Tham khảo sách 'chemistry part 34, julia burdge,2e (2009)', khoa học tự nhiên, hoá học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 838 CHAPTER 21 Environmental Chemistry Although it is unclear whether the CFCs already released to the atmosphere will eventually result in catastrophic damage to life on Earth it is conceivable that the depletion of ozone can be slowed by reducing the availability of Cl atoms. Indeed some chemists have suggested sending a fleet of planes to spray 50 000 tons of ethane C2H6 or propane C3H8 high over the South Pole in an attempt to heal the hole in the ozone layer. Being a reactive species the chlorine atom would react with the hydrocarbons as follows Cl C2H6---- HC1 C2H5 Cl C3H8 HC1 C3H7 The products of these reactions would not affect the ozone concentration. A less realistic plan is to rejuvenate the ozone layer by producing large quantities of ozone and releasing it into the stratosphere from airplanes. Technically this solution is feasible but it would be enormously costly and it would require the collaboration of many nations. Having discussed the chemistry in the outer regions of Earth s atmosphere we will focus in Sections through on events closer to us that is in the troposphere. Figure A volcanic eruption. Volcanoes Volcanic eruptions Earth s most spectacular natural displays of energy are instrumental in forming large parts of Earth s crust. The upper mantle immediately under the crust is nearly molten. A slight increase in heat such as that generated by the movement of one crustal plate under another melts the rock. The molten rock called magma rises to the surface and generates some types of volcanic eruptions Figure . An active volcano emits gases liquids and solids. The gases spewed into the atmosphere include primarily N2 CO2 HC1 HF H2S and water vapor. It is estimated that volcanoes are the source of about two-thirds of the sulfur in the air. On the slopes of Mount St. Helens which last erupted in 1980 deposits of elemental sulfur are visible near the eruption site. At high temperatures the hydrogen sulfide gas given off by a .
