Review Reports

Sr. No

Comments by Reviewer

Reply/response

General Comments

The study entitled “Risk Assessment of Heavy Metals in Groundwater for a Managed Aquifer Recharge Project” investigates the quality of water collected from different sampling points in Pakistan to support baseline data for a Managed Aquifer Recharge (MAR) project. Water suitability for drinking or irrigation purposes was assessed using determination of heavy metals in water samples. The study provides insight into water chemical condition through an integrated assessment combining analytical measurements, statistical analysis, and geospatial mapping, fulfilling its primary aim, to provide valuable baseline data for MAR planning in Pakistan.

Noted with Thanks

General

The subject is interesting, though not innovative. To my view, the manuscript must undergo major revision before considering publication. Major drawbacks are repetition and redundancy throughout the manuscript with many deficiencies in methodology, presentation of results and discussion. The text should be revised to include only relevant and conclusive data; while justifications should also be provided (i.e. number of sampling campaigns, samples, analysis of results etc).

Thanks for the valuable comments. The subject is although general, it is innovative for the MAR project in Pakistan.

This MAR project of first of its nature and needed proper investigations for successful implementation. Manuscript has been revised and amended accordingly- shown in track changes.

1.       

In the Introduction section, please briefly describe the context of water quality standards related to irrigation water in Pakistan, to introduce the reader to requirements/thresholds for exploiting water sources.

Needful done in tracked changes at line Nos: 168-170

2.       

Lines 75-88: Although metals such as As and Pb are indeed major public health threats, other contaminants, including microbial pathogens (E. coli, coliform bacteria), nitrates, pesticide residues etc, contribute significantly to disease burden. This is overlooked in the Introduction part but should be included and discussed properly.

Needful done in the text lines 95-99. Although, these are very important parameters [pointed out by the honorable reviewer, these aspects were beyond the scope of present study.

3.       

In section 2.1 please provide the source of data for compiling Figs 2 & 3.

Ref for these figures is the PhD work of first author. However both figures have been deleted keeping in view the general comments by the learned reviewer

4.       

Vehari district is quite large with significant agricultural activity and almost 20000 tubewells. Please explain and provide justifications about sampling strategy. Why is the number of samples and sampling points adequate? How was the sampling period selected? Please provide more insights. Was grab sampling the only method? Please check sampling conditions & sample preservation for chromium analysis and refer them accordingly.

The research was a component of PhD research of first author. Twenty groundwater samples were proposed approximately uniformly distributed at a grid of about 8.5 x 8.5 km. Keeping in view the time limits, financial resources to meet the analysis costs, and Covid restrictions, this sampling was considered adequate.  Explanation added in the manuscript at lines 183-185 with proper citation.   

5.       

Sampling was restricted to a single campaign (May–June 2021), overlooking seasonal variability that strongly influences heavy metal mobilization, especially under monsoonal recharge. This limitation should be explicitly highlighted in the text, with reference to the specific constraints it produces for interpreting water quality and health outcomes.

Rightly pointed out. This study was limited for one time sampling as explained above at Sr No 4. Could not be repeated due to Covid and time limit for PhD research. This has been explained in the text of manuscript at lines 183-185

6.       

Figure 4 should be amended: it would be clearer to discriminate between end-use pathways (irrigation and drinking) and analytical steps (general/descriptive analysis), since grouping them on the same level implies equivalence, i.e. first level could be the analysis (descriptives), second level water uses etc.

Correctly pointed out by the honorable reviewer a deep point, but we think the figure serves the purpose for general (some time less technical) readers.

7.       

Lines 250-253. The reported ranking of heavy metals by mean concentration (Al > Mn > Ba > As > Zn > Mo > Cu > Cr > Ni > Se > Pb > Co > Cd) is misleading in terms of interpretation. Concentration values of different elements are not directly comparable, since each metal has distinct geochemical behavior, natural background levels and toxicological significance. Please re-write this part of the manuscript.

Thanks for raising this very important conceptual correction. Needful done in the text at line 267-270 tracked  in the manuscript.

8.       

Figure 5 has many weaknesses and should be amended: it is almost impossible to distinguish individual elements due to almost identical colors and y-axis scaling (i.e second y-axis should be used). In addition, the use of line plots to demonstrate metals concentrations across different sampling locations is wrong. Lines imply continuity, which does not exist here, since each site (HM1–HM23) is a discrete and independent sampling point, not part of a continuous dataset. The correct approach would be to use bar charts, boxplots (better to follow exceedances etc), or scatter plots.

Needful done as suggested please. Shown in bar charts

9.       

Table 1 shows the results of heavy metals analysis using two digits. How many significant digits are there? Please explain and amend accordingly.

Generally 2 digits are significant. Table corrected accordingly

10.    

Figure 6 should be deleted, as it lacks scientific validity and interpretive value. Plotting the “total load of heavy metals” as a single aggregated value per sampling site is misleading. Please explain in detail or delete.

Figure deleted as suggested 

11.    

Pearson correlation is applied to obtained data; however, no justification is provided about methodological issues (normal distribution of data etc). For instance, why Pearson and not Spearman's rank correlation? Were all requirements satisfied? Please explain and mend accordingly.

Observation by the honorable reviewer is highly appreciated and acknowledged. Pearson’s correlation coefficient was applied with the understanding that there is small variability in the values of different parameters. However, it is acknowledged that Spearman’s rank correlation can provide better insights for the variable not exhibiting normality. Explanation added in text please see lines 121-123 in tracked text

12.    

Figures 7 & 8 should be delivered in better quality and explanations should also be provided about how coloring was made and what is the meaning.

These are the GIS software (ArcMap 10.6) generated figures and color are adjusted by the software itself as explained in the legend. 

13.    

Figures 9-13 should be merged and reduced by number in a way that only significant and conclusive info is presented.

Needful done

14.    

Table 7 should be revised to contain statistical features of values. Please delete ‘fit’ and have it as a note. Presentation of single values cannot lead to conclusions. Same for Table 8 & 10.

Table 7 has been deleted to reduce the overall size of paper. There are no statistical parameters as one single sample has been taken for drain, river and canal. Same done for table 8 and 10

15.    

‘Risk Assessment’ section: Repetition should be deleted, as well as over generalizations. For example, the first paragraph should be included in the ‘introduction’ section and not in the discussion section. The sentence ‘Heavy metals and some trace elements in irrigation water cause soil contamination 608 and are significant for irrigation water quality because of properties like biodegradation 609 and thermo-degradation resistance (Antoniadis et al., 2019)’ is repeated twice. The text frequently is not clear: i.e., Mn is reported as mostly below guidelines, yet the discussion emphasizes Mn-related risks without making clear that exceedances were rare. In general, the discussion section refers to toxicity and not to discussion about the findings of the present study. Although numerous references are cited, they are listed sequentially rather than critically compared or compared with results of the present study. The discussion is superficial and should be revised thoroughly. For example, the text cites Khalid et al. (2020) and Murtaza et al. (2020) showing poor drinking water quality in Vehari, but it does not discuss these findings with the current study’s irrigation-focused results. Moreover, the section moves abruptly between irrigation suitability and drinking water hazards without clear transition. The text confuses micronutrients (Zn, Cu, Mn) with toxic heavy metals (Pb, Cd, As) without carefully distinguishing between their roles. The claim that “cyan (CN)” is a trace element is incorrect; cyanide is a compound, not a trace metal. Please revise the text meticulously.

Thanks for providing critical analysis and comments, these have helped a lot in improving the quality of manuscript.

Removed duplicated introductory sentences and moved general background to the Introduction.

Clarified that Mn exceedances were rare (used your numbers).

Explicitly separated micronutrients (Zn, Cu, Mn) from toxic heavy metals (Pb, Cd, As) and adjusted language accordingly.

Corrected the error: removed “cyan (CN) as a trace element”

Added a direct comparison with Khalid et al. (2020) and Murtaza et al. (2020), clarifying differences in scope (drinking water vs irrigation) and how results relate.