Pollution of Air and Water
Focused last-minute revision notes with clear concepts, exam traps, key comparisons and compact practice.
Chapter Snapshot
- Pollution is harmful change in environmental quality due to contaminants or excessive energy.
- Major air pollutants include particulate matter, carbon monoxide, sulphur dioxide and nitrogen oxides.
- Smog forms when pollutants mix with fog or undergo atmospheric reactions.
- Sulphur and nitrogen oxides can contribute to acid rain.
- Greenhouse gases trap heat; increased greenhouse-gas concentrations contribute to global warming.
- Water pollution comes from sewage, industrial discharge, farm runoff, plastics and other wastes.
- Potable water is safe for drinking and must meet quality standards.
- Water treatment commonly includes sedimentation, filtration and disinfection, but methods depend on contamination.
- Preventing pollution is usually better and cheaper than cleaning it afterward.
What You Will Learn
- Define air and water pollution
- Identify major air pollutants and sources
- Explain smog, acid rain and greenhouse effect at Class 8 level
- Identify major water pollutants
- Explain potable water and basic treatment
- Suggest practical pollution-control measures
Last-Minute Chapter Map
Pollution control works best when contaminants are prevented or treated before they enter air or water.
1. Air Pollution
Air pollution occurs when harmful substances are present in air at levels that damage health, organisms, materials or ecosystems. Sources include vehicles, industries, burning fuels, construction dust, fires and open waste burning.
2. Important Air Pollutants
Carbon monoxide reduces the blood’s ability to carry oxygen. Sulphur dioxide and nitrogen oxides irritate the respiratory system and contribute to acid rain. Fine particulate matter can penetrate deep into lungs. Ground-level ozone is another harmful pollutant formed through atmospheric reactions.
3. Smog and Acid Rain
Smog is polluted air containing suspended particles and gases; some forms involve fog, while photochemical smog forms through sunlight-driven reactions. Acid rain develops when sulphur and nitrogen oxides form acidic substances in the atmosphere, damaging lakes, soil, vegetation and buildings.
4. Greenhouse Effect and Global Warming
The natural greenhouse effect keeps Earth warm enough for life. Increasing concentrations of gases such as carbon dioxide and methane strengthen heat trapping and contribute to global warming and climate change.
5. Water Pollution
Water becomes polluted when sewage, industrial chemicals, agricultural runoff, pathogens, plastics or other wastes reduce its quality. Polluted water can spread disease, kill aquatic organisms and reduce dissolved oxygen.
6. Potable Water and Treatment
Potable water is water safe for drinking. Treatment may include screening, sedimentation, filtration and disinfection. Boiling can kill many pathogens at home, but it does not remove every chemical contaminant, so source quality still matters.
7. Prevention and Control
Use cleaner fuels and public transport, maintain vehicles, control industrial emissions, avoid burning waste, treat sewage and industrial effluent, reduce fertiliser runoff, conserve water and dispose of chemicals responsibly. Preventing pollution at source is most effective.
Air vs Water Pollution
| Feature | Air Pollution | Water Pollution |
|---|---|---|
| Common sources | Vehicles, fuel burning, industry, dust | Sewage, industry, farm runoff, waste |
| Major effects | Respiratory disease, smog, acid rain | Disease, ecosystem damage, oxygen depletion |
| Control focus | Cleaner transport/fuels and emission control | Wastewater treatment and source protection |
Exam Focus
Must Revise Before the Exam
- Air pollution sources
- CO, SO2, NOx, particulates
- Smog
- Acid rain
- Greenhouse effect/global warming
- Water pollution sources
- Potable water
- Basic water treatment
- Prevention measures
Common Mistakes
Key Terms
Key Terms
Quick Revision
Quick Revision
- Air pollution can come from transport, industry, burning and dust.
- CO is poisonous; SO2 and NOx contribute to acid rain.
- Fine particulate matter harms lungs.
- Greenhouse effect is natural, but extra greenhouse gases increase warming.
- Water pollution comes from sewage, industry, farming and waste.
- Potable water is safe for drinking.
- Treatment often uses sedimentation, filtration and disinfection.
- Boiling does not remove all chemicals.
- Prevent pollution at source whenever possible.
Practice Questions
Which pollutant reduces blood oxygen-carrying ability?
A. carbon monoxide
B. oxygen
C. nitrogen
D. water vapour
View Solution
Correct Answer: A. carbon monoxide
Carbon monoxide binds strongly with haemoglobin.
Acid rain is strongly linked with emissions of:
A. sulphur dioxide and nitrogen oxides
B. helium and neon
C. oxygen and argon
D. water vapour only
View Solution
Correct Answer: A. sulphur dioxide and nitrogen oxides
SO2 and NOx can form acidic compounds in the atmosphere.
Water safe for drinking is called:
A. saline
B. potable
C. distilled only
D. opaque
View Solution
Correct Answer: B. potable
Potable means safe for drinking.
Which is the best first strategy for pollution control?
A. dilute pollution after release
B. prevent pollutants at source
C. burn waste openly
D. ignore small sources
View Solution
Correct Answer: B. prevent pollutants at source
Prevention at source is generally more effective than later cleanup.
How does acid rain form?
View Solution
Sulphur dioxide and nitrogen oxides react in the atmosphere to form acidic substances that return to the surface in rain, snow or dry deposition.
Why is boiling not enough for every polluted water source?
View Solution
Boiling kills many disease-causing organisms but does not remove dissolved toxic chemicals, heavy metals or all other pollutants.
Suggest three actions a city can take to reduce air pollution.
View Solution
Improve public transport and vehicle emission control, manage construction dust, shift to cleaner fuels/energy, control industrial emissions and stop open waste burning. Any three well-explained actions are suitable.
Chapter Summary
Chapter Summary
- Air pollution can come from transport, industry, burning and dust.
- CO is poisonous; SO2 and NOx contribute to acid rain.
- Fine particulate matter harms lungs.
- Greenhouse effect is natural, but extra greenhouse gases increase warming.
- Water pollution comes from sewage, industry, farming and waste.
- Potable water is safe for drinking.
- Treatment often uses sedimentation, filtration and disinfection.
- Boiling does not remove all chemicals.
- Prevent pollution at source whenever possible.