Ozone Depletion and Acid Rain
NCERT Class 12 • Biology • Chapter "Environmental Issues" | NCERT Class 11 • Geography • Chapters on the atmosphere
Ozone Depletion and Acid Rain
Two global problems are often confused with global warming but are quite separate. Ozone depletion is the thinning of a protective layer high in the atmosphere, while acid rain is the falling of rain made acidic by pollutants. Each has its own cause and its own cure.
The Ozone Layer and Its Depletion
- The ozone layer lies in the stratosphere and absorbs most of the harmful ultraviolet radiation coming from the sun.
- Ozone in the stratosphere is protective, while ozone at ground level is a pollutant, which is why the same molecule is described so differently.
- Chlorofluorocarbons, used in refrigerators, air conditioners, aerosol sprays and foam, are the main cause of depletion.
- A chlorine atom released from a chlorofluorocarbon molecule can destroy a very large number of ozone molecules before it is removed.
- The ozone hole is the severe seasonal thinning observed over Antarctica, where cold conditions accelerate the reactions.
- Increased ultraviolet radiation causes skin cancer, cataract, weakened immunity and damage to crops and phytoplankton.
- The Montreal Protocol committed countries to phasing out ozone depleting substances and is considered the most successful environmental agreement.
Acid Rain
- Acid rain forms when sulphur dioxide and oxides of nitrogen dissolve in atmospheric moisture to make sulphuric and nitric acid.
- The main sources are coal burning power plants, industry and vehicle exhaust.
- Rain with a pH below about 5.6 is considered acidic.
- It damages crops and forests by harming leaves and by leaching nutrients out of the soil.
- It acidifies lakes and rivers, killing fish and other aquatic life.
- It corrodes buildings and monuments, and marble structures are especially vulnerable.
- Control means reducing sulphur and nitrogen emissions through cleaner fuel, scrubbers and better combustion technology.
- Adding lime to acidified lakes and soil can partly neutralise the damage already done.
| Problem | Cause | Main Effect |
|---|---|---|
| Ozone depletion | Chlorofluorocarbons | More ultraviolet radiation reaching earth |
| Acid rain | Sulphur and nitrogen oxides | Damage to crops, lakes and monuments |
| Global warming | Greenhouse gases | Rising average temperature |
Ozone hole — the severe seasonal thinning of the ozone layer observed over Antarctica.
Exam me kaise aata hai
- Which chemicals mainly destroy the ozone layer — chlorofluorocarbons
- The ozone hole is observed over — Antarctica
- Acid rain is caused by — sulphur dioxide and oxides of nitrogen
- The agreement to phase out ozone depleting substances is the — Montreal Protocol
UPSC/State PSC ke liye
- The Montreal Protocol succeeded because the number of substances was small, substitutes existed, and the harm was clearly established, conditions that climate negotiation does not enjoy.
- Acid rain is a transboundary problem: emissions in one country fall as acid rain in another, which is why it needs regional agreement.
Yahan confuse hote hain
✗ Ozone depletion causes global warming | They are separate problems with different causes | ✓
✗ Ozone is always harmful | Stratospheric ozone protects us; ground level ozone is a pollutant | ✓
✗ Acid rain only affects the place where the pollution is released | It is carried by wind and falls far away | ✓
Ek nazar me
- The ozone layer absorbs harmful ultraviolet radiation.
- Chlorofluorocarbons destroy it, and the ozone hole appears over Antarctica.
- The Montreal Protocol phased out ozone depleting substances.
- Acid rain comes from sulphur and nitrogen oxides and damages crops, lakes and monuments.