Long-term chemical characterization of tropical and marine aerosols at the Cape Verde Atmospheric Observatory (CVAO) from 2007 to 2011

Fomba, K. W.; Müller, K.; van Pinxteren, D.; Poulain, L.; van Pinxteren, M.; Herrmann, H.

doi:https://doi.org/10.5194/acp-14-8883-2014

Articles | Volume 14, issue 17

https://doi.org/10.5194/acp-14-8883-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-14-8883-2014

© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 14, issue 17

Research article

|

01 Sep 2014

Research article |

| 01 Sep 2014

Long-term chemical characterization of tropical and marine aerosols at the Cape Verde Atmospheric Observatory (CVAO) from 2007 to 2011

K. W. Fomba, K. Müller, D. van Pinxteren, L. Poulain, M. van Pinxteren, and H. Herrmann

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Final revised paper (published on 01 Sep 2014)
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Preprint (discussion started on 14 Feb 2014)

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

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RC C1249: 'Comments to acpd-14-3917-2014', Anonymous Referee #1, 09 Apr 2014
- AC C2959: 'Author´s answer to referee 1 comments', Hartmut Herrmann, 30 May 2014
SC C1303: 'comparison dust events at Izaña to CVAO', Rodriguez Sergio, 10 Apr 2014
- AC C2974: 'Author´s answer to short comments Rodriguez Sergio', Hartmut Herrmann, 30 May 2014
RC C1335: 'Review of the manuscript ‘’ Long-term chemical characterization of tropical and marine aerosols at the CVAO: field studies (2007 to 2011)’’', Anonymous Referee #2, 11 Apr 2014
- AC C2962: 'Author´s answer to referee 2 comments', Hartmut Herrmann, 30 May 2014

Peer-review completion

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

AR by Hartmut Herrmann on behalf of the Authors (30 May 2014)

ED: Referee Nomination & Report Request started (20 Jun 2014) by Tuukka Petäjä

RR by Anonymous Referee #1 (21 Jun 2014)

RR by Anonymous Referee #2 (27 Jun 2014)

Suggestions for revision or reasons for rejection

The authors have done a fair job in addressing most concerns raised, however, there are still a few issues outlined below that should be addressed.
Nss-sulphate.
I guess my comment on the inconsistency was not clear; I have not questioned the contribution of different sources to nss-sulphate concentrations in different air masses, which is nicely described in the author’s response. However, this is not the case in the MS, where there is no separation between different air masses (e.g. Figure 4 and 5). For the specific examples see below:
L293-296 ‘’ During non-dust period long range transport from the northwestern African coast, Europe and secondarily formed PM from the ocean were the main sources of nss-aerosol constituents. However, in the case of sulfate, nss-sulfate from oceanic sources was more important. ‘’
L401-409 gives some indication and points to the secondary production, but emphasis is still on the oceanic sources.
I understand this is valid for all air masses during non-dust periods and I read the general conclusion, which states that nss-sulphate concentration was dominated by the marine source.
While the following paragraph attributes it to the anthropogenic sources:
L563-566 ‘’ Nitrate and nss-sulfate showed good correlations during the winter and the summer (r² = 0.72) seasons (Nov-Apr and May-Oct, Figure 5) which could be attributed to their anthropogenic origin due to observation of frequent elevation of these concentrations during long range transport from Europe and Africa.’’
The same non-dust periods and long range transport from Europe and Africa as before, but here nss-sulphate is dominated by the anthropogenic sources; I understand that figure 5 includes all summer and all winter measurements without separating into different air masses?.
Those are only few examples …
Secondly, I still think that an addition of secondary marine nss-sulphate would distort the correlation (Figure 5), and would not contribute to the slope: biogenic nss-sulphate would not depend on the anthropogenic nitrate, therefore, high marine nss-sulphate contributions would equally occur at low and high nitrate levels. Moreover, adding a random amount of marine nss-sulphate at all levels of nitrate would introduce either scatter or intercept, but it would not affect the slope (Slope could only be affected by the proportional addition of more nss-sulphate for increasing nitrate, which, to my knowledge, could not be the case for marine nss-sulphate).
It should also be pointed out here that the main source of secondary nss-sulphate is assumed to be a cloud processing and condensation of gaseous precursors on the existing particles and not a nucleation. This is still not clear in the MS, and causes confusion.

And finally, a rhetorical question: what did authors mean by gaseous fresh nss-sulphate emitted from marine sources as stated in the reply?:
‘’ It is true that the freshly emitted nss-sulfate e.g from marine sources may not have enough time to get internally mixed with freshly emitted sea salt particles, but subsequently depending on the residence time of the sea salt particle these gaseous species may condense on the existing sea salt particles, thus, the term aged sea salt particles. ‘’

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ED: Reconsider after minor revisions (Editor review) (05 Jul 2014) by Tuukka Petäjä

AR by Hartmut Herrmann on behalf of the Authors (07 Jul 2014) Author's response Manuscript

ED: Publish subject to technical corrections (23 Jul 2014) by Tuukka Petäjä

Technical comments for Fomba et al. (2014) Long-term chemical characterization of tropical and marine aerosols at the CVAO: Field studies (2007 to 2011)

Title suggestion:
Long-term chemical characterization of tropical and marine aerosols at the CVAO from 2007 to 2011

Abstract:
line 25: OC and EC not defined.
Main text:
line 64: …, CVAO) in 2006 located at …
line 72: … et al. 2012) making it …
line 106: Long-term measurements in a remote site …
line 111: … filter measurements at the …
line 128: … about 10 m above sea level (asl)
line 157: … equilibrated for 72 h …
line 163:. The ion analysis …
line 177: … following literature
line 251: Comment. In line 369 you state that the concentration was five times higher. Please be consistent.
line 304: … shows the time series …
line 321: … a good indicator for the …
line 322: strikethrough left behind.
line 327: … the above mentioned features did not hold.
line 336: Figure 4 is introduced in two sentences. One is enough.
line 350: … of Saharan dust together with antropogenic gaseous …
line 360- 361: m/s would be consistent with the selected style for units.
line 364: … trajectory analysis and it is …
line 369: factor of 4-5 elsewhere
line 377: sea salt was not as strong as …
line 380-381: implying no influence of the dust storms on sea salt and particularly on sodium concentrations.
line 397: … aerosol composition.
line 403: … photochemical acitivity during. ..
line 421: … during dust storms and air mass…
line 502: … corresponding to sea salt (ss) and …
line 577-578: … in order to clearly explain the difference.
line 588: … was influenced by marine emissions …
line 604: Use São Vicente in a consistent way.
line 610: … previously illustrated above.
line 616: … found a good correlation
line 671: … concluded that the…
line 641: … by release of more reactive …
line 649: … evaporation of volatile …
line 663: … concentrations usually …
line 664: 62% / 9 %. End paragraph here.
line 669: … depletion of about 4 % …
line 678: … onto and react with …
line 669: … dust events there is no…
line 704: … particles thereby resulting …
line 709: … components are the …
line 718: … (Figure 10B).
line 737: Do you mean Figure 10C and 10D?
line 744: … chloride loss while during …
line 799: … particle composition.
References:
Please remove capitalization article names. Do not include issue numbers.
Check typing in following references:
Bates et al. 1992
Behnke et al.
Carpenter et al.
Chiapello et al.
Clarke et al.
Facchini et al. 2008
Jaenicke
Kandler et al.
Kawamura and Gagosian
Kerminen et al.
Lee et al.
Liebzeit
Mozurkewich
Paatero
Quinn et al.
Schultz et al.
Virkkula et al.

Figure 2: Please add A and B for sub-plots.
Figure 4: NH4+: please correct ylabel to be consistent with other sub-plots.
Figure 6: Use A,B and C to be consistent with the selected style.
Figure 8: Please use dates in a systematic format.
Figure 9: … 10 sample running mean…
Figure 10 C and D: One data point at high end can affect the slope a lot.

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