- Problem definition
- The reasons
- Soil contamination: effects of contamination
- Deep processes
- Horizontal radionuclide redistribution
- Vertical Migration
- The most polluted areas on the planet
- Features of the use of contaminated areas
- Security measures
Human activity very often adversely affects the surrounding world of animate and inanimate nature. The rapid development of industry, the intensive development of agriculture, the difficulties of waste disposal - all this seriously threatens the ecology of the planet. With the development of nuclear energy and the improvement of nuclear weapons, another problem arose - the radioactive contamination of soils, water bodies, and the atmosphere.
Soil contamination is the excess in it of the concentration of radionuclides above the indicators of the maximum permissible rate due to anthropogenic activity.
Contaminated areas are characterized by a significant excess of doses of external and internal exposure. To indicate the rate of ionizing cure, the International Commission of Radiation Protection (ICRP) introduced an average annual dose of radiation, which for soils and rocks is 0.25-0.5 microsievert per year (mSv / g). This standard determines the amount of radiation that is safe for human health and is many times lower than the value that can lead to the death of a living organism over a further 30 days.
How does soil contamination occur? Sources of pollution are two groups of radionuclides:
It is known that the soil contains natural radionuclides. But their concentration increases significantly due to the extraction, storage of natural raw materials, processing, fertilization, their production, burning coal, using ashes as fertilizing plants or for the manufacture of building materials, etc.
Due to the rapid production and use of fertilizers, the amount of radioactively contaminated soils increases every year. For example, the issue of increasing the concentration of radionuclides in the soil due to the use of potash and phosphate fertilizers is not well understood.
Artificial radionuclides massively fall into the components of the planet's biosphere due to nuclear explosions.
Thus, the main causes of radioactive contamination of the soil cover are:
- intensive development of agricultural land;
- heavy industry;
- development of deposits of natural resources;
- disposal of radioactive waste;
- radiation emissions from nuclear power plants;
- test of nuclear weapons.
Soil contamination: effects of contamination
There are many negative effects of soil contamination:
- direct adverse effects of radioactive substances on animals, vegetation and humans;
- significant limitation of the ability to use soil resources for agricultural purposes. After all, all products that are obtained from such a land plot have higher than normal levels of the concentration of radioactive substances due to contamination of open water bodies and groundwater, where harmful compounds are washed out from the soil. Heavy pollution can lead to the inability to use fresh water not only for drinking and cooking, but also for feeding cattle or irrigating agricultural land.
Many scientists claim that environmental damage by radiation substances leads to the complete destruction of biogeotational populations and populations. This happens with a high level of pollution. Such areas are fixed mainly near the places where the emission of radiation occurred and, as a result, the radioactive contamination of the soil. Chernobyl - the exclusion zone after the Chernobyl accident. Then hundreds of hectares received the strongest dose of radiation, as a result of which they were completely removed from human life.
The soil absorbing complex sorts radioactive substances. In addition, he keeps them for a long time.
Radionuclides in the soil are characterized by:
- properties of chemically active isotopes;
- properties and composition of the soil itself;
- properties of radionuclides in depositions;
- climate indicators;
- landscape features.
Radionuclides to the surface of the soil come in the composition of aerosols, minerals, fuel particles, etc. The maximum part of their soluble fractions in the global fallout is 30-90%. The highest index is for cesium and strontium. Nobody knows how the radionuclides will behave in the future. Dynamic equilibrium increases as the solubility of their precipitations decreases. The introduction of soluble organic substances into the soil and the special acidification of the medium influence the increase in the radionuclide migration, which is used to purify it.
The mobility of radiation pollution depends on:
- mineralogical composition;
- the presence of geochemical barriers in the soil;
- granulometric composition;
- humus properties;
- medium reaction.
Horizontal radionuclide redistribution
To predict the possible effects of soil radioactive contamination, it is very important to know the features of the migration of radionuclides.
The redistribution of radionuclides in the soil occurs horizontally and vertically in a natural way and for reasons of anthropogenic activity.
Horizontal migration occurs due to:
- eolian transference (the name comes from the name of the god of winds Eola);
- flood waters that cause more intense pollution of lowlands and wetlands;
- the vital activity of animals (earthworms, wild boars, moles and other “digging”);
- harvesting green fodder in polluted meadows;
- forest fires, which are very powerful isotope transfer factors.
The minimum horizontal migration is observed in forest cenoses, and the maximum - in agrocenoses with light soils. Horizontal redistribution, on the one hand, reduces the level of soil contamination by radioactive nuclides, on the other hand, it expands the range of their distribution.
As for the vertical redistribution, it occurs slowly in all types of soil. The linear speed of this process ranges from tenths to two centimeters per year. The soil in this case plays the role of a biogeochemical barrier. Studies conducted in the Chernobyl zone showed that most of the radionuclides for a long time remained within the upper soil layer (about 10 cm). And in the forest part of this zone, radioactive substances have accumulated in the litter (foliage, needles) and the lower soil layer (about 1-2 cm).
Vertical migration of radionuclides depends on such factors:
- volcanic eruption;
- rains, moisture transfer by runoff and evaporation;
- transfer by root systems of plants;
- human activity - plowing, irrigation.
The most polluted areas on the planet
On the planet there are hundreds of radioactively contaminated areas. A serious danger is the territory of Henford in the state of Washington, USA. Here in the middle of the last century, a gigantic complex was built, which was engaged in the world's first nuclear development. As a result of its activities, an area of 518 square meters is polluted. km
Soils in Somalia were used for the illegal dumping of nuclear waste. The Semipalatinsk test site in Kazakhstan, where nuclear tests were conducted, is one of the most radiation-hazardous areas in the world. In the town of Mailuu-Suu, Kyrgyzstan, all-Union-scale uranium mining was established, which led to an extremely high concentration of radioactive isotopes in the mine district.
The well-known Chernobyl zone is a dead zone where radioactive contamination of soils happened for many hundreds of kilometers. The Chernobyl nuclear power plant is not the only nuclear power plant in the world where a global catastrophe occurred. This happened in Fukushima, Japan. Here the earthquake and tsunami in March 2011 caused an accident at a nuclear power plant, as a result of which a huge territory was damaged.
The industrial complex "Mayak" in Russia in the secret city "Chelyabinsk-40" near the town of Kyshtym suffered from an accident in 1957. Its consequences were radiation contamination of 25 thousand hectares of arable land. A similar catastrophic situation has developed around the Siberian Chemical Plant OJSC in the Tomsk Region, Russia.
Features of the use of contaminated areas
Radionuclides with a long decay period mainly accumulate in the soil: promethium-147, cerium-144, cesium-137, ruthenium-106 and 103, strontium-90. The most dangerous for living organisms is strontium-90. Therefore, agrochemical, agrotechnical and other measures that can reduce the transfer of hazardous compounds from the soil to plants are carried out in the fields contaminated by radiation. For this purpose, the top layer of soil is also cut off with subsequent burial.
An effective measure is the sowing of plants of certain varieties and species, which are characterized by a minimum level of accumulation of radionuclides. Everyone knows that in livestock farming, only clean feed should be used for fattening. Special sorbent additives are also used, which suppress the transfer of radioactive substances to the composition of milk.
Reclamation works are aimed at reducing the intake of radionuclides into plants. To do this, make sorbents in the soil, such as: vermiculite, zeolite, mineral and organic additives, lime. In agriculture, the reduction of accumulation of radionuclides in plants occurs with the help of agrotechnical methods. Conduct plantazhnuyu plowing, with the turnover of the reservoir. This tillage technique leads to a deepening of radioactive contamination. Due to this, the accumulation of substances in plants is reduced by 24 times. In agriculture, the structure of crop rotation should be changed. It is better to start growing technical crops that are not used in food.
An alternative method of using a contaminated area is the elimination of any specific impact. For example, you can create special reserves. With a pronounced radiation background, a forest, mainly pine, is planted at the site of infection.
Security measures in areas where there is radiation contamination of the soil, are aimed at reducing the negative impact of radiation. The following actions are carried out:
- development of strategies for the use of products and territory at the national or international level, depending on the extent of contamination and the potential risk of contamination of the surrounding areas;
- reclamation, agrotechnical measures;
- chemical disinfection;
- use of sorbents;
- restriction of human activity;
- informing the public about the possible danger;
- restriction of export of any products from the hazardous area.
The period of validity of these restrictions depends primarily on the density of pollution. In addition, pay attention to the exposure dose of radiation. This period can last from several weeks to many decades. Thus, environmentalists reduce the contamination of soil and its consequences.