Pollution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of the Three Gorges Reservoir
Round 1
Reviewer 1 Report
Dear Editor,
the paper " Pollution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of the Three Gorges Reservoir" by Shui et al. presents quite interesting data on the spatial distribution of heavy metal content in riverbanks sediments from Yangtze river tributaries in the Three Gorges reservoir area. The pollution degree and the potential ecological risk are evaluated on the basis of appropriate parametrization, whereas there is an wrong overuse of the statistics in last part of the paper that has to be eliminated. The presented manuscript mainly suffers for a very poor English language that makes it unreadable, often leading to misleading interpretations. While reading the manuscript, I realized that there was little attention in the its preparation: in Fig. 1 Chinese terms appear in the inset, the Geoaccumulation Index is called “land accumulation index” or again “ground accumulation index”, the dendrogram of Fig. 5 is called “pedigree diagram”. The presented maps of Fig. 1 and 2 do not include any estuary feature, I can only see confluences of tributaries in the Yangtze river. I therefore recommend reconsidering the manuscript only after a deep English language revision, a reorganization of the presented figures and the correct application of statistical methods.
Author Response
We gratefully thank the editor and all reviewers for their constructive ramarks and useful suggestions, which are very helpful in improving our manuscript. We have taken your criticisms comments and suggestions. Your comments were modified and response point by point.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Presented research is interdisciplinary and combines issues from geochemistry, toxicity and environmental risk assessment. River pollution and its monitoring based on heavy metals is an international need. The article contains interesting and helpful information and results presented in the paper are valuable from monitoring point of view, but the manuscript should be corrected , especially regards :
The current introduction is too much focused on research area, and is not sufficient, it should be more informative and more scientific advanced and soundness and should clearly explain the problem.
Subsection 2.1 – starts with a capital letter
The background value of this paper refers to the average content of heavy metals in the sediments of the Yangtze River in the 1990s. – values and reference literature should be supplemented
Line 117 – space - Lars Hakanson
Line 124-125 “….I, Tir refer to the toxicity response coefficient of single pollutant (Ni, Cu, Zn, Pb, Cd, Cr, As and Hg are 5, 5, 1, 5, 30, 2, 10, 40)” -reference literature should be supplemented
Page 6- page/text can not be horizontal, only eventually table on the separate page
Please correct number of significant digits according to standards ( in whole manuscript, particularly in all tables) e.g. line 227 table 6 .
In my opinion there is no sufficient information about methodology - especially chemical procedures and quality assurance.
Reference materials - Were there any reference material used? What about reproducibility?
References must be corrected and fulfilled.
There is no conclusion! - It should be separate subsection with the scientific advanced and soundness assumption summation.
Author Response
We gratefully thank the editor and all reviewers for their constructive ramarks and useful suggestions, which are very helpful in improving our manuscript. We have taken your criticisms comments and suggestions. Your comments were modified and response point by point.
Author Response File: Author Response.pdf
Reviewer 3 Report
Table 1: correct ”No ploution”
Conclusions: do not exist
Author Response
We gratefully thank the editor and all reviewers for their constructive ramarks and useful suggestions, which are very helpful in improving our manuscript. We have taken your criticisms comments and suggestions. Your comments were modified and response point by point.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear Editor,
the revised version of the paper " Pollution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of the Three Gorges Reservoir" provided by Shui et al. is certainly improved with respect to the previous one. Most of the manuscript has been rewritten, conclusions added, and most of the methodological flaws and terminology corrected.
However, the revised manuscript still suffers for a poor English language, and cannot be published in the present form (see also attached pdf for some suggestions). Moreover, the presented results have to be consistent with the significant digits, as also suggested by another reviewer.
I suggest to the authors the use of an English language editing service.
Comments for author File: Comments.pdf
Author Response
Dear Editor：
Thank you for your Suggestions and comments on the paper. We apologize for the grammar problem，The manuscript has been revised according your comments. I have submitted the manuscript to MDPI for language improvement.
All the best with your
Fengyi Chang
Hubei University of Technology
Original manuscript：Cu, Zn, Pb and Cr was enriched in sediments in recent years. The results of Igeo show that the pollution degree is as follows: Pb > Cu > Zn > Cr > Cd > Ni > As > Hg.
Revised Manuscript：Cu, Zn, Pb, and Cr have been enriched in sediments in recent years. The results of Igeo show that the pollution degree is as follows: Pb > Cu > Zn > Cr > Cd > Ni > As > Hg.
Original manuscript：And it will be causing "secondary pollution" to the water and worsening the water quality [5,6].
Revised Manuscript：This will cause "secondary pollution" in the water and worsen the water quality [5,6].
Original manuscript：Since the impoundment of the three Gorges Reservoir, the flow velocity in the reservoir has slows down.
Revised Manuscript：Since the impoundment of the Three Gorges Reservoir, the flow velocity in the reservoir has slowed down.
Original manuscript：Xiaoqing X et al have analyzed the concentration of heavy metals in the main stream sediments of the Three Gorges Reservoir in different periods [17,18], but there are few studies on the tributary ediments. Therefore, this paper analyze the heavy metals of surface sediments (Ni, Zn, Cu, Cd, Cr, Pb, As, Hg) in the six important tributaries of the Three Gorges Reservoir and its estuary. Geoaccumulation index and potential ecological risk index are important methods for evaluating and analyzing heavy metals in sediments, which can intuitively reflect the impact of human activities on heavy metals and the impact of heavy metals on the environment. So, this paper uses these assessment method to evaluate heavy metal pollution, and uses cluster analysis and principal component analysis to carry out pollution traceability analysis. The results can provide a scientific basis for the management and protection of the ecological environment of the Three Gorges Reservoir.
Revised Manuscript：Xiaoqing X et al. analyzed the concentrations of heavy metals in the sediments of the main stream of the Three Gorges Reservoir in different periods [17,18], but there have been few studies on the tributary sediments. Therefore, this study analyzed the heavy metal contents of surface sediments (Ni, Zn, Cu, Cd, Cr, Pb, As, Hg) in the six important tributaries of the Three Gorges Reservoir and its estuary. The geoaccumulation index and the potential ecological risk index are important methods for evaluating and analyzing the heavy metal content in sediments, as they can intuitively reflect the impact of human activities on heavy metals and the impact of heavy metals on the environment. So, this study used these assessment methods to evaluate heavy metal pollution, and cluster analysis and principal component analysis were used to carry out pollution traceability analysis. The results can provide a scientific basis for the management and protection of the ecological environment of the Three Gorges Reservoir.
Original manuscript：In May 2019, 12 sampling points were determined by GPS positioning in the six important tributary and estuary of the three Gorges Reservoir.
In May 2019, 12 sampling points were determined by GPS positioning in six important tributaries and estuaries of the three Gorges Reservoir.
Original manuscript：After natural air-drying, sediment samples are grounded and crushed by an agate mortar and sifted by 200 meshes.
Revised Manuscript：After natural air-drying, sediment samples were ground and crushed by an agate mortar and sifted by 200 meshes.
Original manuscript：Compare with the national standard limit of 80 mg/kg, the concentration in Wushan was 394.64mg/kg.
Revised Manuscript：In contrast with the national standard limit of 80 mg/kg, the concentration in Wushan was 394.64 mg/kg.
Original manuscript：No ploution
No pollution
Original manuscript：According to the analysis of potential ecological risk index, the average number of heavy metals in sediments in the three Gorges reservoir is lower than 40, which indicating that they all have a low pollution level.
Revised Manuscript：According to the analysis of the potential ecological risk index, the average number of heavy metals in sediments in the three Gorges reservoir is lower than 40, which indicates that they all have low pollution levels.
Original manuscript：Cd is mainly contributed pollutants to the three sampling sites of Yunyang, Xiaojiang and Xinjin, which was consistent with the results of the previous analysis.
Revised Manuscript：Cd is the main contributor to pollution at the three sampling sites of Yunyang, Xiaojiang and Xinjin, which is consistent with the results of the previous analysis.
Original manuscript：The metal elements in sediments are mainly affected by natural weathering and human activities in the basin. And the influence degree is determined by the types of the input water metal elements.
Revised Manuscript：The metal elements in sediments are mainly affected by natural weathering and human activities in the basin. Additionally, the degree of influence is determined by the types of water metal elements present.
Author Response File: Author Response.pdf
Reviewer 2 Report
I accept in present form.
Author Response
Dear reviewer：
I have submitted the manuscript to MDPI for language improvement. Thank you for your Suggestions and comments on the paper.
All the best with your
Fengyi Chang
Hubei University of Technology
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
Dear Editor,
the revised version of the paper " Pollution Characteristics and Ecological Risk Assessment of Heavy Metals in Sediments of the Three Gorges Reservoir" provided by Shui et al. is now improved. However, many logical points and grammar have to be corrected before the paper can be accepted for publication.
A list of suggested correction for the authors is attached below:
- In the introduction, not only “physical and chemical processes” are responsible for heavy metals accumulation in surface sediments.
I suggest to replace the sentence: “After entering the water environment, heavy metals can quickly deposit into the sediment through complex physical and chemical processes [4].”
with: “After entering the water environment, heavy metals can quickly deposit into the sediment through complex physical, chemical and biological processes [4, Natali and Bianchini, 2018].”
quoting the reference: “Natural vs anthropogenic components in sediments from the Po River delta coastal lagoons (NE Italy) Environmental Science and Pollution Research 25 (3), 2981-2991 by C. Natali and G. Bianchini, where bioaccumulation processes have been found to be responsible for anthropogenic heavy metal enrichment in lagoon surface sediments.
- I suggest to replace the sentence: “It is also conducive to the economic development and ecological protection of the Three Gorges Reservoir environment [12].”
with: “Moreover, it is conducive to the economic development and ecological protection of the Three Gorges Reservoir environment [12].
- Maybe “Yan X et al.”?
- I suggest to replace the sentence: “Therefore, this study analyzed the heavy metal contents of surface sediments (Ni, Zn, Cu, Cd, Cr, Pb, As, Hg) in the six important tributaries of the Three Gorges Reservoir and its estuary.”
With: “Therefore, this study analyzed the heavy metal (Ni, Zn, Cu, Cd, Cr, Pb, As, Hg) contents of surface sediments in the six important tributaries of the Three Gorges Reservoir and their estuaries.”
- I suggest to replace the sentence: “In May 2019, 12 sampling points were determined by GPS positioning in six important tributaries and estuaries of the three Gorges Reservoir. The sampling locations are shown in Figure 1.”
With: “Samples were collected in May 2019 from 12 sampling points along six important tributaries and estuaries of the three Gorges Reservoir (Fig.1). Each sampling point was georeferenced by a portable GPS device. The tributary sampling points……..”
- Remove “at home and abroad” all long the text, it is meaningless in a scientific paper.
- Maybe “2.3. Pollution degree Evaluation methods” ??
- 1. Spatial Distribution of Heavy Metals in the Surface Sediments of the Three Gorges Reservoir.
- Figure 2. Concentration maps of heavy metals in surface sediments from the Three Gorges Reservoir area
- Again 394.64 mg/kg ??. I asked in the previous review to be consistent with significant digits. Correct it in the text and Tables.
- Remove “Category” as x-axis label in Fig. 3
- “…….the risk of Cd pollution in the Three Gorges Reservoir should be taken seriously into account.”
- “In addition, it is clear from Figure 2 that the pollution….”
- “Table 6. Temporal variation of heavy metals in sediments in the Three Gorges Reservoir area over the last 20 years.”
- “The contents of Ni and As were similar to those in 1999,..”
- “4.2. Sources of Heavy Metals in the Three Gorges Reservoir.”
- Remove : “4.3. Source of Surface Stream Sediments in the Three Gorges Reservoir” because the title above already includes the text of sub-chapther 4.3.
Author Response
We gratefully thank the editor for your suggestions. We have taken your comments, and modified point by point. We hope our work can now be accepted for publication.
1. Comments: In the introduction, not only “physical and chemical processes” are responsible for heavy metals accumulation in surface sediments.I suggest to replace the sentence: “After entering the water environment, heavy metals can quickly deposit into the sediment through complex physical and chemical processes [4].”with: “After entering the water environment, heavy metals can quickly deposit into the sediment through complex physical, chemical and biological processes [4, Natali and Bianchini, 2018].”
Reply: Thank fou your valuable suggestions. We have replaced the sentence and cited relater literature in the proper place of the manuscript. (P. 1, Line 44-46; P. 11, Line 339-340).
2. Comments: I suggest to replace the sentence: “It is also conducive to the economic development and ecological protection of the Three Gorges Reservoir environment [12].”
with: “Moreover, it is conducive to the economic development and ecological protection of the Three Gorges Reservoir environment [12].
Reply: Thank fou your valuable suggestions. We have replaced the sentence in the manuscript. (P. 2, Line 55-57).
3. Comments: Maybe “Yan X et al.”?
Reply: Thank fou your valuable suggestions. We have replaced the Yan X et al into Yan in the manuscript. (P. 2, Line 61).
4. Comments: I suggest to replace the sentence: “Therefore, this study analyzed the heavy metal contents of surface sediments (Ni, Zn, Cu, Cd, Cr, Pb, As, Hg) in the six important tributaries of the Three Gorges Reservoir and its estuary.”With: “Therefore, this study analyzed the heavy metal (Ni, Zn, Cu, Cd, Cr, Pb, As, Hg) contents of surface sediments in the six important tributaries of the Three Gorges Reservoir and their estuaries.
Reply: Thank fou your valuable suggestions. We have replaced the sentence in the manuscript. (P. 2, Line 68-70).
5. Comments: I suggest to replace the sentence: “In May 2019, 12 sampling points were determined by GPS positioning in six important tributaries and estuaries of the three Gorges Reservoir. The sampling locations are shown in Figure 1. With: “Samples were collected in May 2019 from 12 sampling points along six important tributaries and estuaries of the three Gorges Reservoir (Fig.1). Each sampling point was georeferenced by a portable GPS device. The tributary sampling points……..”
Reply: Thank fou your valuable suggestions. We have replaced the sentence in the manuscript. (P. 2, Line 80-82).
6. Comments: Remove “at home and abroad” all long the text, it is meaningless in a scientific paper.
Reply: Thank fou your valuable suggestions. We have removed the phrase in the manuscript. (P. 3, Line 103-104)
7. Comments: Maybe “2.3. Pollution degree Evaluation methods” ??
Reply: Thank fou your valuable suggestions. We have replaced the title in the manuscript. (P. 3, Line 101).
8. Comments: 1. Spatial Distribution of Heavy Metals in the Surface Sediments of the Three Gorges Reservoir.Figure 2. Concentration maps of heavy metals in surface sediments from the Three Gorges Reservoir area
Reply: Thank fou your valuable suggestions. We have replaced the title of the figure in the manuscript. (P. 2, Line 9; P. 5, Line 171).
9. Comments: - Again 394.64 mg/kg ??. I asked in the previous review to be consistent with significant digits. Correct it in the text and Tables.
Reply: Thank you so much for your careful check. We feel so sorry for our negligence which your mentioned last time. We have checked the whole paper and revised all the figures in this paper to four significant figures. If there is any mistake in our revision, please give your valuable suggestions. (P. 5, Line 185; P. 6, Line 191; P. 9, Line 248).
10. Comments: Remove “Category” as x-axis label in Fig. 3
Reply: Thank fou your valuable suggestions. We have replaced the figure in the manuscript. (P.7, Line 211).
11. Comments:“…….the risk of Cd pollution in the Three Gorges Reservoir should be taken seriously into account.”
Reply: Thank fou your valuable suggestions. We have replaced the sentence in the manuscript. (P. 8, Line 226-227).
12. Comments:“In addition, it is clear from Figure 2 that the pollution….”
Reply: Thank fou your valuable suggestions. We have replaced the sentence in the manuscript. (P. 8, Line 241).
13. Comments:“Table 6. Temporal variation of heavy metals in sediments in the Three Gorges Reservoir area over the last 20 years.”
Reply: Thank fou your valuable suggestions. We have replaced the title in the manuscript. (P. 9, Line 247).
14. Comments:“The contents of Ni and As were similar to those in 1999,..”
Reply: Thank fou your valuable suggestions. We have replaced the sentence in the manuscript. (P. 9, Line 250-251).
15. Comments:“ 4.2. Sources of Heavy Metals in the Three Gorges Reservoir.”
Reply: Thank fou your valuable suggestions. We have replaced the sentence in the manuscript. (P. 9, Line 257).
16. Comments: Remove : “4.3. Source of Surface Stream Sediments in the Three Gorges Reservoir” because the title above already includes the text of sub-chapther 4.3.
Reply: Thank fou your valuable suggestions. We have removed the title “4.3. Source of Surface Stream Sediments in the Three Gorges Reservoir” in the manuscript. (P. 9, Line 283).
Author Response File: Author Response.pdf
