Water activity as the determinant for homogeneous ice nucleation in aqueous solutions

被引:1013
作者
Koop, T [1 ]
Luo, BP
Tsias, A
Peter, T
机构
[1] ETH Honggerberg, Swiss Fed Inst Technol, Inst Atmospher Sci, CH-8093 Zurich, Switzerland
[2] Max Planck Inst Chem, Nachwuchsgrp, D-55020 Mainz, Germany
关键词
D O I
10.1038/35020537
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The unique properties of water in the supercooled (metastable) state are not fully understood(1). In particular, the effects of solutes and mechanical pressure on the kinetics of the liquid-to-solid phase transition of supercooled water and aqueous solutions to ice have remained unresolved. Here we show from experimental data that the homogeneous nucleation of ice from supercooled aqueous solutions is independent of the nature of the solute, but depends only on the water activity of the solution-that is, the ratio between the water vapour pressures of the solution and of pure water under the same conditions. In addition, we show that the presence of solutes and the application of pressure have a very similar effect on ice nucleation. We present a thermodynamic theory for homogeneous ice nucleation, which expresses the nucleation rate coefficient as a function of water activity and pressure. Recent observations from clouds containing ice are in good agreement with our theory and our results should help to overcome one of the main weaknesses of numerical models of the atmosphere, the formulation of cloud processes.
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页码:611 / 614
页数:5
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