Atmospheric Processes Ozone Depletion. Quick recap… "The ozone layer" refers to the ozone within stratosphere over 90% of the earth's ozone resides Ozone

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  • Slide 1
  • Atmospheric Processes Ozone Depletion
  • Slide 2
  • Quick recap "The ozone layer" refers to the ozone within stratosphere over 90% of the earth's ozone resides Ozone is an irritating, corrosive, colourless gas with a smell O 3 formed by Ozone-Oxygen cycle, UV catalyst A reduction in atmospheric ozone has been observed in two ways General global reduction rate of approx. 4% Polar ozone holes annual drop in stratospheric concentration. Up to over the Antarctic and over the Arctic
  • Slide 3
  • Ozone depletion history Satellite measurements of ozone started in the early 70's first comprehensive worldwide measurements started in 1978 with the Nimbus-7 satellite carried TOMS (total ozone mapping spectrometer) today there are several different satellites measuring concentrations of ozone and other atmospheric gases Chlorofluorocarbons were first created in 1928 as non-toxic, non-flamable refrigerants, and were first produced commercially in the 1930's by DuPont 1974 research showed a link between CFCs and ozone depletion predicted a 7% decrease in 60 years US banned CFC's in aerosol sprays in 1978 Data collected by the British Antarctic Survey showing that ozone levels had dropped to 10% below normal January levels for Antarctica. NASA soon discovered that the spring-time ''ozone hole'' had been covered up by a computer-program designed to discard sudden, large drops in ozone concentrations as ''errors' Numerous studies since then have confirmed both the Antarctic hole, as well as an overall global decrease in Ozone One major study calculates that the global ozone has decreased 2.5% from 1969 to 1986 and another 3% drop from 1986 to 1993
  • Slide 4
  • dr8&feature=player_embedded dr8&feature=player_embedded orld_avoided.html orld_avoided.html
  • Slide 5
  • Why is there concern about ozone depletion? If UVB reaches the Earths surface it could; Be absorbed by living cells, which can: break up biological molecules Causing damage to DNA food chain implications Causes cancers or possibly cataracts Damage to plant tissue Damage to marine plankton
  • Slide 6
  • Categories of UV Light. The UV light worth considering is UVB which is almost fully absorbed by the ozone this could change?
  • Slide 7
  • UV (Ultraviolet) light absorption Categorised by its wavelength: Type of UV Light WavelengthCharacteristics UV A320-400 nmNot absorbed by ozone UV B280-320 nmAlmost fully absorbed by ozone UV C
  • The Montreal Protocol on Substances that Deplete the Ozone Layer " Perhaps the single most successful international agreement to date has been the Montreal Protocol. "-Kofi Annan, Former Secretary General of the United Nations
  • Slide 20
  • Timelineevents leading to the Montreal Protocol (1987) 1985 the Vienna Convention established mechanisms for international co-operation in research into the ozone layer 1985 marked the first discovery of the Antarctic ozone hole Montreal Protocol on Substances that Deplete the Ozone Layer was negotiated and signed by 24 countries and by the European Economic Community in September 1987 The Protocol called for the Parties to phase down the use of CFCs, halons and other man-made ODCs one of the first international environmental agreements that includes trade sanctions to achieve the stated goals of a treaty
  • Slide 21
  • Summary of Montreal Protocol Control Measures Ozone Depleting Substances Developed Countries (MEDC) (phase out date) Developing Countries (LEDC) (phase out date) Chlorofluorocarbons (CFCs)19952010 Halons19932010 Carbon tetrachloride19952010 Methyl chloroform19952015 Hydrochlorofluorocarbons (HCFCs) Freeze from beginning of 1996 35% - reduction 2004 65% - reduction 2010 90% - reduction 2015 Total Phase - 2020 Freeze 2016 Total phase out 2040
  • Slide 22
  • NASA/NOAA satellite data showing the rise in stratospheric chlorine and corresponding decline in ozone layer thickness from 1979 to 1997. As stratospheric chlorine declined in response to enactment of the Montreal Protocol, the first stage of ozone recovery began.
  • Slide 23
  • Questions Explain how humans activities have increased/caused ozone depletion (4 marks) Outline the methods that have been used to reduce ozone depletion (8 marks) Describe and explain why Antarctica is more susceptible to ozone depletion than equatorial regions (3 marks)
  • Slide 24
  • Summary of Ozone in the Stratosphere ne/2010/twentyquestions/


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