Potential genesis and implications of calcium nitrate  in Antarctic snow

Mahalinganathan, Kanthanathan; Thamban, Meloth

doi:https://doi.org/10.5194/tc-10-825-2016

Articles | Volume 10, issue 2

https://doi.org/10.5194/tc-10-825-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/tc-10-825-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 10, issue 2

Research article

|

15 Apr 2016

Research article |

| 15 Apr 2016

Potential genesis and implications of calcium nitrate in Antarctic snow

Kanthanathan Mahalinganathan and Meloth Thamban

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Final revised paper (published on 15 Apr 2016)
Preprint (discussion started on 06 Nov 2015)

Interactive discussion

Status: closed

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

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- Supplement

RC C2396: 'review of Potential genesis and implications of calcium nitrate in Antarctic snow', Anonymous Referee #1, 29 Nov 2015
- AC C2909: 'Response to reviewer's comments', Kanthanathan Mahalinganathan, 30 Jan 2016
RC C2436: 'Referee comments', Anonymous Referee #2, 07 Dec 2015
- AC C2917: 'Response to reviewer's comments', Kanthanathan Mahalinganathan, 30 Jan 2016

Peer-review completion

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

AR by Kanthanathan Mahalinganathan on behalf of the Authors (08 Feb 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (15 Feb 2016) by Florent Dominé

RR by Anonymous Referee #1 (23 Feb 2016)

RR by Anonymous Referee #2 (28 Feb 2016)

Suggestions for revision or reasons for rejection

Comments to the paper:

Potential genesis and implications of calcium nitrate in Antarctic Snow.

by Mahalinganathan et al.

This is my second review of this manuscript and I’m happy to see that the Authors have written an improved version following almost all the referee suggestions.
In this way, I think that the present manuscript is ready to be published on The Cryosphere journal after few minor changes or clarifications.

1. I’m not yet convinced about ion chromatography detection limits (DL) for calcium and nitrate. Authors say that a 1000 ul loop was used for anions (i.e., nitrate) and a 100 ul loop for cations (i.e., calcium) determination. It seems to be unusual that the calcium DL (0.3 ug/l) is one order of magnitude lower than the nitrate DL (5 ug/l), although an injection volume ten times lower is used. Authors are requested to check their analytical procedures and the method performance.
2. The ionic balance of the coastal part of the PEL transect (Coast PEL) shown in figure 3 is quite surprising. Cations are not balanced by the measured anions and a too large contribution of HCO3- (around 50 % of the anion equivalents) is used to balance the ion content. The use of H+ and HCO3- to balance the excess of anion and cation, respectively, is a correct approach. A large anion excess can be justify by the dominance of acidic species, such as H2SO4 and HNO3 (and so, balanced by H+). On the contrary, a large cations excess is not usual in Antarctica, especially in coastal areas, where aerosol and snow are almost neutralized (at least in winter depositions) or acidic (in summer depositions). The anion lack could be due to problems in evaluating the nss-sulphate or, especially, the chloride contributions. Indeed, the mean nss-sulphate concentration seems to be quite low, while the chloride concentration is surely under-evaluated, with respect to the Na content. In coastal areas, the Na/Cl Eq/Eq ratio is close to 1, because of the proximity of the sea spray source. Instead, in the ionic balance shown in figure 3, the chloride concentration is about one half of the Na concentration. On the other hand, Authors could have over-estimated the Na concentration. Authors are requested to check their calculations or explain this anomaly.
3. A minor question: in several parts of the manuscript (and figure 6), the Authors report: “NO3- is associated with HNO3” or “… with Ca(NO3)2”. This is not correct and should be changed in “… with H+ (to give HNO3)” or “… with nssCa2+ (to give Ca(NO3)2)”, or simply: NO3- is present as HNO3 or as Ca(NO3)2.

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ED: Publish subject to minor revisions (Editor review) (14 Mar 2016) by Florent Dominé

AR by Kanthanathan Mahalinganathan on behalf of the Authors (22 Mar 2016) Author's response Manuscript

ED: Publish as is (05 Apr 2016) by Florent Dominé

Short summary

Our results show a strong association between calcium and nitrate ions in snow from two different regions that are > 2000 km apart in East Antarctica. Such association could have formed during the interaction between long-range transported dust with the atmospheric nitrate. This study also implies that apart from other well-known sources of nitrate in Antarctica, nitrate associated with mineral dust could form a significant portion of total nitrate deposited in Antarctic snow.