Heavy Metals in Leafy Vegetables and Soft Fruits from Allotment Gardens in the Warsaw Agglomeration: Health Risk Assessment

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript addresses a highly relevant topic concerning the contamination of urban-grown vegetables and fruits with heavy metals (HMs) and the associated health risks. The study is well-structured and provides comprehensive data on HM concentrations in various crops from Warsaw allotment gardens, including health risk assessments using recognized indices (HQ, HI, CR). The work contributes valuable insights into urban agriculture safety and public health implications.

In the abstract, include a brief mention of the risk assessment results (e.g., which crops pose the highest risk and recommendations), improving reader takeaway.

In Introduction Add recent global urban agriculture studies to position the study in a broader international context.

Clarify the research gap more explicitly — i.e., why is this study needed in Warsaw specifically? Are there few existing data on urban allotment gardens there?

Improve flow by consolidating overlapping points about sources of HMs and risks into fewer, clearer paragraphs.

Clarify the sampling strategy — e.g., how were the 16 allotment gardens selected? How were the specific sampling points within each garden determined?

Provide justification for the chosen drying temperatures and durations relative to HM stability.

Include more detail on quality assurance/quality control (QA/QC) measures, such as: 1) Use of certified reference materials 2) Method detection limits 3) Replicate analysis precision.

Clarify the basis for assumed daily consumption (K) values in the risk assessment equations — is this from local dietary surveys or literature?

Include spatial distribution maps of HM concentrations to visualize contamination gradients in allotment gardens.

Highlighting which values exceed permissible limits directly in the tables (e.g., color-coding or bolding).

Discuss the variability of HM concentrations more deeply — what factors might explain the broad ranges? Soil properties, proximity to traffic, garden management?

Strengthen the discussion by comparing results more thoroughly with other international urban agriculture studies to contextualize Warsaw’s situation.

Discuss the implications of findings for urban gardening practices, e.g., what agricultural techniques can reduce HM uptake?

Address the potential limitations of the study

Recommend specific remediation or management actions based on results.

Provide a clearer explanation of the health risk indices (HQ, HI, CR) in layman’s terms for wider accessibility.

For tomatoes, which showed high Pb HQ values, discuss potential reasons and practical recommendations.

Consider including children's health risk assessment, as they are more vulnerable to HM toxicity.

Strengthen the conclusion by emphasizing actionable recommendations

Highlight the novelty of the study’s findings in Warsaw and potential applicability to other urban areas.

 

Author Response

Please find enclosed our revised manuscript entitled “Heavy Metals in Leafy Vegetables and Soft Fruits from Allotment Gardens in the Warsaw Agglomeration: Health Risk Assessment” (ID: Sustainability-3674006) for recommendation to published on Sustainability.

Reviewer #1:

Thanks a lot for the comments. We have modified they as requested.

Specific Comments:

In the abstract, include a brief mention of the risk assessment results (e.g., which crops pose the highest risk and recommendations), improving reader takeaway.

Response: Information about the health risk assessment has been added to the abstract. Lines 33–37.

In Introduction Add recent global urban agriculture studies to position the study in a broader international context.

Response: The issue has been discussed in an international context. Lines 105-115

Clarify the research gap more explicitly — i.e., why is this study needed in Warsaw specifically? Are there few existing data on urban allotment gardens there?

Response: The rationale for conducting this research in Warsaw has been clarified. Lines 105-115; 121-129; 153-163

Improve flow by consolidating overlapping points about sources of HMs and risks into fewer, clearer paragraphs.

Response: HM and risk sources were consolidated. Lines 52-85

Clarify the sampling strategy — e.g., how were the 16 allotment gardens selected? How were the specific sampling points within each garden determined?

Response: Samples were collected from plots where no micronutrient fertilisation or composts of unknown origin were used. Information on how samples were taken for the study has been added. Lines 250-253

Provide justification for the chosen drying temperatures and durations relative to HM stability.

Response: Drying at 105 °C enabled the acquisition of dry matter without loss of heavy metals during the drying process. Lines 278-280

Include more detail on quality assurance/quality control (QA/QC) measures, such as: 1) Use of certified reference materials 2) Method detection limits 3) Replicate analysis precision.

Response to 1: Added: Certified reference materials — Montana soil and tobacco — were used for quality control. Lines 293-294

Response to 2: Added: Method detection limits: (Line 295)

Metal	LOD	Units
Pb	0.01–0.1	µg L-1 lub µg kg-1 DM
Cd	0.001–0.01	µg L-1 lub µg kg-1 DM
Zn	0.05–0.5	µg L-1 lub µg kg-1 DM
Cu	0.01–0.1	µg L-1 lub µg kg-1 DM

Response to 3: The precision of the repeatability of the results is determined by the standard deviation that is in the tables with the results. Precision in the context of repeatability refers to the degree to which repeated measurements of the same sample using the same method produce similar results. The standard deviation is a measure of this variability. A low standard deviation means that the measurements are centered around the average value, and so are more precise. A high standard deviation indicates a greater dispersion of results, which means less precision.

Clarify the basis for assumed daily consumption (K) values in the risk assessment equations — is this from local dietary surveys or literature?

Response: These data were obtained from the Statistical Yearbook of the Republic of Poland. Warszawa 2023. Lines 303

Include spatial distribution maps of HM concentrations to visualize contamination gradients in allotment gardens. Highlighting which values exceed permissible limits directly in the tables (e.g., color-coding or bolding).

Response: In the tables 1-2, values exceeding the permissible limits are highlighted in red. The additional generation of spatial distribution maps of HM concentrations would not add value to the study nor influence the conclusions.

Discuss the variability of HM concentrations more deeply — what factors might explain the broad ranges? Soil properties, proximity to traffic, garden management?

Response: The influence of various factors on the variability of HM concentrations in plants has been discussed in more detail. Lines 343–345.

 

Strengthen the discussion by comparing results more thoroughly with other international urban agriculture studies to contextualize Warsaw’s situation.

Response: The results have been compared with data from researchers in different parts of the world. Lines: 343-347; 356; 375-376; 379-384; 388; 399-401; 411-412; 435-437; 470-476; 483-484; 603–611

Discuss the implications of findings for urban gardening practices, e.g., what agricultural techniques can reduce HM uptake?

Response: Recommendations for reducing HMs in soil and plants have been added in the Introduction. Lines 121–129

Address the potential limitations of the study

Response: Potential study limitations have been discussed. Lines 151–161.

Recommend specific remediation or management actions based on results.

Response: Remedial action recommendations based on the findings have been added to the Conclusions. Lines 678–682.

Provide a clearer explanation of the health risk indices (HQ, HI, CR) in layman’s terms for wider accessibility.

Response: The meanings of the indicators have been explained using plain language. Lines 553–557; 585-589; 603-606.

For tomatoes, which showed high Pb HQ values, discuss potential reasons and practical recommendations.

Response: The causes and related risks have been discussed for tomatoes. Lines 603–611

Consider including children's health risk assessment, as they are more vulnerable to HM toxicity.

Response: A health risk assessment for children has been included. Lines 68-71; 603-611

Strengthen the conclusion by emphasizing actionable recommendations

Response: Recommendations to reduce HM contamination in crops grown in AGs have been added. Lines 678–682

Highlight the novelty of the study’s findings in Warsaw and potential applicability to other urban areas.

Response: The novelty of the Warsaw-based study and its potential applicability to other cities have been discussed in the Conclusions. Lines 687–696.

More recent literature has been added (red color) and some older references removed. There has been a reorganization of references.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please find the comments enclosed. 

Comments for author File: Comments.pdf

Author Response

Please find enclosed our revised manuscript entitled “Heavy Metals in Leafy Vegetables and Soft Fruits from Allotment Gardens in the Warsaw Agglomeration: Health Risk Assessment” (ID: Sustainability-3674006) for recommendation to published on Sustainability.

Reviewer #2:

Thanks a lot for the comments. We have modified they as requested.

Specific Comments:

1. The Health Risk section, starting from line 93, should be integrated into the Introduction and should not remain as a separate paragraph. The Reviewer considers the Introduction to be well-written and believes there is no need for extensive explanations on the health effects of each metal, especially those not investigated in this study. A much shorter version of this information should be seamlessly incorporated into the Introduction.

Response to 1: The Introduction has been consolidated.

2. The map (Figure 1) should indicate the sampling locations of both the AGs and the control sites.

Response to 2: Mapping the sampling locations would not add any value to the article nor influence the conclusions.

3. The maximum permissible limits for HMs established by the European Union should be added to Table 1, "Content of heavy metals (mg kg-1 dry matter (DM)) in leafy vegetables from AGs of Warsaw."

Response to 3: Permissible HM limits have been added to Tables 1 and 2.

4. "Traces" as values in tables should be replaced by the LOD (Limit of Detection) of the analytical method used.

Response to 4: ‘LOD’ has been added to Tables 1 and 2 instead of ‘traces’.

5. A comparative table presenting data from other studies investigating HMs in plants and vegetables should be created and discussed in the text. Including comparative studies from outside of Europe would be of great importance for a wider audience.

Response to 5: Literature sources containing HM concentration data in vegetables grown outside of Europe were used. Based on these, the studies were added and discussed as recommended by the reviewer. Lines 105–115.

More recent literature has been added (red color) and some older references removed. There has been a reorganization of references.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

your topic is interesting. I agree that safety of foods is extremely necessary to be permanently tested. I have some recommendations/notes:

Introduction

- in my opinion, introduction is too long. On the contrary, legislative focused on HM in Poland, or EU should be shortly presented.

- hypothesis/aim of paper should be rewritten – hypotheses are divided to two parts: lines 84-92 and lines 155-162. It should be just in the end of article and concisely and well-arranged.

Methods

- lines (L) 176-178: if another locality was used as control, it (soil type, pH etc. – like soil was described for AGs) should be shortly described. This meaning sounds very general.

- L183-196: where were analyses done? Certified laboratory of control institute? or university laboratory? please, specify

Results and discussion

- tables 1 and 2: I would prefer to add limit for HM directly to the table – it is simple to reading and comparison

- I am not sure about your some presentation of results and it seems to be confusing for me, e.g.:

1. a) L 239-241: The calculated mean concentrations (Tables 1 and 2) indicate that the levels of heavy metals (HMs) in both the analyzed vegetables and fruits did not exceed the maximum permissible limits established by the European Union for zinc (Zn; 200 mg kg⁻¹ )
2. b) Zn content in the studied beet greens and lettuce cultivated in Warsaw’s AGs exceeded the maximum permissible limit established by the FAO/WHO, which is 450 mg kg¹ DM

= these meanings are confusing for me: it lower limit was not exceeded, how higher limit can be exceeded? Please check your meanings or rewrite it more understandable.

 

After major revision, it can be published.

Author Response

Please find enclosed our revised manuscript entitled “Heavy Metals in Leafy Vegetables and Soft Fruits from Allotment Gardens in the Warsaw Agglomeration: Health Risk Assessment” (ID: Sustainability-3674006) for recommendation to published on Sustainability.

Reviewer #3:

Thanks a lot for the comments. We have modified they as requested.

Specific Comments:

Introduction

- in my opinion, introduction is too long. On the contrary, legislative focused on HM in Poland, or EU should be shortly presented.

Response: The introduction has been consolidated.

- hypothesis/aim of paper should be rewritten – hypotheses are divided to two parts: lines 84-92 and lines 155-162. It should be just in the end of article and concisely and well-arranged.

Response: The hypotheses and research aim have been combined into one section with no division. Lines 153–175.

Methods

- lines (L) 176-178: if another locality was used as control, it (soil type, pH etc. – like soil was described for AGs) should be shortly described. This meaning sounds very general.

Response: Added information about the control location: The control allotment garden was located on podzolic soils, classified within the granulometric group of light and loamy sands; in the upper part of the profile, dusty soils were present with a pH in KCl ranging from 6.8 to 7.0 and a humus content of 3.6%. Lines 265–268.

- L183-196: where were analyses done? Certified laboratory of control institute? or university laboratory? please, specify

Response: Added: The analyses were conducted in an accredited laboratory of the Institute of Environmental Protection – National Research Institute in Warsaw. Lines 291–292.

Results and discussion

- tables 1 and 2: I would prefer to add limit for HM directly to the table – it is simple to reading and comparison

Response: Permissible HM limits have been added to the Tables 1 and 2.

- I am not sure about your some presentation of results and it seems to be confusing for me, e.g.:

1. a) L 239-241: The calculated mean concentrations (Tables 1 and 2) indicate that the levels of heavy metals (HMs) in both the analyzed vegetables and fruits did not exceed the maximum permissible limits established by the European Union for zinc (Zn; 200 mg kg⁻¹ )
2. b) Zn content in the studied beet greens and lettuce cultivated in Warsaw’s AGs exceeded the maximum permissible limit established by the FAO/WHO, which is 450 mg kg¹ DM

Response: According to the table in Mawari et al. 2022 (https://doi.org/10.1177/11786302221119151), the EU permissible Zn limit is 200 mg kg⁻¹ DM. This has been referenced in the text (Line 375-376 - [4]).

Response: Lines 411–412 refer to the FAO/WHO permissible Zn limit, which is 50 mg kg⁻¹ DM according to Sultana et al. 2022 (https://doi.org/10.1186/s40068-022-00261-9). The previously cited value of 450 mg kg⁻¹ DM was incorrect. It should be 50 mg kg⁻¹ DM.

More recent literature has been added (red color) and some older references removed. There has been a reorganization of references.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

1. The description of heavy metal pollution sources and their impact on the human body is repeated in different sections of the manuscript. Therefore, it is recommended that the authors review the text and remove repetitions. So, it is better to move the text (lines 228-238) to the Introduction.
2. For clarity, it is better to remove the maximum permissible limits from the text and present them as a separate table or insert them into Table 1.
3. Provide information on the hazard quotient (HQ) and the hazard index (HI) in the “HEALTH RISKS” section, and move the calculation formulas for these parameters to the end of the “Materials and Methods” section.
4. Expand the abbreviation IP in the text (line 74).
5. What conditions were used for the vegetable and fruit solutions storage after mineralization between analyses or were new solutions prepared each time?
6. Why were “laboratory tests performed only in duplicate” (line 195)? Usually at least three tests are done.
7. What portion of ash (or the entire mass of ash obtained) was dissolved and in what volume of hydrochloric acid (Line 192)?
8. Lines 430-434 duplicate lines 426-430.
9. Why did the zinc content in beet tops, lettuce and sorrel exceed the permissible values ​​(lines 328-331), but not in other vegetables? What is the reason for this?
10. Lines 395-396. "The highest exceedances of the permissible concentrations were recorded for lead (Pb) and cadmium (Cd), which were 80 and 9 times higher than the permissible limits, respectively". Despite this, the authors suggest eating vegetables grown in AGs located in urban areas. To do this, they advise the outer leaves and thoroughly washing the lettuce. Since this recommendation is not supported by the results of chemical analysis, it is proposed to remove these recommendations.
11. The value 1.54 × 10⁻⁵ of the cancer risk falls within the acceptable range of 1 × 10⁻⁴ and 1 × 10⁻⁶ (lines 488, 477), but the conclusion is made "the cancer risk for Pb is considered tolerable". Please, explain.

Author Response

Please find enclosed our revised manuscript entitled “Heavy Metals in Leafy Vegetables and Soft Fruits from Allotment Gardens in the Warsaw Agglomeration: Health Risk Assessment” (ID: Sustainability-3674006) for recommendation to published on Sustainability.

Reviewer #4:

Thanks a lot for the comments. We have modified they as requested.

Specific Comments:

1. The description of heavy metal pollution sources and their impact on the human body is repeated in different sections of the manuscript. Therefore, it is recommended that the authors review the text and remove repetitions. So, it is better to move the text (lines 228-238) to the Introduction.

Response to 1: Repetitions were removed and lines (365–372) were moved to the Introduction.

2. For clarity, it is better to remove the maximum permissible limits from the text and present them as a separate table or insert them into Table 1.

Response to 2: Permissible HM limits were added to Tables 1 and 2.

3. Provide information on the hazard quotient (HQ) and the hazard index (HI) in the “HEALTH RISKS” section, and move the calculation formulas for these parameters to the end of the “Materials and Methods” section.

Response to 3: The "Health Risk" section includes information on the hazard quotient (HQ) and hazard index (HI), and the calculation formulas for these parameters have been moved to the end of the "Materials and Methods" section. Lines: 553-557; 585-589; 603-611; 639-641; 651-656; 296-326

4. Expand the abbreviation IP in the text (line 74).

Response to 4: It should be AGs (allotment gardens), Line 142.

5. What conditions were used for the vegetable and fruit solutions storage after mineralization between analyses or were new solutions prepared each time?

Response to 5: Added information about the storing conditions: Heavy metals (HMs) were determined the day after mineralization. The mineralized solutions were stored at room temperature. Lines 287-288

6. Why were “laboratory tests performed only in duplicate” (line 195)? Usually at least three tests are done.

Response to 6: Since the methodological error did not exceed 5.6%, it was decided to perform two replicates.

7. What portion of ash (or the entire mass of ash obtained) was dissolved and in what volume of hydrochloric acid (Line 192)?

Response to 7: Added information: The entire ash mass was dissolved in 50 mL of hydrochloric acid. Lines 286-287

8. Lines 430-434 duplicate lines 426-430.

Response to 8: Duplicate lines (579–583) were removed.

9. Why did the zinc content in beet tops, lettuce and sorrel exceed the permissible values ​​(lines 328-331), but not in other vegetables? What is the reason for this?

Response to 9: The cause of increased Zn levels in leafy vegetables has been explained. Lines 470–477.

10. Lines 395-396. "The highest exceedances of the permissible concentrations were recorded for lead (Pb) and cadmium (Cd), which were 80 and 9 times higher than the permissible limits, respectively". Despite this, the authors suggest eating vegetables grown in AGs located in urban areas. To do this, they advise the outer leaves and thoroughly washing the lettuce. Since this recommendation is not supported by the results of chemical analysis, it is proposed to remove these recommendations.

Response to 10: The recommendation was removed, and it was added that lettuce grown in AGs is not recommended for consumption. Lines 541–546

11. The value 1.54 × 10⁻⁵ of the cancer risk falls within the acceptable range of 1 × 10⁻⁴ and 1 × 10⁻⁶ (lines 488, 477), but the conclusion is made "the cancer risk for Pb is considered tolerable". Please, explain.

Response to 11: The cancer risk value related to Pb accumulation in plants has been clarified and corrected. Lines 639–641

More recent literature has been added (red color) and some older references removed. There has been a reorganization of references.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

The study of heavy metal accumulation in plants is important and relevant. Unlike many organic pollutants, heavy metals do not degrade and are stable in the environment. The authors of the article determined the content of metals in plant tissues and organs, which is undoubtedly interesting and important from both practical and theoretical points of view. During the process of studying the article, a number of questions and comments arose.

 

1. It is worth supplementing the introduction with information on how to control household plots at some level of innovation in the economy and for consumers. How significant is the study in figures? Perhaps, it is possible to determine what percentage of production falls to the share of the population. Since the publication is published in an international edition, the data indicators will be of great importance for readers from other countries who are not familiar with such indicators in Warsaw.

 

2. In the health risks section, threshold values ​​should be added.

Permissible values ​​of metals and values ​​at which the described symptoms are possible allow a more adequate assessment of the results obtained and emphasize the relevance of the study. For example, in line 121 the authors write: "Excessive doses of Zn cause severe neurological symptoms, oxidative stress, and reduce the integrity of the intestinal wall...", adding a threshold value helped the reader to evaluate the seriousness of the statements in numerical terms by comparing the results obtained.

 

3. In the last paragraph of the introduction, it is worth adding a few words about where these elements accumulate in plants, perhaps showing the percentage of accumulation in somatic tissues and generative, or consumed and not consumed by humans.

 

4. Separately, I would like to highlight and compare the authors clearly and in detail the section "Materials and Methods". However, the visual material is significantly limited in this section. Perhaps the sampling scheme or cards with collection sites significantly limits the publication and enhances understanding of the requirements.

 

5. Is it possible to place the results section and discussion in this journal?

 

6. In Tables 1 and 2, it is necessary to add the acceptable values ​​​​of the studied components for inclusion of plants and their parts.

 

7. As a result of reading the article, the question inevitably arises: what is the novelty of these studies, in relation to those already conducted? Or is it repeated, or does it summarize the data of the others? The question arises, since the authors indicate this in the text, for example, in lines 227 to 237, referring to sources [50, 51, 52, 53, 54, 55], because the fact of the effect of TM on a person is a known fact, as is the fact that they can significantly accumulate in the parts of the population consumed by people, and that this indicator varies from culture to culture. Perhaps it is worth adding a few phrases about the latest research in the field of health?

 

8. What do the authors associate with the high values ​​of cadmium, and not other metals, described in the paragraph from lines 239 to 248?

 

9. Perhaps the work deals with the issue of soil phytoremediation, as a proposal for partial identification of these problems?

 

10. Of the 86 sources, only 26 have been published in the last 5 years.

Comments for author File: Comments.pdf

Author Response

Please find enclosed our revised manuscript entitled “Heavy Metals in Leafy Vegetables and Soft Fruits from Allotment Gardens in the Warsaw Agglomeration: Health Risk Assessment” (ID: Sustainability-3674006) for recommendation to published on Sustainability.

Reviewer #5:

Thanks a lot for the comments. We have modified they as requested.

Specific Comments:

1. It is worth supplementing the introduction with information on how to control household plots at some level of innovation in the economy and for consumers. How significant is the study in figures? Perhaps, it is possible to determine what percentage of production falls to the share of the population. Since the publication is published in an international edition, the data indicators will be of great importance for readers from other countries who are not familiar with such indicators in Warsaw.

Response to 1: Information has been added regarding how AGs should be monitored. Percent data on urban vegetable production depending on city size were included. In addition, the importance of HM contamination control in fruits and vegetables was added to the Conclusions. Lines 105-115; 121-129; 687-696

2. In the health risks section, threshold values ​​should be added. Permissible values ​​of metals and values ​​at which the described symptoms are possible allow a more adequate assessment of the results obtained and emphasize the relevance of the study. For example, in line 121 the authors write: "Excessive doses of Zn cause severe neurological symptoms, oxidative stress, and reduce the integrity of the intestinal wall...", adding a threshold value helped the reader to evaluate the seriousness of the statements in numerical terms by comparing the results obtained.

Response to 2: The Threshold value was added. Line 72. 

3. In the last paragraph of the introduction, it is worth adding a few words about where these elements accumulate in plants, perhaps showing the percentage of accumulation in somatic tissues and generative, or consumed and not consumed by humans.

Response to 3: Added to the Introduction, Lines 89–92.

4. Separately, I would like to highlight and compare the authors clearly and in detail the section "Materials and Methods". However, the visual material is significantly limited in this section. Perhaps the sampling scheme or cards with collection sites significantly limits the publication and enhances understanding of the requirements.

Response to 4: Mapping the sampling locations would not add any value to the article nor influence the conclusions

5. Is it possible to place the results section and discussion in this journal?

Response to 5: The editorial board of Sustainability did not raise any objections to the combined format of the Results and Discussion section.

6. In Tables 1 and 2, it is necessary to add the acceptable values ​​​​of the studied components for inclusion of plants and their parts.

Response to 6: Permissible HM limits were added to Tables 1 and 2.

7. As a result of reading the article, the question inevitably arises: what is the novelty of these studies, in relation to those already conducted? Or is it repeated, or does it summarize the data of the others? The question arises, since the authors indicate this in the text, for example, in lines 227 to 237, referring to sources [50, 51, 52, 53, 54, 55], because the fact of the effect of TM on a person is a known fact, as is the fact that they can significantly accumulate in the parts of the population consumed by people, and that this indicator varies from culture to culture. Perhaps it is worth adding a few phrases about the latest research in the field of health?

Response to 7: Information on novelty and current challenges of such studies has been added (Introduction and Conclusions). Lines 59-89; 153–163; 687-696. Lines 227–237 were corrected as suggested. Line 365.

8. What do the authors associate with the high values ​​of cadmium, and not other metals, described in the paragraph from lines 239 to 248?

Response to 8: The mechanism of Cd accumulation in leafy vegetables has been described. Lines 379–384.

9. Perhaps the work deals with the issue of soil phytoremediation, as a proposal for partial identification of these problems?

Response to 9: Information on phytoremediation of soils has been added as a possible solution to HM accumulation in AG crops in Warsaw. Lines 121–129

10. Of the 86 sources, only 26 have been published in the last 5 years.

Response to 10: More recent literature has been added (red color) and some older references removed. There has been a reorganization of references.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

After reviewing the revised version of the manuscript, I am pleased to inform you that the quality of the work has significantly improved. The authors have addressed the concerns raised in the previous review and the manuscript is now suitable for acceptance.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have responded to all my suggestions. 

Reviewer 3 Report

Comments and Suggestions for Authors

Dear authors,

thank you for your reply to my notes/recommendations. After precise reading, I can see that your worked a lot in correction or improvement of your article. In my opinion, it is now clearer and I can recommend it to publishing.

Kind regards

Your reviewer

Reviewer 4 Report

Comments and Suggestions for Authors

All comments were taken into account in the revised manuscript.

Reviewer 5 Report

Comments and Suggestions for Authors

I thank the authors of the article for the changes made and for answering my questions. I wish you good luck in your future scientific work.