Three Complementary Sampling Approaches Provide Comprehensive Characterization of Pesticide Contamination in Urban Stormwater

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Editors and Authors,

I have carefully reviewed the manuscript of the article "Three complementary sampling approaches provide a comprehensive characterization of pesticide contamination in urban stormwater".

The research undoubtedly plays an important role in the scientific community.

The article provides valuable suggestions for improving the pesticide monitoring system in urban water bodies.

However, to improve the article's quality and attract a wider audience, it would be good to consider the following comments.

The map in Figure 1 only shows the locations of ponds within the city of Brampton, Canada, without the general context of the location of this city within Canada. Correcting this would help readers better navigate the geographical location of the study site.

Table 2 has a different style of presentation, which makes it difficult to read the tables consistently.

Author Response

Comment 1: Dear Editors and Authors, I have carefully reviewed the manuscript of the article "Three complementary sampling approaches provide a comprehensive characterization of pesticide contamination in urban stormwater". The research undoubtedly plays an important role in the scientific community. The article provides valuable suggestions for improving the pesticide monitoring system in urban water bodies. However, to improve the article's quality and attract a wider audience, it would be good to consider the following comments. 

Response: Thank you very much for your positive feedback and helpful suggestions. We have made your recommended changes, described below, to the tables and map in the manuscript. 

Comment 2: The map in Figure 1 only shows the locations of ponds within the city of Brampton, Canada, without the general context of the location of this city within Canada. Correcting this would help readers better navigate the geographical location of the study site. 

Response: Thank you for your suggestion to improve this figure. We have updated the map to include a reference to the location of Brampton within Canada. 

Comment 3: Table 2 has a different style of presentation, which makes it difficult to read the tables consistently. 

Response: Thank you for bringing this to our attention – we have changed the formatting of this table to match more closely the style of the other tables. 

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript is well written and easy to follow.  I have a couple of suggestions to improve it. 

1. The supplementary material should have some more information on the construction of the biofilm sample rack since these are not commercially available. In particular dimensions and manufacturing methods should be included for the custom-built holders.

2. TWA is first used on page 3 but not defined until page 8.

3. Page 9 line 308 - we created plots.  Which plots?  Are these the ones in the supplementary material or Figure 4.  Please label.

4. Table 2 - need more information in the legend about the non-diagonal entries.  I believe those should be pesticide detections shared between the two indicated sampling methods.  Also it would make the statement made of page 14 lines 476-477 (refers to Table 4) much clearer if the number of pesticides for each sampling method could be somehow made clearer of the 5 shared between all 3 methods. For example 1 for water, 0 for biofilm, and 4 for o-DGT in Table 2. (Since Table 4 covers 2.5 pages - harder to glean this information)

5. Table 3 is the percentage detection frequency.  The legend should include the fraction was times by 100.

6. Page 12 line 344 references Table 3 - this information is first shown in Table 2.

7. The discussion about Table 4 should include the total number of pesticides detected for each method as well. (water quantified 10, detected 14; biofilm quantified 4, detected 6; o-GDT quantified 76, detected 79)

8. Any speculation as to why atrazine, difenoconazole, and metolachlor have similar maximum TWA in o-DGT and water sampling?

9. Figure 4 - I can not see the blue color - it looks black. Also the grey dots are hard to see.  

10. The numbers for the references are listed twice.  1. [1]

Author Response

This manuscript is well written and easy to follow.  I have a couple of suggestions to improve it.  

Thank you very much for your positive feedback and constructive comments. We have made changes to the manuscript according to your comments below.

Comment 1: The supplementary material should have some more information on the construction of the biofilm sample rack since these are not commercially available. In particular dimensions and manufacturing methods should be included for the custom-built holders.

Response: Thank you for your interest in our biofilm samplers! We have inserted a detailed description of how we constructed both the biofilm samplers and the holders for the o-DGTs to the Supplementary Materials.  

Comment 2: TWA is first used on page 3 but not defined until page 8.

Response: We have defined the time-weighted average (TWA) on L 117 – L 118. 

Comment 3: Page 9 line 308 - we created plots.  Which plots?  Are these the ones in the supplementary material or Figure 4.  Please label.

Response: Thank you for bringing this to our attention. We have clarified that we are referring to Figure 4 (L 314).

Comment 4: Table 2 - need more information in the legend about the non-diagonal entries.  I believe those should be pesticide detections shared between the two indicated sampling methods.  Also it would make the statement made of page 14 lines 476-477 (refers to Table 4) much clearer if the number of pesticides for each sampling method could be somehow made clearer of the 5 shared between all 3 methods. For example 1 for water, 0 for biofilm, and 4 for o-DGT in Table 2. (Since Table 4 covers 2.5 pages - harder to glean this information)

Response: Thank you for your suggestions to improve this table. We revised the table caption to better explain what data this table summarizes and have removed the redundant half of the triangle to better cue the reader to the nature of the pairwise comparisons being made (L 324 – L 328).

Comment 5: Table 3 is the percentage detection frequency.  The legend should include the fraction was times by 100.

Response: We have made this correction (L 345).  

Comment 6: Page 12 line 344 references Table 3 - this information is first shown in Table 2.

Response: We have made this correction (L 353).

Comment 7: The discussion about Table 4 should include the total number of pesticides detected for each method as well. (water quantified 10, detected 14; biofilm quantified 4, detected 6; o-GDT quantified 76, detected 79)

Response: This is an excellent point – we have added this information to L 485 and L 486.

Comment 8: Any speculation as to why atrazine, difenoconazole, and metolachlor have similar maximum TWA in o-DGT and water sampling?

Response: Thank you for pointing out the potential for misunderstanding in our writing. We believe you are referring to L 525 – L 537 where we compare the maximum TWA in o-DGT to the method detection limits in water samples for these pesticides. Table 3 shows that these pesticides were not detected in the water samples - we have added reference to this on  L 527 to help clarify this. In this section, we are testing our prediction that if a compound is only detected in o-DGT samplers, its TWA concentration should be lower than the MDL for water samples. For those 3 pesticides, the maximum TWA concentrations in o-DGTs (Table 4) and MDLs for water samples were within the same order of magnitude.

Comment 9: Figure 4 - I can not see the blue color - it looks black. Also the grey dots are hard to see.  

Response: We apologize for this and have made changes to improve this figure. We have changed the colour of the grey dots so they are more contrasted against the background. We have also clarified the caption’s reference to the dashed lines as the blue colour is not an important distinction - the difference between the dashed and solid lines are what matters in this figure. Thank you for bringing these issues to our attention.

Comment 10: The numbers for the references are listed twice.  1. [1]

Response: Thank you for bringing this to our attention. We have corrected this error. 

Reviewer 3 Report

Comments and Suggestions for Authors

1. The Introduction section mentions that "Urban pollution is intensified by the consequences of this rapid development and land clearing, which results in widespread coverage with impervious surfaces." Why does the intensification of urban pollution lead to extensive coverage with impervious surfaces? Here, relevant references should be cited or an explanation provided to facilitate readers' understanding of this phenomenon.

2. The last sentence of the second paragraph in the Introduction states that monitoring related indicators is important. It can be briefly supplemented with the main parts that the following content of this article will focus on, as well as the main research ideas and contents, to make the article structure clearer.

3. In Part 1.2 when elaborating on the hypotheses of this article, the proposed hypotheses can be numbered and listed for greater clarity.

4. In Part 2.2, it is mentioned that the research area of this study is 21 stormwater management ponds in Brampton, Ontario, Canada. Further explanations can be provided on the reasons for selecting this research area, such as its uniqueness and necessity, to demonstrate the value of this area for this study.

5. It should be checked whether Line 514 is missing a chapter number. If so, it should be supplemented.

 

6. In the abstract section, a brief supplement on the research significance of this study can be added at the end to help readers quickly grasp the research content of the article.

Author Response

Comment 1: The Introduction section mentions that "Urban pollution is intensified by the consequences of this rapid development and land clearing, which results in widespread coverage with impervious surfaces." Why does the intensification of urban pollution lead to extensive coverage with impervious surfaces? Here, relevant references should be cited or an explanation provided to facilitate readers' understanding of this phenomenon.

Response: Apologies, we see how this sentence can be confusing. We have reworded to clarify that it is the rapid development, not urban pollution, that leads to coverage with impervious surfaces (L 34 – L 36). We have also provided a relevant reference to support this point (L 36).  

Comment 2: The last sentence of the second paragraph in the Introduction states that monitoring related indicators is important. It can be briefly supplemented with the main parts that the following content of this article will focus on, as well as the main research ideas and contents, to make the article structure clearer.

Response: Thank you for this helpful suggestion, we agree it is needed. We have added a brief description of the content that will follow this section to clarify the article structure (L 56 – L 61).  

Comment 3: In Part 1.2 when elaborating on the hypotheses of this article, the proposed hypotheses can be numbered and listed for greater clarity.

Response: We have added numbers to the hypotheses as suggested (L 145 and L 150).   

Comment 4: In Part 2.2, it is mentioned that the research area of this study is 21 stormwater management ponds in Brampton, Ontario, Canada. Further explanations can be provided on the reasons for selecting this research area, such as its uniqueness and necessity, to demonstrate the value of this area for this study.

Response: Thank you for pointing out the need for more information about the location of our study. We have added further descriptions about the city and why it makes an ideal location for studying urban pesticide contamination in stormwater (L 174  - L 178).  

Comment 5: It should be checked whether Line 514 is missing a chapter number. If so, it should be supplemented.

Response: Thank you for your attention to detail! We believe you are referring to the Morin et al. (2013) paper. For this article, there is no chapter number, just the pages of the article (pp. 61-73) and volume (109) in the journal.  

Comment 6: In the abstract section, a brief supplement on the research significance of this study can be added at the end to help readers quickly grasp the research content of the article.

Response: Thank you for your feedback on the abstract. We have revised the entire abstract and have added a concluding statement about the significance of this study to address your suggestion (L 26 – L 28).  

Reviewer 4 Report

Comments and Suggestions for Authors

Based on the submission review, I am with regret to suggest against publication of the preform. But authors are encouraged to resubmit after significant improvement.

Firstly, the topic does not quite fit with Urban Science aim and scope. As the references indicate, it seems like close linked to environment engineering sectors. 

So the authors need to reconsider the academic value of this research, with emphasis on the journal reader interests.  

Then the scientific questions are clear, since the main work concentrates on water sampling approach for pesticide pollution investigation in local case study.

Restructure the whole content in IMRDC style. There are no specific results, especially conclusion part in this paper.

Furthermore, please read the author guidelines carefully and prepare the manuscript strictly following the instructions. Several formats errors (e.g., equation and reference numbers).

Author Response

Comment 1: Based on the submission review, I am with regret to suggest against publication of the preform. But authors are encouraged to resubmit after significant improvement. Firstly, the topic does not quite fit with Urban Science aim and scope. As the references indicate, it seems like close linked to environment engineering sectors. So the authors need to reconsider the academic value of this research, with emphasis on the journal reader interests.   

Response: We thank you for your feedback and we hear your concerns about the manuscript’s scope. To give some context about our submission, last Fall we received a direct invitation from an editor with Urban Science to submit an article to a special issue. We shared an abstract of our manuscript with this editor, who encouraged our submission.  

We believe our manuscript does fit within the aims and scope of Urban Science. The aim of Urban Science is to “publish research relating to urban development, planning, expansion, living conditions and well-being, and sustainability.” The contamination of stormwater is related to each of these fields: for example, development directly impacts the creation of stormwater infrastructure and its contaminant burden; contaminated stormwater affects the living conditions and well-being of both residents and wildlife in cities; and identifying and monitoring contamination in urban waters is essential to the sustainability of urban water systems and urban biodiversity. We believe our research also fits within the scopes of Urban Science, most notably within the scope of the “Urban Environment” and “Pollution in Urban Areas”.  

We acknowledge your concerns about the level of interest of our manuscript within the readership of Urban Science. We have collected some examples of similar articles, focused on stormwater management and contamination, which we hope will improve confidence in the compatibility of our research with this journal. Some examples of articles with stormwater contamination themes include: 

“Stormwater Management: An Integrated Approach to Support Healthy, Livable, and Ecological Cities” By Grigg 2024. https://doi.org/10.3390/urbansci8030089  

”Community Perceptions and Knowledge of Modern Stormwater Treatment Assets” By Zamanifard et al., 2021. https://doi.org/10.3390/urbansci5010005  

“Pipe Dreams: Urban Wastewater Treatment for Biodiversity Protection” By Cunningham & Gharipour, 2018 https://doi.org/10.3390/urbansci2010010 

“A Case Study Evaluating Water Quality and Reach-, Buffer-, and Watershed-Scale Explanatory Variables of an Urban Coastal Watershed” By Heidkamp & Christian, 2022. https://doi.org/10.3390/urbansci6010017   

We do think our manuscript is relevant to the aims and scopes of Urban Science, but we take to heart your concerns that this relevance was not clear enough. To address this issue, we have made a number of changes to the manuscript. We have revised the abstract and have highlighted the direct links between our work and the journal’s scopes (L 13 – L 28). Further, we have added a new conclusion section that emphasizes the results of our study and how it relates to the scopes of the journal, particularly “Pollution in Urban Areas” and the “Urban Environment” (L 688 – L 695). We hope these changes address your concerns. 

Comment 2: Then the scientific questions are clear, since the main work concentrates on water sampling approach for pesticide pollution investigation in local case study. 

Response: Thank you for your positive feedback. 

Comment 3: Restructure the whole content in IMRDC style. There are no specific results, especially conclusion part in this paper. 

Response: We have added a conclusion section (L 688 – L 695) to the manuscript. The manuscript now has every section required by the journal according to their guidelines for authors, which states that the results section may be combined with the discussion sections for research manuscripts (please refer to: https://www.mdpi.com/journal/urbansci/instructions#preparation).  

Comment 4: Furthermore, please read the author guidelines carefully and prepare the manuscript strictly following the instructions. Several formats errors (e.g., equation and reference numbers). 

Response: Thank you for your feedback. We have closely adhered to the author guidelines and formatting requirements, as advised by the Editor. We have corrected errors in the sections with equations and the numbering in the reference section. 

Round 2

Reviewer 4 Report

Comments and Suggestions for Authors

Authors responded rationally.