Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y....
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Transcript of Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y....
![Page 1: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/1.jpg)
Enrichment of surface-active compounds in coalescing cloud drops
I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1
1 Department of Environmental Sciences, Weizmann Institute of Science, Rehovot 76100, Israel.
2 Michigan Technological University, USA.
IAAR 24.12.2008 Tel Aviv
![Page 2: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/2.jpg)
Questions we addressed
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth?
• Why commonly assumed dilution wouldn’t block possible effects?
• What are these substances?
• Are they really present on drop’s surface?
![Page 3: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/3.jpg)
Questions we addressed
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth?
• Why commonly assumed dilution wouldn’t block possible effects?
• What are these substances?
• Are they really present on drop’s surface?
![Page 4: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/4.jpg)
Cloud-and raindrops size distribution depend on surface tension of colliding drops
![Page 5: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/5.jpg)
Evaporation of cloud- and raindrops depend on the presence of non-water molecules on the surface of drop
![Page 6: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/6.jpg)
Drop-breakup and rate of fall depend on the surface tension of drop
![Page 7: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/7.jpg)
Questions we addressed and answered
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth? By modification of surface properties. Lets consider just one: surface tension.
• Why commonly assumed dilution wouldn’t block possible effects?
• What are these substances?
• Are they really present on drop’s surface?
![Page 8: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/8.jpg)
Questions we addressed and answered
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth? By modification of surface properties. Lets consider just one: surface tension.
• Why commonly assumed dilution wouldn’t block possible effects?
• What are these substances?
• Are they really present on drop’s surface?
![Page 9: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/9.jpg)
Two main stages of drop growth in a cloud
CloudCondensationNuclei0.01 μm
Droplet
10 μm Droplet
50 μm
Raindrop
1: Diffusion 2: Collision-coalescence
3000 μm
![Page 10: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/10.jpg)
Two main stages of drop growth in a cloud
CloudCondensationNuclei0.01 μm
Droplet
10 μm Droplet
50 μm
Raindrop
1: Diffusion 2: Collision-coalescence
3000 μm
Pure water addition, increase of collective surface area and volume
![Page 11: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/11.jpg)
Two main stages of drop growth in a cloud
CloudCondensationNuclei0.01 μm
Droplet
10 μm Droplet
50 μm
Raindrop
1: Diffusion 2: Collision-coalescence
3000 μm
Pure water addition, increase of collective surface area and volume
No new water addition, collective volume and amounts of substances don’t change, surface area decreases - insoluble species concentration increases!
![Page 12: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/12.jpg)
Two main stages of drop growth in a cloud
CloudCondensationNuclei0.01 μm
Droplet
10 μm Droplet
50 μm
Raindrop
1: Diffusion 2: Collision-coalescence
3000 μm
Pure water addition, increase of collective surface area and volume
No new water addition, collective volume and amounts of substances don’t change, surface area decreases - insoluble species concentration increases!
Coalescence concentrates water insoluble surfactants and leads to decrease of surface tension
![Page 13: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/13.jpg)
Questions we addressed and answered
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth? By modification of surface properties. Lets consider just one: surface tension.
• Why commonly assumed dilution wouldn’t block possible effects? There is no dilution at the stage of collision growth. There is enrichment!
• What are these substances?
• Are they really present on drop’s surface?
![Page 14: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/14.jpg)
Questions we addressed and answered
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth? By modification of surface properties. Lets consider just one: surface tension.
• Why commonly assumed dilution wouldn’t block possible effects? There is no dilution at the stage of collision growth. There is enrichment!
• What are these substances?
• Are they really present on drop’s surface?
![Page 15: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/15.jpg)
Coalescence of drops in laboratory simulation:
![Page 16: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/16.jpg)
Su
rfac
e te
nsi
on
, m
N-1m
Number of coalescence events
Surface tension decrease upon consecutive coalescence
(sessile drop with pendant drops preloaded by different surfactants)
Adsorption isotherm for stearic acid
![Page 17: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/17.jpg)
Questions we addressed and answered
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth? By modification of surface properties. Lets consider just one: surface tension.
• Why commonly assumed dilution wouldn’t block possible effects? There is no dilution at the stage of collision growth. There is enrichment!
• What are these substances? They are surfactants; Water-insoluble are the most efficient because of their enrichment in coalescing drops.
• Are they really present and active on drop’s surface?
![Page 18: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/18.jpg)
Questions we addressed and answered
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth? By modification of surface properties. Lets consider just one: surface tension.
• Why commonly assumed dilution wouldn’t block possible effects? There is no dilution at the stage of collision growth. There is enrichment!
• What are these substances? They are surfactants; Water-insoluble are the most efficient because of their enrichment in coalescing drops.
• Are they really present and active on drop’s surface?
![Page 19: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/19.jpg)
Sampling individual raindrops and measuring their surface tension
![Page 20: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/20.jpg)
Sampling individual raindrops and measuring their surface tension
“Icicle” method
![Page 21: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/21.jpg)
Surface area variation by varying drop volume cause variation of surface concentration of water-insoluble
surfactants and consequently surface tension
![Page 22: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/22.jpg)
Approximate surface area, cm2
50
6
0
7
0
80
Su
rfac
e te
nsi
on
, m
N-1m
Water-insoluble surfactants on raindrops decrease surface tension when surface area is decreased and
uncover themselves.
0.10 0.15 0.20 0.25 0.30
![Page 23: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/23.jpg)
Questions we addressed and answered
• How could chemical substances affect the microphysics of clouds after activation of droplets, at the stage of collision growth? By modification of surface properties. Lets consider just one: surface tension.
• Why commonly assumed dilution wouldn’t block possible effects? There is no dilution at the stage of collision growth. There is enrichment!
• What are these substances? They are surfactants; Water-insoluble are the most efficient because of their enrichment in coalescing drops.
• Are they really present and active on drop’s surface? Yes, we found them acting at individual raindrops.
![Page 24: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/24.jpg)
Conclusions
• Coalescence of drops concentrates water insoluble species on droplet’s surfaces and leads to decrease of surface tension.
• Water-insoluble surfactants were detected on the surface of individual raindrops.
• A chain of implications in cloud microphysics could be predicted and wait to be investigated.
![Page 25: Enrichment of surface-active compounds in coalescing cloud drops I. Taraniuk 1, A. Kostinski 2, Y. Rudich 1 1 Department of Environmental Sciences, Weizmann.](https://reader035.fdocuments.net/reader035/viewer/2022062712/56649c735503460f94925e2f/html5/thumbnails/25.jpg)
Thank you!
This work was supported, in part, by the US NSF this
work was supported by NSF grant ATM05-54670 and by
the Israeli Science Foundation (Grant #162/05). We are
grateful to W. Cantrell for helpful suggestions.
Acknowledgements