Review Reports

Round 1

Reviewer 1 Report (Previous Reviewer 4)

Comments and Suggestions for Authors

The manuscript has been improved considerably.

Presently, it is in must better conditions.

However, some improvements should be done.

A list of symbols or abbreviations would be very useful.

Citations’ format should be corrected.

First, read the pdf file “comments 3939506a”.

Second, pay attention to the format of the text, figure, and tables. The tables are wrongly numerated.

Other issues:

1 – The first paragraph of the Introduction (section 1) needs to be improved (see comments). The text in between lines 35 and 50 must be reorganized.

2 – Pay attention to the PM2.5 that should be PM_2.5 through the text.

3 – Figure 1 is too width.

4 – Pay attention to the format of the units’ parameters presented in the text. Micron is not used anymore, now is micrometer. Use μm.

5 – Each time you mentioned in the text… several authors presented …. use the citations [x1, x2, x3]. Show at least two or three citations… Cite the studies when mentioning them.

5 – Format the tables and pay attention to their numeration.

6 – Pay attention to time hour format. 6 am or 6:00 am. Standard the format through the text.

7 – Do not use bold style in the text.

8 – Each time a statement is done and is from several studies, please use a citation.

9 – References were not checked.

Comments for author File: Comments.pdf

Author Response

Comment 1: The manuscript has been improved considerably.

Response 1: Thank you for your careful guidance, which is a great inspiration for my future research.

 

Comment 2: Presently, it is in must better conditions.

Response 2: I have carefully read your very detailed handwriting suggestions and made all revision.

 

Comment 3: However, some improvements should be done. A list of symbols or abbreviations would be very useful.

Response 3: I have added a list of symbols or abbreviations. It is placed after acknowledgement. This is the place required by Atmosphere.

 

Comment 4: Citations’ format should be corrected.

Response 4: I have formatted all the citations based on your comments.

 

Comment 5: First, read the pdf file “comments 3939506a”.

Response 5: Thanks again for your effort in providing a so detailed suggestion.

 

Comment 6： Second, pay attention to the format of the text, figure, and tables. The tables are wrongly numerated.

Response 6: The sentence with the wrong table number that you saw should be deleted before last round submission because I did not coordinate well with the internal editor, which resulted in that sentence not being deleted. I have checked the table and image numbers for accuracy.

Comment 7: Other issues:

1 – The first paragraph of the Introduction (section 1) needs to be improved (see comments). The text in between lines 35 and 50 must be reorganized.

Response 7: I have totally followed your suggestion to reorganize this part.

 

Comment 8: 2 – Pay attention to the PM2.5 that should be PM_2.5 through the text.

Response 8: I have changed all PM2.5 to PM_2.5.

Comment 9：3 – Figure 1 is too width.

Response 9: I have changed the size of the figure based on your suggestion.

Comment 10: 4 – Pay attention to the format of the units’ parameters presented in the text. Micron is not used anymore, now is micrometer. Use μm.

Response 10: I have revised all the units’ parameters related issues based on your suggestions

Comment 11: 5 – Each time you mentioned in the text… several authors presented …. use the citations [x1, x2, x3]. Show at least two or three citations… Cite the studies when mentioning them.

Response 11: I have revised to ensure each time I mentioned in the text Cite the studies when mentioning them.

Comment 12: 5 – Format the tables and pay attention to their numeration.

Response 12: I have tried to format the tables and check the numeration.

Comment 13: 6 – Pay attention to time hour format. 6 am or 6:00 am. Standard the format through the text.

Response 13: I have uniformly adopted a 24-hour clock system in the text

 

Comment 14: 7 – Do not use bold style in the text.

Response 14: I am sorry for the negligence. I have corrected this issue.

Comment 15: 8 – Each time a statement is done and is from several studies, please use a citation.

Response 15: I have provided citation for all the statement which require to be cited.

 

Comment 16: 9 – References were not checked.

Response 16: I have checked the consistency between the citation numbers and the article in the reference list. Because the editorial office only gave me five days for minor revisions, I can only allocate a portion of my time each day for revising articles. Everything else has been changed, but there is no time to completely unify the reference format into MDPI style. During the proofreading stage of MDPI journals, authors will be required to make improvement of reference list in editor’s assistance. I hope you can allow me to adjust the reference list during that stage. 

 

Reviewer 2 Report (Previous Reviewer 3)

Comments and Suggestions for Authors

The authors address all of my comments. Just one minor comment, all "2.5" and "2" for PM_2.5 and NO_2 etc. should be underscripted. Also, the tables should be rearranged in better manners, now the spacing has some problems.

Author Response

Comment 1: The authors address all of my comments. Just one minor comment, all "2.5" and "2" for PM_2.5 and NO_2 etc. should be underscripted.

Response 1: Thanks again for your suggestions. I have correct all the issue to ensure underscripts are added wherever it is needed

Comment 2: Also, the tables should be rearranged in better manners, now the spacing has some problems.

Response 2: I have tried to adjust the table to better arrange it, and some of the spacing issues between pages are caused by converting Word to PDF. I will make further adjustments as needed during the proofreading process.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

 

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I reviewed the revised version of the manuscript, and the authors have done an excellent job. I have no further comments.

Reviewer 2 Report

Comments and Suggestions for Authors

Thank you. Congrats on your improvements of the paper. I am satisfied with the changes.

Reviewer 3 Report

Comments and Suggestions for Authors This review paper explores how green space could positively and negatively affect PM2.5 concentrations in different spatial scales, including macro and meso scales. The explanations are provided with the aid of CFD models, and the conclusion also includes something about the synergistic effect of vegetation and meteorological conditions. The topic is interesting, however, the review report is rather long, and lack of a focus and scientific novelty (though it's a review paper, one should have a clear emphasis, and now it's quite scattered). Further, there are some major points to be addressed in revising the current manuscript:   (1) Abstract is too long, please shorten it accordingly. Also, the abstract includes some sentences with regard to future research, which should definitely not appear in Abstract section, but certainly, one may put these wordings into Conclusion of the review paper.   (2) In Introduction, for undesirable health effects of PM2.5, please also take reference to Table 1 of https://www.mdpi.com/1660-4601/18/12/6532,  and the adverse effects mentioned in https://www.sciencedirect.com/science/article/pii/S2666765724001212 . Please add these 2 references accordingly.   (3) In Introduction, "Many researchers have pointed out that urban green space can have a significant impact on particulate matter" - what kind of urban green space are you referring to? Please provide a clear definition before discussing.   (4) Line 97: "close the research gap and guide future research" - what are the research gaps induced based on the past literature? Also, what is the key importance of future research in relevant disciplines? Please take reference of some recent literature too.   (5) Section 2. Method - please provide a brief description of the 118 research, in terms of category, fields, focus and country / city investigated. Also, what is the detailed criteria of the selection of these 118 research papers?   (6) Section 3. It seems that the title of the heading should be modified - as the sub-sections refer to "amount of PM2.5 reduced by green space", "impact of green space structure on PM2.5 concentrations", "The impact of green space spatial pattern on PM2.5 from the perspectives of landscape ecology and morphology" etc. Thus, the use of the wording "global, regional, urban, central urban scale" are not appropriate. Also, the authors have provided too much details in the Table, with each key finding in each paper investigated, however, one should actually categorize these findings and discuss the ideas from another perspective, e.g., how many research papers obtain / acquire such finding based on a specific method (which can be statistical approach / modeling approach) etc. The existing categorization (by city of China) seems quite scattered, and similar research finding may be applied to many of these cities at the same time. Therefore, the reorganization of Section 3 (especially the tables) must be conducted before resubmission.   (7) Section 4.1 mentions that most studies adopted "reduction rate" as an indicator to determine how road greening could affect PM2.5 concentrations. However, are there any assumptions behind the scene before one can adopt such indicator for quantification? In lines 370-371, the authors also mentioned that researchers only revealed its positive effects without revealing the mitigating effects, but how could this be remedied? Please provide some elaborations here and extensions involved.   (8) Table 3 should be grouped based on the method being adopted, for example, the two studies that adopted CFD model (or similar modeling approaches) should be put together for analysis, so that similarities and differences can be shown immediately. Also, the main findings of some of these studies are rather vague and lack of clarity. Same applies to Table 4. Assumptions of different studies should also be stated clearly in all relevant tables.   (9) Section 4.2 explores how green spaces could affect residential areas. How is the term "residential" being defined? Due to mixed land use pattern within different cities of China (attributed to modern spatial development), it's extremely hard for one to categorize a particular region as "residential area", so perhaps having a percentage of land pixels will be better. Also, linear pollution sources from traffic emissions (Line 413) will also cause effects to residential areas. Further, in Line 431, what do you mean by "buffer formed by greening"? Please clarify.   (10) Section 4.3 (Lines 468-469) - about the land use regression model adopted, what are the assumptions, set-up etc.? Different set-ups and modeling settings will likely lead to different conclusions. Also, some of the sentences in Section 4.3 are not supported by scientific grounds and basis, for example Lines 475-476, it might be better if some statistical values and scientific evidence is added.   (11) Lines 478-480: "Because different characteristics like meteorology, terrain, built environment, human activities, emission source, the impact of industrial area greening in different cities on PM2.5 can also have some differences." - need to add in details and elaborations, refer to how sustainability features related to greening are being incorporated into reducing air pollution and enhancing regional and local health qualities and liveability, for example, the following reference should be acknowledged: https://pmc.ncbi.nlm.nih.gov/articles/PMC4556255/ https://www.mdpi.com/2071-1050/13/16/8781  https://www.sciencedirect.com/science/article/abs/pii/S1618866716301170   (12) For section 4.4, it's better to describe clearly the actual meaning of "campus" - are you referring to secondary school or university campus, or entertainment facilities for young people, or other facilities? For "negatively correlated" and "positively correlated" mentioned in this paragraph, please input some statistics into the manuscript.   (13) For section 4.5, how are the measurements at park being conducted? In particular, at what vertical level for obtaining vertical distribution? Also, what which prescribed spatial domain are you referring to?   (14) For Section 5, certainly the characteristics and category of plants are important, but the context here is rather detailed, One should shorten it and provide a better summary.   (15) Table 3 should group studies of the same "regulatory mechanism studied" into the same box.   (16) The Conclusion of this study should link to future city development, how relevant greening policies can be implemented, designed and facilitated in regional and local context, how to promote citizen science for enhancing public awareness on greening features and facilities, as well as how to promote the reduction of air pollution within different spatial contexts. Relevant past literature should also be included into the manuscript for in-depth discussions of aforementioned ideas.   Overall speaking, the topic is interesting, but Major Revision is needed for sure, to brush up the quality of the manuscript, and to make better and clearer tables by summarizing and synergizing relevant information into the same row. 

Author Response

Comment 1: Abstract is too long, please shorten it accordingly. Also, the abstract includes some sentences with regard to future research, which should definitely not appear in Abstract section, but certainly, one may put these wordings into Conclusion of the review paper.

Response 1: We sincerely appreciate the reviewer’s detailed review of this article and the valuable suggestions you have put forward. Your suggestions that the Abstract is too long and that future research directions should not be included in the Abstract are very pertinent. We fully accept them and have revised the paper according to your opinions. We have significantly streamlined the Abstract section, eliminating redundant descriptive content and retaining only core information about the study, including the research background, objectives, methods, main findings, and conclusions.

Comment 2: In Introduction, for undesirable health effects of PM2.5, please also take reference to Table 1 of https://www.mdpi.com/1660-4601/18/12/6532,  and the adverse effects mentioned in https://www.sciencedirect.com/science/article/pii/S2666765724001212 . Please add these 2 references accordingly.

Response 2: You suggested that we supplement the adverse effects of PM_2.5 on health in the Introduction section and cite the relevant content from two studies (Mak H W L et al, 2021 and Sangkham S et al, 2024). This suggestion is very important and helps to elaborate on the health risks of PM_2.5 more comprehensively. Based on your suggestions, we have revised the Introduction; supplemented the negative impacts of PM2.5 on the respiratory system, cardiovascular system, and children's health; and cited the two studies you mentioned.

Comment 3: In Introduction, "Many researchers have pointed out that urban green space can have a significant impact on particulate matter" - what kind of urban green space are you referring to? Please provide a clear definition before discussing.

Response 3: We sincerely appreciate the reviewer’s constructive suggestion. According to your suggestion, we have supplemented the definition of "urban green space" in the Introduction. Specifically, urban green space refers to the areas with vegetation coverage in a city, including but not limited to parks, street greening, residential area green space, industrial area green space, campus green space, vertical greening (such as green walls and green roofs), etc. (Diener & Mudu, 2021). The scale of these green spaces varies from the macro (such as urban forests) to micro (such as individual plants) scales, and the influence mechanisms of their structural and functional differences on particulate matter are also different.

Comment 4: Line 97: "close the research gap and guide future research" - what are the research gaps induced based on the past literature? Also, what is the key importance of future research in relevant disciplines? Please take reference of some recent literature too.

Response 4: We have used the sentences below to show the importance of this review (you can also find these sentences in the Introduction of the article). Because English is not our first language, we are not sure whether the phase “research gap” can be used in a review article, so we have removed this phrase but still explain what research has not been but needs to be conducted.  

“Since the 1990s, the number of studies related to the impact of green spaces on PM2.5 concentrations has increased rapidly. With various studies conducted at different times, in different places, at different scales, and using different methods, people have gradually realized that green space can not only reduce PM2.5 concentrations but also exacerbate PM2.5 pollution, especially in some micro-environments. To the best of our knowledge, no one has comprehensively reviewed this topic from a global perspective. Thus, in this study, we aim to comprehensively review this subject and guide urban green space managers in managing green space to reduce atmospheric PM_2.5 pollution in a more effective way.”

 Comment 5: Section 2. Method - please provide a brief description of the 118 research, in terms of category, fields, focus and country / city investigated. Also, what is the detailed criteria of the selection of these 118 research papers?

Response 5: We rewrote the Methods to provide a clearer explanation about how we selected the 118 articles.

“The global databases Web of Science, Engineering Village, and ResearchGate were selected as our search engines. The timeframe we set to search for articles ranged from 1995 to 2024. The types of articles selected were journal articles and reviews. In order to retrieve all the relevant articles related to the effects of green space on PM2.5 concentrations, we did not limit the fields, scales, countries, or cities investigated. As long as an article was related to our search aim (i.e., it explored the positive and/or negative effects of green space on PM2.5), it was selected. To comprehensively retrieve all the relevant articles, we listed all the terms synonymous with PM2.5 and green space and combined them one by one (Figure 1 shows all the keywords used). Every time we used one combination (like fine particles and parks) in a search, we then downloaded all the relevant articles and then changed to another combination. We continued to employ this approach until we had used all the effective combinations. Ultimately, we retrieved and downloaded 118 articles. “

Comment 6: Section 3. It seems that the title of the heading should be modified - as the sub-sections refer to "amount of PM2.5 reduced by green space", "impact of green space structure on PM2.5 concentrations", "The impact of green space spatial pattern on PM2.5 from the perspectives of landscape ecology and morphology" etc. Thus, the use of the wording "global, regional, urban, central urban scale" are not appropriate.

Response 6: We are sorry. We have revised all headings. For section 3, the new headings are as follows:

3. Effects of regional and urban green space on PM2.5.

3.1 The amount of PM2.5 reduced by regional or urban green space

3.2 The impact of regional and urban green space structure on PM2.5

3.3 The impact of regional and urban green space spatial pattern on PM2.5 from the landscape ecology and morphology perspective

I think these revisions now better align with our subject background. Since we are urban planners, we not only focused on regional or urban master plans (including green space master plans) but also focused on detailed plans for roads, residential areas, and other specific areas (including relevant detailed green space plans).

Comment 7: Also, the authors have provided too much details in the Table, with each key finding in each paper investigated, however, one should actually categorize these findings and discuss the ideas from another perspective, e.g., how many research papers obtain / acquire such finding based on a specific method (which can be statistical approach / modeling approach) etc. The existing categorization (by city of China) seems quite scattered, and similar research finding may be applied to many of these cities at the same time. Therefore, the reorganization of Section 3 (especially the tables) must be conducted before resubmission.

Response 7: Due to significant differences in urban spatial forms, pollution source distribution characteristics, microclimates, etc., the Brownian motion of PM2.5 and turbulence in wind environments themselves are irregular movements. During our review process, we found significant differences in the research findings across different locations and times. In addition, there may be significant differences within the same region due to variations in research scale. I have reclassified the research into three categories, each with some common characteristics in terms of research findings. We have placed each category of research in a separate table. There are significant differences in research findings within the same category due to factors such as different cities, time periods, and scales. The table is just right for comparing these differences. Finally, we also summarized that overall, although these large-scale studies all support improving green space ratios, there are significant differences in how to adjust the form of green spaces, the distance between green spaces, and the number of green patches from different cities, times, and scales. There is no fixed method that can be applied to all cities at all times and scales. Therefore, the optimization of urban green space pattern aimed at reducing PM2.5 needs to be tailored to region or city conditions and targeted strategies should be proposed. You can find specific changes in the corresponding section.

Comment 8: Section 4.1 mentions that most studies adopted "reduction rate" as an indicator to determine how road greening could affect PM2.5 concentrations. However, are there any assumptions behind the scene before one can adopt such indicator for quantification? In lines 370-371, the authors also mentioned that researchers only revealed its positive effects without revealing the mitigating effects, but how could this be remedied? Please provide some elaborations here and extensions involved.

Response 8：I have reread all the relevant studies, as mentioned in the two Discussion paragraphs in the corresponding section of the article. The current studies selected certain indicators to explore the impact of green spaces on PM2.5, using reduction rates and other criteria as criteria to quantify the effect of green spaces on PM2.5. The current study does not imply any underlying assumptions. Due to significant differences in the spatial form, microclimate, and greening characteristics of street valleys in different studies, as well as differences in research methods and criteria, there are significant differences in the relevant findings among different studies. I suggest that future studies should focus on under what conditions road greening has a positive impact on PM2.5 and under what conditions it has a negative impact, and future researchers can explore this from the perspective of the mechanism to reveal the reasons behind the distinct phenomena. You can refer to the second and third paragraphs of Section 4.1 for details.

Comment 9: Table 3 should be grouped based on the method being adopted, for example, the two studies that adopted CFD model (or similar modeling approaches) should be put together for analysis, so that similarities and differences can be shown immediately. Also, the main findings of some of these studies are rather vague and lack of clarity. Same applies to Table 4. Assumptions of different studies should also be stated clearly in all relevant tables.

Response 9: I have read the research in Tables 3 and 4 again and rewrote the contents. The research in the new Table 3 is all based on actual measurements, while the research in Table 4 is entirely based on CFD simulations. I tried my best to ensure a clearer and more accurate description of all the research. I have added a Parameter (s) column to provide a more detailed description of what indicators each study focuses on. Due to the different research conditions, such as the fact that measured studies have not completely excluded interference from sources other than traffic, while simulated studies have been conducted under relatively ideal conditions, there are inherent differences between measured and simulated studies. By comparing Tables 3 and 4, it can be seen that both measured and simulated studies have found that (1) road green spaces exacerbate PM2.5 pollution; (2) road green spaces reduce PM2.5 pollution; and (3) depending on the specific situation, road green spaces may either exacerbate or reduce PM2.5 pollution. Therefore, the differences cannot be attributed to the influence of other source types, or simulation studies are too ideal to fully consider all pollution sources. We have pointed out in the article that the viewpoints of all researchers are not contradictory to each other due to the differences caused by various factors such as the street environment they studied (road width, street aspect ratio, etc.), green coverage characteristics (green coverage rate, tree species, crown width, etc.), microclimate (wind, temperature, humidity, rainfall, etc.), even research methods, and judgment indicators (some judge the effect based on vertical reduction rate, and some choose fixed observation points at the horizontal level as judgment criteria). This review can piece together research from different disciplinary backgrounds, research locations, and spatial parameters to facilitate subsequent researchers to continue their research. However, due to the diverse environmental features such as street environments in different studies, we believe it is difficult to derive an absolute viewpoint simply by comparing several studies that works perfectly in all street environments.

 Comment 10: Section 4.2 explores how green spaces could affect residential areas. How is the term "residential" being defined? Due to mixed land use pattern within different cities of China (attributed to modern spatial development), it's extremely hard for one to categorize a particular region as "residential area", so perhaps having a percentage of land pixels will be better.

Response 10: Thank you very much for your suggestion. Our discipline background is urban and rural planning, and we usually define residential land use area as residential areas. In China, urban land can be classified, with residential land areas being an important part. You can refer to reference 1 (on land classification) below for more information. Nowadays, urban land use is mixed, but relevant practitioners will use methods such as kernel density analysis to define areas with mostly residential land as residential land. I have studied abroad in the UK, and I believe that residential area is a commonly used term that can be adjusted according to research needs. You can consider a gated residential community as a residential area, and sometimes, urban and rural planning practitioners may define multiple residential communities as a residential area. For example, in reference 2 below, “residential area is directly used in the title. This part mainly reviews microscale studies, which involve conducting field measurements within residential areas or using simulation software to simulate residential communities. So, these studies are conducted in residential areas.

1. Ziming Li,Bin ChenCA1,Yufei Huang,et al. Enhanced mapping of essential urban land use categories in China (EULUC-China 2.0): integrating multimodal deep learning with multisource geospatial data[J]. Science Bulletin,2025,.
2. Wojnowska-HeciakCA1,P. Sikorski,J. Ciemniewska,et al. Stakeholder perceptions of biodiversity in urban residential areas[J]. Journal of Environmental Management,2025,Vol.382: 125368.

 

Comment 10: Also, linear pollution sources from traffic emissions (Line 413) will also cause effects to residential areas.

 Response 10: Indeed, multiple sources of PM2.5 are widely present and interact with each other in the environment, and the flow of pollutants in the air is extremely complex. Currently, most studies have not separated a single source of PM2.5 separately for research. For example, research conducted on vehicular lanes mainly focuses on traffic sources, but other unavoidable sources may have an impact. Similarly, residential areas also have many types of PM2.5 sources, but household sources undoubtedly make important contributions. Our review is classified based on relevant research, and there are currently some studies focusing on PM2.5 in residential areas, so we classified them in this way.

Comment 11: Further, in Line 431, what do you mean by "buffer formed by greening"? Please clarify.

Response 11: I am sorry. I have read the original article again and used “residential areas located behind Planting bands” to replace the original statement.

Comment 12: Section 4.3 (Lines 468-469) - about the land use regression model adopted, what are the assumptions, set-up etc.? Different set-ups and modeling settings will likely lead to different conclusions. Also, some of the sentences in Section 4.3 are not supported by scientific grounds and basis, for example Lines 475-476, it might be better if some statistical values and scientific evidence is added.

Response 12: I have rewritten the whole section and for the regression model study, I provided more information.

 “Han et al. (2020) [69] used a land use regression model to study PM2.5 during the hot season in Xi'an, China. The study included a large number of monitoring points, buffer zones, and localized emission source variables (covering information on land use, road traffic source facilities, socio-economic conditions, emission sources, and geographic spatial data). A linear model was constructed through stepwise regression, and it was found that PM2.5 during the hot season in Xi'an, the spatial distribution of PM 2.5 is closely related to the layout of industrial land, with industrial emissions contributing more than transportation. Green spaces, especially large-scale green spaces, can effectively reduce PM2.5 concentrations.”

 I have also added relevant data for the study in the original lines 475-476. The R² values are the only relevant values the authors provided.

“In addition, Bikis (2023) [70] found that the green spaces near roads and in industrial areas of Addis Ababa, Ethiopia, are lacking. The correlation between the occurrence of air-quality-related health problems and the air quality index at 12 transportation stations corresponded to an R² =95.47% in terms of average concentration. In addition, the correlation between the air quality index and air-quality-related health problems with respect to manufacturing industry employees was stronger (R2 = 97.28%). These results confirmed that the manufacturing industry emits more pollutants than transportation. These factors can raise PM_2.5 concentrations in these areas. Increasing the amount of green space in industrial and road areas is an effective way of solving this problem.”

Comment 13: Lines 478-480: "Because different characteristics like meteorology, terrain, built environment, human activities, emission source, the impact of industrial area greening in different cities on PM2.5 can also have some differences." - need to add in details and elaborations, refer to how sustainability features related to greening are being incorporated into reducing air pollution and enhancing regional and local health qualities and liveability, for example, the following reference should be acknowledged:

https://pmc.ncbi.nlm.nih.gov/articles/PMC4556255/

https://www.mdpi.com/20711050/13/16/8781 

 https://www.sciencedirect.com/science/article/abs/pii/S1618866716301170.

Response 13: During the revision, I determined that it may be better to put these in Section 7. So, I moved the original paragraph in the article and the articles you suggested to Section 7:

Relevant studies have been added as [110-112].

[110] Andrew Chee Keng · Lee/Lee AC,Hannah C · Jordan/Jordan HC,Jason · Horsley/Horsley J. Value of urban green spaces in promoting healthy living and wellbeing: prospects for planning.[J]. Risk management and healthcare policy,2015,Vol.8: 131-137.

[111] Chi, Yan Ling,Mak,et al. From Comparative And Statistical Assessments Of Liveability And Health Conditions Of Districts In Hong Kong Towards Future City Development[J]. Sustainability (Switzerland),2021,Vol.13(16): 8781.

[112] Chan, CS (Chan, Chung-Shing). Health-related elements in green space branding in Hong Kong[J]. URBAN FORESTRY AND URBAN GREENING,2017,Vol.21(1): 192-202.

 Comment 14: For section 4.4, it's better to describe clearly the actual meaning of "campus" - are you referring to secondary school or university campus, or entertainment facilities for young people, or other facilities? For "negatively correlated" and "positively correlated" mentioned in this paragraph, please input some statistics into the manuscript.

Response 14: The campus we mentioned is the entire school campus (include primary campus, secondary campus, and university campus); the study we cited not only conducted research at its secondary school but also conducted some at the university campus, but we classified this as a single class. We also tried to provide a clearer explanation about this in the article.

“School campuses are important places of study from kindergarten to university. A healthy school campus environment is quite important for the student population.  ”

I have provided the statistical information for relevant findings about correlations.

 

Comment 15: For section 4.5, how are the measurements at park being conducted? In particular, at what vertical level for obtaining vertical distribution? Also, what which prescribed spatial domain are you referring to?

Response 15: I have rewritten the whole section to provide detailed information about how measurements at the park were conducted.

For the study about vertical distribution, I have added detailed information.

“They collected PM2.5 concentration at 1.5m, 10m, 25m, 35m, 50m, 65m, 80m, 100m height at the building collection point and the forest park.”

These studies collected data at urban parks. The studies tries to explore the impact of urban parks on PM2.5 by comparing the difference between PM2.5 concentration inside and outside of the parks.

Comment 16: For Section 5, certainly the characteristics and category of plants are important, but the context here is rather detailed. One should shorten it and provide a better summary.

Response 16: I have rewritten this section and divided it into three paragraphs.

The first paragraph is mainly about the impact of plants on PM2.5 is an extremely complex and comprehensive process.

The second paragraph is about the significant differences in the impact of different tree species and even different parts of the same tree on PM2.5.

The third paragraph is mainly about the impact of different microclimate conditions for plants on PM2.5 also showing significant differences.

 

Comment 17: Table 3 should group studies of the same "regulatory mechanism studied" into the same box.

Response 17: I have divided the research into four tables (deposition, blockage, adsorption, and absorption), read those articles again, and rewritten the tables.

Comment 18: The Conclusion of this study should link to future city development, how relevant greening policies can be implemented, designed and facilitated in regional and local context, how to promote citizen science for enhancing public awareness on greening features and facilities, as well as how to promote the reduction of air pollution within different spatial contexts. Relevant past literature should also be included into the manuscript for in-depth discussions of aforementioned ideas.

Response 18: I have added a Discussion section and rewritten the Conclusions section. I used relevant studies to explore how to carry out relevant optimization from the perspective of urban spaces. However, due to the extremely complex process of the impact of greening on PM2.5, we have attempted to propose effective suggestions. However, due to the complex mechanism of action and limited current research, we can only provide a few optimization suggestions. But, our article undoubtedly helps people better understand the complexity of the impact of greenery on PM2.5.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have made some improvements to the text but have not considered the most important requests made by at least one of the reviewers.

The text keeps repeating ideas and statements.

The text has problems with units, etc.

The authors don't use scientific words.

The text does not use abbreviations for various written expressions that are continually repeated (e.g. particulate matter).

A review is not just a compilation of sentences without criteria. It is much more than that.

A review must be done critically and the authors must have the knowledge to write about the subjects without any inaccuracies.

Organize the text by attributes and write the text for this purpose. The organization of the text is mandatory.

Make your contribution by explaining the different processes mentioned by the various authors. And explain them very well, to make it attractive and easy to read.

The authors don't know the difference between adsorption and absorption.

Etc.

Make the basic corrections to move on to the next level!

 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English quality should be improved.

Author Response

Comment 1: The authors have made some improvements to the text but have not considered the most important requests made by at least one of the reviewers.

Response 1: Thanks for your careful and responsible review. I am sorry. During the last several months, I have reread all relevant articles again and rewritten the whole article. I hope it is better now.

Comment 2: The text keeps repeating ideas and statements.

Response 2: I have rewritten the whole article again to delete all repeated sentences and to try to make the article more concise and clearer.

Comment 3: The text has problems with units, etc.

Response 3: I am sorry. I have checked the whole article to correct this issue.

 Comment 4: The authors don't use scientific words.

Response 4: I have checked the whole article to correct this issue and used a language editing service to improve the language expression.

Comment 5: The text does not use abbreviations for various written expressions that are continually repeated (e.g. particulate matter).

Response 5: I am sorry. I have checked the whole article and used abbreviations for relevant words.

Comment 6: A review is not just a compilation of sentences without criteria. It is much more than that.

Response 6: In the process of rewriting this review, I critically reread all articles, using objective and correct viewpoints from relevant articles as the standard (excluding a few articles or viewpoints with obvious limitations), integrating the research results conducted by scholars from different disciplinary backgrounds using different methods at different scales. This comprehensively reviewed relevant research from the perspective of the impact of green spaces on PM2.5, in order to better demonstrate the dual impact of green spaces on PM2.5. Based on the review, I revealed similarities and differences in the relevant research to obtain new findings and encouraged subsequent researchers to further explore under what circumstances green spaces have positive effects on PM2.5 concentration and under what circumstances they have negative effects.

Comment 7: A review must be done critically and the authors must have the knowledge to write about the subjects without any inaccuracies.

Response 7:  I have added a Discussion section (Section 7). This section reflects the fact that we did not blindly copy the viewpoints of other articles when writing this review but critically reviewed all articles and comprehensively integrated them to better reveal the positive and negative effects of green spaces on PM2.5 concentration in order to obtain some new perspectives that belong to us.

Before conducting the review, we did not know if there are completely different views on whether green spaces have a positive or negative impact on PM2.5 in studies of different scales. After conducting the review, we found that the large-scale research conducted by scholars with backgrounds in urban geography, landscape ecology, etc. found that urban green spaces as a whole are always beneficial for reducing PM2.5 pollution. A small number of studies have also found higher PM2.5 concentrations in some local areas, such as waterfront green areas, compared to the low greening control group.

Before reading this review, the vast majority of researchers may not be aware that in urban road areas, the difference is quite obvious, while in parks and campuses with high green coverage, these areas nearly do not produce any PM2.5, and greenery is always beneficial for reducing PM2.5 concentration.

We also attempted to reveal the significant differences and inhibitory effects of different tree species on PM2.5, which may be the main reason for the possible increase and decrease in PM2.5 caused by greening. You can see the Discussion section for more details.

After carefully reading the relevant articles, we objectively propose that green spaces have both positive and negative effects on PM2.5, which is valid and not caused by experimental defects or the research limitations of some researchers. The movement of PM2.5 from different sources in complex environments and the varying effects of different green space characteristics on PM2.5 have resulted in this complex phenomenon. We also believe that this article is meaningful, and we think that future researchers may further explore under what circumstances green spaces lead to an increase in PM2.5 and under what circumstances green spaces lead to a decrease in PM2.5. We think this is a very meaningful and relatively lacking research. Our review may provide them with a good start.

In the past few months, I have reread all the articles and carefully rewritten them to further ensure that I have sufficient understanding of the relevant knowledge and that the knowledge and viewpoints in the articles are completely accurate.

Comment 8: Organize the text by attributes and write the text for this purpose. The organization of the text is mandatory.

Response 8: During the process of rewriting this article, I have made every effort to reorganize the content of each section, including selecting important viewpoints and reorganizing my thoughts to bring them together. Additionally, I summarized the content based on these thoughts. In addition, I have made adjustments to the tables in all three sections based on the suggestion of another reviewer.

Comment 9: Make your contribution by explaining the different processes mentioned by the various authors. And explain them very well, to make it attractive and easy to read.

Response 9: I have tried my best to organize each paragraph with my own logic and added a Discussion section. During the process of rewriting the Conclusions section, I also put forward viewpoints based on the findings of others.

Comment 10: The authors don't know the difference between adsorption and absorption.

Response 10: In Section 6 (The regulatory effect of plants on PM2.5), I classified all the studies according to various mechanisms (deposition, blockage, adsorption, and absorption) and divided them into four tables. In the previous round of revisions, the third author Jiawei Li completed most of the modifications, and it is unclear whether her previous understanding was incorrect. As the first author of this article, I have been responsible for the revisions over the past few months. I believe that adsorption refers to the complex structure on the surface of plant leaves that promotes the attachment of PM2.5, while absorption refers to plants inhaling some very small particles through stomata. If there are any mistakes in my understanding, I hope you can point them out and give me another chance.