A model of mercury cycling and isotopic fractionation in the ocean

Archer, David E.; Blum, Joel D.

doi:https://doi.org/10.5194/bg-15-6297-2018

Articles | Volume 15, issue 20

https://doi.org/10.5194/bg-15-6297-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Progress in quantifying ocean biogeochemistry – in honour...

https://doi.org/10.5194/bg-15-6297-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 15, issue 20

Research article

|

26 Oct 2018

Research article |

| 26 Oct 2018

A model of mercury cycling and isotopic fractionation in the ocean

David E. Archer and Joel D. Blum

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Final revised paper (published on 26 Oct 2018)
Supplement to the final revised paper
Preprint (discussion started on 07 Mar 2018)

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'comments from reviewer', Anonymous Referee #1, 25 Mar 2018
- AC1: 'Responses to reviewer comments', David Archer, 27 Apr 2018
RC2: 'what does this mean? subject?', Anonymous Referee #2, 09 Apr 2018
- AC1: 'Responses to reviewer comments', David Archer, 27 Apr 2018

Peer-review completion

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

ED: Reconsider after major revisions (14 May 2018) by Christoph Heinze

AR by David Archer on behalf of the Authors (21 Aug 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (06 Sep 2018) by Christoph Heinze

RR by Anonymous Referee #1 (18 Sep 2018)

RR by Jeroen Sonke (20 Sep 2018)

Suggestions for revision or reasons for rejection

Archer and Blum resubmitted a substantial revision of their marine Hg speciation and Hg stable isotope GCM. I find that the authors have taken into account all suggestions made by the reviewers; a good selection of published observations are now compared to model results and cited appropriately. The revised MS reads well, and despite model simplifications I think the scientific findings are a stimulating addition to the literature; I find the discussion of particle Hg flux vs advection in determining the deep Ocean Hg levels is now excellent. Apart from minor comments below I think the MS can be accepted without further revisions.

I have extracted the numerous SI tar files but can’t read the final format. They also do not seem to be cited in the main text.

Minor comments:
P2, l34. I think you mean odd-MIF here….plz check
P3, l28. “Other Hg transformation reactions are provoked by light, and only take place in the surface ocean (Blum et al.,2014;Bergquist and Blum, 2007).”

The REFs need to be after ‘by light’, and the 2nd part of the phrase changed to a suggestion. The REFs did not study Hg photochemistry in the surface Ocean.

P4, l1. ‘what 100m depth scale’?

Table 1, L3. MM should be MMHg?

Figure 1 caption. Maybe provide citation for the biological reactions, in particular DMHg (if biological at all!).

Figure 2 caption. “Comparison of Hg(tot) concentrations in pM from the model with data in the top row, from {Laurier, 2004 #6663} and {Zhang, 2014 #6675},”

The Zhang’14 reference makes no sense because it is a model paper; I see observations from Cossa (S Ocean cruise), from Lamborg (N-Atlantic), and another N-Atlantic cruise that are not cited. Plz cite all observations.

Figure 6 legend. Mason should be Munson.

Figure 10 plots: convert MM and DM to MMHg and DMHg

Figure 11 caption, line 1. ‘fractions’ should be fractionation?

Figure 12. Global mean Ocean d202 and D199 are 1.5 and 1.5. Marine sediments are not…?

P11, L14. Suggest to remind the reader that the two gases are Hg(0) and DMHg.

P11, L29 I think DMHg should be Hg(0)….?

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ED: Publish subject to technical corrections (21 Sep 2018) by Christoph Heinze

AR by David Archer on behalf of the Authors (08 Oct 2018) Author's response Manuscript

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Short summary

Humans have had a huge impact on the mercury cycle in the biosphere, but it is difficult to follow the mercury cycle because mercury has so many mobile forms, as gases in the atmosphere and solutes in water. Mercury isotopes constrain mercury fluxes and sources, because mercury has many stable isotopes, and different fractionation mechanisms have different fingerprints in those isotopic compositions. We present the first model of mercury isotopic composition in the ocean.