Impact of exhaust emissions on chemical snowpack composition at Concordia Station, Antarctica

Helmig, Detlev; Liptzin, Daniel; Hueber, Jacques; Savarino, Joel

doi:https://doi.org/10.5194/tc-14-199-2020

Articles | Volume 14, issue 1

https://doi.org/10.5194/tc-14-199-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/tc-14-199-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 14, issue 1

Research article

|

23 Jan 2020

Research article |

| 23 Jan 2020

Impact of exhaust emissions on chemical snowpack composition at Concordia Station, Antarctica

Detlev Helmig, Daniel Liptzin, Jacques Hueber, and Joel Savarino

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Final revised paper (published on 23 Jan 2020)
Supplement to the final revised paper
Preprint (discussion started on 16 Oct 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Reviewer Comments on " Intrusion, retention, and snowpack chemical effects from exhaust emissions at Concordia Station, Antarctica" by Helmig et al.', Anonymous Referee #1, 19 Nov 2018
- AC2: 'Response to Reviewer #1 Comments', Detlev Helmig, 08 Apr 2019
RC2: 'Reviewer Comment on "Intrusion, retention, and snowpack chemical effects from exhaust emissions at Concordia Station, Antarctica"', Anonymous Referee #2, 01 Dec 2018
- AC1: 'Response to Reviewer #2 Comments', Detlev Helmig, 04 Apr 2019

Peer-review completion

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

AR by Detlev Helmig on behalf of the Authors (12 May 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Jun 2019) by Martin Schneebeli

RR by Anonymous Referee #1 (24 Jun 2019)

Suggestions for revision or reasons for rejection

The author have addressed in my view to satisfaction the reviewer comments and submitted a revised manuscript, which should be published in "The Cryosphere". Below I list a few minor comments, which should be addressed to clarify the argument presented.

Since this work addresses primarily air chemistry i.e. the chemical composition of air above the snow and in the interstitial air of the surface snow pack I strongly suggest replacing "snowpack chemical effects" throughout the text (possibly also in the title) with more precise terminology such as chemical composition of the interstitial air of the surface snow pack or air of the open pore space in the snowpack. The impacts of station exhaust on snow chemical composition and reactivity are discussed only qualitatively in light of snow nitrate profiles with no quantitative conclusions.

L14 / L228-234 GEM and CH2O are mentioned now also in the abstract, but throughout the manuscript not a single quantitative measurement is mentioned for these two species. Even though GEM and CH2O results related to pollution were not conclusive, at least order of magnitude and standard deviation of these observations during pollution events should be included. Otherwise it is hard to judge for the reader what was going on.

L138 - Please add here also very brief methodology detail / references for GEM and CH2O measurements, most importantly time resolution, limit of detection, and the mentioned instrument problems.

L240-243 This is an interesting question, but as the the authors noted in their rebuttal to a related reviewer comment, direct snow nitrate alteration is likely to be minor because the nitrate reservoir in the snowpack is so much larger than in the atmosphere. So either do a quantitative budget analysis or weaken the statement.

L303-306 the more likely scenario leading to increased snow NO3 near the station is the reduced nitrate loss due to decreased light penetration into the snow and therefore decreased photolysis rates from BC and possibly HULIS (Humic LIke Substances) contamination, as described in the previous section, and not direct deposition of NO3 from NOx rich air. Please clarify also in light of the large imbalance in NO3 mass distirution between snow and atmosphere.

L306-09 Mention here also the findings from the d15N studies at Dome C: no pollution signal in the snow; how about atmospheric nitrate? Did any of the nitrate filter samples collected over the years show pollution signal in d15N?

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RR by Anonymous Referee #2 (27 Jun 2019)

ED: Publish subject to minor revisions (review by editor) (28 Jun 2019) by Martin Schneebeli

AR by Detlev Helmig on behalf of the Authors (10 Sep 2019) Author's response Manuscript

ED: Publish as is (28 Sep 2019) by Martin Schneebeli

AR by Detlev Helmig on behalf of the Authors (25 Nov 2019)

Short summary

We present 15 months of trace gas observations from air withdrawn within the snowpack and from above the snow at Concordia Station in Antarctica. The data show occasional positive spikes, indicative of pollution from the station generator. The pollution signal can be seen in snowpack air shortly after it is observed above the snow surface, and lasting for up to several days, much longer than above the surface.