Water pollution and eutrophication
Introduced| English | Meaning |
|---|---|
| eutrophication/ˌjuːtrəfɪˈkeɪʃn/ | Nutrient enrichment of water that can cause excessive plant or algal growth and oxygen depletion as organic matter decomposes. |
| nitrates/ˈnaɪtreɪts/ | A compound containing the nitrate ion, NO3 with a single negative charge. |
| algae/ˈælɡiː/ | A diverse group of mainly aquatic photosynthetic organisms that lack the true roots, stems and leaves of plants. |
| algal bloom/ˈælɡl bluːm/ | A rapid increase in the abundance of algae or similar photosynthetic microorganisms in a body of water. |
When fertiliser poisons a river
- Fertilisers help crops grow — but washed into rivers and lakes, they can kill the life there.
- This damaging chain of events is eutrophication 富营养化.
Eutrophication sequence
Follow fertiliser runoff from nutrient input to fish death.
Eutrophication is usually started by:
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Extra nitrates trigger the process.
The extra nutrients cause a rapid growth of:
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Nitrates feed an algal bloom.
A rapid surface growth of algae from excess nutrients is an algal ______.
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The bloom blocks light and starts the harm.
The cause
- Fertiliser (or sewage) runs off into water, adding lots of nitrates 硝酸盐.
- These nutrients make algae 藻类 grow rapidly, covering the surface — an algal bloom 藻华.
Eutrophication: extra fertiliser makes algae bloom, then the water loses its oxygen and fish die
Fish die in eutrophication because the water loses its:
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Decomposers use up the oxygen.
Put the eutrophication steps in order.
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Nitrates → bloom → plants die → oxygen used up → fish die.
The chain of harm
- The algal bloom blocks light, so plants below die.
- Decomposers break down the dead plants, and their respiration uses up the oxygen.
The result
- With little oxygen left, fish and other animals die.
- This is eutrophication — fertiliser pollution suffocating a waterway.
Worked example. Fertiliser washes into a lake → nitrates feed an algal bloom → light is blocked, plants die → decomposers use up the oxygen → fish suffocate. Each step follows from the last.
You've got it
- eutrophication: nitrates (fertiliser/sewage) cause an algal bloom
- the bloom blocks light (plants die); decomposers then use up oxygen
- with no oxygen, fish and animals die — the water is polluted