INVESTIGATION OF THE EFFECT OF PHASE TRANSITION OF WATER ON THE TRANSFORMATION OF AIR POLLUTANTS

1997：1）在露水的采集和监测中，露水的pH值相对于雨雾的pH值偏高。高浓度的亚硝酸、铵阳离子和羧酸，如甲酸和乙酸，2）在铵离子存在下，亚硝酸可被还原为分子态氮，并在露水干燥过程中从水相中逸出（水从露水中蒸发）。19981）通过溶液的冷冻加速了硫化物与过氧化氢的水相氧化的反应速率。这种硫化物氧化通过硫代硫酸盐、连三硫酸盐和连四硫酸盐连续进行，并最终产生硫酸盐。硫代硫酸盐氧化成硫酸盐甚至可以在冷冻溶液中发生。2）空调排水pH值较高，亚硝酸、铵离子、羧酸浓度也较高。3）亚硝酸在干燥过程中还原为露水中的分子氮的过程如下：（1）亚硝酸在干燥过程中被还原为分子氮; a）在水的蒸发过程中，露水中硫酸根离子与钠阳离子反应，硫酸钠以固态沉淀。B）过量的钠阳离子（未反应的）与亚硝酸根阴离子反应，然后亚硝酸钠以固态沉淀。（未反应的）与质子反应并且产生的亚硝酸可以从水相逃逸到气相，分子氮可以由亚硝酸与浓溶液中的铵通过蒸发水来生产。4）在阴天或夜间的环境空气和室内空气中可以观察到相对高浓度的亚硝酸。目前，我们开始研制选择性高灵敏度的亚硝酸监测系统。

1997 :1) In dew collection and monitoring, the pH values of dew were relatively high compared with those in rain or fog. High concentration of nitrous acid, ammonium cation and carboxylic acids, such as formic acid and acetic acid, could be observed in dew.2) Nitrous acid could be reduced to molecular nitrogen in the presence of ammonium cation and escaped from aqueous phase during the dryihg process of dew(evaporation of water from dew).19981) The reaction rate of the aqueous phase oxidation of sulfide with hydrogen peroxide was accelerated by freezing of the solution. This sulfide oxidation proceeds consecutively via thiosulafate, trithionate and tetrathionate, and finally produces sulfate. The oxidation of thiosulfate to sulfate could take place even in the frozen solution. On the contrary, trithionate and tetrathionate could not be oxidized to sulfate in frozen solution.2) The pH values were relatively high and the concentrations of nitrous acid, ammonium cation, carboxylic acid were also high in drain water collected from air conditioner.3) The reduction of nitrous acid to molecular nitrogen in dew during the drying process takes place as follows ;a) During the evaporation of water, sulfate ions in dew react with sodium cations and sodium sulfates precipitate in solid state.b) Excess sodium cations (unreacted) react with nitrite anions and then the sodium nitrites precipitate in solid state.c) Finally free nitrite anions(unreacted) react with protons and nitrous acid produced can escape from aqueous phase to gas phase, and molecular nitrogen can be produced from nitrous acid with ammonium in concentrated solution by evaporation of water.4) Relatively high concentration of nitrous acid could be observed in ambient air on cloudy day or at night and also in the indoor air. Now we began to develope the selective and sensitive monitoring system for nitrous acid.