The main sources of heavy metals are waste from industrial enterprises, various types of power plants, plants from the mining and processing industries, as well as emissions from automotive and some other equipment. Most often, heavy metals enter the environment in the form of aerosols or chemical compounds such as sulfates, sulfides, carbonates, oxides, etc.

Which of the heavy metals most often pollute the soil? The most common heavy metals in industrial waste are mercury, lead and cadmium. Arsenic, zinc, iron, copper and manganese are also often found among harmful emissions.

Heavy metals can enter the environment in insoluble and soluble forms.

Ways of contamination of the soil with heavy metals

The first way of soil contamination with heavy metals is to get into the water and further spread of this water in the soil.

Another option is for heavy metals to enter the atmosphere and precipitate through dry deposition or wet deposition.

Interaction of soil with heavy metals

The soil is an adsorbent of various types of chemical elements, including heavy metals. For a long period they are in the ground, undergoing gradual decontamination. For some heavy metals, these periods can be several hundred or even thousands of years.

Ions of heavy and other metals can react with soil components, being utilized by leaching, through erosion, deflation, and through plants.

What are the methods for determining heavy metals in soil?

First of all, it must be understood that the composition of the soil is heterogeneous, therefore, even on the same land plot, soil indicators can vary greatly in its various parts. Therefore, you need to take several samples and either examine each separately, or mix them into a single mass and take a sample for analysis from there.

The number of methods for determining metals in soil is quite large, for example, some of them:

• method for determining movable forms.
• method for determining exchange forms.
• method for detection of acid-soluble (technogenic) forms.
• gross content method.

Using these techniques, the process of extracting metals from the soil is carried out. Subsequently, it is necessary to determine the percentage of certain metals in the extract itself, for which three main technologies are used:

2) Mass spectrometry with inductively coupled plasma.

3) Electrochemical methods.

The device for the corresponding technology is selected depending on which element is being studied and what its concentration is expected in the soil extract.

Spectrometric methods for studying heavy metals in soil

1) Atomic absorption spectrometry.

The soil sample is dissolved in a special solvent, after which the reagent binds to a certain metal, precipitates, dries and ignites to make the weight constant. Then weighing is carried out using an analytical balance.

The disadvantages of this method include a significant amount of time required for analysis, and a high level of researcher qualification.

2) Atomic absorption spectrometry with plasma atomization.

This is a more common method that allows you to determine several different metals at once in one go. It also differs in accuracy. The essence of the method is as follows: the sample must be transferred to a gaseous atomic state, then the degree of absorption of radiation by atoms of gases - ultraviolet or visible - is analyzed.

Electrochemical methods for the study of heavy metals in soil

The preparatory stage consists in dissolving the soil sample in an aqueous solution. In the future, such technologies for the determination of heavy metals in it are used:

• potentiometry.
• voltammetry.
• conductometry.
• coulometry.

Federal Service for Supervision of Consumer Rights Protection and Human Welfare

2.1.7. SOIL, CLEANING OF POPULATED PLACES, PRODUCTION AND CONSUMPTION WASTE SANITARY PROTECTION OF SOIL

Maximum Permissible Concentrations (MACs) of Chemical Substances in Soil

Hygiene standards
GN 2.1.7.2041-06

1. Prepared by a team of authors consisting of: N.V. Rusakov, I.A. Kryatov, N.I. Tonkopiy, Zh.Zh. Gumarova, N.V. Pirtakhia (State Research Institute of Human Ecology and Environmental Hygiene named after A.N. Sysin, Russian Academy of Medical Sciences); A.P. Vesele (Federal Service for Supervision of Consumer Rights Protection and Human Welfare).

2. Recommended for approval by the Bureau of the Commission on State Sanitary and Epidemiological Regulation under the Federal Service for Supervision of Consumer Rights Protection and Human Welfare (Minutes No. 2 of June 16, 2005).

3. Approved by the Head of the Federal Service for Supervision of Consumer Rights Protection and Human Welfare, Chief State Sanitary Doctor of the Russian Federation G.G. Onishenko January 19, 2006

4. Put into effect by the Decree of the Chief State Sanitary Doctor of the Russian Federation dated January 23, 2006 No. 1 from April 1, 2006.

5. Introduced to replace the hygienic standards "List of maximum allowable concentrations (MPC) and approximate allowable amounts (APC) of chemicals in the soil" No. 6229-91 and GN 2.1.7.020-94 (Supplement 1 to No. 6229-91).

6. Registered with the Ministry of Justice of the Russian Federation (registration number 7470 dated February 7, 2006).

Federal Law of the Russian Federation
"On the sanitary and epidemiological well-being of the population"
No. 52-FZMarch 30, 1999

“State sanitary and epidemiological rules and regulations (hereinafter referred to as sanitary rules) are regulatory legal acts that establish sanitary and epidemiological requirements (including criteria for the safety and (or) harmlessness of environmental factors for humans, hygienic and other standards), non-compliance with which creates threat to human life or health, as well as the threat of the emergence and spread of diseases” (Article 1).

“Compliance with sanitary rules is mandatory for citizens, individual entrepreneurs and legal entities” (Article 39, paragraph 3).

CHIEF STATE SANITARY PHYSICIAN OF THE RUSSIAN FEDERATION

RESOLUTION

01/23/06 Moscow №1

About the implementation
hygiene standards
GN 2.1.7.2041-06

On the basis of Federal Law No. 52-FZ of March 30, 1999 “On the Sanitary and Epidemiological Welfare of the Population” (Collected Legislation of the Russian Federation, 1999, No. 14, Art. 1650; 2003, No. 2, Art. 167; No. 27, Art. 2700 ; 2004, No. 35, Art. 3607) and the Regulations on State Sanitary and Epidemiological Rationing, approved by Decree of the Government of the Russian Federation No. 554 dated July 24, 2000 (Collected Legislation of the Russian Federation, 2000, No. 31, Art. 3295), as amended Decree of the Government of the Russian Federation of September 15, 2005 No. 569 (Collected Legislation of the Russian Federation, 2005, No. 39, Art. 3953)

RESOLVE:

1. To put into effect from April 1, 2006, the hygienic standards GN 2.1.7.2041-06 "Maximum Permissible Concentrations (MPC) of chemicals in the soil", approved by the Chief State Sanitary Doctor of the Russian Federation on January 19, 2006.

G.G. Onishchenko

APPROVE

Head of the Federal Service
on supervision in the field of protection of rights
consumers and human well-being,
Chief State Sanitary
doctor of the Russian Federation

G.G. Onishchenko

2.1.7. SOIL, CLEANING OF POPULATED PLACES, PRODUCTION AND CONSUMPTION WASTE, SANITARY PROTECTION OF SOIL

Maximum Permissible Concentrations (MACs) of Chemical Substances in Soil

Hygiene standards
GN 2.1.7.2041-06

I. General provisions and scope

1.1. The hygienic standards "Maximum Permissible Concentrations (MACs) of Chemical Substances in the Soil" (hereinafter referred to as the standards) were developed in accordance with the Federal Law of March 30, 1999 N 52-FZ "On the Sanitary and Epidemiological Welfare of the Population" (Sobraniye Zakonodatelstva Rossiyskoy Federatsii, 1999, N 14, article 1650; 2003, N 2, article 167; N 27, article 2700; 2004, N 35) and the Regulations on state sanitary and epidemiological regulation, approved by Decree of the Government of the Russian Federation of July 24, 2000 N 554 (Collection of Legislation of the Russian Federation, 2000, N 31, art. 3295) as amended by the Decree of the Government of the Russian Federation of September 15, 2005 N 569 (Sobraniye Zakonodatelstva Rossiyskoy Federatsii, 2005, N 39, art. 3953)

1.2. These standards are valid throughout the Russian Federation and establish the maximum permissible concentrations of chemicals in the soil of various types of land use.

1.3. The standards apply to the soils of settlements, agricultural land, sanitary protection zones of water supply sources, the territory of resort areas and individual institutions.

1.4. These standards have been developed on the basis of complex experimental studies of the danger of the indirect impact of a soil pollutant on human health, as well as taking into account its toxicity, epidemiological studies and international standardization experience.

1.5. Compliance with hygiene standards is mandatory for citizens, individual entrepreneurs and legal entities.

II. Maximum Permissible Concentrations (MACs) of Chemical Substances in Soil

	Substance name			MPC value (mg/kg) taking into account the background (clark)	The limiting indicator of harmfulness
Gross content
	Benz/a/pyrene				general sanitary
					Air migration
					Air migration
					general sanitary
	Vanadium + manganese	7440-62-2+7439-96-5			general sanitary
	Dimethylbenzenes (1,2-dimethylbenzene; 1,3-dimethylbenzene; 1,4-dimethylbenzene)				Translocation
	Complex granular fertilizers (KGU)				Water migration
	Complex liquid fertilizers (KJU)				Water migration
	Manganese				general sanitary
	Metanal				Air migration
	Methylbenzene				Air migration
	(1-methylethenyl)benzene				Air migration
	(1-methylethyl)benzene				Air migration
	(1-methylethyl)benzene + (1-methylethenyl)benzene	98-82-8 + 25013-15-4	С9Н12 + С9Н10		Air migration
					Translocation
	Nitrates (according to NO3)				Water migration
					Water migration
					general sanitary
					Translocation
					general sanitary
	Lead + mercury	7439-92-1 + 7439-97-6			Translocation
					general sanitary
	Sulfuric acid (by S)				general sanitary
	Hydrogen sulfide (by S)				Air migration
	Superphosphate (by P2O5)				Translocation
					Water migration
	Furan-2-carbaldehyde				general sanitary
	Potassium chloride (by K2O)				Water migration
	Chrome Hexavalent				general sanitary
					Air migration
	Ethenylbenzene				Air migration
Movable form
					general sanitary
	Manganese recoverable with 0.1 N H2SO4:
	Chernozem
	Sod-podzolic:
	Retrievable with ammonium acetate buffer pH 4.8:				general sanitary
	Chernozem
	Sod-podzolic:
					general sanitary
					general sanitary
					general sanitary
					Translocation
	Chromium trivalent5				general sanitary
					Translocation
Water soluble form
					Translocation

Notes.

1. KGU - complex granular fertilizers of composition N:P:K=64:0:15. MPC KGU is controlled by the content of nitrates in the soil, which should not exceed 76.8 mg/kg of absolutely dry soil.

KZhU - complex liquid fertilizers of the composition N:P:K=10:34:0 TU 6-08-290-74 with manganese additives not more than 0.6% of the total mass. MPC KZhU is controlled by the content of mobile phosphates in the soil, which should not exceed 27.2 mg/kg of absolutely dry soil.

2. Standards for arsenic and lead for different types of soils are presented as approximate permissible concentrations (AEC) in another document.

3. MPC OFU is controlled by the content of benzo/a/pyrene in the soil, which should not exceed the MPC of benzo/a/pyrene.

4. The mobile form of cobalt is extracted from the soil with an acetate-sodium buffer solution with pH 3.5 and pH 4.7 for gray soils and an acetate-ammonium buffer solution with pH 4.8 for other soil types.

5. The mobile form of the element is extracted from the soil with an ammonium acetate buffer solution with a pH of 4.8.

6. The mobile form of fluorine is extracted from soil with pH £ 6.5 0.006 N HCl, with pH >6.5 - 0.03 N K2SO4.

Notes to Section II

The names of individual substances in alphabetical order are given, where possible, in accordance with the rules of the International Union of Pure Applied Chemistry (IUPAC) (column 2) and are provided with Chemical Abstracts Service (CAS) registration numbers (column 3) to facilitate the identification of substances.

Column 4 shows the formulas of substances.

The values ​​of the Standards are given in milligrams of a substance per kilogram of soil (mg/kg) - column 5 - for gross and mobile forms of their content in the soil.

The limiting indicator of harmfulness is indicated (column 6), according to which the following standards are established: air migration (air migration), water migration (water migration), general sanitary or translocation.

For ease of use of the standards, an index of main synonyms (Appendix 1), formulas of substances (Appendix 2) and CAS numbers (Appendix 3) is provided.

1. GOST 26204-84, GOST 28213-84 “Soils. Methods of Analysis".

2. Dmitriev M.T., Kaznina N.I., Pinigina I.A. Sanitary-chemical analysis of pollutants in the environment: a Handbook. Moscow: Chemistry, 1989.

3. Method for determination of furfural in soil No. 012-17/145 /MZ UzSSR dated 24.03.87. Tashkent, 1987.

4. Guidelines for the qualitative and quantitative determination of carcinogenic polycyclic hydrocarbons in products of complex composition No. 1423-76 dated 12.05.76. M., 1976.

5. Guidelines for sampling from environmental objects and preparing them for the subsequent determination of carcinogenic polycyclic aromatic hydrocarbons: No. 1424-76 dated 12.05.76.

6. Maximum permissible concentrations of chemicals in the soil: No. 1968-79 /MZ USSR of 21.02.79. M., 1979.

7. Maximum permissible concentrations of chemicals in the soil: No. 2264-80 dated 10.30.80 / USSR Ministry of Health. M., 1980.

PAGE_BREAK-- heavy metals, which characterizes a wide group of pollutants, has recently become widespread. In various scientific and applied works, the authors interpret the meaning of this concept in different ways. In this regard, the number of elements assigned to the group of heavy metals varies over a wide range. Numerous characteristics are used as membership criteria: atomic mass, density, toxicity, prevalence in the natural environment, the degree of involvement in natural and technogenic cycles. In some cases, the definition of heavy metals includes elements that are brittle (for example, bismuth) or metalloids (for example, arsenic).

In the works devoted to the problems of environmental pollution and environmental monitoring, to date, to heavy metals include more than 40 metals of the periodic system D.I. Mendeleev with an atomic mass of more than 50 atomic units: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, Sn, Hg, Pb, Bi etc. At the same time, the following conditions play an important role in the categorization of heavy metals: their high toxicity to living organisms in relatively low concentrations, as well as their ability to bioaccumulate and biomagnify. Almost all metals that fall under this definition (with the exception of lead, mercury, cadmium and bismuth, whose biological role is currently not clear), are actively involved in biological processes and are part of many enzymes. According to the classification of N. Reimers, metals with a density of more than 8 g/cm3 should be considered heavy. Thus, heavy metals are Pb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg.

Formally defined heavy metals corresponds to a large number of elements. However, according to researchers involved in practical activities related to the organization of observations of the state and pollution of the environment, the compounds of these elements are far from equivalent as pollutants. Therefore, in many works there is a narrowing of the scope of the group of heavy metals, in accordance with the priority criteria, due to the direction and specifics of the work. So, in the already classic works of Yu.A. Israel in the list of chemicals to be determined in natural media at background stations in biosphere reserves, in the section heavy metals named Pb, Hg, Cd, As. On the other hand, according to the decision of the Task Force on Heavy Metal Emissions, which operates under the auspices of the United Nations Economic Commission for Europe and collects and analyzes information on pollutant emissions in European countries, only Zn, As, Se and Sb were assigned to heavy metals. According to the definition of N. Reimers, noble and rare metals stand apart from heavy metals, respectively, remain only Pb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg. In applied work, heavy metals are most often added Pt, Ag, W, Fe, Au, Mn.

Metal ions are indispensable components of natural water bodies. Depending on the environmental conditions (pH, redox potential, the presence of ligands), they exist in different degrees of oxidation and are part of a variety of inorganic and organometallic compounds, which can be truly dissolved, colloidal-dispersed, or be part of mineral and organic suspensions.

The truly dissolved forms of metals, in turn, are very diverse, which is associated with the processes of hydrolysis, hydrolytic polymerization (formation of polynuclear hydroxo complexes), and complexation with various ligands. Accordingly, both the catalytic properties of metals and the availability for aquatic microorganisms depend on the forms of their existence in the aquatic ecosystem.

Many metals form fairly strong complexes with organic matter; these complexes are one of the most important forms of element migration in natural waters. Most organic complexes are formed by the chelate cycle and are stable. The complexes formed by soil acids with salts of iron, aluminum, titanium, uranium, vanadium, copper, molybdenum and other heavy metals are relatively well soluble in neutral, slightly acidic and slightly alkaline media. Therefore, organometallic complexes are capable of migrating in natural waters over very considerable distances. This is especially important for low-mineralized and, first of all, surface waters, in which the formation of other complexes is impossible.

To understand the factors that regulate the metal concentration in natural waters, their chemical reactivity, bioavailability and toxicity, it is necessary to know not only the total content, but also the proportion of free and bound metal forms.

The transition of metals in an aqueous medium to the metal complex form has three consequences:

1. There may be an increase in the total concentration of metal ions due to its transition into solution from bottom sediments;

2. The membrane permeability of complex ions can differ significantly from the permeability of hydrated ions;

3. The toxicity of the metal as a result of complexation can change greatly.

So, chelate forms Cu, Cd, Hg less toxic than free ions. To understand the factors that regulate the metal concentration in natural waters, their chemical reactivity, bioavailability and toxicity, it is necessary to know not only the total content, but also the proportion of bound and free forms.

The sources of water pollution with heavy metals are wastewater from galvanizing shops, mining, ferrous and non-ferrous metallurgy, and machine-building plants. Heavy metals are found in fertilizers and pesticides and can enter water bodies along with runoff from agricultural land.

An increase in the concentration of heavy metals in natural waters is often associated with other types of pollution, such as acidification. The precipitation of acid precipitation contributes to a decrease in the pH value and the transition of metals from a state adsorbed on mineral and organic substances to a free state.

First of all, of interest are those metals that pollute the atmosphere the most due to their use in significant volumes in production activities and, as a result of accumulation in the external environment, pose a serious danger in terms of their biological activity and toxic properties. These include lead, mercury, cadmium, zinc, bismuth, cobalt, nickel, copper, tin, antimony, vanadium, manganese, chromium, molybdenum and arsenic.
Biogeochemical properties of heavy metals

H - high, Y - moderate, H - low

Vanadium.

Vanadium is predominantly in a dispersed state and is found in iron ores, oil, asphalt, bitumen, oil shale, coal, etc. One of the main sources of vanadium pollution of natural waters is oil and its products.

It occurs in natural waters in very low concentrations: in river water 0.2 - 4.5 µg/dm3, in sea water - an average of 2 µg/dm3

In water it forms stable anionic complexes (V4O12)4- and (V10O26)6-. In the migration of vanadium, the role of its dissolved complex compounds with organic substances, especially with humic acids, is essential.

Elevated concentrations of vanadium are harmful to human health. MPCv of vanadium is 0.1 mg/dm3 (the limiting indicator of harmfulness is sanitary-toxicological), MPCvr is 0.001 mg/dm3.

The natural sources of bismuth entering natural waters are the processes of leaching of bismuth-containing minerals. The source of entry into natural waters can also be wastewater from pharmaceutical and perfume industries, some glass industry enterprises.

It is found in unpolluted surface waters in submicrogram concentrations. The highest concentration was found in groundwater and is 20 µg/dm3, in marine waters - 0.02 µg/dm3. MPCv is 0.1 mg/dm3

The main sources of iron compounds in surface waters are the processes of chemical weathering of rocks, accompanied by their mechanical destruction and dissolution. In the process of interaction with mineral and organic substances contained in natural waters, a complex complex of iron compounds is formed, which are in water in a dissolved, colloidal and suspended state. Significant amounts of iron come with underground runoff and with wastewater from enterprises of the metallurgical, metalworking, textile, paint and varnish industries and with agricultural effluents.

Phase equilibria depend on the chemical composition of water, pH, Eh, and, to some extent, temperature. In routine analysis weighted form emit particles with a size of more than 0.45 microns. It is predominantly iron-bearing minerals, iron oxide hydrate and iron compounds adsorbed on suspensions. Truly dissolved and colloidal form are usually considered together. Dissolved iron represented by compounds in ionic form, in the form of a hydroxocomplex and complexes with dissolved inorganic and organic substances of natural waters. In the ionic form, mainly Fe(II) migrates, and Fe(III) in the absence of complexing substances cannot be in a significant amount in a dissolved state.

Iron is found mainly in waters with low Eh values.

As a result of chemical and biochemical (with the participation of iron bacteria) oxidation, Fe(II) passes into Fe(III), which, upon hydrolysis, precipitates in the form of Fe(OH)3. Both Fe(II) and Fe(III) tend to form hydroxo complexes of the type +, 4+, +, 3+, - and others that coexist in solution at different concentrations depending on pH and generally determine the state of the iron-hydroxyl system. The main form of occurrence of Fe(III) in surface waters is its complex compounds with dissolved inorganic and organic compounds, mainly humic substances. At pH = 8.0, the main form is Fe(OH)3. The colloidal form of iron is the least studied; it is iron oxide hydrate Fe(OH)3 and complexes with organic substances.

The content of iron in the surface waters of the land is tenths of a milligram, near the swamps - a few milligrams. An increased content of iron is observed in swamp waters, in which it is found in the form of complexes with salts of humic acids - humates. The highest concentrations of iron (up to several tens and hundreds of milligrams per 1 dm3) are observed in groundwater with low pH values.

Being a biologically active element, iron to a certain extent affects the intensity of phytoplankton development and the qualitative composition of the microflora in the reservoir.

Iron concentrations are subject to marked seasonal fluctuations. Usually, in reservoirs with high biological productivity, during the period of summer and winter stagnation, an increase in the concentration of iron in the bottom layers of water is noticeable. The autumn-spring mixing of water masses (homothermia) is accompanied by the oxidation of Fe(II) to Fe(III) and the precipitation of the latter in the form of Fe(OH)3.

It enters natural waters during the leaching of soils, polymetallic and copper ores, as a result of the decomposition of aquatic organisms capable of accumulating it. Cadmium compounds are carried into surface water with wastewater from lead-zinc plants, ore-dressing plants, a number of chemical enterprises (sulfuric acid production), galvanic production, and also with mine waters. The decrease in the concentration of dissolved cadmium compounds occurs due to the processes of sorption, precipitation of cadmium hydroxide and carbonate and their consumption by aquatic organisms.

Dissolved forms of cadmium in natural waters are mainly mineral and organo-mineral complexes. The main suspended form of cadmium is its adsorbed compounds. A significant part of cadmium can migrate within the cells of aquatic organisms.

In river uncontaminated and slightly polluted waters, cadmium is contained in submicrogram concentrations; in polluted and waste waters, the concentration of cadmium can reach tens of micrograms per 1 dm3.

Cadmium compounds play an important role in the life of animals and humans. It is toxic in high concentrations, especially in combination with other toxic substances.

MPCv is 0.001 mg/dm3, MPCvr is 0.0005 mg/dm3 (the limiting sign of harmfulness is toxicological).

Cobalt compounds enter natural waters as a result of their leaching from copper pyrite and other ores, from soils during the decomposition of organisms and plants, as well as with wastewater from metallurgical, metalworking and chemical plants. Some amounts of cobalt come from soils as a result of the decomposition of plant and animal organisms.

Cobalt compounds in natural waters are in a dissolved and suspended state, the quantitative ratio between which is determined by the chemical composition of water, temperature and pH values. Dissolved forms are represented mainly by complex compounds, incl. with organic matter in natural waters. Divalent cobalt compounds are most characteristic of surface waters. In the presence of oxidizing agents, trivalent cobalt can exist in appreciable concentrations.

Cobalt is one of the biologically active elements and is always found in the body of animals and plants. Insufficient content of cobalt in plants is associated with its insufficient content in soils, which contributes to the development of anemia in animals (taiga-forest non-chernozem zone). As part of vitamin B12, cobalt has a very active effect on the intake of nitrogenous substances, an increase in the content of chlorophyll and ascorbic acid, activates biosynthesis and increases the content of protein nitrogen in plants. However, elevated concentrations of cobalt compounds are toxic.

In unpolluted and slightly polluted river waters, its content varies from tenths to thousandths of a milligram per 1 dm3, the average content in sea water is 0.5 μg/dm3. MPCv is 0.1 mg/dm3, MPCv is 0.01 mg/dm3.

Manganese

Manganese enters surface waters as a result of leaching of ferromanganese ores and other minerals containing manganese (pyrolusite, psilomelane, brownite, manganite, black ocher). Significant amounts of manganese come from the decomposition of aquatic animals and plant organisms, especially blue-green, diatoms and higher aquatic plants. Manganese compounds are discharged into reservoirs with wastewater from manganese processing plants, metallurgical plants, chemical industry enterprises and mine waters.

A decrease in the concentration of manganese ions in natural waters occurs as a result of the oxidation of Mn(II) to MnO2 and other high-valent oxides that precipitate. The main parameters that determine the oxidation reaction are the concentration of dissolved oxygen, pH value and temperature. The concentration of dissolved manganese compounds decreases due to their utilization by algae.

The main form of migration of manganese compounds in surface waters is suspensions, the composition of which is determined in turn by the composition of rocks drained by waters, as well as colloidal hydroxides of heavy metals and sorbed manganese compounds. Of essential importance in the migration of manganese in dissolved and colloidal forms are organic substances and the processes of complex formation of manganese with inorganic and organic ligands. Mn(II) forms soluble complexes with bicarbonates and sulfates. Complexes of manganese with a chloride ion are rare. Complex compounds of Mn(II) with organic substances are usually less stable than with other transition metals. These include compounds with amines, organic acids, amino acids and humic substances. Mn(III) in high concentrations can be in a dissolved state only in the presence of strong complexing agents; Mn(YII) does not occur in natural waters.

In river waters, the manganese content usually ranges from 1 to 160 µg/dm3, the average content in sea waters is 2 µg/dm3, in underground waters - n.102 - n.103 µg/dm3.

The concentration of manganese in surface waters is subject to seasonal fluctuations.

The factors determining changes in manganese concentrations are the ratio between surface and underground runoff, the intensity of its consumption during photosynthesis, the decomposition of phytoplankton, microorganisms and higher aquatic vegetation, as well as the processes of its deposition on the bottom of water bodies.

The role of manganese in the life of higher plants and algae in water bodies is very large. Manganese contributes to the utilization of CO2 by plants, which increases the intensity of photosynthesis, participates in the processes of nitrate reduction and nitrogen assimilation by plants. Manganese promotes the transition of active Fe(II) to Fe(III), which protects the cell from poisoning, accelerates the growth of organisms, etc. The important ecological and physiological role of manganese necessitates the study and distribution of manganese in natural waters.

For water bodies for sanitary use, MPCv (according to the manganese ion) is set equal to 0.1 mg/dm3.

Below are maps of the distribution of average concentrations of metals: manganese, copper, nickel and lead, built according to observational data for 1989 - 1993. in 123 cities. The use of more recent data is assumed to be inappropriate, since due to the reduction in production, the concentrations of suspended solids and, accordingly, metals have significantly decreased.

Impact on health. Many metals are a constituent of dust and have a significant impact on health.

Manganese enters the atmosphere from emissions from ferrous metallurgy enterprises (60% of all manganese emissions), mechanical engineering and metalworking (23%), non-ferrous metallurgy (9%), numerous small sources, for example, from welding.

High concentrations of manganese lead to the appearance of neurotoxic effects, progressive damage to the central nervous system, pneumonia.
The highest concentrations of manganese (0.57 - 0.66 µg/m3) are observed in large centers of metallurgy: in Lipetsk and Cherepovets, as well as in Magadan. Most of the cities with high concentrations of Mn (0.23 - 0.69 µg/m3) are concentrated on the Kola Peninsula: Zapolyarny, Kandalaksha, Monchegorsk, Olenegorsk (see map).

For 1991 - 1994 manganese emissions from industrial sources decreased by 62%, average concentrations - by 48%.

Copper is one of the most important trace elements. The physiological activity of copper is associated mainly with its inclusion in the composition of the active centers of redox enzymes. Insufficient copper content in soils adversely affects the synthesis of proteins, fats and vitamins and contributes to the infertility of plant organisms. Copper is involved in the process of photosynthesis and affects the absorption of nitrogen by plants. At the same time, excessive concentrations of copper have an adverse effect on plant and animal organisms.

Cu(II) compounds are the most common in natural waters. Of the Cu(I) compounds, Cu2O, Cu2S, and CuCl, which are sparingly soluble in water, are the most common. In the presence of ligands in an aqueous medium, along with the equilibrium of hydroxide dissociation, it is necessary to take into account the formation of various complex forms that are in equilibrium with metal aqua ions.

The main source of copper entering natural waters is wastewater from chemical and metallurgical industries, mine waters, and aldehyde reagents used to kill algae. Copper can form as a result of corrosion of copper pipes and other structures used in water systems. In groundwater, the copper content is due to the interaction of water with rocks containing it (chalcopyrite, chalcocite, covellite, bornite, malachite, azurite, chrysacolla, brotantine).

The maximum permissible concentration of copper in the water of reservoirs for sanitary and household water use is 0.1 mg/dm3 (the limiting sign of harmfulness is general sanitary), in the water of fishery reservoirs it is 0.001 mg/dm3.

Town

Norilsk

Monchegorsk

Krasnouralsk

Kolchugino

Zapolyarny

Emissions М (thousand tons/year) of copper oxide and average annual concentrations q (µg/m3) of copper.

Copper enters the air with emissions from metallurgical industries. In particulate matter emissions, it is contained mainly in the form of compounds, mainly copper oxide.

Non-ferrous metallurgy enterprises account for 98.7% of all anthropogenic emissions of this metal, of which 71% are carried out by enterprises of the Norilsk Nickel concern located in Zapolyarny and Nikel, Monchegorsk and Norilsk, and about 25% of copper emissions are carried out in Revda, Krasnouralsk , Kolchugino and others.

High concentrations of copper lead to intoxication, anemia and hepatitis.

As can be seen from the map, the highest concentrations of copper are noted in the cities of Lipetsk and Rudnaya Pristan. Copper concentrations were also increased in the cities of the Kola Peninsula, in Zapolyarny, Monchegorsk, Nikel, Olenegorsk, and also in Norilsk.

Emissions of copper from industrial sources decreased by 34%, average concentrations - by 42%.

Molybdenum

Molybdenum compounds enter surface waters as a result of their leaching from exogenous minerals containing molybdenum. Molybdenum also enters water bodies with wastewater from processing plants and non-ferrous metallurgy enterprises. The decrease in the concentrations of molybdenum compounds occurs as a result of the precipitation of sparingly soluble compounds, the processes of adsorption by mineral suspensions and consumption by plant aquatic organisms.

Molybdenum in surface waters is mainly in the form MoO42-. It is highly probable that it exists in the form of organomineral complexes. The possibility of some accumulation in the colloidal state follows from the fact that the products of molybdenite oxidation are loose finely dispersed substances.

In river waters, molybdenum is found in concentrations from 2.1 to 10.6 µg/dm3. Sea water contains an average of 10 µg/dm3 of molybdenum.

In small quantities, molybdenum is necessary for the normal development of plant and animal organisms. Molybdenum is part of the enzyme xanthine oxidase. With a deficiency of molybdenum, the enzyme is formed in insufficient quantities, which causes negative reactions in the body. In high concentrations, molybdenum is harmful. With an excess of molybdenum, metabolism is disturbed.

The maximum permissible concentration of molybdenum in water bodies for sanitary use is 0.25 mg/dm3.

Arsenic enters natural waters from mineral springs, areas of arsenic mineralization (arsenic pyrites, realgar, orpiment), as well as from zones of oxidation of rocks of polymetallic, copper-cobalt and tungsten types. A certain amount of arsenic comes from soils, as well as from the decomposition of plant and animal organisms. Consumption of arsenic by aquatic organisms is one of the reasons for the decrease in its concentration in water, which is most clearly manifested during the period of intensive development of plankton.

Significant amounts of arsenic enter water bodies with wastewater from processing plants, waste from the production of dyes, tanneries and pesticide factories, as well as from agricultural lands where pesticides are used.

In natural waters, arsenic compounds are in a dissolved and suspended state, the ratio between which is determined by the chemical composition of water and pH values. In dissolved form, arsenic occurs in tri- and pentavalent forms, mainly as anions.

In unpolluted river waters, arsenic is usually found in microgram concentrations. In mineral waters, its concentration can reach several milligrams per 1 dm3, in sea waters it contains on average 3 µg/dm3, in underground waters it occurs in concentrations of n.105 µg/dm3. Arsenic compounds in high concentrations are toxic to the body of animals and humans: they inhibit oxidative processes, inhibit the supply of oxygen to organs and tissues.

MPCv for arsenic is 0.05 mg/dm3 (the limiting indicator of harmfulness is sanitary-toxicological) and MPCv is 0.05 mg/dm3.

The presence of nickel in natural waters is due to the composition of the rocks through which water passes: it is found in places of deposits of sulfide copper-nickel ores and iron-nickel ores. It enters the water from soils and from plant and animal organisms during their decay. An increased content of nickel compared to other types of algae was found in blue-green algae. Nickel compounds also enter water bodies with wastewater from nickel plating shops, synthetic rubber plants, and nickel enrichment plants. Huge nickel emissions accompany the burning of fossil fuels.

Its concentration can decrease as a result of the precipitation of compounds such as cyanides, sulfides, carbonates or hydroxides (with increasing pH values), due to its consumption by aquatic organisms and adsorption processes.

In surface waters, nickel compounds are in dissolved, suspended, and colloidal states, the quantitative ratio between which depends on the water composition, temperature, and pH values. Sorbents of nickel compounds can be iron hydroxide, organic substances, highly dispersed calcium carbonate, clays. Dissolved forms are mainly complex ions, most often with amino acids, humic and fulvic acids, and also in the form of a strong cyanide complex. Nickel compounds are the most common in natural waters, in which it is in the +2 oxidation state. Ni3+ compounds are usually formed in an alkaline medium.

Nickel compounds play an important role in hematopoietic processes, being catalysts. Its increased content has a specific effect on the cardiovascular system. Nickel is one of the carcinogenic elements. It can cause respiratory diseases. It is believed that free nickel ions (Ni2+) are about 2 times more toxic than its complex compounds.

In unpolluted and slightly polluted river waters, the nickel concentration usually ranges from 0.8 to 10 μg/dm3; in polluted it is several tens of micrograms per 1 dm3. The average concentration of nickel in sea water is 2 µg/dm3, in groundwater - n.103 µg/dm3. In underground waters washing nickel-containing rocks, nickel concentration sometimes increases up to 20 mg/dm3.

Nickel enters the atmosphere from non-ferrous metallurgy enterprises, which account for 97% of all nickel emissions, of which 89% come from enterprises of the Norilsk Nickel concern located in Zapolyarny and Nikel, Monchegorsk and Norilsk.

The increased content of nickel in the environment leads to the appearance of endemic diseases, bronchial cancer. Nickel compounds belong to the 1st group of carcinogens.
The map shows several points with high average concentrations of nickel in the locations of the Norilsk Nickel concern: Apatity, Kandalaksha, Monchegorsk, Olenegorsk.

Nickel emissions from industrial enterprises decreased by 28%, average concentrations - by 35%.

Emissions М (thousand tons/year) and average annual concentrations q (µg/m3) of nickel.

It enters natural waters as a result of leaching of tin-containing minerals (cassiterite, stannin), as well as with wastewater from various industries (fabric dyeing, synthesis of organic dyes, production of alloys with the addition of tin, etc.).

The toxic effect of tin is small.

Tin is found in unpolluted surface waters in submicrogram concentrations. In groundwater, its concentration reaches a few micrograms per 1 dm3. MPCv is 2 mg/dm3.

Mercury compounds can enter surface waters as a result of leaching of rocks in the area of ​​mercury deposits (cinnabar, metacinnabarite, livingstone), in the process of decomposition of aquatic organisms that accumulate mercury. Significant amounts enter water bodies with wastewater from enterprises producing dyes, pesticides, pharmaceuticals, and some explosives. Coal-fired thermal power plants emit significant amounts of mercury compounds into the atmosphere, which, as a result of wet and dry fallout, enter water bodies.

The decrease in the concentration of dissolved mercury compounds occurs as a result of their extraction by many marine and freshwater organisms, which have the ability to accumulate it in concentrations many times higher than its content in water, as well as adsorption processes by suspended solids and bottom sediments.

In surface waters, mercury compounds are in dissolved and suspended state. The ratio between them depends on the chemical composition of water and pH values. Suspended mercury is sorbed mercury compounds. Dissolved forms are undissociated molecules, complex organic and mineral compounds. In the water of water bodies, mercury can be in the form of methylmercury compounds.

Mercury compounds are highly toxic, they affect the human nervous system, cause changes in the mucous membrane, impaired motor function and secretion of the gastrointestinal tract, changes in the blood, etc. Bacterial methylation processes are aimed at the formation of methylmercury compounds, which are many times more toxic than mineral salts mercury. Methylmercury compounds accumulate in fish and can enter the human body.

MPCv of mercury is 0.0005 mg/dm3 (the limiting sign of harmfulness is sanitary-toxicological), MPCv is 0.0001 mg/dm3.

Natural sources of lead in surface waters are the processes of dissolution of endogenous (galena) and exogenous (anglesite, cerussite, etc.) minerals. A significant increase in the content of lead in the environment (including in surface waters) is associated with the combustion of coal, the use of tetraethyl lead as an antiknock agent in motor fuel, with the removal into water bodies with wastewater from ore processing plants, some metallurgical plants, chemical industries, mines, etc. Significant factors in lowering the concentration of lead in water are its adsorption by suspended solids and sedimentation with them into bottom sediments. Among other metals, lead is extracted and accumulated by hydrobionts.

Lead is found in natural waters in a dissolved and suspended (sorbed) state. In dissolved form, it occurs in the form of mineral and organomineral complexes, as well as simple ions, in insoluble form - mainly in the form of sulfides, sulfates and carbonates.

In river waters, the lead concentration ranges from tenths to units of micrograms per 1 dm3. Even in the water of water bodies adjacent to areas of polymetallic ores, its concentration rarely reaches tens of milligrams per 1 dm3. Only in chloride thermal waters the concentration of lead sometimes reaches several milligrams per 1 dm3.

The limiting indicator of harmfulness of lead is sanitary-toxicological. MPCv of lead is 0.03 mg/dm3, MPCv is 0.1 mg/dm3.

Lead is contained in emissions from metallurgy, metalworking, electrical engineering, petrochemistry and motor transport enterprises.

The impact of lead on health occurs through the inhalation of air containing lead, and the intake of lead with food, water, and dust particles. Lead accumulates in the body, in bones and surface tissues. Lead affects the kidneys, liver, nervous system and blood-forming organs. The elderly and children are especially sensitive to even low doses of lead.

Emissions M (thousand tons/year) and average annual concentrations q (µg/m3) of lead.

In seven years, lead emissions from industrial sources have decreased by 60% due to production cuts and the closure of many enterprises. The sharp decline in industrial emissions is not accompanied by a decrease in vehicle emissions. Average lead concentrations decreased by only 41%. The difference in abatement rates and lead concentrations can be explained by the underestimation of vehicle emissions in previous years; Currently, the number of cars and the intensity of their movement has increased.

Tetraethyl lead

It enters natural waters due to the use as an antiknock agent in the motor fuel of water vehicles, as well as with surface runoff from urban areas.

This substance is characterized by high toxicity, has cumulative properties.

The sources of silver entering surface waters are groundwater and wastewater from mines, processing plants, and photographic enterprises. The increased content of silver is associated with the use of bactericidal and algicidal preparations.

In wastewater, silver can be present in dissolved and suspended form, mostly in the form of halide salts.

In unpolluted surface waters, silver is found in submicrogram concentrations. In groundwater, the concentration of silver varies from a few to tens of micrograms per 1 dm3, in sea water, on average, 0.3 μg/dm3.

Silver ions are capable of destroying bacteria and sterilize water even in small concentrations (the lower limit of the bactericidal action of silver ions is 2.10-11 mol/dm3). The role of silver in the body of animals and humans has not been studied enough.

MPCv of silver is 0.05 mg/dm3.

Antimony enters surface waters through the leaching of antimony minerals (stibnite, senarmontite, valentinite, servingite, stibiocanite) and with wastewater from rubber, glass, dyeing, and match enterprises.

In natural waters, antimony compounds are in a dissolved and suspended state. Under the redox conditions characteristic of surface waters, both trivalent and pentavalent antimony can exist.

In unpolluted surface waters, antimony is found in submicrogram concentrations, in sea water its concentration reaches 0.5 µg/dm3, in groundwater - 10 µg/dm3. MPCv of antimony is 0.05 mg/dm3 (the limiting indicator of harmfulness is sanitary-toxicological), MPCv is 0.01 mg/dm3.

Tri- and hexavalent chromium compounds enter surface waters as a result of leaching from rocks (chromite, crocoite, uvarovite, etc.). Some quantities come from the decomposition of organisms and plants, from soils. Significant quantities can enter water bodies with wastewater from electroplating shops, dyeing shops of textile enterprises, tanneries and chemical industries. A decrease in the concentration of chromium ions can be observed as a result of their consumption by aquatic organisms and adsorption processes.

In surface waters, chromium compounds are in dissolved and suspended states, the ratio between which depends on the composition of the water, temperature, and pH of the solution. Suspended chromium compounds are mainly sorbed chromium compounds. Sorbents can be clays, iron hydroxide, highly dispersed settling calcium carbonate, plant and animal residues. In dissolved form, chromium can be in the form of chromates and bichromates. Under aerobic conditions, Cr(VI) transforms into Cr(III), whose salts in neutral and alkaline media are hydrolyzed with the release of hydroxide.

In unpolluted and slightly polluted river waters, the chromium content ranges from several tenths of a microgram per liter to several micrograms per liter, in polluted water bodies it reaches several tens and hundreds of micrograms per liter. The average concentration in sea waters is 0.05 µg/dm3, in groundwater - usually within n.10 - n.102 µg/dm3.

Cr(VI) and Cr(III) compounds in increased amounts have carcinogenic properties. Cr(VI) compounds are more dangerous.

It enters natural waters as a result of natural processes of destruction and dissolution of rocks and minerals (sphalerite, zincite, goslarite, smithsonite, calamine), as well as with wastewater from ore processing plants and electroplating shops, production of parchment paper, mineral paints, viscose fiber and others

In water, it exists mainly in ionic form or in the form of its mineral and organic complexes. Sometimes it occurs in insoluble forms: in the form of hydroxide, carbonate, sulfide, etc.

In river waters, the concentration of zinc usually ranges from 3 to 120 µg/dm3, in marine waters - from 1.5 to 10 µg/dm3. The content in ore and especially in mine waters with low pH values ​​can be significant.

Zinc is one of the active trace elements that affect the growth and normal development of organisms. At the same time, many zinc compounds are toxic, primarily its sulfate and chloride.

MPCv Zn2+ is 1 mg/dm3 (limiting indicator of harmfulness - organoleptic), MPCvr Zn2+ - 0.01 mg/dm3 (limiting sign of harmfulness - toxicological).

Heavy metals are already in second place in terms of danger, yielding to pesticides and well ahead of such well-known pollutants as carbon dioxide and sulfur, but in the forecast they should become the most dangerous, more dangerous than nuclear power plant waste and solid waste. Pollution with heavy metals is associated with their widespread use in industrial production, coupled with poor purification systems, as a result of which heavy metals enter the environment, including the soil, polluting and poisoning it.

Heavy metals are among the priority pollutants, monitoring of which is mandatory in all environments. In various scientific and applied works, the authors interpret the meaning of the concept of "heavy metals" in different ways. In some cases, the definition of heavy metals includes elements that are brittle (for example, bismuth) or metalloids (for example, arsenic).

Soil is the main medium into which heavy metals enter, including from the atmosphere and the aquatic environment. It also serves as a source of secondary pollution of surface air and waters that enter the World Ocean from it. Heavy metals are assimilated from the soil by plants, which then get into the food of more highly organized animals.
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--PAGE_BREAK-- 3.3. lead intoxication
Currently, lead occupies the first place among the causes of industrial poisoning. This is due to its wide application in various industries. Lead ore workers are exposed to lead in lead smelters, in the production of batteries, in soldering, in printing houses, in the manufacture of crystal glass or ceramic products, leaded gasoline, lead paints, etc. Lead pollution of atmospheric air, soil and water in the vicinity of such industries, as well as near major highways, creates a threat of lead exposure to the population living in these areas, and, above all, children, who are more sensitive to the effects of heavy metals.
It should be noted with regret that in Russia there is no state policy on the legal, regulatory and economic regulation of the impact of lead on the environment and public health, on reducing emissions (discharges, wastes) of lead and its compounds into the environment, and on the complete cessation of the production of lead-containing gasoline.

Due to the extremely unsatisfactory educational work to explain to the population the degree of danger of heavy metal exposure to the human body, in Russia the number of contingents with occupational contact with lead is not decreasing, but is gradually increasing. Cases of chronic lead intoxication have been recorded in 14 industries in Russia. The leading industries are the electrical industry (production of batteries), instrumentation, printing and non-ferrous metallurgy, in which intoxication is caused by an excess of the maximum permissible concentration (MAC) of lead in the air of the working area by 20 or more times.

A significant source of lead is automotive exhaust, as half of Russia still uses leaded gasoline. However, metallurgical plants, in particular copper smelters, remain the main source of environmental pollution. And there are leaders here. On the territory of the Sverdlovsk region there are 3 largest sources of lead emissions in the country: in the cities of Krasnouralsk, Kirovograd and Revda.

The chimneys of the Krasnouralsk copper smelter, built back in the years of Stalinist industrialization and using equipment from 1932, annually spewing 150-170 tons of lead into the city of 34,000, covering everything with lead dust.

The concentration of lead in the soil of Krasnouralsk varies from 42.9 to 790.8 mg/kg with the maximum allowable concentration MPC = 130 microns/kg. Water samples in the water supply of the neighboring village. Oktyabrsky, fed by an underground water source, recorded an excess of MPC up to two times.

Lead pollution has an impact on human health. Lead exposure disrupts the female and male reproductive systems. For women of pregnant and childbearing age, elevated levels of lead in the blood pose a particular danger, since lead disrupts menstrual function, more often there are premature births, miscarriages and fetal death due to the penetration of lead through the placental barrier. Newborns have a high mortality rate.

Lead poisoning is extremely dangerous for young children - it affects the development of the brain and nervous system. Testing of 165 Krasnouralsk children from 4 years of age revealed a significant mental retardation in 75.7%, and 6.8% of the children examined were found to have mental retardation, including mental retardation.

Preschool children are most susceptible to the harmful effects of lead because their nervous systems are still in the developmental stage. Even at low doses, lead poisoning causes a decrease in intellectual development, attention and concentration, a lag in reading, leads to the development of aggressiveness, hyperactivity and other behavioral problems in the child. These developmental abnormalities can be long-term and irreversible. Low birth weight, stunting, and hearing loss are also the result of lead poisoning. High doses of intoxication lead to mental retardation, coma, convulsions and death.

A white paper published by Russian specialists reports that lead pollution covers the entire country and is one of the many environmental disasters in the former Soviet Union that have come to light in recent years. Most of the territory of Russia is experiencing a load from lead fallout that exceeds the critical value for the normal functioning of the ecosystem. In dozens of cities, there is an excess of lead concentrations in the air and soil above the values ​​corresponding to the MPC.

The highest level of air pollution with lead, exceeding the MPC, was observed in the cities of Komsomolsk-on-Amur, Tobolsk, Tyumen, Karabash, Vladimir, Vladivostok.

The maximum loads of lead deposition leading to the degradation of terrestrial ecosystems are observed in the Moscow, Vladimir, Nizhny Novgorod, Ryazan, Tula, Rostov and Leningrad regions.

Stationary sources are responsible for the discharge of more than 50 tons of lead in the form of various compounds into water bodies. At the same time, 7 battery factories dump 35 tons of lead annually through the sewer system. An analysis of the distribution of lead discharges into water bodies on the territory of Russia shows that Leningrad, Yaroslavl, Perm, Samara, Penza and Oryol regions are leaders in this type of load.

The country needs urgent measures to reduce lead pollution, but so far Russia's economic crisis overshadows environmental problems. In a prolonged industrial depression, Russia lacks the funds to clean up past pollution, but if the economy starts to recover and factories return to work, pollution could only get worse.
10 most polluted cities of the former USSR

(Metals are listed in descending order of priority level for a given city)

4. Soil hygiene. Waste disposal.
The soil in cities and other settlements and their environs has long been different from the natural, biologically valuable soil, which plays an important role in maintaining the ecological balance. The soil in cities is subject to the same harmful effects as the urban air and hydrosphere, so its significant degradation occurs everywhere. Soil hygiene is not given sufficient attention, although its importance as one of the main components of the biosphere (air, water, soil) and a biological environmental factor is even more significant than water, since the amount of the latter (primarily the quality of groundwater) is determined by the state of the soil, and it is impossible to separate these factors from each other. The soil has the ability of biological self-purification: in the soil there is a splitting of the waste that has fallen into it and their mineralization; in the end, the soil compensates for the lost minerals at their expense.

If, as a result of soil overload, any of the components of its mineralizing capacity is lost, this will inevitably lead to a violation of the self-purification mechanism and to complete degradation of the soil. And, on the contrary, the creation of optimal conditions for self-purification of the soil contributes to the preservation of the ecological balance and conditions for the existence of all living organisms, including humans.

Therefore, the problem of neutralizing waste that has a harmful biological effect is not limited to the issue of their export; it is a more complex hygienic problem, since the soil is the link between water, air and man.
4.1.
The role of soil in metabolism

The biological relationship between soil and man is carried out mainly through metabolism. The soil is, as it were, a supplier of minerals necessary for the metabolic cycle, for the growth of plants consumed by humans and herbivores, eaten in turn by humans and carnivores. Thus, the soil provides food for many representatives of the plant and animal world.

Consequently, the deterioration of soil quality, the decrease in its biological value, its ability to self-cleanse causes a biological chain reaction, which, in the event of prolonged harmful effects, can lead to a variety of health disorders among the population. Moreover, if mineralization processes slow down, nitrates, nitrogen, phosphorus, potassium, etc., formed during the decay of substances, can enter groundwater used for drinking purposes and cause serious diseases (for example, nitrates can cause methemoglobinemia, primarily in infant).

Consumption of water from soil poor in iodine can cause endemic goiter, etc.
4.2.
Ecological relationship between soil and water and liquid waste (wastewater)

A person extracts from the soil the water necessary to maintain metabolic processes and life itself. The quality of water depends on the condition of the soil; it always reflects the biological state of a given soil.

This applies in particular to groundwater, the biological value of which is essentially determined by the properties of soils and soil, the ability of the latter to self-purify, its filtration capacity, the composition of its macroflora, microfauna, etc.

The direct influence of the soil on surface water is already less significant, it is associated mainly with precipitation. For example, after heavy rains, various pollutants are washed out of the soil into open water bodies (rivers, lakes), including artificial fertilizers (nitrogen, phosphate), pesticides, herbicides; in areas of karst, fractured deposits, pollutants can penetrate through cracks into deep The groundwater.

Inadequate wastewater treatment can also cause harmful biological effects on the soil and eventually lead to soil degradation. Therefore, soil protection in settlements is one of the main requirements for environmental protection in general.
4.3.
Soil load limits for solid waste (household and street waste, industrial waste, dry sludge from sewage sedimentation, radioactive substances, etc.)

The problem is exacerbated by the fact that, as a result of the generation of more and more solid waste in cities, the soil in their vicinity is subjected to increasing pressure. Soil properties and composition are deteriorating at an ever faster rate.

Of the 64.3 million tons of paper produced in the USA, 49.1 million tons end up in waste (out of this amount, 26 million tons are supplied by the household, and 23.1 million tons by the trading network).

In connection with the foregoing, the removal and final disposal of solid waste is a very significant, more difficult to implement hygienic problem in the context of increasing urbanization.

Final disposal of solid waste in contaminated soil is possible. However, due to the constantly deteriorating self-cleaning capacity of urban soil, the final disposal of waste buried in the ground is impossible.

A person could successfully use the biochemical processes occurring in the soil, its neutralizing and disinfecting ability to neutralize solid waste, but urban soil, as a result of centuries of human habitation and activities in cities, has long become unsuitable for this purpose.

The mechanisms of self-purification, mineralization occurring in the soil, the role of the bacteria and enzymes involved in them, as well as the intermediate and final products of the decomposition of substances are well known. Currently, research is aimed at identifying the factors that ensure the biological balance of the natural soil, as well as clarifying the question of how much solid waste (and what composition) can lead to a violation of the biological balance of the soil.
The amount of household waste (garbage) per inhabitant of some large cities of the world

It should be noted that the hygienic condition of the soil in cities as a result of its overload is rapidly deteriorating, although the ability of the soil to self-purify is the main hygienic requirement for maintaining biological balance. The soil in the cities is no longer able to cope with its task without the help of man. The only way out of this situation is the complete neutralization and destruction of waste in accordance with hygienic requirements.

Therefore, the construction of public utilities should be aimed at preserving the natural ability of the soil to self-purify, and if this ability has already become unsatisfactory, then it must be restored artificially.

The most unfavorable is the toxic effect of industrial waste, both liquid and solid. An increasing amount of such waste is getting into the soil, which it is not able to cope with. So, for example, soil contamination with arsenic was found in the vicinity of superphosphate production plants (within a radius of 3 km). As is known, some pesticides, such as organochlorine compounds that have entered the soil, do not decompose for a long time.

The situation is similar with some synthetic packaging materials (polyvinyl chloride, polyethylene, etc.).

Some toxic compounds sooner or later enter groundwater, as a result of which not only the biological balance of the soil is disturbed, but the quality of groundwater also deteriorates to such an extent that it can no longer be used as drinking water.
Percentage of the amount of basic synthetic materials contained in household waste (garbage)

*
Together with waste of other plastics that harden under the action of heat.
The problem of waste has increased today also because part of the waste, mainly human and animal feces, is used to fertilize agricultural land [feces contain a significant amount of nitrogen-0.4-0.5%, phosphorus (P203)-0.2-0 .6%, potassium (K? 0) -0.5-1.5%, carbon-5-15%]. This problem of the city has spread to the city's neighborhoods.
4.4.
The role of soil in the spread of various diseases

Soil plays a role in the spread of infectious diseases. This was reported back in the last century by Petterkoffer (1882) and Fodor (1875), who mainly highlighted the role of soil in the spread of intestinal diseases: cholera, typhoid, dysentery, etc. They also drew attention to the fact that some bacteria and viruses remain viable and virulent in the soil for months. Subsequently, a number of authors confirmed their observations, especially in relation to urban soil. For example, the causative agent of cholera remains viable and pathogenic in groundwater from 20 to 200 days, the causative agent of typhoid fever in feces - from 30 to 100 days, the causative agent of paratyphoid - from 30 to 60 days. (In terms of the spread of infectious diseases, urban soil is much more dangerous than field soil fertilized with manure.)

To determine the degree of soil contamination, a number of authors use the determination of the bacterial number (E. coli), as in determining the quality of water. Other authors consider it expedient to determine, in addition, the number of thermophilic bacteria involved in the process of mineralization.

The spread of infectious diseases through the soil is greatly facilitated by watering the land with sewage. At the same time, the mineralization properties of the soil also deteriorate. Therefore, watering with wastewater should be carried out under constant strict sanitary supervision and only outside the urban area.

4.5.
Harmful effect of the main types of pollutants (solid and liquid waste) leading to soil degradation

4.5.1.
Neutralization of liquid waste in the soil

In a number of settlements that do not have sewage systems, some waste, including manure, is neutralized in the soil.

As you know, this is the easiest way to neutralize. However, it is admissible only if we are dealing with a biologically valuable soil that has retained the ability to self-purify, which is not typical for urban soils. If the soil no longer possesses these qualities, then in order to protect it from further degradation, there is a need for complex technical facilities for the neutralization of liquid waste.

In a number of places, waste is neutralized in compost pits. Technically, this solution is a difficult task. In addition, liquids are able to penetrate the soil over fairly long distances. The task is further complicated by the fact that urban wastewater contains an increasing amount of toxic industrial waste that worsens the mineralization properties of the soil to an even greater extent than human and animal feces. Therefore, it is permissible to drain into compost pits only wastewater that has previously undergone sedimentation. Otherwise, the filtration capacity of the soil is disturbed, then the soil loses its other protective properties, the pores gradually become blocked, etc.

The use of human feces to irrigate agricultural fields is the second way to neutralize liquid waste. This method presents a double hygienic danger: firstly, it can lead to soil overload; secondly, this waste can become a serious source of infection. Therefore, feces must first be disinfected and subjected to appropriate treatment, and only then used as a fertilizer. There are two opposing points of view here. According to hygienic requirements, faeces are subject to almost complete destruction, and from the point of view of the national economy, they represent a valuable fertilizer. Fresh faeces cannot be used for watering gardens and fields without first disinfecting them. If you still have to use fresh feces, then they require such a degree of neutralization that they are almost of no value as a fertilizer.

Feces can be used as fertilizer only in specially designated areas - with constant sanitary and hygienic control, especially for the state of groundwater, the number of flies, etc.

The requirements for the disposal and disposal of animal faeces in the soil do not differ in principle from those for the disposal of human faeces.

Until recently, manure has been a significant source of valuable nutrients for agriculture to improve soil fertility. However, in recent years, manure has lost its importance, partly due to the mechanization of agriculture, partly due to the increasing use of artificial fertilizers.

In the absence of appropriate treatment and disposal, manure is also dangerous, as well as untreated human feces. Therefore, before being taken to the fields, manure is allowed to mature so that during this time (at a temperature of 60-70 ° C) the necessary biothermal processes can occur in it. After that, the manure is considered "mature" and freed from most of the pathogens contained in it (bacteria, worm eggs, etc.).

It must be remembered that manure stores can provide ideal breeding grounds for flies that promote the spread of various intestinal infections. It should be noted that flies for reproduction most readily choose pig manure, then horse, sheep and, last but not least, cow manure. Before exporting manure to the fields, it must be treated with insecticidal agents.
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Chapter 1. HEAVY METALS: BIOLOGICAL ROLE,

Heavy metals- this is a group of chemical elements with a relative atomic mass of more than 40. The appearance in the literature of the term "heavy metals" was associated with the manifestation of the toxicity of certain metals and their danger to living organisms. However, the “heavy” group also includes some microelements, the vital necessity and a wide range of biological effects of which have been irrefutably proven (Alekseev, 1987; Mineev, 1988; Krasnokutskaya et al., 1990; Saet et al., 1990; Ilyin, 1991; Cadmium: ecological…, 1994; Heavy…, 1997; Pronina, 2000).

Differences in terminology are mainly related to the concentration of metals in the natural environment. On the one hand, the concentration of the metal can be excessive and even toxic, then this metal is called "heavy", on the other hand, at a normal concentration or deficiency, it is referred to as trace elements. Thus, the terms microelements and heavy metals are most likely qualitative rather than quantitative categories, and are tied to extreme variants of the ecological situation (Alekseev, 1987; Ilyin, 1991; Maistrenko et al., 1996; Ilyin, Syso, 2001).

The functions of a living organism are inseparably linked with the chemistry of the earth's crust and should be studied in close connection with the latter (Vinogradov, 1957; Vernadsky, 1960; Avtsyn et al., 1991; Dobrovolsky, 1997). According to A.P. Vinogradova (1957), the quantitative content of an element in the body is determined by its content in the external environment, as well as the properties of the element itself, taking into account the solubility of its compounds. For the first time, the scientific foundations of the doctrine of microelements in our country were substantiated by V. I. Vernadsky (1960). Basic research was carried out by A.P. Vinogradov (1957), the founder of the theory of biogeochemical provinces and their role in the occurrence of endemic diseases in humans and animals, and V.V. Kovalsky (1974), the founder of geochemical ecology and biogeography of chemical elements, who was the first to carry out the biogeochemical zoning of the USSR.

Currently, out of 92 naturally occurring elements, 81 are found in the human body. At the same time, 15 of them (Fe, I, Cu, Zn, Co, Cr, Mo, Ni, V, Se, Mn, As, F, Si, Li) are recognized as vital. However, they can have a negative effect on plants, animals and humans if the concentration of their available forms exceeds certain limits. Cd , Pb , Sn and Rb are considered conditionally necessary, because they are apparently not very important for plants and animals and dangerous for human health even at relatively low concentrations (Dobrovolsky, 1980; Reutse and Kyrstya, 1986; Yagodin et al., 1989; Avtsyn et al., 1991; Davydova, 1991; Vronsky, 1996; Panin, 2000; Pronina, 2000).

For a long time, biogeochemical studies of microelements have been dominated by interest in geochemical anomalies and the resulting endemias of natural origin. However, in subsequent years, due to the rapid development of industry and global technogenic pollution of the environment, the anomalies of elements, mostly HMs, of industrial origin began to attract the most attention. Already now in many regions of the world the environment becomes more and more chemically "aggressive". In recent decades, the territories of industrial cities and adjacent lands have become the main objects of biogeochemical research (Geochemistry ..., 1986; Lepneva, 1987; Ilyin et al., 1988, 1997; Kabala, Singh, 2001; Kathryn and etc., 2002), especially if agricultural plants are grown on them and then used as food (Rautse, Kyrstya, 1986; Ilyin, 1985, 1987; Kabata-Pendias, Pendias, 1989; Chernykh, 1996, etc.).

The influence of trace elements on the vital activity of animals and humans is also being actively studied for medical purposes. It has now been found that many diseases, syndromes and pathological conditions are caused by a deficiency, excess or imbalance of microelements in a living organism and are collectively called “microelementoses” (Avtsyn et al., 1991).

In our studies, metals were studied from the standpoint of their toxic effects on living organisms caused by anthropogenic environmental pollution, so we used the term "heavy metals" for the studied elements.

1.1. Biological role and toxicological effect of heavy metals

In recent years, the important biological role of most metals has been increasingly confirmed. Numerous studies have established that the influence of metals is very diverse and depends on the content in the environment and the degree of need for them by microorganisms, plants, animals and humans.

The phytotoxic effect of HMs manifests itself, as a rule, at a high level of technogenic contamination of soils by them and largely depends on the properties and behavior of a particular metal. However, in nature, metal ions rarely occur in isolation from each other. Therefore, various combinative combinations and concentrations of different metals in the environment lead to changes in the properties of individual elements as a result of their synergistic or antagonistic effects on living organisms. For example, a mixture of zinc and copper is five times more toxic than the arithmetically calculated sum of their toxicity, which is due to the synergism in the combined effect of these elements. A mixture of zinc and nickel works in a similar way. However, there are sets of metals whose combined action manifests itself additively. A striking example of this is zinc and cadmium, which exhibit mutual physiological antagonism (Khimiya…, 1985). Manifestations of synergism and antagonism of metals are also evident in their multicomponent mixtures. Therefore, the total toxicological effect of HM pollution depends not only on the set and content of specific elements, but also on the characteristics of their mutual impact on biota.

Thus, the effect of heavy metals on living organisms is very diverse. This is due, firstly, to the chemical characteristics of metals, secondly, to the attitude of organisms towards them, and, thirdly, to environmental conditions. Below, according to the data available in the literature (Chemistry ..., 1985; Kenneth, Falchuk, 1993; Cadmium: ecological ..., 1994; Strawn, Sparks, 2000 and others), we give a brief description of the effect of HMs on living organisms.

Lead. The biological role of lead has been studied very poorly, but there are data in the literature (Avtsyn et al., 1991) confirming that the metal is vital for animal organisms, for example, rats. Animals lack this element when its concentration in the feed is less than 0.05-0.5 mg/kg (Ilyin, 1985; Kalnitsky, 1985). Plants also need it in small amounts. Lead deficiency in plants is possible when its content in the aerial part is from 2 to 6 µg/kg of dry matter (Kalnitsky, 1985; Kabata-Pendias, Pendias, 1989).

Increased interest in lead is due to its priority position among the main environmental pollutants (Kovalsky, 1974; Saet, 1987; Report ..., 1997; Snakin, 1998; Makarov, 2002). The metal is toxic to microorganisms, plants, animals and humans.

An excess of lead in plants, associated with its high concentration in the soil, inhibits respiration and suppresses the process of photosynthesis, sometimes leading to an increase in the content of cadmium and a decrease in the intake of zinc, calcium, phosphorus, and sulfur. As a result, the yield of plants decreases and the quality of the products is sharply deteriorating. External symptoms of the negative effects of lead are the appearance of dark green leaves, twisting of old leaves, and stunted foliage. The resistance of plants to its excess is not the same: cereals are less resistant, legumes are more resistant. Therefore, symptoms of toxicity in different crops may occur at different total lead content in the soil - from 100 to 500 mg/kg (Kabata-Pendias, Pendias, 1989; Ilyin, Syso, 2001). The metal concentration is above 10 mg/kg dry. in-va is toxic to most cultivated plants (Rautse, Kyrstya, 1986).

Lead enters the human body mainly through the digestive tract. At toxic doses, the element accumulates in the kidneys, liver, spleen and bone tissues. With lead toxicosis, the hematopoietic organs (anemia), the nervous system (encephalopathy and neuropathy) and the kidneys (nephropathy) are primarily affected. The hematopoietic system is most susceptible to lead, especially in children.

Cadmiumis well known as a toxic element, but it also belongs to the group of "new" microelements (cadmium, vanadium, silicon, tin, fluorine) and, in low concentrations, can stimulate their growth in some animals (Avtsyn et al., 1991). For higher plants, the value of cadmium has not been reliably established.

The main problems associated with mankind with this element are due to technogenic pollution of the environment and its toxicity to living organisms already at low concentrations (Ilyin, Syso, 2001).

The toxicity of cadmium to plants is manifested in the disruption of enzyme activity, inhibition of photosynthesis, disruption of transpiration, and inhibition of the reduction of N O 2 to N O. In addition, in plant metabolism, it is an antagonist of a number of nutrients (Zn, Cu, Mn, Ni, Se, Ca, Mg, P). Under the toxic effect of the metal in plants, growth retardation, damage to the root system and leaf chlorosis are observed. Cadmium quite easily enters from the soil and atmosphere into plants. In terms of phytotoxicity and ability to accumulate in plants in the HM series, it ranks first (Cd > Cu > Zn > Pb) (Ovcharenko et al., 1998).

Cadmium is capable of accumulating in the body of humans and animals, tk. relatively easily absorbed from food and water and penetrates into various organs and tissues. The toxic effect of the metal is manifested even at very low concentrations. Its excess inhibits the synthesis of DNA, proteins and nucleic acids, affects the activity of enzymes, disrupts the absorption and metabolism of other trace elements (Zn, Cu, Se, Fe), which can cause their deficiency.

Cadmium metabolism in the body is characterized by the following main features (Avtsyn et al., 1991): lack of an effective homeostatic control mechanism; long-term retention (cumulation) in the body with a very long half-life (average 25 years); predominant accumulation in the liver and kidneys; intensive interaction with other divalent metals both in the process of absorption and at the tissue level.

Chronic human exposure to cadmium results in impaired renal function, lung failure, osteomalacia, anemia, and loss of smell. There is evidence of a possible carcinogenic effect of cadmium and its possible involvement in the development of cardiovascular diseases. The most severe form of chronic cadmium poisoning is itai-itai disease, which is characterized by skeletal deformity with a noticeable decrease in growth, lumbar pain, painful phenomena in the muscles of the legs, and a duck's gait. In addition, there are frequent fractures of softened bones even when coughing, as well as dysfunction of the pancreas, changes in the gastrointestinal tract, hypochromic anemia, kidney dysfunction, etc. (Avtsyn et al., 1991).

Zinc. Of particular interest to zinc is associated with the discovery of its role in nucleic acid metabolism, transcription processes, stabilization of nucleic acids, proteins, and especially components of biological membranes (Peive, 1961), as well as in the metabolism of vitamin A. It plays an important role in the synthesis of nucleic acids and protein. Zinc is present in all 20 nucleotidyltransferases, and its discovery in reverse transcriptases made it possible to establish a close relationship with the processes of carcinogenesis. The element is necessary to stabilize the structure of DNA, RNA, ribosomes, plays an important role in the translation process and is indispensable at many key stages of gene expression. Zinc has been found in more than 200 enzymes belonging to all six classes, including hydrolases, transferases, oxidoreductases, lyases, ligases, and isomerases (Avtsyn et al., 1991). The uniqueness of zinc lies in the fact that no element is included in the composition of such a number of enzymes and does not perform such a variety of physiological functions (Kashin, 1999).

Elevated concentrations of zinc have a toxic effect on living organisms. In humans, they cause nausea, vomiting, respiratory failure, pulmonary fibrosis, and is a carcinogen (Kenneth and Falchuk, 1993). An excess of zinc in plants occurs in areas of industrial soil pollution, as well as with improper use of zinc-containing fertilizers. Most plant species have a high tolerance to its excess in soils. However, at very high levels of this metal in soils, chlorosis of young leaves is a common symptom of zinc toxicosis. With its excessive intake into plants and the resulting antagonism with other elements, the absorption of copper and iron decreases and symptoms of their deficiency appear.

In animals and humans, zinc affects cell division and respiration, skeletal development, brain formation and behavioral reflexes, wound healing, reproductive function, immune response, and interacts with insulin. With a deficiency of the element, a number of skin diseases occur. The toxicity of zinc for animals and humans is low, because. with excess intake, it is not cumulated, but is excreted. However, there are separate reports in the literature about the toxic effect of this metal: in animals, the increase in live weight decreases, depression in behavior appears, and abortions are possible (Kalnitsky, 1985). In general, the greatest problem for plants, animals and humans in most cases is the deficiency of zinc, rather than its toxic amounts.

Copper- is one of the most important irreplaceable elements necessary for living organisms. In plants, it is actively involved in the processes of photosynthesis, respiration, restoration and nitrogen fixation. Copper is part of a number of oxidase enzymes - cytochrome oxidase, ceruloplasmin, superoxide dismutase, urate oxidase, and others (Shkolnik, 1974; Avtsyn et al., 1991) and participates in biochemical processes as an integral part of enzymes that carry out reactions of substrate oxidation with molecular oxygen. Data on the toxicity of the element to plants are scarce. Currently, the main problem is the lack of copper in soils or its imbalance with cobalt. The main signs of copper deficiency for plants are a slowdown and then cessation of the formation of reproductive organs, the appearance of puny grain, empty-grained ears, and a decrease in resistance to adverse environmental factors. Wheat, oats, barley, alfalfa, table beet, onion and sunflower are most sensitive to its deficiency (Ilyin, Syso 2001; Adriano , 1986).

In the body of an adult, half of the total amount of copper is found in muscles and bones, and 10% in the liver. The main processes of absorption of this element occur in the stomach and small intestine. Its assimilation and metabolism are closely related to the content of other macro- and microelements and organic compounds in food. There is a physiological antagonism of copper with molybdenum and sulfate sulfur, as well as manganese, zinc, lead, strontium, cadmium, calcium, silver. An excess of these elements, along with a low content of copper in feed and food products, can cause a significant deficiency of the latter in human and animal organisms, which in turn leads to anemia, reduced growth rate, loss of live weight, and in case of an acute shortage of metal (less than 2 -3 mg per day) may cause rheumatoid arthritis and endemic goiter. excessive The absorption of copper by a person leads to Wilson's disease, in which an excess of the element is deposited in the brain tissue, skin, liver, pancreas and myocardium.

Nickel.The biological role of nickel is participation in the structural organization and functioning of the main cellular components - DNA, RNA and protein. Along with this, it is also present in the hormonal regulation of the body. According to its biochemical properties, nickel is very similar to iron and cobalt. Metal deficiency in ruminant farm animals is manifested in a decrease in enzyme activity and the possibility of death.

So far, there are no data on nickel deficiency for plants in the literature, however, a number of experiments have established a positive effect of nickel introduction into soils on crop yields, which may be due to the fact that it stimulates the microbiological processes of nitrification and mineralization of nitrogen compounds in soils. (Kashin, 1998; Ilyin, Syso, 2001; Brown, Wilch, 1987). Nickel toxicity to plants is manifested in the suppression of photosynthesis and transpiration processes, the appearance of signs of leaf chlorosis. For animal organisms, the toxic effect of the element is accompanied by a decrease in the activity of a number of metalloenzymes, a violation of protein, RNA and DNA synthesis, and the development of pronounced damage in many organs and tissues. The embryotoxicity of nickel has been experimentally established (Strochkova et al., 1987; Yagodin et al., 1991). Excessive intake of metal into the body of animals and humans can be associated with intense technogenic pollution of soils and plants with this element.

Chromium. Chromium is one of the elements vital to animal organisms. Its main functions are interaction with insulin in the processes of carbohydrate metabolism, participation in the structure and function of nucleic acids and, probably, the thyroid gland (Avtsyn et al., 1991). Plant organisms react positively to the introduction of chromium at a low content of the available form in the soil, however, the question of the element's indispensability for plant organisms continues to be studied.

The toxic effect of a metal depends on its valency: a hexavalent cation is much more toxic than a trivalent one. Symptoms of chromium toxicity are externally manifested in a decrease in the rate of growth and development of plants, withering of the aerial parts, damage to the root system and chlorosis of young leaves. An excess of metal in plants leads to a sharp decrease in the concentrations of many physiologically important elements, primarily K, P, Fe, Mn, Cu, B. In humans and animals, Cr 6+ has a general toxicological, nephrotoxic and hepatotoxic effect. Chromium toxicity is expressed in a change in the immunological reaction of the body, a decrease in reparative processes in cells, enzyme inhibition, liver damage, and a violation of biological oxidation processes, in particular the tricarboxylic acid cycle. In addition, an excess of metal causes specific skin lesions (dermatitis, ulcers), manifestations of the nasal mucosa, pneumosclerosis, gastritis, stomach and duodenal ulcers, chromic hepatosis, dysregulation of vascular tone and cardiac activity. Compounds Cr 6+ , along with a general toxicological effect, are capable of causing mutagenic and carcinogenic effects. Chromium, in addition to lung tissue, accumulates in the liver, kidneys, spleen, bones, and bone marrow (Krasnokutskaya et al., 1990).

The effect of HM toxic concentrations on plants is shown in Table 1.1, and on human and animal health in Table 1.2.

Table 1.1

Effects of toxic concentrations of some heavy metals on plants

Element	Concentration in soil, mg/kg	Plant response to elevated HM concentrations
	100-500	Inhibition of respiration and suppression of the process of photosynthesis, sometimes an increase in the content of cadmium and a decrease in the intake of zinc, calcium, phosphorus, sulfur, a decrease in yield, a deterioration in the quality of crop products. External symptoms - the appearance of dark green leaves, twisting of old leaves, stunted foliage
	1-13	Violation of enzyme activity, processes of transpiration and CO 2 fixation, inhibition of photosynthesis, inhibition of biological recovery N O 2 to N Oh, the difficulty in the intake and metabolism of a number of nutrients in plants. External symptoms - growth retardation, damage to the root system, leaf chlorosis.
	140-250	Chlorosis of young leaves
	200-500	Deterioration of plant growth and development, wilting of the aerial parts, damage to the root system, chlorosis of young leaves, a sharp decrease in the content of most essential macro- and microelements in plants (K, P, Fe, Mn, Cu, B, etc.).
	30-100*	Suppression of the processes of photosynthesis and transpiration, the appearance of signs of chlorosis

Note: * - mobile form, according to: Reutse, Kyrstya, 1986; Kabata-Pendias, Pendias, 1989; Yagodin et al., 1989;. Ilyin, Syso, 2002

Table 1.2

Impact of environmental pollution with heavy metals

on human and animal health

Element	Characteristic diseases at high concentrations of HM in the body
	An increase in mortality from cardiovascular diseases, an increase in general morbidity, changes in the lungs of children, damage to the hematopoietic organs, nervous and cardiovascular systems, liver, kidneys, disorders in the course of pregnancy, childbirth, the menstrual cycle, stillbirth, congenital deformities. Inhibition of the activity of many enzymes, violation of metabolic processes.
	Kidney dysfunction, inhibition of the synthesis of DNA, proteins and nucleic acids, decreased enzyme activity, slowing down the intake and metabolism of other microelements ( Zn, Cu, Se, Fe ), which can cause their deficiency in the body.
	Changes in the morphological composition of the blood, malignant tumors, radiation sickness; in animals - a decrease in live weight gain, depression in behavior, the possibility of abortion.
	Increasing mortality from respiratory cancer.
	Changes in the body's immunological response, reduced reparative processes in cells, enzyme inhibition, liver damage.
	Violation of the synthesis of protein, RNA and DNA, the development of severe damage in many organs and tissues.

According to: Methodical ..., 1982; Kalnitsky, 1985; Avtsyn et al., 1991; Pokatilov, 1993; Makarov, 2002

1.2. Heavy metals in soils

The content of HM in soils depends, as established by many researchers, on the composition of the original rocks, a significant variety of which is associated with a complex geological history of the development of territories (Kovda, 1973). depends on the conditions of hypergene transformation.

In recent decades, human anthropogenic activity has been intensively involved in the processes of HM migration in the natural environment. The amounts of chemical elements entering the environment as a result of technogenesis, in some cases, significantly exceed the level of their natural intake. For example, global selection Pb from natural sources per year is 12 thousand tons. and anthropogenic emissions of 332 thousand tons. ( Nriagu , 1989). Involved in natural migration cycles, anthropogenic flows lead to the rapid spread of pollutants in the natural components of the urban landscape, where their interaction with humans is inevitable. The volumes of pollutants containing HM increase annually and cause damage to the natural environment, undermine the existing ecological balance and adversely affect human health.

The main sources of anthropogenic release of HM into the environment are thermal power plants, metallurgical enterprises, quarries and mines for the extraction of polymetallic ores, transport, chemical means of protecting crops from diseases and pests, burning oil and various wastes, production of glass, fertilizers, cement, etc. The most powerful HM halos appear around ferrous and especially non-ferrous metallurgy enterprises as a result of atmospheric emissions (Kovalsky, 1974; Dobrovolsky, 1983; Israel, 1984; Geochemistry ..., 1986; Saet, 1987; Panin, 2000; Kabala, Singh, 2001). The effect of pollutants extends to tens of kilometers from the source of elements entering the atmosphere. Thus, metals in an amount of 10 to 30% of the total emissions into the atmosphere spread over a distance of 10 km or more from an industrial enterprise. At the same time, combined pollution of plants is observed, which consists of the direct settling of aerosols and dust on the surface of leaves and the root assimilation of HMs accumulated in the soil over a long period of pollution from the atmosphere (Ilyin, Syso, 2001).

According to the data below, one can judge the size of anthropogenic activity of mankind: the contribution of technogenic lead is 94-97% (the rest is natural sources), cadmium - 84-89%, copper - 56-87%, nickel - 66-75%, mercury - 58% etc. At the same time, 26-44% of the world anthropogenic flow of these elements falls on Europe, and the share of the European territory of the former USSR is 28-42% of all emissions in Europe (Vronsky, 1996). The level of technogenic fallout of HMs from the atmosphere in different regions of the world is not the same (Table 1.3) and depends on the presence of developed deposits, the degree of development of the mining and processing and industrial industries, transport, urbanization of territories, etc.

Table 1.3

Fallout of heavy metals from the atmosphere onto the underlying surface

regions of the world, thousand tons/year (Israel et al., 1989, cited by Vronsky, 1996)

Region	Lead	Cadmium	Mercury
Europe		1,59
		1,78	10,6
Asia		2,58
Asian part b. the USSR	21,4	0,88	20,9
North America		7,36	17,8
Central and South America			24,9
Africa			28,4
Australia		0,22
Arctic		0,87	19,4
Antarctica	0,38	0,016

The study of the share participation of various industries in the global flow of HM emissions shows: 73% of copper and 55% of cadmium are associated with emissions from copper and nickel production enterprises; 54% of mercury emissions come from coal combustion; 46% of nickel - for burning oil products; 86% of lead enters the atmosphere from vehicles (Vronsky, 1996). Agriculture also supplies a certain amount of HM to the environment, where pesticides and mineral fertilizers are used, in particular, superphosphates contain significant amounts of chromium, cadmium, cobalt, copper, nickel, vanadium, zinc, etc.

Elements emitted into the atmosphere through the pipes of chemical, heavy and nuclear industries have a noticeable effect on the environment. The share of thermal and other power plants in atmospheric pollution is 27%, ferrous metallurgy enterprises - 24.3%, enterprises for the extraction and manufacture of building materials - 8.1% (Alekseev, 1987; Ilyin, 1991). HMs (with the exception of mercury) are mainly introduced into the atmosphere as aerosols. The set of metals and their content in aerosols are determined by the specialization of industrial and energy activities. When coal, oil, and shale are burned, the elements contained in these fuels enter the atmosphere along with smoke. So, coal contains cerium, chromium, lead, mercury, silver, tin, titanium, as well as uranium, radium and other metals.

The most significant environmental pollution is caused by powerful thermal stations (Maistrenko et al., 1996). Every year, burning coal alone releases 8,700 times more mercury into the atmosphere than can be included in the natural biogeochemical cycle, 60 times more uranium, 40 times more cadmium, 10 times more yttrium and zirconium, and 3-4 times more tin. 90% of cadmium, mercury, tin, titanium and zinc polluting the atmosphere gets into it when coal is burned. This largely affects the Republic of Buryatia, where energy companies using coal are the largest air pollutants. Among them (according to their contribution to total emissions), Gusinoozerskaya GRES (30%) and CHPP-1 of Ulan-Ude (10%) stand out.

Significant pollution of atmospheric air and soil occurs due to transport. Most HMs contained in dust and gas emissions from industrial enterprises are, as a rule, more soluble than natural compounds (Bol'shakov et al., 1993). Large industrialized cities stand out among the most active sources of HMs. Metals accumulate relatively quickly in the soils of cities and are extremely slowly removed from them: the half-life of zinc is up to 500 years, cadmium is up to 1100 years, copper is up to 1500 years, and lead is up to several thousand years (Maistrenko et al., 1996). In many cities of the world, high rates of HM pollution have led to the disruption of the main agroecological functions of soils (Orlov et al., 1991; Kasimov et al., 1995). Cultivation of agricultural plants used for food near these territories is potentially dangerous, since crops accumulate excessive amounts of HMs that can lead to various diseases in humans and animals.

According to a number of authors (Ilyin and Stepanova, 1979; Zyrin, 1985; Gorbatov and Zyrin, 1987, etc.), it is more correct to assess the degree of soil contamination with HMs by the content of their most bioavailable mobile forms. However, maximum allowable concentrations (MPCs) of mobile forms of most HMs have not yet been developed. Therefore, the literature data on the level of their content, leading to adverse environmental consequences, can serve as a criterion for comparison.

Below is a brief description of the properties of metals, concerning the features of their behavior in soils.

Lead (Pb). Atomic mass 207.2. The primary element is a toxicant. All soluble lead compounds are poisonous. Under natural conditions, it exists mainly in the form of PbS. Clark Pb in the earth's crust 16.0 mg/kg (Vinogradov, 1957). Compared to other HMs, it is the least mobile, and the degree of mobility of the element is greatly reduced when soils are limed. Mobile Pb is present in the form of complexes with organic matter (60–80% of mobile Pb). At high pH values, lead is chemically fixed in the soil in the form of hydroxide, phosphate, carbonate, and Pb-organic complexes (Zinc and cadmium…, 1992; Heavy…, 1997).

The natural content of lead in soils is inherited from parent rocks and is closely related to their mineralogical and chemical composition (Beus et al., 1976; Kabata-Pendias, Pendias, 1989). The average concentration of this element in the soils of the world reaches, according to various estimates, from 10 (Saet et al., 1990) to 35 mg/kg (Bowen, 1979). The MPC of lead for soils in Russia corresponds to 30 mg/kg (Instructive ..., 1990), in Germany - 100 mg/kg (Kloke, 1980).

The high concentration of lead in soils can be associated with both natural geochemical anomalies and anthropogenic impact. With technogenic pollution, the highest concentration of the element, as a rule, is found in the upper soil layer. In some industrial areas, it reaches 1000 mg/kg (Dobrovolsky, 1983), and in the surface layer of soils around non-ferrous metallurgy enterprises in Western Europe, it reaches 545 mg/kg (Rautse and Kyrstya, 1986).

The content of lead in soils in Russia varies significantly depending on the type of soil, the proximity of industrial enterprises and natural geochemical anomalies. In the soils of residential areas, especially those associated with the production of lead-containing products, the content of this element is often tens or more times higher than the MPC (Table 1.4). According to preliminary estimates, up to 28% of the country's territory has a Pb content in the soil, on average, below the background, and 11% can be attributed to the risk zone. At the same time, in the Russian Federation the problem of soil pollution with lead is predominantly a problem of residential areas (Snakin et al., 1998).

Cadmium (Cd). Atomic mass 112.4. Cadmium is similar in chemical properties to zinc, but differs from it in greater mobility in acidic environments and better availability for plants. In the soil solution, the metal is present in the form of Cd 2+ and forms complex ions and organic chelates. The main factor determining the content of the element in soils in the absence of anthropogenic influence is the parent rocks (Vinogradov, 1962; Mineev et al., 1981; Dobrovolsky, 1983; Ilyin, 1991; Zinc and cadmium ..., 1992; Cadmium: ecological ..., 1994) . Clark of cadmium in the lithosphere 0.13 mg/kg (Kabata-Pendias, Pendias, 1989). In soil-forming rocks, the average metal content is: in clays and clay shales - 0.15 mg / kg, loess and loess-like loams - 0.08, sands and sandy loams - 0.03 mg / kg (Zinc and cadmium ..., 1992). In the Quaternary deposits of Western Siberia, the concentration of cadmium varies within 0.01-0.08 mg/kg.

The mobility of cadmium in soil depends on the environment and redox potential (Heavy…, 1997).

The average content of cadmium in the soils of the world is 0.5 mg/kg (Saet et al., 1990). Its concentration in the soil cover of the European part of Russia is 0.14 mg/kg in soddy-podzolic soil, 0.24 mg/kg in chernozem (Zinc and cadmium ..., 1992), 0.07 mg/kg in the main types soils of Western Siberia (Ilyin, 1991). The approximate allowable content (AEC) of cadmium for sandy and sandy loamy soils in Russia is 0.5 mg/kg, in Germany the MPC of cadmium is 3 mg/kg (Kloke, 1980).

Cadmium contamination of the soil cover is considered one of the most dangerous environmental phenomena, since it accumulates in plants above the norm even with slight soil contamination (Kadmiy …, 1994; Ovcharenko, 1998). The highest concentrations of cadmium in the upper soil layer are observed in mining areas - up to 469 mg/kg (Kabata-Pendias, Pendias, 1989), around zinc smelters they reach 1700 mg/kg (Rautse, Kyrstya, 1986).

Zinc (Zn). Atomic mass 65.4. Its clarke in the earth's crust is 83 mg/kg. Zinc is concentrated in clay deposits and shales in amounts from 80 to 120 mg/kg (Kabata-Pendias, Pendias, 1989), in deluvial, loess-like and carbonate loamy deposits of the Urals, in loams of Western Siberia - from 60 to 80 mg/kg.

Important factors influencing the mobility of Zn in soils are the content of clay minerals and the pH value. With an increase in pH, the element passes into organic complexes and is bound by the soil. Zinc ions also lose their mobility, getting into the interpacket spaces of the montmorillonite crystal lattice. With organic matter, Zn forms stable forms; therefore, in most cases, it accumulates in soil horizons with a high content of humus and in peat.

The reasons for the increased content of zinc in soils can be both natural geochemical anomalies and technogenic pollution. The main anthropogenic sources of its receipt are primarily non-ferrous metallurgy enterprises. Soil contamination with this metal in some areas has led to its extremely high accumulation in the upper soil layer - up to 66400 mg/kg. In garden soils, up to 250 or more mg/kg of zinc accumulates (Kabata-Pendias, Pendias, 1989). The AEC of zinc for sandy and sandy loamy soils is 55 mg/kg; German scientists recommend an MPC of 100 mg/kg (Kloke, 1980).

Copper (Cu). Atomic mass 63.5. Clark in the earth's crust 47 mg/kg (Vinogradov, 1962). Chemically, copper is an inactive metal. The fundamental factor influencing the Cu content is its concentration in soil-forming rocks (Goryunova et al., 2001). Of the igneous rocks, the largest amount of the element is accumulated by the main rocks - basalts (100-140 mg/kg) and andesites (20-30 mg/kg). Covering and loess-like loams (20-40 mg/kg) are less rich in copper. Its lowest content is noted in sandstones, limestones and granites (5-15 mg/kg) (Kovalsky, Andriyanova, 1970; Kabata-Pendias, Pendias, 1989). The concentration of metal in clays of the European part of the territory of the former USSR reaches 25 mg/kg (Malgin, 1978; Kovda, 1989), in loess-like loams it reaches 18 mg/kg (Kovda, 1989). Sandy and sandy soil-forming rocks of the Altai Mountains accumulate an average of 31 mg/kg of copper (Malgin, 1978), in the south of Western Siberia - 19 mg/kg (Ilyin, 1973).

In soils, copper is a weakly migratory element, although the content of the mobile form is quite high. The amount of mobile copper depends on many factors: the chemical and mineralogical composition of the parent rock, the pH of the soil solution, the content of organic matter, etc. (Vinogradov, 1957; Peive, 1961; Kovalsky and Andriyanova, 1970; Alekseev, 1987, etc.). The largest amount of copper in the soil is associated with oxides of iron, manganese, iron and aluminum hydroxides, and, especially, with montmorillonite vermiculite. Humic and fulvic acids are able to form stable complexes with copper. At pH 7-8, the solubility of copper is the lowest.

The average content of copper in the soils of the world is 30 mg/kg ( Bowen , 1979). Near industrial sources of pollution, in some cases, soil contamination with copper up to 3500 mg/kg can be observed (Kabata-Pendias, Pendias, 1989). The average metal content in the soils of the central and southern regions of the former USSR is 4.5-10.0 mg/kg, in the south of Western Siberia - 30.6 mg/kg (Ilyin, 1973), in Siberia and the Far East - 27.8 mg/kg ( Makeev, 1973). MPC for copper in Russia is 55 mg/kg (Instructive ..., 1990), APC for sandy and sandy loamy soils is 33 mg/kg (Control ..., 1998), in Germany - 100 mg/kg ( Kloke, 1980).

Nickel (Ni). Atomic mass 58.7. In continental sediments, it is present mainly in the form of sulfides and arsenites, and is also associated with carbonates, phosphates, and silicates. The clarke of an element in the earth's crust is 58 mg/kg (Vinogradov, 1957). Ultrabasic (1400-2000 mg/kg) and basic (200-1000 mg/kg) rocks accumulate the greatest amount of metal, while sedimentary and acidic rocks contain it in much lower concentrations - 5-90 and 5-15 mg/kg, respectively (Reuce , Kyrstya, 1986; Kabata-Pendias and Pendias, 1989). Of great importance in the accumulation of nickel by soil-forming rocks is their granulometric composition. On the example of soil-forming rocks of Western Siberia, it can be seen that in lighter rocks its content is the lowest, in heavy rocks it is the highest: in sands - 17, sandy loams and light loams - 22, medium loams - 36, heavy loams and clays - 46 (Ilyin, 2002) .

The content of nickel in soils largely depends on the availability of this element in soil-forming rocks (Kabata-Pendias, Pendias, 1989). The highest concentrations of nickel, as a rule, are observed in clayey and loamy soils, in soils formed on basic and volcanic rocks and rich in organic matter. The distribution of Ni in the soil profile is determined by the content of organic matter, amorphous oxides, and the amount of clay fraction.

The level of nickel concentration in the upper soil layer also depends on the degree of their technogenic pollution. In areas with a developed metalworking industry, very high accumulation of nickel occurs in soils: in Canada, its gross content reaches 206–26,000 mg/kg, and in Great Britain, the content of mobile forms reaches 506–600 mg/kg. In the soils of Great Britain, Holland, Germany, treated with sewage sludge, nickel accumulates up to 84–101 mg/kg (Kabata-Pendias, Pendias, 1989). In Russia (according to a survey of 40-60% of agricultural soils), 2.8% of the soil cover is contaminated with this element. The proportion of soils contaminated with Ni among other HMs (Pb, Cd, Zn, Cr, Co, As, etc.) is actually the most significant and is second only to soils contaminated with copper (3.8%) (Aristarkhov, Kharitonova, 2002). According to land monitoring data of the State Station of the Agrochemical Service "Buryatskaya" for 1993-1997. on the territory of the Republic of Buryatia, an excess of the MAC of nickel was registered by 1.4% of the land of the surveyed area of ​​agricultural land, among which the soils of Zakamensky (20% of the land are polluted - 46 thousand ha) and Khorinsky districts (11% of the land are polluted - 8 thousand ha).

Chrome (cr). Atomic mass 52. In natural compounds, chromium has a valence of +3 and +6. Most of Cr 3+ is present in chromite FeCr 2 O 4 or other minerals of the spinel series, where it replaces Fe and Al, to which it is very close in its geochemical properties and ionic radius.

Clark of chromium in the earth's crust - 83 mg / kg. Its highest concentrations among igneous rocks are typical for ultrabasic and basic (1600–3400 and 170–200 mg/kg, respectively), lower concentrations for medium rocks (15–50 mg/kg), and the lowest for acidic rocks (4–25 mg/kg). kg). Among sedimentary rocks, the maximum content of the element was found in clay sediments and shales (60-120 mg/kg), the minimum content was found in sandstones and limestones (5-40 mg/kg) (Kabata-Pendias, Pendias, 1989). The content of metal in soil-forming rocks of different regions is very diverse. In the European part of the former USSR, its content in the most common soil-forming rocks such as loess, loess-like carbonate and mantle loams averages 75-95 mg/kg (Yakushevskaya, 1973). The soil-forming rocks of Western Siberia contain an average of 58 mg/kg Cr, and its amount is closely related to the granulometric composition of the rocks: sandy and sandy loamy rocks - 16 mg/kg, and medium loamy and clayey rocks - about 60 mg/kg (Ilyin, Syso, 2001) .

In soils, most of the chromium is present in the form of Cr 3+ . In an acidic environment, the Cr 3+ ion is inert; at pH 5.5, it precipitates almost completely. The Cr 6+ ion is extremely unstable and is easily mobilized in both acidic and alkaline soils. The adsorption of chromium by clays depends on the pH of the medium: with an increase in pH, the adsorption of Cr 6+ decreases, and Cr 3+ increases. Soil organic matter stimulates the reduction of Cr 6+ to Cr 3+ .

The natural content of chromium in soils depends mainly on its concentration in soil-forming rocks (Kabata-Pendias and Pendias, 1989; Krasnokutskaya et al., 1990), while the distribution along the soil profile depends on the features of soil formation, in particular, on the granulometric composition of genetic horizons. The average content of chromium in soils is 70 mg/kg (Bowen, 1979). The highest content of the element is observed in soils formed on basic and volcanic rocks rich in this metal. The average content of Cr in the soils of the United States is 54 mg/kg, China is 150 mg/kg (Kabata-Pendias and Pendias, 1989), and Ukraine is 400 mg/kg (Bespamyatnov and Krotov, 1985). In Russia, its high concentrations in soils under natural conditions are due to the enrichment of soil-forming rocks. Kursk chernozems contain 83 mg/kg of chromium, soddy-podzolic soils of the Moscow region - 100 mg/kg. The soils of the Urals, formed on serpentinites, contain up to 10,000 mg/kg of metal, and 86–115 mg/kg in Western Siberia (Yakushevskaya, 1973; Krasnokutskaya et al., 1990; Ilyin and Syso, 2001).

The contribution of anthropogenic sources to the supply of chromium is very significant. Chromium metal is mainly used for chromium plating as a component of alloy steels. Soil pollution with Cr has been noted due to emissions from cement plants, iron-chromium slag dumps, oil refineries, ferrous and non-ferrous metallurgy enterprises, the use of industrial wastewater sludge in agriculture, especially tanneries, and mineral fertilizers. The highest concentrations of chromium in technogenically contaminated soils reach 400 mg/kg or more (Kabata-Pendias, Pendias, 1989), which is especially characteristic of large cities (Table 1.4). In Buryatia, according to land monitoring data conducted by the Buryatskaya State Agrochemical Service Station for 1993-1997, 22 thousand hectares are contaminated with chromium. Excesses of MPC by 1.6-1.8 times were noted in Dzhida (6.2 thousand ha), Zakamensky (17.0 thousand ha) and Tunkinsky (14.0 thousand ha) districts. MPC for chromium in soils in Russia has not yet been developed, and in Germany for soils of agricultural land it is 200-500, household plots - 100 mg / kg (Ilyin, Syso, 2001; Eikmann, Kloke, 1991).

1.3. Effect of heavy metals on microbial cenosis of soils

One of the most effective diagnostic indicators of soil pollution is its biological state, which can be assessed by the viability of the soil microorganisms inhabiting it (Babieva et al., 1980; Levin et al., 1989; Guzev, Levin, 1991; Kolesnikov, 1995; Zvyagintsev et al. ., 1997; Saeki etc. al., 2002).

It should also be taken into account that microorganisms play an important role in the migration of HMs in the soil. In the process of life, they act as producers, consumers and transport agents in the soil ecosystem. Many soil fungi exhibit the ability to immobilize HMs, fixing them in the mycelium and temporarily excluding them from the cycle. In addition, fungi, releasing organic acids, neutralize the effect of these elements, forming with them components that are less toxic and available to plants than free ions (Pronina, 2000; Zeolites, 2000).

Under the influence of elevated HM concentrations, there is a sharp decrease in the activity of enzymes: amylase, dehydrogenase, urease, invertase, catalase (Grigoryan, 1980; Panikova, Pertsovskaya, 1982), as well as the number of individual agronomically valuable groups of microorganisms (Bulavko, 1982; Babich, Stotzky, 1985 ). HMs inhibit the processes of mineralization and synthesis of various substances in soils (Naplekova, 1982; Evdokimova et al., 1984), suppress the respiration of soil microorganisms, cause a microbostatic effect (Skvortsova et al., 1980), and can act as a mutagenic factor (Kabata-Pendias, Pendias, 1989). Excessive content of HMs in the soil reduces the activity of metabolic processes, morphological transformations in the structure of reproductive organs, and other changes in soil biota occur. HMs can largely suppress biochemical activity and cause changes in the total number of soil microorganisms (Brookes and Mcgrant, 1984).

Soil contamination with HM causes certain changes in the species composition of the complex of soil microorganisms. As a general pattern, there is a significant reduction in the species richness and diversity of the complex of soil micromycetes due to pollution. In the microbial community of polluted soil, micromycete species resistant to HM appear unusual for normal conditions (Kobzev, 1980; Lagauskas et al., 1981; Evdokimova et al., 1984). Tolerance of microorganisms to soil pollution depends on their belonging to different systematic groups. Species of the genus Bacillus, nitrifying microorganisms, are very sensitive to high concentrations of HMs; pseudomonads, streptomycetes, and many types of cellulose-destroying microorganisms are somewhat more resistant; fungi and actinomycetes are the most resistant (Naplekova, 1982; Zeolites..., 2000).

At low HM concentrations, some stimulation of the development of the microbial community is observed, then, as the concentrations increase, partial inhibition occurs and, finally, its complete suppression. Significant changes in the species composition are recorded at HM concentrations 50–300 times higher than the background ones.

The degree of inhibition of the vital activity of microbiocenosis also depends on the physiological and biochemical properties of specific metals that pollute the soil. Lead has a negative effect on biotic activity in the soil, inhibiting the activity of enzymes by reducing the intensity of carbon dioxide release and the number of microorganisms, causing disturbances in the metabolism of microorganisms, especially the processes of respiration and cell division. Cadmium ions at a concentration of 12 mg/kg disrupt the fixation of atmospheric nitrogen, as well as the processes of ammonification, nitrification, and denitrification (Rautse and Kirstya, 1986). Mushrooms are the most exposed to cadmium, and some species completely disappear after the metal enters the soil (Kadmium: ecological ..., 1994). An excess of zinc in soils hinders the fermentation of cellulose decomposition, the respiration of microorganisms, the action of urease, etc., as a result of which the processes of transformation of organic matter in soils are disrupted. In addition, the toxic effect of HMs depends on the set of metals and their mutual effects (antagonistic, synergistic, or total) on the microbiota.

Thus, under the influence of soil pollution with HMs, changes occur in the complex of soil microorganisms. This is expressed in a decrease in species richness and diversity and an increase in the proportion of microorganisms tolerant to pollution. The intensity of soil self-purification from pollutants depends on the activity of soil processes and the vital activity of the microorganisms inhabiting it.

The level of soil contamination with HMs affects the biochemical activity of soils, the species structure, and the total number of microbial communities (Microorganisms…, 1989). In soils where the content of heavy metals exceeds the background by 2-5 times or more, individual indicators of enzymatic activity change most noticeably, the total biomass of the amylolytic microbial community increases slightly, and other microbiological indicators also change. With a further increase in the HM content to one order of magnitude, a significant decrease in individual indicators of the biochemical activity of soil microorganisms is found (Grigoryan, 1980; Panikova and Pertsovskaya, 1982). There is a redistribution of the dominance of the amylolytic microbial community in the soil. In the soil containing HMs in concentrations one or two orders of magnitude higher than the background ones, changes in a whole group of microbiological parameters are already significant. The number of species of soil micromycetes is reduced, and the most resistant species begin to absolutely dominate. When the HM content in the soil exceeds the background by three orders of magnitude, sharp changes are observed in almost all microbiological parameters. At the indicated concentrations of HMs in soils, inhibition and death of the microbiota normal for uncontaminated soil occurs. At the same time, a very limited number of microorganisms resistant to HM, mainly micromycetes, actively develops and even absolutely dominates. Finally, at HM concentrations in soils that exceed the background levels by four or more orders of magnitude, a catastrophic decrease in soil microbiological activity is found, bordering on the complete death of microorganisms.

1.4. Heavy metals in plants

Plant food is the main source of HM intake in humans and animals. According to various data (Panin, 2000; Ilyin, Syso, 2001), from 40 to 80% of HM comes with it, and only 20-40% - with air and water. Therefore, the health of the population largely depends on the level of accumulation of metals in plants used for food.

The chemical composition of plants, as is known, reflects the elemental composition of soils. Therefore, excessive accumulation of HMs by plants is primarily due to their high concentrations in soils. In their vital activity, plants come into contact only with available forms of HMs, the amount of which, in turn, is closely related to the buffering capacity of soils. However, the ability of soils to bind and inactivate HMs has its limits, and when they can no longer cope with the incoming flow of metals, the presence in the plants themselves of physiological and biochemical mechanisms that prevent their entry becomes important.

The mechanisms of plant resistance to HM excess can manifest themselves in different ways: some species are able to accumulate high HM concentrations, but show tolerance to them; others seek to reduce their intake by maximizing their barrier functions. For most plants, the first barrier level is the roots, where the greatest amount of HM is retained, the next one is the stems and leaves, and, finally, the last one is the organs and parts of plants responsible for reproductive functions (most often seeds and fruits, as well as root and tuber crops and etc.). (Garmash G.A. 1982; Ilyin, Stepanova, 1982; Garmash N.Yu., 1986; Alekseev, 1987; Heavy ..., 1987; Goryunova, 1995; Orlov et al., 1991 and others; Ilyin, Syso, 2001). The level of HM accumulation by different plants depending on their genetic and species characteristics with the same HM content in soils is clearly illustrated by the data presented in Table 1.5.

Table 1.5

technogenically polluted soil, mg/kg wet weight (household plot,

Belovo, Kemerovo region) (Ilyin, Syso, 2001)

Culture (plant organ)
tomato (fruit)
White cabbage (head)
Potato (tuber)
Carrot (root vegetable)
Beetroot (root vegetable)
DOK (Naystein et al., 1987)

Note: gross content in soil Zn is equal to 7130, P b - 434 mg / kg

However, these patterns do not always repeat, which is probably due to the growing conditions of plants and their genetic specificity. There are cases when different varieties of the same crop growing on the same contaminated soil contained different amounts of HM. This fact, apparently, is due to the intraspecific polymorphism inherent in all living organisms, which can also manifest itself in technogenic pollution of the natural environment. This property in plants can become the basis for genetic breeding studies in order to create varieties with increased protective capabilities in relation to excessive HM concentrations (Ilyin and Syso, 2001).

Despite the significant variability of various plants to the accumulation of HMs, the bioaccumulation of elements has a certain tendency, allowing them to be ordered into several groups: 1) Cd , Cs , Rb - elements of intense absorption; 2) Zn, Mo, Cu, Pb, As, Co - average degree of absorption; 3) Mn , Ni , Cr - weak absorption and 4) Se , Fe , Ba , Te - elements that are difficult for plants (Heavy ..., 1987; Cadmium ..., 1994; Pronina, 2000).

Another route of HM entry into plants is foliar absorption from air currents. It takes place with a significant precipitation of metals from the atmosphere onto the sheet apparatus, most often near large industrial enterprises. The entry of elements into plants through the leaves (or foliar absorption) occurs mainly through non-metabolic penetration through the cuticle. HM absorbed by leaves can be transferred to other organs and tissues and included in the metabolism. Metals deposited with dust emissions on leaves and stems do not pose a danger to humans if the plants are thoroughly washed before eating. However, animals eating such vegetation can receive large amounts of HMs.

As plants grow, the elements are redistributed throughout their organs. At the same time, for copper and zinc, the following regularity is established in their content: roots > grain > straw. For lead, cadmium, and strontium, it has a different form: roots > straw > grain (Heavy…, 1997). It is known that, along with the species specificity of plants with regard to the accumulation of HMs, there are certain general patterns. For example, the highest HM content was found in leafy vegetables and silage crops, while the lowest content was found in legumes, cereals, and industrial crops.

Thus, the considered material indicates a huge contribution to soil and plant pollution by HMs from large cities. Therefore, the problem of TM has become one of the "acute" problems of modern natural science. An earlier geochemical survey of soils in the city of Ulan-Ude (Belogolovov, 1989) makes it possible to estimate the total level of contamination of 0–5 cm of the soil cover layer with a wide range of chemical elements. However, the soils of horticultural cooperatives, household plots and other lands where food plants are grown by the population remain practically unexplored; those territories, the pollution of which may directly affect the health of the population of Ulan-Ude. There are absolutely no data on the content of mobile HM forms. Therefore, in our studies, we tried to dwell in more detail on the study of the current state of contamination of garden soils in Ulan-Ude with HMs, their most dangerous mobile forms for biota, and the features of the distribution and behavior of metals in the soil cover and profile of the main types of soils in Ulan-Ude .

Heavy metals are, perhaps, one of the most serious soil pollution, which threatens us with a host of undesirable and, moreover, harmful consequences.

By its nature, the soil is a combination of various clay minerals of organic and inorganic origin. Depending on the composition of the soil, geographic data, as well as remoteness from industrial areas, various types of heavy metals can be contained in the soil, each of which poses a particular degree of danger to the environment. Due to the fact that in different places the structure of the soil can also be different, the redox conditions, reactivity, as well as the mechanisms of binding heavy metals in the soil are also different.

The greatest danger to the soil is technogenic factors. Various industries, whose waste is heavy metal particles, unfortunately, are equipped in such a way that even the best filters pass elements of heavy metals, which first appear in the atmosphere, and then, together with industrial waste, penetrate the soil. This type of pollution is called man-made. In this case, the mechanical composition of the soil, the content of carbonates and the ability to absorb are of great importance. Heavy metals differ not only in the degree of impact on the soil, but also in the state in which they are in it.

At present, it is known that almost all particles of heavy metals can be found in the soil in the following states: as a mixture of isomorphic particles, oxidized, in the form of salt deposits, in a crystal lattice, in a soluble form, directly in the soil solution, and even be part of organic substances. At the same time, it should be taken into account that, depending on the redox conditions, the composition of the soil and the level of carbon dioxide content, the behavior of metal particles may change.

Heavy metals are terrible not only because of their presence in the soil composition, but because they are able to move, change and penetrate into plants, which can cause significant harm to the environment. The mobility of heavy metal particles can vary depending on whether there is a difference between the elements in the solid and liquid phases. Pollutants, in this case elements of heavy metals, can often take a firmly fixed form when penetrating into the soil layers. In this form, metals are not available to plants. In all other cases, metals easily penetrate plants.

Water-soluble metal elements penetrate the soil very quickly. Moreover, they do not just enter the soil layer, they are able to migrate through it. From school lessons, everyone knows that over time, low-molecular water-soluble mineral compounds are formed in the soil, which migrate to the lower part of the reservoir. And together with them, heavy metal compounds also migrate, forming low-molecular complexes, that is, transforming into another state.