 |
| Titel |
Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation? |
| VerfasserIn |
D. M. Lienhard, A. J. Huisman, U. K. Krieger, Y. Rudich, C. Marcolli, B. P. Luo, D. L. Bones, J. P. Reid, A. T. Lambe, M. R. Canagaratna, P. Davidovits, T. B. Onasch, D. R. Worsnop, S. S. Steimer, T. Koop, T. Peter |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 23 ; Nr. 15, no. 23 (2015-12-09), S.13599-13613 |
| Datensatznummer |
250120213
|
| Publikation (Nr.) |
 copernicus.org/acp-15-13599-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| New measurements of water diffusion in
secondary organic aerosol (SOA) material produced by oxidation
of α-pinene and in
a number of organic/inorganic model mixtures (3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), levoglucosan,
levoglucosan/NH4HSO4, raffinose) are presented. These indicate that water diffusion coefficients are determined by several properties of the
aerosol substance and cannot be inferred from the glass transition temperature or bouncing properties. Our results suggest that
water diffusion in SOA particles is faster than often assumed and imposes no significant kinetic limitation on water uptake and
release at temperatures above 220 K. The fast diffusion of water suggests that heterogeneous ice nucleation on a glassy
core is very unlikely in these systems. At temperatures below 220 K, model simulations of SOA particles suggest that
heterogeneous ice nucleation may occur in the immersion mode on glassy cores which remain embedded in a liquid shell when
experiencing fast updraft velocities. The particles absorb significant quantities of water during these updrafts which
plasticize their outer layers such that these layers equilibrate readily with the gas phase humidity before the homogeneous ice
nucleation threshold is reached. Glass formation is thus unlikely to restrict homogeneous ice nucleation. Only under most
extreme conditions near the very high tropical tropopause may the homogeneous ice nucleation rate coefficient be reduced as
a consequence of slow condensed-phase water diffusion. Since the differences between the behavior limited or non limited by
diffusion are small even at the very high tropical tropopause, condensed-phase water diffusivity is unlikely to have significant
consequences on the direct climatic effects of SOA particles under tropospheric conditions. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|