SOLUTE EFFECTS ON THE EVAPORATION OF ICE PARTICLES

The possible influence of trace chemicals, in particular sulfate, nitrate, and ammonia, on the growth and lifetime of ice crystals is studied theoretically, based on the concept of a transition layer on the ice surface. Solutes, which are produced in the gas phase or on the particle surface, can be incorporated into the bulk of the ice crystals during condensational growth and released from the bulk during evaporation. The solute accumulated on the surface of ice particles during evaporation tends to form a layer of concentrated solution, which alters the equilibrium vapor pressure and thus affects the evaporation of ice particles. Our analysis indicates that the evaporation of ice crystals can be retarded significantly by solutes, especially in polluted environments and for low ice particle number concentrations. It is also shown that ice particles in subsaturated air may survive without complete evaporation when the environmental ice-saturation ratio is above a temperature-dependent critical value that can be as low as 91%. Experimental and observational studies are necessary for verification. We also briefly speculate about other conditions in which atmospheric chemical processes may affect surface properties of ice particles.