Changes in Speciation and Bioavailability of Trace Elements in Sewage Sludge after the Ozonation Process
Round 1
Reviewer 1 Report
Comments to authors:
I have revised your manuscript entitled “Changes in speciation of trace elements in sewage sludge after the ozonation process and its bioavailability for crop plants”. This is an interesting topic. But it needs some important changes.
· The most important question is what novelty in this study is.
· Abbreviations and acronyms should be used consistently throughout the manuscript.
· Units must be according to the International System of Units (SI) in the manuscript.
· Linguistic correction in the manuscript is taken into account.
· Line 31: “F1 fraction” which form does this fraction represent. The authors should include it in abstract.
· Lines 41-42: “The study demonstrated that the sewage sludge ozonation process did not cause significant changes in the content of the individual heavy metal fractions.”
· Line 52: “plant” what the meaning of.
· Line 55: “Agricultural use of sewage sludge for fertilization” Most of the research in this field does not recommend the use of sewage sludge in agriculture because it contains many pollutants.
· Lines 65-69: The authors should clarify the role played by the Ozonation process.
· Did the authors study the effect of ozonation process on the microbial activity in the sewage sludge?
· Line 89: “gravity filtration” what the meaning of. How did you do that?
· Line 110: “[21]” this reference is an error.
· Lines 124-129: This section represents soil properties. I suggest these properties be inserted in a Table.
· What the texture of this soil.
· “sand granulometric composition” what the meaning of.
· I suggest inserting sewage sludge properties in a Table.
· Line 130: “the surface layers of sandy soils” this is an error.
· What is the period of maize and wheat experiments?
· Why the total content of heavy metals in SS_N higher than SS_O.
· Soil samples were supposed to be taken after the cultivation of wheat and maize, in which heavy metals fractionation by sequential extraction procedure.
· What is the benefit of sequential extraction for heavy metals?
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript «Changes in speciation of trace elements in sewage sludge after the ozonation process and its bioavailability for crop plants» of Szostek M. et al. described the changes in speciation of trace elements in sewage sludge after the ozonation process and its bioavailability.
Some questions and remarks listed below:
1. The abstract prepared out of the journal rules (it must limited by 200 words)
2. Keywords need correction because almost fully repeat the title and sewage sludge wrote twice
3. The introduction seems similar size with abstract and will be better rewrite. Maybe will be better add an information about maize and wheat. The difference or not between these plant species in metals accumulation
4. In pot design noted that per a pot was used 6 grains of maize and 18 of wheat. This difference in amount of a plants per a pot can affect on values of translocation factor and caused a changes that described in conclusion
5. Is any plant’s parameters were investigated? The plant reaction can characterized a negative/positive effects of ozonation sewage sludge but from conclusion seems positive effect of ozonation on accumulation some essential elements for plants
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
This manuscript had studied the changes of heavy metals speciation in sewage sludge after the ozonation process and assessed its risk. The research is of great importance for the application of sewage sludge in agricultural land. However, the ozonation process of sewage sludge may affect the amounts of different forms of heavy metals, also the soil process of heavy metals in sewage sludge applied into soil influence the forms of them, so is the ozonation process or the soil process resulted in the difference of bioavailability of heavy metals in pot experiment? I recommend that the authors to deeply revise the manuscript for more clarity and scientific soundness. Some of the specific suggestions and comments are shown as follow:
1. Line 25, 35-37. BCF and BAF, which is right?
2. Line 124-126. What is the ratio of soil weight to water volume of the soil solution for the pH determination?
3. Line 129-130. The thickness of the surface layer of sandy soil needs to be specified, otherwise the concentration of heavy metals will be differentiated.
4. Line 134-135. Are the doses of sewage sludge applied according to dry weight or fresh weight?
5. Line 137-138. Why is the mean dry matter content in the sewage sludge used in SS_O than that in SS_N?
6. Line 184-187 and Figure 1. Why are the total concentrations of Mn, Cu, Ni, Cr, Pb, Cd different between the SS_N and SS_O?
7. The lines of the vertical and horizontal axes of all figures are not clear. All Figures in this manuscript are suggested to revise.
8. Line 235. There is not the D1, D2, D3 in Figure 1. The explanation is suggested to delete.
Author Response
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Author Response File: Author Response.docx
Reviewer 4 Report
In this study, two Sewage sludge non-ozonated (SS_N) and after ozonation process (SS_O) were evaluated in order to assess their potential impact on the natural environment, which is of great importance for practical agricultural production, and is recommended to be received after minor revision. I have read this article carefully and found some places need to be revised, the details are as follows.
1. the direct logical relationship between the introduction and the paragraphs is not strong, so I suggest to adjust it.
2. no clear scientific problem is seen in the introduction, and it is suggested to restate the scientific problem.
3. 2.7. Statistical analysis section, it is not clear what data analysis method is used? Generally, t-test is used for the difference between two treatments.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have not responded to all comments.
Author Response
Dear Reviewer,
Please find in the attachment our response.
New responses are marked in blue color.
Thank you for your time and attention.
Best regards
Authors
Authors
Author Response File: Author Response.docx
Reviewer 2 Report
Authors added changes.
Author Response
Dear Reviewer,
The authors are grateful for the contribution of the reviewer process and the positive evaluation of our manuscript.
Thank ypu for your time and attention
Best regards
Authors
Reviewer 3 Report
The authors addressed my questions but did not add them to the manuscript, suggesting that the answers of these concerns be added in the appropriate form to the according places in the manuscript.
Author Response
Dear Reviewer,
Please find in the attachment our response. New responses are marked in blue color.
Thank you for your time and attention.
Best regards
Authors
Author Response File: Author Response.docx
