ozone depletion & climate change (ch 20)
DESCRIPTION
OZONE DEPLETION & CLIMATE CHANGE (Ch 20). ELECTROMAGNETIC SPECTRUM. 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. - PowerPoint PPT PresentationTRANSCRIPT
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OZONE DEPLETION OZONE DEPLETION & CLIMATE CHANGE& CLIMATE CHANGE
(Ch 20)(Ch 20)
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ELECTROMAGNETIC SPECTRUM
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TYPES OF UV RADIATIONTYPES OF UV RADIATION
UV – A (AGING)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)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: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.
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HEALTHHEALTH
OZONE LAYER DECREASES…. INCREASED UV RADIATION ENTERS
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IMPACTS ON ENVIRONMENTAL SYSTEMS
Decreased Decreased primary primary
productivity productivity (land & ocean)(land & ocean)
Damage to Damage to fish/amphibianfish/amphibian
s/ mammalss/ mammals
Disrupt food Disrupt food chainchain
Effects on Effects on food crops food crops
(beans, wheat, (beans, wheat, rice, corn)rice, corn)
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AT
MO
SP
HR
E
LA
B
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Cumulative Graph should look like…
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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)
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CHEMICAL CLASSES OF OZONE DESTROYERS
CHLOROFLOUROCARBONS(CFC'S)
CHLOROFLOUROCARBONS(CFC'S)
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.
HALOCARBONS/HALONS (ODS)
HALOCARBONS/HALONS (ODS)
Highly reactive group 17 Cl, Br, F
Sources: Styrofoam, Solvents, Soil Fumigant, Fire Extinguishers
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OZONE PHLEMISTRY WKST
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O2 becomes O3
1)O2 + UV ●O + ●O
2) O2 + ●O O3 O3 becomes O2
1)O3 + UV O2 + ●O
2) O3 + ●O O2 + O2 CFCs degrades O3 into O2
1)CCl2F2 + UV ●CClF2 + ●Cl
2) ●Cl + O3 ClO● + O2
NO degrades O3 into O2
1) NO + O3 NO2 + O2 AIRPLANES!
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OZONE CHEMISTRYfor the visual learners
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STEP 1:NATURAL FORMATION OF OXYGEN
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STEP 2: Natural Formation of Ozone in the STRATOSPHERE
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Step 3: Natural Breakdown of Ozone in the STRATOSPHERE
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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!)
OZONE
CFCFree Radical
Chlorine
Free Radical Oxygen
OxygenCLO*
STEP 4: CFC’s BREAKING DOWN OZONE (anthropogenic causes)
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Ozone over Antarctica
ANTARCTIC OZONE HOLE (16 MIN)
OZZY OZONE (10 MIN)
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THOMAS MIDGLEY