172 Chapter 8 Confocal Fluorescence Microscopy of Interstitial Fluids in Freezing Electrolyte Solutions *

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: ice core
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.425.3067; http://thesis.library.caltech.edu/5471/10/08_Chap8_JC.pdf

The information content of ice core records and the strength of ice-atmosphere interactions depend on the morphology and composition of the fluid films threading polycrystalline ice. Flat ice surfaces separated by pure water always attract by dispersive forces. Thus, these films owe their existence to the presence of impurities and to curvature effects. Electrolyte impurities induce colligative effects, but also adsorb on charged ice surfaces and screen their resulting electrostatic repulsion. Film thickness � is not therefore a monotonically increasing function of electrolyte concentration as it may be surmised. This possibility is herein demonstrated via time-resolved confocal fluorescence microscopy imaging of the freezing and thawing process of electrolyte solutions doped with a dual-emission pH probe. During freezing of water, the pH probe accumulates into 12 � 2 �m thick veins embedded in a pristine ice matrix. The ice front advancing into a 1.0 mM NaCl electrolyte solution, in contrast, engulfs the pH probe into small pockets (<1�1 �m 2) distributed over the sample. Together, these observations are consistent with a non-monotonic dependence of � on ion concentration. The local pH