The effect of toxic substances on soil contamination

Soil pollution with heavy metals

Soil pollution with heavy metals has different sources:

1. Waste metalworking industry;

2. Industrial emissions;

3. Fuel combustion products;

4. Automobile exhaust of exhaust gases;

5. Funds of chemicalization of agriculture.

Metallurgical enterprises are annually emitted to the surface of the Earth more than 150 thousand tons of copper, 120 thousand tons of zinc, about 90 thousand tons of lead, 12 thousand tons of nickel, 1.5 thousand tons of molybdenum, about 800 tons of cobalt and about 30 tons of mercury . On 1 gram of draft copper, the waste of the copper-smelting industry contains 2.09 tons of dust, which contains up to 15% of copper, 60% of iron oxide and 4% arsenic, mercury, zinc and lead. Waste machine-building and chemical industries contain up to 1 thousand mg / kg lead, up to 3 thousand mg / kg of copper, up to 10 thousand mg / kg of chromium and iron, up to 100 g / kg of phosphorus and up to 10 g / kg of manganese and nickel . In Silesia around the zinc plants, dumps with zinc content from 2 to 12% and lead from 0.5 to 3% are praying, and in the United States exploit ores with a zinc content of 1.8%.

With exhaust gases, more than 250 thousand tons of lead fall into the surface of the soil per year; This is the main polluter soil lead.

Heavy metals fall into the soil together with fertilizers, which they enter as an admixture, as well as with biocides.

L. G. Bondarev (1976) calculated possible receipts of heavy metals on the surface of the soil cover as a result of human production activities with full exhaustion of ore reserves, in the combustion of the existing reserves of coal and peat and comparing them with possible reserves of metals accumulated in the gumosphere to date. The resulting picture allows you to make an idea of \u200b\u200bthe changes that a person is able to cause for 500-1000 years, which is enough for proven minerals.

Possible receipt of metals in the biosphere with the exhaustion of reliable reserves of ores, coal, peat, million tons

	Total maniogenous emissions of metals	Contained in the gumosphere	The ratio of technogenic emissions to the content in the gumosphere

The attitude of these quantities allows to predict the scale of the influence of human activity on the environment, primarily on soil cover.

Technogenic flow of metals in the soil, consolidation of them in humus horizons in the soil profile as a whole cannot be uniform. Its unevenness and contrast is primarily associated with the density of the population. If you consider this relationship proportional, then 37.3% of all metals will be dissipated only in 2% of the survivable sushi.

The distribution of heavy metals on the surface of the soil is determined by many factors. It depends on the characteristics of the sources of pollution, the meteorological characteristics of the region, geochemical factors and the landscape situation as a whole.

The source of pollution as a whole determines the quality and amount of the produced product. In this case, the degree of dispersion depends on the height of the emission. The maximum pollution zone is distributed to a distance equal to a 10-40-fold height of the pipe with a high and hot emission, a 5-20-fold height of the pipe with a low industrial emission. The duration of the release of emission particles in the atmosphere depends on their mass and physicochemical properties. The heavier particles, the faster they settle.

The non-uniformity of the technogenic propagation of metals is exacerbated by the heterogeneity of the geochemical situation and natural landscapes. In this regard, to predict possible pollution by the products of technogenesis and the prevention of the unwanted consequences of human activity, it is necessary to understand the laws of geochemistry, the laws of migration of chemical elements in various natural landscapes or a geochemical setting.

The chemical elements and their compounds fall into the soil undergo a number of transformations, dissipate or accumulate depending on the nature of geochemical barriers inherent in this area. The concept of geochemical barriers was formulated by A. I. Perelman (1961) as sections of the hypergenesis zone, where the change in migration conditions leads to the accumulation of chemical elements. The basis of the classification of barriers is the migration types of elements. On this basis, A. I. Perelman allocates four types and several classes of geochemical barriers:

1. Barriers - for all elements that biogeochemical redistributed and sorted by alive organisms (oxygen, carbon, hydrogen, calcium, potassium, nitrogen, silicon, manganese, etc.);

2. Physical and chemical barriers:

1) Oxidative - iron or iron-manganese (iron, manganese), manganese (manganese), sulfur (sulfur);

2) reducing - sulphide (iron, zinc, nickel, copper, cobalt, lead, arsenic, etc.), Gleyevaya (vanadium, copper, silver, selenium);

3) sulphate (barium, calcium, strontium);

4) alkaline (iron, calcium, magnesium, copper, strontium, nickel, etc.);

5) sour (silicon oxide);

6) evaporative (calcium, sodium, magnesium, sulfur, fluorine, etc.);

7) adsorption (calcium, potassium, magnesium, phosphorus, sulfur, lead, etc.);

8) thermodynamic (calcium, sulfur).

3. Mechanical barriers (iron, titanium, chrome, nickel, etc.);

4. Technogenic barriers.

Geochemical barriers exist not isolated, but in combination with each other, forming complex complexes. They regulate the elemental composition of the flows of substances, the functioning of ecosystems depends to greater extent.

The products of technogenesis, depending on their nature and the landscape, in which they fall, can either be recycled with natural processes, and do not cause significant changes in nature, or maintain and accumulate, destructive affecting all living things.

Both the other process are determined by a number of factors whose analysis allows to judge the level of biochemical stability of the landscape and predict the nature of their changes in nature under the influence of technogenesis. In autonomous landscapes, self-cleaning processes from technogenic pollution are developing, since technogenesis products are scattered with surface and intravenous waters. In accumulative landscapes, technogenesis products are accumulated and preserved.

* At the motorway depending on the traffic intensity and distance to the motorway

Mascinating attention to environmental protection caused special interest in impact on the soil of heavy metals.

From a historical point of view, interest in this problem appeared with the study of soil fertility, since such elements like iron, manganese, copper, zinc, molybdenum, and possibly cobalt, are very important for the life of plants and, therefore, for animals and humans.

They are known and called trace elements, because plants are needed in small quantities. The group of trace elements also includes metals, the content of which in the soil is quite high, for example, iron, which is part of most soils and occupies a fourth place in the composition of the earth's crust (5%) after oxygen (46.6%), silicon (27.7 %) and aluminum (8.1%).

All trace elements can have a negative effect on the plants if the concentration of their available forms exceeds certain limits. Some heavy metals, such as mercury, lead and cadmium, which, apparently, are not very important for plants and animals, are dangerous to human health even at low concentrations.

Exhaust gases of vehicles, export in the field or wastewater treatment plant, wastewater irrigation, waste, residues and emissions during the operation of mines and industrial sites, the introduction of phosphate and organic fertilizers, the use of pesticides, etc. led to an increase in the concentrations of heavy metals in the soil.

As long as heavy metals are firmly connected with composite parts of the soil and difficult to access, their negative effect on the soil and the environment will be insignificant. However, if the soil conditions allow you to move heavy metals to the soil solution, the direct risk of soil contamination appears, there is a possibility of penetrating them into plants, as well as in the human body and animals that consume these plants. In addition, heavy metals can be pollutants of plants and water bodies as a result of the use of waste water. The danger of soil pollution and plants depends: from the type of plants; forms of chemical compounds in the soil; the presence of elements of opposing the effects of heavy metals and substances that form comprehensive compounds with them; from the processes of adsorption and desorption; The number of available forms of these metals in the soil and soil-climatic conditions. Consequently, the negative effect of heavy metals depends essentially on their mobility, i.e. solubility.

Heavy metals are mainly characterized by variable valence, low solubility of their hydroxides, high ability to form complex compounds and, naturally, cationic ability.

The factors that contribute to the deduction of heavy metals soil include: exchange adsorption of the surface of clay and humus, the formation of complex compounds with humus, the adsorption of surface and occlusion (dissolving or absorbable gases melted or solid metals) hydrated aluminum, iron, manganese oxides, etc. , as well as the formation of insoluble compounds, especially when restoring.

Heavy metals in the soil solution are found both in ion and in the associated forms that are in a certain equilibrium (Fig. 1).

In Figure L P - soluble ligands, what are organic acids with a small molecular weight, and l - insoluble. The reaction of metals (M) with humus substances includes partially and ion exchange.

Of course, there may be other forms of metals in the soil, which do not participate directly in this equilibrium, for example, metals from the crystal lattice of primary and secondary minerals, as well as metals from living organisms and their dead residues.

Observation of the change in heavy metals in the soil is impossible without knowledge of the factors determining their mobility. The processes of movement of the deduction, which cause the behavior of heavy metals in the soil, are not much different from the processes that determine the behavior of other cations. Although heavy metals are sometimes detected in soils at low concentrations, they form stable complexes with organic compounds and enter specific adsorption reactions are easier than alkaline and alkaline earth metals.

The migration of heavy metals in soils can occur with liquid and suspension with the help of plant roots or soil microorganisms. Migration of soluble compounds occurs together with soil solution (diffusion) or by moving the fluid itself. The flushing of clays and organic matter leads to the migration of all the metals associated with them. The migration of volatile substances in a gaseous form, for example, dimethyl mercury, is random, and this method of displacement does not have much importance. Migration in the solid phase and penetration into the crystal lattice are more binding mechanism than moving.

Heavy metals can be made or adsorbed by microorganisms, which in turn are able to participate in the migration of the corresponding metals.

Rainy worms and other organisms can promote migration of heavy metals with mechanical or biological paths, stirring the soil or including metals in their fabrics.

Of all the migration types, the most important is migration in the liquid phase, because most of the metals fall into the soil in soluble or in the form of aqueous suspension and in fact all interactions between heavy metals and liquid components of the soil occurs on the border of the liquid and solid phases.

Heavy metals in the soil through the trophic chain come to the plants, and then consumed by animals and man. Different biological barriers are involved in the cycle of heavy metals, as a result of which selective bio-accumulation occurs, protecting living organisms from excess of these elements. Nevertheless, the activity of biological barriers is limited, and most often heavy metals are concentrated in the soil. Soil resistance to pollution is different depending on bufferiness.

Soils with a high adsorption capacity, respectively, and a high content of clays, as well as organic matter can hold these elements, especially in the upper horizons. This is characteristic of carbonate soils and soils with a neutral reaction. In these soils, the amount of toxic compounds that can be washed into groundwater and are absorbed by plants, significantly less than in sandy acidic soils. However, there is a big risk in increasing the concentration of elements to toxic, which causes a violation of the equilibrium of physical, chemical and biological processes in the soil. Heavy metals held by the organic and colloidal parts of the soil significantly limit biological activity, inhibit yttrification processes that are important for soil fertility.

Sand soils, which are characterized by low absorption capacity, as well as acidic soils very poorly hold heavy metals, with the exception of molybdenum and selenium. Therefore, they are easily adsorbed by plants, with some of them even in very low concentrations have toxic effects.

The zinc content in the soil fluctuates from 10 to 800 mg / kg, although it is most often 30-50 mg / kg. The accumulation of an excess amount of zinc adversely affects the majority of soil processes: causes a change in the physical and physicochemical properties of the soil, reduces biological activities. Zinc suppresses the life of microorganisms, as a result of which the processes of formation of organic matter in the soils are violated. Excess zinc in soil cover makes it difficult to ferment the decomposition of cellulose, respiration, the actions of urease.

Heavy metals, coming out of the soil in the plant, transmitting along the supply chains, have a toxic effect on plants, animals and humans.

Among the most toxic elements, it is primarily to be called mercury, which represents the greatest danger in the form of a strong-toxic compound - methylratuti. Mercury enters the atmosphere when burning coal and when evaporation of water from contaminated water bodies. With air masses, it can be transferred and deposited on the soils in separate areas. Studies have shown that mercury is well sorbed in the upper centimeters of the humid and accumulative horizon of different types of soils of a loamy mechanical composition. Her migration by profile and leaning outside the soil profile in such soils is insignificant. However, in the soils of a light mechanical composition, acidic and depleted humus, mercury migration processes are enhanced. In such soils, the process of evaporation of organic mercury compounds, which possess volatility properties.

When mercury is making a sand, clay and peat soil at the rate of 200 and 100 kg / hectare, the crop on sandy soil is completely died regardless of the level of lime. At peat soil, the harvest dropped. On clay soil there was a decrease in harvest only at a low dose of lime.

Lead also has the ability to transmit along the supply chains, accumulating in the tissues of plants, animals and humans. Dose of lead, equal to 100 mg / kg of dry feed weight, is considered lethal for animals.

The lead dust settles on the surface of the soil, is adsorbed by organic substances, moves along the profile with soil solutions, but is carried out beyond the soil profile in small quantities.

Thanks to the process of migration under an acidic environment, technogenic lead anomalies in soils with a length of 100 m. Lead from soil enters the plants and accumulates in them. In the grain of wheat and barley, the amount of it is 5-8 times higher than the background content, in the buckle, potatoes - more than 20 times, in the tubers - more than 26 times.

Cadmium, like vanadium and zinc, accumulates humus thicker soil. The character of its distribution in the soil profile and landscape, apparently, has a lot in common with other metals, in particular with the character of the distribution of lead.

However, cadmium is fixed in the soil profile less firmly than lead. The maximum adsorption of cadmium is peculiar to neutral and alkaline soils with a high content of humus and high absorption capacity. Its content in podzolic soils can be from hundredths of up to 1 mg / kg, in chernozem - up to 15-30, and in the red blood - up to 60 mg / kg.

Many soil invertebrates concentrate cadmium in their organisms. Cadmium is absorbed by rainworms, mocicians and snails 10-15 times more active than lead and zinc. Cadmium toxic for agricultural plants, and even if high cadmium concentrations do not have a noticeable effect on the crop of crops, it affects it on changing the quality of products, since the content of cadmium is increased in plants.

The arsenic falls into the soil with coal combustion products, with waste of the metallurgical industry, with enterprises for the production of fertilizers. The most firmly arsenic is held in the soirs containing the active forms of iron, aluminum, calcium. The toxicity of arsenic in the soils is known to everyone. Pollution of soils arsenic causes, for example, the death of rainwrites. The background content of arsenic in soils is the hundredths of the milligram per kilogram of the soil.

Fluorine and its compounds are widely used in atomic, petroleum, chemical, and other industries. It falls into the soil with emissions of metallurgical enterprises, in particular, aluminum plants, as well as admixtures when making superphosphate and some other insecticides.

Contaminary soil, fluorine causes a reduction in harvest not only due to direct toxic effect, but also changing the ratio of nutrients in the soil. The greatest adsorption of fluorine occurs in soils with a well-developed soil absorbing complex. The soluble fluoride compounds move along the soil profile with a downward current of the soil solutions and can fall into groundwater. Soil contamination with fluoride compounds destroys the soil structure and reduces the water permeability of the soil.

Zinc and copper are less toxic than these heavy metals, but the excessive amount in the waste of the metallurgical industry pollutes the soil and inhibit the growth of microorganisms, reduces the enzymatic activity of soil, reduces the crop of plants.

It should be noted that the toxicity of heavy metals should be placed under their joint impact on living organisms in the soil. The joint impact of zinc and cadmium has several times a stronger inhibitory effect on microorganisms than at the same concentration of each element separately.

Since heavy metals and in fuel combustion products, and in the emissions of the metallurgical industry are usually found in various combinations, the effect of them on nature surrounding the sources of pollution is stronger than those supposed on the basis of the concentration of individual elements.

Near enterprises, natural phytocenoses of enterprises become more monotonous in the species composition, since many species do not maintain the increase in the concentration of heavy metals in the soil. The number of species can be reduced to 2-3, and sometimes before the formation of monocenoses.

In forest phytocenoses, the first responds to pollution of lichens and mosses. The most stable wood tier. However, a long or high-intensity effect causes dry dry phenomena.

Pissicide soil pollution

Pesticides are mainly organic compounds with small molecular weight and different solubility in water. Chemical composition, their acidity or alkalinity, water solubility, structure, polarity, magnitude and polarization of molecules - all these features together or each individual affects the processes of adsorption-desorption with soil colloids. Taking into account the names of pesticides and the complex nature of the relationship in the process of adsorption-desorption by colloids, they can be divided into two large classes: polar and non-polar, and not included in this classification, for example, chlororganic insecticides - on ionic and non-ionic.

Pesticides, which contain acidic or main groups, or behave during dissociation as cations, constitute a group of ionic connections. Pesticides that do not have a sour nor alkaline reaction are a group of non-ionic compounds.

The nature of chemical compounds and the ability of soil colloids to adsorption and desorption is influenced: the nature of functional groups and substitution groups with respect to functional groups and the degree of saturation of the molecule. For adsorption of pesticide molecules with soil colloids, the nature of molecular charges has a significant impact, the polarity of molecules plays a certain role. The uneven distribution of charges increases the dissimetry of the molecule and its reactivity.

The soil mainly acts as the successor of pesticides, where they decompose and where they are constantly moving in plants or the environment, or as a repository, where some of them can exist many years after the application.

Pesticides - fine substances - in the soil are subject to numerous effects of biotic and nebiotic nature, some determine their behavior, transformation and, finally, mineralization. The type and speed of transformations depends on: the chemical structure of the active substance and its stability, the mechanical composition and structure of the soil, the chemical properties of the soil, the composition of the flora and the soil fauna, the intensity of the influence of external influences and the agricultural system.

Adsorption of pesticides in the soil is a complex process depending on numerous factors. It plays an important role in moving pesticides and serves to temporarily maintain in vapor or dissolved state or as a suspension on the surface of soil particles. A particularly important role in the adsorption of pesticides is played by il and organic soil substance, which constitute the "colloidal complex" of the soil. Adsorption is reduced to the ion-cationic exchange of negatively charged or complex particles and acid groups of humus substances, or anionic, due to the presence of metal hydroxides (Al (OH) 3 and Fe (OH) 3) or occurs in the form of molecular metabolism. If the adsorbed molecules are neutral, then they are held on the surface of or organic particles and humus colloids by bipolar forces, hydrogen bonds and dispersed forces. Adsorption plays a paramount role in the accumulation of pesticides in the soil, which are adsorbed by ion exchange or in the form of neutral molecules depending on their nature.

The movement of pesticides in the soil occurs with soil solution or simultaneously with the movement of colloidal particles on which they are adsorbed. It depends on both diffusion processes and mass current (discharge), which are a conventional method for washing.

With surface drain, rapid or irrigation, pesticides are moved in solution or suspension, accumulating in soil recesses. This form of movement of pesticides depends on the terrain, the eroding of soils, the intensity of precipitation, the degree of coating of soils by vegetation, the period of time passed since the pesticide. The number of pesticides moving with surface runoff is more than 5% of the soil. According to the Romanian Research Institute of Soil Science and Agrochemistry on the stock venues in the experimental center of Alden as a result of the washing rains, the loss of triazine occurs simultaneously with the soil. The residual amounts of HCH from 1.7 to 3.9 mg / kg were detected on the stock vessels with a slope of 2.5% in Bilche-ARJ, and in suspension - from 0.041 to 0.085 mg / kg of HCHR and from 0.009 to 0.026 mg / kg DDT.

Washing pesticides According to the soil profile consists of their movement together with water circulating in soil, which is due to the main physico-chemical properties of soil, the direction of water movement, as well as the adsorption and desorption processes of pesticides with colloid soil particles. So, in the soil, annually for a long time processed DDT in a dose of 189 mg / ha, after 20 years, 80% of this pesticide, which penetrated to depth 76 cm.

According to studies conducted in Romania, not three different soils (alluvial purified, typical salt, powerful chernozem), where the treatment with chlororganic insecticides (GCHG and DDT) were carried out for 25 years (with irrigation over the past decade), residual amounts of pesticides reached The depths of 85 cm in a typical salt bar, 200 cm in alluvial purified soil and 275 cm in the black soil with a concentration of 0.067 mg / kg of the CCLG and, respectively, 0.035 mg / kg DDT at a depth of 220 cm.

On pesticides that have fallen into the soil are influenced by various factors both during their efficiency and in the future, when the drug is already becoming residual. Pesticides in the soil are susceptible to decomposition due to nebiotic and biotic factors and processes.

Physical and chemical properties of soils affect transformations in pesticides in it. So clay, oxides, hydroxisals and metal ions, as well as the organic substance of the soil, perform the role of catalysts in many reactions of decomposition of pesticides. Pesticide hydrolysis comes with the participation of groundwater. As a result of the reaction with free radicals of humus substances, a change in the composite particles of the soil and the molecular structure of pesticides occurs.

In many works, the great importance of soil microorganisms in the decomposition of pesticides is emphasized. There are very few active substances that do not decompose biologically. The duration of the decomposition of pesticides by microorganisms can vary from several days to several months, and sometimes decades, depending on the specifics of the active substance, types of microorganisms, soil properties. The decomposition of the actors of pesticides is carried out by bacteria, mushrooms and higher plants.

Typically, the decomposition of pesticides, especially soluble, less frequently adsorbed by soil colloids occurs with the participation of microorganisms.

Mushrooms are mainly involved in the decomposition of weakly soluble and poorlyaded herbicide colloids.

Recultivation and control over soil pollution with heavy metals and pesticides

The identification of soil contamination with heavy metals is made by direct methods of selection of soil samples on the territories studied and their chemical analysis on the maintenance of heavy metals. It is also effectively used for these purposes a number of indirect methods: a visual assessment of the state of phytogenesis, analysis of the distribution and behavior of species - indicators among plants, invertebrates and microorganisms.

To identify the spatial patterns of manifestation of soil contamination, a comparative geographic method is used, mapping methods of structural components of biogeocenoses, including soils. Such cards not only register the level of soil contamination with heavy metals and the corresponding changes in the impark cover, but allow you to predict a change in the state of the natural environment.

The distance from the source of pollution to identify the halo pollution can fluctuate in large limits and, depending on the intensity of pollution and the forces of dominant winds, can vary from hundreds of meters to tens of kilometers.

In the United States on board the resource satellite ERRS-1, sensors were installed to determine the degree of damage to the Waemut Pine with sulfur gas and the soil zinc. The source of pollution was a zincofavior plant, acting with the daily release of zinc into the atmosphere of 6.3-9 tons. Registered zinc concentration, equal to 80 thousand μg / g in the surface layer of the soil within a radius of 800 m from the plant. The vegetation around the plant died in a radius of 468 hectares. The complexity of using the remote method is to integrate the materials, as necessary when deciphering the information received from the series of control tests in areas of specific pollution.

Identification of the level of toxicity of heavy metals is not easy. For soils with different mechanical compositions and content of organic matter, this level will be no way. Currently, employees of the Institutes of Hygiene made attempts to determine the MPC metals in the soil. As test plants, barley, oats and potatoes are recommended. Toxic level was considered when the yield decreases by 5-10%. Note for mercury - 25 mg / kg, arsenic - 12-15, cadmium - 20 mg / kg. Some destructive concentrations of a number of heavy metals in plants (g / m) are established: Lead - 10, mercury - 0.04, chrome - 2, cadmium - 3, zinc and manganese - 300, copper - 150, cobalt - 5, molybdenum and Nickel - 3, Vanadium - 2.

The protection of soils from pollution by heavy metals is based on improving production. For example, 45 kg of mercury is consumed on the production of 1 tons of chlorine, and at the other - 14-18 kg. In the future, it is considered possible to reduce this value to 0.1 kg.

A new strategy for the protection of soils from pollution with heavy metals is also concluded in the creation of closed technological systems, in the organization of waste-free industries.

The waste of the chemical and machine-building industry is also valuable secondary raw materials. So the waste of machine-building enterprises are valuable raw materials for agriculture due to phosphorus.

Currently, the task of compulsory verification of all the possibilities of utilizing each type of waste, before their disposal or destruction.

With atmospheric soil contamination with heavy metals, when they are concentrated in large quantities, but in the most upper centimeters of the soil, it is possible to remove this layer of the soil and its burial.

Recently, a number of chemicals are recommended that can inactivate heavy metals in the soil or lower their toxicity. The FRG proposed the use of ion exchange resins forming heavy metal compounds. They are used in acidic and salt forms or in a mixture of both forms.

In Japan, France, Germany and Great Britain, one of the Japanese firms patented a method for fixing heavy metals Mercpto-8-Tiazine. When using this preparation, cadmium, lead, copper, mercury and nickel are firmly fixed in the soil in the form of unusual and inaccessible for plants forms.

Calming of soil reduces the acidity of fertilizers and solubility of lead, cadmium, arsenic and zinc. The absorption of their plants sharply decreases. Cobalt, nickel, copper and manganese in a neutral or weakly alkaline medium also do not have toxic action on plants.

Organic fertilizers, like the organic soil substance, are adsorbed and held in absorbed state most heavy metals. Making organic fertilizers in high doses, the use of green fertilizers, bird litter, rice straw flour reduce cadmium content and fluorine in plants, as well as chromium toxicity and other heavy metals.

Optimization of plants mineral nutrition by regulating the composition and doses of fertilizers also reduces the toxic effect of individual elements. In England, in soils infected with lead, arsenic and copper, the delay in the appearance of germination was removed when making mineral nitrogen fertilizers. The introduction of increased doses of phosphorus reduced the toxic effect of lead, copper, zinc and cadmium. With an alkaline reaction of the medium at the filling rice fields, the introduction of phosphoric fertilizers led to the formation of insoluble and hard-to-reach for the phosphate plants of cadmium.

However, it is known that the level of toxicity of heavy metal metals for different types of plants. Therefore, the removal of the toxicity of heavy metals to the optimization of mineral nutrition should be differentiated not only taking into account the soil conditions, but also of the type and variety of plants.

Among the natural plants and crops, a number of types and varieties resistant to pollution of heavy metals were revealed. These include cotton, beets and some legumes. A combination of safety measures and measures to eliminate soil pollution with heavy metals makes it possible to protect the soil and plants from their toxic impact.

One of the main conditions for the protection of soils from contamination by biocides is the creation and use of less toxic and less persistent compounds and making them into the soil and reduce the doses of their introduction into the soil. There are several ways to reduce the dose of biocides without reducing the efficiency of their cultivation:

· Combination of pesticides with other techniques. Integrated pest control method - Agrotechnical, biological, chemical, etc. At the same time, the task is not to destroy the whole type of entirely, but reliably protect the culture. Ukrainian scientists apply a microbireparation in aggregate with small doses of pesticides, which weakens the pest body and make it more susceptible to diseases;

· Application of promising forms of pesticides. The use of new forms of pesticides can significantly reduce the rate of consumption of the active substance and minimize unwanted consequences, including soil pollution;

· Alternation of using toxicants with an unequal mechanism of action. This method of making chemical means of struggle prevents the emergence of stable forms of pests. For most cultures, 2-3 drugs with an unequal spectrum of action are recommended.

When processing soil pesticides, only a small part of them reaches places of application of the toxic action of plants and animals. The rest is accumulated on the surface of the soil. The degree of soil contamination depends on many reasons and primarily from the resistance of the biocide itself. The resistance of the biocide understand the ability of toxicant to resist the decomposing action of physical, chemical and biological processes.

The main criterion of the detoxicant is a complete decay of the toxicant to non-toxic components.

The soil cover of the Earth plays a decisive role in providing human nutrition and raw materials for vitality industries. The use of ocean, hydroponics, or artificially synthesized substances, for this purpose, can not, at least in the foreseeable future, replace the products of ground ecosystems (soil productivity). Therefore, continuous monitoring of the state of soil and soil cover is a prerequisite for obtaining planned products of rural and forestry.

At the same time, the soil cover is a natural base for the settlement of people, serves as the basis for creating recreational areas. It allows you to create an optimal ecological situation for life, labor and recreation of people. On the nature of the soil cover, the properties of the soil flowing into the soils of chemical and biochemical processes depend on the purity and composition of the atmosphere, terrestrial and groundwater. Soil cover - one of the most powerful regulators of the chemical composition of the atmosphere and hydrosphere. The soil was and remains the main condition for the livelihood of nations and humanity as a whole. Preservation and improvement of soil cover, and, consequently, the main life resources in the conditions of intensifying agricultural production, the development of industry, the rapid growth of cities and transport is possible only with well-established control over the use of all types of soil and land resources.

Soil is the most sensitive to anthropogenic effects. Of all the Earth shells, the soil cover is the thinnest shell, the power of the most fertile glumulated layer, even in chernozem does not exceed, as a rule, 80-100 cm, and in many soils of most natural zones it is only 15-20 cm. Loose soil body with The destruction of many years of vegetation and the spindle is easily exposed to erosion and deflation.

With insufficiently thought-out anthropogenic effects and violation of balanced natural environmental bonds in the soils, unwanted humus mineralization processes are rapidly developed in soils, acidity or alkalinity increases, saline, rehabilitation processes are growing - all this sharply deteriorates the properties of the soil, and in limiting cases leads to local destruction of soil cover. High sensitivity, the vulnerability of soil cover is due to limited bufferiness and soil resistance to the effects of forces that are not inherent in environmental terms.

Even the chernozem suffered very significant changes in the last 100 years, causing anxious and reasonable concerns for his further fate. All in a broader scale manifests soil contamination with heavy metals, petroleum products, detergents, the effect of nitric and sulfuric acids of technogenic origin, leading to the formation of man-made deserts in the vicinity of some industrial enterprises increases.

Restoration of the impaired soil cover requires a long time and large capital investments.

One of the sources of environmental pollution is heavy metals (TM), more than 40 elements of the Mendeleev system. They take part in many biological processes. Among the most common heavy metals that pollute the biosphere are elements:

• nickel;
• titanium;
• zinc;
• lead;
• vanadium;
• mercury;
• cadmium;
• tin;
• chromium;
• copper;
• manganese;
• molybdenum;
• cobalt.

Sources of environmental pollution

In a broad sense, sources of environmental pollution with heavy metals can be divided into natural and technogenic. In the first case, the chemical elements fall into the biosphere due to water and wind erosion, eruption of volcanoes, weathered minerals. In the second case, TM fall into the atmosphere, a lithosphere, a hydrosphere due to active anthropogenic activity: when burning fuel for energy, during the operation of the metallurgical and chemical industry, in the agro-industriality, during the mining of fossils, etc.

During the operation of industrial facilities, environmental pollution with heavy metals is happening in various ways:

• into air in the form of aerosols, spreading into extensive territories;
• together with industrial runoff, the metals enroll in the reservoirs, changing the chemical composition of rivers, seas, oceans, and also fall into groundwater;
• sundaying in the soil layer, the metals change its composition, which leads to its exhaustion.

Danger of pollution with heavy metals

The main danger of TM is that they pollute all the layers of the biosphere. As a result, smoke and dust emissions fall into the atmosphere, then fall out in the form. Then people and animals breathe dirty air, these elements fall into the body of living beings, causing all sorts of pathologies and illness.

Metals pollute all water and water sources. This generates the problem of drinking water deficit on the planet. In some regions of the Earth, people die not only from the fact that they drink dirty water, and in the consequence of what is sick, but also from dehydration.

Accumulating in the ground, TM poison plants growing in it. Finding into the soil, the metals are absorbed into the root system, then enter the stems and leaves, root and seeds. Their excess leads to a deterioration in the growth of flora, toxication, yellowing, fading and destruction of plants.

Thus, heavy metals have a negative impact on the environment. They fall into the biosphere in various ways, and, of course, mostly thanks to the activities of people. To slow down the process of the TM contamination, it is necessary to control all areas of industry, use cleansing filters and reduce the amount of waste in which metals may be contained.

Heavy metals entering the environment as a result of human production activities (industry, transport, etc.) are one of the most dangerous pollutants of the biosphere. Elements such as mercury, lead, cadmium, copper are related to the "critical group of substances - environmental stress indicators." It is estimated that only metallurgical enterprises are thrown into the surface of the Earth more than 150 thousand tons of copper; 120 - zinc, about 90 - lead, 12 - nickel and about 30 tons of mercury. These metals tend to be fixed in individual units of biological circulation, accumulated in biomass of microorganisms and plants and in the trophic chains to enter the organism of animals and a person, negatively affecting their livelihoods. On the other hand, heavy metals certainly affect the environmental situation, overwhelming the development and biological activity of many organisms.

The relevance of the impact of heavy metals to soil microorganisms is determined by the fact that it is in the soil most of all the processes of mineralization of organic residues that ensure the conjugation of the biological and geological cycle. The soil is an ecological assembly of biosphere connections, in which the interaction of alive and inanimate matter is most intensively. On the soil, the metabolic processes are closed between the earth's crust, hydrosphere, an atmosphere that live on the bodies of organisms, an important place among which soil microorganisms occupy.
From these perennial observations of Roshydromet, it is known that according to the total index of soil pollution by heavy metals, calculated for the territories within the five-kilometer zone, 2.2% of the settlements of Russia refer to the category of "extremely dangerous pollution", 10.1% - "dangerous pollution", 6.7% - "moderately dangerous pollution." More than 64 million citizens of the Russian Federation live in territories with excessive air pollution.
After the economic downturn of the 90s, in the past 10 years, the level of pollutant emissions from industry and transport is once again observed in Russia. The pace of utilization of industrial and household waste is at times lagged from the pace of education in slag storages; More than 82 billion tons of production and consumption was accumulated on landfills and landfills. The average of the use and disposal of waste in industry is about 43.3%, solid household waste is almost fully referred to.
The area of \u200b\u200bdisturbed lands in Russia is currently more than 1 million hectares. Of these, agriculture accounts for 10%, non-ferrous metallurgy - 10, coal industry - 9, oil producing - 9, gas - 7, peat - 5, ferrous metallurgy - 4%. At 51 thousand hectares of the restored land passes the same annually into the category of violated.
The extremely unfavorable situation also develops with the accumulation of harmful substances in the soils of urban and industrial areas, since at present, more than 100 thousand dangerous industries and objects are taken into account in the country (of which about 3 thousand chemical), which predetermines very high levels of risks. Technogenic pollution and emergency phenomena with large-scale emissions of highly toxic materials.
Arable soils are contaminated with such elements as mercury, arsenic, lead, boron, copper, tin, bismuth, which fall into the soil in the composition of pesticides, biocides, plant growth stimulants, structural agents. Unconventional fertilizers made from various waste often contain a large set of pollutants with high concentrations.
The use of mineral fertilizers in agriculture is aimed at an increase in the content of plant nutrition elements, an increase in crop yields. However, together with the active substance of the main elements of food in the soil, many different chemicals come with fertilizers, including heavy metals. The latter is due to the presence of toxic impurities in the feedstock, imperfection of production technologies and applying fertilizers. Thus, the cadmium content in mineral fertilizers depends on the type of raw materials from which fertilizers produce: in the apatity of the Kola Peninsula there are a minor amount (0.4-0.6 mg / kg), in Algerian phosphorites - up to 6, and in Moroccan - more 30 mg / kg. The presence of lead and arsenic in Kola Apatity, respectively, 5-12 and 4-15 times lower than in Algeria and Morocco phosphorites.
A.Yu. Idiyev et al. Provides the following data on the content of heavy metals in mineral fertilizers (mg / kg): nitrogen - PB - 2-27; Zn - 1-42; Cu - 1-15; CD - 0.3-1,3; Ni - 0.9; phosphate - respectively 2-27; 23; 10-17; 2.6; 6.5; potash - respectively 196; 182; 186; 0.6; 19.3 and Hg - 0.7 mg / kg, i.e. fertilizers can be a source of pollution of the soil system - plants. For example, with the introduction of mineral fertilizers under the monoculture of winter wheat on the chernozem typical in the dose of N45P60K60 in the soil, PB is 35133 mg / ha, Zn - 29496, Cu - 29982, CD - 1194, Ni - 5563 mg / ha. For a long-term period, their amount can achieve essential values.
Distribution in the landscape of technological sources of metals and metalloids depends on the distance from the source of pollution, from climatic conditions (the strength and direction of winds), from the terrain, from technological factors (waste condition, the method of waste generation to the environment, the height of enterprises ).
Soil contamination occurs when under the environment of technogenic compounds of metals and metalloids in any phase state. In general, aerosol pollution prevails on the planet. At the same time, the largest particles of aerosols (\u003e 2 μm) fall out in close proximity to the source of pollution (within a few kilometers), forming a zone with a maximum concentration of pollutants. Pollution can be traced at a distance of tens of kilometers. The size and shape of the area of \u200b\u200bpollution is determined by the influence of the above factors.
The accumulation of the main part of pollutants is observed mainly in the humus-accumulative soil horizon. They are binding to aluminosilicates, non-silicate minerals, organic substances due to various reactions of interaction. Some of them are held by these components firmly and not only does not participate in migration along the soil profile, but also does not represent hazards for living organisms. The negative environmental consequences of soil pollution are associated with moving compounds of metals and metalloids. Their formation in the soil is due to the concentration of these elements on the surface of the solid phases of soil due to the sorption-desorption reactions, deposition-dissolve, ion exchange, the formation of complex compounds. All these compounds are equilibrium with soil solution and jointly represent the system of soil moving compounds of various chemical elements. The number of absorbed elements and strength to hold them with soils depend on the properties of elements and from the chemical properties of the soil. The influence of these properties on the behavior of metals and metalloids has both general, and specific features. The concentration of absorbed elements is determined by the presence of fine-dispersed clay minerals and organic substances. An increase in acidity is accompanied by an increase in solubility of metals compounds, but limiting the solubility of metalloid compounds. The effect of non-silicate compounds of iron and aluminum on absorption of pollutants depends on the acid-base conditions in the soils.
In the conditions of washing mode, the potential mobility of metals and metalloids is implemented, and they can be carried out beyond the soil profile, being sources of secondary groundwater pollution.
The compounds of heavy metals included in the finest particles (micron and submicron) aerosols can flow into the upper layers of the atmosphere and transferred over long distances measured by thousands of kilometers, i.e. to participate in global transfer of substances.
According to the East Meteorological Synthesizing Center, the pollution of the territory of Russia lead and the cadmium of other countries more than 10 times the pollution of these countries by half-tanta from Russian sources, which is due to the dominance of the Western-Eastern air mass transfer. Leading lead in the European territory of Russia (ETP) every year is: from sources of Ukraine - about 1100 tons, Poland and Belarus - 180-190, Germany - more than 130 tons. Cadmium falling on ETP from the objects of Ukraine every year exceeds 40 tons, Poland - almost 9 , Belarus - 7, Germany - more than 5 tons.
Increasing environmental pollution with heavy metals (TM) is a threat to natural bicompositions and agrocenoses. TM accumulated in the soil is extracted from it by plants and in the trophic chains in increasing concentrations enter the animal organism. Plants accumulate Tm not only from the soil, but also from the air. Depending on the type of plants and the ecological situation, they dominate the effect of soil or air pollution. Therefore, the concentration of Tm in plants may exceed or below their content in the soil. Especially a lot of air lead (up to 95%) absorb leafy vegetables.
At roadside territories, significantly contaminates heavy metal the soil of vehicles, especially lead. At the concentration of it in the soil of 50 mg / kg approximately the tenth of this amount, grassy plants accumulate. Also, plants are actively absorbed by zinc, the amount of which in them can several times higher than its content in the soil.
Heavy metals significantly affect the number, species composition and vital activity of soil microbiota. They inhibit the processes of mineralization and synthesis of various substances in the soils, suppress the breathing of soil microorganisms, cause a microbostic effect and can act as a mutagenic factor.
Most heavy metals in elevated concentrations inhibit the activity of enzymes in the soils: amylases, dehydrogenase, urease, invertases, catalases. Based on this, indices similar to the widely known indicator of LD50 were proposed, in which the concentration of a pollutant is considered to be 50 or 25%, which reduces certain physiological activity, for example, a decrease in CO2 is the ECD50, inhibition of dehydrogenase activity - EC50, suppression of invertase activity by 25%, Reducing the activity of the restoration of trivalent iron - EC50.
S.V. Levin et al. As indicator signs of different levels of soil contamination with heavy metals in real conditions, the following is proposed. The low level of contamination should be set to exceed the background concentrations of heavy metals using adopted chemical analysis methods. On the average level of pollution, the lack of redistribution of members of the initiated microbial community of the soil with an additional introduction to the dose of a polluter equal to the double concentration corresponding to the domain of the homeostasis zone of unpolluted soil. As additional indicator signs, it is appropriate to use a decrease in the activity of nitrogen in the soil and the variability of this process, the reduction of the species wealth and the diversity of the soil microorganisms complex and an increase in the shares of toxic forming forms, epiphytic and pigmented microorganisms. To indicate a high level of contamination, it is most advisable to take into account the reaction to pollution of higher plants. Additional features may be detected in the soil in a high population density of resistant to a particular contaminant forms of microorganisms against a general reduction in the microbiological activity of soil.
In general, in Russia, the average concentration of all TM defined in soils does not exceed 0.5 PDK (CHD). However, the variation coefficient for individual elements is within 69-93%, and the cadmium exceeds 100%. The average lead content in sand and sampling soil is 6.75 mg / kg. The amount of copper, zinc, cadmium is in the range of 0.5-1.0 ADC. Every year, each square meter of soil surface absorbs about 6 kg of chemicals (lead, cadmium, arsenic, copper, zinc, etc.). By the degree of danger, TM is divided into three classes, of which the first refers to high-hazardous substances. It includes PB, Zn, Cu, AS, SE, F, HG. The second moderately dangerous class is represented by, CO, Ni, Mo, Cu, CR, and the third (low hazard) - Ba, V, W, Mn, Sr. Information about the hazardous concentrations of TM gives an analysis of their mobile forms (Table 4.11).

For reclamation of soils contaminated with heavy metals, different methods use different methods, one of which is the use of natural zeolites or sorbentmethrons with its participation. Zeolites have high selectivity in relation to many heavy metals. The effectiveness of these minerals and zeolite-containing rocks for the binding of heavy metals in soils and reducing their receipt to the plants is revealed. As a rule, soils contain zeolites in minor quantities, however, in many countries of the world, the natural zeolites deposits are widespread, and the use of soil detoxification can be economically no costly and environmentally effective, due to improving the agrochemical properties of soils.
The use of 35 and 50 g / kg of the soil of the heylandite Pegasi field (fraction 0.3 mm) on the contaminated chernozem near the zincofavil plant under vegetable crops reduced the content of moving forms of zinc and lead, but at the same time the nitrogen and partially phosphoric potassium nutrition has deteriorated, which reduced their productivity.
According to VS Belousov, introduction to heavy metal polluted soil (10-100 times excess background) 10-20 t / ha Zeolite-containing rocks of the Hadayzhensky field (Krasnodar Territory) containing 27-35% of zeolites (ralbits, heyland), contributed to a decrease in the accumulation of TM in plants : copper and zinc up to 5-14 times, lead and cadmium - up to 2-4 times. It was also revealed that the absence of an explicit correlation relationship between the adsorption properties of the CSP and the effect of metal inactivation, expressed, for example, in relatively smaller indicators of the reduction of lead content in test cultures, despite its very high absorption of CSP in adsorption experiments, is quite expected and is a consequence species differences in plants in the ability to accumulate heavy metals.
In the vegetative experiments on ferrous-podzolic soils (Moscow region), artificially contaminated with lead in the amount of 640 mg Pb / kg, which corresponds to a 10-fold MPC for acidic soils, the use of zeolite of the Sokirnitsky field and the modified Zeolite "Weddone Fos" containing in The quality of the active components of ammonium ions, potassium, magnesium and phosphorus in doses of 0.5% of the soil mass, had a different effect on the agrochemical characteristic of soil, the growth and development of plants. The modified zeolite reduced the acidity of the soil, significantly increased the content of nitrogen and phosphorus plants, increased ammonification activity and the intensity of microbiological processes, ensured the normal vegetation of salad plants, while the introduction of unsaturated zeolite was not effective.
The unsaturated zeolite and the modified zeolite "Wednofos" after 30 and 90 days of the soil composting also did not show their sorption properties in relation to lead. Perhaps 90 days are not enough to pass the process of sorption of lead zeolites, as evidenced by the data of V.G. Mineyev et al. On the manifestation of the sorption effect of zeolites only for the second year after their introduction.
When introducing into brown soils, the semipalatinsky pertedsheye of crushed to a high degree of zeolite dispersion The relative content of the active mineral fraction with high ion exchange properties increased, as a result of which the overall capacity of the absorption of the arable layer increased. The dependence between the dose of zeolites and the amount of adsorbed lead was noted - the maximum dose led to the greatest lead absorption. The effect of zeolites on the adsorption process significantly depended on its grinding. Thus, the adsorption of lead ions when making zeolites with a grinding of 2 mm in the soup soil increased by an average of 3.0; 6.0 and 8.0%; in the medium divine-in 5.0; 8.0 and 11.0%; in a straightfold medium divine - by 2.0; 4.0 and 8.0%, respectively. When using zeolites of a 0.2 mm zeolites, an increase in the amount of absorbed lead was: in the soup soil on average 17, 19 and 21%, in the medium divided - 21, 23 and 26%, in the brainstant and the medium divine - 21, 23 and 25%, respectively.
A.M. Abdujatite on brown soils of the Semipalatinsky Podtyshye also received positive results of the effect of natural zeolites on the environmental stability of soils and their absorption capacity with respect to the lead, a decrease in its phytotoxicity.
According to M.S. Panin and T.I. Gulkina, when studying the influence of various agrochemicals for sorption of copper ions, the soils of this region found that the introduction of organic fertilizers and zeolites contributed to an increase in soil sorption.
In carbonate light-seeded soil contaminated by PB, the product of the combustion of ethyl automotive fuel, 47% of this element detected in the sand fraction. If the PB (II) salts hit in unpolluted clay soil and sandy severe loam in this fraction, only 5-12% PB is provided in this fraction. The introduction of zeolite (clinoptylite) reduces the PB content in the liquid soil phase, which should lead to a decrease in its availability for plants. However, zeolite does not allow to translate metal from the dust and clay fraction into a sandy to prevent its wind removal into the atmosphere with dust.
Natural zeolites are used in environmentally friendly technologies for measuring soils, reducing the content of water-soluble strontium in the soil by 15-75% when making them with phosphogyps, as well as reduce the concentrations of heavy metals. When growing barley, corn and making a mixture of phosphogyps and cliniment, negative phenomena caused by phosphogypsum were eliminated, which had a positive effect on the growth, development and yield of cultures.
In the vegetative experience on polluted soils with a test plant, the barley was studied the influence of zeolites on phosphate bufferity on the background of the introduction into the soil 5, 10 and 20 mg of p / 100 g of soil. The control was noted high intensity of absorption P and low phosphate bufferiness (RVS (P)) at a low dose of P-fertilizer. NH-and Caesolites reduced PBC (P), and the intensity of H2RO4 did not change to the end of the vegetation of plants. The effect of melorantes increased with an increase in the content P in the soil, as a result of which the magnitude of the PBC (P) potential increased twice, which was positively reflected on soil fertility. Zeolithic meliorants harmonize the fertilizer of plants mineral p, while their natural barriers are activated in t. N. Zn acclimatization; As a result, the accumulation of toxicants in test plants decreased.
The cultivation of fruit and berry crops provides regular processing with protective drugs containing heavy metals. Considering that these cultures grow in one place for a long time (dozens of years) in the soils of gardens, as a rule, heavy metals accumulate, negatively affecting the quality of berry products. Perennial studies found that, for example, in gray forest soil under the berries, the gross content of Tm exceeded the regional-background concentration 2 times for PB and Ni, 3 times for Zn, 6 times for CU.
The use of zeolite-containing rocks of the Khaynetsky field to reduce contamination of black currant berries, raspberries and gooseberries is an environmentally and cost-effective event.
In the work of L.I. Leonteva revealed the following feature, which, in our opinion, is very significantly significant. The author found that the maximum decrease in the content of movable forms P and Ni in the gray forest soil is provided by the depositing of the zeolite-containing rock at a dose of 8 and 16 t / ha, and Zn and Cu - 24 t / ha, i.e., there is a differentiated relationship of the element to the amount of sorbent .
The creation of fertilizing compositions and soils from production waste requires special control, in particular the rationing of heavy metals. Therefore, the use of zeolites here is considered to be an effective admission. For example, when studying the peculiarities of the growth and development of asters on the soils created on the basis of the humus layer of the chernozem of the apodoline according to the scheme: control, soil + 100 g / m slag; soil + 100 g / m2 slag + 100 g / m2 zeolite; soil + 100 g / m2 zeolite; soil + 200 g / m2 zeolite; Soil + sewage sediment 100 g / m "+ zeolite 200 g / m2; soil + precipitate 100 g / m2, it has been established that the best for the growth of ASTR was the soil with sediment of wastewater and zeolite.
Evaluating the follow-up to create soils from zeolites, sedimentation of wastewater and slag sections, they determined their effect on the lead concentration, cadmium, chromium, zinc and copper. If in control the number of rolling lead was 13.7% of gross content in the soil, then when making slag, it increased to 15.1%. The use of organic substances sewage sludge reduced the content of moving lead to 12.2%. The greatest effect of lead firmware into low-lifting forms has zeolite, reducing the concentration of mobile forms PB to 8.3%. With the joint action of sewage sediment and zeolite, the amount of rolling lead decreased by 4.2% when using slags. On the fixation of cadmium, a positive effect was provided both zeolite and sewage sediments. In reducing the mobility of copper and zinc in the soils, the zeolite and its combination with organic substances of sewage sediment were largely shown. The organic substance of sewage sediment contributed to an increase in the mobility of nickel and manganese.
Making wastewater precipitation by Lyubertsy Aeration Station into Saddy-podzolic soils led to their pollution TM. TM accumulation coefficients in the polluted OCB soils over moving compounds were 3-10 times higher than the gross content, compared with the soils unpolluted, which indicated the high activity of them with precipitation TM and the availability of them for plants. The maximum reduction of mobility Tm (20-25% of the initial level) was noted when the peat-made mixture was made, which is due to the formation of durable TM complexes with an organic matter. Iron ore, the least effective as a meliorant caused a decrease in the content of moving metal compounds by 5-10%. Zeolite according to the action as a Meliorant occupied an intermediate position. The meliorants used in experiments reduced the mobility of CD, Zn, Cu and CR on average by 10-20%. Thus, the use of meliorants was effectively using TM in soils close to MPC or exceeding permissible concentrations for no more than 10-20%. Melorantes in contaminated soil reduced them to a plant by 15-20%.
Alluvial turf soils of the Western Trans-Baikalia according to the degree of security by mobile forms of microelements defined in ammonium-acetate hoods belong to the highly protected manganese, the average-covered - on zinc and copper, very highly protected - on cobalt. They do not need to use microfertilizers, so making sewage precipitation can lead to soil contamination with toxic elements and requires an environmental-geochemical assessment.
L.L. Ubugunov et al. The effect of sewage sediment (ASS), Mordenites-containing MYXOP-Talinsky deposits (MT) and mineral fertilizers on the content of movable forms of heavy metals in alluvial turf soils was studied. Studies were conducted according to the following scheme: 1) control; 2) N60P60K60 - background; 3) OCB - 15 t / ha; 4) Mt - 15 t / ha; 5) background + arda - 15 t / ha; 6) background + MT 15 t / ha; 7) OCB 7.5 t / ha + MT 7.5 t / ha; 8) OCB / H + MT 5 t / ha; 9) background + arda 7.5 t / ha; 10) background + arda 10 t / ha + MT 5 t / ha. Mineral fertilizers contributed annually, the ASS, MT and mixtures there are once every 3 years.
To estimate the intensity of the accumulation of Tm in the soil, geochemical indicators are used: the concentration coefficient is KC and the contamination total indicator - ZC, defined by formulas:

where C is the concentration of the element in the experimental version, CF is the concentration of the element on control;

Zc \u003d σkc - (n-1),

where n is the number of elements with KC ≥ 1.0.
The results obtained revealed an ambiguous effect of mineral fertilizers, ardent, ardentite-containing tuffs and their mixtures on the content of mobile trace elements in the soil layer 0-20 cm, although it should be noted that in all the experiments their amount did not exceed the MPC level (Table 4.12).
The use of almost all types of fertilizers, with the exception of MT and MT + NPK, led to an increase in the content of manganese. When introduced into the OCB soil, with Mineral Fertilizers, KC reached maximum value (1.24). Zinc accumulation more significantly occurred: KC when making OCB reached the values \u200b\u200bof 1.85-2.27; Mineral fertilizers and Mixes of ASC + MT -1.13-1.27; With the use of zeolites, it decreased to the minimum value - 1.00-1.07. The accumulation of copper and cadmium in the soil did not occur, their maintenance in all versions of experience as a whole was at the level or slightly below the control. Only a minor increase in Cu content (KC - 1.05-1.11) is noted in an option using OCB as in pure form (Var. 3) and on the backdrop of NPK (Var. 5) and CD (KC - 1,13 ) When in the soil of mineral fertilizers (Var. 2) and OCB on their background (Var. 5). The cobalt content has slightly increased when using all kinds of fertilizers (maximum - var. 2, KC -1.30), with the exception of options with the use of zeolites. The maximum nickel concentration (KC - 1.13-1.22) and lead (KC - 1.33) was noted when the OCB and OCB is introduced against the backdrop of NPK (Var. 3, 5), the use of OCB in conjunction with zeolites (Var . 7, 8) reduced this indicator (KC - 1.04 - 1.08).

By the magnitude of the total contamination of heavy metals of the soil layer 0-20 cm (Table 4.12) Types of fertilizers are located in the next ranked row (in brackets - ZC value): OCB + NPK (3.52) → ASS (2.68) - NPK (1.84) → 10СВ + MT + NPK (1.66-1.64) → OC + MT, Var. 8 (1.52) → OC + MT Var. 7 (1.40) → MT + NPK (1.12). The level of total pollution of soils with heavy metals when applied to the soil fertilizer was generally insignificant, compared with the control (ZC<10), тем не менее тенденция накопления TM при использовании осадков сточных вод четко обозначилась, как и эффективное действие морденитсодержащих туфов в снижении содержания подвижных форм тяжелых металлов в почве, а также в повышении качества клубней картофеля.
L.V. Kiryicheva and I.V. The Glazunova was formulated by the following basic requirements for the component composition of the sorbentmethroerates created: the high capacity absorption capacity, the simultaneous presence of organic and mineral components in the composition, physiological neutrality (pH 6.0-7.5), the ability of the composition to adsorb movable forms TM, translating them into fixed Forms, an increased hydro-accumulating composition of the composition, the presence of a structure of the structural agent, the property of the liophilicity and coagulant, the high specific surface, the availability of the feedstock and its low cost, the use (utilization) of commodity waste as part of the sorbent, the manufacturability of the manufacturer of the sorbent, and environmental and environmental neutrality.
Of the 20 compositions of sorbents of natural origin, the authors revealed the most effective, containing 65% sapropel, 25% of zeolite and 10% alumina. This sorbent-meliorant was patented and called "Sorbek" (Patent of the Russian Federation No. 2049107 "Composition for soil aelioration").
The mechanism of the validity of the sorbentmethrhanta, when making it in the soil, is very complex and includes the processes of various physicochemical nature: hemosorption (absorption with the formation of hard-soluble TM compounds); Mechanical absorption (volume absorption of large molecules) and ion exchange processes (substitution in the soil-absorbing complex (PPK) of TM ions on non-toxic ions). The high absorption capacity of the "sorbex" is due to the regulated value of the capacitance of cationic metabolism, the fineness of the structure (large specific surface, up to 160 m2), as well as a stabilizing effect on the pH indicator depending on the nature of the pollution and the reaction of the medium in order to prevent desorption of the most dangerous pollutants.
In the presence of soil moisture in Sorbent there is a partial dissociation and hydrolysis of aluminum sulfate and humic substances that are part of the organic substance of sapropel. Electrolytic dissociation: A12 (SO4) 3⇔2A13 ++ 3SO4B2-; A13 ++ H2O \u003d alone2 + \u003d ON; (R * -COO) 2 Ca ⇔ R - COO- + R - SOX + (R - aliphatic radical of humic substances); R - COO + H2O ⇔ R - Soam + ON0. The cations obtained as a result of hydrolysis are sorbents of anionic forms of pollutants, such as arsenic (V), forming insoluble salts or stable organ-mineral compounds: AL3 + - ASO4B3- \u003d ALASO4; 3R-COOCA ++ ASO4B3- \u003d (R-COOCA) 3 ASO4.
More common cationic forms characteristic of TM form strong chelate complexes with polyphenol groups of humic substances or are sorbed by anions formed during the dissociation of carboxyls, phenolic hydroxyls - functional groups of spropel humic substances in accordance with the reactions presented: 2R - COO + PB2 + \u003d (R - Soo) 2 PB; 2Ar - O + Cu2 + \u003d (AR - O) 2SU (AR aromatic radical of humic substances). Since the organic substance of sapropel is insoluble in water, TM is moving into fixed forms in the form of durable organineral complexes. Sulfate anions precipitate cations, mainly barium or lead: 2pb2 + + 3SO4B2- \u003d PB3 (SO4) 2.
At an anionic complex of spropel humic substances, all two- and trivalent TM cations are sorbed, and Sulfat-non-sulfate immobilizes lead and barium ions. With polyvalent contamination, TM competes between cations and mainly sorbed cations with a higher electrode potential, according to the electrochemical row of metals voltages, therefore sorption codium cation will prevent the presence of nickel, copper, lead and cobalt ion sorption.
The mechanical absorption capacity of "sorbex" is ensured by fineness and significant specific surface area. Pollutants having large molecules, such as pesticides, petroleum products, etc., are mechanically delayed in sorption traps.
The best result was achieved by making a sorbent to the soil, which made it possible to reduce the consumption of TM plants of oats from the soil: Ni - by 7.5 times; Cu - at 1.5; Zn - in 1.9; P - at 2.4; Fe - in 4.4; Mn - 5 times.
To assess the influence of "sorbx" on the receipt of TM in the vegetable products, depending on the total pollution of the soil of A.V. Ilinsky was held vegetative and field experiments. In the vegetation experience, the influence of "sorbex" was studied on the content of oats in the phytomass at different levels of contamination of the znolar chernozem Zn, Cu, Pb and Cd according to the scheme (Table 4.13).

The soil was contaminated by adding chemically pure water-soluble salts and was thoroughly stirred, then exposure was subjected for 7 days. Calculation of Doses of Making TM salts was carried out taking into account background concentrations. The experiment used vegetative vessels with an area of \u200b\u200b364 cm2 with a mass of soil in each vessel 7 kg.
The soil had the following agrochemical indicators RNKCl \u003d 5.1, humus - 5.7% (in Tyurin), phosphorus - 23.5 mg / 100 g and potassium 19.2 mg / 100 g (in Kirsanov). The background content of movable (1M HNO3) forms Zn, Cu, Pb, CD - 4.37; 3.34; 3.0; 0.15 mg / kg, respectively. The duration of the experiment is 2.5 months.
To maintain the optimal humidity of 0.8HV, periodically watered with clean water.
The yield of oats phytomass (Fig. 4.10) in options without making a "sorbex" with extremely dangerous pollution decreases more than 2 times. The use of "sorbex" at the rate of 3.3 kg / m contributed to an increase in the phytomass, compared with control, 2 or more times (Fig. 4.10), as well as a significant reduction in CU, Zn, PB consumption by plants. At the same time, an insignificant increase in the CD content in the oats phytomass occurred (Table 4.14), which corresponds to theoretical prerequisites for the sorption mechanism.

Thus, the introduction of sorbent-meliorants into contaminated soil allows not only to reduce the flow of heavy metals in the plants, improve the agrochemical properties of degraded chernozem, but also increase the productivity of crops.

Federal Agency for Education State Educational Institution

Higher Professional Education "Voronezh State University"

Soil pollution with heavy metals. Methods for monitoring and rationing of polluted soils

Educational and methodical manual for universities

Compilers: H.A. Jullyikan, D.I. Scheglov, N.S. Gorbunova

Publishing and Printing Center of the Voronezh State University

Approved by the Scientific and Methodological Council of the Bio-Soil Faculty of July 4, 2009, Protocol No. 10

Reviewer Dr. Biol. Sciences, prof. L.A. Yablonsky

The educational and methodological manual was prepared at the Department of Soil Science and Land Management of the Bio-Soil Faculty of Voronezh State University.

For specialty 020701 - Soil science

General information about pollution ................................................ ..............................
The concept of man-made anomalies .............................................. .......................
Soil pollution with heavy metals .............................................. ...............
Migration of heavy metals in soil profile .............................................
The concept of soil environmental monitoring ........................................
Indicators of the state of the soils defined by their control ........................
Environmental rationing of the quality of polluted soils ..........................
General requirements for the classification of soils exposed to pollution ......
Literature................................................. .................................................. ........

General information about pollution

Pollutants- These are substances of anthropogenic origin entering the environment in quantities exceeding the natural level of their receipt. Soil pollution- type of anthropogenic degradation, in which the content of chemicals in soils exposed to anthropogenic effects exceeds the natural regional background level. Exceeding the content of certain chemicals in the human environment (compared to natural levels) due to their receipt of anthropogenic sources is an environmental hazard.

The use of chemicals in economic activities and involve them in the cycle of anthropogenic transformations in the environment is constantly growing. The characteristic of the intensity of the extraction and use of chemical elements is technophilicity - the ratio of annual production or production of an element in tons to its Clark in a lithosphere (A.I. Perelman, 1999). High technology is characteristic of the elements most actively used by the person, especially for those whose natural level in the lithosphere is low. High levels of technical philicities are characteristic of such metals such as Bi, Hg, Sb, Pb, Cu, SE, AG, AS, MO, SN, CR, Zn, the need for various types of productions is large. With a low content of these elements in the rocks (10-2 -10-6%) mining them are significant. This leads to extracting from the subsoil of the land of the enormous quantities of ores containing these elements, and to the subsequent global scattering in the environment.

In addition to technology, other quantitative characteristics of technogenesis are also proposed. So, the ratio of the technofilicity of the element to its biofilience (biofee - Clarki concentration of chemical elements in the living substance) M.A. Glazovskaya called destructive activity of technogenesis elements. The destructive activity of the elements of technogenesis characterizes the degree of danger of elements for living organisms. Another quantitative characteristic of anthropogenic involvement of chemical elements in their global cycles on the planet is mobilization factoror factor technogenic enrichmentwhich is calculated as the ratio of the technogenic flow of the chemical element to its natural stream. The level of technogenic enrichment factor, as well as the technofilicity of the elements, is not only an indicator of mobilization of them from the lithosphere to terrestrial natural environments, but also the reflection of the level of emissions of chemical elements with waste generations.

The concept of man-made anomalies

Geochemical anomaly- section of the earth's crust (or surface of the Earth), characterized by substantially increased concentrations of some chemical elements or their compounds compared with the background values \u200b\u200band naturally located relative to the accumulations of minerals. The identification of man-made anomalies is one of the most important eco-geochemical tasks in assessing the state of the environment. Anomalies are formed in the components of the landscape as a result of the receipt of various substances from man-made sources and are some volume, within which the values \u200b\u200bof the anomalous concentrations of elements are more background values. According to the prevalence of A.I. Perelman and N.S. Kasimov (1999) allocate the following man-made anomalies:

1) global - covering the whole globe (for example, increased

2) regional - emerging in certain parts of continents, natural zones and areas as a result of the use of pesticides, mineral fertilizers, acidification of atmospheric precipitation of sulfur compounds, etc.;

3) local - formed in the atmosphere, soils, waters, plants around local man-made sources: plants, mines, etc.

In terms of education, man-made anomalies are divided:

1) on lithochemical (in soils, rocks);

2) hydrogeochemical (in waters);

3) atmogochemical (in the atmosphere, snow);

4) biochemical (in organisms).

According to the duration of the source of pollution, they are divided:

– on short-term (emergency emissions, etc.);

– middle-quality (with termination of impact, for example, termination of the development of mineral deposits);

– long-term stationary (anomalies of factories, cities, agroleandshafts, such as Kma, Norilsk Nickel).

When evaluating man-made anomalies, background areas are chosen away from man-made sources of pollutants, as a rule, more than 30-50 km. One of the criteria of anomalism is the coefficient of technogenic concentration or anomalism of the COP, which is the ratio of the content of the element in the considered an abnormal object to its background content in the components of the landscape.

To assess the impact of the amount of pollutants entering the body, hygienic pollution standards are also used -

delno permissible concentrations. This is the maximum content of a harmful substance in a natural object or product (water, air, soil, food), which does not affect human health or other organisms.

Pollutants on danger are divided into classes (GOST

17.4.1.0283): I class (highly dangerous) - AS, CD, HG, SE, PB, F, benz (a) Pyrene, Zn; Class II (moderately dangerous) - b, co, ni, mo, cu, sb, cr; III class (little dangerous) - Ba, V, W, Mn, Sr, acetophenone.

Soil pollution with heavy metals

Heavy metals (TM) are already ranked second in the degree of danger, yielding pesticides and significantly ahead of such well-known pollutants as carbon dioxide and sulfur. In the future, they can become more dangerous than waste of nuclear power plants and solid waste. Pollution TM is associated with their widespread use in industrial production. In connection with the imperfect cleaning systems, the TM enter the environment, including in the soil, pollution and poisoning it. TM refers to special pollutants, whose observations are mandatory in all environments.

Soil is the main environment in which TM, including from the atmosphere and an aquatic environment. It serves as a source of secondary pollution of surface air and waters falling from it in the world ocean. From the soil TM is assimilated by plants, which then fall into food.

The term "heavy metals", characterizing a wide group of pollutants, has recently received significant distribution. In various scientific and applied works, the authors interpret the meaning of this concept in different ways. In this connection, the number of elements attributable to a group of heavy metals varies widely. As criteria, numerous characteristics are used: atomic weight, density, toxicity, prevalence in the natural environment, the degree of involvement in natural and man-made cycles.

In the works devoted to the problems of pollution of the environment and environmental monitoring, today there are more than 40 elements of the Periodic System D.I. Mendeleev with an atomic mass of over 40 atomic units: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, CD, SN, HG, PB, BI, etc. according to the classification of N. Reimers (1990),

metals with a density of more than 8 g / cm3 should be considered severe. In this case, the following conditions play an important role in categorizing heavy metals: their high toxicity for living organisms in relatively low concentrations, as well as the ability to bioaccumulation and biomagnification. Almost all metals falling under this

(with the exception of lead, mercury, cadmium and bismuth, whose biological role is currently not clear), actively participate in biological processes, are part of many enzymes.

The most powerful waste suppliers enriched with metal, non-ferrous metals (aluminum, alumina, copper-zinc, lead-melted, nickel, titanium, mercury, etc.), as well as for the processing of non-ferrous metals (radio engineering, electrical, instrument-making, Galvanic, etc.).

In the dust of metallurgical industries, RUD processing plants, the concentration of PB, Zn, Bi, Sn can be increased compared to a lithosphere for several orders (up to 10-12), the concentration of CD, V, SB is ten thousand times, CD, Mo, PB, SN, ZN, BI, AG - hundreds of times. Waste of non-ferrous metallurgy enterprises, plants of the paint industry and reinforced concrete structures are enriched with mercury. In the dust of engineering plants, the concentration W, CD, PB (Table 1) is elevated.

Under the influence of emission-enriched emissions, the ranges of landscape pollution are formed mainly at the regional and local levels. The influence of energy enterprises on environmental pollution is due not to the concentration of metals in waste, and their huge amounts. Waste mass, for example, in industrial centers, exceeds their total amount coming from all other sources of pollution. With car exhaust gases, a significant amount of PB is ejected to the environment, which exceeds its receipt with the waste of metallurgical enterprises.

Arable soils are contaminated with such elements as HG, AS, PB, Cu, Sn, Bi, which fall into the soil in the composition of the pesticides, biocides, plant growth stimulants, structural agents. Unconventional fertilizers made from various waste often contain a large set of pollutants with high concentrations. From traditional mineral fertilizers, phosphoric fertilizers contain impurities Mn, Zn, Ni, Cr, Pb, Cu, CD (Gaponyuk, 1985).

The distribution in the landscape of metals entered into the atmosphere from technogenic sources is determined by the distance from the source of pollution, climatic conditions (strength and direction of winds), terrain relief, technological factors (waste condition, method of waste generation into the environment, pipe height of enterprises).

The dispersion of TM depends on the height of the emission source into the atmosphere. According to the calculations of M.E. Berlinda (1975), with high flue pipes, a significant concentration of emissions is created in the surface layer of the atmosphere at a distance of 10-40 heights of the pipe. 6 zones are distinguished around such sources of pollution (Table 2). The exposure area of \u200b\u200bindividual industrial enterprises for the adjacent territory can reach 1000 km2.

table 2

Soil pollution zones around point sources of pollution

			Distance OT	Excess content
			source	tM TM
			dirty in km	schia to the background
		Security zone of the enterprise

Soil pollution zones and their size are closely connected with vectors of dominant winds. Relief, vegetation, urban buildings can change the direction and speed of the surface layer of air. Similar to the zones of soil pollution can be allocated and zones of pollution of vegetable cover.

Migration of heavy metals in soil profile

The accumulation of the main part of pollutants is observed mainly in the humus-accumulative soil horizon, where they are binding to aluminosilicates, non-silicate minerals, organic substances due to various reactions of interaction. The composition and the number of elements held in the soil depend on the content and composition of humus, acid-base and redox conditions, sorption capacity, biological absorption intensity. Part of heavy metals is held with these components firmly and not only does not participate in migration on the soil profile, but also does not represent danger

for living organisms. The negative environmental consequences of soil contamination are associated with moving metal compounds.

IN soil profile limits Technogenic stream of substances meets a number Soil-geochemical barriers. These include carbonate, gypsum, illuvual horizons (illuvial-iron-humus). Some of the high-precipitoxic elements can switch to hard-to-reach compound plants, other elements, mobile in this solagegeochemical setting, can migrate in soil thicker, representing a potential hazard for biota. The mobility of the elements is largely dependent on the acid-base and oxidizing conditions in soils. In neutral soils, the connections of Zn, V, AS, SE, which can be leached during seasonal soil busting.

The accumulation of mobile, especially dangerous for the organisms of the components of the elements depends on the water and air regimes: the smallest accumulation of them is observed in the water-permeable soils of the washing mode, it increases in soils with a rapid mode and maximum in soils with a discharge mode. In evaporative concentration and alkaline reaction in the soil, SE, AS, V can be accumulated in an easily accessible form, and under the reducing medium conditions - Hg as methylated compounds.

However, it should be borne in mind that in the conditions of washing regime, the potential mobility of metals is implemented, and they can be carried out beyond the soil profile, being sources of secondary groundwater pollution.

IN acid soils with a predominance of oxidative conditions (soil of a podzolic row, well-drained) such heavy metals, such as CD and HG, form light-lifting forms. In contrast, PB, AS, SE form low-lifting compounds that can accumulate in humus and illuvial horizons and negatively affect the state of soil biota. If there are s in the composition of pollutants, the secondary hydrogen sulfide medium is created in reducing conditions and many metals form insoluble or underminable sulfides.

IN wetlands MO, V, AS, SE are present in sedentary forms. A significant part of the elements in acidic wetlands is present in relatively moving and dangerous for living agents; These are the compounds PB, CR, NI, CO, CU, Zn, CD and HG. In weakly acidic and neutral soils with good aeration, hard-soluble PB compounds are formed, especially with lime. In neutral soils, the connections of Zn, V, AS, SE, and CD and HG can be delayed in humus and illuvial horizons. As alkalinity increases, the hazard of soil pollution listed elements increases.

The concept of soil environmental monitoring

Soil environmental monitoring - regular system

in the space and soil control time, which gives information about their condition in order to evaluate the past, present and forecast changes in the future. Soil monitoring is aimed at identifying anthropogenic changes in soils, which may end up harm human health. The special role of soil monitoring is due to the fact that all changes in the composition and properties of soil are reflected in the soils of their environmental functions, therefore, in the state of the biosphere.

The fact that in the soil, in contrast to the air of the atmosphere and waters, surface reservoirs, the environmental consequences of anthropogenic effects are usually manifested later, but they are more stable and saved longer. There is a need to evaluate the long-term consequences of this impact, for example, the possibility of mobilizing pollutants in soils, as a result of which the soil from the "depot" of pollutants can turn into their secondary source.

Types of soil environmental monitoring

The selection of soil environmental monitoring species is based on differences in combining informative soil indicators corresponding to the tasks of each of them. Based on the differences in the mechanisms and scales of manifestation of soil degradation, two groups of monitoring types are allocated

ring: First Group -global monitoring, the second is local and regional.

Global Soil Monitoring is an integral part of the global biosphere monitoring. It is conducted to evaluate the effect on the state of soil the environmental consequences of the long-range transfer of pollutants due to the danger of generally slanting pollution of the biosphere and the accompanying global level processes. The results of global or biosphere monitoring characterize global changes in the condition of living organisms on the planet under the influence of human activity.

The purpose of local ice monitoring is to identify the impact of soil degradation on the ecosystems of local and regional levels and directly on the living conditions of a person in its environmental management.

Local monitoringthey are also called sanitary and hygienic or impact. It is aimed at monitoring the level of content in the environment of those pollutants that emit a specific

S. DONAHUE - Soil pollution with heavy metalsSoil-soils are one of the most important components of the agricultural and urban environment, and in both cases, reasonable management is the key to the quality of the soil. This series of technical notes is considering man-made human activity, which causes soil degradation, as well as management methods that protect urban soils. This technical note is devoted to soil pollution with heavy metals.

Metals in the soil

Production, production and use of synthetic substances (for example, pesticides, paints, industrial waste, household and industrial water) can lead to pollution of urban and agricultural land with heavy metals. Heavy metals are also found in nature, but rarely in toxic quantities. Potential soil pollution can be formed in old landfills (especially those used for industrial waste), in old gardens that were used pesticides containing arsenic as an active ingredient, in the fields, which in the past were used under wastewater or municipal precipitation, In areas or around mountain dumps and tailings, industrial areas where chemicals may have been discarded to land in areas from the leeward side of industrial facilities.

Excessive accumulation of heavy metals in soils is toxic for humans and animals. The accumulation of heavy metals is usually chronic (impact for a long period of time), together with food. Acute (immediate) poisoning with heavy metals occurs when swallowed or skin contact. Chronic problems associated with the long-term impact of heavy metals are:

1. Lead - mental disorders.
2. Cadmium - affects the kidneys, liver and gastrointestinal tract.
3. Arsenic - skin diseases affects the kidneys and the central nervous system.

The most common cationic elements are mercury, cadmium, lead, nickel, copper, zinc, chrome and manganese. The most common anionic elements are arsenic, molybdenum, selenium, boron.

Traditional ways to restore contaminated soils

The methods of reclamation of soils and crops can help prevent pollutants from entering the plants, leaving them in the soil. These reclamation methods will not lead to the removal of heavy metals of pollutants, but will help to immobilize them into the soil and reduce the likelihood of negative effects of metals. Please note that the type of metal (cation or anion) must be considered:

1. Increasing the pH of the soil to 6.5 or higher. Cationic metals are more soluble at lower pH levels, so the increase in the pH makes them less accessible to plants and, therefore, are less likely to be included in the tissue of plants and fall into the human body. The increase in the pH has the opposite effect on the anionic elements.
2. Drain in wet soils. Drainage improves soil aeration and will allow metals to oxidize, which makes them less soluble and affordable. The reverse property will be observed for chromium, which is more affordable in oxidized form. The activity of the organic matter is effectively in reducing the availability of chromium.
3. . The use of phosphates. The use of phosphates can lead to a decrease in the availability of cationic metals, but to have the opposite effect on anionic compounds, such as arsenic. Apply phosphates need reasonably because the high level of phosphorus in the soil can lead to water pollution.
4. Careful selection of plants for use on metallically polluted plants move a large amount of metals in the leaves, rather than their fruits or seeds. The greatest risk of food infection in the chain of leafy vegetables (salad or spinach). Another danger is the eating of these plants with cattle.

Installations for environmental cleaning

Studies have shown that plants are effective in purifying contaminated soils (Wenzel and Sovt., 1999). Fortoemonediation is a general term of using plants for removing heavy metals or for soil content in a purest state, without pollutants, such as heavy metals, pesticides, solvents, crude oil, polycyclic aromatic hydrocarbons. For example, steppe grass can stimulate the decay of petroleum products. Wildflowers were recently used to degradation of hydrocarbons from oil spill in Kuwait. Hybrid types of poplars can remove chemical compounds such as TNT, as well as high content of nitrates and pesticides (Brady and Weil, 1999).

Plants for processing metallic contaminated soils

Plants were used to stabilize and remove metals from soil and water. Three mechanisms are used: phytoxtraction, rizoofiltration and phytostabilization.

This article talks about rice filtration and phytostabilization, but the focus focus on phytoxtraction.

Rizoofiltration is adsorption on roots of plants or absorption of pollutants plant roots, which are in the surrounding root zone of solutions (rizosphere).

Rizoofiltration is used to disinfect groundwater. Plants are grown in greenhouses. Polluted water is used to acclimatize plants in the environment. Then, these plants are planted on the site of contaminated groundwater, where the roots are filtered by water and pollutants. As soon as the roots are saturated with contaminated substances, the plants are collected. In Chernobyl, thus used sunflower, to remove radioactive substances in groundwater (EPA, 1998)

Phytostabilization is the use of perennial plants to stabilize or immobilize harmful substances in the soil and groundwater. Metals are absorbed and accumulated in roots are adsorbed on the roots, or deposited in the rhizosphere. Also, these plants can be used to restore vegetation, in places where natural vegetation lacks, thereby reducing the risk of water and wind erosion and leaching. Phytostabilization reduces the mobility of pollutants and prevents further movement of contaminated substances into groundwater or air, and reduces them in food chains.

Phytoxtraction

Phytoextraction is the process of growing plants in a metal polluted soil. The roots move the metals into the above-ground parts of the plants, after which these plants are collected and burned or composed for processing metals. Several growth cycles of crops can be needed to reduce the level of pollution in permissible limits. If the plants burn, the ash must be disposed of on waste landfills.

Plants growing for phytoxtraction are called hyperactors. They absorb an unusually large amount of metal compared to other plants. Hyperactors can contain about 1000 milligrams per kilogram of cobalt, copper, chromium, lead, nickel, and even 10,000 milligrams per kilogram (1%) manganese and zinc in a dry matter (Baker and Brooks, 1989).

Phytoextraction is simpler for metals such as nickel, zinc, copper, because these metals prefer most of the 400 plants of hyperaccumulators. Some plants from the genus Thlaspi (Pennycress) are known to contain about 3% zinc in tissues. These plants can be used as ore due to the high concentration of metal (Brady and Weyl, 1999).

Of all metals, lead is the most common soil pollutant (EPA, 1993). Unfortunately, plants do not accumulate lead in natural conditions. Chelators such as EDTA (ethylenediaminetetraacetic acid) must be added to the soil. EDTA allows plants to extract lead. The most common plant used to extract lead is Indian Mustard (Brassisa Juncea). Phytotech (private research company) reported that they cleared plantations in New Jersey, under industrial standards from 1 to 2, with the help of Indian mustard (Wantanabe, 1997).

Plants can remove zinc, cadmium, lead, selenium and nickel from the soil on projects that are medium and long-term promising.

Traditional cleaning in the territories can cost from $ 10.00 and $ 100.00 per cubic meter (m3), while the removal of contaminated materials can cost from $ 30.00 to $ 300 / m 3. For comparison, phytoxtraction can cost $ 0.05 / m3 (Watanabe, 1997).

Prospects for the future

Fortoemediation was studied in the process of studying small and full-scale applications. Fortoemonediation can move to the sphere of commercialization (Watanabe, 1997). It is predicted that the market phytoment will reach $ 214 to $ 370 million by 2005 (ENVIRONMENTAL SCIENCE & TECHNOLOGY, 1998). Considering the current effectiveness of phytoceediation is best suited for cleaning wider areas in which pollutants are present in low and medium concentrations. Further commercialization of phytoment is needed, further research is needed in order to make sure that plant tissues used for phyto-generation do not have adverse environmental impact, wildlife or person (EPA, 1998). Studies are also necessary to find more efficient bioaccumulators that produce more biomass. There is a need for commercial extraction of metals from plant biomass, so they can be recycled. Fortoemediation is slower than traditional methods for removing heavy metals from the soil, but much cheaper. Warning of soil pollution is much cheaper than the correction of catastrophic consequences.

List of used literature

1.Baker, A.J.M., and r.r. Brooks. 1989. Terrestrial Plants Which Hyperaccumulate Metallic Elements - A Review of their Distribution, Ecology, and Phytochemistry. Biorecovery 1: 81: 126.
2. BRADY, N.C., AND R.R. Weil. 1999. The Nature and Properties of Soils. 12th Ed. PRENTICE HALL. Upper Saddle River, NJ.
3. ENVIRONMENTAL SCIENCE & Technology. 1998. PhyToreMediation; forecasting. ENVIRONMENTAL SCIENCE & TECHNOLOGY. Vol. 32, Issue 17, p.399a.
4. McGrath, S.P. 1998. Phytoextraction for Soil Remediation. p. 261-287. In R. Brooks (Ed.) Plants That Hyperaccumulate Heavy Metals Their Role in PhytoreMediation, MicrobioLogy, Archaeology, Mineral Expliaration and Phytomining. CAB INTERNATIONAL, NEW YORK, NY.
5. Phytotech. 2000. PhyToreMediation Technology.