Characterization and Risk Assessment of Nutrient and Heavy Metal Pollution in Surface Sediments of Representative Lakes in Yangxin County, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Although I recognise the effort that authors had regarding the sampling and analyses, the manuscript is very confusing and is not in conditions to be published, at least for now. From the Introduction to the Discussion, everything is presented in a very confusing way. The statistics are poor and some statistical analyses are mentioned throughout the text that are not properly referred to in the Data Analysis, and the Discussion seems like a follow-up to the Results. I recommend that if the authors really want to publish this work, they will have to redo the entire manuscript so that it will be publishable.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The quality of the English is not bad. The way the manuscript is structured, the dry sentences and lack of fluidity make the whole content less acceptable.

Author Response

Author Responses:

Dear expert, your comments on this paper are of great help to improve it. Thank you! Now we response to your questions and suggestions as follows:

 

1:

The introduction is very confusing. It's like a patchwork quilt where there's not really a common thread that leads the reader to understand exactly what is intended. It starts with an overly generalised sentence and then there's a lot of mixing sentences/subjects between organic compounds and metals, and locations. I suggest that this introduction should be rewritten, of course always starting from the general to the particular, and really framed in the work carried out.

Response: Thank you for your advice, you clearly pointed out my shortcomings and I read it again and realized that the logic of our quotes is not smooth enough. We have rewritten written the introduction and added to it based on your suggestion.

 

2:

The description of the study areas is limited to dry sentences, once again without a pattern or logic that makes the reader realise when they are talking about area A or B.

Response: Thank you for your suggestion. We have thoroughly polished the manuscript and added it with your suggestions.

 

3:

Anyone who knows the area will certainly know where the study area is located.  For the reader who doesn't know where the study area is, a more global framework is lacking.

Response: Thanks to your suggestion, we have redrawn the map of the study area and added information about the country so that readers can get a concrete idea of the general location of the area.

 

4:

The statistical methodology is poor. Why not use PRIMER+PERMANOVA to assess the significant differences between the lakes and within each lake, between the sampling stations? Even plot the systems and sampling stations using a PCO?

Response: Thank you for your suggestion, after seeing this suggestion I immediately went to search for the software and the statistical method, I found that it is a good statistical software, but due to the short modification period as well as the fact that I did not find enough instructional videos on Chinese learning sites, I was not able to complete the modification of the data analysis software. In the future, I will spend enough time to learn the software and apply it in the next my paper about phytoplankton. In China, many scholars apply SPSS and ORIGIN software to do data processing and analysis.

• Guo, J.; Wang, K.; Yu, Q.; Duan, X. B.; Liu, S. P.; Chen, D. Q. Pollution characteristics of the heavy metals and their potential ecological risk assessment in nearshore sediments of the middle reaches of the Yangtze Ｒ Acta Scientiae Circumstantiae. 2021, 41: 4625-4636. (In Chinese)
• Cao, S. W.; Liu, C. L.; Li, Y. S.; Li, J.; Hao, Q. C.; Gao, J.; Dong, Y.; Lu, C. M. Sources and ecological risk of heavy metals in the sediments of offshore area in Quanzhou Bay, Fujian Province. China. 2022, 49, 1481-1496. (In Chinese)
• He, J.; Li, F. L.; Tao, L.; Zhang, A.; Zhao Y. B. Distribution characteristics and ecological risk assessment of nitrogen, phosphorus and heavy metals in sediments of typical inland lakes: a case study of Wuhu Lake in Wuhan. Geol Surv China. 2022, 9, 110-118. (In Chinese)
• Liu, M.; Chen, J.; Sun, X.; Hu, Z. Z.; Fan, D. J. Accumulation and transformation of heavy metals in surface sediments from the Yangtze River estuary to the East China Sea shelf. Pollut. 2019, 245, 111-121.

 

5:

The discussion should be aligned with the results and not be a presentation of the results. This chapter should be rewritten after the results chapter has been reorganised.

Response: Thank you for your suggestion, I have placed the correlation data analysis in the results section, and the discussion section has been rewritten and explores the sources of contaminants in more depth. Due to my oversight, Principal Component Analysis (PCA) was not mentioned in the analysis methodology and has been revised and added. Thank you again for your advice, the issues you raised are very important and critical and I have gained a lot from your guidance!

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

Point 1.

This paper investigates the pollution of nutrient salts and heavy metals in the surface sediments of three lakes in Yangxin County, China. The study analyzes sediment samples from Lianhua Lake, Mati Lake, and North Lake, evaluating the distribution, pollution characteristics, and associated risks. The results indicate elevated levels of total nitrogen (TN), total phosphorus (TP), and various heavy metals. The nutrient salt pollution index is found to be severe, with relatively low ecological risks for TN and TP. However, certain heavy metals, particularly mercury (Hg), pose moderate to high ecological risks. The study provides valuable insights for implementing pollution prevention and control measures in the region.

 

Point 2.

This research is important as it assesses and reveals the distribution, pollution characteristics, and associated ecological risks of nutrient salts and heavy metals in the surface sediments of lakes in Yangxin County, China, providing crucial information for implementing effective pollution prevention and control measures in the region.

 

Point 3.

The Introduction section offers an extensive review of the literature, with a predominant focus on research carried out within China. However, it falls short in adequately analyzing studies conducted beyond China, requiring substantial improvement to ensure a more balanced and inclusive perspective.

To add more information above issue please consider the suggested research in your paper when enhancing the introduction section. Specific attention should be paid to the source of heavy metal pollution, like mining activity. Recommended references: 10.33271/mining16.04.071; 10.1201/b16354-43; 10.33271/mining17.02.112; etc. It will show that the problem of heavy metal pollution is important not only in China.

 

Point 4.

While the paper touches on the ecological risks of nutrient salts and heavy metals, a more detailed discussion on how these pollutants specifically affect the local aquatic ecosystems, including flora and fauna, would enhance the understanding of the environmental consequences.

 

Point 5.

What about the influence of initial rare-metal mineralization of water? Please refer to paper - Amralinova, B.; Agaliyeva, B.; Lozynskyi, V.; Frolova, O.; Rysbekov, K.; Mataibaeva, I.; Mizernaya, M. Rare-Metal Mineralization in Salt Lakes and the Linkage with Composition of Granites: Evidence from Burabay Rock Mass (Eastern Kazakhstan). Water 2023, 15, 1386. https://doi.org/10.3390/w15071386

 

Point 6.

The study provides a snapshot of sediment conditions in November 2020, but a discussion on any temporal trends or variations in pollution levels over time would contribute to a more comprehensive understanding of the environmental dynamics in the region.

 

Point 7.

The paper concludes with the identification of pollution sources, but a discussion on potential mitigation and remediation strategies, such as best management practices or policy recommendations, would be valuable.

 

Point 8.

Insights from the Nigerian and Algerian studies regarding policies, regulations, or management strategies implemented in response to groundwater pollution can be considered in the recommendations section of the Yangxin County study. Understanding successful approaches or challenges faced in different regions can inform more effective pollution prevention and control measures.

Egbueri, J. C. Heavy metals pollution source identification and probabilistic health risk assessment of shallow groundwater in Onitsha, Nigeria. Anal. Letters, 2020, 53, 1620-1638. https://doi.org/10.1080/00032719.2020.1712606

Dib, I. Multivariate statistical-based approach to the physical-chemical behavior of shallow groundwater in a semiarid dry climate: The case study of the Gadaïne-Ain Yaghout plain NE Algeria. Min. Miner. Depos. 2022, 16, 38-47. https://doi.org/10.33271/mining16.03.038

 

Point 9.

Lines 387-392. How does the presence of nutrient salts and heavy metals in the surface sediments align with the potential sources identified, such as fishery cultivation residual pollution, sewage discharge, traffic exhaust, and agricultural and industrial activities?

 

Point 10.

 

The manuscript demonstrates practical applicability and offers crucial theoretical insights for future studies. Upon addressing the outlined corrections, the paper is eligible for publication acceptance. The biggest strength of the manuscript lies in its dual merit of presenting practical applications and offering significant theoretical contributions for future studies. 

Author Response

Author Responses:

Dear expert, your comments on this paper are of great help to improve it. Thank you! Now we response to your questions and suggestions as follows:

 

1:

This paper investigates the pollution of nutrient salts and heavy metals in the surface sediments of three lakes in Yangxin County, China. The study analyzes sediment samples from Lianhua Lake, Mati Lake, and North Lake, evaluating the distribution, pollution characteristics, and associated risks. The results indicate elevated levels of total nitrogen (TN), total phosphorus (TP), and various heavy metals. The nutrient salt pollution index is found to be severe, with relatively low ecological risks for TN and TP. However, certain heavy metals, particularly mercury (Hg), pose moderate to high ecological risks. The study provides valuable insights for implementing pollution prevention and control measures in the region.

Response: Thank you for taking time out of your busy schedule to complete the review of our paper, which has been revised and embellished according to your suggestions.

 

2:

This research is important as it assesses and reveals the distribution, pollution characteristics, and associated ecological risks of nutrient salts and heavy metals in the surface sediments of lakes in Yangxin County, China, providing crucial information for implementing effective pollution prevention and control measures in the region.

Response: Thank you for your valuable suggestions, we have made changes and touches.

 

3:

The Introduction section offers an extensive review of the literature, with a predominant focus on research carried out within China. However, it falls short in adequately analyzing studies conducted beyond China, requiring substantial improvement to ensure a more balanced and inclusive perspective. To add more information above issue please consider the suggested research in your paper when enhancing the introduction section. Specific attention should be paid to the source of heavy metal pollution, like mining activity.

Response: Thank you for reminding me to fully realize the inadequacy of the introductory part and improve the status of domestic and international research in the second paragraph, emphasizing the research of mineral development on heavy metal pollution and citing relevant literature.

 

4:

While the paper touches on the ecological risks of nutrient salts and heavy metals, a more detailed discussion on how these pollutants specifically affect the local aquatic ecosystems, including flora and fauna, would enhance the understanding of the environmental consequences.

Response: Thank you for your your suggestions are critical. I have added the seriousness of heavy metal contamination for biohazards in lines 493-501.

 

5:

What about the influence of initial rare-metal mineralization of water? Please refer to paper

Response: Thank you for your suggestion, I have referenced key information from that literature and cited the paper in the discussion section.

 

6:

The study provides a snapshot of sediment conditions in November 2020, but a discussion on any temporal trends or variations in pollution levels over time would contribute to a more comprehensive understanding of the environmental dynamics in the region.

Response: Thank you for your suggestion, since the enrichment of heavy metals in sediments does not change much in a short time, only one sample was taken. It is hoped that in the next five years, a second sampling will be conducted to monitor the changes in heavy metal content and provide some basis for the protection of the ecological development of the area.

 

7:

The paper concludes with the identification of pollution sources, but a discussion on potential mitigation and remediation strategies, such as best management practices or policy recommendations, would be valuable.

Response: Thank you for your advice. I have added management practices and policy recommendations for the area in the conclusions section.

 

8:

Insights from the Nigerian and Algerian studies regarding policies, regulations, or management strategies implemented in response to groundwater pollution can be considered in the recommendations section of the Yangxin County study. Understanding successful approaches or challenges faced in different regions can inform more effective pollution prevention and control measures.

Response: Thank you for your valuable suggestions, I have carefully studied the literature you recommended and added some protective measures for heavy metal pollution in the region in the conclusion section.

 

9:

Lines 387-392. How does the presence of nutrient salts and heavy metals in the surface sediments align with the potential sources identified, such as fishery cultivation residual pollution, sewage discharge, traffic exhaust, and agricultural and industrial activities?

Response: Thank you for your suggestion. Based on principal component analysis and correlation analysis, we aim to determine if the sources of nutrient salts and heavy metal elements are the same. In other words, we explored whether these elements showed significant correlations to determine whether there was a common source of contamination. Subsequently, we combined the results of other scholars' studies on heavy metals in sediments from different regions to determine the sources of contaminants in the region.

 

10:

The manuscript demonstrates practical applicability and offers crucial theoretical insights for future studies. Upon addressing the outlined corrections, the paper is eligible for publication acceptance. The biggest strength of the manuscript lies in its dual merit of presenting practical applications and offering significant theoretical contributions for future studies.

Response: Thank you for your suggestions. We sincerely appreciate your enthusiastic work and hope that the corrections will be recognized by you. Thank you again for your comments and suggestions.

 

 

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Overall, the manuscript has been greatly improved, although there are still some small things to improve/correct. The authors have taken on board the tips that have been given and this has been reflected in the quality of the manuscript. I won't go into detail about each section at this stage, so the authors can see and analyse the comments in the attached document.

Most important notes:

1. The quality of some figures should be improved.

2. The PCA table should be replaced by PCA graphs with the sampling points plotted and the vectors corresponding to TN, TP and heavy metals (each per se) superimposed.

Good work

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The English is pretty good. Only a few minor flaws in syntax and verb tenses have been corrected, but nothing that jeopardises the quality of the manuscript.

Author Response

Author Responses:

Dear expert, your suggestions are very important to us. You can always point out the shortcomings of this paper directly. Thank you! We have adjusted some of the wording in this article to achieve a more precise expression. Now we response to your questions and suggestions as follows:

 

1: The image has been slightly improved based on my previous comment, however it is still of poor quality and the numbers of the sampling stations are barely noticeable. I suggest improving the image quality and increasing the size of the letters. Furthermore, the colors of the provinces on the map and in the legend do not seem to match.

Response：Thank you for your suggestion. We have modified the size of sampling point symbols and notes in the study area map, as well as the colors of provinces to facilitate clearer identification.

 

2：How was the adjustment process done? Based on which criteria?

Response：Hakanson's classification criteria are based on the toxicity coefficients of PCB, Hg, Cd, Pb, As, Cr, Cu, and Zn. However, there are slight differences between these eight pollutants and the eight pollutants in our study. Therefore, in order to ensure the accuracy of the potential ecological risk assessment results, corresponding adjustments have been made. In the original Hakanson standard, 133 is the total value of toxicity coefficients for the eight pollutants, and 150 is the threshold value for the first-level classification. Thus, the unit toxicity coefficient classification value is RIu=150/133=1.13.

In this study, Hg (30) and Cd (30) have the highest toxicity coefficients. The total toxicity value of these eight heavy metal elements is 88. Therefore, the adjusted threshold value for the first level is L1=88*1.13=99.44≈100. Each subsequent level threshold value is twice the previous level threshold value. By recalculating and reclassifying, new adjusted standards have been derived. This adjustment aims to more accurately reflect the potential ecological risk levels of the eight pollutants used in the study.

 

3：The PCA results presented in a Table does not show in a clear way the real behaviour of the variables regarding the PCA axes. This table should be replaced by the PCA graph. Authors can preferably present one PCA per Lake. Otherwise it will be very confused. Please be sure that the PCA graph has the corrected legends and quality.

Response: Thank you for your suggestion. I have changed the table of principal component analysis data into PCA graph, so as to obtain information more intuitively.

 

Reviewer 2 Report

Comments and Suggestions for Authors

I think that the authors have adequately addressed the comments made by the reviewers in the revised version of the manuscript. Therefore, I have no further comments.

I wish all the best to the authors.

Author Response

Author Responses:

Dear expert, Thank you for your recognition of our paper. Under your guidance, the quality of our paper has been greatly improved.In the future paper writing, we will always keep in mind your reminders and suggestions, so as not to make the same small mistakes.We sincerely wish you a happy day!