Primary Study on the Real-Scale Cloud Experiments in a Long Vertical Shaft

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This project was originally scheduled for the period from 1993 to 1994 fiscal years to be carried out in the Nambu Shaft of Mitsui Coal Mining Co.in Kamisunagawa, Hokkaido. However the sudden closure of the shaft in September, 1993, forced us to search for another one suitable for the experiment. After several inquiries and negotiations, an agreement was reached in November, 1994, with Kamaishi Mining Co.in Iwate Prefecture on the use of one of their shafts, but it did not become usable until March, 1995, because of the repairment of facilities and the preliminary observation of enrivonmental conditions. After all these efforts, the first cloud experiment was done in April, 1995, and the second in October, and several results were obtained which fulfillled some of the original purposes of this project.In both of the experiments, it was observed that cloud was formed at altitudes of about ten to several tens of meters. Sulfur dioxide (SO_2) was emitted at the base of the shaft with a fl … More ow rate of about 1l/min, and its concentration was measured below and in the cloud together with the sulfate aerosol concentration. The sulfur content in the cloud water was also measured. As a result, it was found that the total amount of sulfur was conserved at least immediately below and above the cloud bottom, and also that almost all SO_2 was absorbed into the cloud water as it flowed in an updraft. In the second experiment, the vertical distribution of SO_2 concentration was obtained by an SO_2 meter loaded on the elevator. The concentation distribution was expressed by a double exponential funciton with two different decay constants for the altitudes below and above the cloud bottm. The half-life for the in-cloud decay was 80 s showing the rapidity of the rainout process. Cloud droplets size distribution was also observed at the top of the shaft. The size distribution was mostly monomodal with a peak around 9 mum, but a second peak appeared intermittently around 30 mum. Those large droplets were detected by the Water Blue Film method as well. The number concentration of those droplets was not high, but they were found to have significant contribution to the cloud water content. Less