- Practice · 5 marks
Water pollution: sources and effects
Short answer
Water pollution is contamination of water bodies by substances harmful to humans and aquatic life. Point sources like sewage and industrial effluents introduce pathogens, organic matter, heavy metals; non‑point runoff adds nutrients and pesticides. Effects include waterborne diseases, oxygen depletion, eutrophication and bioaccumulation of toxics.
Define water pollution. Describe the major sources and types of water pollutants and their effects on human health and aquatic life.
Water pollution is the contamination of water bodies (rivers, lakes, groundwater, oceans) by substances that degrade its quality and make it unfit for its intended use, harming humans and aquatic life.
Sources
- Point sources: discharge from a specific location: sewage outfalls, industrial effluents (tannery, textile, distillery, paper), hospital waste.
- Non-point sources: diffuse runoff from agricultural land (fertilizer, pesticides), urban storm water, mining areas and open dumping.
Types of pollutants and their effects
| Pollutant | Source | Effect |
|---|---|---|
| Pathogens (bacteria, viruses, protozoa) | Untreated sewage, animal waste | Cholera, typhoid, dysentery, hepatitis |
| Oxygen-demanding organic matter | Sewage, food industries | Fall of dissolved oxygen; fish kill; odour |
| Nutrients (N, P) | Fertilizer, detergents, sewage | Eutrophication, algal blooms, nitrate in drinking water (blue baby syndrome) |
| Heavy metals (Pb, Hg, Cd, As) | Mining, batteries, industries | Toxic, bioaccumulate (Minamata, Itai-itai); arsenic in groundwater |
| Toxic organics (pesticides, PCBs) | Agriculture, industry | Cancer, biomagnification in food chains |
| Suspended solids / sediment | Erosion, construction | Turbidity, reduced light, siltation |
| Heat | Power plant cooling water | Lower oxygen solubility, harm to fish |
| Acids / alkalis | Industry, mine drainage | Change of pH, harm to aquatic life |
Water-borne diseases are the main health burden in developing countries; the aquatic ecosystem suffers from oxygen depletion, loss of species and eutrophication.
✓ Answer checked by Claude Opus 5.5 (high effort)
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