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| Titel |
Freezing of Ethanol Aqueous Solutions Droplets Investigated by in situ Raman Spectroscopy and X-Ray Diffraction |
| VerfasserIn |
Sébastien Facq, Cristian Focsa, Michael Ziskind, Bertrand Chazallon |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250095899
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| Publikation (Nr.) |
 EGU/EGU2014-11375.pdf |
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| Zusammenfassung |
| Volatile Organic Compounds (VOCs) and other anthropogenic reduced trace gases may be
quickly transported to the upper troposphere in the course of active deep convection [1].
During vertical transport, large amounts of these VOCs may be trapped in supercooled
droplets that subsequently freeze. However, whether the organic species are trapped in the
bulk or rejected at the gas-ice interface during freezing is still unclear and could lead
to different ice particle reactivity in the latter case (compared to pure ice). VOCs
are also supposed to be easily released by rapid evaporation once in the UT [2,
3].
The behavior of supercooled droplets of dissolved volatile organic compounds during
freezing, the determination of the subsequent crystalline structures formed and the
mechanisms by which VOCs are trapped/released in the atmosphere is therefore critical to a
better understanding of the creation of new ice particles and the characterization of their
surface and reactivity properties.
In this study, two distinct ethanol aqueous solution droplets ((XEtOH)L = 8.7 wt % and
46.5 wt %) have been investigated by in situ Raman spectroscopy and X-ray diffraction
between 253 and 188 K. This temperature range has been extended down to 88
K to explore the phase diagram and the behavior below Tg in order to compare
with previous work focused on organic compounds of higher molecular weights
[4].
Depending on the initial EtOH content, it is proposed that the particle results in a complex
structure formed with a supercooled layer of relatively high ethanol content at the
liquid/gas interface or with an ethanol hydrate and a supercooled layer of high
ethanol content. Each case depends on temperature trajectories and may have the
potential to impact several atmospheric processes in comparison to the pure ice
case.
[1] Kley, D. Science, 276, 1043 (1997).
[2] Kerbrat, M. et al., J. Phys. Chem. A, 111, 925 (2007).
[3] Petitjean, M. et al., J. Phys. Chem. A, 113, 5091 (2009).
[4] Zobrist, B. et al., Atmospheric Chemistry and Physics, 8, 5221 (2008). |
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