Dicarboxylic acids, oxoacids, benzoic acid, <i>α</i>-dicarbonyls, WSOC, OC,  and ions in spring aerosols from Okinawa Island in the   western North Pacific  Rim: size distributions and  formation processes

Deshmukh, Dhananjay K.; Kawamura, Kimitaka; Lazaar, Manuel; Kunwar, Bhagawati; Boreddy, Suresh K. R.

doi:https://doi.org/10.5194/acp-16-5263-2016

Articles | Volume 16, issue 8

https://doi.org/10.5194/acp-16-5263-2016

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

https://doi.org/10.5194/acp-16-5263-2016

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

Articles | Volume 16, issue 8

Research article

|

27 Apr 2016

Research article |

| 27 Apr 2016

Dicarboxylic acids, oxoacids, benzoic acid, α-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: size distributions and formation processes

Dhananjay K. Deshmukh, Kimitaka Kawamura, Manuel Lazaar, Bhagawati Kunwar, and Suresh K. R. Boreddy

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Final revised paper (published on 27 Apr 2016)
Supplement to the final revised paper
Preprint (discussion started on 30 Sep 2015)

Interactive discussion

Status: closed

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

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RC C8368: 'Results of evaluation', Anonymous Referee #2, 22 Oct 2015
- AC C12071: 'Responses to the comments of Referee #2', Dhananjay Kumar Deshmukh, 29 Jan 2016
RC C10331: 'Review', Anonymous Referee #3, 10 Dec 2015
- AC C12073: 'Responses to the comments of Referee #3', Dhananjay Kumar Deshmukh, 29 Jan 2016

Peer-review completion

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

AR by Dhananjay Kumar Deshmukh on behalf of the Authors (31 Jan 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (01 Feb 2016) by Veli-Matti Kerminen

RR by Anonymous Referee #2 (15 Feb 2016)

Suggestions for revision or reasons for rejection

Dicarboxylic acids, oxoacids, benzoic acid, a-dicarbonyls, WSOC, OC, and ions in spring aerosols from Okinawa Island in the western North Pacific Rim: Size distribution and formation processes

By Deshmukh et al.

The revised manuscript was evaluated. The discussion for the inorganic ions has been improved considerably. However, it was still hard to follow the discussion for the organic components. As proven by the 27 “may”s in the text, the revised manuscript still had too many speculations to explain the observations during this case study. Particularly, it was hard to follow the discussion on the oxidative production of organic components in aqueous droplets. There were also some points that the authors did not seem to address in the revision (e.g., line 354-357). I still saw many writing issues too, such as tense (i.e., mixing present and past tense as referring the observed results), conciseness (e.g., line 434-438), etc. After reading it, I am impressed unfortunately that the revised manuscript is still not an acceptable form by ACP. The followings are specific points I would like to make.

Specific comments:

Figure 2 is still confusing. The authors should provide the time information (in UTC or local time) for the trajectories as well.

In the text the discussion the authors are making with Figure 3 is about the overall chemical composition in the “fine” and “coarse” modes of particles. Such information is available from Table 1. I still do not see a point that the authors need to show Figure 3. This point has not been improved.

Line 186: The reference by Takiguchi et al. does not seem to show the analytical results of organic aerosols, but nitrate aerosols. This group has published a better publication showing the analysis of oxygenated organic aerosols in Okinawa (Irei et al.,EST, 2014). This reference seems more appropriate in this case.

Line 215-223: A writing issue. The authors should be able to organize the possible sources of C2 more concisely.

Line 300-302: State explicitly that the particle size grew during the long-range transport.

Line 341-347 and line 464-475: To explain the observed results of oxidation products found in the fine mode, the authors hypothesized that photooxidation occurred first in cloud droplets, which must be in large size, and then the droplets dried and shrank to smaller size. Did the authors find any supporting result for this particle shrink from the model calculation of LWC? If the latter assumption really happened, I expect that the oxidation products and the LWC were anti-correlated because the particles were dried. Contradictorily, the authors state later that the high correlation was observed between the ratio of WSOC, a group of oxidation products, to OC (or SO42-, for example) and LWC. The logic does not make sense…It will be worthwhile to show time series plot of temperature, RH, and the calculated LWC during the sampling periods (from March 18 to April 13) so that the hypothesis of particle shrink is partially supported by own data.

Line 428-431: I cannot follow the logic why the high loading of WSOC suggests significant contribution from fossil fuel combustion and biomass burning.

Line 646-654: I cannot follow the logic. The authors ruled out a possibility that the observed wC9 originated from sea-surface microlayer. Does the microlayer never contain wC9? The authors should show scientific evidence using references or observations.

Scatter plot of oxalic acid concentration vs. other organic compound concentration: N=5 does not sound an acceptable reason for excluding this plot from the paper because the authors are submitting this manuscript based on the 5 sample analysis anyway. Correlation coefficients for some linear regressions seem to be very high, indicating something. Error analysis should be used to judge that the slopes themselves and the differences between the slopes are significant. The authors should scientifically analyze the plots a little more deeply.

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RR by Anonymous Referee #3 (18 Feb 2016)

Suggestions for revision or reasons for rejection

Comments on the authors’ response:

Lines 157-164 and 189-198 in the revised manuscript:
While the authors made effort to address my comments, it did not address whether the air masses experienced precipitation events DURING the transport (not at the source or the sampling point). The HYSPLIT model can produce meteorological data such as precipitation data along a trajectory so the authors should be able to include this data and discuss about it in the revised manuscript.
In addition to this, the HYSPLIT can generate downward solar radiation flux data so this should also be included in the discussion about photochemical production of WSOC from OC in aerosol aqueous-phase (Lines 464-475 in the revised manuscript).

In connection to HYSPLIT model results, the vertical profiles of trajectories must be included in the Figure 2. When the vertical profiles show a contact with the ground, subsequent air mass movements are not very accurate.

Line 383-389 in the revised manuscript:
Shouldn’t ISORROPIA II predict the state of H+, NH4+, SO42-, and NO3- in the particle phase? This needs to be discussed in the revised manuscript as well.

Section 3.4 onwards:
I do not agree with the authors’ reasons for keeping the structure of these sections. While the authors present the size distribution data on some of “not so common in the literature” organic acids, they are not that useful to the readers if they are just presented in a report style as the case here. I ask the authors to group them based on the formation mechanisms instead of compound groups because that can make this section much more concise and scientifically interesting. As is now, the section is very descriptive and repetitive. It may be acceptable to present such a report style paper when these compounds were newly discovered but I do not see the readers excited to see yet another paper with lots of organic compounds in tables. I believe this manuscript can be improved if the authors address this issue.

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ED: Reject (19 Feb 2016) by Veli-Matti Kerminen

ED: Reconsider after major revisions (25 Feb 2016) by Veli-Matti Kerminen

AR by Dhananjay Kumar Deshmukh on behalf of the Authors (07 Apr 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 Apr 2016) by Veli-Matti Kerminen

RR by Anonymous Referee #3 (12 Apr 2016)

ED: Publish as is (13 Apr 2016) by Veli-Matti Kerminen

AR by Dhananjay Kumar Deshmukh on behalf of the Authors (14 Apr 2016)

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Short summary

Size-segregated aerosols in nine size bins were collected in spring 2008 at Cape Hedo, Okinawa, in the western North Pacific Rim, and measured for diacids and related polar compounds. Oxalic acid, glyoxylic acid, and glyoxal peaked at 0.65–1.1 µm in fine mode, suggesting their secondary formation possibly in aerosol aqueous phase. Their strong correlations with liquid water content in fine mode further suggest an importance of the aqueous-phase production in Okinawa aerosols.