Real Scale Cloud Experiments in a Long Vertical Shaft -A Study on the Oxidation Process of Sulfur Dioxide

在岩手县釜石矿430m长的竖井中，利用放置在竖井顶部的电风扇提升约1m/s的潮湿上升气流形成人工云，并进行了以下实验：为了研究二氧化硫在云滴中的溶解和随后的氧化，这种气体被排放到竖井底部的气流中。然后利用升降机，通过多级撞击器分别对云滴和气溶胶颗粒进行采样。用碳酸钠浸渍过滤器收集二氧化硫。以浸渍甲醛的滤纸作为冲击器的收集介质，抑制硫酸的氧化；这个程序可以分别量化S （IV）和S （VI）。主要结果有：(1)云基上方。发现液滴中的S （IV）已与气相二氧化硫处于平衡状态。(2)在上升气流中，液滴中的浓度比S (VI)/S （IV）几乎保持不变。由此可见，溶解氧对二氧化硫的热氧化反应是缓慢的。云化学的一个显著特征是反应位点（即液滴）的出现和消失是难以捉摸的。因此，有必要了解液滴的形成过程。意外的是，在这个项目的第二年，电梯的停止使得追踪云内反应变得不可能。在这种情况下。研究的重点转向了云滴的形成和生长。沿着这条线，得到了以下结果：利用激光测距仪对云底高度进行了观测，发现云底高度分别在100m和10s的时空尺度上有波动。无机盐（如氯化钠和氯化锂）的水溶液在竖井底部雾化。结果，液滴的数量浓度明显增加，液滴的大小出现膨胀。然而，尺寸分布的模式保持不变。还发现雾化开始和浓度增加开始之间的时间取决于液滴的大小，并根据这种依赖来估计液滴的生长速率。少

In a 430m-long vertical shaft of Kamaishi Mine, Iwate Prefecture, artificial clouds were formed by raising a humid updraft of about 1m/s using an electric fan placed at the top of the shaft, and the following experiments were carried out :1. In order to investigate the dissolution of sulfur dioxide into cloud droplets and subsequent oxidation, this gas was emitted into the air stream at the bottom of the shaft. Then by utilizing an elevator, cloud droplets and aerosol particles were separately sampled through multistage impactors. Sulfur dioxide was also collected by sodium carbonate impregnated filters. As the collection media for the impactor, filter paper impregnated with formaldehyde was used to suppress the oxidation of sulfurous acid ; this procedure enabled one to quantify S (IV) and S (VI) separately. Main results are (1) Immediately above the cloud base. S (IV) in droplets was found to be already in equilibrium with the gas-phase sulfur dioxide. This implies that the rainout o … More f sulfur dioxide is a rapid process, and (2) The concentration ratio S (VI)/S (IV) in droplets stayed almost constant through the updraft. From this result it is concluded that the thermal oxidation reaction of sulfur dioxide by dissolved oxygen is slow.A distinct feature of cloud chemistry is that the reaction sites (i.e droplets) are appearing and disappearing elusively. Therefore it is essential to understand the droplet formation processes. Accidentally, in the second year of this project, the stoppage of the elevator made it impossible to trace the in-cloud reactions. In these circumstances. the study was turned to focus on the formation and growth of cloud droplets. Along this line, the following results were obtained :2. By means of a laser ranging device, the cloud base height was observed, and it was found to fluctuate with the spacial and temporal scales of 100m and 10s, respectively.3. Aqueous solutions of inorganic salts such as sodium chloride and lithium chloride were atomized at the bottom of the shaft. As a result, conspicuous increase was observed in the number concentration of droplets and their sizes were found to be inflated. However, the mode of the size distribution remained constant. It was also found that the time between the start of the atomization and the onset of the concentration increase depended on the droplet size, and the droplet growth rate was estimated from this dependence. Less