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Open AccessArticle
Peer-Review Record

Phosphorus Fractions in the Sediments of Yuecheng Reservoir, China

Water 2019, 11(12), 2646; https://doi.org/10.3390/w11122646
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Water 2019, 11(12), 2646; https://doi.org/10.3390/w11122646
Received: 16 September 2019 / Revised: 11 December 2019 / Accepted: 12 December 2019 / Published: 15 December 2019
(This article belongs to the Special Issue Lake and River Restoration: Method, Evaluation and Management)

Round 1

Reviewer 1 Report

see attachment

Comments for author File: Comments.pdf

Author Response

We thank very much for your insightful comments to improve our manuscript. According to your comments, we carefully revised the manuscript. Please see the detailed responses to each comment below.

Comment: 1. The objectives are not quite clear. The P fractions are investigated for better eutrophication control in the future. Yes, but there is no analysis of future conditions in this study. It simply states a fractional analysis of P components for 5 samples within this reservoir. The scope of the analysis described in the paper falls short of describing how to control eutrophication of the reservoir.

Response: We added a short discussion from line 23 to 26 and line 221 to 228 to describe how to control eutrophication of the reservoir.

 

Comment: 2. The content is a little simplistic in that it is a simple laboratory analysis of 5 samples. There is no description of the influx of P through time at the various tributaries. There is no P budget for this reservoir. There is no model simulation for future scenarios. There is no comparison with other sites in China for a possible comparative analysis. In essence, what is presented here is a laboratory study of a set of five measurements at a point in time.

Response: The main purpose of this paper is to analyze phosphorus fractions in sediments and to preliminarily evaluate its effect on eutrophication. In the future, we want to do scenario analysis based on long-term observation to calculate the phosphorus budget. We compared it with other lakes and reservoir from line 194 to 200.

 

Comment: 3. The article is in general very succinct and well written. It does not mean that it is meaningful. Let’s look at the conclusions. The P ranking order is given, which is fine new knowledge – isn’t it the same result as other sites in China? How do the measurements compare with other sites? The article sounds like the result of a master’s thesis where it is the first time that a student does something. Can the results be placed in a broader perspective? The suggestion that Po is from terrestrial plants sounds plausible, but is it not always the case? Is there any other evidence to support this claim? If I understand this well, Po is not the dominant component of P anyway. What else can be said about the main component, the CaPi? The strong correlation does not sound too surprising because P measurements seems to be everywhere at about the same levels. There is not much spatial variability in your 5 samples. Now the last two sentences should be deleted. The pollution from terrestrial plants needs to be reconsidered. Is the vegetation (e.g. forest) the real source of eutrophication problems? Is the biological characterization so important? It seems that the main fraction is inorganic. How about the source from fertilizers? There is allusion to cultivated agriculture in the title, but it vanished completely from the analysis. What is the deal here?

Response: We gave P ranking at line 218. We think that the phosphorus fractions of a large reservoir in the Taihang Mountains and in one of the most productive and intensively cultivated agricultural regions in North China for the first time is a new knowledge, although there is not significantly different from other lakes and reservoirs. Although the reservoir is located in an agricultural basin, Po is not a major part of the sediment, because the construction of the cascade reservoirs in the upper stream blocks a large number of terrestrial plants in the basin. Ca-Pi is more stable in the sediment and less easily released into overlying water. Pollution from terrestrial plants in sediment are more easily released into overlying water compared with Ca-Pi. In future study we intend to investigated the contribution of forests and crops to terrestrial organic matter.

 

Comment: 4. There should be a scale on Figure 1. It is said in the text line 61 that the reservoir covers an area of 18,100 km2 with a volume of 1.3 km3. Is this correct? – this is a huge reservoir! But in proportion, line 68 states that the drainage are is about 25k+12k, this 38,000 km2. Well, this is a very small drainage area compared to the size of this reservoir. Is this correct? Can you show the drainage basin and major tributaries on the figure 1 with the reservoir area?

Response: We added a scale and river name on Figure 1. The drainage area of the reservoir is 18100km2, the average depth of the reservoir is 20 m and maximum depth is 35m. We changed the description to avoid ambiguity at line 59.

 

Comment: 5. There is mention of eutrophication at several locations in the article. There should be a much better description of the eutrophication levels in terms of P and dependence on temperature. When does eutrophication occur in this area? What are the P levels in the tributaries at different times of the year? Is the source of P really from biological and organic sources? Is it from the fertilizers used by the farming communities in this river basin? There are so many unanswered questions that it is not clear that a tiny piece of information, like the reservoir sediment content, can justify a full paper in a refereed journal.

Response: The algae may appear occasionally in some areas of the reservoir between April and September, with a maximum concentration of 40 ug·L-1. We added a description at line 63.

 

Comment: 6 The title is also misleading. The second half of the title provides a link to agriculture that is not developed at all in the article. The title should be something like: “Phosphorous fractions in the sediment of Reservoir Yuecheng, China”

Response: We changed the title, see line 1.

Author Response File: Author Response.pdf

Reviewer 2 Report

The paper by Dr. Chenghua Dang et al. entitled "Phosphorus fractions and its fluxes from reservoir sediments of the productive and intensively cultivated agricultural region in North China" is an interesting study on the water quality observation and soil analysis in the reservoir. They focused on the risk of eutrophication in relation to phosphorus fractions in Yuecheng reservoir. They analysed 1) physiochemical properties of water, 2) physical and chemical characteristics of sediments, 3) P forms of sediments, 4) P diffusion fluxes at the water-sediment interface, and 5) some P forms correlation. They found that the TP and P diffusion fluxes were pretty high when they compare them between other sites. They concluded that it is important to pay attention to pollutions from terrestrials and internal P loading. 

I have the following concerns. 

P1 L2 its fluxes -> their fluxes ?

P1 L13 As -> As a result of ?

P1 L20 Yuecheng Reservoirs -> Yuecheng Reservoir (delete "s" as it is not plural)? (also P4 L131)

P1 L28 ";" needs between Zhangweinan River basin and Yuecheng Reservoir. If "basin" starts with small  character "b," then this should be consistent with all other "Basin"s (P2 L44 L64) ?

P1 L33 "the" is necessary?

P1 L38 "as" should be deleted?

P2 L44 locatied -> located

P2 L50-52 "as" and ", this (L51)" could be deleted. "has" should be modified to "have" and "this (L52)" to "these" ?

P2 L74 regions -> region ? If you put "s" here, all "region" should be plural. 

P3 Figure 1 should be a little bit larger to be better understood; right-up figure needs some countries' name such as Russia, Mongolia, China, and Philippine etc.; left-up figure needs river name such as Yellow River and Yangtze River etc., axis label, and a little bit larger numeric characters, and no need to describe the compass;left down figure needs scale; right down legend Provincial boundaries -> Provincial and national boundaries, and chain line -> solid line? (they are not clear)

P3 L83 Yuecheng reservoir -> Yuecheng Reservoir. If you use small "r" here, all "Reservoir"s' "R" should be replaced by small "r." (also P5 L149)

P3 L86 You need a blank between 4 and ℃.

P3 L87 24 h -> 24 hr

P3 L107-108 Is "P bound to aluminum (Al), ferrum (Fe) and manganese (Mn) oxides and" correct? Only hydroxides (Fe/Al-Pi) is referred to in this paper.

P4 L116 The word between water and sediment should be hyphen. It looks like minus sign.

P4 L126 Table 2 -> Table 1

P4 L131 One line should be inserted before the table title is described. 

P5 L143 One line should be inserted before the table title is described.

P5 L145 TOC data should be described in Table 2.

P5 L153 Which is correct PO or OP (Organic phosphate)?

P5 L156 a blank is necessary between "." and "C"

P6 L172 One line should be inserted before Figure 3. is described.

P6 Figure 3 Some markers are overlapped. White square, white circle, and white triangle would be better to be easily understood

P6 Figure 4. At YR3 the flux was low although P was high. I think that you should write how come this happened.

P7 L199 This sentence needs careful expression. Only Ca-Pi with TP is strong. a strong association -> an association   

P7 L205 Table 2 -> Table 4

P7 L205 One line should be inserted before the Table is described.

I think that generally this is a well-written paper that shows interesting data. It will be of interest to readers of this journal.

 

Author Response

We thank very much for your insightful comments to improve our manuscript. According to your comments, we carefully revised the manuscript. Please see the detailed responses to each comment below.

Comment: 1. L2 its fluxes -> their fluxes ?

Response: We modify the title according to your and other reviewer’s comment.

 

Comment: 2. L13 As -> As a result of ?

Response: We modify the sentence according to your suggestion at line 12.

 

Comment: 3. L20 Yuecheng Reservoirs -> Yuecheng Reservoir (delete "s" as it is not plural)? (also P4 L131)

Response: We modify the sentence according to your suggestion at line 19 and line 131.

 

Comment: 4. L28 ";" needs between Zhangweinan River basin and Yuecheng Reservoir. If "basin" starts with small character "b," then this should be consistent with all other "Basin"s (P2 L44 L64) ?

Response: We added ";" and modify the sentence according to your suggestion at line 27 and line 58.

 

Comment: 5. L33 "the" is necessary?

Response: We deleted "the" at line 32.

 

Comment: 6. L38 "as" should be deleted?

Response: We deleted "as" at line 38.

 

Comment: 7. L44 locatied -> located

Response: We modify the sentence according to your suggestion at line 44.

 

Comment: 8. L50-52 "as" and ", this (L51)" could be deleted. "has" should be modified to "have" and "this (L52)" to "these" ?

Response: We modify the sentence according to your and other reviewer’s suggestion at line 48 to 50.

 

Comment: 9. L74 regions -> region ? If you put "s" here, all "region" should be plural.

Response: We modify the sentence according to your and other reviewer’s suggestion at line 73.

 

Comment: 10. Figure 1 should be a little bit larger to be better understood; right-up figure needs some countries' name such as Russia, Mongolia, China, and Philippine etc.; left-up figure needs river name such as Yellow River and Yangtze River etc., axis label, and a little bit larger numeric characters, and no need to describe the compass;left down figure needs scale; right down legend Provincial boundaries -> Provincial and national boundaries, and chain line -> solid line? (they are not clear)

Response: We modify the Figure 1 according to your and other reviewer’s suggestion.

 

Comment: 11. L86 You need a blank between 4 and ℃.

Response: We modify the sentence according to your suggestion at line 85.

 

Comment: 12. L87 24 h -> 24 hr

Response: We modify the sentence according to your suggestion at line 86.

 

Comment: 13. L107-108 Is "P bound to aluminum (Al), ferrum (Fe) and manganese (Mn) oxides and" correct? Only hydroxides (Fe/Al-Pi) is referred to in this paper.

Response: We deleted manganese (Mn) according to your suggestion at line 106.

 

Comment: 14. L116 The word between water and sediment should be hyphen. It looks like minus sign.

Response: We modify the sentence according to your suggestion at line 115.

 

Comment: 15. L126 Table 2 -> Table 1

Response: We modify the sentence according to your suggestion at line 125.

 

Comment: 16. L131 One line should be inserted before the table title is described.

Response: We added a line at line 130.

 

Comment: 17. L143 One line should be inserted before the table title is described.

Response: We added a line at line 143.

 

Comment: 18. L145 TOC data should be described in Table 2.

Response: We added TOC data in Table 2 at line 144.

 

Comment: 19. L153 Which is correct PO or OP (Organic phosphate)?

Response: Po is defined as organic phosphate at line 105, so Po is correct.

 

Comment: 20. L156 a blank is necessary between "." and "C"

Response: We modify the sentence according to your suggestion at line 157.

 

Comment: 21. L172 One line should be inserted before Figure 3. is described.

Response: We added a line at line 177.

 

Comment: 22. Figure 3 Some markers are overlapped. White square, white circle, and white triangle would be better to be easily understood.

Response: We modify Figure 3 according to your suggestion at line 178.

 

Comment: 23. Figure 4. At YR3 the flux was low although P was high. I think that you should write how come this happened.

Response: We add a description at line 174.

 

Comment: 24. L199 This sentence needs careful expression. Only Ca-Pi with TP is strong. a strong association -> an association.

Response: We modify the sentence according to your suggestion at line 205.

 

Comment: 25. L205 Table 2 -> Table 4

Response: We modify the table caption according to your suggestion at line 211.

 

Comment: 26. L205 One line should be inserted before the Table is described.

Response: We added a line at line 210.

Author Response File: Author Response.pdf

Reviewer 3 Report

Review of the manuscript "Phosphorus fractions and its fluxes from reservoir sediments of the productive and intensively cultivated agricultural region in North China"

The paper addresses environmentally important question but it has too narrow scope and low novelty. The fundamental aspects are missing and the applied aspects are too narrow.

Reading the Abstract, one can see only local interest study without general issues.

The following sections of the article are considered:

Introduction – There are very few references in the introduction, it is necessary to add and compare with other areas. Materials and methods

Figure 1 – unreadable in black and white

Line 81-87 very poorly described

Results and discussion

Line 126 – Table 2 or 1???

Line 125-130 – Rewriting data from the Table

Table 1 – OPR or ORP

Figure 3 – Description and discussion??

Line 198 – Table 4 or 2???

Line 205 – Table 4 or 2??? What correlation coefficient did you use?

Conclusions

These might be useful results, but again, they are of local interest only

These results can be significant, but extensive comparisons are needed.

In my opinion, it is also necessary to evaluate the contribution of the rivers supplying the reservoir.

Author Response

Reply to Reviewer 3

We thank very much for your insightful comments to improve our manuscript. According to your comments, we carefully revised the manuscript. Please see the detailed responses to each comment below.

Comment: 1. Figure 1 – unreadable in black and white

Response: We modify the Figure 1according to your and other reviewer’s comment.

 

Comment: 2. Line 81-87 very poorly described

Response: We modify the sentence according to your and other reviewer’s suggestion at line 81 to 87.

 

Comment: 3. Line 126 – Table 2 or 1???

Response: We modify the sentence according to your and other reviewer’s suggestion at line 125.

 

Comment: 4. Line 125-130 – Rewriting data from the Table

Response: We modify the sentence according to your and other reviewer’s suggestion at line 125 to 129.

 

Comment: 5. Table 1 – OPR or ORP

Response: We change OPR to ORP at line 131.

 

Comment: 6. Figure 3 – Description and discussion?

Response: We deleted a decription at line 171 to 172.

 

Comment: 7. Line 198 – Table 4 or 2???

Response: We modify the sentence according to your and other reviewer’s suggestion at line 211.

 

Comment: 8. Line 205 – Table 4 or 2??? What correlation coefficient did you use?

Response: We modify the sentence according to your and other reviewer’s suggestion at line 211. We use Multiple Regression Analysis in this section, and we add a description at line 202.

 

Comment: 9. These might be useful results, but again, they are of local interest only.These results can be significant, but extensive comparisons are needed.In my opinion, it is also necessary to evaluate the contribution of the rivers supplying the reservoir.

Response: We added a discussion according to your and other reviewer’s suggestion at line 221 to line 228. In the future, we want to do scenario analysis based on long-term observation to calculate the phosphorus budget.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

My past review comments have not been addressed.

Author Response

We thank very much for your insightful comments to improve our manuscript. According to your comments, we carefully revised the manuscript. Please see the detailed responses to each comment below.

Point 1: The objectives are not quite clear. The P fractions are investigated for better eutrophication control in the future. Yes, but there is no analysis of future conditions in this study. It simply states a fractional analysis of P components for 5 samples within this reservoir. The scope of the analysis described in the paper falls short of describing how to control eutrophication of the reservoir.

Response: Although the Yecheng Reservoir is located in one of the most productive and intensively cultivated agricultural regions in North China, Po is not a major part of the sediment, it is simply because the construction of the cascade reservoirs in the upper stream blocked a large number of terrestrial plants in the basin. Thus, for water environment management in this basin, although the construction of a large number of water conservancy projects in the upper reaches of the river resulted in the decrease of inflow runoff, the pollutions from terrestrial plants or materials played a key role in the sediment phosphorus fraction, and they should be emphasized on the water environment management of river basin.

We added a short discussion from line 25 to 28 and line 224 to 231 to describe how to control eutrophication of the reservoir.

Point 2: The content is a little simplistic in that it is a simple laboratory analysis of 5 samples. There is no description of the influx of P through time at the various tributaries. There is no P budget for this reservoir. There is no model simulation for future scenarios. There is no comparison with other sites in China for a possible comparative analysis. In essence, what is presented here is a laboratory study of a set of five measurements at a point in time.

Response: The main purpose of this paper is to analyze phosphorus fractions in sediments and to preliminarily evaluate its effect on eutrophication. In the past two years, the inflow of Yuecheng Reservoir was almost zero due to the construction of the upper cascade reservoir. In the future, we want to do scenario analysis based on long-term observation to calculate the phosphorus budget. Compared with the other studies, the TP concentration in the sediments is much smaller than that of almost all typical eutrophic lakes. Compared to Dianchi and Taihu, a greater proportion (more than 70%, Figure 2) of TP in the sediments is made up of Ca-Pi which was considered of little mobilization under physic-chemical conditions comparing to Fe/Al-Pi. Moreover, it is speculated that the behavior of microbial degradation of Ca-Pi is driven by the microorganism to absorb reactive P nutrients from the environment for its own use. So, it may be controlled within a certain range by some related enzymes.

Table 3. Comparisons of TP and P diffusion fluxes between the reservoir and other areas

Site

TP (mg kg-1)

PO43--P diffusion fluxes

(mg m-2 d-1)

Reference

Hongze Lake, China

76.6–932.2

0.172–0.793

[24]

Dianchi Lake, China

1,537–4,695

1.00–4.36

[25]

Taihu Lake, China

213.7–724.4

0.76–4.57

[26,27]

Three Gorges Reservoir, China

415.5–1,047.9

-0.003–0.013

[28,29]

Yuecheng Reservoir, China

1576.3-2172.6

0.10-0.31

This study

 

We believe that the eutrophication treatment of the reservoir is a step by step process. Phosphorus budget is very important, but the fractions of sediment phosphorus is an important stage. Many studies of sediments have also focused only on the characteristic of phosphorus fractions, see Liu, Qi, et al. "The phosphorus speciations in the sediments up-and down-stream of cascade dams along the middle Lancang River." Chemosphere 120 (2015): 653-659 and Cavalcante, H., et al. "Phosphorus fractionation in sediments of tropical semiarid reservoirs." Science of the Total Environment 619 (2018): 1022-1029.

We compared it with other lakes and reservoir from line 197 to 203.

 

Point 3: The article is in general very succinct and well written. It does not mean that it is meaningful. Let’s look at the conclusions. The P ranking order is given, which is fine new knowledge – isn’t it the same result as other sites in China? How do the measurements compare with other sites? The article sounds like the result of a master’s thesis where it is the first time that a student does something. Can the results be placed in a broader perspective? The suggestion that Po is from terrestrial plants sounds plausible, but is it not always the case? Is there any other evidence to support this claim? If I understand this well, Po is not the dominant component of P anyway. What else can be said about the main component, the CaPi? The strong correlation does not sound too surprising because P measurements seems to be everywhere at about the same levels. There is not much spatial variability in your 5 samples. Now the last two sentences should be deleted. The pollution from terrestrial plants needs to be reconsidered. Is the vegetation (e.g. forest) the real source of eutrophication problems? Is the biological characterization so important? It seems that the main fraction is inorganic. How about the source from fertilizers? There is allusion to cultivated agriculture in the title, but it vanished completely from the analysis. What is the deal here?

Response: The rank order of P-fraction concentrations obtained from sample sites was Ca-Pi > Po > Fe/Al-Pi. Ca-Pi, varying from 72.4 to 81.9% of TP, was the primary driver of variation in TP. We gave P ranking at line 221. We think that the phosphorus fractions of a large reservoir in the Taihang Mountains and in one of the most productive and intensively cultivated agricultural regions in North China for the first time is a new knowledge, although there is not significantly different from other lakes and reservoirs. Although the reservoir is located in an agricultural basin, Po is not a major part of the sediment, because the construction of the cascade reservoirs in the upper stream blocks a large number of terrestrial plants in the basin. Ca-Pi is more stable in the sediment and less easily released into overlying water. Pollution from terrestrial plants in sediment are more easily released into overlying water compared with Ca-Pi. In future study we intend to investigated the contribution of forests and crops to terrestrial organic matter.

 

Point 4: There should be a scale on Figure 1. It is said in the text line 61 that the reservoir covers an area of 18,100 km2 with a volume of 1.3 km3. Is this correct? – this is a huge reservoir! But in proportion, line 68 states that the drainage are is about 25k+12k, this 38,000 km2. Well, this is a very small drainage area compared to the size of this reservoir. Is this correct? Can you show the drainage basin and major tributaries on the figure 1 with the reservoir area?

Response: We added a scale and river name on Figure 1. The drainage area of the reservoir is 18100km2, the average depth of the reservoir is 20 m and maximum depth is 35m. We changed the description to avoid ambiguity at line 62.

 

Point 5: There is mention of eutrophication at several locations in the article. There should be a much better description of the eutrophication levels in terms of P and dependence on temperature. When does eutrophication occur in this area? What are the P levels in the tributaries at different times of the year? Is the source of P really from biological and organic sources? Is it from the fertilizers used by the farming communities in this river basin? There are so many unanswered questions that it is not clear that a tiny piece of information, like the reservoir sediment content, can justify a full paper in a refereed journal.

Response: The algae may appear occasionally in some areas of the reservoir between April and September, with a maximum concentration of 40 ug·L-1. We added a description at line 66.

 

Point 6: The title is also misleading. The second half of the title provides a link to agriculture that is not developed at all in the article. The title should be something like: “Phosphorous fractions in the sediment of Reservoir Yuecheng, China”

Response: We changed the title to ‘Phosphorus fractions in the sediments of Yuecheng Reservoir, China’, see line 1.

Author Response File: Author Response.pdf

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