Spatial Distribution of Geochemical Anomalies in Soils of River Basins of the Northeastern Caucasus

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Reviewer Comments to Author：

This paper studies the geochemical distribution characteristics of 25 chemical elements in the soils of the uluchang River, sulak River and sunza river basins in the Northeast Caucasus of Russia. By collecting 101 topsoil samples, combined with inductively coupled plasma mass spectrometry (ICP-MS) analysis and multi index evaluation (such as pollution factor, enrichment index Igeo, pollution coefficient, etc.), the spatial heterogeneity, regional background values and abnormal distribution of element concentrations were revealed. This paper has made outstanding contributions to regional data accumulation and method innovation, but there are still some deficiencies in the discussion of the genetic mechanism of geochemical anomalies, which need to be modified.

Specific opinions are as follows:

(1) Although the author said in the introduction that it is very important to study the ecological environment of the Caucasus region, and few studies have discussed the influence of geological background on the enrichment of soil geochemical elements in the Caucasus region (78-86). However, the author did not introduce in detail what previous researchers have done in the Caucasus, which heavy metals in the soil in the Caucasus have obvious abnormal enrichment, and whether the soil heavy metal pollution in the region has affected the surrounding ecological environment? In addition, the geological background conditions and lithological distribution of the Caucasus region should also be supplemented in the introduction and 2.1 introduction to the study area.

(2) Fig. 2 lacks azimuth and scale, so the author is requested to complete it. In addition, there are 23 maps in the paper. The author is requested to select a combination of important maps and place them in the main body of the paper, and the other secondary maps are placed in the annex.

(3) Although the author used a variety of methods such as Igeo, EF, ZC and other indicators to identify the soil geochemical anomalies in the three basins of the Caucasus, whether the author considered collecting some rock samples to further prove that the soil geochemical anomalies are related to different geological backgrounds and lithology. Please add corresponding rock samples or calculate the chemical alteration intensity (CIA) of soils between different watersheds, and elaborate the formation mechanism of geochemical anomalies from the perspective of weathering of soil forming parent materials.

(4) In the abstract, the author discusses that the impact of human activities has increased in the areas close to settlements, industrial areas and roads. The article lacks space for discussion. The author is requested to supplement it completely in the disscusion. Has the author considered using lead isotopes to further identify the source of heavy metals in the "hot spot" of the study area?

(5) The author may consider adding the horizontal geochemical index reference of the global mountains (such as Alps and Andes) to the paper.

(6) Although the main purpose of this study is to identify geochemical anomalies, it is still necessary to assess the risk of heavy metals. The paper does not assess the potential toxicity of high concentrations of elements (such as Cd and Pb) to organisms. Please supplement and improve.

(7) In the discussion part of the article, the author is requested to supplement the results of this study and what strategies can be proposed for soil remediation or management based on abnormal distribution.

Comments for author File: Comments.pdf

Author Response

We thank the reviewer for the following suggestions.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors, I believe your work is interesting but needs a complete overhaul. Some parts are unclear. There are sentences that could be paragraph titles or not. The introduction should be updated. There are many studies on background values, even in the presence of river basins, using various determination techniques. Your method is not entirely clear and overestimates the regional value, which is also likely to be strongly influenced by lithology. Perhaps it is necessary to differentiate or find more values. Geology is hardly mentioned. There is no image concerning the geology of the area and little or no discussion of the possible relationship between geology and PTE values. It should be remembered that the geochemical background value is linked to geology. A value cannot be defined unless it is discussed in conjunction with the latter. Have you considered adding supplementary material? All the photos of the histograms in the results are superfluous in the text and could be placed in a supplement. That said, I will leave you some notes in the Word file.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English needs to be revised.

Author Response

We thank the reviewer for the following suggestions.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

General Evaluation:

This paper investigates the spatial distribution of geochemical anomalies in the soil of river basins in the Northeastern Caucasus, which is of significant practical importance. The study combines multiple geochemical indicators to assess the enrichment and distribution of heavy metals and trace elements in the soil and explores the influence of natural and anthropogenic factors on geochemical anomalies. The paper is well-supported by data and employs a comprehensive analytical approach, with conclusions that hold considerable reference value.

 

Main Suggestions for Revision:

1. The abstract needs to be more concise and focused: The current abstract is informative but does not sufficiently highlight the core findings of the research. It is recommended to summarize the research objective, main results, and conclusions more succinctly. Additionally, emphasize the potential significance of the research findings for the ecological environment management of the region.
2. The introduction requires stronger logic and relevance: The current introduction is broad but not closely tied to the study area. It is suggested to provide a more detailed review of existing soil geochemical studies in the Northeast Caucasus region and clearly state the innovation and necessity of this research. Identify the key scientific questions the study aims to address.
3. The materials and methods section needs more detailed descriptions:

(1) Criteria for selecting sampling locations: Provide a more detailed explanation of the specific standards and considerations for choosing sampling locations, such as different land use types, different altitudes, and different geological units.

(2) Soil sample collection methods: Describe the depth of soil sample collection, sampling tools, and mixing methods to ensure the representativeness of the samples.

(3) Provide quality control information for ICP-MS analysis, including detection limits, precision, and accuracy, to ensure the reliability of the data.

(4) Clearly explain the method for selecting background values.

4. The results section needs clearer presentation and analysis:

(1) Add statistical parameters such as coefficient of variation (CV) to Table 1 to assess the dispersion of the data.

(2) Make the Figures 3-9 clearer to facilitate reader understanding.

(3) Add spatial maps of element distribution to more intuitively display the spatial distribution characteristics of geochemical anomalies.

(4) Describe more clearly the content characteristics and spatial distribution patterns of heavy metals and trace elements in the soil of different river basins.

(5) Conduct a comparative analysis of the calculation results of different geochemical indicators to discuss the applicability and limitations of different indicators.

(6) Consider using statistical methods such as correlation analysis and principal component analysis to further explore the relationships between elements and their controlling factors.

5. The discussion needs more in-depth exploration and comparison:

(1) Conduct a more in-depth analysis of the causes of geochemical anomalies, considering the geological background, mineralization processes, and hydrogeochemical characteristics of the study area.

(2) Analyze the impact of human activities on soil heavy metals and trace elements and distinguish the contributions of natural and anthropogenic factors.

(3) Compare the results of this study with existing research in the region to discuss the consistency and differences in the findings. Compare with similar studies in other regions to analyze the universality and specificity of the research results.

6. The conclusion needs to be more concise and summarize the main findings and conclusions of the research.
7. Ensure the consistency, completeness, and accuracy of the references. Supplement recent relevant literature, especially studies on soil geochemistry in the Caucasus region.

Comments on the Quality of English Language

It is recommended to polish the language appropriately.

Author Response

We thank the reviewer for the following suggestions.

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Reviewer Comments to Author：

Thank the author for carefully replying to my previous comments and revising the manuscript. The author has responded to the questions and suggestions one by one, and provided detailed modification instructions. The quality of the revised manuscript has been significantly improved, and the problems previously concerned have been properly solved. The author has added regional heavy metal data in the introduction of the paper to illustrate the research status of heavy metal pollution in local soil. And the author has sorted out all the drawings. In addition, the author also puts forward some suggestions on regional management in the paper. These modifications have greatly improved the clarity and scientificity of the manuscript. At present, there are no obvious academic defects or major questions in the manuscript. The remaining minor format and language problems can be finally improved in the editing stage before publication.

Based on the full revision of the author and the quality of the current manuscript, I believe that the paper has met the publication requirements of this journal. Therefore, I suggest to employ this manuscript.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Reviewer Comments to Author：

Thank the author for carefully replying to my previous comments and revising the manuscript. The author has responded to the questions and suggestions one by one, and provided detailed modification instructions. The quality of the revised manuscript has been significantly improved, and the problems previously concerned have been properly solved. The author has added regional heavy metal data in the introduction of the paper to illustrate the research status of heavy metal pollution in local soil. And the author has sorted out all the drawings. In addition, the author also puts forward some suggestions on regional management in the paper. These modifications have greatly improved the clarity and scientificity of the manuscript. At present, there are no obvious academic defects or major questions in the manuscript. The remaining minor format and language problems can be finally improved in the editing stage before publication.

Based on the full revision of the author and the quality of the current manuscript, I believe that the paper has met the publication requirements of this journal. Therefore, I suggest to employ this manuscript.

Author Response

Thank you for your review.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors,

the text was improved, now is ok for publication 

Author Response

Thank you for your review.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript still requires some minor revisions.

 

1. The research background should be more targeted. The current introduction merely provides a general overview of the current research status of soil heavy metal pollution, but does not have a sufficiently close connection with the Northeast Caucasus region. It is necessary to supplement the current situation of soil geochemistry research in this region, the existing problems, as well as the entry point and significance of this study.
2. It is suggested to supplement the distribution map of sampling points in the study area and mark the latitude and longitude coordinates of the sampling points, so that readers can understand the spatial distribution of the sampling points.
3. Elaborate on the basis for selecting sampling points, such as topography and landform, geological background, land use type, etc. Explain the number of samples collected at each sampling point, the sampling depth, and the mixing method to ensure the representativeness of the samples.
4. The method for discriminating regional geochemical anomalies should explain the reasons. The method of determining geochemical anomalies by averaging values plus or minus two times the standard deviation is relatively simple. It is recommended to adopt a more scientific and reasonable anomaly discrimination method in combination with the actual situation of the study area.
5. The result description should avoid using subjective words such as "very high" and "very low", and should use specific numerical values to describe the element content.
6. The analysis of the causes of geochemical anomalies is crucial. It is necessary to conduct a comprehensive analysis by combining geological, mineral, and hydrological data. For example, the zinc anomaly in the Sunzha River Basin requires analyzing whether the anomaly is the result of natural mineralization or human pollution based on the known distribution of lead-zinc deposits in the region.
7. The current ecological risk assessment only considers three elements: As, Cd, and Pb. It is recommended to add Cu, Zn, Ni, etc.
8. The conclusion should be more concise and clear. The conclusion should be a high-level summary of the research results and should avoid repeating the content of the result section.

Comments on the Quality of English Language

My personal suggestion is to further polish the language.

Author Response

Thank you for your review.

We have made changes to the paper. Please see the attachment. 

Sincerely,

Ekaterina Kashirina, Roman Gorbunov, Ibragim Kerimov, Tatiana Gorbunova, Polina Drygval, Ekaterina Chuprina, Aleksandra Nikiforova, Nastasia Lineva, Anna Drygval, Andrey Kelip, Cam Nhung Pham, and Nikolai Bratanov

Author Response File: Author Response.pdf