Long-term (2001–2012) trends of carbonaceous aerosols from a remote island in the western North Pacific: an outflow region of Asian pollutants

Boreddy, Suresh K. R.; Haque, M. Mozammel; Kawamura, Kimitaka

doi:https://doi.org/10.5194/acp-18-1291-2018

Articles | Volume 18, issue 2

https://doi.org/10.5194/acp-18-1291-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-18-1291-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 18, issue 2

Research article

|

31 Jan 2018

Research article |

| 31 Jan 2018

Long-term (2001–2012) trends of carbonaceous aerosols from a remote island in the western North Pacific: an outflow region of Asian pollutants

Suresh K. R. Boreddy, M. Mozammel Haque, and Kimitaka Kawamura

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Final revised paper (published on 31 Jan 2018)
Supplement to the final revised paper
Preprint (discussion started on 05 Apr 2017)
Supplement to the preprint

Interactive discussion

Status: closed

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

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- Supplement

RC1: 'Comments on "Long-term (2001-2012) trends of carbonaceous aerosols from remote island in the western North Pacific: an outflow region of Asian pollutants and dust"', Anonymous Referee #1, 13 May 2017
- AC1: 'Responses to anonymous referee#1', Suresh Kumar Reddy Boreddy, 06 Jul 2017
RC2: 'Boreddy Review', Anonymous Referee #2, 19 May 2017
- AC2: 'Responses to anonymous referee#2', Suresh Kumar Reddy Boreddy, 06 Jul 2017

Peer-review completion

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

AR by Suresh Kumar Reddy Boreddy on behalf of the Authors (06 Jul 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Jul 2017) by Stefania Gilardoni

RR by Anonymous Referee #1 (21 Jul 2017)

RR by Anonymous Referee #2 (24 Jul 2017)

ED: Reconsider after major revisions (02 Aug 2017) by Stefania Gilardoni

AR by Suresh Kumar Reddy Boreddy on behalf of the Authors (13 Sep 2017) Author's response Manuscript

ED: Referee Nomination & Report Request started (03 Oct 2017) by Stefania Gilardoni

RR by Anonymous Referee #1 (16 Oct 2017)

RR by Anonymous Referee #2 (17 Oct 2017)

Suggestions for revision or reasons for rejection

-- Marine Aerosol
The authors did tone down the language of the marine discussion some to use “suggests” instead of “shows”, so it is better. But, it is still flawed, it not a main point of their work, and it should probably just be removed.
The authors state that the larger ratio of WIOM to WSOM is an indicator of fresh organic matter from the ocean (because the cited works associate WIOM with primary marine emissions). But then, WIOM, which is supposedly primary, does not correlate with sea salt (not to mention the lack of wind speeds high enough to actually produce primary marine aerosol). The authors state that the lack of correlation then suggests that the source of organic is still from the ocean but from a source independent of wind speed and sea salt. This would then be the secondary organic which is associated with WSOM (according to the cited papers), making the whole argument circular and contradictory.
The authors should state that this may be from a marine source but that it is far more likely that it is from a non-marine source. There may be some marine particles mixed with those from other non-marine (anthropogenic) sources. It is incredibly difficult to perfectly separate marine air masses and sample only marine emissions. The only evidence that these particles are marine are the back trajectories from over the ocean.
Additionally, there is no explanation on how Na+ was measured. If it is from a different paper, it should be still discussed briefly here.

--CCN Discussion
Where did the concentration of sea salt come from? If this is the same that was mentioned as calculated from Na+, this should be noted here. It is also unclear that “sea salt is not a major source of WSOC”. Should this instead be “sea spray” or “ocean sources” instead? Sea salt is not a source of WSOC in general.
The new discussion is better in that it shows the correlation of sea salt to CCN, in addition to WSOC to CCN. The slight increase in the correlation with WSOC+sea salt might actually be the most interesting point here. Together, they represent a larger fraction of the actual particle mass and may influence CCN activation. (The text states r = 0.69, and the figure says r = 0.68.) However, it is clear that the sea salt concentrations control that correlation, even when WSOC is added, since WSOC concentrations are so much smaller.
It is good that the authors noted that particle size is not included here, but more discussion should be added – size plays a really important role in CCN activation.

-- Grammar
This paper still needs to be edited for proper grammar. Some additional suggestions are below (but there are many more that need to be addressed).

L. 403: Remove “that” from “less than OC and that EC”
L. 317: Remove “the” from “source for the both sea salt”

The following sentences are still unclear and need to be rephrased or edited.
L. 247-248: “This result suggests that the dominance of SOA in carbonaceous aerosol over the western North Pacific.”
L. 301-303: “On the other hand, lower ratios of WSOC/OC in summer may suggest that the primary emission of OC from the ocean surface via sea-to-air flux due to the dominance of pristine marine air masses.”

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ED: Publish subject to minor revisions (review by editor) (26 Oct 2017) by Stefania Gilardoni

AR by Suresh Kumar Reddy Boreddy on behalf of the Authors (05 Nov 2017) Author's response Manuscript

ED: Publish subject to minor revisions (review by editor) (15 Nov 2017) by Stefania Gilardoni

AR by Suresh Kumar Reddy Boreddy on behalf of the Authors (25 Nov 2017) Author's response Manuscript

ED: Publish as is (20 Dec 2017) by Stefania Gilardoni

AR by Suresh Kumar Reddy Boreddy on behalf of the Authors (27 Dec 2017)

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Short summary

To better understand the impact of long-range atmospheric transport of East Asian pollutants over the western North Pacific, we conducted a long-term (2001–12) study on carbonaceous aerosols over the WNP, which demonstrates that the photochemical formation of WSOC and its contributions to SOA have increased over the western North Pacific via long-range atmospheric transport. Biomass-burning-derived carbonaceous aerosols have increased, while primary fossil-fuel-derived aerosols have decreased.