Heavy Metal Source Apportionment, Environmental Capacity, and Health Risk Assessment in Agricultural Soils of a Rice-Growing Watershed in Eastern China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This study highlights the importance of integrated and multidisciplinary approaches in assessing metal contamination in an agricultural watershed. By combining techniques such as geostatistics, positive matrix factorization (PMF), self-organizing map (SOM) analysis, and health risk assessment, the work provides a comprehensive understanding of the spatial distribution, contamination sources, soil environmental capacity, and associated human health risks. The results reveal not only localized overloads of potentially toxic metals, but also significant health risks to children, primarily through indirect oral exposure. Thus, this study has strong potential to contribute meaningfully to the development of more effective public policies that take into account the synergistic effects of natural and anthropogenic sources, and also emphasizes the urgency of preventive measures aimed at protecting vulnerable populations—especially children—in rural and agricultural areas. However, some observations are relevant for improving the quality of the manuscript.

I address the following points:

• Given the importance of the topic "heavy metal": The term "heavy metal" is outdated and imprecise. It's preferable to use terms like metal, trace element, or toxic metal, depending on the context. Please refer to the following paper:

Duffus, J. H. "Heavy metals" — a meaningless term? (IUPAC Technical Report). Pure and Applied Chemistry, 2002, 74(5), 793–807. https://doi.org/10.1351/pac200274050793

• In the Results and Discussion section, it is recommended that tables and figures be explicitly referenced when mentioned, to facilitate interpretation by the reader.
• I understand that the information regarding health risk assessment for adults and children came from another study [47]. Therefore, I ask: can the information presented in [47]—which was from Laiyang County—be used for Tancheng County, both located in Shandong Province? This is because it appears that the information was sought in the literature.
• The authors should revise the conclusions, as some information might be better presented in the Results and Discussion Reading the conclusion as it stands, the practical significance of the work may not be clear. In this regard, consider creating a subsection in the Results and Discussion or adding to the conclusions information about the practical and scientific importance of the study—even if it is regionally focused—highlighting the contribution of the work to society; implications for environmental management and public health; and the importance of specific management strategies to mitigate contamination, especially in more vulnerable areas (e.g., cultivated lands, riverbanks).

Specific comments:

• L. 43: What is meant by soil health or healthy soils? The authors should provide a clear definition of this term.
• L. 90: A conjunction appears to be missing to connect the two sentences smoothly.
• L. 99: The abbreviation SOM should be spelled out at first mention.
• L. 139: Figure 1 does not appear to clearly show current land use.
• L. 157: To what extent were the procedures exceeded? Is this a critique of the Geochemical Evaluation Standard for Land Quality (DZ/T 0295-2016), or a way to emphasize how rigorously the authors applied the procedures?
• L. 244–247: Align the equation numbers to the right, consistent with the other equations in the text.
• L. 296, Table 1: Add ‘–’ for cells where information is not available.
• L. 311–312: Is it metal concentration or metal content? Please standardize terminology throughout the text.
• Table 3: Double-check the values presented.
• L. 344–345: Is the information actually shown in Figure 2(a)?
• L. 349: Why is this statement cited? Isn’t the information being presented a result of this study?
• L. 363–366: Reference the relevant figure.
• Figure 4: Is an EF of 20 accurate? Please confirm consistency between lines L.177–181 and the data shown in Figure 4.
• L. 371–374: The text states “slightly enriched,” but L.177 defines EF < 0.5 as “No enrichment (dominantly lithogenic sources).” Please clarify.
• Authors should check whether the introductory information at the beginning of certain Results and Discussion sub-sections should instead be included in the Materials and Methods section—e.g., Section 3.2.2 (L.384–391).
• Standardize all figure and table captions—some start with lowercase letters, others with capitalized words.
• Improve transitions between sentences to enhance the logical flow—e.g., L.408–409.
• L. 523: The first word of the section title should start with a capital letter.
• Table 5: Should the label refer to environmental capacity indices or levels? Or perhaps indexes?
• References: Standardize formatting. There are inconsistencies.
  Example issues:
  • Reference [27] uses capitalized words for each title word.
  • Reference [58] lacks a comma between the surname and initials, and uses commas instead of semicolons to separate authors, unlike other references.
  • Reference [59] uses a period after the first author’s surname (Cheng. ) instead of a comma.

 

Author Response

Dear Reviewer,
Thank you very much for taking the time to review our manuscript. We appreciate your clear and detailed feedback and hope that our responses have adequately addressed all your concerns. In the attached document (Response to Reviewer 1 Comments), we have provided point-by-point responses to each of your comments. For clarity, your original comments are reproduced in italics, followed by our responses in bold. For your convenience, all modifications in the revised manuscript have been highlighted in green.

Sincerely,

The Authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Minor revision~
Strengths include dense sampling, combined PMF and SOM analysis, and spatially explicit risk mapping, while weaknesses include incomplete PMF diagnostics, several parameter and table inconsistencies, and limited exposure pathways and uncertainty analysis. 
(1)Page 1, Line 19 to 37 Clarify the novel contribution relative to recent regional studies and explicitly state the primary hypothesis being tested, then align claims in the abstract with the scope of the data and analyses.
(2)Page 2, Line 72 to 83 The motivation notes that capacity and risk are often disconnected from source apportionment, please state in Methods how source specific information is quantitatively propagated into the capacity and risk calculations or clarify that linkage remains qualitative.
(3)Page 5, Line 137 to 164 Provide the batch level QA QC summary including counts of duplicates and CRMs per element, spike recoveries, and handling of censored data below MDL, and state the number of measurements below MDL for each metal.
(4)Page 6, Line 171 to 181 Report the exact Fe to Fe2O3 conversion factor and the background Fe basis used in EF calculations, and justify the choice of Fe given potential anthropogenic inputs in paddy soils, consider sensitivity using Al or Ti as a check.
(5)Page 7, Line 207 to 209 Specify the value of the relative standard deviation delta used for PMF uncertainties, detail treatment of values at or below MDL including substitution rules, and provide element specific S N classifications.
(6)Page 15, Line 462 to 471 For SOM, report training settings including data scaling, map topology and size selection rationale, learning rate schedule, neighborhood function, epochs, and the internal validation metrics beyond FQE and FTE.
(7)Page 18, Line 523 to 551 Define how PImin is computed from single metal Pi values? state the classification thresholds applied and their basis, and include a sensitivity analysis showing how PI and PImin rankings change with pH class selection?
(8)Page 22, Line 618 to 629 The TCR exceedance statement for children requires uncertainty bounds and a map legend with numeric class thresholds, add percentile maps or confidence surfaces and clarify the decision threshold used for exceedance counting.
(9)Page 7, Line 283 to 295 Justify excluding food chain ingestion from the risk model in an agricultural setting or add a screening level crop uptake pathway using locally relevant transfer factors to bound total exposure.
(10)Page 11, Line 341 to 356 The geochemical correlation discussion attributes patterns to pH and soil components, add quantitative support using partial correlations or regression controlling for pH and texture and report effect sizes.
(11)Page 13, Line 402 to 417 The attribution of Factor 1 to coal combustion would be strengthened by including an auxiliary tracer such as Se or by comparing to published Hg source profiles, add a simple receptor model check or isotopic literature support.

Author Response

Dear Reviewer,
Thank you very much for taking the time to review our manuscript. We appreciate your clear and detailed feedback and hope that our responses have adequately addressed all your concerns. In the attached document (Response to Reviewer 2 Comments), we have provided point-by-point responses to each of your comments. For clarity, your original comments are reproduced in italics, followed by our responses in bold. For your convenience, all modifications in the revised manuscript have been highlighted in yellow.

Sincerely,

The Authors

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

My recommendations refer to:

-clarity of figures 1, 2, 4, and 8b

-It should be specified what is the fertilization method and the fertilizers used in the respective area to fertilize the rice crop, as well as the phytosanitary treatments performed in order to be able to understand the source of heavy metals with a decidual effect, because the article only makes a vague reference to this aspect.

-It should be specified and described more carefully that the source of heavy metals is residual rather than coming from point or widespread pollution.

-also, some initial soil analyses from the studied area on uncultivated land, with spontaneous vegetation and not subject to any source of pollution, should have been presented, in order to make a clearer comparison with the results obtained.

-The results and discussions section should be separated, so the explanations related to the results obtained would be clearer.

-It would be desirable to explain what the solutions are for reducing pollution in that area and implicitly the risks to human health.

-some bibliographic titles are old, if they are not of reference in this field they should be replaced: 14, 15, 16, 21, 22, 25, 26, 31, 39, 51, 55.

-The bibliography numbering is incorrect, it jumps from 16 to 20, meaning titles 17, 18, 19 are not cited in the text.

-also bibliographic title 47 must be corrected.

-bibliographic titles 49, 50, 51 are unmarked in the text.

-bibliographic title 52 from table 3 must be modified or the table should be included alswhere in order to keep the correct numbering in the article text.

Author Response

Dear Reviewer,
Thank you very much for taking the time to review our manuscript. We appreciate your clear and detailed feedback and hope that our responses have adequately addressed all your concerns. In the attached document (Response to Reviewer 3 Comments), we have provided point-by-point responses to each of your comments. For clarity, your original comments are reproduced in italics, followed by our responses in bold. For your convenience, all modifications in the revised manuscript have been highlighted in blue.

Sincerely,

The Authors

Author Response File: Author Response.pdf