instances are included below, but there are many, many others within this paper (too many to include here). I suggest another editing of this paper to improve the English as much as possible.

line 97: "some other researches" is incorrect
line 100: not clear what "Ji’an" refers to
line 101: "In addition, the traffic emission was proposed to be...." should be "....traffic emissions were proposed..."
line 106: "more studies is still required..." should be "are required.."
line 157: "they were believed as minor sources" should be "...to be minor sources.."
line 236: "....pollution events showed...."; "exhibited" would be better.
line 286: "The similar trends...." should be "...similar trends..."
line 315: do not start sentence with "Because"
line 325: "....2003), subsequently contribute to..." should be "...contributing..."
line 337: "...HONO exhibited quick reduction" should be "... a quick reduction..."
line 360: I think you mean ammonia not ammonium.
line 396: ".... the lowest marge with..."; not clear what this is
line 398: should be: "...an interference from the sampling inlet overestimated HONO concentration by 6.7%..."
line 455: should be - "...taken as the lower limit for..."
line 509: should be - "...on ground surfaces..."

Hide

AR by Yongchun Liu on behalf of the Authors (02 Oct 2020) Author's response Manuscript

Download

Article (1294 KB)
Full-text XML

Short summary

Understanding of the chemical and physical processes leading to atmospheric aerosol particle formation is crucial to devising effective mitigation strategies to protect the public and reduce uncertainties in climate predictions. We found that the photolysis of nitrous acid could promote the formation of organic and nitrate aerosol and that traffic-related emission is a major contributor to ambient nitrous acid on haze days in wintertime in Beijing.