Human activities of mining have profound impacts on water quality at local to regional scales. In this paper, the attention is paid to mapping mining-affected water pollution in China. It is achieved through the compilation of a number of publicly available surface water and groundwater datasets. In general, the paper can be valuable.

There are three major comments for further improvement of the paper:

(1) There are various types of mining activities related to the exploitation of natural resources. Underlying the activities are the spatial distribution of natural resources. For example, metals and minerals are of different distributions in China and as a result, the respective mining activities are in different places and of varying intensity. It seems that the paper does not present the big picture of spatial distributions of natural resources. Accordingly, the plot in Figure 1 is patchy, rather than comprehensive. Therefore, the authors may want to explicitly illustrate spatial distributions of natural resources as a big context of the literature survey work for the paper.

(2) It is known that the mining of coal has a considerable impact on water quality, especially in West China. On the other hand, there is a lack of in-depth investigation of coal mining. Given the importance of coal mining and the existence of extensive studies, the authors may want to present a detailed analysis.

References:

Yajun, S.U.N., Ge, C.H.E.N., Zhimin, X.U., Huiqing, Y., Yuzhuo, Z., Lijie, Z., Xin, W., Chenghang, Z. and Jieming, Z., 2020. Research progress of water environment, treatment and utilization in coal mining areas of China. Journal of China Coal Society, 45(1), pp.304-316.

Zhang, X., Li, X. and Gao, X., 2016. Hydrochemistry and coal mining activity induced karst water quality degradation in the Niangziguan karst water system, China. Environmental Science and Pollution Research, 23, pp.6286-6299.

Qu, S., Liang, X., Liao, F., Mao, H., Xiao, B., Duan, L., Shi, Z., Wang, G. and Yu, R., 2023. Geochemical fingerprint and spatial pattern of mine water quality in the Shaanxi-Inner Mongolia Coal Mine Base, Northwest China. Science of The Total Environment, 854, p.158812.

(3) There are serious concerns on heavy metal pollution in recent years. Previously, there have been a few review papers. What new insights (findings) does this paper make?

References:

Cheng, S., 2003. Heavy metal pollution in China: origin, pattern and control. Environmental science and pollution research, 10, pp.192-198.

He, B., Yun, Z., Shi, J. and Jiang, G., 2013. Research progress of heavy metal pollution in China: Sources, analytical methods, status, and toxicity. Chinese Science Bulletin, 58, pp.134-140.

Hu, H., Jin, Q. and Kavan, P., 2014. A study of heavy metal pollution in China: Current status, pollution-control policies and countermeasures. Sustainability, 6(9), pp.5820-5838.

The manuscript aims to provide a comprehensive assessment of mining-affected water pollution across China by compiling a large dataset (8433 water samples from 298 mines). The study evaluates spatial patterns, assesses both carcinogenic and non-carcinogenic risks to human health, and discusses management implications for both coal and metal mining areas. While the work is well supported by extensive data and robust methodologies, questions remain regarding the novelty of the contribution, as the manuscript does not clearly delineate how its findings significantly extend beyond previous studies.

Novelty and Original Contribution

Strengths: The study assembles a large national dataset and applies risk assessment models to evaluate health impacts, which is commendable. The spatial mapping of contamination hotspots and risk distribution provides valuable insights for policy-making.

Concerns: One key issue is that the manuscript does not sufficiently highlight what is new compared to earlier studies. Although the scale of the data collection is impressive, the paper lacks a clear statement of its novel contributions relative to existing literature. The authors could enhance the manuscript by emphasizing unique aspects—such as new methodological approaches, previously unreported spatial trends, or innovative risk assessment strategies—that set this work apart.

Methodological Rigor and Data Quality

Strengths: The methodology is generally robust, with clear criteria for data quality control and appropriate use of standard risk assessment models (e.g., those provided by the US EPA). The division of water samples (acidic vs. neutral/alkaline) and the differentiation between coal and metal mines are well executed.

Suggestions: To further strengthen the paper, the authors should elaborate on how potential biases (e.g., variations in sample density among regions) were addressed. Additionally, more detailed statistical tests comparing water quality parameters between different mining types (such as using non-parametric tests) could provide further evidence for the observed differences.

Presentation and Interpretation of Results

Strengths: The results are logically presented, starting from the basic water quality parameters, moving on to spatial distribution patterns, and culminating in detailed risk assessments for different populations. Figures (e.g., maps and boxplots) support the textual description and help visualize the trends effectively.

Suggestions: Although the numerical details are extensive, the manuscript may benefit from a more concise presentation. For example, summarizing key quantitative findings in a table could improve clarity. Additionally, while the spatial patterns are well described, a deeper discussion on the underlying geochemical or environmental processes that cause these trends would better contextualize the results.

Structure and Coherence of the Argument

Strengths: The manuscript follows a conventional structure (introduction, methodology, results, discussion, conclusion) that makes it easy to follow. The discussion ties the findings back to the broader context of water pollution management.

Suggestions: The transition between sections—especially from the results to the discussion—could be smoother. Explicitly linking how each result addresses the stated objectives would reinforce the coherence of the argument. Also, highlighting the novelty and practical implications of the work in the conclusion would help reinforce the manuscript’s contribution.

Figures, Tables, and Visual Aids

Strengths: Visual aids are generally clear and provide a good overview of the data distribution and risk maps. The integration of detailed figures (such as spatial distribution maps and risk assessment graphs) adds significant value to the manuscript.

Suggestions: Ensure that all figures have clear legends and consistent formatting. It might be beneficial to include a summary table that aggregates the key findings (e.g., median values of critical parameters across different mine types) to enhance readability.

Language and Style

Strengths: The manuscript is written in clear, professional English with an appropriate academic tone. Technical terms are defined upon first use, and the text is generally free of major grammatical errors.

Suggestions: A few sentences could be simplified to improve readability. In particular, some complex sentences in the introduction and discussion might be broken into shorter, more digestible statements. Maintaining consistency in terminology (for instance, ensuring that terms like “differentiated management” are clearly defined) will also help in reinforcing the manuscript’s clarity.

Conclusion

The manuscript presents an extensive dataset and a rigorous analysis of mining-affected water pollution in China, offering useful insights for environmental management and policy-making. However, the work would benefit from a more explicit discussion of its novelty compared to previous studies. Clarifying and emphasizing the unique contributions—whether in data scale, methodological advancements, or new insights into spatial and health risk patterns—would significantly strengthen the paper. With these revisions, the manuscript could represent a valuable addition to the field of environmental hydrology.

The study delivers a thorough and spatially explicit examination of mining-induced water pollution and associated health risks across China, utilizing an extensive dataset comprising 8,433 samples. The differentiation between coal and metal mines, along with the identification of southern China as a pollution hotspot, provides valuable insights for region-specific policy formulation. Below are several constructive suggestions for refining the manuscript:  

1. While the spatial heterogeneity of pollution is convincingly presented, the underlying mechanisms driving the pronounced contamination in southern China (e.g., geological factors, mining practices, or climatic conditions) warrant further elaboration. Incorporating a brief discussion that connects regional geochemistry or historical mining activities to observed pollution patterns would enhance the robustness of the analysis.  

2. The health risk assessment (e.g., 51.52% carcinogenic risk for adults) raises significant concerns but lacks sufficient methodological detail. Please specify the exposure parameters employed (e.g., ingestion rates, body weight assumptions) and the toxicity thresholds applied. Additionally, clarify whether the identified risks stem from specific contaminants (e.g., arsenic, cadmium) or synergistic interactions among multiple pollutants.  

3. The temporal dimension of water sampling remains ambiguous. Were the samples collected across different seasons or years? Temporal variability in water chemistry (e.g., the influence of monsoon events on metal mobility) could significantly affect risk estimates and merits further exploration in the discussion section.