PONE-D-23-41961Short Communication: Evaluating the impacts of microplastics on agricultural soil physicochemical properties and toxic metal availability: an emerging concern for sustainable agriculturePLOS ONE

Dear Dr. Nice,

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Academic Editor

PLOS ONE

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Reviewers' comments:

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Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: N/A

Reviewer #2: No

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Reviewer #1: No

Reviewer #2: No

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Reviewer #1: Yes

Reviewer #2: No

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Dear authors

Abstract

The abstract effectively summarizes the main points of the study. However, some sentences could be further clarified and condensed for brevity without losing important information.

Provide more specific details about the methods used in the study, such as the experimental setup for soil incubation studies and the analytical techniques employed to measure soil characteristics and heavy metal availability.

Instead of listing all the changes in soil characteristics and heavy metal availability in a single sentence, consider breaking down the findings into separate sentences or bullet points to improve readability and comprehension.

Include specific quantitative results or ranges, such as percentage changes in soil properties and heavy metal concentrations, to provide readers with a clearer understanding of the magnitude of the observed effects.

Expand on the implications of the findings for soil health and environmental management. Discuss how the observed changes in soil properties and heavy metal availability due to MPs contamination might impact ecosystem functions and human health.

Ensure consistency in language use and grammar throughout the abstract. For example, check for proper tense usage and grammatical structure in each sentence.

The selected keywords effectively highlight the main topics of the study. However, consider adding additional keywords related to soil pollution, environmental impact assessment, or plastic pollution to improve the discoverability of the manuscript.

Provide a concise summary of the key conclusions drawn from the study's findings, emphasizing the significance of the research and potential avenues for future investigation.

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Introduction

The Introduction effectively introduces the topic of microplastic pollution in soil and highlights its significance for soil health and ecosystem functioning. The structure of the Introduction is logical, with clear transitions between different aspects of the topic.

The Introduction provides a thorough review of relevant literature, citing key studies to support the discussion on the sources, distribution, and potential impacts of microplastics in soil ecosystems. However, ensure that all cited studies are accurately referenced and consider including more recent references to reflect the latest research in the field.

The objectives of the study are clearly stated, indicating the focus on assessing the impact of MPs on soil properties and heavy metal availability in both contaminated and uncontaminated agricultural soils. Consider briefly mentioning the specific MPs types and doses tested in the study to provide additional context for readers.

The Introduction effectively identifies knowledge gaps in the current understanding of microplastic pollution in terrestrial environments, emphasizing the need for research on MPs in agricultural soils. This sets the stage for the study's contribution to addressing this gap.

Ensure smooth transitions between paragraphs and sections to maintain the flow of the Introduction. Consider revising sentence structures for improved clarity and readability, avoiding overly complex or convoluted phrasing.

Conclude the Introduction by emphasizing the importance of the study's findings for informing soil management practices, environmental policy, and future research directions in the field of microplastic pollution in terrestrial ecosystems.

The review of intermittent irrigation techniques is good but citing key studies would strengthen the evaluation (e.g. "Recent work like doi.org/10.1002/ep.14301, https://doi.org/10.1080/15320383.2023.2258413, https://doi.org/10.1080/15226514.2023.2250464, doi.org/10.1002/ep.14230, doi.org/10.1002/ep.14217, https://doi.org/10.1007/s10333-022-00915-5

Materials and Methods" section needs significant revisions for clarity and completeness:

The section effectively outlines the steps involved in microplastic preparation, soil preparation, experimental setup, and analysis methods. However, some sentences are lengthy and complex, which may affect readability. Consider breaking down long sentences into shorter ones for clarity.

The description of microplastic preparation is clear and provides sufficient detail on the sources of different types of microplastics and the cleaning process. Ensure consistency in terminology (e.g., "plastics items" vs. "plastic products") for clarity.

The description of soil collection, preparation, and experimental setup is well-detailed, including information on soil properties and treatment groups. Consider providing more information on the rationale for choosing specific microplastic types and doses for the experiment.

The methods for analyzing soil properties, including pH, nutrient content, organic carbon, and heavy metals, are described in sufficient detail. However, consider providing more context or references for the analytical techniques used, particularly for readers who may be less familiar with these methods.

The section briefly mentions the statistical software used for analysis but lacks detail on specific statistical tests or procedures employed. Consider elaborating on the statistical methods used to analyze the data and determine significance.

Reference to Figure S1 is made but not included in the text. Ensure that all figures and tables mentioned in the text are properly labeled and referenced.

Ensure consistency in formatting, units of measurement, and terminology throughout the section to avoid confusion. Double-check numerical values and units for accuracy.

Provide information on replicates and controls to ensure the reproducibility of the experimental results. Clarify how triplicate experiments were conducted and averaged.

Results and Discussion

The section is well-organized and presents the results in a systematic manner. However, it could benefit from clearer subheadings to delineate different aspects of the results (e.g., soil physicochemical properties, soil nutrients availability, soil metals availability).

The interpretation of the results is generally clear, but consider providing more detailed explanations for some observations. For example, explain why certain types of microplastics (MPs) have different effects on soil pH, EC, and nutrient availability.

The section references previous studies to support the findings, which strengthens the discussion. However, provide more direct comparisons with previous research to highlight similarities or differences in results.

The figures and tables effectively complement the text and provide visual representations of the data. Ensure that all figures mentioned in the text are included, and provide clear captions for each figure/table to facilitate understanding.

Ensure consistency in reporting units of measurement and formatting of results throughout the section. Double-check numerical values and units for accuracy.

While the section presents results followed by discussions, aim for a more integrated approach where results are discussed in tandem with their implications. This will help readers understand the significance of the findings more effectively.

Ensure that all references cited in the text are included in the reference list, and vice versa. Check the formatting of citations to ensure consistency with the journal's style guidelines.

Provide more context for the findings within the broader scope of environmental science and soil research. Discuss the potential implications of the results for soil health, ecosystem functioning, and agricultural productivity.

While the section provides numerical data on soil properties and metal availability, consider including statistical analyses to support the significance of the findings. This could involve ANOVA, t-tests, or other relevant statistical tests to compare differences between treatment groups.

Address any limitations or potential sources of bias in the study design or methodology. Acknowledging limitations demonstrates transparency and helps readers interpret the results accurately.

Discuss the practical implications of the findings for environmental management or agricultural practices. Consider how the results could inform policies aimed at mitigating the impact of microplastics on soil health and metal contamination.

Suggest potential avenues for future research based on the study findings. Identify unanswered questions or areas requiring further investigation to advance understanding in this field.

Ensure that the language used is concise, precise, and appropriate for the target audience. Avoid overly technical jargon where possible and strive for clarity in conveying complex concepts.

Conclusions

Begin by succinctly summarizing the main findings of the study, emphasizing the significant changes observed in soil properties and heavy metal availability due to microplastic contamination.

Discuss the implications of the findings for soil health, environmental quality, and agricultural productivity. Emphasize the potential risks posed by microplastics and their impact on soil fertility and metal bioavailability.

Acknowledge the variation in effects observed among different types of microplastics and at different doses. Highlighting these variations adds depth to the conclusions and helps contextualize the results.

Suggest specific areas for future research, such as investigating the mechanisms underlying the interaction between microplastics and heavy metals, conducting plant experiments to assess their combined effects, and exploring the long-term implications for soil ecosystems.

Conclude with a call for action, emphasizing the importance of addressing microplastic pollution in soil and advocating for further research and policy initiatives to mitigate its impact on environmental and human health.

Best regards,

Reviewer #2: General comments:

In the manuscript “PONE-D-23-41961,” the authors evaluated the possible impact of microplastics (MPs) on soil physicochemical and chemical properties and toxic metals availability in contaminated and uncontaminated agricultural soils. The topic is relevant and timely. However, the study has important limitations that justify my recommendation against publication in a renowned journal such as PLOS ONE. The following items can help authors improve the manuscript for future publication.

Specific comments/suggestions:

1. Title – replace “physicochemical properties” >>> “physicochemical and chemical properties”

2. L21: replace “doses” >>> “concentrations”. Adjust this throughout the manuscript.

3. L23: define the acronyms or abbreviations presented in the abstract.

4. L60: replace “Ph” >>> “pH”.

5. L70: replace “MHs” >>> “HMs.” Check this throughout the manuscript.

6. Microplastics and MPs - When you first use a word that can be abbreviated, spell it out in full and show the abbreviation/acronym in parentheses immediately afterward. After that, you can stick to using the abbreviation/acronym.

7. L81-82: The justification for conducting the study should be improved. The absence of studies on a given topic does not constitute a good scientific justification. The goal of the first step of the manuscript is to get your audience's attention, to show them why your research matters, and to make them want to know more about your research. This step involves providing the reader with critical background or contextual information that introduces the topic area and indicates why the research is essential. Why is this research important? What real-life or everyday problem, issue, question, or context does the research relate to? What is the research ultimately trying to achieve? How can I grab the reader’s attention and concern? How can I state the problem or context of the research in terms that most people can report to? What possible negative repercussions would result from not solving this problem? What benefit does the research promise? How the intended outcomes of the study could be used to advance knowledge? These questions must be answered in the introduction of the manuscript! Furthermore, the hypotheses tested should be clearly presented at the end of the introduction.

8. L89-90: Were the plastic products new or aged? Clarify in the text.

9. L91-92: Authors must justify the choice of polymers tested. Although this is obvious, it must be clarified, considering that several other synthetic polymers could have been chosen.

10. L100-102: Authors must present the classification of the soil used. I recommend authors use the World Reference Base (WRB), i.e., the international standard for soil classification systems endorsed by the International Union of Soil Sciences.

11. L106: what is the reason for these seven days?

12. L113: Authors must clearly justify the choice of concentrations tested. The results of concentration-response experiments must always be interpreted in light of environmental concentrations.

13. L118: correct incorrect character in a sentence.

14. L116: What was the criterion for choosing the determined humidity? Throughout the 90 days of incubation, do the authors ensure this humidity was maintained unchanged? I'm not sure if the “paraffin” seal completely prevented evaporation. Clarify this in the text.

15. Were plastic cups used to conduct the experiment? Clarify this and how contradictory this can be in the context of the contamination of MPs.

16. L124: Anti-colorimetric technique? Confused! Clear that up!

17. L122-139: Authors must clarify the quality assurance/quality control (QA/QC) procedures adopted in the analyses.

18. Authors must analyze the data using appropriate statistics and explore it better, which can be achieved by consulting a statistics specialist. The findings reported by the authors were not adequately analyzed, which constitutes a significant limitation of the study. Furthermore, quantifying MPs in soils must confirm several speculations presented throughout the discussion. Without this quantification, it won't be easy to relate the variables investigated.

19. As long as I can remember, the rule has been that the title or caption for a table, along with the footnotes, to a table or figure, should provide enough information so that a reader can determine what the table or figure is showing without having to look for additional information in the text of the article. This means that all symbols and abbreviations must be defined in the table or the notes under the table, and the title must be very clear. This needs to be repeated separately for each table and figure on paper. Therefore, I recommend reforming the titles and captions of the figures/tables to make them self-explanatory.

20. Finally, careful proofreading in English should be carried out. Some sentences are difficult to understand. Thus, please write your text in good English (American or British usage is accepted, but not a mixture of these). Alternatively, authors may use the English Language Editing service available from Elsevier's Author Services.

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Reviewer #1: Yes: Dr. Farzad Rassaei, PhD

Reviewer #2: No

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Short Communication: Evaluating the impacts of microplastics on agricultural soil physicochemical properties and toxic metal availability: an emerging concern for sustainable agriculture

PONE-D-23-41961R1

Dear Md. Simoon Nice,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and accepted for publication. 

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Kind regards,

Babar Iqbal, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

The reviewer is satisfied with the revision and recommend accepting the manuscript in its current form.