The Problem of Ozone Depletion: Causes and Solutions
Causes of Ozone Depletion:
- Ozone depletion occurs primarily in the stratosphere, where high levels of certain compounds contribute to the problem.
- The depletion of ozone is mainly caused by the release of human-made chemicals, known as ozone-depleting substances (ODS), into the atmosphere.
Specific Compounds Responsible for Ozone Depletion:
The correct answer choice is D: Chlorine and Bromine. These compounds are primarily responsible for the depletion of ozone in the stratosphere. Here's why:
1. Chlorine:
- Chlorine is released into the atmosphere through the use of chlorofluorocarbons (CFCs), such as CFC-11 and CFC-12, which were commonly used in refrigeration, air conditioning, and aerosol propellants.
- Once released, CFCs can remain in the atmosphere for several decades.
- In the stratosphere, CFCs are broken down by ultraviolet (UV) radiation, releasing chlorine atoms.
2. Bromine:
- Bromine is released into the atmosphere through the use of halons, such as halon-1211 and halon-1301, which were commonly used in fire extinguishers and fire suppression systems.
- Similar to CFCs, halons can also remain in the atmosphere for an extended period.
- In the stratosphere, halons are broken down by UV radiation, releasing bromine atoms.
Impact of Chlorine and Bromine on Ozone:
- Both chlorine and bromine atoms are highly reactive and can catalytically destroy ozone molecules.
- When released into the stratosphere, these atoms can continuously break down ozone molecules, leading to a reduction in the ozone layer's thickness.
- The loss of ozone in the stratosphere allows more harmful ultraviolet-B (UV-B) radiation from the sun to reach the Earth's surface, posing serious health and environmental risks.
Solutions to Ozone Depletion:
- The international community recognized the seriousness of the ozone depletion problem and took action to address it.
- The Montreal Protocol, adopted in 1987, is an international treaty that aimed to phase out the production and use of ODSs.
- As a result of the protocol, the production and consumption of most ODSs, including CFCs and halons, have been significantly reduced.
- The ozone layer has shown signs of recovery, and it is expected to fully recover by the middle of the 21st century if the protocol's provisions are upheld.
In conclusion, the problem of ozone depletion in the stratosphere is primarily caused by high levels of chlorine and bromine compounds. These compounds, released from human activities, can catalytically destroy ozone molecules, leading to the thinning of the ozone layer. However, international efforts, such as the Montreal Protocol, have been successful in reducing the production and use of ozone-depleting substances, offering hope for the recovery of the ozone layer.