Phosphorus cycle
The phosphorus cycle or phosphorus cycle is the constant migration and biogeochemical conversion of the bio-element phosphorus in water , in soils and in biomass .
background
The phosphor is present in all living organisms to a central part, in terms of quantity, in particular in phospholipids of all membranes of the cellular and intracellular level, but also as an essential part of the DNA , whereby it in phosphate form, as well as adenosine triphosphate (ATP) for energy conversions . Some marine plankton organisms such as cyanobacteria have replaced phospholipids with other lipids due to a lack of phosphate. Its outstanding importance makes phosphorus an essential nutrient for all living things. Although ubiquitous in nature in low concentrations , phosphorus is a non-renewable resource . The global deposits are limited, phosphate-rich minerals are concentrated in only a few countries.
As mentioned, phosphorus is ubiquitous in the environment, but depending on the location, its concentration (content) can be so low that plant growth is restricted. The law of the minimum applies , according to which growth depends on the scarcest plant nutrients available . The use of mineral and organic fertilizers increases the phosphorus content in the soil and thus the growth.
About 90 percent of global phosphorus production is used as fertilizer in agriculture ; Phosphorus is therefore of enormous importance for today's highly industrialized production of agricultural goods . However, the previous phosphorus mining sites will probably only be able to satisfy the continued high demand for a few years, probably until around 2020. A possible peak phosphorus scenario - analogous to peak oil - is forecast.
Origin of phosphorus
Phosphorus finds its origin in neutrino sources in the cosmos, which are supernovae . In the center of which had been hydrogen to helium , this to carbon and oxygen , and this to silicon , phosphorus and sulfur , and finally to iron , cobalt and nickel fused , which finally led to the collapse of the star within milliseconds.
Bring phosphorus into the cycle as phosphate
The element phosphorus is only bound, almost without exception as phosphate , introduced into the terrestrial cycle. When it comes to the origin and implementation of phosphorus, two sources have to be separated:
- Natural sources such as organic fertilizers, plant residues, sediments, etc.
- Anthropogenic introduction, especially through fertilizers of mineral origin.
The implementation from natural sources is estimated at 3 megatons per year (Mt / a). In addition, since the beginning of industrial fertilizer production, large amounts of phosphorus have been applied by humans, estimated at 12 Mt / a since the 1950s. Today's input is even estimated at 14 Mt / a. The anthropogenic input therefore corresponds to four to five times the natural mobilization.
Phosphorus occurs naturally as a phosphate-rich mineral - mostly as apatite . The weathering of these phosphate rocks is the most important natural source of phosphorus. As an anthropogenic source, these rocks are mined in places with a very high phosphate content and, after appropriate processing, used as mineral fertilizer and thus introduced into the phosphate cycle.
Transport of phosphorus
Phosphorus is found in the environment as phosphate, usually in a solid, liquid or dissolved state. The only naturally occurring gaseous phosphorus compound is phosphine , but its proportion is negligible in the entire phosphorus cycle. However, the transport of phosphorus in soil particles through wind erosion is important. Dissolved phosphorus and phosphorus contained in soil or rock particles is transported naturally via erosion, mainly via rivers. Phosphorus is also introduced into the cycle through the tectonic uplift of rock and its weathering.
A large part of the separated phosphorus is fed back into the phosphorus cycle through fertilization in agriculture. In addition to organic sources such as liquid manure , plant residues or manure , mineral fertilizers are particularly important. The use of guano is no longer relevant today.
In the waters production depends on biomass usually directly related to the available amount of phosphorus. The increase in phosphorus input in lakes therefore leads to eutrophication . The condition of lakes is often assessed according to their “nutrient content” and the resulting growth of algae ; in fact, it is the available phosphorus content. Phosphorus also plays an important eutrophic role in rivers. That is why today phosphorus is removed in sewage treatment plants by various processes ( phosphorus elimination ), whereby the recovery of phosphorus or phosphates - due to the finite nature of their natural resources - is becoming increasingly important.
Implementation of phosphorus
Phosphates are converted very quickly in plants and animals. However, the processes that move phosphates across soils or seas are very sluggish, which makes the phosphorus cycle one of the slowest biogeochemical cycles. Phosphorus that has been brought into the soil via natural or anthropogenic sources is converted in the form of phosphate. In order to be available to plants, there must be a dissolved orthophosphate ion that can be taken up via the roots. If the phosphate is in other organic and inorganic forms, it is not available to plants . These phosphorus pools are in dynamic equilibrium with one another.
Lowering in the phosphorus cycle
Organic compounds, authigenic phosphorus, sediments and bound phosphorus complexes, in particular with calcium carbonate, iron or manganese , occur as sinks in the phosphorus cycle .
See also
credentials
- ↑ Benjamin AS Van Mooy, Helen F. Fredricks, Byron E. Pedler, Sonya T. Dyhrman, David M. Karl, Michal Koblížek, Michael W. Lomas, Tracy J. Mincer, Lisa R. Moore, Thierry Moutin, Michael S. Rappé, Eric A. Webb: Phytoplankton in the ocean use non-phosphorus lipids in response to phosphorus scarcity. In: Nature , Vol. 458, No. 7234, March 2009, pp. 69-72.
- ^ Dana Cordell, Stuart White: Sustainable phosphorus measures: Strategies and technologies for achieving phosphorus security . In: Agronomy , Vol. 3, No. 1, March 2013, pp. 86–116, (PDF) , accessed on February 15, 2020.
- ↑ D. Cordell, J.-O. Drangert, S. White: The story of phosphorus: Global food security and food for thought. In: Global Environmental Change. Vol. 19, 2009, pp. 292-305 (English).
- ^ A b D. Cordell: The Story of Phosphorus. Dissertation. Linköpings universitet , Linköping 2010 (English).
- ↑ Martina Davids: Neutrino sources in the cosmos: Supernovae . Neutrino Seminar, RWTH Aachen University, WS2003 / 2004, November 24, 2003, (PDF) , viewed February 16, 2020.
- ↑ P. Falkowski, RJ Scholes, E. Boyle, J. Canadell, D. Canfield, J. Elser, N. Gruber, K. Hibbard, P. Högberg, S. Linder et al. (2000). The Global Carbon Cycle: A Test of Our Knowledge of Earth as a System. Science , 290, pp. 291-296.
- ^ "Before the fertilizer runs out - Phosphorus recycling should secure world food", Spektrumdirekt, March 9, 2010; Abstract .
- ^ KB Föllmi (1996). The phosphorus cycle, phosphogenesis and marine phosphate-rich deposits. Earth-Science Reviews, 40, pp. 55-124.