The Effect of Remediation of Soil Co-Contaminated by Cu and Cd in a Semi-Arid Area with Sewage Sludge-Derived Biochar

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article submitted for review concerns the bioremediation of soil contaminated with cadmium and copper using biochar. Biochar is a very popular recycled material lately. The authors should be commended for using this material in such a way. However, the authors did not avoid several mistakes when writing the article. Below is my list of comments and questions:

1. The introduction only cites data from China, the authors should also refer to another continent for comparison.

2. I also believe that the introduction contains little information about the sources of these metals in the soil, but also no reference to the raw material from which biochar was made. It should also be noted that impurities may exist in such raw materials. For this purpose, I recommend using the article: https://doi.org/10.12911/22998993/103013

3. The article should be checked for subscripts and editing errors, as there are many of them, e.g. "HClO4-HNO3" in line 155.

4. in the introduction, the methodology for determining elements is very poorly described, there is no limit of quantification, no limit of detection, no measurements from reference material, no exact name of the device, etc.

5.Moreover, the materials and methods section should include a diagram of biochar production and a diagram of its application in the soil. There are no photos of what it looked like.

6. there is no reference to other studies in the description of the results. A discussion section with similar experiments from around the world should be added, because such experiments have been done. At least refer to 3 different similar experiments by other researchers.

Author Response

Thank you very much for reviewing the manuscript, Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript entitled "The effect of remediation of soil co-contaminated by Cu and Cd in a semi-arid area with sewage sludge-derived biochar" examined the role of the sewage sludge biochar for remediation of cadmium and copper. The study covers an interesting topic, and the overall presentation of the manuscript is also appropriate. However, I recommend major amendments at this level. In addition, please incorporate the below-mentioned comments.

Abstract section:

1.     Please underscore the scientific value added to your paper in your abstract. Your abstract should clearly state the essence of the problem you are addressing, what you did, and what you found and recommended. Moreover, the abstract needs careful reading and should precisely depict important results. It should have a stronger concluding sentence. That will help prospective abstract readers decide whether to read the entire article.

2.     Highlight the key findings of the study with % difference.

3.     Please conclude the abstract with future strategies and recommendations.

Introduction section:

1.        In the introduction, you must connect state-of-the-art to your paper goals. Please follow the literature review with clear and concise state-of-the-art analysis. This should clearly show the knowledge gaps identified and link them to your paper goals. Please reason both the novelty and the relevance of your paper goals. Discuss the previous studies that you are referring to. What are the Research Gaps/Contributions? The paper may not be considered further without a clear research gap and study novelty.

2.        The introduction section is abrupt, and background information is scattered. It lacks systematic layering and connectivity between the sentences as well as paragraphs.

3.        What were the objectives of this study?

4.        What was the hypothesis of the manuscript?

Materials and methods section

1. The Materials and Methods section lacks detailed information on experimental procedures. It is essential to describe how the authors measured soil parameters such as pH, water holding capacity, electrical conductivity, and cation exchange capacity. Additionally, the methodology for determining soil organic matter, available phosphorus, nitrogen, and potassium should be included. Please specify the instruments or techniques used for measuring these physiochemical properties of the soil.

2. The methodology for assessing urease and catalase activity in the soil is missing. Including this information is crucial for understanding the enzymatic activity and its impact on soil health and nutrient cycling.

3. Similarly, there is no mention of the method used to determine the total cadmium and copper concentration and their respective fractions in the soil. This information is vital for evaluating the contamination levels and potential risks associated with heavy metal presence in the soil.

4. It is recommended that the authors incorporate Principal Component Analysis (PCA) and correlation analysis into their study to enhance the visual presentation and provide a deeper insight into the relationships between different variables and parameters studied. These analytical techniques can offer valuable insights into the underlying patterns and associations within the dataset.

Results and Discussion Section

1.     It is advisable to present the Results and Discussion sections separately to enhance clarity and facilitate better understanding for the reader. This approach allows for a clear delineation between the presentation of results and the interpretation and discussion of those results, making it easier for readers to follow the logical flow of the research findings.

2.     In your discussion section, please link your empirical results with a broader and deeper literature review.

3.     One way to improve the Discussion is to avoid repeating results in this part. Discussion is very shallow and needs in-depth discussion with the recent literature published. In discussion, there is a lack of a mechanistic approach.

4.     Improve the caption of figures and tables; moreover, mentioned the abbreviation details used in tables and figure in footnote.

5.     Sewage sludge biochar can be a potential source of heavy metals. How did the authors address this issue? Can you explain their approach?

Conclusion section

Please ensure your conclusions section underscores the scientific value-added of your paper and/or the applicability of your findings/results. Highlight the novelty of your study. In addition to summarizing the actions taken and results, please strengthen the explanation of their significance. It is recommended to use quantitative reasoning compared with appropriate benchmarks, especially those stemming from previous work.

 

A professional edition should edit the language of this manuscript.

Comments on the Quality of English Language

Extensive english editing is required 

Author Response

Thank you very much for reviewing the manuscript, please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript titled ‘’ The effect of remediation of soil co-contaminated by Cu and Cd in a semi-arid area with sewage sludge-derived biochar ‘’ is an interesting work on biochar efficiency in remediation of heavy metal polluted soils. However, there are some important factors need to be improved before further process.

Line 16: The beginning of the abstract needs to be start with the main concern of the research in a general view then the go through in details.

Lines 16-20: ‘’ Biochar extracted from sewage sludge has been used to adsorb environmental pollutants, while its effectiveness in remediating soils contaminated with various heavy metals needs further investigation. This study used sewage sludge-derived biochar to remediate Cu and Cd co-contaminated soil in a semi-arid area for the first time. The effect of biochar on improving soil’s physico-chemical and biological properties and the immobilization of Cu and Cd were investigated.  ‘’ ->  All these three sentences are telling one thing! This section needs to be rephrased with clear content.

Line 20: ‘’ Applying the biochar significantly enhanced the water-holding capacity…. ‘’ -> Where is the experimental design? Before going through your results, there should be something about M&M!

Lines 20-27: Just reporting the findings based in some general terms like ‘’improved’’, ‘’increased’’, decreased’’, … is not enough!  There should be something about percentage of changes! If a treatment increased, please let us know how much this increase by numerical values is!

Lines 35-50: Please provide a data about global potential of sewage sludge and biochar from sewage sludge. Here is one paper you can find these data and add it here: https://doi.org/10.3390/ijerph191912983

Line 210: repair? Use suitable word!

Lines 305-309: regarding biochar porous structure and extended specific surface area add this ref: https://doi.org/10.1016/j.enconman.2023.117924

 

Author Response

Thank you very much for reviewing the manuscript, please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

all comments have been taken into account. I recommend the article for publication in its current form

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have significantly improved the quality of the manuscript, according to the reviewer's comments and suggestions. Now, the manuscript is suitable for publication.

Comments on the Quality of English Language

Minor English editing is required

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript has been notably improved and it has potential to be published.