07 Jun 2022
Research article | 07 Jun 2022
First evidence of microplastics in Antarctic snow
Alex R. Aves et al.
- Final revised paper (published on 07 Jun 2022)
- Supplement to the final revised paper
- Preprint (discussion started on 04 Jan 2022)
- Supplement to the preprint
Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor |
: Report abuse
RC1: 'Comment on tc-2021-385', Anonymous Referee #1, 25 Jan 2022
- AC1: 'Reply on RC1', Alex Aves, 22 Mar 2022
RC2: 'Comment on tc-2021-385', Anonymous Referee #2, 28 Feb 2022
- AC2: 'Reply on RC2', Alex Aves, 22 Mar 2022
Peer review completion
AR: Author's response | RR: Referee report | ED: Editor decision
ED: Publish subject to revisions (further review by editor and referees) (07 Apr 2022) by Kaitlin Keegan
AR by Alex Aves on behalf of the Authors (19 Apr 2022)  Author's response Author's tracked changes Manuscript
ED: Publish as is (06 May 2022) by Kaitlin Keegan
Review of Aves et al.
So far as I know (and I am not an expert) this is the first documentation of microplastics in Antarctic snow. As such it is a valuable paper that documents the ever growing reach of this pollutant.
Analysis of air borne microplastics is a relatively new field and one where protocols are still being developed. I am pleased to see that considerable thought has gone into the minimising of contamination in this study. The sampling and analysis protocols are thoroughly described and rigorous, providing confidence that the results of microplastic concentrations are accurate. The discussion of the potential sources is thoughtful and realistic. I have some specific comments below that might be considered before final publication about the analysis and the sources.
The analysis method (section 2.3) involves visual identification of the microplastics followed by FTIR characterisation. This visual approach must necessarily preclude some very small microplastic fragments, but there is no discussion of a lower size limit. The useful effort to check recovery focusses on particles of 500µm. In Figure 5 the lowest size range is 0-200 µm. Around line 240 there is discussion of the possible bias against detecting small particles in this work, but I would suggest that this be discussed in the methods section.
Table A2 describes the size of particles, but particularly for fibres with one long and another short axis, the issue of size is ambiguous and the caption of this table could be expanded to clarify this.
The discussion of sources is thoughtful and interesting, although necessarily inconclusive. As I understand it the remote sampling sites are generally south and west of the main nearby stations (Mcmurdo and Scott Figure 3) and the airflow was generally from the south and east (Figure 6). In line 357 I think the authors imply that air masses containing the sampled snow would have passed over “the bases” before reaching the deposition sites and in line 300 they suggest the bases are the main source. Their data shows higher microplastics closer to the bases, so there clearly is a source there, but I’m not sure that their data does imply the bases are the sources for the microplastics at the sampling sites further from the Scott and McMurdo stations. I would say you cannot conclude if the source is from there or from very long range transport, but maybe I am missing something in the argument.
We do know, as the authors document, that long range transport of other material than microplastics does occur to Antarctica, so this is clearly a potential source. In that context I did not really understand in line 203 what the authors mean by the residence time. I think their figure of 156 hours is the longest trajectory they considered. However, assuming that microplastics can remain suspended in the air (my understanding of the term residence time) for longer than that, they could have been derived from further afield, or indeed have been deposited and resuspended from land or the sea en route. I would suggest the argument here might be clarified.