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UA GC 170A1 - Ozone
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GC 170 1st Edition Lecture 12 Outline of Last Lecture I. ExamOutline of Current Lecture - Ozone:o Where is the ozone layer?o How is ozone produced?o How does ozone protect us from UV radiation?- CFC’so What are they?o How do they destroy the ozone?- Ozone discoveryCurrent Lecture- What & where is the ozone layer?- A layer of O3 molecules in the stratosphere- O3 is triatomic molecule o Absorbs high energy UV radiation- Absorbing electromagnetic radiation aids in understanding why temp increases in the atmosphere- Temp peaks above the region of highest concentration of O3- O3 absorbs incoming UV- Molecules vibrate and converts electromagnetic radiation to heat- Process of ozone production in stratosphere- Incoming UV radiation (photons) splits O2 molecules- Oxygen atom combine with O2 to form O3- Constant ozone production in stratosphere- Negative health effects of UV- Skin cancer- Cataracts in eyes- Immune system problems- Roles of ozone in atmosphere- Stratosphereo Absorbs UV radiationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Molecules break apart then reform- Troposphere o Role of a GHGo Absorbs and emits longwaveCFC’s- Chlorofluorocarbonso Molecule made ofo Chloro: chlorineo Fluoro: fluorineo Carbon: carbono Man made chemicals made in 1920’s - Why so important?o Wonder-chemical- non-toxic to humanso Evaporate quickly (absorb lots of energy)o Used in air conditioning & refrigeratorso Used in aerosol canso They are inert and don’t react with anything In stratosphere they react with UV radiation High energy photons (UV radiation) strike molecules  releases chlorine atom- Free chlorine destroys ozone molecules (up to 1000)- Creates ozone hole o Area of ozone depletion over south pole  3 times the size of United stateso Float into stratosphere (takes 30-100 years)- 1974 two scientistso Rowland & Molina questioned what CFC’s were doing?o Hypothesis: CFC’s are destroying the ozone layer Needed evidence of chlorine monoxide (CIO) and ozone levels in stratosphere If ozone levels depleted, then hypothesis would be proved trueo First observations: Measurements over Switzerland until 1975 Expected to see decreasing levels of ozone Much variability, difficult to see trend- No trendo British scientists in Antarctica (south pole) Observing atmosphere since 1956 1977, observed decreasing trend in ozone concentrationo Two kinds of observations Point measurements (weather balloons) Area measurements (satellites)- Ozone hole clearly recognized in 1985o Rowland & Molina Found evidence of depleted ozone, but concentrated over south pole Prove that CFC’s were causing Ozone hole, needed evidence of chlorine monoxide levels and ozone levels in stratosphereo 1987 NASA flight through the ozone hole ClO (chlorine monoxide) levels increased over south pole Ozone levels decreased over south pole Showed proof of link between ClO & ozone depletion- Why is ozone hole over South Pole?o Polar stratospheric clouds (small ice particles) Accelerate chemical reaction of ozone destruction Ice particles give surfaces for reactions to occur Long winter (no sun) creates very low temperatures which create the polar stratospheric cloudsOzone hole gets bigger between September &


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UA GC 170A1 - Ozone

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