Ozone Depletion Flashcards
What does the ozone absorb?
Harmful UV radiation
All of UVC
Most of UVB
Some of UVA
Which layer of the atmosphere is the ozone?
The stratosphere
In which layer of the atmosphere is the ozone not supposed to be (harmful)?
The troposphere
How is the ozone layer formed from the release of CFCs into the atmosphere?
- CFCs released into environment by industry, rises up to stratosphere
- Sunlight breaks CFCs up, releasing Chlorine
- Chlorine reacts with ozone (O3) and destroys Ozone
- More reactions course more depletion
UVC is mostly absorbed by Diatomic oxygen molecules and splits into monatomic oxygen:
O2 + UV —> O + O
UVB is absorbed by ozone and splits this molecule into diatomic oxygen and monatomic oxygen:
O3 + UV —> O2 + O
Monatomic oxygen is very reactive and combines with diatomic oxygen molecule to form ozone, heat is released:
O + O2 —> O3
What is a combination of active processes that cancel out each other’s effects so that there is no overall change?
Dynamic Equilibrium
What are some effects of UVB on living organisms?
Skin cancer
Cataracts
Sunburn
Cuticle damage on plants
What is an example of a halogen that causes ozone depletion in the stratosphere?
Chlorine
What is the history and the properties of CFCs?
CFCs are not natural - artificial and manufactured by humans
Non-flammable, non-toxic, tasteless, odourless and chemically stable
Used in the manufacturing of aerosol sprays, blowing agents for foams, packaging materials, as solvents and as refrigerants
First synthesised in 1928 by Thomas Midgley Jr. of General Motors
Doesn’t dissolve in water
Dissolve oil and greases without damaging electrical parts
Sources of CFCs:
Fridges
Aerosol sprays
Blowing agents for foams
Packing materials
Solvent
What is the Rowland-Molina principle?
Proposed by scientists Mario J. Molina and F. Sherwood Rowland in 1974, suggests that chlorofluorocarbons (CFCs)—commonly used in refrigeration and aerosol products—are the main agents behind ozone layer degradation.
Extra:
CFCs are stable and persistent in the atmosphere
Travel/move to the stratosphere
High energy UV break bonds
Single monoatomic Cl is very reactive
Reaction with O stops the natural formation of O3
Chemistry of the Ozone Layer
Chlorofluorocarbons (CFCs)
Why is ozone depletion greatest at Polar Regions?
Polar vortex winds and polar stratospheric cloud creates very cold conditions.
Cold, dark conditions means Cl is released from ice crystals, destroying the ozone layer (Cl free radicals destroy ozone layer).
What other gases cause ozone depletion?
(Chlorine)
Halogens - e.g Bromine
What is ozone measured in?
Dobson Units
Normal level of ozone is 300 DU
Anything less than 300 DU is considered part of a hole
What are the methods of measuring ozone in the stratosphere?
Satellites measure UV reflection from Earth’s surface - more UV reflection means more UV got through to surface, therefore the worse the conditions of the ozone layer.
Helium balloons / high flying aircraft in stratosphere collecting air samples.
UV detectors at ground level
What are the disadvantages of the methods used to measure ozone in the stratosphere?
Satellites are expensive
UV detectors can only detect UV six months of the year
Balloons are scientific to measure in the stratosphere
What is the Montreal Protocol 1987?
The Montreal Protocol, finalized in 1987, is a global agreement to protect the stratospheric ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS).
Almost every country in the world, agreed and signed.
What did the Montreal Protocol agree to specifically?
Agreed to phase out and ban the use of CFCs
Alternative propellant HCFCs to be banned by 2030
Propellants used today HFCs, propane and butane
Alternatives to aerosols sprays - pump action, trigger spray, roll on/stick deodorant
Safe and regulated disposal of fridges
What has the Montreal protocol achieved?
The Montreal Protocol has been successful in slowing and reversing the increase of ozone-depleting gases (halogen source gases) in the atmosphere.
