Ozone Depletion in the Stratosphere The other story Ch. 19

APES Everything away except a writing utensil

Altitude (kilometers) Ozone concentration (ppm) Altitude (miles) Stratospheric ozone Stratosphere Troposphere Photochemical ozone Beneficial Ozone Harmful Ozone *

What does the ozone layer do? Protects Earth from dangerous UV

What does the ozone layer do? Protects Earth from dangerous UV – Cause mutations Higher rate skin cancer, cataracts, and immune system problems – Essential for life: affect plants & marine ecosystems in unknown ways – Prevents tropospheric ozone Stratospheric Ozone Absorbs: ALL UV-C radiation (most energetic – most lethal) MOST UV-B radiation, but NO UV-A radiation

Consequence: Increase UV (UVB) reaching Earth’s surface Human – Sunburn – Skin Cancer – Cataracts – Efficiency in immune system Ecosystem – Reducing of primary productivity in oceans – Disrupt food chains – Damage fish/amphibians/mammal s – Widespread effects on major food crops – Decrease plant productivity – Impair/destroy phytoplankton

Class of Chemicals Primarily Responsible for Thinning of Stratospheric Ozone Layer

Chlorofluorocarbons (CFCs) – Coolant/refrigerant/air conditioner – Aerosol or propellant – Foam-blowing plastics/insulation (styrofoam) – Solvent/Cleaners Halocarbons – Fire retardants (fire extinguishers) – Soil fumigant/pesticide – Solvents – Foam blowing insulation

Class of Chemicals Primarily Responsible for Thinning of Stratospheric Ozone Layer Chlorofluorocarbons (CFCs) – AKA Freons – Wonder Chemical – Inexpensive – Stable in troposphere Chemically unreactive odorless nonflamable nontoxic, non corrosive

Class of Chemicals Primarily Responsible for Thinning of Stratospheric Ozone Layer Others – Hydrobromoflurocarbons (HBFCs) Fire extinguishers – Methyl bromide fumigant – Hydrogen chloride Emitted by space shuttles – Carbon tetrachloride, methyl chloroform, n- propyl bromide, hexachlorobutadiene Cleaning solvents

HOW do CFCs Break Down Ozone?* 1.CFCs & others released into troposphere 2.CFCs move/drift upward into stratosphere 3.UV radiation breaks apart CFCs releasing Chlorine (bromine/fluorine) 4.Sunlight causes chemical reaction allowing Cl to attack O 3 creating O 2 THUS reducing O 3 levels

HOW do CFCs Break Down Ozone?* CCl 3 F+UV Cl+CCl 2 F Cl + O 3 ClO + O 2 ClO + O CL + O 2

Sun Once free, the chlorine atom is off to attack another ozone molecule and begin the cycle again. A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2. The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). UV radiation Cl C F The chlorine atom attacks an ozone (O 3 ) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O 2 ). Cl O O O O O O O O O Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl 3, breaking off a chlorine atom and leaving CFCl 2. O CLICK ME!

How Do We Know This is Happening? Predicted by Mario Molina & Sherwood Rowland

How Do We Know This is Happening? James Lovelock predicted haze came from human sources Presented at conference with meteorologists & chemists

Original Hypothesis

Nitrogen Dioxide Neutralizes Some Chlorine Still Significant (though lower) levels of ozone depletion

Hypothesis Changes

Seasonal Thinning of Ozone at the Poles During four months of each year up to half of the ozone in the stratosphere over Antarctica and a smaller amount over the Artic is depleted.

Seasonal Thinning of Ozone at the Poles Polar stratospheric clouds - high-altitude clouds of ice particles in ozone layer Ice particles provide solid surface for reactions

Seasonal Thinning at the Poles  Ozone thinning (hole)  Polar vortex

Seasonal Thinning of Ozone at the Poles

Final Hypothesis

Additional Evidence Airplane flew through ozone hole

Ozone Depletion Occurs Worldwide

Montreal Protocol nations 50% reduction in CFC (not others) production by 1998 Phase out CFCs in developed countries by 1996 Phase out use of CFCs in developing countries by 2005

Copenhagen Protocol Montreal Protocol Amendment countries Accelerated phase out – by 1996 PREVENTION!!

International Cooperation Reach 1980 levels by levels by 2108

Ozone Depletion Projected worse over Antarctic and Arctic between 2010 & 2019

Need Help? Good Ozone Link

Characteristics of Global Warming and Ozone Depletion Global Warming CO 2, CH 4, NO x (greenhouse gases) Absorbs infrared (IR) radiation Raising the earth’s surface temperature Decrease burning of fossil fuels Ozone Depletion O 3, O 2, and CFCs Absorbs ultraviolet (UV) radiation Decreasing O 3 concentration in the stratosphere Eliminate CFCs