6.2 Stratospheric Ozone

Atmosphere

Stratosphere 12-50 km thick Temperature increases with altitude (gets warmer!) Horizontal winds (jet stream) Contains ozone layer

Ozone 3 oxygen molecules

Ozone – O3 Dynamic equilibria Balance between two ongoing processes UV radiation passing through the Earth’s upper atmosphere is absorbed by the formation and destruction of ozone.

Ozone UV (ultraviolet) radiation is absorbed during the formation and destruction of ozone into oxygen (O2)

Ozone and UV light Allows UVa and UVb through, but blocks UVc waves   Allows UVa and UVb through, but blocks UVc waves UVa - causes wrinkles UVb - causes skin cancer UVc - worst one because of damage to organisms/tissues

UV radiation also affects other living organisms Damage to photosynthetic organisms. Especially phytoplankton – basis of many aquatic food webs.

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

Damage to the Ozone

CFCs are usually very stable CFCs are usually very stable. However, in the high stratosphere the UV radiation breaks them down releasing free chlorine atoms (chlorine is very reactive)

HOGS (Halogenated Organic Gases) HOG’s are usually stable but break down into halogen atoms (F, Cl, Br, I, At) which are highly reactive Ex. (CFC = chlorofluorocarbon Cl and F are halogens Organic = contains carbon

Depletion of Ozone

Damage to the ozone ODS (Ozone-depleting substance) Substance Use/source Notes Chlorofluorocarbons (CFCs or freons) Hydrochlorofluorocarbon (HCFCs) Halons Methyl bromide Nitrogen Oxides (NO, NO2, N2O, NOx)

Sources of CFC’s fire extinguishers, refrigerators, AC units

Sources of CFC’s fire extinguishers, refrigerators, AC units

Pollution Management Strategies

Reducing ODS Apply the “Replace, regulate and restore” model of pollution management to ODS. Strategy Example of action Altering the human activity producing pollution (replace). Regulate and reduce the pollutants at the point of emission. Clean up and restoration

Pollution Management of CFC’s and HOGS Reduce-Regulate-Restore model Reduce: Replace CFC’s with CO2, propane, or air Replace aerosol propellants Replace methylbromide pesticides with something other than GHG’s Don’t use aerosol hair products or deodorant

Pollution Management of CFC’s and HOGS Regulate: 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 refrigerators returned to manufacturers to recover harmful materials inside Capture CFC’s from scrap cars AC units

Pollution Management of CFC’s and HOGS Restore: Remove chlorine from the stratosphere or add ozone (not exactly feasible!) Ozone layer is slowly replenishing itself as long as we continue the ban

National and International Organizations

National and International Organizations UNEP (United Nations Environmental Programme) Montreal Protocol 1987

National and International Organizations UNEP (United Nations Environmental Programme) Key role in: Providing information Creating and evaluating international agreements Protection of stratospheric ozone

National and International Organizations Montreal Protocol 1987 International agreements on the reduction of ODS use. National laws and regulations aimed at reducing consumption of ODS (CFCs in particular)

The Montreal Protocol 1987 This protocol is very significant for a number of reasons: Best example of international cooperation on an environmental issue. An example of the precautionary principle in science-based decision making. Experts from many different fields coming together to research a problem and find solutions. The first to recognise that different countries could phase-out ODS chemicals at different times depending on their economic status. The first with regulations that were carefully monitored. 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

Hair Bands Ruined the Ozone Poison 1983… so much hairspray