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

研究发现，冷冻过程中溶解氧加速亚硝酸氧化的机理是反应物进入冰粒间未冻溶液的冷冻浓缩效应。在-3 ℃时，亚硝酸的浓缩系数为2400。在溶质从溶液中蒸发损失的研究中，发现溶质从冷冻样品中蒸发到气相中的过程是随着放置时间的延长而进行的。这也是由于溶质冷冻浓缩到样品表面。电中性酸通过与质子结合形成，质子通过冻结电位增加并蒸发成气相。实验中所考察的溶质蒸发速率大小顺序为甲酸>乙酸>丙酸>丁酸>盐酸>硝酸。结果表明，蒸发速率主要取决于酸的离解常数和沸点，在雨、雾和雪的野外测量中，冬季样品中亚硝酸盐的浓度远小于夏季和雾样品中亚硝酸盐的浓度。这一结果表明，亚硝酸盐在环境中被冷冻氧化。此外，冬季氯离子浓度与钠离子浓度的比值小于夏季。这种损失的一种可能性是冻结蒸发损失，但需要进一步研究。有报道认为，南极或绿色土地积雪中的乙酸和甲酸蒸发损失。需要了解环境中是否会发生溶质因冷冻而发生的变化以及溶质的蒸发量。

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.