Cloud condensation nuclei activity of six pollenkitts  and the influence of their surface activity

Prisle, Nønne L.; Lin, Jack J.; Purdue, Sara; Lin, Haisheng; Meredith, J. Carson; Nenes, Athanasios

doi:https://doi.org/10.5194/acp-19-4741-2019

Articles | Volume 19, issue 7

https://doi.org/10.5194/acp-19-4741-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-19-4741-2019

© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 7

Research article

|

09 Apr 2019

Research article |

| 09 Apr 2019

Cloud condensation nuclei activity of six pollenkitts and the influence of their surface activity

Nønne L. Prisle, Jack J. Lin, Sara Purdue, Haisheng Lin, J. Carson Meredith, and Athanasios Nenes

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Final revised paper (published on 09 Apr 2019)
Preprint (discussion started on 07 May 2018)

Interactive discussion

Status: closed

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

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RC1: 'Referee comment', Anonymous Referee #1, 23 Jun 2018
RC2: 'review', Anonymous Referee #2, 06 Jul 2018
AC1: 'Final author reply', Nonne Prisle, 27 Aug 2018

Peer-review completion

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

AR by Nonne Prisle on behalf of the Authors (03 Oct 2018) Manuscript

ED: Referee Nomination & Report Request started (10 Nov 2018) by Maria Cristina Facchini

RR by Anonymous Referee #2 (04 Dec 2018)

Suggestions for revision or reasons for rejection

My major concern about the ambiguity in the objectives of this study has been addressed by the Authors in their rebuttal. Their observations of surface tension effects on CCN activation for particles containing natural organic compounds - which are in fact weaker surfactants than the standard compounds employed in previous studies - highlight the potential complexity of surface films structure and properties in nascent cloud droplets.
The new version of the manuscript is certainly much clearer than the previous one, but I still see some misalignment between the manuscript and the contents of Authors’ rebuttal. As a consequence, I still find somewhat obscure statements like “It may also be an important contributor to pollen water uptake and CCN activity (line 5)” and “Our present characterization provides the basis for including pollenkit contributions explicitly in the description of pollen-water interactions over a wide range of atmospheric conditions” (lines 17-18). If CCN measurements were meant as a tool to observe aerosol microphysical properties such as surface tension effects (as successfully demonstrated by Figure 4 in the paper), then I cannot appreciate the relevance of targeting the CCN activity of pollen grains (and not simply of aerosols containing an organic material resembling pollenkit). Are the simulations of CCN activation of a 15 micron particle (Figure 4) really relevant for cloud formation studies? There is a sparse literature on the impact of fragmentation of pollen grains on CCN concentrations in pristine environments, but again, effects on CCN number are expected for submicrometer pollen fragments not intact grains. I suggest the Authors to remove this remaining ambiguity from the text of the manuscript. If instead, the “pollen-water interactions” refer to other properties of pollen grains, such as their ability to adhere to surfaces, this should be clearly specified in the Abstract.

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ED: Publish subject to minor revisions (review by editor) (09 Dec 2018) by Maria Cristina Facchini

AR by Nonne Prisle on behalf of the Authors (14 Jan 2019) Author's response Manuscript

ED: Publish as is (04 Feb 2019) by Maria Cristina Facchini

AR by Nonne Prisle on behalf of the Authors (12 Feb 2019)

Short summary

We measure surface activity and cloud-forming potential of pollenkitt, an organic mixture coating pollen grains. Cloud droplet formation is affected through both surface tension and bulk depletion, with a consistent particle size-dependent signature. We observe nonideal solution effects in pollenkitt mixtures with ammonium sulfate salt. Our results suggest sensitivity of general water interactions, including cloud formation by pollen and their fragments, to both atmospheric humidity and aging.