EESA10 - Chapter 8 notes

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Environmental Science
Silvija Stefanovic

Chapter 8: Ozone Depletion and Ultraviolet Radiation UV radiation responsible for photochemical smog, bleaching of paints and decay of plastics Conjugated bonds in organic molecules absorb UV radiation which damages these molecules Oxygen produced by photosynthesis forms a filter in the outer reaches of the atmosphere that absorbs the most energetic and harmful UV radiation The oxygen splits up and forms ozone; ozone layer can absorb UV radiation of higher wavelengths Less energetic radiation is not absorbed by the ozone layer and reaches ground level The UV radiation in UVB band still reaches ground level and can have deleterious effects on cells UVA radiation is less photochemically active and less harmful than UVB light We have adapted to UV stress by forming protective UV absorbing surface layers, repairing cell damage or replacing damaged cells Eyes less adapted but shielded by brows and squinting Ozone Depletion Molina and Rowland proposed that stratospheric ozone might be destroyed by industrially produced chlorine and bromine containing stable substances; these inert substances can reach the stratosphere where they are decomposed by high energy UV radiation and reactive Cl and Br are released Downward trend in the amount of stratospheric ozone has been measured in temperate and polar climate zones Ozone hole forms because of the generation of reactive chlorine on the surface of ice crystals in high altitude polar clouds This will result in an increased flux of UV radiation at the earth’s surface and in top layers of the ocean Health Effects Ozone depletion won’t simply increase all UVB related effects because adaptive reactions will dampen or even neutralize the impact of increase in UVB radiation Rates of sunburn won’t increase for regular sun exposure Human skin can adapt easily to gradual increases in UVB exposure Health effects due to increased reflux in UV radiation is skin cancer, cataracts and cellular immunity Decreased immunity may cause increased severity of infections, less effective vaccination and increase in non-Hodgkin’s lymphoma Skin Cancer UVB radiation can cause mu
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