Biosphere processes. The nitrogen cycle in nature

A chemical element with atomic number seven is designated by the symbol N (Nitrogenium). Its name - "zot" - from Ancient Greek is translated as "lifeless". This term, according to one of the theories of its occurrence, was proposed by Antoine Lavoisier in 1787, instead of the preceding "flogged", "spoiled" and "mephitic" air. It was then that a group of French scientists, in whose work Lavoisier took an active part, was engaged in the development of the principles of chemical nomenclature. Even then, the property of nitrogen was not observed to support neither burning nor breathing.

According to another version, the word "nitrogen" was invented not by Lavoisier and his colleagues. It was found in the alchemical literature at the dawn of the Middle Ages to denote the so-called "primary matter of metals", and it was attributed, no less, to the "alpha and omega" property of everything.

In nature, nitrogen can be contained as a simple substance with formula N2, it is a fairly inert gas without taste, color and odor. Three quarters of the earth's atmosphere consists of nitrogen. This element plays a very important role in the existence of plants and animals. In the composition of proteins, its percentage is 16-18% by weight. It also enters the structure of nucleic acids, nucleoproteins, amino acids, chlorophyll, hemoglobin. In living cells, in terms of the number of atoms, nitrogen occupies about 2%, and in the mass fraction this index increases to 2.5%. Element N occupies the fourth place in importance after the main elements of organic chemistry - hydrogen, carbon and oxygen.

Basically, the nitrogen cycle in nature is based on chemical reactions in the air. Among them, oxidation predominates. Chemical interactions in the biosphere also play an important part among the interactions of nitrogen. The main place N2 in nature is the atmosphere. And plants play an important role, in fact, they begin a cycle of nitrogen in nature. The vegetable world of our planet performs the function of protein synthesis. As materials, nitrates are used that are in the soil. The source of natural nitrates is atmospheric nitrogen and ammonium salts. The very mechanism of transformation of a simple substance into a form, available for assimilation by plants, has been called nitrogen binding.

There are two mechanisms of nitrogen binding. In the first variant, during the lightning discharge, a certain amount of nitrogen oxides is formed. Diluting in water, they provoke the appearance of nitric acid, which gives a push for the appearance in the soil of nitrates. In the second variant, ammonia is formed. It is processed by bacteria into nitrates, usually they are located in the root knots of tuberous plants. Still this mechanism is called nitrification.

The death of the plant leads to the formation of ammonium compounds. Bacteria work on them, turning them into nitrates and nitrogen, returning to the atmosphere. Fixation, nitrification and denitrification of nitrogen are the constituent parts of a complex mechanism that carries out the nitrogen cycle in nature. The scheme of this process is that there is an exchange between the fixation of nitrogen and its denitrification.

Nitrogen fixation occurs when plants metabolize nitrogen compounds from the air, many bacteria and cyanobacteria are involved in this process. The products of fixing nitrogen are ammonia, nitrates or nitrites.

The cycle of nitrogen in nature with the transition to nitrification takes the next step from fixation. Now ammonia passes into nitrates and nitrites. During the course of denitrification, the cycle of nitrogen in nature ends, with nitrates decomposing to nitrogen. Pseudomonas, rod-shaped bacteria and other microorganisms take an active part in the process.

During the course of denitrification, several intermediate products may appear. The most important of these is nitrous oxide, it is a persistent greenhouse gas.

Expanding the topic, it is worthwhile to understand the meaning of the concepts of assimilation and mineralization. Assimilation is the process of the transition of inorganic nitrogen into its organic form. By mineralization is meant the conversion of organic nitrogen into an inorganic compound. Antagonists assimilation and mineralization are an important form of transformation of substances, during which there is a cycle of nitrogen in nature.

Presentation of the report on this topic is most successfully carried out using tables and charts.