Understanding atmospheric aerosol particles with improved particle identification and quantification by single-particle  mass spectrometry

Shen, Xiaoli; Saathoff, Harald; Huang, Wei; Mohr, Claudia; Ramisetty, Ramakrishna; Leisner, Thomas

doi:https://doi.org/10.5194/amt-12-2219-2019

Articles | Volume 12, issue 4

https://doi.org/10.5194/amt-12-2219-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-12-2219-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 12, issue 4

Research article

|

10 Apr 2019

Research article |

| 10 Apr 2019

Understanding atmospheric aerosol particles with improved particle identification and quantification by single-particle mass spectrometry

Xiaoli Shen, Harald Saathoff, Wei Huang, Claudia Mohr, Ramakrishna Ramisetty, and Thomas Leisner

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Final revised paper (published on 10 Apr 2019)
Supplement to the final revised paper
Preprint (discussion started on 17 Oct 2018)
Supplement to the preprint

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Comments for amt-2018-362', Anonymous Referee #1, 04 Nov 2018
- AC1: 'Author comment', Xiaoli Shen, 28 Jan 2019
RC2: 'Review of Shen et al.', Anonymous Referee #2, 24 Nov 2018
- AC1: 'Author comment', Xiaoli Shen, 28 Jan 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Xiaoli Shen on behalf of the Authors (28 Jan 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (30 Jan 2019) by Mingjin Tang

RR by Anonymous Referee #1 (18 Feb 2019)

RR by Anonymous Referee #3 (06 Mar 2019)

Suggestions for revision or reasons for rejection

Shen et al. describe the processing and interpretation of an atmospheric dataset of aerosol mass spectra collected by the LAAPTOF single particle mass spectrometer, and its comparison with an aerosol mass spectrometer (AMS). The work is very useful to LAAPTOF users and the mass spectrometry community, especially given the relative lack of literature on atmospheric measurements with this comparatively new SPMS. The data processing approach based on laboratory reference spectra is interesting and valuable. I only have a couple remarks and minor edits before final publication.

General remarks:

1. Section 2.2 describes how the spectra were grouped using fuzzy clustering, creating a soft assignment of each spectrum to one or more cluster centers, and then assigned to each cluster center using correlation coefficients. Unless I missed something, this seems to be a way of arriving at a hard assignment for each spectrum to one of the classes. Subsequent data analysis seems to be based on this hard assignment. Have the authors checked whether hard clustering (“fuzzyfier” = 1) would arrive at the same number fractions and cluster centers? It would be nice if the physical (or mathematical) meaning of the similarity fraction and the value extracted from fuzzy (rather than hard) clustering specifically for this study were explained more clearly.
2. What were the criteria by which the measurement period was split into those periods of different lengths? Period 4 seems a bit arbitrarily defined (having no other data to go by than the mass spectrometer results shown in the figures). Were those periods meteorologically different from each other? Also, were the data of the instruments on pg. 27, lines 25 – 29, used at all in this study?

Minor edits:

1. pg. 28, line 12: more accurate wording would be: the single particle is detected successively (not “coincidently”) by the two detection lasers, and its flight time (not diameter) is recorded and then converted to size. Also, the mass spectrometer itself, I believe, has better than unit mass resolution. The total system may be limited to unit mass resolution, so this should be worded accurately.
2. pg. 28, line 18: perhaps a short outline of the procedure would be good here.
3. pg. 35, line 33: Was this found for the LAAPTOF or a different SPMS?

Presentation/Figures:

Figure 1: This is an enormous caption. Perhaps some of the information could be put into a table or into the supplement (or both)?

Figure 2: The labels in the spectra are extremely hard to read, besides being a bit reader-unfriendly with its color-coded numbers that one has to read up about in the caption. The peak numbering is also a bit excessive. I’d suggest including a table that shows the signature peaks (m/z and name, if known) for each class, as well as those peaks present in each class, and reducing the number of labels (especially for unidentified peaks) in the graphs to a manageable number.

Figure 4: It might be useful to mark the periods from Figure 5 in graph 3 c).

Figure 5: It would be nice to repeat the class labels on the y-axis.

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RR by Anonymous Referee #4 (07 Mar 2019)

ED: Reconsider after major revisions (07 Mar 2019) by Mingjin Tang

AR by Xiaoli Shen on behalf of the Authors (18 Mar 2019) Author's response Manuscript

ED: Publish as is (22 Mar 2019) by Mingjin Tang

AR by Xiaoli Shen on behalf of the Authors (22 Mar 2019) Manuscript

Short summary

Based on single-particle mass spectra from field measurements in the upper Rhine valley, we identified characteristic particle classes and estimated their mass contributions without the need of a reference instrument in the field. Our study provides a good example for quantitative interpretation of single-particle data. Together with the complimentary results from bulk measurements, we have shown how a better understanding of the mixing state of ambient aerosol particles can be achieved.