Effect of Common Ions in Agricultural Additives on the Retention of Cd, Cu, and Cr in Farmland Soils

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Thank you for the invitation to review the manuscript titled "Effect of common ions in agricultural additives on the retention of Cd, Cu and Cr in farmland soils."

This article investigated the adsorption behavior of HMs, common anions, and dissolved organic matter (DOM) in alkaline soil of farmland under different experimental environments. The research results of this article can provide detailed insights into the interaction between HMs, DOM, and anions, which is of great significance for the targeted application of pesticides and fertilizers, as well as the effective control of HMs in farmland soil.

The specific modification suggestions are as follows:

1.   Page 1, Line 30-42: What are the specific environmental impacts of the variations in retention and release of the three soil heavy metal ions (HMs) mentioned in the text within the soil matrix? What significance does studying their changes hold? Please supplement and summarize existing relevant research findings.

2. In Figure 1, the change in Cl- (Competitive sorption) is not depicted in the adsorption variation diagram for Cd on the left side. Should this change be discussed in the main text?

3.   Page 7, Line 204-205: Are there other literature supporting this result? It is recommended to enhance this section with studies from other scholars to give the article's results more scientific validity.

4.   Page 9, Line 228-239: What components typically characterize the DOM characterized using EEM-PARAFAC? What are the similarities and distinctive features between the DOM characterized in the article and that characterized by other scholars?

5.    Page 13, Line 277-281: Is there other literature supporting this result? It is suggested to enhance this section with studies from other scholars to give the article's results more scientific validity.

Comments on the Quality of English Language

The overall English expression of the article is fluent, and no obvious grammar errors or inaccurate expressions are found.But please consider further refining the detailed English expression throughout the entire manuscript to improve clarity and coherence.

Author Response

Response to Reviewer 1 Comments

 

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Our research is an experimental study, summarizing the retention and release capabilities of heavy metals (HMs) in fluvo-aquic soil under common HM cation and anion environments through batch adsorption experiments and Excitation—Emission—Matrix Spectra (EEM) fluorescence quenching titration experiments. We found that the combined complexation of sulfate ions and dissolved organic matter (DOM) enhanced the soil's release capability for Cr. This discovery provides a new understanding for the environmental behavior of HM in soil and the removal of soil heavy metal pollution. The correction to the main text has been highlighted in the article.

 

Thank you for the invitation to review the manuscript titled "Effect of common ions in agricultural additives on the retention of Cd, Cu and Cr in farmland soils." This article investigated the adsorption behavior of HMs, common anions, and dissolved organic matter (DOM) in alkaline soil of farmland under different experimental environments. The research results of this article can provide detailed insights into the interaction between HMs, DOM, and anions, which is of great significance for the targeted application of pesticides and fertilizers, as well as the effective control of HMs in farmland soil.

The specific modification suggestions are as follows:

Comments 1: Page 1, Line 30-42: What are the specific environmental impacts of the variations in retention and release of the three soil heavy metal ions (HMs) mentioned in the text within the soil matrix? What significance does study their changes hold? Please supplement and summarize existing relevant research findings.

Response 1: Thank you very much. The stronger the soil's retention capacity for HMs, the greater the accumulation of HMs in the soil, which can pose toxic hazards to crops, increase the concentration of HMs in agricultural products, and potentially lead to health risks. Additionally, a higher release capacity of HMs from the soil indicates a deeper migration into the soil, thereby increasing the risk of groundwater contamination.

Changes in the retention and release of HMs can break the sorption equilibrium, resulting in additional pollution risks. As observed in the experimental phenomenon described in this study, the addition of SO₄^2- enhances the release capacity of Cr³⁺, leading to an increase in the concentration of Cr³⁺ in the soil solution. This can result in both crop uptake of Cr³⁺ and potential groundwater pollution. It is important to pay attention to such changes in the fate of HMs. Appropriate explanations have been included in the introduction section of this paper. Please refer to line 42-48.

 

Comments 2: In Figure 1, the change in Cl- (Competitive sorption) is not depicted in the adsorption variation diagram for Cd on the left side. Should this change be discussed in the main text?

Response 2: We greatly appreciate your comment. After careful confirmation, we have reset the range of the vertical axis to make the Figure1 clearer. We believe that in the new image, the change in Cl^- (competitive competition) can be identified. Please refer to Figure 1.

 

Comments 3: Page 7, Line 204-205: Are there other literature supporting this result? It is recommended to enhance this section with studies from other scholars to give the article's results more scientific validity.

Response 3: Thank you for your comments. Similar conclusions have also been reported in previous literature. Cerqueira et al[1] pointed out that most soils have a greater affinity for Cu than Cd, due to the favorable competition to Cu²⁺ for the adsorption sites than Cd²⁺. Mendes et al[2] found that in the ternary HMs mixed sorption system, the affinity of soil for Cr³⁺ is greater than that of Cu²⁺, and these conclusions are similar to the results in this paper. We have added appropriate explanations and references in the main text, please refer to line 258-270.

 

Comments 4: Page 9, Line 228-239: What components typically characterize the DOM characterized using EEM-PARAFAC? What are the similarities and distinctive features between the DOM characterized in the article and that characterized by other scholars?

Response 4: Thank you for your suggestion. EEM-PARAFAC typically characterize the DOM components into five regions[3]:

Region Ⅰ:Aromatic Protein: Tyrosine (Em (280~330)/Ex (200~250));

Region Ⅱ: Aromatic Protein Ⅱ: Tryptophan (Em (330~380)/Ex (200~250));

Region Ⅲ: Fulvic acid-like: Hydrophobic acid (Em (380~550)/Ex (200~250));

Region Ⅳ: Soluble microbial by-product-like: (Em (280~380)/Ex (250~340));

Region Ⅴ: Humic acid-like: Marine humic acides (Em (380~550)/Ex (250~400)).

The Humic-like components discovered in this study are similar to previous studies. Protein-like components characterized in the article is different from other scholars, which obtain DOM solution from oceans or lakes. These protein components may come from manure that has not fully decomposed, or from soil microbial activity, meanwhile it is also the most active organic component in complexing with HMs.

 

Comments 5: Page 13, Line 277-281: Is there other literature supporting this result? It is suggested to enhance this section with studies from other scholars to give the article's results more scientific validity.

Response 5: Thank you very much for your suggestion. A research conclusion indicated that sulfate ions may complexes with Cd (CdSO₄⁰_（aq）)，which increase the Cd concentration in solution[4], it is similar to the experimental results of batch adsorption in this study. we have innovated to provide a new experiment of considering the influence of anions in fluorescence quenching titration experiments of DOM and HMs. Previous literature lacks experimental research on this aspect, and as a result, we have not found much relevant research findings. Our exploration of the complexation effect of SO₄^2- on Cr ³⁺ represents a novel perspective, potentially implicating the role of DOM in these interactions.

 

References:

1. Cerqueira, B.; Covelo, E.F.; Andrade, L.; Vega, F.A. The influence of soil properties on the individual and competitive sorption and desorption of Cu and Cd. Geoderma 2011, 162, 20-26.
2. Mendes, L.A.; Bucater, L.F.P.; Landgraf, M.D.; Rezende, M.O.O. Role of Organic Matter in the Adsorption/Desorption of Cr, Cu and Pb in Competitive Systems in Two Different Soils. OALib 2014, 01, 1-5.
3. Chen, W.; Westerhoff, P.; Leenheer, J.A.; Booksh, K. Fluorescence Excitation−Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter. Environ Sci Technol 2003, 37, 5701-5710.
4. Berkelaar, E.J.; Hale, B.A. Cadmium accumulation by durum wheat roots in ligand-buffered hydroponic culture: uptake of Cd–ligand complexes or enhanced diffusion? Canadian Journal of Botany 2003, 81, 755-763.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The chosen topic, concerning the contamination of agricultural soils, is of high interest. Assessing the impact of common ions in agricultural additives explores how their presence affects the behavior and mobility of heavy metals in agricultural soils.

The abbreviation "HM" for heavy metal must be explained in the abstract.

The literature review in the introductory section addresses the impact of human activities on soil health and how the transfer of these elements can occur. However, the authors should also describe the results of the studies, what their conclusions were (as a starting point for the present research).

Citations are not correctly formatted in the present work. The MDPI format requires the format "[5]" instead of "(Liu et al. 2022; Zhu et al. 2021)". I kindly request the authors to rewrite all citations in the article, as they are incorrectly written.

Additionally, the line spacing is too large. The paragraphing of the text certainly needs to be modified.

The software used for statistical analysis is not specified, nor is the method of analysis described. I kindly ask the authors to provide a more detailed description of their objectives, methods, and the software used.

The quality of the images should be improved.

The discussion section should address aspects such as HM migration, transformation, bioavailability, and toxicity in soils more thoroughly and clearly. Therefore, the authors need to transition the experimental aspects towards utility by providing a more detailed interpretation. If the objective was more focused on the experimental validation of techniques, this should be mentioned in the paper.

In the conclusions section, the authors should elaborate on the last sentence: "Our study contributes to the experimental analysis of applying agricultural inputs to alkaline soils to avoid risks of soil pollution."

The References section is written completely wrong. The authors did not consider that references should be listed in the order of appearance in the manuscript, the year should be bold (not in parentheses), initials of authors should be followed by different punctuation marks, etc. References should also be numbered.

The presentation of the manuscript requires some improvements, which can increase the value of this paper.

Author Response

Response to Reviewer 2 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Our research is an experimental study, summarizing the retention and release capabilities of heavy metals (HMs) in fluvo-aquic soil under common HM cation and anion environments through batch adsorption experiments and Excitation—Emission—Matrix Spectra (EEM) fluorescence quenching titration experiments. We found that the combined complexation of sulfate ions and dissolved organic matter (DOM) enhanced the soil's release capability for Cr. This discovery provides a new understanding for the environmental behavior of HM in soil and the removal of soil heavy metal pollution. The correction to the main text has been highlighted in the article.

The overall English expression of the article is fluent, and no obvious grammar errors or inaccurate expressions are found. But please consider further refining the detailed English expression throughout the entire manuscript to improve clarity and coherence. The chosen topic, concerning the contamination of agricultural soils, is of high interest. Assessing the impact of common ions in agricultural additives explores how their presence affects the behavior and mobility of heavy metals in agricultural soils.

Comments 1: The abbreviation "HM" for heavy metal must be explained in the abstract.

Response 1: Thank you for your suggestion. We have corrected it in the abstract.

 

Comments 2: The literature review in the introductory section addresses the impact of human activities on soil health and how the transfer of these elements can occur. However, the authors should also describe the results of the studies, what their conclusions were (as a starting point for the present research).

Response 2: Thank you for your suggestion. We have strengthened the description of the conclusions from previous studies. Please refer to line 42-47, 93-95,105-107.

 

Comments 3: Citations are not correctly formatted in the present work. The MDPI format requires the format "[5]" instead of "(Liu et al. 2022; Zhu et al. 2021)". I kindly request the authors to rewrite all citations in the article, as they are incorrectly written.

Response 3: Thank you very much. The correct format of citations has been written.

 

Comments 4: Additionally, the line spacing is too large. The paragraphing of the text certainly needs to be modified.

Response 4: Thank you for your suggestion. We used appropriate line spacing throughout the entire document. We have removed some complex sentences and reduced their length to achieve a better reading experience.

 

Comments 5: The software used for statistical analysis is not specified, nor is the method of analysis described. I kindly ask the authors to provide a more detailed description of their objectives, methods, and the software used.

Response 5: We appreciate your comment, we have provided software used for statistical analysis. Please refer to line 229-232. However, because it is a common method and there is a word limitation in the main text, the details of our method are not described in the main text. Most methods are common ones that have been published, such as batch adsorption experiments[1], EEM+PARAFAC[2,3], quenching titration[4], Ryan-weber model[5] etc. Some methods are described in the supplementary materials.

 

Comments 6: The quality of the images should be improved.

Response 6: We appreciate your comment. We have carefully checked the format of the image and provided JPEG format(300dpi).

 

Comments 7: The discussion section should address aspects such as HM migration, transformation, bioavailability, and toxicity in soils more thoroughly and clearly. Therefore, the authors need to transition the experimental aspects towards utility by providing a more detailed interpretation. If the objective was more focused on the experimental validation of techniques, this should be mentioned in the paper.

Response 7: Thank you for your suggestion. Our previous version combined results with the discussion, which made the discussion unclear. Therefore, we added the discussion of sorption preferences of cations, the complexation of DOM and HMs and the experimental aspects towards utility. Please refer to Line 258-270,338-362.

 

Comments 8: In the conclusions section, the authors should elaborate on the last sentence: "Our study contributes to the experimental analysis of applying agricultural inputs to alkaline soils to avoid risks of soil pollution."

Response 8: We appreciate your comment. We have added additional discussion about this sentence. Please refer to 350-362.

 

Comments 9: The References section is written completely wrong. The authors did not consider that references should be listed in the order of appearance in the manuscript, the year should be bold (not in parentheses), initials of authors should be followed by different punctuation marks, etc. References should also be numbered.

Response 9: Thank you for your suggestion. We agree with your suggestion and we have rewritten to the format of the references.

 

The presentation of the manuscript requires some improvements, which can increase the value of this paper.

Reply: Thank you for your suggestion. We have improved the introduction, discussion, and article format to improve the quality of the paper.

 

 

References:

1. Shaheen, S.M. Sorption and lability of cadmium and lead in different soils from Egypt and Greece. Geoderma 2009, 153, 61-68.
2. Zhu, Y.; Jin, Y.; Liu, X.; Miao, T.; Guan, Q.; Yang, R.; Qu, J. Insight into interactions of heavy metals with livestock manure compost-derived dissolved organic matter using EEM-PARAFAC and 2D-FTIR-COS analyses. J Hazard Mater 2021, 420, 126532.
3. Stedmon, C.A.; Bro, R. Characterizing dissolved organic matter fluorescence with paral- lel factor analysis: a tutorial. Limnol Oceanogr:Method 2008.
4. Wu, J.; Zhang, H.; He, P.; Shao, L. Insight into the heavy metal binding potential of dissolved organic matter in MSW leachate using EEM quenching combined with PARAFAC analysis. Water Res 2011, 45, 1711-1719.
5. Ryan, D.K.; Weber, J.H. Fluorescence quenching titration for determination of complexing capacities and stability constants of fulvic acid. Analytical chemistry (Washington) 1982, 54, 986-990.

 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

 

The study investigates the influence of anions and dissolved organic matter (DOM) on the adsorption of cadmium (Cd), chromium (Cr), and copper (Cu) in alkaline soil. Results show that different anions affect the retention of these heavy metals differently, with sulfates significantly enhancing Cr-DOM binding, potentially hindering heavy metal retention. These findings provide insights for targeted pesticide and fertilizer application and efficient heavy metal control in agricultural soils.

The study was well conducted, but the high level of plagiarism is concerning. I recommend rewriting the manuscript to fix these issues. Even the captions for figures and tables are plagiarised; please fix this.

Author Response

Response to Reviewer 3 Comments

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Our research is an experimental study, summarizing the retention and release capabilities of heavy metals (HMs) in fluvo-aquic soil under common HM cation and anion environments through batch adsorption experiments and Excitation—Emission—Matrix Spectra (EEM) fluorescence quenching titration experiments. We found that the combined complexation of sulfate ions and dissolved organic matter (DOM) enhanced the soil's release capability for Cr. This discovery provides a new understanding for the environmental behavior of HM in soil and the removal of soil heavy metal pollution. The correction to the main text has been highlighted in the article.

 

The study investigates the influence of anions and dissolved organic matter (DOM) on the adsorption of cadmium (Cd), chromium (Cr), and copper (Cu) in alkaline soil. Results show that different anions affect the retention of these heavy metals differently, with sulfates significantly enhancing Cr-DOM binding, potentially hindering heavy metal retention. These findings provide insights for targeted pesticide and fertilizer application and efficient heavy metal control in agricultural soils.

 

Comments 1: The study was well conducted, but the high level of plagiarism is concerning. I recommend rewriting the manuscript to fix these issues. Even the captions for figures and tables are plagiarised; please fix this.

Response 1:  Thank you for your suggestion. We have rewritten the sentences that may have been plagiarized in manuscript, including captions for figures and tables.

 

 

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I appreciate the modifications made in the paper. The manuscript is now clearer, so it could be published as is.

Author Response

Response to Reviewer 2 Comments

 

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

 

Comments and Suggestions for Authors：I appreciate the modifications made in the paper. The manuscript is now clearer, so it could be published as is.

 

Response：We greatly appreciate your recognition and will continue to improve the quality of this manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for implementing my comments. The plagiarism rate is 29%, but it looks acceptable. However, no papers from 2023 and 2024 are referenced in the manuscript. Please update your literature and make relevant changes to the manuscript. 

Author Response

Response to Reviewer 1 Comments

 

1. Summary

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

 

Comments and Suggestions for Authors: Thank you for implementing my comments. The plagiarism rate is 29%, but it looks acceptable. However, no papers from 2023 and 2024 are referenced in the manuscript. Please update your literature and make relevant changes to the manuscript. 

 

Response: Thank you very much. We have carefully considered the suggestions and have made the following modifications:

1. We have rephrased certain sentences that could have been interpreted as plagiarized, while retaining the original wording for fixed expressions, experimental methods, and explanations of equation parameters.
2. We have replaced the references in the introduction section with papers from 2023 and 2024, and revised several sentences to enhance the overall quality of the manuscript, focusing mainly on the Introduction and Results and Discussion sections. To differentiate this version from the previous revised one, we have employed red highlighting, contrasting it with the blue highlighting used previously.

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

Dear Authors,

You have added one reference paper from 2024, and still no research papers from 2023. Please conduct a proper literature survey and update your literature.

Please check the header of the manuscript; it says 2023.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 4

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for implementing the comments. I can confirm that the literature survey is improved and meets the criteria.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files.

Comments and Suggestions for Authors：Thank you for implementing the comments. I can confirm that the literature survey is improved and meets the criteria.

 Response：We greatly appreciate your recognition and will continue to improve the quality of this manuscript.