6.2 Stratospheric Ozone

What type of radiation is emitted from the sun?

UV

Where is ozone found?

Stratosphere

What is ozone’s role?

Protects life on earth by absorbing sun’s harmful UV radiation

How does ozone undergo natural destruction and reformation?

• UV radiation breaks O3 info O2 and O

• Free O atom combines with O2 to reform O3

• Process creates dynamic equilibrium, maintaining stable ozone levels

What is a dynamic equilibrium in the ozone cycle?

Balance between ozone destruction and reformation, where rates of processes both equal

What are ozone-depleting substances (ODSs)?

Chemicals that break down ozone molecules, thinning ozone layer

List some human activities and products using ODSs

• Aerosols: CFCs in sprays and deodorants

• Gas-blown plastics: ODSs in foamed plastic production

• Pesticides: methyl bromide in soil fumigation

• Flame retardants: halogenated compounds in products

• Refrigerants: CFCs and HCFCs in cooling systems

How do ODSs contribute to ozone depletion?

ODSs release halogen atoms (chlorine/bromine) into stratosphere

Halogen atoms destroy ozone molecules in cycle, thinning ozone layer

What are the consequences of ozone layer thinning?

Increased UV radiation reaches Earth’s surface, harming living organisms

What are the effects of UV radiation on humans?

• Cataracts: clouding of eye lens, causing blurry vision

• Skin cancer: DNA damage in skin cells, leading to tumours

• Sunburn: inflammatory response causing redness, pain and blisters

• Premature skin aging: breaks down collagen, wrinkles and sagging

How does UV radiation damage DNA?

• Induces mutations during cell division

• Causes genetic alteration in skin cells, increasing cancer risk

How can UV-related health risks be minimised?

• High SPF sunscreen

• UV-blocking sunglasses

• Seek shade during peak hours

• Protective clothing

• Regular skin and eye check-ups

How does UV-radiation affect biological productivity?

• DNA damage and reduced photosynthesis

• Decreased primary productivity in aquatic ecosystems

• Disruption of nutrient cycling and food webs

Why are phytoplankton important?

• Convert sunlight, CO2 and nutrients into organic matter

• Support food webs and nutrient cycling

• Reduced phytoplankton impacts zooplankton, fish and marine animals

What are the ecosystem impacts of reduced phytoplankton productivity?

• Imbalances in nutrient cycling

• Decreased food availability for higher trophic levels

• Disruption of aquatic ecosystems stability

How does ozone layer depletion affect aquatic ecosystems?

Depletion increases harmful UV radiation, am-lifting damage to photosynthetic organisms and ecosystem dynamics

What actions can mitigate UV radiation’s effects?

• Reduce human activities causing ozone depletion

• Preserve phytoplankton health to maintain ecosystem balance

How can the manufacture and release of ozone-depleting substances be reduced?

1. Recycling refrigerants: properly collecting, purifying and reusing refrigerants reduces need for new production - replace ODSs refrigerants with “green freeze” technology (propane/butane)

2. Gas-blown plastics: develop alternatives to foaming agents that use ODS

3. Halogenated particles: replace with organic or environmentally friendly alternatives (e.g. use organic pest control instead of methyl bromide)

4. Aerosols: use non-propellant alternatives like pump sprays/soap bars instead of shaving foam

What is the role of UNEP in ozone protection?

• Raises awareness of ozone depletion, its causes and impacts

• Conducts research and shares information with governments, industries and public

• Creates and evaluates international agreements to reduce ODS use

What is the Montreal Protocol?

• 1987 international agreement under UNEP to reduce ODS production and emissions

• Updated with amendments to reflect scientific and technological advancement

• Signed by 24 countries initially, now 197 countries

What are the achievements of the Montreal Protocol?

• Reduced ODS emissions from 1.5 million tonnes in 1987 to 400,000 tonnes in 2010

• Aims to end HCFC production by 2040

What challenges remain in protecting the ozone layer?

1. Illegal trade: persistent black markets for ODS (UNEP collaborates with national authorities to monitor and enforce compliance)

2. National implementation: government enact laws to reduce CFCs and promote ozone-friendly alternatives

What is the collective role of stakeholders in ozone protection?

UNEP, governments, industries and other stakeholders collaborate to:

• Enforce reduction targets

• Mitigate illegal ODS trade

• Foster global cooperation for sustainable ozone protection