Phosphorus cycle
From Wikipedia, the free encyclopedia
A phosphorus cycle is the biogeochemical cycle that describes the movement of phosphorus through the lithosphere, hydrosphere, and biosphere. Unlike many other biogeochemical cycles, the atmosphere does not play a significant role in the movements of phosphorus, because phosphorus and phosphorus-based compounds are usually solids at the typical ranges of temperature and pressure found on Earth.
[edit] Phosphorus in the environment
Phosphorus is an essential nutrient for plants and animals in the form of ions PO43- and HPO42- . It is a part of DNA-molecules, of molecules that store energy (ATP and ADP) and of fats of cell membranes. Phosphorus is also a building block of certain parts of the human and animal body, such as the bones and teeth.
Phosphorus normally occurs in nature as part of a phosphate ion, consisting of a phosphorus atom and some number of oxygen atoms, the most abundant form (called orthophosphate) having four oxygens: PO43-. Most phosphates are found as salts in ocean sediments or in rocks. Over time, geologic processes can bring ocean sediments to land, and weathering will carry terrestrial . Plants absorb phosphates from the soil. The plants may then be consumed by herbivores who in turn may be consumed by carnivores. After death, the animal or plant decays, and the phosphates are returned to the soil. Runoff may carry them back to the ocean or they may be reincorporated into rock.
The primary biological importance of phosphates is as a component of nucleotides, which serve as energy storage within cells (ATP) or when linked together, form the nucleic acids DNA and RNA. Phosphorus is also found in bones, whose strength is derived from calcium phosphate, and in phospholipids (found in all biological membranes).
Phosphates move quickly through plants and animals; however, the processes that move them through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest biogeochemical cycles.
However, recent findings suggest that phosphorus is cycled through the ocean on the timescale of 10,000yr, suggesting that the phosphorus cycle may play a role in global warming.
Unlike other cycles of matter compounds, phosphorus cannot be found in air as a gas. This is because at normal temperature and circumstances, it is a liquid. It usually cycles through water, soil and sediments. In the atmosphere phosphorus is mainly small dust particles.
Phosphorus is one of the longest cycles, and takes a long time to move from sediments to living organisms and back to sediments.
[edit] References
- Part III of "Matter cycles": The phosphorus cycle, Lenntech Water treatment & air purification, Holding B.V. 2006
- Environmental Literacy Council - Phosphorus Cycle
- Monitoring and assessing water quality, section 5.6 Phosphorus - EPA
| Biogeochemical cycles |
|---|
| Carbon cycle - Hydrogen cycle - Nitrogen cycle |
| Oxygen cycle - Phosphorus cycle - Sulfur cycle - Water cycle |
