-->PONE-D-25-58360-->-->Chemical Composition, Seasonal Variability, and Source Identification of PM2.5 at an Urban Background Site in Medellín—Colombia-->-->PLOS ONE

Dear Dr. Correa Ochoa,

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PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions-->

-->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

Reviewer #3: Partly

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

Reviewer #1: N/A

Reviewer #2: Yes

Reviewer #3: Yes

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-->3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

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-->4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

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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: Some conclusions are not supported by the data. Eg, the traffic emissions contributions and their persistence. Also, it's difficult to check some conclusions as the months corresponding to PM2.5 concentrations are not mentioned in the figure.

Statistical analysis: As the authors have not made their data analysis code available, it's not possible to check the statistical analysis. However, just reading the methods, the statistical analysis looks correct.

Data availability - though the authors have mentioned that all the data are available without restriction, there is no reference to the raw data. There is no supporting information that contains the raw data or any online repository, eg., on GitHub.

English: The language of the paper can be improved.

Following is my feedback:

Overall, the authors collected substantial data to identify sources of PM₂.₅. However, the manuscript would benefit from improvements in writing clarity and more detailed descriptions of study area and meteorological conditions for each monitoring day. I recommend using a consistent definition of PC2 throughout the paper. Describing it solely as “secondary aerosols” in certain sections may be misleading to readers. In the discussion, it is unclear which specific months were affected by the COVID-19 lockdown. The manuscript states that lockdown began in mid-March 2020, but also mentions “mixed effects” beforehand without specifying the months involved.

Specific comments are provided below.

Abstract

Line 21: Change the capital “I” in “Industrial” to lowercase.

Line 22: Add standard deviations to the reported mean PM₂.₅ concentrations.

Lines 25- 27: Make it clear that traffic emissions here represents non-exhaust emissions. The conclusion is not well supported by the data. The so-called persistent sources, especially the non-exhaust traffic emissions only contribute <1% to total PM2.5 in all seasons (Table 6).

Introduction

Lines 84–86: Add references to support the statement about previous studies—what are the “few studies” referred to here?

Methods

Study Site

Provide more detail on surrounding roads: Are they fully paved, partially paved, or unpaved?

Clarify the sources of biomass burning in the region:

– Is it dominated by seasonal crop residue burning?

– Biomass use for cooking?

– Wood burning for heating?

Ensure consistent formatting of PM₂.₅ (use subscript for “2.5” throughout; e.g., lines 122, 127).

Line 120: Add the number of samples collected in each season.

Line 167: Correct to “analyzed”.

Results / Discussion

Line 187 (Table 2): Include standard deviations and medians for each variable measured in each season.

Why does the Dry 1 period have the lowest average concentration? Please discuss.

Figure 3:

– Mark rainy days or indicate the average rainfall on monitoring days, if any.

– Clarify the x-axis: include monitoring dates.

– Explain the smoothing method used for PM₂.₅ (e.g., CMA) and state the window size.

Line 255 (Table 5): In PC2, also include “mixed combustion”.

Line 262: Correct “PC” to “OC”.

Line 283: Table 6 is not cited in the text; please reference it.

Line 306: The effect of rainfall is not visible in the data. Need to mark dates in the figure 3.

Additionally, the impact of the lockdown is not apparent in the PM₂.₅ concentrations around mid-March 2020, mainly because the dates are not mentioned in the Figure 3.

Reviewer #2: General Comments

The manuscript titled ‘Chemical Composition, Seasonal Variability, and Source Identification of PM2.5 at an Urban Background Site in Medellín—Colombia’ explores the chemical composition and sources of PM in the city. The research is interesting and provides valuable insights. However, I think the manuscript needs improvements. Please check my comments below

• Section: 2.3 what is the error/uncertainty in the quantification of metals and ions

• Methodology section needs improvement in terms of what steps followed for quantification? What techniques used? What reagents used? This information will be helpful for readers to understand the research

• In table.2 please provide the SD along with mean. Also include the mean and SD of all the quantified chemical species

• PC5. Cl is also released from waste burning/mixed waste burning etc. How can you surely report it as Industrial emissions?

• I recommend authors to collect satellite VIIRS derived fire data and plot for the region around the city for the study period to show how many fire spots occur?

• It would be better if air mass back trajectories to the site is made and presented for the study period? May be concentration weighted trajectories?

• Provide some data on number of construction buildings in the city per year.

• Provide data of traffic vehicular count in the city

Reviewer #3: The manuscript entitled “Chemical Composition, Seasonal Variability, and Source Identification of PM2.5 at an Urban Background Site in Medellín – Colombia” analysed a year-long concentration of PM2.5 and its sources in Colombia. Even though the manuscript is written in a proper manner, it requires some significant changes that need to be implemented before publication. So a major revision is required to improve the quality. The General and specific comments are attached in seperate sheet.

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Reviewer #1: No

Reviewer #2: Yes: vignesh prabhu

Reviewer #3: No

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Attachments

Attachment

Submitted filename: Reviewer3-PONE-D-25-58360.pdf

Chemical Composition, Seasonal Variability, and Source Identification of PM2.5 at an Urban Background Site in Medellín—Colombia

PONE-D-25-58360R1

Dear Dr. Correa Ochoa,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Dipesh Rupakheti

Academic Editor

PLOS One

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.-->

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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-->2. 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: Yes

Reviewer #2: Partly

Reviewer #3: Yes

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-->3. Has the statistical analysis been performed appropriately and rigorously? -->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

-->4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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-->5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

-->6. 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: (No Response)

Reviewer #2: (No Response)

Reviewer #3: The authors had put a significant effort in correcting the manuscript. Now the manuscript can be considered for publication

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Reviewer #1: No

Reviewer #2: Yes: vignesh prabhu

Reviewer #3: No

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