Ozone Depletion Ozone O 3 Absorbs harmful UV

Ozone Depletion • Ozone (O 3) – 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

Depletion of the Ozone Layer q Ozone (O 3) in upper atmosphere blocks ultraviolet (UV) light from Sun. q UV causes skin cancer and cataracts. q O 3 depletion is caused by chlorofluorocarbons (CFCs). Uses for CFCs: CFCs refrigerants aerosol propellants banned in U. S. in 1996 O 3 is replenished with each strike of lightning.

Freon (CFC’s) chlorofluorocarbons F Cl Cl Cl Trichlorofluoromethane (Freon-11) Cl C F F Dichlorodifluoromethane (Freon-12) CFC-11 and CFC-12 are odorless, nontoxic, nonflammable, and very stable.

Mechanism of Ozone Depletion “free radical” • Initiation CCl 2 F 2 • Propagation Cl. + O 3 Solar radiation Cl. O. + O. Cl. + CF 2 Cl. O. + O 2 Cl. + O 2 • Termination A single chlorine molecule can destroy thousands of ozone molecules.

Ozone, O 3 Ozone Hole Grows Larger Ozone hole has increased 50% from 1975 - 1985

Monthly Change in Ozone TOMS Total Ozone Monthly Averages

Ultraviolet Radiation • Skin cancer • Cataracts • Sun-glasses UVA & UVB protection

Greenhouse Effect vs. Ozone Hole Alike Different Global Warming by trapping heat on Earth Plant trees to slow down and burn less fossil fuels that produce CO 2 Depletion of O 3 (ozone layer). . . causes skin cancer and cataracts Environmental Issues Topic Caused by buildup of CO 2 carbon dioxide Different Greenhouse Effect Topic Related to Earth's Atmosphere Man-made problem Ozone Hole Caused by CFC's (chlorofluorocarbons) destroying ozone layer Replace CFC's in AC & refrigerators