环境专业英语 07_ozone depletion.pptx

Ozone Depletion;Ozone hole in North America during 1984 and 1997. Source: NASA;Image of the largest Antarctic ozone hole ever recorded (September 2006), over the Southern pole.;Ozone (O3);Ozone (O3);Ozone cycle overview;Ozone (O3);;As well as emitting visible light, the sun also emits short-wavelength ultraviolet radiation. The ozone layer absorbs the shorter, more hazardous, ultraviolet wavelengths and hence keeps 95% - 99% of the sun’s ultraviolet radiation from striking the earth. A number of consequences can result from increased levels of UV (ultraviolet radiation) striking the earth, including: genetic damage, eye damage and damage to marine life. This short-wavelength ultraviolet radiation can affect human health by causing skin cancer and affecting the immune system. It also contributes to various types of damage to the eyes (e.g. keratitis or snow blindness, and various opacities on and within the eyes, including pinguecula, and cataract).;However, the ozone layer is being damaged. The decrease of stratospheric ozone was first reported in 1974 and the decrease was quickly linked to the increasing presence of a class of manmade compounds called CFCs or Chlorofluorocarbons.;Textbook P41;Consequences of ozone layer depletion