Water pollution and eutrophication
| English | Chinese | Pinyin |
|---|---|---|
| eutrophication | 富营养化 | fù yíng yǎng huà |
| nitrates | 硝酸盐 | xiāo suān yán |
| algae | 藻类 | zǎo lèi |
| algal bloom | 藻华 | zǎo huá |
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:
Extra nitrates trigger the process.
The extra nutrients cause a rapid growth of:
Nitrates feed an algal bloom.
A rapid surface growth of algae from excess nutrients is an algal ______.
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:
Decomposers use up the oxygen.
Put the eutrophication steps in order.
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