Sources and Geographical Origins of PM10 in Metz (France) Using Oxalate as a Marker of Secondary Organic Aerosols by Positive Matrix Factorization Analysis
, Laurent Y. Alleman 5, Nicolas Bonnaire 2 and Emmanuel Rivière 1Round 1
Reviewer 1 Report
Atmospheric particles (PM10) collected in Metz were analysed by an original source apportionment study. Positive matrix factorization (PMF) analysis was applied to a filter-based chemical dataset obtained for a period from April 2015 to January 2017. Nine factors were clearly identified, showing mainly contributions from anthropogenic sources of primary PM (traffic and biomass burning) as well as secondary aerosols (sulfate-, nitrate-, and oxalate-rich factors). Wood-burning aerosols exhibited strong temporal variations and contributed up to 30% of the PM mass fraction during winter, while primary traffic concentrations remained relatively constant throughout the year so that these two sources are the main contributors also during PM10 pollution episodes. Furthermore, the dominance of the oxalate-rich factor is related to secondary organic aerosol loadings which are still poorly characterized in this region. Concentration-Weighted Trajectory (CWT) analysis provided a significant transport of both nitrate-rich and sulfate-rich factors from Northeastern Europe but also from the Balkan region.
General comments
Why PM10 is investigated and not PM2.5 which is more relevant due to secondary aerosol formation?
There is in lines 2 - 4 at page 3: “After sampling, filters were frozen until analyses. Each filter 2 was subsampled in order to perform several analytical methods and built a comprehensive chemical 3 characterization dataset of PM10.” How the subsampling is realized if the filters were frozen? The filters were divided? This was before or after the frozen period? Which tools were used for filter division? In which environment this was performed?
Oxalate is not highlighted in the conclusions as it is suggested in title. This should be in balance.
The paper addresses relevant scientific questions within the scope of the journal.
The paper presents novel concepts, ideas and tools.
The scientific methods and assumptions are valid and outlined mainly so that substantial conclusions are reached.
The results are sufficient to support the interpretations and conclusions.
The description of experiments is not sufficiently complete and precise to allow their reproduction by fellow scientists. In chapter 2 important information is missing.
The quality and information of the figures are fine
The related work is cited.
Title and abstract reflect the whole content of the paper. But PM10 should be included in the title.
The overall presentation is well structured and clear. The language is fluent and precise but must be improved in detail.
The mathematical symbols, abbreviations, and units are generally correctly defined and used. But some questions exist.
Specific Comments
Which information about the factors for PMF were applied?
How the error coefficients and signal-to-noise ratios for PMF were determined?
What is the last line in Equ. 1?
Page 5, line 8: Why the end point altitude of 100 m was selected?
Page 11, line 9: “… with hotspots located i) over Eastern Germany …” and the reference 58 “Pay, M.T.; Jiménez-Guerrero, P.; Baldasano, J.M. Assessing sensitivity regimes of secondary inorganic aerosol formation in Europe with the CALIOPE-EU modeling system. Atmospheric Environment 2012, 51, 146–164.” Is not correct because the reference is for PM2.5, the year 2004 and does not conclude this. Also the spatial distribution of the nitrate-rich factors is not in correspondence with this reference.
Technical corrections
One cannot understand the captions of the figures without the text – more definitions used and explanations are required.
Author Response
Please see attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
General comment
The paper regards a source apportionment analysis done in Metz (France) for PM10 discussing in details secondary aerosol and trying to gather information of long-range transport using CWT. The paper is interesting and could be useful for readers. However, some aspects are not clear and some additional details should be included (see my specific comments). In conclusion, I believe that it could be published after a revision addressing my specific comments.
Specific comments
In the introduction there is a discussion of potentiality of source apportionment using receptor model as well as some of the main results found in France. I believe that it could be useful a mention to the recent study of Weber et al (Atmosphere 2019, 10(6), 310; https://doi.org/10.3390/atmos10060310) regarding source apportionment in 15 French site as well as to the results of Belis et al. (Atmospheric Environment 123, 240-250, 2015) regarding the accuracy of source apportionment studied during an European intercomparison exercise for receptor models.
Figure 1. I believe that ions are used as input. I mean Na+ not Na, and so on. It would be better to specify this in the x-axis labels. In case this is too difficult, a note could be given in the caption of the figure.
Line 20, page 6. What is reported as NWR (non parametric wind regression)? They seem what are generally called pollution roses in several papers. If this is the case, I would suggest to use the widely used pollution rose term.
Page 6 lines 19-20. Considering the VWT results, it is possible that some marine contributions associated to North Africa could be transported towards Europe during Saharan Dust advection?
Page 7 line 11. Better “do not” rather than don’t.
Page 7, lines 21-39. I would like to mention, in case it could be useful to the interpretation, that a recent study in Venice area (Barbaro et al., Science of the Total Environment 658 (2019) 1423–1439) found two primary biogenic factors, one mainly found in coarse fraction with a chemical profile similar to that found in this paper giving a contribution to PM10 around 3% so comparable with these results.
Figure 4. Please add the R2 values. Intercepts are not considered because not relevant?
Page 10 line 34. Why local? Why heavy fuels? I believe that it would be better to speak only of combustion.
Section 3.4 lines 17-20. This sentence is not very correct. Actually there are a number of papers using oxalate in PMF, probably, there are limited cases in which a factor dominated by oxalate is found. Please correct the sentence.
Supplementary. Table S1 please add intercepts. Table 2 should be S2, Figures 1, 2, and 3 should be S1, S2, and S3.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Thank you for improving the article corresponding to the reviewer comments
Reviewer 2 Report
Authors improved the paper during the revision process and answered reasonably to my questions. I believe that the paper could be accepted for publication in the present form.
