Ozone Depletion

• Ozone (O3)– Absorbs harmful UV radiation from sun

ozone is produced during lightning storms

• Chlorofluorocarbons (CFC’s) destroy ozone– CFC’s production was banned in 1977– CFC’s “live” for hundreds of years

banned in U.S. in 1996

Depletion of the Ozone Layer

Ozone (O3) in upper atmosphere blocks ultraviolet (UV) light from Sun.

UV causes skin cancer and cataracts.

O3 depletion is caused by chlorofluorocarbons (CFCs).

O3 is replenished with each strike of lightning.

aerosol propellantsUses for CFCs:

refrigerants

CFCsCFCs

Freon (CFC’s)

Trichlorofluoromethane (Freon-11)

Dichlorodifluoromethane (Freon-12)

F

Cl

CCl Cl

Cl

F

CCl F

CFC-11 and CFC-12 are odorless, nontoxic, nonflammable, and very stable.

chlorofluorocarbons

Mechanism of Ozone Depletion

• Initiation CCl2F2 Cl + CF2Cl

• Propagation Cl + O3 ClO + O2

ClO + O Cl + O2

• Termination

Solar radiation

A single chlorine molecule can destroy thousands of ozone molecules.

.

..

. . .

.

“free radical”

Ozone Hole Grows Larger

Ozone hole has increased 50% from 1975 - 1985

Ozone, O3

Monthly Change in OzoneTOMS Total Ozone Monthly Averages

Ultraviolet Radiation

• Skin cancer

• Cataracts

• Sun-glassesUVA & UVB protection

Greenhouse Effect vs. Ozone Hole

Greenhouse Effect

Depletion of O3

(ozone layer)...causes skin cancer

and cataracts

Caused by CFC's(chlorofluorocarbons)

destroying ozonelayer

Replace CFC's inAC & refrigerators

Global Warmingby trapping heat

on Earth

Caused by buildup of CO2

carbon dioxide

Plant trees toslow down and burn

less fossil fuels that produce CO2

Alike Different

Related toEarth's

Atmosphere

Man-made problem

Environmental Issues

OzoneHole

Different

Topic Topic