The Phosphorus Cycle
Introduced| English |
|---|
| phosphate/ˈfɒsfeɪt/ |
| weathering/ˈweðərɪŋ/ |
| sediment/ˈsedɪmənt/ |
The slow cycle
- Phosphorus is essential for DNA, cell membranes, and bones.
- But unlike carbon and nitrogen, it has no gas form.
- So it cannot travel through the air.
- Instead it moves slowly through rock, soil, water, and life.
Locked in rock
- Most of Earth's phosphorus is stored in rocks as phosphate.
- There is essentially no phosphorus in the atmosphere.
- This is the key difference from the carbon and nitrogen cycles.
- The rock store is huge but hard to reach.
How is the phosphorus cycle different from the carbon and nitrogen cycles?
Phosphorus has no gas phase — it cycles through rock, soil, water, and living things only.
Where is most of Earth's phosphorus stored?
Most phosphorus is locked in rocks as phosphate, released slowly by weathering.
Weathering frees it slowly
- Weathering 风化 slowly breaks down rock over long ages.
- This releases phosphate 磷酸盐 into the soil and water.
- Plants absorb the phosphate through their roots.
- Because weathering is slow, phosphorus is often in short supply.
The phosphorus cycle
Step around the cycle - unlike carbon and nitrogen, phosphorus has no gas phase and moves very slowly.
The slow breakdown of rock that releases phosphate into soil is called ____.
Weathering slowly frees phosphate from rock so living things can use it.
Through life and back to sediment
- Plants use phosphorus to build DNA and membranes; it passes up the food chain.
- Decomposers return it to the soil when things die.
- Runoff carries phosphate to the sea, where it settles as sediment 沉积物.
- Over millions of years the sediment forms new rock, restarting the cycle.
The phosphorus cycle is much slower than the carbon or nitrogen cycles.
With no fast gas phase, phosphorus cycles slowly through rock and sediment over long ages.
Select all true statements about the phosphorus cycle.
There is essentially no phosphorus in the air. The other three are correct.
The phosphorus cycle has no gas phase — the single biggest way it differs from the carbon and nitrogen cycles. Because it moves only through rock, soil, and water, it is very slow, so phosphorus is often the nutrient that limits how much a plant can grow.
Why fertiliser adds phosphorus:
- Natural weathering releases phosphate too slowly for fast-growing crops.
- Farmers mine phosphate rock and add it as fertiliser.
- This speeds up the slow cycle — but excess phosphate washing into rivers can cause serious pollution.
The phosphorus cycle has no gas phase, so it moves slowly through rock, soil, water, and life. Most phosphorus is stored in rock as phosphate and released by weathering. Plants take it up, it passes through the food chain, and runoff returns it to ocean sediment that slowly becomes new rock.