| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a method of cleaning polluted air which is capable of effectively removing the nitrate ions accumulated in a soil layer during autumn and winter seasons. SOLUTION: The polluted air is sucked by a blower 18, is passed upward in the soil layer 14 through a polluted air introducing pipe 16, an air duct 20 and a vent layer 22 and is released to the atmospheric air from the surface of the soil layer 14. The greater part of NOx dissolves into the water content of the soil and turns to nitric acid ions. In spring and summer seasons, the nitrate ions are removed by denitrifying bacteria in the soil and plants 32. In the autumn and winter seasons, the activity of the denitrifying bacteria and the plants 32 degrade with a decrease in the atmospheric temperature (ground temperature) and the nitrate ions are gradually accumulated into the soil. Before the denitrifying bacteria are activated, the nitrate ions are consumed by the plants 32. When the denitrifying bacteria are activated in the spring season, a large amount of the nitrate ions are already removed by the plants 32 and are effectively removed, in early spring or afterward, from the soil by both of the denitrifying bacteria and the plants 32.</p> |
