Hydrochemical Characteristics and Evolution of Underground Brine During Mining Process in Luobei Mining Area of Lop Nur, Northwestern China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. In many places, grammatical as well as formatting problems are seen. Please proofread this manuscript.
2. See line no 20 & 21 (However, the content of Mg²⁺ increased gradually during mining.). It is repeated. Please edit it.
3. Figures and tables are to be described in detail.
4. Processes like cation exchange, halite dissolution…..in the findings are known process. Give some new conceptual insights.
5. A comparison study with similar basins or mining areas can be included and this will give uniqueness to the results.
6. If possible, include the relationship between management/environmental consequences mainly on ecological risk or quality of groundwater
7. In some places same explanations, mainly on’ ion behaviour’ are repetitive in the discussion sessions.
8. This study has limited novelty.
9. Quantitative validation should be added.
10. Mixing effects are inferred without tracers or isotopic evidence, weakening the reliability of the conclusions
11. Interpretation of hydrochemical evolution can be discussed i.e., on lithology, recharge zones, aquifer structure etc.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

ABSTRACT

• Line 13-18: This sentence is too long, and the idea is getting lost. Please consider revising it and do not start it with "Based on".
• Line 20-21: There is repetition.

 

INTRODUCTION

• The primary function of an introduction within a research paper is to establish the topic and methodology for readers, with several overarching objectives that aim to pique their interest. For instance, the introduction can be improved if the following are considered and factored into the introduction.
• The authors should
  • Introduce the subject matter and captivate the readers’ attention.
  • Provide a synopsis of previous research or relevant background information.
  • Establish their distinct methodology.
  • Elaborate on their precise research quandary and articulate a clear problem statement.
  • Outline the structure of the paper in its entirety.
• The authors must explain the novelty of their study from the previous studies in the area.

 

STUDY AREA

• Which structures are observed in the lithologies, and how do they control the groundwater flow regime? When you add all these, they can better inform the sources of the ions, especially when the geology is described with a geological map.
• The geology and hydrogeology of the area are not described. Which rocks are dominant in the area? Which type of aquifer is common in the area? What are the borehole depths? What are the aquifer properties (e.g., yield, storativity, transmissivity, etc.)? What are the sources of recharge and discharge of groundwater? This information will help in understanding the source of any contamination whether geogenic or anthropogenic.

 

MATERIALS AND METHODS

• Estimation protocols of different cations and anions were not described. Instrumental conditions for analysis were not placed. No quality control and quality assurance study were placed in favour of the reliability of the generated data. Nothing has been told about SRM, duplicate sampling, duplicate analysis, recovery of spiked sample, inter-laboratory testing, standardization, blank analysis etc.
• Why didn’t the authors measure the physical parameters like pH, EC, and TDS in the field? Only TDS is reported, why?
• The authors should plot Piper and Gibbs diagrams, which can highlight the degree of water-rock interaction.

 

RESULTS AND DISCUSSION

• Figure 1: Integrate the Digital Elevation Model (DEM) to assess whether slope variations affect brine formation.
• If data on the depth of the water table in each sampling well is available, prepare a depth contour map and integrate it with the 1-Grid vector groundwater flow map. This will help to interpret groundwater flow patterns and subsurface saline/freshwater dynamics.
• Consider plotting an Hydrochemical Facies Evolution Diagram (HFED) to illustrate the dynamics between saline and freshwater in the study area. Moreover, your EC and TDS values are high, which may point to some saline water intrusion.
• Authors have shown various causes of salinity; they should draw a conceptual model depicting salinity, its causes, and its mechanism for the study area.
• Interpretations should be linked with the geology of the area, especially with the mineralogical composition, because not all ions could be derived from anthropogenic sources.

 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors in the current study investigated the long-term impact of brine mining on the groundwater chemistry in the Luobei Depression, focusing on the significant increase in dissolved magnesium between 2006 and 2023. Using three sampling stages (2006, 2019, 2023) comprising of 207 brine samples, they applied ionic ratio analysis and PHREEQC based saturation index modelling to track chemical evolution. The results reveal a deepening cone of depression and a notable a significant rise in Mg²⁺ concentrations. The study highlights the geochemical risks of continued extraction, warning of declining brine quality.

 This study uses real world experimental data to show how the  long term brine extraction alters groundwater chemistry, making it a good candidate for publication in the Water Journal.

Suggestions for improvement:

1) Lines 20-21: “However … during mining.” Repetition, remove redundant phrase.

2) Line 73: “Based on the hydro chemical… underground phreatic…” Explain a bit earlier what are the 3 phases mentioned here. Of course phases are mentioned as “stages” in the abstract but they need to be defined in the introduction as well.

 3) Lines 183-196: Specify in the analysis at the end of section 3.1 the spatial interpolation method that was used to produce the surface plots spatial distribution of Mg²⁺ , in Figure 3 (spline, kriging etc.) and possibly describe any measures taken to account for the different sample number that were gathered in the distinct three time periods (stage2 had 23 samples and stage3 had 116 samples).

4) Lines 236-238: “Furthermore … of leached brine.” The authors should try to rewrite this sentence and make it clearer.

5) Lines 308-309: A reference is required for Equations 2-4.

 6) Overall the authors need to clearer explain in the discussion,  what the side effects of unsupervised and extended mining are. Of course they described the changes in chemistry regarding several ions but why is this important for the underground water quality? Will the increase of Mg concentration increase the costs of the mining process or will make the underground water aquifer unusable for irrigation or other purposes. Are there any hard thresholds that are crossed in the elevated ion concentrations? The current research doesn’t seem to have a justified reason for being carried out.

 7) A good proof read is required for the manuscript since several spaces between words are missing from the manuscript.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors incorporated all the corrections, and this manuscript can be accepted. 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have satisfactorily addressed all my previous comments, and thus, the manuscript can now be accepted for publication in its current form.