Topic 6.2 - Stratospheric Ozone

Question 1

Why does ozone play such a key role in the temperature structure of the Earth’s atmosphere?

Answer 1

WIthout the filter of the ozone layer, more of the Sun’s UV-B radiation would penetrate the atmosphere and reach the Earth’s atmosphere

Question 2

When is UV-B absorbed?

Answer 2

During the formation and destruction of ozone from oxygen

Question 3

How is stratospheric ozone formed?

Answer 3

Sunlight breaks apart one oxygen molecule to produce two oxygen atoms –> each combine with an oxygen to produce an ozone molecule

Question 4

Where is the largest production of ozone and why?

Answer 4

The tropical stratosphere because reactions take place whenever UV-B Is present

Question 5

Why is the ozone hole seasonal?

Answer 5

In Antartic winters there are widespread clouds –> chemical reactions convert less reactive forms of chlorine into large amounts of highly reactive forms

Question 6

What happens when the sun rises at the end of the Southern Hemisphere winter

Answer 6

Degrades reactive gases and releases ‘free radicals’ of chlorine that can catalyze thousands of ozone molecules

Question 7

Why does ozone destruction reduce in the late spring?

Answer 7

The polar vortex weakens –> temperatures rise + fewer clouds –> ozone rich air from lower latitudes mixes back into the polar stratosphere

Question 8

Halogenated organic gases

Answer 8

Stable under normal conditions but liberate halogen atoms when exposed to UV-B in the stratosphere

Question 9

What happens when atoms react with monotomic oxygen

Answer 9

The rate of ozone reformation is slowed

Question 10

What happens when pollutants enhance the destruction of ozone?

Answer 10

The equilibrium is disturbed

Question 11

Give examples of ozone-depleting substances

Answer 11

Chloroflurocarbons - propellants in spray cans, foam, refrigerants

Hydrochloroflurocarbons - replacements for CFCs

Halon - fire extinguishers

Methyl bromide - pesticides

NItrogen oxides - bacterial breakdown of nitrates + nitrates in soil, supreme aircraft

Carbon tetrachloride - cleaning substance

Question 12

How is ozone depleted by CFC’s?

Answer 12

UV radiation breaks off a chlorine atom from CFC molecule

Chlorine atom attacks an ozone molecule, breaks it apart and destroys its ozone

The result is an ordinary oxygen molecule + chlorine monoxide molecule

The chlorine monoxide molecule is attacked by a free oxygen atom

This forms an ordinary oxygen molecule and releases the chlorine atom

The chloine atom is now free to attack and destroy another ozone molecule

Question 13

What is ozone measured in?

Answer 13

Dobson Units

Question 14

How many units of ozone need to be present in an area for sever ozone destruction?

Answer 14

220 DU or more

Question 15

Effects of UV on living organisms

Answer 15

Increase in mutation rates in DNA causing cancer

Can cause eye cataracts

Can damage the ability to carry out photosynthesis in plants and phytoplankton

Reduces primary production and therefore total productivity

Damaged to immune system

Question 16

Effects of UV-B radiation on biological production

Answer 16

Impairs photosynthesis in many species

Over-exposure reduces size, productivity and quality in many crop plants

Over-exposure impairs the productivity of phytoplankton in aquatic ecosystems

UV-B increases plant’s susceptibility to disease

Mutation and damage to photosynthetic organisms

Question 17

Pollution management: altering human activity

Answer 17

Replace gas-blown plastics

Replace old fridges with ‘greenfreeze’ technology

Propane and butane to replace CFC’s as a propellant

Methyl bromide can be replaced with other pesticides

Question 18

Pollution management: Controlling release of pollutants

Answer 18

Recover and recycle CFC’s

Capture CFC’s from scrap car AC units

Ban on production and use of ODs

National legalisation

Policing and enforcement to ensure compliance and stop illegal use of OD’s

Question 19

Pollution management: cleanup and restoration

Answer 19

Add ozone to or remove chlorine from stratosphere

Removals and destruction of existing ODs in the refrigerators and air condition systems

Question 20

What have UNEP’s treaties dealt with in terms of climate change?

Answer 20

Internation trade in harmful chemicals

Air pollution

Contamination of international workshops

1987 –> Montreal Protocol on substance that deplete the ozone layer

Question 21

Why do LEDC’s still demand CFC’s

Answer 21

The reliance of equipment using these chemicals is high

Question 22

Why are there such high rates of illegal trade?

Answer 22

Expense of OD substitues

Expense of updating equipment

Lifetime of CFC conditioning equipment is long

Penalties in small countries are small