GC 170 1st Edition Lecture 12 Outline of Last Lecture I Exam Outline 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 s o What are they o How do they destroy the ozone Ozone discovery Current 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 Stratosphere o Absorbs UV radiation These 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 GHG o Absorbs and emits longwave CFC s Chlorofluorocarbons o Molecule made of o Chloro chlorine o Fluoro fluorine o Carbon carbon o Man made chemicals made in 1920 s Why so important o Wonder chemical non toxic to humans o Evaporate quickly absorb lots of energy o Used in air conditioning refrigerators o Used in aerosol cans o 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 states o Float into stratosphere takes 30 100 years 1974 two scientists o 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 true o First observations Measurements over Switzerland until 1975 Expected to see decreasing levels of ozone Much variability difficult to see trend No trend o British scientists in Antarctica south pole Observing atmosphere since 1956 1977 observed decreasing trend in ozone concentration o Two kinds of observations Point measurements weather balloons Area measurements satellites Ozone hole clearly recognized in 1985 o 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 stratosphere o 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 clouds Ozone hole gets bigger between September October
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