Fundamental Study for Behavior of Pollutants in the Formation of Ice Fog

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We found that the acceleration mechanism of nitrous acid oxidation by dissolved oxygen in the freezing process is freeze concentration effect of the reactants into unfrozen solution confined between ice grains. The concentration factor of nitrous acid is estimated to be 2400 at -3ﾟC.In the study of evaporation loss of solutes from solution, it is found that solutes evaporate from the frozen sample to gas phase with stand time. This is also due to freeze concentration of solutes into the surface of the sample. The electrically neutral acid forms by bonding with proton which increase by freezing potential and evaporates into gas phase. The order of the evaporation rates of solutes we investigated was formic acid>acetic acid>propionic acid>butyric acid>hydrochloric acid>>nitric acid. The results we obtained suggest that the evaporation rate depends on mainly acid dissociation constants and also boiling pointsIn the field measurements for rain, fog and snow, concentrations of nitrite in winter sample were much smaller than those in summer and fog sample. This result suggest that nitrite is oxidized by freezing in the environment. Further, the ratio of concentration of chloride to that of sodium ion in winter was smaller that that in summer. One possibility of this loss is evaporation loss by freezing, but further study is needed. Some reports suggest that the evaporation loss of acetic and formic acids from snow pack in Antarctic or Green Land. It is required whether or not the changes of solutes by freezing occurs the environment and how amounts of solutes evaporate.