Characterization of Coarse Organic Particulate Matter in Urban and Rural Switzerland Using Advanced Offline Mass Spectrometry

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study investigate the composition of coarse organic aerosol across rural, suburban, and urban areas of Switzerland. It identified two distinct classes of coarse OA, and compared their characteristics in seasons and regions. This research has a novel perspective and the conclusion is clear. Here are some suggestions for revisions:

Abstract: It would be better to specify the exact seasons and quantity of the sample collection.

Introduction: Studies on coarse particulate matter from industrial emissions can also be included here, as industrial emissions are also one of the main sources of urban particulate matter.

Materials and Methods: 2.7. Add the calculation formula and explanation of the principle of PMF.  Line 455: Where are these 100,000 particles from? All from the samples of this study?

Results and Discussions: Is there any content about the source analysis conducted using PMF included in the main text? Based on the data obtained through in-situ sampling in this study, can they be used to optimize the analysis results of PMF?

Conclusions: What benefits do the results of this study bring to the subsequent research in this field? Highlight the innovation and contribution of this study here.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article is devoted to the study of the organic fraction of atmospheric PM particles in the size range from 2.5 to 10 microns in various regions of Switzerland. The study was performed using modern methods of aerosol mass spectrometry and additional analytical methods. As a result of the analysis, two main classes of organic carbon were identified: primary biological organic carbon (PBOC) and sulfur-containing organic carbon (SCOC). The authors analyzed their spatial and temporal patterns, their relationship to sources (biogenic emissions, transport emissions), as well as their contribution to the total mass of organic carbon. Methodologically, the work was carried out at a high level: the authors use data from five monitoring stations of the type for a one-year period, which ensures the representativeness of the conclusions. 

1 – the literature should be given in accordance with the rules of the journal (references, as they occur).
2 – I ask the authors to clarify, where is the sulfur-containing carbon?  SCOC correlates with both non-explosive emissions (NEE-PM) and mineral dust (MINERAL-PM). However, without additional analysis (for example, metal-tracer ratios), it is impossible to separate the contributions of brake, tire, and road surface wear. A more detailed interpretation involving data on the elements (Ba, Cu, Zn, Sb) is recommended. 
3 – The authors consider air temperature as the most "active" factor influencing the aerosol composition. Of course, air temperature is a key factor that has both direct and indirect effects. However, unfortunately, I did not find in the manuscript an analysis of the effects of humidity, wind speed and direction, the amount and nature of precipitation, which are critically important for the resuspension of road dust (a key source of SCOC) and aerosol washout. This could explain individual peaks in concentrations unrelated to temperature. I understand that involving these parameters in the analysis is extremely time-consuming and will significantly complicate the manuscript. Therefore, I suggest that the authors limit themselves to a brief mention in the chapter "Discussion" of the possible influence of these factors on the content and composition of the aerosol. 
4 - The authors use bootstrap analysis to assess PMF uncertainty, but do not provide key output parameters: the percentage of successful factor identifications, ranges of profile variability and contributions. I ask you to clarify whether it is possible to supplement the manuscript with these clarifications. This would increase the transparency and repeatability of the study. 
5 - It is not completely clear what "average of the median" means (line 493).  It needs to be clarified what the authors meant, since the average of the medians calculated for different stations is not equal to the total median or the total average for the combined sample. If the authors wanted to present a single average value, then they should recalculate the total solubility over the entire data set.
6 - The conclusions are formulated only in the context of Switzerland. To assess the generalizability of the results, it is necessary to discuss their comparability with work in other temperate and Alpine regions (for example, research in the Alps, North America or Asia).
7 – It would be appropriate to supplement the manuscript with a map showing the study area, the location of sampling stations, and the main types of landscape (natural, residential, and industrial).

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The work is methodologically very detailed and makes a significant contribution to coarse-grained aerosol research.

I believe it should be made clearer that the results mainly concern the soluble fraction.

Of the 514 initial ions, only 11 remain for PMF analysis, which can lead to loss of information about less dominant sources and oversimplification of the aerosol chemistry. In the discussion, it should be made clear that PMF identifies the dominant, not the complete, spectrum of OCcoarse sources.

The regressions did not account for the additional uncertainty in the PBOC and SCOC factors themselves, assuming they were "completely correct." A brief explanation of why this uncertainty is negligible could be included in the main text.

Single-particle analysis only covers the two urban stations. If possible, add a brief discussion of potential differences in the composition of biological and mineral particles at rural stations.

The articles presenting the experiments must contain a thorough formal analysis of experimental errors, including errors in all measured variables and parameters presented, description of the instruments used, how they are used, calibration, etc. reality and overall error calculation in all applied maintenance and other rules.

The literature is current, extensive, and relevant, including key works. However, of the many sources cited, none are from the journal to which the manuscript was submitted.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have made the necessary revisions to the opinions. I have no further suggestions.

Reviewer 2 Report

Comments and Suggestions for Authors

I thank the authors for making changes to the text of the manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for taking most of my comments into account.