Ecological Problems In the world Students of 101 在101世界学生的生态问题.pptVIP

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Ecological Problems In the world Students of 101 在101世界学生的生态问题.ppt

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PROJECTEcological Problems In the world I. Introduction The theme of our report is “Global ecological problems”. We would like to tell you about the most important problems. We are very interested in this problem because it is really a very serious problem. II. We worked in the Internet. The worked under the leadership of our teachers : English teacher and the teacher of informatics. III. Ozone holes The discovery of the Antarctic ozone hole by British Antarctic survey scientists Farman, Gardiner and Shanklin (announced in a paper in Nature in May 1985) came as a shock to the scientific community, because the observed decline in polar ozone was far larger than anyone had anticipated. Satellite measurements showed massive depletion of ozone around the South pole. Susan Solomon, an atmospheric chemist at the National Oceanic and Atmospheric Administration (NOAA), proposed that chemical reactions on polar stratospheric clouds (PSCs) in the cold Antarctic stratosphere caused a massive, though localized and seasonal, increase in the amount of chlorine present in active, ozone-destroying forms. The polar stratospheric clouds in Antarctica are only formed when there are very low temperatures, as low as –80degrees C, and early spring conditions. In such conditions the ice crystals of the cloud provide a suitable surface for conversion of unreactive chlorine compounds into reactive chlorine compounds which can deplete ozone easily. Moreover the polar vortex formed over Antarctica is very tight and the reaction which occurs on the surface of the cloud crystals is far different from when it occurs in atmosphere. These conditions have led to ozone hole formation in Antarctica. This hypothesis was decisively confirmed, first by laboratory measurements and subsequently by direct measurements, from the ground and from high-altitude airplanes, of very high concentrations of chlorine monoxide (ClO) in the Antarctic stratosphere. During the Antarctic winter and spring