Ozone depletion
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Order the UV based on wavelength
• highest - UVA (gets all the way through) • middle - UVB (ozone layer absorbs lots of it) • lowest - UVC (non gets all the way through)
What is the term for ‘a combination of active processes that cancel out each other’s effects so that there is no overall change’
• dynamic equilibrium
What are some effects of UVB on living organisms
• skin cancer • cataracts • leaf tissue damage on plants - decreases photosynthesis
What is a halogen
• a group 7 element • they are highly reactive and are toxic
What pollutant gas contains chlorine
• CFC’s - chloroflurocarbons
What is the history of CFC’s
• after WWII - CFC’s were used as propellants for bug sprays, paints etc • during 1950’s and 60’s, CFC’s were used in air conditioning
What are the properties of CFC’s
• non-flammable • non-toxic • persistant
What are the sources for CFC’s
• fridges • air conditioning • paints • fire extinguisher
What was the Rowland-Molina principle
• was a 1974 paper suggesting that CFC’s could deplete the ozone layer • hypothesised; CFC’s are persistant, some in troposphere are getting into stratosphere. there is enough energy in the stratosphere to set chlorine free from CFC molecules
How do CFC’s deplete ozone in the stratosphere
• when CFC’s are exposed to UV, they break apart releasing chlorine atoms • free Cl molecules react with O3 which slows down O3 formation • chlorine monoxide reacts with free floating O2 that destroys O3 • this keeps on happening • Cl reacts with other gases to form HCl • they get put back in the troposphere and are washed away by rain
Why is ozone depletion greater at polar regions
• extremely cold temperatures • polar vortex winds • stratospheric clouds
What other gases cause ozone depletion
• HCFC’s • halons -bromine, fluorine and iodine
How do scientists monitor ozone levels in the stratosphere
• collect air samples - use weather balloons • ground bases surveys - equipment which measures how much UV radiation reaches earth’s surface • satellites - shows cloud movement
What is the Montreal Protocol
• global agreement to protect stratospheric ozone by phasing out production of ozone • alternative to CFC’s is HFC’s • they established a fund for LIC’s to make the phasing-out process easier for them