Ozone Depletion

Question 1

Reactions between UV radiation and oxygen: UVC

Answer 1

UVC + O2 —> O + O

Question 2

Reactions between UV radiation and oxygen: UVB

Answer 2

UVB + O3 —> O2 + O

Question 3

Reactions between monatomic and diatomic oxygen

Answer 3

O + O2 —> O3 + heat

Question 4

Dynamic equilibrium

Answer 4

a combination of active processes that cancel out each other’s effects so that there is no overall charge

Question 5

Effects of UVB on living organisms

Answer 5

skin cancer, causes cataracts, damages leaf tissue

Question 6

What pollutant gas contains chlorine?

Answer 6

chlorofluorocarbons

Question 7

Properties of CFCs

Answer 7

non - toxic
inflammable

Question 8

History of CFCs

Answer 8

Anthropogenic
Created due to methyl chloride accidents
1974 - discovered that CFCs were responsible for ozone depletion
1987 - 27 nations signed the Montreal Protocol

Question 9

Sources of CFCs

Answer 9

refrigerators
air con
propellants
paints
fire extinguishers

Question 10

What was the Rowland-Molina principle?

Answer 10

1974 paper

CFCs are broken down by UV in stratosphere to form halogen free radicals, which catalytically react with ozone

Question 11

Depletions - Cl

Answer 11

Cl + O3 —> ClO + O2
slows O3 formation

Question 12

Depletions - ClO

Answer 12

ClO + O —> Cl + O2
Cl is released, breaks down more ozone

Question 13

Why is ozone depletion greatest at polar regions?

Answer 13

cold temp
polar vortex winds above poles prevent air from mixing and spreading
stratospheric clouds - contain ice crystals which allow for more reactions that release Cl

Question 14

What other gases cause ozone depletion?

Answer 14

bromine, iodine, fluorine
HCFCs

Question 15

What is ozone measured in?

Answer 15

Dobson Unites (DU)

Question 16

100 DU =

Answer 16

1mm of O3

Question 17

What is the regular level of ozone?

Answer 17

300 DU

Question 18

What level is considered as a hole in the ozone layer?

Answer 18

below 220 DU

Question 19

Atmospheric monitoring - helium balloons/UAVs

Answer 19

samples are collected and analysed from the air

Question 20

Atmospheric monitoring - ground based surveys

Answer 20

measures UV reaching Earth’s surface
more UV = less O3

Question 21

Atmospheric monitoring - satellites

Answer 21

measure reflected UV and re-emitted IR from Earth’s surface

Question 22

What does the Montreal Protocol regulate?

Answer 22

the consumption of ozone depleting substances (ODS)

Question 23

Who was the Montreal Protocol signed by?

Answer 23

all 198 UN member states

Question 24

What was agreed in the Montreal Protocol?

Answer 24

all nations had equal responsibilities (e.g. controlling ODS trade)
timeline of change was longer for less economically developed countries (LEDCs)

Question 25

What has the Montreal Protocol achieved?

Answer 25

over 99% of ODS have been removed from the atmosphere allowing ozone recovery

Question 26

What alternatives are now used instead of CFCs?

Answer 26

trigger and pump action sprays
propellant alternatives - propane, butane HCFCs