OZONE DEPLETION

ELECTROMAGNETIC SPECTRUM

TYPES OF UV RADIATION UV – A (AGING): Low energy. Thought to contribute to premature aging and wrinkling of the skin and has recently been implicated as a cause of skin cancer.   UV – B (BURNING): Medium energy. UVB is more dangerous than UVA and has been implicated as a major cause of skin cancers, sunburning and cataracts.   UV – C: High energy. UVC is extremely dangerous but does not reach the earth’s surface due to absorption in the atmosphere.  Most of the radiation below 290 nm is absorbed by the ozone in the upper atmosphere.  Depletion of this layer increases the amount of UVC reaching ground level. TYPES OF UV RADIATION

OZONE LAYER DECREASES…. INCREASED UV RADIATION ENTERS HEALTH

Impacts on environmental systems Decreased primary productivity (land & ocean) Damage to fish/amphibians / mammals Disrupt food chain Effects on food crops (beans, wheat, rice, corn) Impacts on environmental systems

ATMOSPHRE LAB

Cumulative Graph should look like…

Ozone Depletion Ozone- molecule consisting of 3 oxygen atoms Benefit to humans because it absorbs harmful UV radiation Ozone layer is being depleted because of the addition of chemicals (esp. CFC’s) that break apart the ozone molecule Ozone Video (2:20) Guided notes consideration: explain how CFC’s interact with ozone; describe the changes in the “hole”

CHEMICAL CLASSES OF OZONE DESTROYERS CHLOROFLOUROCARBONS (CFC'S) HALOCARBONS/HALONS (ODS) No significant natural sources identified Source: Air conditioning, Aerosol propellants, solvents, styrofoam GREAT longevity takes 5-7 years for CFC’s to go from ground to upper atm. Highly reactive group 17 Cl, Br, F Sources: Styrofoam, Solvents, Soil Fumigant, Fire Extinguishers

OZONE PHLEMISTRY WKST

NATURAL O3 becomes O2 NATURALO2 becomes O3 O3 + UV  O2 + ●O 3) ●O + ●O  O2 NATURALO2 becomes O3 O2 + UV  ●O + ●O 2) O2 + ●O  O3 2 Ozone become 3 Oxygen CFCs degrades O3 into O2 CCl2F2 + UV  ●CClF2 + ●Cl 2) ●Cl + O3  ClO● + O2 NO degrades O3 into O2 1) NO + O3  NO2 + O2 Airplanes!

OZONE CHEMISTRY for the visual learners

STEP 1: NATURAL FORMATION OF OXYGEN

STEP 2: Natural Formation of Ozone in the Stratosphere UV ENERGY 3 OXYGEN MOLECULES 2 OXYGEN RADICALS 2 OZONE MOLECULES

Step 3: Natural Breakdown of Ozone in the STRATOSPHERE

CFC’s BREAKING DOWN OZONE (anthropogenic causes) STEP 4: (anthropogenic causes) CFC Free Radical Chlorine OZONE CLO* OXYGEN Free Radical Oxygen Free Radical Chlorine PER CHLORINE ATOM BROKEN OFF BY UV RADIATION FROM CFC’S, 100-300,000 OZONE MOLECULES CAN BE BROKEN DOWN (~900,000 O3 MOLEUCLES PER CFC!)

Antarctic Ozone Hole (16 min) Ozzy Ozone (10 min) Ozone over Antarctica Antarctic Ozone Hole (16 min) Ozzy Ozone (10 min) See word document- standard: use Ozzy; honors: choose either; MY: Antarctic Ozone Hole Both videos will be a quicktime file found on the I drive

THOMAS MIDGLEY