Comparison of co-located refractory black carbon (rBC) and elemental carbon (EC) mass concentration measurements during field campaigns at several European sites

Pileci, Rosaria E.; Modini, Robin L.; Bertò, Michele; Yuan, Jinfeng; Corbin, Joel C.; Marinoni, Angela; Henzing, Bas; Moerman, Marcel M.; Putaud, Jean P.; Spindler, Gerald; Wehner, Birgit; Müller, Thomas; Tuch, Thomas; Trentini, Arianna; Zanatta, Marco; Baltensperger, Urs; Gysel-Beer, Martin

doi:https://doi.org/10.5194/amt-14-1379-2021

Articles | Volume 14, issue 2

https://doi.org/10.5194/amt-14-1379-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/amt-14-1379-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 2

Research article

|

23 Feb 2021

Research article |

| 23 Feb 2021

Comparison of co-located refractory black carbon (rBC) and elemental carbon (EC) mass concentration measurements during field campaigns at several European sites

Rosaria E. Pileci, Robin L. Modini, Michele Bertò, Jinfeng Yuan, Joel C. Corbin, Angela Marinoni, Bas Henzing, Marcel M. Moerman, Jean P. Putaud, Gerald Spindler, Birgit Wehner, Thomas Müller, Thomas Tuch, Arianna Trentini, Marco Zanatta, Urs Baltensperger, and Martin Gysel-Beer

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Final revised paper (published on 23 Feb 2021)
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Preprint (discussion started on 25 Jun 2020)
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Interactive discussion

Status: closed

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

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- Supplement

RC1: 'major concerns expressed', Anonymous Referee #1, 21 Jul 2020
- AC1: 'Author reply to RC1', Martin Gysel-Beer, 19 Oct 2020
RC2: 'Review', Anonymous Referee #2, 21 Jul 2020
- AC2: 'Author reply to RC2', Martin Gysel-Beer, 19 Oct 2020

Peer-review completion

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

AR by Martin Gysel-Beer on behalf of the Authors (17 Dec 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (20 Dec 2020) by Pierre Herckes

RR by Anonymous Referee #1 (02 Jan 2021)

Suggestions for revision or reasons for rejection

Most of the concerns raised in the first review have now been rectified and the manuscript has improved significantly. However, there remain two issues that are not addressed properly. In the Abstract and Conclusion there is the explicit statement that "Overall, considering the five field campaigns, the median of the observed rBC to EC mass ratios for the whole dataset was 0.92, with a GSD of 1.50." While it is true that mathematically the very high GSD practically means that the two methods are indistinguishable within the limits of inherent uncertainties, given the fact that the mean only refer to the specific combination of individual campaigns of markedly different durations (14, 21, 24, 30, 54 days) without a-priori methodological planning and standardization, to provide a mean value is absolutely meaningless. If, for example, the campaign that provides mean value greater than unity had lasted twice as long whereas the other having mean value less than unity had been significantly reduced in duration, a 'mean value' exceeding unity would have been easily obtained (of course, with a similarly large GSD which conveys basically the same mathematical meaning). So I strongly suggest the authors should refrain from reporting 'mean' numbers in the Abstract and Conclusion, because it explicitly implies that the experimental setup had been well designed, standardized and balanced and are able to provide robust and high-quality data for detailed statistical analyses. This was certainly not the case with the manuscript.

My second concern is about the way the role of tar brown carbon is addressed in the revision (see Section 2.2.1). The reference and the quoted statement "...its absorbance decreases strongly from the blue–UV region of the electromagnetic spectrum towards the red region (Karanasiou et al., 2015), thereby reducing the potential impact of brown carbon interference” is outdated given the fact the significant red absorption of tar brown carbon has been only recently discovered (see references in my previous comments). The addition of "per unit mass" does not resolve the issue since tar brown carbon is in the form of large tar balls of several hundred nm from biomass burning emission (which is the most significant single source of PM2.5 in Europe according to several 14C studies), therefore their smaller mass-specific absorption may not necessarily mean that their overall contribution is not significant.

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ED: Reconsider after major revisions (02 Jan 2021) by Pierre Herckes

AR by Martin Gysel-Beer on behalf of the Authors (04 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (07 Jan 2021) by Pierre Herckes

AR by Martin Gysel-Beer on behalf of the Authors (17 Jan 2021) Manuscript

Short summary

Black carbon (BC), which is an important constituent of atmospheric aerosols, remains difficult to quantify due to various limitations of available methods. This study provides an extensive comparison of co-located field measurements, applying two methods based on different principles. It was shown that both methods indeed quantify the same aerosol property – BC mass concentration. The level of agreement that can be expected was quantified, and some reasons for discrepancy were identified.