Quick review of atmosphere layers Troposphere 0 – 12 km thick 75% of all gases in atmosphere; all weather happens here; temperature decreases with higher altitude (gets colder!)

Quick review of atmosphere layers Stratosphere 12-50 km thick horizontal winds (jet stream) contains ozone layer temperature increases with higher altitude (gets warmer!)

Quick review of atmosphere layers Mesosphere 50-80 km thick meteor showers happen here temperature decreases with higher altitude (gets colder!)

Quick review of atmosphere layers Thermosphere aurora borealis and aurora australis (northern lights) ionosphere is here…reflects radio waves for communications can be very very hot (2000+ ℃) !

Quick review of atmosphere layers Exosphere 550km+ above earth’s surface outermost layer of earth’s atmosphere satellites orbit here

Atmosphere

Intro to Ozone Ozone is found in two layers of the atmosphere Stratosphere = good ozone Troposphere = bad ozone

GOOD OZONE (Blocks harmful UV radiation) BAD OZONE! (part of smog pollution)

HOW IS OZONE FORMED AND DESTROYED? http://www.bing.com/videos/search?q=ozone+formation&&view=detail&mid=14162985A2F47A87C8D314162985A2F47A87C8D3&&FORM=VRDGAR

Intro to Ozone O3 Made of 3 oxygen atoms A reactive gas What does ozone do? Stratospheric ozone blocks incoming UV radiation from the sun Protects life from damaging UV radiation!

The Ozone Layer The ozone layer is in dynamic equilibrium Ozone is constantly made from oxygen atoms and is continuously converted back to oxygen. Equilibrium because: there is a balance between two ongoing processes

The Ozone Layer UV radiation gets absorbed when ozone molecules are formed and when ozone molecules break apart

Ozone and UV radiation Ozone… allows UV-A and UV-B through blocks UV-C waves. Ozone layer absorbs 99% of UV-C and 50% of UV-B

Effects of UV radiation UV-A – Lowest energy (longest wavelength) causes wrinkles UV-B - causes skin cancer UV-C – Highest energy (shortest wavelength). Most harmful, because of damage to organisms/tissues

Effects of UV Radiation Damaging Effects: Genetic mutations that effect health Damage to living tissues (sunburns, etc.) Cataract formation in eyes Skin cancers Suppression of immune system

Effects of UV Radiation Damaging Effects: Damage to photosynthetic organisms, especially phytoplankton Damage to consumers of photosynthetic organisms, especially zooplankton (these are the BASE OF AQUATIC FOOD WEBS!)

Beneficial Effects of UV In animals, stimulates the production of Vitamin D Treat psoriasis and vitiligo (skin diseases) Steriliser, water purifier Forensics, lighting, lasers

Damage to the Ozone Layer Ozone Depleting Substances (ODSs) are breaking down the ozone layer

Sources of ODS’s aerosols (spray cans) gas-blown plastics pesticides flame retardants refrigerants

HOGs (Halogenated Organic Gases) HOG’s are usually stable but break down into halogen atoms (F, Cl, Br, I, At) which are highly reactive and destroy the ozone layer A type of HOG is chlorofluorocarbon (CFC)

CFCs (chlorofluorocarbons) CFC’s are usually very stable molecules But, in the high stratosphere, UV radiation breaks them down. Thus releasing free chlorine atoms, which are very reactive. The free chlorines break apart ozone molecules.

Therefore, MORE UV RADIATION reaches the earth. CFC’s enter the stratosphere. UV radiation hits the CFC molecules. UV radiation causes the Chlorine atoms to separate from their CFC molecules. The free Chlorine atoms bond to oxygen atoms that are part of ozone molecules. The ozone layer is depleted as more ozone molecules are broken apart.  Therefore, MORE UV RADIATION reaches the earth. The Chlorine atoms remove an oxygen atom from the Ozone molecules, breaking apart the ozone molecules Free chlorine atoms continue moving around the stratosphere, breaking apart more and more ozone molecules.

Explain how CFC’s are depleting the ozone layer. [5]

Replace – Regulate – Restore Model Replace CFC’s with CO2, propane, or air Replace aerosols with pump action sprays Replace methylbromide pesticides with something other than greenhouse gases Don’t use aerosol hair products or deodorant

Replace – Regulate – Restore Model Require a switch to HCFC’s because they don’t persist as long in the atmosphere; (They are still harmful to the ozone layer…just less so) Create laws to require that old refrigerators are returned to manufacturers to recover harmful materials inside Capture CFC’s from scrap cars AC units

Replace – Regulate – Restore Model Remove chlorine from the stratosphere or add ozone (not exactly feasible!) Allow the ozone layer to slowly replenish itself as long as we continue to ban ODS’s

International Organizations and Agreements How do we regulate all countries from using ODSs? UNEP - United Nations Environmental Programme Key role in: Providing information on air pollution Creating and evaluating international agreements Brought together the countries that formed the Montreal Protocol! Protection of stratospheric ozone

International Organizations and Agreements Montreal Protocol 1987 International agreement for the reduction of ODS use. National governments made laws and regulations aimed at reducing consumption and production of ODS (CFCs in particular) There have been many updates to the Montreal Protocol, that have made it even more effective

The Montreal Protocol - 1987 VERY significant because: Best example of international cooperation on an environmental issue. Example of the precautionary principle in science-based decision making. Experts from many different fields came together to research a problem and find solutions. The first to recognize that different countries could phase- out ODS chemicals at different times depending on their economic status. (LEDC’s were given more time) The first with regulations that were carefully monitored. Had updates to the agreement, which made it more effective

The Montreal Protocol - 1987 Precautionary principle - in environmental matters, the theory that if the effects of a product or action are unknown, then the product should not be used or the action should not be taken