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| Titel |
Glass formation and unusual hygroscopic growth of iodic acid solution droplets with relevance for iodine mediated particle formation in the marine boundary layer |
| VerfasserIn |
B. J. Murray, A. E. Haddrell, S. Peppe, J. F. Davies, J. P. Reid, D. O'Sullivan, H. C. Price, R. Kumar, R. W. Saunders, J. M. C. Plane, N. S. Umo, T. W. Wilson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 18 ; Nr. 12, no. 18 (2012-09-25), S.8575-8587 |
| Datensatznummer |
250011465
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| Publikation (Nr.) |
 copernicus.org/acp-12-8575-2012.pdf |
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| Zusammenfassung |
| Iodine oxide particles are known to nucleate in the marine boundary layer
where gas phase molecular iodine and organoiodine species are produced by
macroalgae. These ultra-fine particles may then grow through the condensation
of other materials to sizes where they may serve as cloud condensation
nuclei. There has been some debate over the chemical identity of the
initially nucleated particles. In laboratory simulations, hygroscopic
measurements have been used to infer that they are composed of insoluble
I2O4, while elemental analysis of laboratory generated particles
suggests soluble I2O5 or its hydrated form iodic acid, HIO3
(I2O5·H2O). In this paper we explore the response of
super-micron sized aqueous iodic acid solution droplets to varying humidity
using both Raman microscopy and single particle electrodynamic traps. These
measurements reveal that the propensity of an iodic acid solution droplet to
crystallise is negligible on drying to ~0% relative humidity
(RH). On applying mechanical pressure to these droplets they shatter in a
manner consistent with an ultra-viscous liquid or a brittle glass. Water
retention in amorphous material at low RH is important for understanding the
hygroscopic growth of aerosol particles and uptake of other condensable
material. Subsequent water uptake between 10 and 20% RH causes their
viscosity to reduce sufficiently that the cracked droplets flow and merge.
The persistence of iodic acid solution in an amorphous state, rather than a
crystalline state, suggests they will more readily accommodate other
condensable material and are therefore more likely to grow to sizes where
they may serve as cloud condensation nuclei. On increasing the humidity to
~90% the mass of the droplets only increases by ~20%
with a corresponding increase in radius of only 6%, which is remarkably
small for a highly soluble material. We suggest that the small growth factor
of aqueous iodic acid solution droplets is consistent with the small aerosol
growth factors observed in previous experiments. |
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