Integrated Analysis of Heavy-Metal Pollution in Three Gorges Reservoir Sediments: Spatial Distribution, Source Apportionment, and Ecological Risk Assessment
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis study focuses on ‘Integrated Analysis of Heavy Metal Pollution in Three Gorges Reservoir Sediments: Spatial Distribution, Source Apportionment and Ecological Risk Assessment’. The manuscript in its current form is not suitable for publication due to several critical shortcomings. The writing contains informal and unclear expressions that reduce the clarity of the presentation. Furthermore, the Introduction fails to establish the novelty of the study or how it addresses gaps in previous research, particularly given the substantial existing literature on the Three Gorges Reservoir area. It remains unclear whether this work simply applies established methods to a new location or offers genuine conceptual or methodological advancements. The Materials and Methods section lacks essential details regarding chemical analytical procedures and quality control measures, which undermines the reliability and scientific rigor of the study. The Discussion largely restates results rather than providing critical interpretation or contextualization, which falls short of expected scholarly depth. Finally, the Conclusions are overly vague and do not meaningfully summarize the key findings, diminishing the impact of the study.
- Lines 11 to 13 do not clearly state the specific ecological threats posed by heavy metals in the Three Gorges Reservoir sediments.
- Line 15 mentions "Air-Space-Ground integrated monitoring data" but does not explain what this entails or how it was utilized.
- Line 21 mentions "significant spatial heterogeneity" but does not provide any quantitative measure or summary statistic to support this.
- Lines 22 and 24 should explain the meaning of Cu/Pb and Cd/Hg.
- Line 25 highlights Cd as the "primary ecological risk driver" but does not compare its risk level meaningfully with other metals.
- The objective of the study is missing in the Abstract.
- There is too much content in the abstract introducing the research methods, which is inappropriate. The structure of the abstract needs to be reorganized.
- Lines 44 to 56 describe the drawdown zone's dual role as a sink/source but remain superficial. They miss the opportunity to introduce a more sophisticated conceptual model.
- Lines 65 to 67 conclude that heavy metals "create persistent hazards for drinking water source security" as a broad, generic statement. The argument should be specifically linked to the mechanisms described in the previous paragraph.
- Lines 68 to 82 review previous studies as a mere cataloguing exercise. This section lacks synthesis and a critical gap analysis.
- Lines 83 to 101 state the aim but remain entirely methodology-focused. The introduction should conclude with clear, explicit research questions or hypotheses derived from the identified gap.
- The knowledge gap and innovation point of present research is missing in the Introduction section.
- Line 123 in Figure 1 should retain compass and scale or kilometer grid. The region of China where the study area is located needs to be marked. The map misses watershed boundaries, known anthropogenic source locations, flow direction, and sediment accumulation zones, which are essential for interpreting spatial results.
- Line 126 states the use of a "core sampler" without specifying the type.
- Line 133 describes digestion as a destructive analytical preparation step that must precede analysis, not storage. This indicates a potential lapse in methodological description.
- Line 138 provides detection limits for Fe and Mn that are orders of magnitude too high to be relevant given their mean concentrations. This suggests the analytical method was not optimized for these major elements. The detection limit for Hg is presented as 0.002 while the minimum value for Hg is 0.00, which indicates questionable data results.
- Line 143 uses regional soil background values for sediment assessment, which is a significant and potentially invalid methodological choice. Sediment geochemical backgrounds are often distinct from soil backgrounds.
- Lines 181 to 184 provide a software list but omit the specific algorithms, packages, and functions used. This lack of computational transparency makes the analysis impossible to reproduce exactly.
- Section 2 Materials and Methods is devoid of any mention of Quality Assurance/Quality Control. There is no reference to the use of certified reference materials, analytical duplicates, procedural blanks, or spike recoveries.
- Lines 188 to 219 present analysis methods for EC, DO, pH and other parameters that have not been introduced in the Methods section, which makes the results questionable.
- The titles of sections 3.1.1, 3.1.2, and 3.1.3 appear to be the same
- Line 248 presents Figure 2 with font that is difficult to read.
- The Correlation Analysis Between Sediment Metals and Water Physicochemical Properties section lacks significance indicators.
- Section 3.2.3 presents PCA results without critical validation metrics. There is no mention of the Kaiser-Meyer-Olkin measure or Bartlett's test of sphericity, which are essential to demonstrate the dataset's suitability for PCA.
- In Table 9, the sum of Percentage of Datas for RI (%) is not 100%, which makes the results questionable.
- The 4. Discussion Section is insular, only referencing the study's own results. It fails to contextualize findings within the wider body of knowledge. For example, how do the Cd concentrations and ecological risks compare to those reported in other mega-reservoirs globally? Does the deep-layer Cd enrichment align with sediment core studies from other industrial watersheds? This missing dialogue with other studies isolates the paper and diminishes its contribution.
- Line 443 recommends 'This necessitates stringent anthropogenic source controls' in a way that is too vague and generic to be useful. The conclusion should specify what kind of controls would be appropriate.
Comments on the Quality of English Language
The English could be improved to more clearly express the research.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe reviewed MS of Haitao Yan et al. addresses the issue of heavy metal pollution in sediments of Three Gorges Reservoir in the middle-lower Yangtze River basin in China. The study area is crucial for both environmental safety and sustainable development of the vast region but at the same time it is extremely ecologically vulnerable. Although the results and conclusion of the MS in the present form are technically mainly of a local importance, the uniqueness of the study area adds to its greater environmental significance and makes it worth publication in Water.
The data obtained are novel and well presented. The tables and figures are consistent and well designed.
The reference list is complete and up to date. The English of the manuscript is good but needs to be polished.
Introduction, Methods, Results and Discussion need improvement.
In Introduction, justification of the target heavy metal list and specific anthropogenic point sources of particular metals in the reservoir is not addressed.
Methods lack in depths of sampling points/bathymetry of the reservoir; analytical apparatus countries of origin; laboratories and institutions where analytical routines were carried out; literature references for sample digestion, elemental analysis, certified reference materials, origin and credibility of hydrochemical characteristics, and some details of data processing.
Results and discussion miss comparative analysis of own data and literature sources addressing previous data and similar research on heavy metal distribution and behavior in fluvial sediments of the study area and other regions.
Please, find further Specific comments in the attached file.
Comments for author File: Comments.pdf
please check the repeats and subsection titles in the text
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
The study is well done. It may have scientific soundness expressed by the number of reads and citations. However, the manuscript has no discussion. The Authors’ results are not discussed. Due to this my advice to the Editor is: ‘reconsider after major correction’
- The study has no discussion. The results are not discussed with other results. The Discussion chapter has no citation. The Authors’ results are not discussed. In present form of the manuscript the Discussion chapter is a part of Conclusions chapter. The Results chapter has four citation, this is too little for so interesting material and analyses done by Authors. This is the resason for 'major correction'.
- The second thing about the manuscript I have to complain is the editing:
2.1. 3.1.1. Subchapter has no title, the same is with: 3.1.2. and 3.1.3. subchapters.
2.2. Table 7. Line for Fe is not readable!. Why the table is so narrow?
2.3. Figures: 7 and 2. Are not readable! They are definitely to small!
2.4. Please write units in SI for instance mg kg-1 d.m.
2.5. Please explain and expand all abbreviations (TEL, ERL, PEL, TP, TN, TOC, Turb., DO, EC, especially since they are not mentioned in the Material and Method Chapter
2.6. Please correct: as, cd, cr, pb, hg in References number 58.
2.6. In same figures (1, 3, 7, 9, 10, 11). Please consider to use abbreviations. For instance MR instead of Miao River, XR instead of Xiangxi River. In Material and method chapter write the full names (in English language transcription) but latter on use shortened forms. This let you save space and make figures more readable. For no Chinese readers this let you draw attention from the ‘strange geographical names’ to the data. The MR or XR are friendly in any language, for any Reader.
- Please consider to add to the Keywords ‘Source Apportionment’.
- I have some questions. They are debatable.
4.1. What acids did you use to digest the sample?
4.2. Why did you carry on with 0-65 cm sediment layer?
4.3. How did you collect the samples?
4.4. In Subchapters 3.2.1. and 3.2.2. you apply correlation analysis. Do you use parametric or nonparametric (Spearman correlation analyse)?
4.5. What is homo or heterogeneity of water physicochemical properties in Three Gorges Reservoir? How do the: TP, TN, TOC, Turb., pH, DO, EC and Temp. represent the water physicochemical properties in correlations from Figure 4.
4.6. You study the metal concentrations along the Reservoir and up and down the 65cm sediment layer. In three-dimensional coordinate system along is x coordinate, up and down is z coordinate and what about with y coordinate? If I guess a sample was taken in the middle of the River/Reservoir what are the metal concentrations 200m north or south from this point? What do you think what is the diversity of metals in width of the Reservoir?
4.7. Why didn’t you use water physicochemical properties (TP, TN, TOC, Turb., pH, DO, EC, Temp.) in Principal Component Analysis (Table 8 and figure 6).
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsAccept in present form
Reviewer 2 Report
Comments and Suggestions for AuthorsThe MS has been significantly amended and in its present form can be accepted for publication.
Reviewer 3 Report
Comments and Suggestions for AuthorsDear Authors,
I accept the answers and improvements. I support my high opinion about the manuscript.
My advice to the Editor is ‘accept the manuscript’.
