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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