Simulations of anthropogenic bromoform indicate  high emissions at the coast of East Asia

Maas, Josefine; Tegtmeier, Susann; Jia, Yue; Quack, Birgit; Durgadoo, Jonathan V.; Biastoch, Arne

doi:https://doi.org/10.5194/acp-21-4103-2021

Articles | Volume 21, issue 5

https://doi.org/10.5194/acp-21-4103-2021

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

https://doi.org/10.5194/acp-21-4103-2021

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

Articles | Volume 21, issue 5

Research article

|

18 Mar 2021

Research article |

| 18 Mar 2021

Simulations of anthropogenic bromoform indicate high emissions at the coast of East Asia

Josefine Maas, Susann Tegtmeier, Yue Jia, Birgit Quack, Jonathan V. Durgadoo, and Arne Biastoch

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Final revised paper (published on 18 Mar 2021)
Supplement to the final revised paper
Preprint (discussion started on 27 Jan 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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RC1: 'Review of Mass et al. 2020', Anonymous Referee #1, 29 Feb 2020
- AC1: 'Author comment on the manuscript', Josefine Maas, 17 Sep 2020
RC2: 'Review of Maas et al. by reviewer #2', Anonymous Referee #2, 12 Mar 2020
- RC3: 'Additional general comment', Anonymous Referee #2, 13 Mar 2020
- AC1: 'Author comment on the manuscript', Josefine Maas, 17 Sep 2020
RC4: 'Simulations of anthropogenic bromoform indicate high emissions at the coast of East Asia', Anonymous Referee #3, 22 Mar 2020
- AC1: 'Author comment on the manuscript', Josefine Maas, 17 Sep 2020

Peer-review completion

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

AR by Josefine Maas on behalf of the Authors (07 Dec 2020) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Dec 2020) by Neil Harris

RR by Anonymous Referee #2 (06 Jan 2021)

Suggestions for revision or reasons for rejection

I thank the authors for addressing my comments. I think this is nearly ready now. I would like to see the following changes and then I think the paper will be ready for publication. There is still just one significant issue that needs to be solved related to the years of study.

Line 9. “Power plants in East and Southeast Asian economies… ”. I think you need to be more specific. This could be read as the power plant size, number, or some other characteristic. You should make it clear that this is the number.

Line 12. Since this paragraph relates to the oceanic modelling, and the oceanic models support these findings, I would make it clear that “By means of Lagrangian analyses…” refers to oceanic ”Lagrangian analyses”

The information on the years being studied is not mentioned in the abstract. I think this is fairly critical information given the strong arguments linking rapid economic development to increases in emissions. Furthermore, I suggest you link the concluding statement in the abstract (line 35) to the period over which this conclusion is valid.

Line 19. Suggest making it clearer that these are concentrations in sea water. Perhaps use “in coastal waters” instead of “along the coastlines”.

“Atmospheric and oceanic measurements cannot distinguish between naturally and industrially produced bromoform and all the top-down and bottom-up emission estimates discussed above automatically include the latter.” I would just be a bit careful here. I think this is an over-simplification. For example, the top-down emissions from Ordóñez et al., 2012 actually prescribed a spatial distribution over the open ocean according to the satellite derived maps of chlorophyll-a, so this statement is not fully correct in this case. Perhaps lessen this to “…emission estimates discussed above potentially include the latter already.”

Line 102. “Especially” redundant.

Section 2.2 and 2.3. I think the authors need to be a bit clearer on some of the assumptions and need to give more justification for some of the methodological choices. There is an apparent mismatch between the years run for the oceanic model (2005-2006) and the years run for the atmospheric model (2015-2018). A more logical choice would have been to use the same time period for each model, but perhaps this was not possible. This is not necessarily a problem, but I would like the authors to state clearly that such a mismatch exists, explain why it exists (I assume the oceanic forcing is not available for the 2015-2018 period?), to give at least some kind of justification (limited year-to-year variability?), and to explain what impact this has on their conclusions. This seems to me to be the last major issue requiring attention prior to publication. It would be useful to discuss the effects of this choice in the uncertainties discussion in Sect 6.

Line 281. Change …is… to …are.
Line 284. Change the first DBPs to DBP.
Line 312. Change to “in the form”
Line 359. “… to the stratospheric halogen budget.”
Line 368. “…compared to bromoform from climatological…”’
Line 403. “and up to the cold point”

Section 5.2. Can the authors please tabulate the information presented in the latter paragraphs where the various comparisons between the observed and simulated atmospheric CHBr3 mixing ratios are reported. Try make a table with the mixing ratios from Low, Moderate, and High for the different regions where there are observations and list the refs in the table perhaps by using asterisks. This would make it easier to absorb this information. In some places in the text it is pretty difficult to follow, and at one point the authors tell us that the observations from the Pearl River Delta compare well with the observations, but we are not told what the values are.

Sect. 5.2 Can the authors please try to explain why the observations in the Strait of Malacca are much higher than in their simulation?

Line 511. I think you should state that we also need dedicated monitoring at coastal sites near to these anthropogenic sources.
Line 514. Provides
Line 537. input of 0.12-0.15 ppt Br.
Line 542. in the form of both,
Line 550. The highest uncertainties
Line 559. shown in most cases to give good agreement
Figure 10. Please make the coastlines more visible. Perhaps black would be a more suitable colour.

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RR by Anonymous Referee #1 (13 Jan 2021)

Suggestions for revision or reasons for rejection

The revision seems to have improved substantially from the previous version. Most of my concerns, as well as those from the other reviewers, from the originally submitted manuscript have been well addressed. The inclusion of multiple years of simulation and comparison with the KORUS-AQ have greatly strengthened the results. Overall, the revised manuscript looks good. My remaining major comment is about the Conclusions section. I understand that this section has been reworked substantially to address the concerns raised by me and reviewer #2. However, in present form, it becomes lengthy and to some point handwavy with not really relevant details. I agree with reviewer #2’s suggestion that it is important to include discussions on uncertainties, various key processes that are important for source gas and product gas transport to assess Br budget. However, you should be mindful that conclusion and discussion need to be succinct and to the point, by focusing on the key messages. It would be good to hear what the other reviewers feel about the current conclusions, but, in my view, this section can use some significant condensation.

Some minor editorial comments:

P2 L72. It is not 100% accurate to say “Once bromoform is photolyzed …” as bromoform can also lost significantly due to reaction with OH. Suggest change to “Once bromoform is photochemically destroyed …”

P3 L87. Here and throughout the text: I think the more common term is “Western Pacific”, not “West Pacific”

P3 L112. Bromine budgets -> bromine budget

P4 L146. I would suggest use either season-dependent or vary with season. “seasonally dependent” is probably not grammatically correct.

P5 L156. Consider change to “To assess the long-term …”

P5 L161. Should be “1/12 degree”

P5 L168. Suggest change “generally purely advective” to “primarily advection”

P5 L182. Add “a” before “specific”

P5 L183. Suggest change to “is representative of long-lived non-volatile DBP”

P6 L201. Should be “Henry’s Law constant”

P7 L244. I would just use “bottom-up bromoform emissions”, with no “derived”

P7 L247. Delete “area” after “Southeast”. These are regions, not areas.

P7 L258. I don’t think “evaluate the additional anthropogenic bromoform” is the correct description here. You are not really evaluating these results against observations (the KORUS-AQ comparison would be adequate to justify this point either as there were very few measurements up in the UT/LS region), but calculating the differences using sensitivity runs. I would suggest change to “quantify the additional anthropogenic bromoform contribution based on …”

P14 L514. I think here “substantial source of …” is adequate. The word “growing” is misleading unless you have data suggesting the water chlorination consumption is growing, hence more formation of bromoform from anthropogenic sources.

P15 L528. Amounts -> amount

P15 L549. Budgets -> budget

P15 L549. Aspect -> aspects

P26 Table 2, last column. Please clarify whether it is ppt of CHBr3 or ppt of Br?

Figures 6-10 caption and color bar legend, and the corresponding discussion in the text. For clarity, please clarify whether these are ppt of CHBr3 or ppt of Br?

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ED: Publish subject to minor revisions (review by editor) (13 Jan 2021) by Neil Harris

AR by Josefine Maas on behalf of the Authors (23 Jan 2021) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (25 Jan 2021) by Neil Harris

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Short summary

Cooling-water disinfection at coastal power plants is a known source of atmospheric bromoform. A large source of anthropogenic bromoform is the industrial regions in East Asia. In current bottom-up flux estimates, these anthropogenic emissions are missing, underestimating the global air–sea flux of bromoform. With transport simulations, we show that by including anthropogenic bromoform from cooling-water treatment, the bottom-up flux estimates significantly improve in East and Southeast Asia.