The phosphorus cycle

Phosphorus is one of the most important chemical elements involved in the development of living organisms. It is a part of the protoplasm and most of the animal and vegetable proteins. Human phosphorus is vital for the full development of organs and tissues, as well as to ensure normal brain function. No wonder Academician AE Fersman called it an element of life and thought.

The phosphorus cycle in the biosphere consists of several main links - rocks, soil, plants and animal organisms. The source of most phosphorus-containing compounds in nature is the apatite mineral, which contains from 5 to 36% of phosphorus oxide. Crystals of apatite occur in igneous rocks and in places where they come into contact with sedimentary rocks. Significant reserves of this mineral are found in Brazil and Norway, and the largest deposit is in the Khibiny (Kola Peninsula).

In the process of weathering, occurring under the influence of atmospheric conditions, soil acids, living organisms, apatites are destroyed and are involved in the biochemical cycle of phosphorus, covering the bio-, hydro- and lithosphere.

Plants absorb the phosphate anions from the dissolved phosphates and accumulate the element mainly in generative organs - fruits and seeds. Different parts of plants are eaten by animals and people, and the cycle of phosphorus continues.

In any animal organism, physiological processes are constantly occurring, connected with the splitting, synthesis and other chemical transformations of phosphorus-containing compounds. In mammals, this element is found in proteins of blood, milk, nervous, bone and brain tissues. It is also present in the composition of nucleic acids - compounds involved in the processes of transmission of hereditary information. After the death of animal organisms, the phosphorus cycle closes - the element returns to the lithosphere, dropping out of the biochemical cycle. Under certain conditions (for example, with a sharp change in climatic conditions, fluctuations in salinity, temperature, acidity of water, etc.), there is a mass death of organisms and the accumulation of their residues on the seabed. As a result, new deposits of phosphorus-containing rocks of sedimentary origin (for example, phosphorites) are formed. Over time, organogenic rocks - bioliths - become a new source of this element in the biogenic cycle.

As in all the cycles of substances in nature, a person energetically interferes with this process. Phosphorus and its compounds are used in metallurgy, chemical industry, in the production of detergents, matches and drugs. But the main consumer of phosphates is agriculture. This element is necessary for plants to fully flowering and fruiting, it increases winter hardiness and participates in the development of the root system. But on cultivated soils, the phosphorus reserve is gradually depleted, which makes it necessary to introduce fertilizers, for the production of which the same phosphorites and apatites are used.

Thus, new links of anthropogenic character - industry and agriculture - are included in the cycle of phosphorus. Human activities are aimed at increasing the concentration of this element in the environment. This phenomenon, called by scientists the phosphatization of land, is due to the harvest of seafood and the extraction of phosphorus-containing minerals with subsequent use in various branches of the agro-industrial complex. The most intense phosphatization occurs in industrially developed regions with a high population density. In sparsely populated areas and in the areas of extraction of apatite and phosphorite, on the contrary, dephosphatization occurs.