Presentation on theme: "OZONE In 1994, the United Nations General Assembly voted to designate September 16 as "World Ozone Day", to commemorate the signing of the Montreal Protocol."— Presentation transcript:
OZONE In 1994, the United Nations General Assembly voted to designate September 16 as "World Ozone Day", to commemorate the signing of the Montreal Protocol on that date in 1987.United Nations General Assembly
Ozone in the lower troposphere especially in urban areas is bad ozone. In urban environments sunlight can combine with fossil fuel combustion byproducts (oxides of nitrogen and some hydrocarbons) to create ozone. Ozone is a major component of this photochemical smog and can irritate eyes, throats, lungs, and vegetation. Ozone concentrations during ozone alert days can be dangerous to those with chronic lung disease.
History CFC introduced 1928 by DuPont Replacing earlier toxic refrigerants (ammonia (NH 3 ), methyl chloride (CH 3 Cl), and sulfur dioxide (SO 2 )) and allowing widespread introduction of refrigerators into the public market during after 1930.sulfur
1930s. Chapman proposed that stratospheric ozone was created by sunlight and oxygen, and destroyed by sunlight and oxygen.
1960s. Measurements of ozone showed that the Chapman reactions were not sufficient to explain the lower than expected ozone levels in the atmosphere. NO can also be replaced by natural occurring Cl, Br, H, and O
Early 1970s. Paul Crutzen from Germany, realized that elevated stratospheric nitrogen levels resulting from elevated tropospheric N 2 O could increase NO in the stratosphere and destroy Ozone.
Early 1970s. The proposal of a supersonic airline fleet resulted in an assessment of such a fleet on the ozone layer. Paul Crutzen from Germany, among many other scientists, realized that elevated stratospheric hydrogen and nitrogen levels resulting from super sonic aircraft exhaust could be damaging to ozone layer.
1974. Sherwood Rowlin and Mario Molina report that the increasing levels of chlorofluorocarbons observed by James Lovelock could result in elevated stratospheric chlorine levels and hence damage stratospheric ozone. Since chlorine is a catalyst for ozone destruction a single chlorine atom can participate in the destruction of many ozone molecules.
1978. US bans non-essential use of CFCs ie. aerosol sprays. CFCs are still used as refrigerants as well as other applications.
1979-1984. Much debate about the predictions of Rowlin and Molina. Some scientists accused them of scaring the public with chicken little "The sky is falling " tactics. (1992) Available on Amazon for $0.01
1985. Farman, Gardinar and Shanklin from the British Antarctic Survey. Published results from ozone measurement at Halley Antarctic Research Station in _Nature_, May 1985. Average October ozone levels recorded by Farman's group at Halley Bay, Antarctica, from 1957 through 1984. http://undsci.berkeley.edu/article/0_0_0/ozone_depletion_09
1986. Susan Solomon and other atmospheric chemists note that chemical reactions on polar stratospheric clouds make the threat to stratospheric ozone much worse than originally proposed by Rowlin and Molina. Polar Stratospheric Clouds (PSCs) a.k.a. Mother of Pearl
1986. Susan Solomon and other atmospheric chemists note that chemical reactions on polar stratospheric clouds make the threat to stratospheric ozone much worse than originally proposed by Rowlin and Molina.
1987. The most recent world resolution regarding the problem of ozone depletion is the Montreal Protocol. The original Montreal Protocol was signed in the fall of 1987, based on negotiations started between european- scandinavian countries and the US over CFC's in aerosol sprays in 1983.
1995. Crutzen, Rowlin, and Molina share the Nobel prize in chemistry for their efforts at understanding ozone chemistry and the ozone hole.
1998 to present. Scientist explore the connection between climate change and ozone. Most climate models predict that increased levels of greenhouse gases in the atmosphere will: 1) raise near surface temperatures (Global warming) 2) result in colder stratospheric temperatures.
1998 to present. Colder stratospheric temperatures may: 1) enhance the occurrence of polar stratospheric clouds and the polar vortex strength which could delay the recovery of the Antarctic ozone hole 2) enhance the strength of the Arctic polar vortex and the occurrence of Arctic polar stratospheric clouds which could result in an Arctic ozone hole similar to that in the Antarctic.