Atmospheric Chemistry and Physics, vol. 11, issue 18 (2011) pp. 9971-9982
Interfacial layers on ice significantly influence air-ice chemical interactions. In solute-containing aqueous systems, a liquid brine may form upon freezing due to the exclusion of impurities from the ice crystal lattice coupled with freezing point depression in the concentrated brine. The brine may be segregated to the air-ice interface where it cre- ates a surface layer, in micropockets, or at grain boundaries or triple junctions. We present a model for brines and their associated liq- uid layers in environmental ice systems that is valid over a wide range of temperatures and solute concentrations. The model is derived from fundamental equlibrium thermody- namics and takes into account nonideal solution behavior in the brine, partitioning of the solute into the ice matrix, and equilibration between the brine and the gas phase for volatile solutes. We find that these phenomena are important to con- sider when modeling brines in environmental ices, especially at low temperatures. We demonstrate its application for en- vironmentally important volatile and nonvolatile solutes in- cluding NaCl, HCl, and HNO 3 . The model is compared to existing models and experimental data from literature where available. We also identify environmentally relevant regimes where brine is not predicted to exist, but the QLL may sig- nificantly impact air-ice chemical interactions. This model can be used to improve the representation of air-ice chemical interactions in polar atmospheric chemistry models.
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