Appraisal of Groundwater Vulnerability Pollution Mapping Using GIS Based GOD Index in Tiruchendur, Thoothukudi District, India

Round 1

Reviewer 1 Report

Reviewer’s Comments

 

Overall comment

The theme of the manuscript addressing the Appraisal of groundwater vulnerability pollution mapping using GIS based GOD Index in Tiruchendur, Thoothukudi District, India. The authors have made a good effort to identify the appraisal of groundwater vulnerability pollution. Results are also presented clearly and concisely. However, there is always room for improvement to raise the caliber of research, so nothing is ever final.

 

The article is well-structured. However, it is important that the authors must improve the discussion part to further highlight the geological importance related to groundwater vulnerability pollution mapping. I am not able to find out any figure or table inside the paper This would greatly benefit the international readership. What is the innovation of the presented article?

 

 

I would like to thank the authors of the article for its fluent text. Throughout the article, I noticed some points that, if corrected, could enhance the article

 

 

Other comments

 

·         There is a need to revisit the Introduction part. It is suggested to develop coherency in the writeup. It is suggested to write a paper of different countries to build this section

 

It is suggested to read the following paper and build your introduction section

Oroji, B. Groundwater vulnerability assessment with using GIS in Hamadan–Bahar plain, Iran. Appl Water Sci 9, 196 (2019). https://doi.org/10.1007/s13201-019-1082-x

Bera, A., Mukhopadhyay, B. P., Chowdhury, P., Ghosh, A., and Biswas, S., 2021, Groundwater vulnerability assessment using GIS-based DRASTIC model in Nangasai River Basin, India with special emphasis on agricultural contamination: Ecotoxicology and Environmental Safety, v. 214, p. 112085.

Ahmad, N., Khan, S., Ehsan, M., Rehman, F. U., and Al-Shuhail, A., 2022, Estimating the Total Volume of Running Water Bodies Using Geographic Information System (GIS): A Case Study of Peshawar Basin (Pakistan): Sustainability, v. 14, no. 7, p. 3754

Mehmood, A., Qadir, A., Ehsan, M., Ali, A., Raza, D., and Aziz, H., 2021, Hydrogeological studies and evaluation of surface and groundwater quality of Khyber Pakhtunkhwa, Pakistan: Desalination and Water Treatment v. 244, p. 41-54.

 

·         In section “3.4. Mitigation of groundwater sources from vulnerability:” This section needs more discussion that supports your results.

 

·         Conclusion This section should be short in length. It is suggested to remove unnecessary information from this section

 

 

·         I am not able to find out any figure or table inside the paper. It is cited inside but not properly presents. 

Author Response

Reviewer #1:

The theme of the manuscript addressing the Appraisal of groundwater vulnerability pollution mapping using GIS based GOD Index in Tiruchendur, Thoothukudi District, India. The authors have made a good effort to identify the appraisal of groundwater vulnerability pollution. Results are also presented clearly and concisely. However, there is always room for improvement to raise the caliber of research, so nothing is ever final.

 

The article is well-structured. However, it is important that the authors must improve the discussion part to further highlight the geological importance related to groundwater vulnerability pollution mapping. I am not able to find out any figure or table inside the paper. This would greatly benefit the international readership.

Response: Thank you for your time to critically read our manuscript and offering suggestions. Our response to each of your comment is as follows:

 

• What is the innovation of the presented article?

Response: Many researchers have carried out Thoothukudi water quality and its suitability studies, but no one conducted the vulnerability studies in Tiruchendur Taluk. The result of this GOD model study will help the police makers and planners for preparing groundwater management plan in the near future. This predicting groundwater vulnerability map can be further utilized as a base map for management of groundwater pollution and its planning.

 

I would like to thank the authors of the article for its fluent text. Throughout the article, I noticed some points that, if corrected, could enhance the article

Response: Thank you for your time to critically read our manuscript and offering suggestions. Our response to each of your comment is as follows

 

• There is a need to revisit the Introduction part. It is suggested to develop coherency in the write-up. It is suggested to write a paper of different countries to build this section

Response: Suggestion Incorporated.

 

• In section “3.4. Mitigation of groundwater sources from vulnerability:” This section needs more discussion that supports your results.

Response: As per reviewer comments this section produced. Suggestion Incorporated.

 

• Conclusion: This section should be short in length. It is suggested to remove unnecessary information from this section

Response: Conclusion section revised. Necessary innovative things are provided to make the readers interesting.

 

• I am not able to find out any figure or table inside the paper. It is cited inside but not properly presents.

Response: All the figures and tables are provided in revised version.

• One major point that I would like to make is in the logic of the article. One issue where things are sometimes blurred is the difference between groundwater vulnerability and groundwater pollution.

Vulnerability - As authors point out in the introduction it is "the potential for contaminants to occur in a given event."

Pollution - This is when pollution has actually occurred in the groundwater.

Just because an area is vulnerable to pollution does not mean that it is polluted. And an area that is not vulnerable can still be polluted. At times the author seems to conflate these ideas. If they find an area that has high EC and elevated NO3-N, this does not necessarily mean that it is vulnerable. It just means that the vulnerability that was there was been exploited by an actual pollution source.

Response: We agree with your point and thanks again for developing my manuscript writing skills. We have referred to the articles mentioned above and appreciate the valuable feedback. "Groundwater vulnerability is conceptualized on the assumption that groundwater vulnerability may act as a partial buffer to groundwater against natural influences (Baalousha, 2006; Hasiniaina et al., 2010; Bera et al., 2021)”. We have modified entire manuscript. Suggestion Incorporated.

• Another wrinkle in this is the coastal aspect of EC. If some of these areas have high EC, it could just be coastal intrusion into groundwater. Some of this would happen irrespective of pollution. Human activities can induce seawater intrusion. However, I'm not sure (a) that this is the pollution that the authors have in mind or (b) that this type of pollution (if you can call it that) is captured well by the GOD vulnerability method.

Response: We consider your valuable opinion; the mentioned coastal areas are already confirmed by various studies of sea water intrusion and man-made pollution activities. In this I explore all of the natural and anthropogenic activities that readers experience through these vulnerable studies. This will help reduce further degradation and guide people in future groundwater management.

Author Response File: Author Response.docx

Reviewer 2 Report

I didn't evaluate any of the figures or tables because I didn't have them. I hope that they exist somewhere and that someone has looked at them.

One major point that I would like to make is in the logic of the article. One issue where things are sometimes blurred is the difference between groundwater vulnerability and groundwater pollution.

(1) Vulnerability - As authors point out in the introduction it is "the potential for contaminants to occur in a given event."

(2) Pollution - This is when pollution has actually occurred in the groundwater.

Just because an area is vulnerable to pollution does not mean that it is polluted. And an area that is not vulnerable can still be polluted. At times the authors seems to conflate these ideas. If they find an area that has high EC and elevated NO3-N, this does not necessarily mean that it is vulnerable. It just means that the vulnerability that was there was been exploited by an actual pollution source.

Another wrinkle in this is the coastal aspect of EC. If some of these areas have high EC, it could just be coastal intrusion into groundwater. Some of this would happen irrespective of pollution. Human activities can induce seawater intrusion. However, I'm not sure (a) that this is the pollution that the authors have in mind or (b) that this type of pollution (if you can call it that) is captured well by the GOD vulnerability method.

Comments for author File: Comments.pdf

Author Response

Reviewer #2:

• This research article focuses on the collection of Microplastic pollutants from ground water and surface water sample. Microscopic and spectroscopic methods used to identify and analyze the microplastics present in the collected sample. The research is relevant and interesting with describing the comparison between worldwide studies in groundwater and surface water MPs. Many research papers have also investigated on microplastics occurrence and distribution in general, so there lack of novelty. On the basis of previous work that has been done in this field, I strongly recommend thorough the manuscript before publication.

Response: The entire manuscript has been modified based on the reviewer suggestion. The results and discussion parts were revised and by adopting a novelty approach.

• Abstract, lines 30-31, Seems kind of obvious to avoid further polluting activities. May be you could talk about how you are making the case in terms of cost-benefit on this recommendation?

Response: Yes Sir, in the guidelines lot of methods are there with low cost for environmental sustainability.

• Intro, lines 40-41, it may be just me, but I wouldn't call these things "problems" inthemselves.Itismorelikethereareproblemsassociatedwiththemorsomenegativeaspects.Itisnotasiftheseare"justproblems". There are good things that come from them after all.

 

Response: I understand your thoughts Sir. Here I highlighted some existing problems for the readers to understand.

 

• Intro, lines 50-54, yes, the GOD method is easiest. But what else is different about this versus DRASTIC and SINTACS? I think it is necessary to tell the reader so that they can evaluate the tradeoffs in this choice you made.

Response: Among the mentioned methods, GOD was selected for this study as it is the easiest to evaluate and interpret based on the hydrogeological parameters of GOD and these all parameters had been already measured by regional government and private water authority, so we can ensure the accuracy and the quality of the data. Therefore, we have selected this methodology.

• Intro line 69, Suggest you identifytheseinfirstusage. I had to go lookup BIS. I normally think of this as Building Information Systems (BIS). Didn't realize you meant Bureau of Indian Standards.

Response: Suggestion Incorporated.

 

• Study area, line 91, Could you be more specific? Do you mean salt production, like sea salt? Or something else?

Response: Suggestion Incorporated.

• Study area, line 95, I don't know how MDPI feels about this, but I get concerned about usingWikipedia as a source. I would suggest you source what Wikipedia sources don’t his since usually Wikipedia just combine so the original and authoritative source materials.

Response: We have removed this sentence. It is not important things in our study.

 

• Study area, line 99, What do you mean by this? Is "heavy water" like deuterated water?

Response: Yes, Suggestion Incorporated.

 

• Study area, lines 106-8, Since this study is about water, it would help the context of these water suppliers if you could say something about what their water sources andtreatmentbeforedeliveryare.

Response: Water sources and rainfall data, etc., for the study area were also discussed sir.

• Materials-methods, line 113-4, I'm not sure what this means exactly. “model stations” Did you createfictitious groundwater stations where you interpolated data? Or do you mean that you tried to selecting real groundwater wells that were about 1km apart from an existing database.

Response: We have selected availability of groundwater wells with an equal distance (1km).

 

GW vulnerability assessment, equation 1andexplanationthereafter, “Is this explanation correct? I think you might mean that this is the value0-1 of the Gc parameter. I wouldn't think you would have a different weight on these three parameters which is location-dependent. To methe weighting (it you do mean weighting) is an indication of the relative importance of each to the vulnerability. Not the value that will determine the GOD Index for a particular location. Did you weight the parameters differently? You might need to provide a simple example calculation to illustrate it clearly”

Response: An example is given in the manuscript. (Section 2.2. Groundwater Vulnerability Assessment)

 

• Line 148, “Not sure if this is what you mean. "Exaggerating" sounds like you are exploding a scale to make it easier to see or (what would beworse) speaking beyond what the data actually tell you”.

Response: Controversy statement revised. Suggestion Incorporated.

 

• Groundwater occurrence (G), line 155, “I think the semi-confined would be> 50% confined and semi-unconfined would be > 50% unconfined. Can you clarify this point? You just never explain how you define these terms”

Response: It is possible when we consider the whole study area, while we could classify individual sampling station as either semi-confined or unconfined.

 

• Overlying aquifer class (O), lines 159-61, “I don't think you are saying this correctly. It is not correct to say that thesediment overlying an aquifer unit tells you "the degree ofcontamination". I think what you probably mean is the RISK of contamination. The only way to know the degree is to actually measure pollution sources or the groundwater for a resultant pollutant”.

Response: Reviewer statement revised. Suggestion Incorporated.

 

• Line 169, “Should change all instance of “depth of the water table” to be depth TO the water table. These are different physical ideas”

Response: Suggestion Incorporated.

• Lines 170-72, “Two points on how you are using the D parameter generally:

Do you use the depth to groundwater table for even a confined aquifer in the same way you use it for an unconfined aquifer? I say this because the fact that an aquifer is confined means that its threat frompollutionis justnotas significantevenifitis very shallow.

It is my opinion that the term "water table" is only used for an unconfined aquifer, where the water level can easily move up or down with water volume. I think that is better to use the general term of" depth to water "or" depth to water level" to allow the idea to speak to both confined and unconfined units”

Response: We respect your comments, as per your suggestion incorporated in revised manuscript.

• Depth to groundwater table (D), lines175-77, “I think these sentences need a little more explanation as well. If you got a water level from a confined aquifer unit, then the level doesn't really tell you the depth to water. It is an indication of the hydraulic head orpotentiometric surface in the confined space. There is some relationship between risk and vulnerability in this, but I'm not sure that it is clear cut. If you used a depth to water measurement in a well in a confined aquifer for the D metric, I would question any vulnerability conclusions you make from this”

Response: Suggestion incorporated,

 

• Section comment, “2.4 Model validation”, “This section is unclear to me. It sounds like you would describe a method to validate this model. But instead you talk about modelvalidation in general. You aren't very clear about how you would validate your model in this case. Later I can see how you are related EC and nitrate concentrations to the idea of vulnerability, but you need to explain our logic better in this section in my opinion”

Response: As per your suggestion this section modified. Suggestion incorporated

 

• Line 243, “Do you just mean concentration when you say “nitrate absorption”? I didn't think you were evaluating partitioning of nitrate between soils and soluble forms. But when you say absorption, it conjures up ideas of how you are evaluating environmental phase partitioning”

Response: Suggestion incorporated.

 

 

• Line 270-1, “This seems too vague to know what you mean here. The knowledge of what authors mean by “a separate legal concept” is hard to know”.

Response: Suggestion incorporated

 

• Line 288-90, “Not sure I agree with thee statement on atmospheric pressure and groundwater being related to pollution. Just because oxygen mixed readily with groundwater doesn't mean that there will be pollution there”

Response: Suggestion incorporated

 

• Line 295, “Discussion of “main source of pollution is use of pesticides”. You didn’t measure or bring up any data on this. I think you need to talk about howsomeone has found pesticides or their residuals in groundwater or surface soils to know that this is an issue. Otherwise, it is just speculation. It is ok to talk about it as speculation. You just need to admit that is what it is”

Response: Suggestion incorporated. Many studies were concluded that the impact on fertilizer usage due to nitrate concentration in groundwater.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

agree with revision