the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 Jul 2023
HONO chemistry at a suburban site during the EXPLORE-YRD campaign in 2018: HONO formation mechanisms and impacts on O3 production
Abstract. HONO is an important precursor for OH radicals that impact secondary pollutants production. However, there are still large uncertainties about different HONO sources, which hinder accurate predictions of HONO concentration and hence atmospheric oxidation capacity. Here HONO was measured during the EXPLORE-YRD campaign, along with other important parameters, enabling us to comprehensively investigate HONO variation characteristics and evaluate the relative importance of different HONO sources by using a box model. HONO showed significant variations, ranging from several tens of ppt to 4.4 ppb. The average diurnal pattern of HONO/NOx showed a maximum of 0.17 around noon and resembled that of j(O1D), indicating the existence of photo-induced sources. Modeling simulations with only the default HONO source (OH+NO) largely underestimated HONO concentrations, with the modeled averaged noontime HONO concentration an order of magnitude lower than the observed concentration. The calculated unknown source strength (Punknown) of HONO showed a nearly symmetrical diurnal profile with a maximum of 2.5 ppb h-1 around noon. The correlation analysis and sensitivity tests showed that photo-induced NO2 conversion on the ground was able to explain Punknown. Additional HONO sources incorporated into the box model improved the model’s performance in simulating HONO concentrations. The revised box model well reproduced nighttime HONO concentration but still underestimated daytime HONO concentration. Further sensitivity tests indicated the underestimation of daytime HONO was not due to uncertainties of photo-induced NO2 uptake coefficients on the ground or aerosol surfaces or enhancement factor of nitrate photolysis but was more likely to other sources that were not considered in the model. Among the incorporated heterogeneous HONO sources and the gas-phase source, photo-induced NO2 conversion on the ground dominated the modeled HONO production during the daytime, accounting for 73 % of the total, followed by NO+OH (10 %), NO2 hydrolysis on the ground surface (9 %), photo-induced NO2 conversion on the aerosol surface (3 %), nitrate photolysis (3 %), and NO2 hydrolysis on the aerosol surface (2 %). NO2 hydrolysis on the ground surface was the major source of nighttime HONO, contributing to 65 % of total HONO production. HONO photolysis contributed to 43 % of ROx production during the daytime, followed by O3 photolysis (17 %), HCHO photolysis (14 %), ozonolysis of alkenes (12 %), and carbonyl photolysis (10 %). The net ozone production rate (12.6 ppb h-1) with observed HONO as a model constraint decreased by 45 % compared to that (6.7 ppb h-1) without HONO as a model constraint, indicating HONO evidently enhanced HONO production and hence aggravated O3 pollution in summer seasons. Our study emphasized the importance of NO2 heterogeneous conversion on the ground surface in HONO production and accurate parameterization of HONO sources in predicting secondary pollutants production.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-1058', Anonymous Referee #1, 13 Jul 2023
General comments:
This paper reports observations of HONO in a suburban location in the YRD region over a period of several weeks in summer. The authors find that photo-induced NO2 conversion on the ground dominated the HONO production during the daytime, and NO2 hydrolysis on the ground surface was the major source of nighttime HONO. Meanwhile, the authors employ a box model to investigate what contribution ROx and O3 derived from HONO makes to the radical chemistry at their measurement site. These results are meaningful for the development of HONO investigation. However, there also existed some problems the authors need to improve the manuscript before its publication in ACP.
Specific comments:
1. I am curious about the observation time. In the Method section, the observation period is introduced to be from May 14 to June 20, 2018, but Figure 2 only presents the observed parameters from May 23 to June 18, 2018, whereas the box model simulates the period of May 28-June 12, 2018. Why?
2. Importantly, in the calculation of HONO unknown source strength, the HONO deposition was not considered, why?
3. In the section of vehicle emission, the calculated average contribution of vehicle emission to observed HONO could reach 15%, but it did not appear in the HONO budget, why? According to the HONO budget result, direct emission might be the second most important source for HONO.
4. a few technical comments and typos:
Line 2: The secondary HONO should be removed in the title.
Line 43: SOA should be presented as its full name when it appeared at the first time.
Line 47: …HONO was a vital OH precursor not only in the early morning but also throughout the day.
Line 52/87: varied – various
Line 53: remove “to explain HONO”
Line 76: remove “typically”
Line 80: heterogeneous nitrate/HNO3 photolysis on varied surfaces – adsorbed nitrate/HNO3 photolysis
Line 82: heterogeneous – adsorbed
Line 98/258/321/345/348/356/418/439/474: write the right format (e.g., Fu et al., (2019) found…) for the references.
Line 150: throughout the paper – in this study
Line 155: an instrument model is needed for the portable weather station.
Line 162: try – trying
Line 180: the reaction of NO2 and OH is missing in D(Ox)
Line 186/348: relative humidity has been abbreviated in line 154.
Line 191: it is difficult to derive the deduction of “VOCs are abundant” from “the MAXIMUM diurnal averaged HCHO concentration”. Please rephrase the sentence.
Line 197: the Class-II limit values are corresponding to the maximum 8-hour averaged O3, rather than O3 concentration.
Line 207: What does mean the average peak concentration of OH? For example, in the study of Zhang et al., (2022a), the OH concentration of 2.7*10^6 cm-3 represented the average OH radical concentration at noontime (11:00-13:00). Comparison should be performed at the same level.
Line 220: was possibly the reason – was the possible reason
Line 227: need the reference for the HONO lifetime. Generally, nocturnal HONO lifetime is relatively long (several hours).
Line 235: higher concentration of O3 production – higher O3 production
Line 255: Jinan – Ji’nan
Line 307: photolytic – photo-related?
Figure 2: the order of magnitude for OH is not 10^(-6) but 10^6.
Figure 13: the meaning of legend should be stated one by one.
Citation: https://doi.org/10.5194/egusphere-2023-1058-RC1 -
AC1: 'Reply on RC1', Keding Lu, 27 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1058/egusphere-2023-1058-AC1-supplement.pdf
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AC1: 'Reply on RC1', Keding Lu, 27 Sep 2023
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RC2: 'Comment on egusphere-2023-1058', Anonymous Referee #2, 16 Jul 2023
General comments
The manuscript examined the potential formation pathways for HONO and their impacts on ozone production in a suburban site in the China YRD region during the summertime, using sophisticated field measurements and constrained box model tests. They found that the traditional OH+NO pathway only largely underestimate the observed HONO concentrations. Within several potential pathways, photo-induced NO2 conversion on the ground is mostly likely the missing HONO source during the day, and NO2 hydrolysis on the group surface is the major missing source at night. The study also indicated a significant HONO contribution from direct vehicle emissions. They also assessed the contributions of the missing sources to the ozone production, suggesting an important role of HONO in aggravating ozone pollution. The topic is important and relevant. The dataset and analysis are comprehensive and valuable in improving the understanding the secondary pollutions and control policies. This paper is within the scope of ACP and might be of great interest to the broad atmospheric science community. I have a few questions and comments that should be answered before it can be considered for publication.
Specific comments:Line 36: Should it be “increased by 88%”? (12.6-6.7)/6.7 = 88%
Line 64: “which is typically less than 2% NOx emissions” is confusing. Did you mean the HONO/NOx ratio is typically less than 2%?
Section 3.7 HONO Budget: why did you not include direct emissions, such as vehicle emission, into the HONO production rate? It seems vehicle emission contributed significantly to this site (~15%).
Technical corrections:
Line 28: change it to be “more likely due to”.
Line 37: Should it be “indicating HONO evidently enhanced O3 production”?
Line 42: please define “SOA”, also “VOCs”, “PAN” …in the following text.
Line 52-53: may change the sentence to be “several HONO sources, including …, have been proposed”.
Line 52, 80, 87: replace “varied” with “various”.
Line 98: please correct the format of the citation.
Line 105: from 28 to 76 is more than doubling.
Line 314: Should “Sa” here be the “aerosol surface area density”, rather than “aerosol surface-to-volume ratio”?
Line 345: please correct the format of the citation.
Line 353: change “whether” to be “regardless of whether”.
Figure 2: Some values on y-axis of CO, PM2.5, and NO2 overlaps with each other. Please fix that.
Table 1: Why the Reaction of NO2 hydrolysis only gives 0.5 HONO for 1 NO2 reacted?
Citation: https://doi.org/10.5194/egusphere-2023-1058-RC2 -
AC2: 'Reply on RC2', Keding Lu, 27 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1058/egusphere-2023-1058-AC2-supplement.pdf
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AC2: 'Reply on RC2', Keding Lu, 27 Sep 2023
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RC3: 'Comment on egusphere-2023-1058', Anonymous Referee #3, 26 Jul 2023
Ye et al. examined HONO chemistry and its impact on ozone formation using a field campaign measurement and box modeling. They found a high HONO/NOx ratio of 0.17 around noon coinciding with high J(O1D), which suggests the importance of photo-induced sources for HONO formation. This is furthered verified by statistical analysis and box modeling with updated parameterization. They also demonstrated HONO chemistry can greatly enhance net ozone production by 45%.
Overall, this is a well-executed study and the key conclusions are reasonably defended. In particularly, the observational constraint for HONO chemistry from EXPLORE-YRD campaign adds important evidence to the understanding of HONO formation. However, I suggest the authors to discuss more broadly the HONO formation chemistry under different chemical conditions. I would recommend its publication after revision.
The authors highlighted HCHO production from NO2 heterogeneous conversion at ground. But how is daytime PM2.5 concentration during EXPLORE-YRD? I am wondering if the importance of aerosol update will increase over a severe PM2.5 pollution episode. Some discussion on the application of key conclusion from this study is required.
L43: please spell out “SOA”
L166-167: any reference for “a lifetime of 8 hours”?
L251: this argument should be further justified.
In Fig.1, The website of TROPOMI NO2 data product should be provided.
Citation: https://doi.org/10.5194/egusphere-2023-1058-RC3 -
AC3: 'Reply on RC3', Keding Lu, 27 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1058/egusphere-2023-1058-AC3-supplement.pdf
-
AC3: 'Reply on RC3', Keding Lu, 27 Sep 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-1058', Anonymous Referee #1, 13 Jul 2023
General comments:
This paper reports observations of HONO in a suburban location in the YRD region over a period of several weeks in summer. The authors find that photo-induced NO2 conversion on the ground dominated the HONO production during the daytime, and NO2 hydrolysis on the ground surface was the major source of nighttime HONO. Meanwhile, the authors employ a box model to investigate what contribution ROx and O3 derived from HONO makes to the radical chemistry at their measurement site. These results are meaningful for the development of HONO investigation. However, there also existed some problems the authors need to improve the manuscript before its publication in ACP.
Specific comments:
1. I am curious about the observation time. In the Method section, the observation period is introduced to be from May 14 to June 20, 2018, but Figure 2 only presents the observed parameters from May 23 to June 18, 2018, whereas the box model simulates the period of May 28-June 12, 2018. Why?
2. Importantly, in the calculation of HONO unknown source strength, the HONO deposition was not considered, why?
3. In the section of vehicle emission, the calculated average contribution of vehicle emission to observed HONO could reach 15%, but it did not appear in the HONO budget, why? According to the HONO budget result, direct emission might be the second most important source for HONO.
4. a few technical comments and typos:
Line 2: The secondary HONO should be removed in the title.
Line 43: SOA should be presented as its full name when it appeared at the first time.
Line 47: …HONO was a vital OH precursor not only in the early morning but also throughout the day.
Line 52/87: varied – various
Line 53: remove “to explain HONO”
Line 76: remove “typically”
Line 80: heterogeneous nitrate/HNO3 photolysis on varied surfaces – adsorbed nitrate/HNO3 photolysis
Line 82: heterogeneous – adsorbed
Line 98/258/321/345/348/356/418/439/474: write the right format (e.g., Fu et al., (2019) found…) for the references.
Line 150: throughout the paper – in this study
Line 155: an instrument model is needed for the portable weather station.
Line 162: try – trying
Line 180: the reaction of NO2 and OH is missing in D(Ox)
Line 186/348: relative humidity has been abbreviated in line 154.
Line 191: it is difficult to derive the deduction of “VOCs are abundant” from “the MAXIMUM diurnal averaged HCHO concentration”. Please rephrase the sentence.
Line 197: the Class-II limit values are corresponding to the maximum 8-hour averaged O3, rather than O3 concentration.
Line 207: What does mean the average peak concentration of OH? For example, in the study of Zhang et al., (2022a), the OH concentration of 2.7*10^6 cm-3 represented the average OH radical concentration at noontime (11:00-13:00). Comparison should be performed at the same level.
Line 220: was possibly the reason – was the possible reason
Line 227: need the reference for the HONO lifetime. Generally, nocturnal HONO lifetime is relatively long (several hours).
Line 235: higher concentration of O3 production – higher O3 production
Line 255: Jinan – Ji’nan
Line 307: photolytic – photo-related?
Figure 2: the order of magnitude for OH is not 10^(-6) but 10^6.
Figure 13: the meaning of legend should be stated one by one.
Citation: https://doi.org/10.5194/egusphere-2023-1058-RC1 -
AC1: 'Reply on RC1', Keding Lu, 27 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1058/egusphere-2023-1058-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Keding Lu, 27 Sep 2023
-
RC2: 'Comment on egusphere-2023-1058', Anonymous Referee #2, 16 Jul 2023
General comments
The manuscript examined the potential formation pathways for HONO and their impacts on ozone production in a suburban site in the China YRD region during the summertime, using sophisticated field measurements and constrained box model tests. They found that the traditional OH+NO pathway only largely underestimate the observed HONO concentrations. Within several potential pathways, photo-induced NO2 conversion on the ground is mostly likely the missing HONO source during the day, and NO2 hydrolysis on the group surface is the major missing source at night. The study also indicated a significant HONO contribution from direct vehicle emissions. They also assessed the contributions of the missing sources to the ozone production, suggesting an important role of HONO in aggravating ozone pollution. The topic is important and relevant. The dataset and analysis are comprehensive and valuable in improving the understanding the secondary pollutions and control policies. This paper is within the scope of ACP and might be of great interest to the broad atmospheric science community. I have a few questions and comments that should be answered before it can be considered for publication.
Specific comments:Line 36: Should it be “increased by 88%”? (12.6-6.7)/6.7 = 88%
Line 64: “which is typically less than 2% NOx emissions” is confusing. Did you mean the HONO/NOx ratio is typically less than 2%?
Section 3.7 HONO Budget: why did you not include direct emissions, such as vehicle emission, into the HONO production rate? It seems vehicle emission contributed significantly to this site (~15%).
Technical corrections:
Line 28: change it to be “more likely due to”.
Line 37: Should it be “indicating HONO evidently enhanced O3 production”?
Line 42: please define “SOA”, also “VOCs”, “PAN” …in the following text.
Line 52-53: may change the sentence to be “several HONO sources, including …, have been proposed”.
Line 52, 80, 87: replace “varied” with “various”.
Line 98: please correct the format of the citation.
Line 105: from 28 to 76 is more than doubling.
Line 314: Should “Sa” here be the “aerosol surface area density”, rather than “aerosol surface-to-volume ratio”?
Line 345: please correct the format of the citation.
Line 353: change “whether” to be “regardless of whether”.
Figure 2: Some values on y-axis of CO, PM2.5, and NO2 overlaps with each other. Please fix that.
Table 1: Why the Reaction of NO2 hydrolysis only gives 0.5 HONO for 1 NO2 reacted?
Citation: https://doi.org/10.5194/egusphere-2023-1058-RC2 -
AC2: 'Reply on RC2', Keding Lu, 27 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1058/egusphere-2023-1058-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Keding Lu, 27 Sep 2023
-
RC3: 'Comment on egusphere-2023-1058', Anonymous Referee #3, 26 Jul 2023
Ye et al. examined HONO chemistry and its impact on ozone formation using a field campaign measurement and box modeling. They found a high HONO/NOx ratio of 0.17 around noon coinciding with high J(O1D), which suggests the importance of photo-induced sources for HONO formation. This is furthered verified by statistical analysis and box modeling with updated parameterization. They also demonstrated HONO chemistry can greatly enhance net ozone production by 45%.
Overall, this is a well-executed study and the key conclusions are reasonably defended. In particularly, the observational constraint for HONO chemistry from EXPLORE-YRD campaign adds important evidence to the understanding of HONO formation. However, I suggest the authors to discuss more broadly the HONO formation chemistry under different chemical conditions. I would recommend its publication after revision.
The authors highlighted HCHO production from NO2 heterogeneous conversion at ground. But how is daytime PM2.5 concentration during EXPLORE-YRD? I am wondering if the importance of aerosol update will increase over a severe PM2.5 pollution episode. Some discussion on the application of key conclusion from this study is required.
L43: please spell out “SOA”
L166-167: any reference for “a lifetime of 8 hours”?
L251: this argument should be further justified.
In Fig.1, The website of TROPOMI NO2 data product should be provided.
Citation: https://doi.org/10.5194/egusphere-2023-1058-RC3 -
AC3: 'Reply on RC3', Keding Lu, 27 Sep 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1058/egusphere-2023-1058-AC3-supplement.pdf
-
AC3: 'Reply on RC3', Keding Lu, 27 Sep 2023
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Xuefei Ma
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Yuhan Liu
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Haichao Wang
Zhaofeng Tan
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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