Phosphorus cycle

The phosphorus cycle and phosphorus cycle is the biogeochemical steady migration and implementation of the biomember phosphorus in the aquatic environment, in soil and in biomass.

Background

The phosphorus comes in all living things play a central role, particularly as a component of ATP in energy conversion and as a component of DNA. In this case, phosphorus is present in the form of phosphate. His outstanding importance makes it an essential nutrient. Although ubiquitous in nature occurring at low concentrations, phosphorus is considered to be non-renewable resource. The global resources are limited and concentrated in a few countries.

Phosphorus is ubiquitous in the environment, but can be as low concentration in Abhängingigkeit the site that it limits the growth of plants. Here, the Liebig's law or Law of the Minimum applies after which the growth is determined by the scarcest nutrient. By the use of mineral fertilizers and organic manure, the content of phosphorus in the soil and so that the growth is increased. Approximately 90 % of the global phosphorus production are used as agricultural fertilizer use, where they are of enormous importance for the production of agricultural goods. The scarcity of the remaining phosphorus and the enormous importance as a fertilizer could greatly increase the future demand for phosphorus. A possible peak Phosphorus scenario, analogous to Peak Oil is predicted here.

The phosphorus cycle

Origin of phosphorus

In the origin and implementation of phosphorus it is important to separate two sources:

• Natural sources, such as organic manure, crop residues, sediments, etc.
• Anthropogenic contribution, particularly through fertilizer.

The conversion from natural sources is estimated to be 3 megatons per year ( Mt / a). In addition, since the beginning of the industrial fertilizer production large quantities of phosphorus discharged from the people that are estimated to be 12 Mt / a since the 1950s. The anthropogenic contribution thus corresponds to 4 times the natural mobilization. Today's contribution is even estimated to be 14 Mt / a.

Phosphorus is in the nature as phosphate- rich mineral - mostly as apatite - before. The weathering of phosphate rocks is the most important natural source of phosphorus. As anthropogenic source of these rocks are mined in places with a very high phosphate content and used after appropriate treatment as a mineral fertilizer and thus introduced into the phosphate cycle.

Transport of phosphorus

Phosphorus is in the environment as phosphate. This is essentially limited to solid or liquid or dissolved state. The only naturally occurring gaseous phosphorus compound is phosphine, but its proportion in the total phosphorus cycle is negligible. Of importance, however, is the transport of phosphorus in soil particles by wind erosion. And dissolved phosphorus contained in the soil or rock particles phosphorus is transported in a natural way on the discharge mainly by rivers. Phosphorus is also introduced into the circuit via the tectonic elevation of rock and their weathering.

The fertilizers in modern agriculture, a large part of the incorporated phosphorus is introduced into the cycle today. Here are the one hand, organic sources like manure, crop residues, manure, and mineral matter. The use of guano is negligible today.

In the waters biomass production is often related directly to the amount of available phosphorus. Therefore, increases in phosphorus discharges into lakes lead to eutrophication. In general, do you judge the condition of lakes according to their " nutrient content " and its consequences for the growth of algae, and thinks practically always available phosphorus content. Even in the rivers phosphorus plays an important role eutrophication. Therefore, it is now removed in sewage treatment plants phosphorus by various methods ( phosphorus removal ), the recovery of phosphorus and phosphates - gains more and more importance - because of the finite nature of natural resources.

Reaction of phosphorus

Phosphates are implemented very quickly in plants and animals. The processes move the phosphates about soils or oceans, but are very slow, making the phosphorus cycle to one of the slowest biogeochemical cycles. Phosphorus, which was introduced to the ground via natural or anthropogenic sources, is implemented in the form of phosphate. In order to be available for plants, a dissolved orthophosphate must be present, which can be absorbed through the roots. If the phosphate in other organic and inorganic forms, it is not available to plants. These phosphorus pools each other in a dynamic equilibrium.

Sinks in the phosphorus cycle

As sinks in the phosphorus cycle occur in particular organic compounds, authigenic phosphorus, sediment and phosphorus bound complexes especially with calcium, iron or manganese.