THE MAIN POLLUTANTS OF SOILS
Soil is the top layer of land formed under the influence of plants, animals, microorganisms and climate from the parent rocks on which it is located. It is an important and complex component of the biosphere, closely related to its other parts.
There are several stages in the development and formation of the soil. Young soils are usually the result of weathering of the parent rocks or the transfer of sediment deposits (for example, alluvium). Microorganisms, pioneer plants - lichens, mosses, grasses, small animals settle on these substrates.Gradually, other plant and animal species are introduced, the composition of the biocenosis becomes more complex, a whole series of relationships arise between the mineral substrate and living organisms. As a result, a mature soil is formed, the properties of which depend on the original parent rock and climate.The process of soil development ends when the balance is reached, the correspondence of the soil with the vegetation cover and the climate.The soil is like a living organism, within which various complex processes take place. In order to maintain the soil in good condition, it is necessary to know the nature of the metabolic processes of all its components.The soil is home to a great variety of different living organisms: bacteria, micro-fungi, algae, protozoa, mollusks, arthropods and their larvae, earthworms and many others. All these organisms play a huge role in the formation of the soil and the change of its physical and chemical characteristics.
In artificial ecosystems, such a cycle is disrupted, since people withdraw a significant part of agricultural products, using it for their needs. Due to the non-participation of this part of the production in the cycle, the soil becomes infertile. To avoid this and increase soil fertility in artificial ecosystems, a person contributes organic and mineral fertilizers.
Soil pollution
Under normal natural conditions, all processes occurring in the soil are in equilibrium. But often a person is guilty of disturbing the equilibrium state of the soil. As a result of the development of human economic activity, pollution occurs, changes in the composition of the soil and even its destruction. And these insignificant areas continue to shrink due to inept human economic activity.Huge areas of fertile land are lost during mining operations, during the construction of enterprises and cities. The destruction of forests and natural grass cover, repeated plowing of the land without observing the rules of agricultural technology leads to soil erosion - destruction and washing away of the fertile layer by water and wind. One of the consequences of increased human production activity is the intensive pollution of the soil cover. The main pollutants of soils are metals and their compounds, radioactive elements, as well as fertilizers and pesticides used in agriculture.The most dangerous soil pollutants include mercury and its compounds. Mercury enters the environment with toxic chemicals, with industrial waste containing metallic mercury and its various compounds.Lead contamination of soils is even more widespread and dangerous.Lead compounds are used as additives to gasoline, so motor transport is a serious source of lead pollution. There is especially a lot of lead in the soils along major highways.Near large centers of ferrous and non-ferrous metallurgy, soils are contaminated with iron, copper, zinc, manganese, nickel, aluminum and other metals. In many places, their concentration is ten times higher than the MPC.Radioactive elements can get into the soil and accumulate in it as a result of precipitation from atomic explosions or during the disposal of liquid and solid waste from industrial enterprises, nuclear power plants or research institutions related to the study and use of atomic energy.
Modern agriculture, which widely uses fertilizers and various chemicals to control pests, weeds and plant diseases, has a significant impact on the chemical composition of soils. Currently, the amount of substances involved in the cycle in the process of agricultural activity is approximately the same as in the process of industrial production.Persistent organic compounds used as pesticides are particularly dangerous. They accumulate in the soil, in water, bottom sediments of reservoirs.
Heavy metals enter the soil mainly from the atmosphere with emissions from industrial enterprises. If the soils are contaminated with heavy metals and radionuclides, it is almost impossible to clean them. So far, the only way is known: to sow such soils with fast-growing crops that give a large green mass; such crops extract toxic elements from the soil, and then the harvested crop is subject to destruction. But this is a rather long and expensive procedure. It is possible to reduce the mobility of toxic compounds and their entry into plants, if increase the pH of the soil by liming or add large doses of organic substances, for example, peat. A good effect can be given by deep plowing, when the top polluted soil layer is lowered to a depth of 50 - 70 cm during plowing, and the deep soil layers are raised to the surface. To do this, you can use special multi-tiered plows, but the deep layers still remain polluted. Finally, crops that are not used as food or feed, such as flowers, can be grown on soils contaminated with heavy metals (but not radionuclides).
