Spatial Assessment of Groundwater Quality and Health Risk of Nitrogen Pollution for Shallow Groundwater Aquifer around Fuyang City, China

Round 1

Reviewer 1 Report

The article is written well, clearly and read well.

On the other hand, the same results, the same conclusions, would be obtained if the chemical composition of the water from the evaluated 34 wells was compared with the standard for drinking water. It would also be found that the most unfavourable water is that which contains an increased, excessive amount of nitrate. These waters should not be used for drinking purposes as they may pose a health risk.

I just have a few technical notes.

1. Line 64 - quote citation National Chinese Standard,
2. Line 93 - terrain is high, terrain is low - this is something to reformulate, what does high, low terrain mean?
3. Line 220 - HI does not need to indicate, not counted in the work,
4. Line 308 - add for the above five sampling sites based on whose chemical elements / components is very poor quality of water,
5. Line 32 - really only over 1.5 billion people drink groundwater? No more? The other approximately 7 billion people is supplied with surface water? Check it please.
6. Write clearly in the introduction whether all 34 wells / boreholes are used to supply the population with drinking water.
7. Line 389 - groundwater has a negative effect reformulated - groundwater can have a negative effect.

Author Response

Please see attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Thank you for the opportunity to review your article “Spatial Assessment of Groundwater Quality and Health Risk of Nitrogen Pollution for Shallow Aquifer Around Fuyang City, China”  I enjoyed the topic and found many of the results to be informative.

First, I do believe it could benefit from additional English language editing.  There are a few sections I had to read multiple times to make sure I understood the message.

Line-specific comments:

Line 58: A more common term would be “spontaneous abortion” or “miscarriage” for pregnant women with Nitrate exposure.

Line ~151-152: You collected 34 samples.  Was this 1 sample at 34 locations?  Were they all collected on the same day?  I could use a little more information.

Line 155-157: Sent to the lab within 24 hrs and kept on ice until processing – How long were they stored before processing?  This left me a little concerned because some of the compounds you listed have hold times of less than 48hrs (at least the laboratories I’ve worked with).  Samples which are processed for Ammonia are also typically preserved with sulfuric acid.  Please add some text which clarifies this process so the reader knows the data that went into your analysis is of reliable quality.  This could add uncertainty to your data which is mentioned at the end of this review.

Line 157-160: Please list all 16 parameters from table 1. 

Line 161 Section 4.2: I like reading about these approaches but I found myself wondering what these five grades mean as it relates to the parameters measured.  A quick search showed that most studies include a table with the 5 categories and the range of the parameters – this would really improve understanding of what this section is doing.

Line 199 “However, China’s models assigns a unique parameter to reflect the actual contamination exposure and ensure the safety of drinking water in China” You appear to follow the EPA method, so this sentence is confusing.  I kept looking for this unique parameter but didn’t find it.  If you didn’t use this unique parameter, please remove the sentence.  If you did, please clarify where this parameter is.

Line 207 / Equation 8 and 9.  E is more commonly referred to as the average daily dose in non-carcinogenic risk assessments.

Line 343: “Consumption of small amount of pollutants through drinking water intake for long time will also cause health risk” One of the points of the non-carcinogenic health risk assessment is that these compounds don’t build up over time and are threshold based.  You did not do a carcinogenic assessment and therefore this statement is misleading and should be removed. 

General observation:

I really like the use of the fuzzy comprehensive assessment and the results from it.

My primary concern is the lack of depth on the risk assessment.  There are people doing incredible work incorporating uncertainty and variability into risk assessments through stochastic and probabilistic methods – many related to groundwater quality.  There is non-negligible natural temporal variability in water quality, uncertainty in laboratory measurements, natural variability between humans, and uncertainty in the parameters (such as the RfD) we use to calculate risk assessments.  This type of discussion about uncertainty and variability is common in risk assessment.  Researchers (as well as the EPA) have moved beyond point/discrete estimates of risk which are really a surface level application.  Given the gap between novel health risk assessments and the application of the concept in this paper, I suggest including:

1) content in the introduction discussing current health risk assessment approaches

2) explanation / justification of why you chose to do single/discrete estimates in the methods

3) discussion of the potential impact of uncertainty and variability on your results in the conclusions

Author Response

Please see attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

General comments

This study aims assessment of groundwater pollution in a selected city by using both water quality and the estimated health risk. Regarding the originality of the manuscript, the authors should present and discuss on the comparative results between the overall water quality (fuzzy comprehensive assessment) and the overall health risk (HI). A consideration on the different/similar characteristics among sampling points can be one of the important discussion points.

Specific comments

P4 3. Geological and Hydrogeological Setting

・There are no references.

・This part can be a shorter.

P1 L23-24:

Is the value “8.82%” same as the value in P8 L264? The value on P8 L264 indicated the ratio of samples exceeded the acceptable limit according to the National Groundwater Standard. Water quality and non-carcinogenic risk are different each other, so I think this sentence needs to be revised.

P7-:

There is no result of HI.

P7 Equation (8):

For the calculation of exposure dosage for adults, EF×ED= 365day/year×30 year =10,950, and this is equal to AT. Is this equation correct?

P7 Equation (10):

- Please write a description of “i”.

- HI_total is the sum of HQs for NH₄-N, NO₃-N and NO₂-N. I think HQ_i  is correct, not HI_i .

P7 L240:

What do you mean “blending”?

P9 Figure 2:

Table 1 covers all information shown in Figure 2. Please avoid duplication of result presentation.

P13 L337-338:

You have already written the same content on P8 L257-260. I don’t think this sentence is necessary.

P13 L342-344:

You said “consumption of small amount of pollutants through drinking water intake for long time will also cause health risk”. This means that the risks for parameters other than nitrate also need to be assessed although each concentration was below the acceptable limit. Hence the HQ values for all water quality parameters as well as the overall risk, HI, need to be presented and discussed.

P14 Figure 6:

Acceptable limit of HQ is 1 and the legend should include a “1” boundary.

P14 L354-355:

Table 3 shows that only three samples exceeded the acceptable guidelines. I think this sentence is not correct.

P14 L357: “1.44 and 2.696”

You wrote the range of HQ values in L353-354 (0.008-1.526 for adults and 0.014-2.544 for children). I think “The highest risks of nitrate are 1.526 and 2.544” is correct.

P15 L385: “0.136 and 0.227”

Please check these values. I think “0.129 and 0.241 (in P14 L354)” is correct.

Author Response

Please see attached file.

Author Response File: Author Response.pdf

Reviewer 4 Report

All comments are presented in the attached document.

Comments for author File: Comments.pdf

Author Response

Please see attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thank you for the considering the comments presented and responding to each.  

I am still a little unclear on the number of samples collected.  The total was 34 but the new line indicated 30 samples plus parallel samples at 4 locations.  But then you say EXCLUDING the parallel samples, there are 34 but it seems like there would be 30.  Please clarify the language on page 5 lines 165-168.

All other comments have been sufficiently answered.  

Author Response

We are very grateful for your kind comments and valuable suggestions.

 Reviewer #2

Comments and Suggestions:

Thank you for considering the comments presented and responding to each. 

I am still a little unclear on the number of samples collected.  The total was 34 but the new line indicated 30 samples plus parallel samples at 4 locations.  But then you say EXCLUDING the parallel samples, there are 34 but it seems like there would be 30.  Please clarify the language on page 5 lines 165-168. All other comments have been sufficiently answered.  

Response: I am sorry we did not explain the problem clearly. We mean we sampled 30 at 30 locations (one sample at each location), and sampled 2 samples at each of the other 4 locations (2 samples at each location). Actually, there are 38 samples at 34 locations (including 4 parallel samples).

Therefore, we had one sample at each of 34 locations, in which we had one more parallel sample at each of 4 locations. We have revisied it in L 176 - 177 in the revision.

Reviewer 3 Report

The manuscript has been partly revised but still remains critical lacks in convincible logic of research questions and establishment of originality. Publication is not recommended as it is.

General comments

This study aims assessment of groundwater pollution in a selected city by using both water quality and the estimated health risk. Regarding the originality of the manuscript, the authors should present and discuss on the comparative results between the overall water quality (fuzzy comprehensive assessment) and the overall health risk (HI). A consideration on the different/similar characteristics among sampling points can be one of the important discussion points.

Response: Thank you for your comment. We have added some information. Please see L384- 388.

-> Again I strongly suggest the authors to consider more seriously and carefully about the importance to “declare an originality” and to develop a “quantitative analysis and discussion” based on the originality. The Introduction section still lacks of a logical structure of research questions; highly insufficient to explain what have been known and unknown thorough previous researches and why, and how this study can contribute to solve the problems. Also, the addition above mentioned is still quantitative and the relationship between water quality and health risk should be statistically assessed and discussed.

Specific comments

P4 3. Geological and Hydrogeological Setting

- There are no references.

- This part can be a shorter.

Response: We sincerely thank you for valuable suggestions and all the comments to our work will be highly appreciated. We have added reference. Please see L129, L134 and L157.

-> Please make this part shorter by selecting necessary and unnecessary information from the viewpoint of aim scope of this study.

P1 L23-24:

Is the value “8.82%” same as the value on P8 L264? The value on P8 L264 indicated the ratio of samples exceeded the acceptable limit according to the national groundwater standard. Water quality and non-carcinogenic risk are different, so I think this sentence needs to be revised.

Response: Thank you for your suggestion. The value in L 23-24 also indicated the health risk is beyond the recommended level of USEPA in 8.82% (3 samples) of the wells for both adults and children, respectively.

-> I understood your explanation. However, related to the general comments, the meaning and the difference between water quality and health risk should be defined and considered more clearly.

P7: There is no result of HI.

Response: Thank you for your comment. HI is replaced by HQ in equation 10 (L 239).

-> OK.

P7 Equation (8):

For the calculation of exposure dosage for adults, EF×ED= 365day/year×30 year =10,950, and this is equal to AT. Is this equation correct?

Response: Thank you for your comment. Yes, it is correct. AT is the time period over which the dose is averaged (day), and it is derive by using pathway-specific period of exposure for non-carcinogenic effects (ED×365 days/year).

-> I do not agree with your answer. “EF×ED (=10,950)” in numerator is canceled by “AT (=10.950)” in denominator according to the current writing of the manuscript.

P7 Equation (10):

Please write a description of “i”. HI_total is the sum of HQs for NH₄-N, NO₃-N and NO₂-N. I think HQ_i is correct, not HI_i .

Response: Thank you for your valuable correction. We agree with the comment. It is corrected. Please see equation 10 (L 239) and We have added description of “i”in L 241.

-> OK.

P7 L240:

What do you mean “blending”?

Response: Thank you for your valuable correction. We have deleted the word. Please see ->

-> OK.

P9 Figure 2:

Table 1 covers all information shown in Figure 2. Please avoid duplication of result presentation.

Response: Thank you for your good suggestion. We think that Figure 2 with this article to call attention to understand that boxplots can be used to provide a quick and simple comparison of data sets.

-> I understood.

P13 L337-338:

You have already written the same content on P8 L257-260. I don’t think this sentence is necessary.

Response: Thank you for the reviewing meticulous work. It has been revised. Please see L 368.

-> OK.

P13 L342-344:

You said “consumption of small amount of pollutants through drinking water intake for long time will also cause health risk”. This means that the risks for parameters other than nitrate also need to be assessed although each concentration was below the acceptable limit. Hence the HQ values for all water quality parameters as well as the overall risk, HI, need to be presented and discussed.  

Response: Thank you for your valuable comments. We are so sorry for inconsistent writing. now we removed this part because our human health risk assessment only considered on non- carcinogenic risk. One of the points of the non-carcinogenic health risk assessment is that these compounds don’t build up over time and their risk is acceptable. [Human health risk assessment for chemical pollutants in drinking water source in Shizuishan city, northwest China].

-> OK.

P14 Figure 6: Acceptable limit of HQ is 1 and the legend should include a “1” boundary.

Response: Thanks the reviewer for the good suggestion. However, according to other reviewer’s comment, we deleted figure 6.

-> OK.

P14 L354-355: Table 3 shows that only three samples exceeded the acceptable guidelines. I think this sentence is not correct.

Response: Thank you for your valuable correction. It is corrected. Please see L 379.

-> OK.

P14 L357: “1.44 and 2.696”

You wrote the range of HQ values in L353-354 (0.008-1.526 for adults and 0.014-2.544 for children). I think “The highest risks of nitrate are 1.526 and 2.544” is correct.

Response: We sincerely thank you for valuable suggestions and all the comments to our work will be highly appreciated. We are so sorry to put obvious errors. This could bring trouble to reviewers and readers. Now we revised and updated. please see L 382.

-> OK.

P15 L385: “0.136 and 0.227”

Please check these values. I think “0.129 and 0.241 (on P14 L354)” is correct.

Response: Thank you for your valuable correction. We have corrected it. please see L 437- L438.

-> OK.

Author Response

We are very grateful for your kind comments and valuable suggestions.

Comments and Suggestions

The manuscript has been partly revised but still remains critical lacks in convincible logic of research questions and establishment of originality. The publication is not recommended as it is.

General comments

This study aims assessment of groundwater pollution in a selected city by using both water quality and the estimated health risk. Regarding the originality of the manuscript, the authors should present and discuss the comparative results between the overall water quality (fuzzy comprehensive assessment) and the overall health risk (HI). A consideration of the different/similar characteristics among sampling points can be one of the important discussion points.

Response: Thank you for your comment. We have added some information. Please see L384- 388.

-> Again I strongly suggest the authors to consider more seriously and carefully about the importance to “declare an originality” and to develop a “quantitative analysis and discussion” based on the originality. The Introduction section still lacks of a logical structure of research questions; highly insufficient to explain what have been known and unknown thorough previous researches and why, and how this study can contribute to solve the problems. Also, the addition above mentioned is still quantitative and the relationship between water quality and health risk should be statistically assessed and discussed.

Response: Again we are grateful for the reviewing meticulous work. We have added supplement information. Please see L 45-56, L75-77, L99-102, and L 407-416.

L 45-56: Therefore it is necessary to evaluate groundwater quality correctly. Various scientific approaches that contributed to significant quality improvements in water quality were reported [10-12]. Some of these methods include set pair analysis [13,14], matter element extension analysis [15,16], water quality index [17] and others were mainly studied before. All these methods mentioned above have their own merits and demerits. For example, in groundwater quality assessment, set pair analysis and matter element extension analysis can be more important to deal with the uncertainties, but their calculation processes are complex, so they are not easy for common engineers to understand their basic principles and concepts. Water quality index is easy to calculate, but unable to deal with uncertainties associated with the water quality standards and water quality parameters [12]. Fuzzy comprehensive assessment method was used to overcome the shortcomings associated with the above methods in this study.

L75-77: Wu et al. [31] conducted a study on severe nitrate pollution and health risks of a coastal aquifer and found that the groundwater nitrate concentrations exerted non-carcinogenic health risks for different age groups in the northern Shandong Peninsula of China.

L99-102: The study of [1] points out that a comprehensive understanding of the potential health risks of nitrate in drinking water is essential for making proper decisions to reduce the contamination and protect residents from health hazards.

L 407-416: As mentioned in Table 3, when the groundwater quality of wells S03, S05 and S16, and categorized as being gradeⅤ, which is classified as very poor groundwater quality, and was also deemed to be unsuitable for drinking purpose. And also these three sites will pose non-carcinogenic health risks to adults and children. This indicates that the non-carcinogenic risks of NO₃-N in very poor groundwater quality are beyond the permissible limit. Regions of poor and very poor groundwater quality can be targeted for more detailed investigation and tight monitoring programs. On the contrary, the sample site of S04 and S23 fall under poor and very poor groundwater quality but the non-carcinogenic health risks of NO₃-N were within an acceptable limit. For NO₃-N, the HQ values of about 88.2% of all samples were less than 1 for both adults and children when groundwater was classified as good and fair groundwater quality in the present study.

Specific comments

P4 3. Geological and Hydrogeological Setting

-> Please make this part shorter by selecting necessary and unnecessary information from the viewpoint of aim scope of this study.

Response: Thank the reviewer for the good suggestion. According to the suggestion, we have selected unnecessary information from L 153-158 because the aim of this study focuses on the shallow groundwater aquifer group.

L 153-158: Deep groundwater is deposited in strata below 50 m, which is not closely related to atmospheric precipitation and surface water, according to hydrogeological structure and exploitation status, the deep groundwater of loose rock is divided into 3 aquifer groups, namely, the second aquifer group (with about 50-150 m depth), the third aquifer group (with about 150-500 m depth) and the fourth aquifer group (with about 500-1000 m depth).

P7 Equation (8):

For the calculation of exposure dosage for adults, EF×ED= 365day/year×30 year =10,950, and this is equal to AT. Is this equation correct?

Response: Thank you for your comment. Yes, it is correct. AT is the time period over which the dose is averaged (day), and it is derived by using a pathway-specific period of exposure for non-carcinogenic effects (ED×365 days/year).

-> I do not agree with your answer. “EF×ED (=10,950)” in  numerator is canceled by “AT (=10.950)” in denominator according to the current writing of the manuscript.

Response: Thank you for your comment. The equation of exposure dose through intake can be simplified. Therefore, the multiplied value of “EF×ED (=10,950)” in the numerator is canceled by “AT (=10.950)” in the denominator. Please see these references [Groundwater Nitrate Contamination and Associated Health Risk for the Rural Communities in an Agricultural Area of Ningxia, Northwest China] and [Health risk assessment of nitrate exposure in groundwater of rural areas of Gonabad and Bajestan, Iran].

Reviewer 4 Report

Dear Authors,

I went throughout the revised version and saw that the manuscript was intensively changed and looks now better. However, some minor comments can be find in the attached document.

Good luck 

Comments for author File: Comments.pdf

Author Response

We are very grateful for your kind comments and valuable suggestions.

Comments and Suggestions:

Dear Authors,

I went throughout the revised version and saw that the manuscript was intensively changed and looks now better. However, some minor comments can be find in the attached document.

Good luck 

P2L94

Response: Again we are grateful for the reviewing meticulous work. According to the National Chinese

standards, groundwater is unacceptable for drinking when the NO₃–N contents in groundwater are higher than 20 mg/L. Please see this reference [General Administration of Quality Supervision, Inspection & Quarantine of China, Standardization Administration of China. Standards for groundwater quality (GB/T 14848-2017). Standards Press of China, Beijing (in Chinese): 2017].

The Km in the scale bars of 0-600 and 0-10 has to be spaced

Response: Thank you for your valuable comments on our manuscript. It is corrected. Please see Figure 1, 3, and 5.

P4 L 120,

Response: Thank you for your correction. It is corrected please see L 132.

P7 L 220, P7 L231, and P8 L 246

Response: Thank you for your comment. It is corrected. Please see L 235, L246, and L 261.

P7 equation 8 and 9 and P8 equation 10

Response: Thank you for your valuable correction. We deleted the, in our manuscript. Please see equations 8, 9, and 10.

P11 L 317

Response: Thank the reviewer this comment is helpful. We have added supplement information. Please see L 303-305, L 311-313, and L 321-323.

L 303-305: As can be seen from Figure 3(c), NO₃-N concentration is not uniformly distributed in the study region, and also very higher NO₃-N concentration was observed in the Datian, Chahua, and Central part of the area.

L 311-313: Sites with high concentrations of fluoride were mainly found in the southwest, southeast, northwest, and northeastern parts of the study area. The high concentration of fluoride in groundwater is mainly related to lithological reasons and is related to fluoride-bearing minerals [62].

L 321-323: Fe³⁺ with high concentrations mainly distributed in the southeast part of the study area, whereas Mn with high concentrations mainly existed in Chengji, Chahua, and southeast regions.

P12 L 339

Response: Thank you for your correction. It is corrected. Please see L 360-361.

L 360-361: The poor and very poor quality water is not suitable for drinking, but after proper treatment, it might be used for recreation and irrigation purposes.

P15 L 384 and L 402

Response: Thank you for your comment. It is corrected. Please see L 417 and L 435.

Round 3

Reviewer 3 Report

Please make a definitive conclusion on the Equation (8), if keep the present form or change it by removing the cancelled terms. If the present form is kept, the authors should add a clarification of the reason.

Author Response

Thank you for your patient work and kind comments and valuable suggestions. We have made a point-by-point response to comments. Please see the attachment.

Author Response File: Author Response.pdf