Trend Analysis and Spatial Source Attribution of Surface Ozone in Chaozhou, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study is aimed at evaluating the long-term changes in surface ozone concentration in the vicinity of Chaozhou, China and the identification the direction of its sources. Surface ozone is a significant pollutant that influences on the human health and the environment especially in the large urban areas. Therefore, the understanding of the causes of ozone concentration variability can help to predict and mitigate its future changes.

The authors of the manuscript analyzed the temporal variability in the daily maximum 8-hour average ozone concentrations obtained from a number of environmental monitoring stations in Chaozhou using several statistical methods, including filtering techniques, analysis of the variances, percentile regression, backward trajectories and cluster, sector, and sources analysis.

To my opinion, the manuscript is well-written and has very good logical structure. Figures and tables are self-sufficient, and well-understandable; they reflect the analysis made by the authors. The authors have done a lot of analysis using modern statistical methods. But to my mind, the manuscript suffers from the lack of analysis of physical and chemical reasons of the results obtained as well as the lack of the overview of the previous studies. Some explanation of the causes of surface ozone variability taking into account its sources and sinks in the atmosphere could significantly strengthen the significance of the study.

In general, the study has scientific significance as it contributes to investigation of the variability in ozone concentrations in specific region. This study is useful for other researchers and is relevant to the scope of the journal. But the estimates given by authors sometimes suffer from the lack of statistical significance. Even the authors use the statistical methods for their analysis they do not present any confident intervals for estimates obtained (trends, correlation coefficients). 

Discussion and most of the conclusions are reasonable and relevant to the scope of the study presented. The introduction section should be improved by adding the information on sources and sinks of surface ozone in general and in the region considered with the overview of other studies in this field and the place of the current study among others.

After some revision this manuscript could be published in the journal. 

Minor comments are in the file attached.

Comments for author File: Comments.pdf

Author Response

Thank you very much for taking the time to review this manuscript. We sincerely appreciate your detailed review and constructive comments, which have significantly contributed to improving our study. We have carefully considered each suggestion and made the corresponding revisions and corrections, which are highlighted in track changes in the re-submitted files. Please find our detailed responses and the specific revisions made in response to your comments below. Your feedback has been invaluable in enhancing the clarity, depth, and overall quality of our manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript prepared by Huang et al. titled “Trend Analysis and Spatial Source Attribution of Surface Ozone in Chaozhou, China” employs advanced statistical and modeling techniques to assess long-term trends in surface ozone concentrations and identify their sources in Chaozhou, China. Utilizing the Kolmogorov-Zurbenko filter and percentile regression, the study documents a general long-term decrease in daily maximum 8-hour average ozone levels, which is punctuated by significant seasonal fluctuations. Additionally, the research employs trajectory cluster analysis, trajectory sector analysis, and potential source contribution function analysis to pinpoint the geographical origins of ozone pollution, finding significant contributions from northeast air masses. This comprehensive methodology provides a robust framework for understanding both the temporal dynamics and spatial sources of ozone in Chaozhou, contributing valuable insights into effective air quality management strategies. The findings suggest that while local emission control measures have been effective, regional transport of pollutants plays a significant role in local air quality, underscoring the need for regional collaboration in pollution management. The topic is highly relevant to the journal and the manuscript is well organized. Overall, I am happy to recommend the paper for publication in Atmosphere after a minor revision.

 

Major comments:

1.     Please provide a more detailed description of the effects of ozone pollution, including its impacts on human health, ecosystems, and other relevant environmental aspects in the introduction.

2.     You reference numerous standards, regulations, and policies specific to China, which may not be familiar to all readers. I recommend either providing a more detailed explanation of these within the text or considering their removal if they do not directly contribute to the core findings of the study.

3.     In the abstract, you indicate that Chaozhou's elevated ozone levels are influenced by both regional transport and local emissions. However, the main text references only one publication and provides a rather general discussion on local ozone sources. Could you please include additional studies or data specific to ozone production in this region? A more detailed discussion on this topic would enhance the manuscript's depth and provide a clearer understanding of the local and regional dynamics affecting ozone levels.

Minor comments:

1.     Please specify the study period clearly in the abstract to provide readers with immediate context regarding the temporal scope of your research.

2.     Line 63: “O3 has a relatively long atmospheric lifetime” of about….?

3.     Lines 94-96: Please provide the information on the measurement methods used, time period covered by the data, quality of the data, etc.

4.     Lines 208-210: Are these trends statistically significant? Please give the p-value.

5.     Line 219, 228: What does the “secondary standard” or “second-level standard” mean and why 160ug/m3 has been chosen as a criterion?

6.     Line 230: I would not use the word “significant”.

7.     Lines 233-235: The logic presented here is incomplete. Please consider including a discussion of the adverse health effects associated with high levels of ozone either here or in the introduction.

8.     Line 237: Please provide more specific descriptions in the captions for the two plots. The current captions are unclear and may lead to confusion.

9.     Lines 258-260: I disagree with the conclusion as stated. The variance analysis indicates that the short-term component predominantly controls the variation, which is expected. However, the long-term component also contributes to the general trend of ozone concentration. It may not be accurate to describe the long-term component's influence as "negligible."

10.   Lines 316-327: What about clusters B and D?

Author Response

Thank you very much for taking the time to review this manuscript. We sincerely appreciate your detailed review and constructive comments. We have carefully considered each suggestion and made the necessary revisions to our manuscript. Specifically, we have expanded the introduction to include more comprehensive background information and relevant references, enhanced the methods section with more detailed descriptions of the techniques used, and ensured that our conclusions are well-supported by the results. We believe these revisions address your concerns and improve the clarity and significance of our study. Thank you for your valuable feedback and recommendation for publication.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This study analyzed the temporal trends and spatial sources of ozone pollution in Chaozhou using a long-term dataset covering years 2014-2023. Multiple analysing methods have been used including KZ filter and percentile regression focusing on daily maximum 8-hr moving average (MDA8) ozone. A long-term decreasing trend in MDA8 ozone and seasonal fluctuation were found. To elucidate the origins of the measured ozone, authors conducted trajectory cluster analysis - trajectory sector analysis (TSA) and potential source contribution function (PSCF) analysis, from which they concluded that Chaozhou's elevated ozone levels are influenced by both transported air pollution from the northeast and local emissions. This finding adds valuable knowledge regarding the controlling factors governing local air quality and health. This manuscript fits well the journal scope and is written. I recommend publishing this manuscript in this journal after a minor correction. Below are my comments for the authors to consider. 

Comments: 

Line 103-105: what is the unit for the sliding window length m in KZm,p (X)?  What do they mean 15, 365, and 5 band 3 in KZ15,5 (X) and KZ365,3 (X) ? 

Line 206: change section 3.1 to “General characteristics of yearly and seasonal O3 distribution” to highlight your seasonal work in Fig. 2b. 

Line 227: the word “orderly” used here causes confusion, what do you mean? Better to say “… exhibited seasonal fluctuations, eg with two peaks occurring in Oct and April”?

Line 229: better to mention "Ambient Air Quality Standards" (GB3095-2012) in an early stage where the second-level standard (160 μg/m3) was firstly mentioned, eg in Fig. 2 legend.  

Line 230: you need to explain what "M" shaped curve in Figure 2(b) means, eg “with a significant summer minimum in June-August and enhanced ozone in spring and autumn”, and then briefly explain why.  One factor that I can see is that it is likely related to the change of air mass origin in summer, as the major air mass comes from southeast cluster E (in fig 5-7), where has the least air pollution.    

Line 262-263: Figure 3’s legend is too simple; you need to add more detailed information to allow readers to understand what you are showing in this figure without going to the text. What is “its short-term component (b)”?  

Line 270: a full stop missed. 

Line 290: again, the current legend is too short.

Legend in Figures 6-10: a full stop missed at the end of the sentence.

Line 357: (i) Legend of Figure 8 is too simple, add more information. Eg what is shown in sub-panel a, b and c? (ii) the dashed/dotted lines used in panel b and c are too thin to be read.

Line 373-374: Change figure 9 legend to “Sector average concentration (a) and relative contribution (b) for O3 in Chaozhou during the study period”. 

Comments on the Quality of English Language

Line 145: duplicated words in “models to models”

Line 284: duplicated words here in “further and further”

Author Response

Thank you very much for taking the time to review this manuscript. We sincerely appreciate your detailed review and constructive comments, which have significantly contributed to improving our study. We have carefully considered each suggestion and made the corresponding revisions and corrections, which are highlighted in track changes in the re-submitted files. Please find our detailed responses and the specific revisions made in response to your comments below. Your feedback has been invaluable in enhancing the clarity, depth, and overall quality of our manuscript.

Author Response File: Author Response.pdf