OZONE DEPLETION & CLIMATE CHANGE (Ch 20)

OZONE DEPLETION OZONE DEPLETION & CLIMATE CHANGE& CLIMATE CHANGE

(Ch 20)(Ch 20)

ELECTROMAGNETIC SPECTRUM

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.

HEALTHHEALTH

OZONE LAYER DECREASES…. INCREASED UV RADIATION ENTERS

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)

AT

MO

SP

HR

E

LA

B

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)

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

OZONE PHLEMISTRY WKST

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!

OZONE CHEMISTRYfor the visual learners

STEP 1:NATURAL FORMATION OF OXYGEN

STEP 2: Natural Formation of Ozone in the STRATOSPHERE

Step 3: Natural Breakdown of Ozone in the STRATOSPHERE

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)

Ozone over Antarctica

ANTARCTIC OZONE HOLE (16 MIN)

OZZY OZONE (10 MIN)

THOMAS MIDGLEY