Chem5151_strat1

Chem5151_strat1 - Stratospheric Chemistry Part 1 Darin...

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1 Stratospheric Chemistry – Part 1 Darin Toohey – CU PAOS • Why Do We Care? • Ozone – Discovery and History • Circulation • Chapman Chemistry • Catalytic Destruction • The Controversy • The “Big Surprise of 1985” http://web.lemoyne.edu/~giunta/chapman.html http://www.wv-hsta.org/uvproje/history.htm http://remus.jpl.nasa.gov/milestones.ht m http://www.smcm.edu/users/cmmattia/leadership/ozone/Assets/Timeline/timeline2.htm http://www.ciesin.org/docs/011-464/011-464.html http://www.nrdc.org/air/pollution/hozone.asp Some resources that I borrowed from
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2 Melanoma Why do we care? Phytoplankton The EPA estimates that 60 million Americans born by the year 2075 will get skin cancer because of ozone depletion. About one million of these people will die. (thinkquest.org) The Human Connection DNA isn’t just for humans – plants and animals too!
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3 Ozone History In 1785, Martinus Van Marum noted “the odor of electrical matter” in the description of the discharge of air. Note – this was before it was accepted that oxygen was a component of air! Officially named as a chemical in 1840 by Christian Schönbein, after he noted that it had a smell that was similar to that of phosphorus when exposed to air It was soon realized that ozone was a good disinfectant. Otto was first to market a water purifier based on ozone Marius Paul Otto
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4 In 1923, Gordon Dobson developed the first spectrometer to measure ozone in the atmosphere, and he characterized its latitudinal seasonal variability Brewer-Dobson circulation 2 Brewer-Dobson circulation 2
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5 1928 – Thomas Midgley develops chlorofluorcarbons for DuPont, inhaling them to prove that they nontoxic. These non-flammable compounds soon replace the deadly compounds (such as ammonia and SO 2 ) in home refrigerators CFCs become popular in the 1960s when americans want to live in sun belts, drive cars with air conditioning, and use spray cans for just about everything! In 1930, Sydney Chapman published several theoretical papers on upper-atmospheric ozone – now known as the “Chapman Cycle” O 2 + h υ ± O + O ( λ < 242 nm) (1) O + O 2 + M ± O 3 + M (2) O 3 + h υ ± O 2 + O ( λ < 336 nm) (3) O 3 + O ± O 2 + O 2 (4) 10 -21
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6 O O 3 O 2 O O 2 h ν h ν rate 1 = J O2 [O 2 ] (J O2 10 -11 s -1 , 30 km) rate 2 = k 2 [O][O 2 ][M] (k 2 9 × 10 -34 cm 6 s -1 at 250 K) rate 3 = J O3 [O 3 ] (J O3 10 -3 s -1 at 30 km) rate 4 = k 4 [O][O 3 ] (k 4 2 × 10 -15 cm 3 s -1 at 250 K) ] ][ [ ] [ ] ][ ][ [ ] [ 2 ] [ 3 4 3 2 2 2 3 2 O O k O J M O O k O J dt O d O O + = ] ][ [ ] [ ] ][ ][ [ ] [ 3
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Chem5151_strat1 - Stratospheric Chemistry Part 1 Darin...

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