human activity very often adversely affects the world around animate and inanimate nature.The rapid development of industry, intensive agriculture, difficulties in waste management - all of this seriously threatened the ecology of the planet.With the development of nuclear energy and the improvement of nuclear weapons there is another problem - the contamination of soils, waters, atmosphere.
Defining the problem
Contamination of soil - it is the excess concentration of radionuclides on indicators of the maximum permissible limits due to anthropogenic activities.
Contaminated areas are characterized by significant excess doses of external and internal exposure.To indicate the rate of cure of the International Commission of ionizing Radiation Protection (ICRP) was introduced by the average annual dose of radiation that the soils and rocks of 0.25-0.5 microsieverts per year (mSv / y).This standard specifies the safety for human health and the amount of radiation is many times lower than that which would lead to the death of a living organism for a further 30 days.
reasons
How is the contamination of the soil?Sources of pollution - the two groups of radionuclides:
- man-made;
- natural.
known that soil containing natural radionuclides.But their concentration is significantly increased due to the production, storage, natural raw materials, processing, fertilizer application, production, coal burning, the use of ash as a fertilizing plants or for the production of building materials, etc.
Due to the rapid production and use of fertilizer every year increases the amount of radioactively contaminated soils.For example, poorly understood issue of increasing concentrations of radionuclides in the soil due to the use of potash and phosphate fertilizers.
artificial radionuclides in large quantities fall into the components of the biosphere of the planet due to nuclear explosions.
Thus, the main reasons that cause the contamination of the soil cover are:
- intensive development of agricultural land;
- heavy industry;
- mining of natural resources;
- disposal of radioactive waste;
- emissions of radiation accident;
- nuclear test.
soil contamination: contamination consequences
There are many negative effects of soil contamination:
- direct negative impact of radioactive substances on animals, plants and humans;
- significant limitation of the ability to use soil resources for agricultural purposes.For all products, which is obtained from such land is higher than normal level of concentration of radioactive materials due to contamination of open water bodies and groundwater, where the soil washed out harmful compounds.Heavy pollution can lead to the inability to use the fresh water not only for drinking and cooking, but also on the desoldering livestock or irrigation of agricultural land.
Many scientists argue that the destruction of the environment by radiation substances lead to total loss biogeotsionozov and populations.This occurs when the high level of pollution.Such areas are recorded primarily near locations where there was an emission of radiation and, consequently, the contamination of the soil.Chernobyl - the exclusion zone after the accident.Then hundreds of hectares got a strong dose of radiation, resulting in a fully derived from human activity.
Deep processes
soil absorbing complex sorts of radioactive substances.Additionally, it stores them for a long time.
radionuclides in soil characterized by:
- properties of chemically active isotopes;
- properties and composition of the soil itself;
- properties of radionuclides in fallout;
- climatic indicators;
- features of the landscape.
Radionuclides come to the soil surface as a part of aerosols, minerals, fuel particles, etc.The maximum part of their soluble fractions in the global fallout of 30-90%.The highest figure from cesium and strontium.How to behave in the future radionuclides - nobody knows.Dynamic equilibrium increases with decreasing solubility loss.Soil soluble organic substances and a special effect on the acidification of the medium rise radionuclide migration that is used with a view to its purification.
Mobility radioactive contamination depends on:
- mineralogical composition;
- presence in soil geochemical barriers;
- size distribution;
- properties of humus;
- reaction medium.
Horizontal redistribution of radionuclides
To predict the possible consequences of soil contamination is very important to know the characteristics of radionuclide migration.
redistribution of radionuclides in the soil occurs in horizontal and vertical directions in a natural way and for reasons of human activities.
Horizontal migration occurs as a result of:
- aeolian transport (named after the god of the winds Aeolus);
- spill floodwater that is causing more intense contamination lowlands and wetlands;
- of animal (earthworm, wild boars, moles and other "digging");
- traffic;
- green forage harvesting in contaminated meadows;
- forest fires, which are a very powerful factor in the transport of isotopes.
minimum horizontal migration observed in the forest cenoses, and the maximum - in agrocenoses with light soils.Horizontal redistribution, on the one hand, reduces the level of soil contamination with radioactive nuclides, on the other - expanding the area of their distribution.
Vertical migration
As for vertical redistribution, then in all kinds of soil, it is slow.Linear speed of this process varies from a few tenths to two centimeters per year.The soil in this case serves as a biogeochemical barrier.Studies in Chernobyl, showed that the majority of the radionuclides in a long time remains within the top layer of soil (about 10 cm).A timber of this zone of the radioactive substance accumulated in the litter (leaves, needles) and the lower layer of soil (about 1-2 cm).
vertical migration of radionuclides depends on such factors:
- volcanic eruptions;
- rain, moisture transport runoff and evaporation;
- transfer of the plant root systems;
- human activity - plowing, irrigation.
most contaminated areas on the planet
on the planet, there are hundreds of radioactively contaminated areas.A serious danger is hanford area in Washington State, USA.Here in the middle of the last century was built a huge complex, it ranks first in the world nuclear developments.As a result of his activities in the contaminated area of 518 square meters.km.
soils in Somalia were used for the illegal disposal of nuclear waste.Semipalatnsky range in Kazakhstan, where nuclear tests were carried out, is one of the most radiation-hazardous areas in the world.In the town of Mailu-Suu, Kyrgyzstan, uranium had been established in the Union scale, which led to extremely high concentrations of radioactive isotopes in the area of mines.
All known Chernobyl zone - the dead zone, where many hundreds of kilometers of soil contamination happened.Chernobyl - not the world's only nuclear power plant, where there was a nuclear disaster of global proportions.This happened in Fukushima, Japan.Where the earthquake and tsunami in March 2011 caused the accident at the nuclear power plant, which affected a huge area.
industrial complex "Mayak" in Russia in a secret city "Chelyabinsk-40" near the town of Kyshtym affected by the accident in 1957.It later became the contamination of 25 thousand hectares of arable land.Such a catastrophic situation around OJSC Siberian Chemical Combine in Tomsk, Russia.
Features use of contaminated areas
The soil is mainly accumulated radionuclides with long half-decay: promethium-147, Cerro-144, cesium-137, ruthenium-106 and 103, strontium-90.The most dangerous for living organisms is strontium-90.Therefore, in the fields infected with radiation, conduct agrochemical, agronomic and other measures that can reduce the transition of hazardous compounds from soil to plants.To this end, also cut the top layer of the soil and burying.
effective measure is the planting of some varieties of plants and species, which are characterized by a minimum level of accumulation of radionuclides.We all know that in animal fattening, use only clean feed.Use as sorbents special additives that inhibit passage of radioactive substances in the milk.
Reclamation work aimed at reducing the intake of radionuclides into plants.For this sorbents introduced into the soil, such as vermiculite, zeolite, mineral and organic additives, lime.In agriculture, the reduction of accumulation of radionuclides in plants occurs by means of agricultural practices.Spend plantage plowing, with a turnover of formation.This technique tillage leads to a deepening of radioactive contamination.Due to the accumulation of substances in the plant is reduced by 24 times.In agriculture, the need to change the structure of the crop rotation.It is better to start to grow industrial crops, which are not used for food.
alternative method of using the contaminated area is the removal of any specific action.For example, you can create special reserves.Pronounced background radiation at the site of infection planted forest, mainly pine.
security measures
security measures in areas where there is radioactive contamination of the soil, are directed at reducing the negative impact of radiation.Conduct such actions:
- development strategy for the use of products and territory to the national or international level, depending on the extent of pollution and the potential risk of contamination of surrounding areas;
- reclamation, agro-technical measures;
- chemical decontamination;
- use of sorbents;
- restriction of human activities;
- informing the public about the possible dangers;
- limit export any product to the dangerous area.
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 weeks to decades.Thus ecologists reduce the contamination of soil and its effects.
