the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 17 May 2021
Air pollutants in Xinjiang during the COVID-19 pandemic and glaciochemical records of a Tien-Shan glacier
Abstract. The outbreak of COVID-19 unprecedently impacts the world in many aspects. Air pollutants have been largely reduced in cities worldwide, as reported by numerous studies. We investigated the daily concentrations of SO2, NO2, CO and PM2.5 monitored across the Xinjiang Uygur Autonomous Region (Xinjiang), China, from 2019 through 2020. The variation in NO2 showed responding dips when the local governments imposed mobility restriction measures, while SO2, CO and PM2.5 did not consistently correspond to NO2. This difference indicates that the restriction measures targeted traffic majorly. Sampling from two snow pits separately dug in 2019 and 2020 in Urumqi No.1 (UG1), we analysed water-stable isotopes, soluble ions, black and organic carbon (BC and OC). BC and OC show no differences in the snow-pit profiles dated from 2018 to 2020. The concentrations of human activity induced soluble ions (K+, Cl−, SO42− and NO3−) in the snow shrank to 20 %–30% in 2020 of their respective concentrations in 2019, while they increased 2–3.5-fold in 2019 from before 2018. We suggest that the pandemic has already left marks in the cryosphere and outlook that more evidence would be exposed in ice cores, tree rings, and other archives in the future.
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Interactive discussion
Status: closed
-
RC1: 'Comment on tc-2021-133', Anonymous Referee #1, 10 Jun 2021
Review of “Air pollutants in Xinjiang during the COVID-19 pandemic and glaciochemical records of a Tien-Shan glacier” by Wang et al. submitted to The Cryosphere.
The topic of the paper includes important topics related to the COVID-19 situation and atmospheric quality. Unfortunately, the presentation and analysis of the paper are insufficient in my view for publication in a scientific journal. This relates to many categories that I consider important for a scientific publication, and I can only list a few points here. Most importantly, this study is qualified for publication in The Cryosphere due to several reasons described below.
At first, the relationship between Chinese pollution and COVID-19 have been reported by several groups, and the reports for that region have also already reported (e.g. Zheng et al. 2020 [Zheng, B., Zhang, Q., Geng, G., Shi, Q., Lei, Y., and He, K.: Changes in China's anthropogenic emissions during the COVID-19 pandemic, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2020-355, in review, 2020.]). In the study above, the results for the Xinjiang region were also included. Thus, for the publication of this study, the author should clarify the importance and significance of this study. Otherwise, I do not agree with the publication of the journal The Cryosphere.
Certainly, the results for the snow pit for Urumqi No.1 glacier are something new. However, there are several uncertainties that were not addressed in the main text. Particularly, the age determination of the snow pit and melting and redistribution of ion species should be clearly addressed. Without careful investigation, the conclusions would not be supported.
Overall, I do not think the current writing does not sound scientific, and I do not recommend it for publication. See the detailed comments in the major comments.
Major comments
1. Significance of this paper.
There are many previous studies published on the topic of the relationship between atmospheric quality and COVID-19. The author should describe how this study addresses the remaining problems by comparing other existing studies for this topic. Besides, the author should explain how/why this study should be published in this journal The Cryosphere.
2. Atmospheric pollutants (section 3.1 and related method sections)
In that section, the results and discussion were very briefly shown. The detailed data sets were tucked away in the supplement, but this is not trivial information. In addition, the stages of restriction by the Xinjiang government (stage I to IV) should be explained what these are. Particularly, I think we need to know which kind of changes were required by the governments for the stages.
Additionally, for the interpretation for August to September data, authors concluded in Line 174 “Besides Urumqi, no other prefectures were reported publicly to impose lockdown measures. The concentration of NO2 plunged responding to the lockdown (Figure 2 and S2), implying that the lockdown was not only applied in Urumqi but all other prefectures of Xinjiang”. However, these kinds of information should be asked to the local government directly. It is curious for me that the authors concluded the actual governmental policy based on the atmospheric measurements.
Related to the snow pit results, I think authors should discuss with 2018 data together with the 2019-2020 results. In fact, the authors concluded pollutants for the year 2019 was higher than in 2018 based on the snowpit results. If so, similar results should be obtained from the atmospheric observation.
Overall, I think only Figure 2 and a brief description are not enough for the publication. It is suggested overall to make a deeper analysis of atmospheric pollutants levels between 2018 to 2020 in that region and resubmit the paper, if not to TC may be on a more specific lower impact factor journal.
3. Snowpit results
It is almost impossible for me to judge if or not the conclusions obtained from this study are correct. To evaluate, the age evaluation of these two snow pits and fluxes of ions and impurities should be determined in reasonable ways. In Fig. 3, the authors just determined the age with “with best estimated time annotated on the right (L202-203)”, and thus, I could not evaluate this. Also, in Fig. 4, the authors compared the concentrations of impurities (not fluxes) and concluded the “the snow showed dramatically decreases from 2019 to 2020”, which is not qualified by a reasonable/scientific basis. In addition, impurities concentrations could be redistributed due to melting and refreeze, and thus the comparison with concentration may induce wrong conclusions. I recommend using the flux of the deposition or at least the mass-weighted concentration of each year/season. Overall, it is suggested the analysis of the data is too brief to get a good claim, which is needed for the publication in TC.
4. The increase of atmospheric pollutants from 2018 to 2019
In line 221, the authors concluded the ion species increased from 2018 to 2019, and authors stressed that this is “possibly attributed to increasingly intense emission before the pandemic”. I wonder that this can be tested with the same analysis using atmospheric pollutants data sets as the authors did for 2019 to 2020 in Fig. 2 and S2. If atmospheric pollutants data for that regions do not support this hypothesis, the conclusion based on snow pits both for the increase in 2018 to 2019 nor decrease in 2019 to 2020 by COVID-19 situation would be supported.
The followings are minor points. Note that the minor comments are not exhaustive. This paper should be rewritten correctly, and even if these minor comments are revised, it does not mean that I will recommend it for publication.
Minor comments
L20 Authors only discussed the year 2018 to 2020, and no information available “before 2018” in this study.
L33: byproduct can be replaced by “emissions”.
L37-39:The recent paper showed the opposite conclusions. See Jones et al. 2021 GRL (https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL091883)
L72: What does it mean by “Level 2, 3, 4” here? These are different from the stage for the restrictions? Please write the detail of the restrictions in that area or country, and let the non-Chinese audience understand.
L94: The information shown in Table S2 should not be trivial. Besides, the stages I-IV shown in Fig. 2 should be explained what these are in the method section.
L110: “will” is not appropriate here.
L123: Explain what the standards are. Also, the use of “would” for the method section is not appropriate.
L123-124: Add information of column for IC system.
L148: This sentence is not necessary.
L155: Explain which city was the exception.
L156: Explain using the exact city that the author indicates.
L176: It is very curious. The information for lockdown should be provided by other information (governmental reports etc.) but not by the atmospheric observation. Chicken and egg should not be replaced here.
L147-180: Overall, more discussion is needed, particularly for the links of atmospheric qualities to the stage I to IV and lockdown event during summer.
L220: Covid should be COVID here.
L242: The restriction information should be according to the governmental reports.
L245 and 249: What do authors mean/define by “dramatically”?
L250: I suggest “measure” is changed to “observe”.
L251: This sentence is not necessary to support the conclusion.
L255: The entire paragraph is not necessary.
Citation: https://doi.org/10.5194/tc-2021-133-RC1 -
AC1: 'Reply on RC1', Jing Ming, 21 Jun 2021
Interactive responses to the comments of Referee 1 in Phase 1
The reply to the general view:
The authors appreciate that the general view raised the concerns of our work. They are valuable and helpful to improve the quality of our manuscript in the later phase (the final response). We are thinking of ways to supplement the missing parts and fill up the gaps between our work and the referee’s expectation. In the open discussion phase, we replied to the major comments and talked about our ideas of revision in the next phase.
The reply to the major comments:
- Significance of this paper. There are many previous studies published on the topic of the relationship between atmospheric quality and COVID-19. The author should describe how this study addresses the remaining problems by comparing other existing studies for this topic. Besides, the author should explain how/why this study should be published in this journal The Cryosphere.
Re: There are indeed many studies previously published on the topic of COVID-19 restrictions and air quality. We will explore more next and strengthen the discussion of the topic and highlight our featured points different from other studies. Because our work is regarding with the glacier and snow chemistry besides air pollutants during the pandemic, we choose the Cryosphere as the journal to submit our manuscript after carefully studying its aims and scope before the submission.
- Atmospheric pollutants (section 3.1 and related method sections). In that section, the results and discussion were very briefly shown. The detailed data sets were tucked away in the supplement, but this is not trivial information. In addition, the stages of restriction by the Xinjiang government (stage I to IV) should be explained what these are. Particularly, I think we need to know which kind of changes were required by the governments for the stages.
Additionally, for the interpretation for August to September data, authors concluded in Line 174 “Besides Urumqi, no other prefectures were reported publicly to impose lockdown measures. The concentration of NO2 plunged responding to the lockdown (Figure 2 and S2), implying that the lockdown was not only applied in Urumqi but all other prefectures of Xinjiang”. However, these kinds of information should be asked to the local government directly. It is curious for me that the authors concluded the actual governmental policy based on the atmospheric measurements.
Related to the snow pit results, I think authors should discuss with 2018 data together with the 2019-2020 results. In fact, the authors concluded pollutants for the year 2019 was higher than in 2018 based on the snowpit results. If so, similar results should be obtained from the atmospheric observation.
Overall, I think only Figure 2 and a brief description are not enough for the publication. It is suggested overall to make a deeper analysis of atmospheric pollutants levels between 2018 to 2020 in that region and resubmit the paper, if not to TC may be on a more specific lower impact factor journal.
Re: We would extend the discussion on the restrictions applied by local governments individually to their administrative precincts in the revision, which will take some time and be showed in the final response.
We haven’t ask the local governments directly but to consult some officials in private and look up the open information released on the governments’ websites, newspapers and other media reports. We will extend the discussion on this issue later.
For the data retrieved from the snow pits, the atmospheric observations in 2018 will be included later, and we will discuss with the accordingly new ingredients in the revision. After all, from the concerns raised by the comments, we presume that the discussion in the revision will be greatly strengthened.
- Snowpit results. It is almost impossible for me to judge if or not the conclusions obtained from this study are correct. To evaluate, the age evaluation of these two snow pits and fluxes of ions and impurities should be determined in reasonable ways. In Fig. 3, the authors just determined the age with “with best estimated time annotated on the right (L202-203)”, and thus, I could not evaluate this. Also, in Fig. 4, the authors compared the concentrations of impurities (not fluxes) and concluded the “the snow showed dramatically decreases from 2019 to 2020”, which is not qualified by a reasonable/scientific basis. In addition, impurities concentrations could be redistributed due to melting and refreeze, and thus the comparison with concentration may induce wrong conclusions. I recommend using the flux of the deposition or at least the mass-weighted concentration of each year/season. Overall, it is suggested the analysis of the data is too brief to get a good claim, which is needed for the publication in TC.
Re: In the revising process, we will reconsider the analysis of the data and strengthen the discussion regarding the dating of the snowpit and other concerns raised by the comment.
- The increase of atmospheric pollutants from 2018 to 2019. In line 221, the authors concluded the ion species increased from 2018 to 2019, and authors stressed that this is “possibly attributed to increasingly intense emission before the pandemic”. I wonder that this can be tested with the same analysis using atmospheric pollutants data sets as the authors did for 2019 to 2020 in Fig. 2 and S2. If atmospheric pollutants data for that regions do not support this hypothesis, the conclusion based on snow pits both for the increase in 2018 to 2019 nor decrease in 2019 to 2020 by COVID-19 situation would be supported.
Re: We will extend the dataset back to 2018 or even earlier to validate the preliminary impression in the discussion paper.
The followings are minor points. Note that the minor comments are not exhaustive. This paper should be rewritten correctly, and even if these minor comments are revised, it does not mean that I will recommend it for publication.
Re: According to the major comments, we evaluate that the revised manuscript would be probably rewritten in most parts. We will not expand our replies to the minor comments one by one here and will leave them to the final response phase (Phase 2) complying with the guidance of TC.
Citation: https://doi.org/10.5194/tc-2021-133-AC1 -
RC3: 'Reply on AC1', Anonymous Referee #1, 21 Jun 2021
This is a brief reply to the authors' comment posted. TC and other EGU journals have a discussion phase (Phase 1, opened), and followed by final response & reviews (Phase 2, not opened). However, if there is significant revisions are expected in Phase 1, the reviews for the revised manuscript should not be closed. Otherwise, there is a concern that might hurt the original concept of the "Interactive review process" for this journal.
Citation: https://doi.org/10.5194/tc-2021-133-RC3
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AC1: 'Reply on RC1', Jing Ming, 21 Jun 2021
-
RC2: 'Comment on tc-2021-133', Anonymous Referee #2, 14 Jun 2021
In this study the authors report some observational analyses of the impact of Coivd-19 pandemic restriction measures on air pollutants in Xinjiang, China, and ions/particles in Tien-Shan glacier. They found that NO2 had a large reduction during certain time periods, compared to small variations in SO2, CO and PM2.5. Soluble ions in Tien-Shan snow samples also decreased by 20-30%, although BC and OC showed no differences from 2018 to 2020. The measurements are new and interesting. However, the paper in its current form reads more like a short measurement report. More in-depth analysis is needed to make the paper more scientifically significant. Please see my specific comments below.
Major comments:
- The authors seem to assume that air pollutants at the surface sites and species in Tian-Shan glacier are from local sources in Xinjiang, so emission changes in surrounding regions are not discussed. This is likely not the case, especially for the long-lived ones such as CO. The authors should review relevant studies in the literature on source attribution and/or run airmass back-trajectories to track the sources of pollutants reaching the measurement sites. This would help better understand the observed changes, spatial variation and their relationship with emissions.
- The observed changes are attributed to mobility and emission changes. How about the roles of atmospheric dynamical, physical and chemical processes? Atmospheric transport, dry/wet deposition and chemical reactions should affect the concentrations of the air pollutants. It could be more complicated for the concentrations of ions, BC and OC in snow that involve precipitation and snow melting processes. The direct year-to-year comparisons may be biased due to large interannual variability in these processes. Comparison of 2020 results to longer-term mean might be helpful. More analyses and discussions in this regard are necessary.
- How accurate is the snow dating for the recent past back to 2018? The different results of 2019 between the two snow pit profiles need more clarification. What are the possible reasons for the differences? Please clarify.
Minor technical comments:
Line 34: has -> have
Line 101: Please check the measurement end date of December 31, 2021.
Line 110: Suggest using present tense for this sentence; Staff should be used as a singular noun here.
Citation: https://doi.org/10.5194/tc-2021-133-RC2 -
AC2: 'Reply on RC2', Jing Ming, 21 Jun 2021
Interactive responses to the comments of Referee 2 in Phase 1
The reply to the general view:
We thank the referee for the encouraging general view of our work and raising the concerns of how to improve the paper significantly. We will address our replies to the comments below. These replies will only be limited to our plans of revision according to the advice of the referee, but not extended to specific technical changes in this phase.
Major
- The authors seem to assume that air pollutants at the surface sites and species in Tian-Shan glacier are from local sources in Xinjiang, so emission changes in surrounding regions are not discussed. This is likely not the case, especially for the long-lived ones such as CO. The authors should review relevant studies in the literature on source attribution and/or run airmass back-trajectories to track the sources of pollutants reaching the measurement sites. This would help better understand the observed changes, spatial variation and their relationship with emissions.
Re: Yes, we will review more literatures regarding regional airmass trajectories in Xinjiang and present a general picture of the source, transport and deposition of air pollutants. The observed changes, spatial variation and their relationship with emissions will be better showed in the revision.
- The observed changes are attributed to mobility and emission changes. How about the roles of atmospheric dynamical, physical and chemical processes? Atmospheric transport, dry/wet deposition and chemical reactions should affect the concentrations of the air pollutants. It could be more complicated for the concentrations of ions, BC and OC in snow that involve precipitation and snow melting processes. The direct year-to-year comparisons may be biased due to large interannual variability in these processes. Comparison of 2020 results to longer-term mean might be helpful. More analyses and discussions in this regard are necessary.
Re: Yes, we will extend the air-pollution data back to 2015. The new dataset will be included in the revision.
- How accurate is the snow dating for the recent past back to 2018? The different results of 2019 between the two snow pit profiles need more clarification. What are the possible reasons for the differences? Please clarify.
Re: We substantially comply with the seasonality of stable isotopes to date the snow-pit profiles, while also consider the dust layer and precipitation. We will re-look into these profiles and present more discussion in the later phase.
Minor technical comments: will be checked throughout the paper.
Citation: https://doi.org/10.5194/tc-2021-133-AC2
Interactive discussion
Status: closed
-
RC1: 'Comment on tc-2021-133', Anonymous Referee #1, 10 Jun 2021
Review of “Air pollutants in Xinjiang during the COVID-19 pandemic and glaciochemical records of a Tien-Shan glacier” by Wang et al. submitted to The Cryosphere.
The topic of the paper includes important topics related to the COVID-19 situation and atmospheric quality. Unfortunately, the presentation and analysis of the paper are insufficient in my view for publication in a scientific journal. This relates to many categories that I consider important for a scientific publication, and I can only list a few points here. Most importantly, this study is qualified for publication in The Cryosphere due to several reasons described below.
At first, the relationship between Chinese pollution and COVID-19 have been reported by several groups, and the reports for that region have also already reported (e.g. Zheng et al. 2020 [Zheng, B., Zhang, Q., Geng, G., Shi, Q., Lei, Y., and He, K.: Changes in China's anthropogenic emissions during the COVID-19 pandemic, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2020-355, in review, 2020.]). In the study above, the results for the Xinjiang region were also included. Thus, for the publication of this study, the author should clarify the importance and significance of this study. Otherwise, I do not agree with the publication of the journal The Cryosphere.
Certainly, the results for the snow pit for Urumqi No.1 glacier are something new. However, there are several uncertainties that were not addressed in the main text. Particularly, the age determination of the snow pit and melting and redistribution of ion species should be clearly addressed. Without careful investigation, the conclusions would not be supported.
Overall, I do not think the current writing does not sound scientific, and I do not recommend it for publication. See the detailed comments in the major comments.
Major comments
1. Significance of this paper.
There are many previous studies published on the topic of the relationship between atmospheric quality and COVID-19. The author should describe how this study addresses the remaining problems by comparing other existing studies for this topic. Besides, the author should explain how/why this study should be published in this journal The Cryosphere.
2. Atmospheric pollutants (section 3.1 and related method sections)
In that section, the results and discussion were very briefly shown. The detailed data sets were tucked away in the supplement, but this is not trivial information. In addition, the stages of restriction by the Xinjiang government (stage I to IV) should be explained what these are. Particularly, I think we need to know which kind of changes were required by the governments for the stages.
Additionally, for the interpretation for August to September data, authors concluded in Line 174 “Besides Urumqi, no other prefectures were reported publicly to impose lockdown measures. The concentration of NO2 plunged responding to the lockdown (Figure 2 and S2), implying that the lockdown was not only applied in Urumqi but all other prefectures of Xinjiang”. However, these kinds of information should be asked to the local government directly. It is curious for me that the authors concluded the actual governmental policy based on the atmospheric measurements.
Related to the snow pit results, I think authors should discuss with 2018 data together with the 2019-2020 results. In fact, the authors concluded pollutants for the year 2019 was higher than in 2018 based on the snowpit results. If so, similar results should be obtained from the atmospheric observation.
Overall, I think only Figure 2 and a brief description are not enough for the publication. It is suggested overall to make a deeper analysis of atmospheric pollutants levels between 2018 to 2020 in that region and resubmit the paper, if not to TC may be on a more specific lower impact factor journal.
3. Snowpit results
It is almost impossible for me to judge if or not the conclusions obtained from this study are correct. To evaluate, the age evaluation of these two snow pits and fluxes of ions and impurities should be determined in reasonable ways. In Fig. 3, the authors just determined the age with “with best estimated time annotated on the right (L202-203)”, and thus, I could not evaluate this. Also, in Fig. 4, the authors compared the concentrations of impurities (not fluxes) and concluded the “the snow showed dramatically decreases from 2019 to 2020”, which is not qualified by a reasonable/scientific basis. In addition, impurities concentrations could be redistributed due to melting and refreeze, and thus the comparison with concentration may induce wrong conclusions. I recommend using the flux of the deposition or at least the mass-weighted concentration of each year/season. Overall, it is suggested the analysis of the data is too brief to get a good claim, which is needed for the publication in TC.
4. The increase of atmospheric pollutants from 2018 to 2019
In line 221, the authors concluded the ion species increased from 2018 to 2019, and authors stressed that this is “possibly attributed to increasingly intense emission before the pandemic”. I wonder that this can be tested with the same analysis using atmospheric pollutants data sets as the authors did for 2019 to 2020 in Fig. 2 and S2. If atmospheric pollutants data for that regions do not support this hypothesis, the conclusion based on snow pits both for the increase in 2018 to 2019 nor decrease in 2019 to 2020 by COVID-19 situation would be supported.
The followings are minor points. Note that the minor comments are not exhaustive. This paper should be rewritten correctly, and even if these minor comments are revised, it does not mean that I will recommend it for publication.
Minor comments
L20 Authors only discussed the year 2018 to 2020, and no information available “before 2018” in this study.
L33: byproduct can be replaced by “emissions”.
L37-39:The recent paper showed the opposite conclusions. See Jones et al. 2021 GRL (https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL091883)
L72: What does it mean by “Level 2, 3, 4” here? These are different from the stage for the restrictions? Please write the detail of the restrictions in that area or country, and let the non-Chinese audience understand.
L94: The information shown in Table S2 should not be trivial. Besides, the stages I-IV shown in Fig. 2 should be explained what these are in the method section.
L110: “will” is not appropriate here.
L123: Explain what the standards are. Also, the use of “would” for the method section is not appropriate.
L123-124: Add information of column for IC system.
L148: This sentence is not necessary.
L155: Explain which city was the exception.
L156: Explain using the exact city that the author indicates.
L176: It is very curious. The information for lockdown should be provided by other information (governmental reports etc.) but not by the atmospheric observation. Chicken and egg should not be replaced here.
L147-180: Overall, more discussion is needed, particularly for the links of atmospheric qualities to the stage I to IV and lockdown event during summer.
L220: Covid should be COVID here.
L242: The restriction information should be according to the governmental reports.
L245 and 249: What do authors mean/define by “dramatically”?
L250: I suggest “measure” is changed to “observe”.
L251: This sentence is not necessary to support the conclusion.
L255: The entire paragraph is not necessary.
Citation: https://doi.org/10.5194/tc-2021-133-RC1 -
AC1: 'Reply on RC1', Jing Ming, 21 Jun 2021
Interactive responses to the comments of Referee 1 in Phase 1
The reply to the general view:
The authors appreciate that the general view raised the concerns of our work. They are valuable and helpful to improve the quality of our manuscript in the later phase (the final response). We are thinking of ways to supplement the missing parts and fill up the gaps between our work and the referee’s expectation. In the open discussion phase, we replied to the major comments and talked about our ideas of revision in the next phase.
The reply to the major comments:
- Significance of this paper. There are many previous studies published on the topic of the relationship between atmospheric quality and COVID-19. The author should describe how this study addresses the remaining problems by comparing other existing studies for this topic. Besides, the author should explain how/why this study should be published in this journal The Cryosphere.
Re: There are indeed many studies previously published on the topic of COVID-19 restrictions and air quality. We will explore more next and strengthen the discussion of the topic and highlight our featured points different from other studies. Because our work is regarding with the glacier and snow chemistry besides air pollutants during the pandemic, we choose the Cryosphere as the journal to submit our manuscript after carefully studying its aims and scope before the submission.
- Atmospheric pollutants (section 3.1 and related method sections). In that section, the results and discussion were very briefly shown. The detailed data sets were tucked away in the supplement, but this is not trivial information. In addition, the stages of restriction by the Xinjiang government (stage I to IV) should be explained what these are. Particularly, I think we need to know which kind of changes were required by the governments for the stages.
Additionally, for the interpretation for August to September data, authors concluded in Line 174 “Besides Urumqi, no other prefectures were reported publicly to impose lockdown measures. The concentration of NO2 plunged responding to the lockdown (Figure 2 and S2), implying that the lockdown was not only applied in Urumqi but all other prefectures of Xinjiang”. However, these kinds of information should be asked to the local government directly. It is curious for me that the authors concluded the actual governmental policy based on the atmospheric measurements.
Related to the snow pit results, I think authors should discuss with 2018 data together with the 2019-2020 results. In fact, the authors concluded pollutants for the year 2019 was higher than in 2018 based on the snowpit results. If so, similar results should be obtained from the atmospheric observation.
Overall, I think only Figure 2 and a brief description are not enough for the publication. It is suggested overall to make a deeper analysis of atmospheric pollutants levels between 2018 to 2020 in that region and resubmit the paper, if not to TC may be on a more specific lower impact factor journal.
Re: We would extend the discussion on the restrictions applied by local governments individually to their administrative precincts in the revision, which will take some time and be showed in the final response.
We haven’t ask the local governments directly but to consult some officials in private and look up the open information released on the governments’ websites, newspapers and other media reports. We will extend the discussion on this issue later.
For the data retrieved from the snow pits, the atmospheric observations in 2018 will be included later, and we will discuss with the accordingly new ingredients in the revision. After all, from the concerns raised by the comments, we presume that the discussion in the revision will be greatly strengthened.
- Snowpit results. It is almost impossible for me to judge if or not the conclusions obtained from this study are correct. To evaluate, the age evaluation of these two snow pits and fluxes of ions and impurities should be determined in reasonable ways. In Fig. 3, the authors just determined the age with “with best estimated time annotated on the right (L202-203)”, and thus, I could not evaluate this. Also, in Fig. 4, the authors compared the concentrations of impurities (not fluxes) and concluded the “the snow showed dramatically decreases from 2019 to 2020”, which is not qualified by a reasonable/scientific basis. In addition, impurities concentrations could be redistributed due to melting and refreeze, and thus the comparison with concentration may induce wrong conclusions. I recommend using the flux of the deposition or at least the mass-weighted concentration of each year/season. Overall, it is suggested the analysis of the data is too brief to get a good claim, which is needed for the publication in TC.
Re: In the revising process, we will reconsider the analysis of the data and strengthen the discussion regarding the dating of the snowpit and other concerns raised by the comment.
- The increase of atmospheric pollutants from 2018 to 2019. In line 221, the authors concluded the ion species increased from 2018 to 2019, and authors stressed that this is “possibly attributed to increasingly intense emission before the pandemic”. I wonder that this can be tested with the same analysis using atmospheric pollutants data sets as the authors did for 2019 to 2020 in Fig. 2 and S2. If atmospheric pollutants data for that regions do not support this hypothesis, the conclusion based on snow pits both for the increase in 2018 to 2019 nor decrease in 2019 to 2020 by COVID-19 situation would be supported.
Re: We will extend the dataset back to 2018 or even earlier to validate the preliminary impression in the discussion paper.
The followings are minor points. Note that the minor comments are not exhaustive. This paper should be rewritten correctly, and even if these minor comments are revised, it does not mean that I will recommend it for publication.
Re: According to the major comments, we evaluate that the revised manuscript would be probably rewritten in most parts. We will not expand our replies to the minor comments one by one here and will leave them to the final response phase (Phase 2) complying with the guidance of TC.
Citation: https://doi.org/10.5194/tc-2021-133-AC1 -
RC3: 'Reply on AC1', Anonymous Referee #1, 21 Jun 2021
This is a brief reply to the authors' comment posted. TC and other EGU journals have a discussion phase (Phase 1, opened), and followed by final response & reviews (Phase 2, not opened). However, if there is significant revisions are expected in Phase 1, the reviews for the revised manuscript should not be closed. Otherwise, there is a concern that might hurt the original concept of the "Interactive review process" for this journal.
Citation: https://doi.org/10.5194/tc-2021-133-RC3
-
AC1: 'Reply on RC1', Jing Ming, 21 Jun 2021
-
RC2: 'Comment on tc-2021-133', Anonymous Referee #2, 14 Jun 2021
In this study the authors report some observational analyses of the impact of Coivd-19 pandemic restriction measures on air pollutants in Xinjiang, China, and ions/particles in Tien-Shan glacier. They found that NO2 had a large reduction during certain time periods, compared to small variations in SO2, CO and PM2.5. Soluble ions in Tien-Shan snow samples also decreased by 20-30%, although BC and OC showed no differences from 2018 to 2020. The measurements are new and interesting. However, the paper in its current form reads more like a short measurement report. More in-depth analysis is needed to make the paper more scientifically significant. Please see my specific comments below.
Major comments:
- The authors seem to assume that air pollutants at the surface sites and species in Tian-Shan glacier are from local sources in Xinjiang, so emission changes in surrounding regions are not discussed. This is likely not the case, especially for the long-lived ones such as CO. The authors should review relevant studies in the literature on source attribution and/or run airmass back-trajectories to track the sources of pollutants reaching the measurement sites. This would help better understand the observed changes, spatial variation and their relationship with emissions.
- The observed changes are attributed to mobility and emission changes. How about the roles of atmospheric dynamical, physical and chemical processes? Atmospheric transport, dry/wet deposition and chemical reactions should affect the concentrations of the air pollutants. It could be more complicated for the concentrations of ions, BC and OC in snow that involve precipitation and snow melting processes. The direct year-to-year comparisons may be biased due to large interannual variability in these processes. Comparison of 2020 results to longer-term mean might be helpful. More analyses and discussions in this regard are necessary.
- How accurate is the snow dating for the recent past back to 2018? The different results of 2019 between the two snow pit profiles need more clarification. What are the possible reasons for the differences? Please clarify.
Minor technical comments:
Line 34: has -> have
Line 101: Please check the measurement end date of December 31, 2021.
Line 110: Suggest using present tense for this sentence; Staff should be used as a singular noun here.
Citation: https://doi.org/10.5194/tc-2021-133-RC2 -
AC2: 'Reply on RC2', Jing Ming, 21 Jun 2021
Interactive responses to the comments of Referee 2 in Phase 1
The reply to the general view:
We thank the referee for the encouraging general view of our work and raising the concerns of how to improve the paper significantly. We will address our replies to the comments below. These replies will only be limited to our plans of revision according to the advice of the referee, but not extended to specific technical changes in this phase.
Major
- The authors seem to assume that air pollutants at the surface sites and species in Tian-Shan glacier are from local sources in Xinjiang, so emission changes in surrounding regions are not discussed. This is likely not the case, especially for the long-lived ones such as CO. The authors should review relevant studies in the literature on source attribution and/or run airmass back-trajectories to track the sources of pollutants reaching the measurement sites. This would help better understand the observed changes, spatial variation and their relationship with emissions.
Re: Yes, we will review more literatures regarding regional airmass trajectories in Xinjiang and present a general picture of the source, transport and deposition of air pollutants. The observed changes, spatial variation and their relationship with emissions will be better showed in the revision.
- The observed changes are attributed to mobility and emission changes. How about the roles of atmospheric dynamical, physical and chemical processes? Atmospheric transport, dry/wet deposition and chemical reactions should affect the concentrations of the air pollutants. It could be more complicated for the concentrations of ions, BC and OC in snow that involve precipitation and snow melting processes. The direct year-to-year comparisons may be biased due to large interannual variability in these processes. Comparison of 2020 results to longer-term mean might be helpful. More analyses and discussions in this regard are necessary.
Re: Yes, we will extend the air-pollution data back to 2015. The new dataset will be included in the revision.
- How accurate is the snow dating for the recent past back to 2018? The different results of 2019 between the two snow pit profiles need more clarification. What are the possible reasons for the differences? Please clarify.
Re: We substantially comply with the seasonality of stable isotopes to date the snow-pit profiles, while also consider the dust layer and precipitation. We will re-look into these profiles and present more discussion in the later phase.
Minor technical comments: will be checked throughout the paper.
Citation: https://doi.org/10.5194/tc-2021-133-AC2
Data sets
Footprints of COVID-19 in a Tien-Shan glacier Jing Ming https://doi.org/10.5281/zenodo.4708792
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Xin Zhang
Fanglong Wang
Mengyuan Song
Zhongqin Li
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