Mobile forms of heavy metals in soil. Abstract: Heavy metals in the soil

Antimony

Present in some ores.

It is part of the alloys used in various industrial fields.

Its excess causes severe eating disorders.

Arsenic

The main source of soil contamination with arsenic are substances used to control pests of agricultural plants, such as herbicides, insecticides. Arsenic is a cumulative poison that causes chronic. Its compounds provoke diseases of the nervous system, brain, and skin.

Manganese

In the soil and plants, a high content of this element is observed.

If an additional amount of manganese enters the soil, a dangerous excess of it is quickly created. This affects the human body in the form of destruction of the nervous system.

An excess of other heavy elements is no less dangerous.

From the foregoing, we can conclude that the accumulation of heavy metals in the soil entails severe consequences for human health and the environment as a whole.

The main methods of combating soil pollution with heavy metals

Methods for dealing with soil contamination with heavy metals can be physical, chemical and biological. Among them are the following methods:

• An increase in soil acidity increases the possibility. Therefore, the introduction of organic matter and clay, liming help to some extent in the fight against pollution.
• Sowing, mowing and removing some plants, such as clover, from the soil surface significantly reduces the concentration of heavy metals in the soil. Besides this method is completely environmentally friendly.
• Underground water detoxification, its pumping and cleaning.
• Prediction and elimination of migration of soluble form of heavy metals.
• In some particularly severe cases, complete removal of the soil layer and its replacement with a new one is required.

The most dangerous of all these metals is lead. It has the property of accumulating to hit the human body. Mercury is not dangerous if it enters the human body once or several times, only mercury vapor is especially dangerous. I believe that industrial enterprises should use more advanced production technologies that are not so detrimental to all living things. Not one person should think, but a mass, then we will come to a good result.

Protecting the environment from pollution has become an urgent task of society. Heavy metals occupy a special place among the numerous pollutants. These conditionally include chemical elements with an atomic mass of more than 50, which have the properties of metals. Among the chemical elements, heavy metals are considered to be the most toxic.

Soil is the main medium into which heavy metals enter, including from the atmosphere and 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 dangerous because they have the ability to accumulate in living organisms, to be included in the metabolic cycle, to form highly toxic organometallic compounds, to change their form when moving from one natural environment to another, without being subjected to biological decomposition. Heavy metals cause serious physiological disorders in humans, toxicosis, allergies, oncological diseases, negatively affect the fetus and genetic heredity.

Among heavy metals, lead, cadmium, and zinc are considered priority pollutants, mainly because their technogenic accumulation in the environment is proceeding at a high rate. This group of substances has a high affinity for physiologically important organic compounds.

Soil pollution with mobile forms of heavy metals is the most urgent, since in recent years the problem of environmental pollution has assumed a threatening character. In the current situation, it is necessary not only to intensify research on all aspects of the problem of heavy metals in the biosphere, but also to periodically sum up the results in order to comprehend the results obtained in different, often weakly interconnected, branches of science.

The object of this study is the anthropogenic soils of the Zheleznodorozhny district of Ulyanovsk (on the example of Transportnaya street).

The main goal of the study is to determine the degree of contamination of urban soils with heavy metals.

The objectives of the study are: determination of the pH value in the selected soil samples; determination of the concentration of mobile forms of copper, zinc, cadmium, lead; analysis of the obtained data and proposal of recommendations to reduce the content of heavy metals in urban soils.

Samples in 2005 were taken along the highway along Transportnaya St., and in 2006 on the territory of personal household plots (along the same street) located near the railway tracks. Samples were taken to a depth of 0-5 cm and 5-10 cm. A total of 20 samples were taken, each weighing 500 g.

The investigated samples of samples of 2005 and 2006 belong to the neutral soil. Neutral soils absorb heavy metals from solutions to a greater extent than acidic ones. But there is a danger of an increase in the mobility of heavy metals and their penetration into groundwater and a nearby reservoir, when acid rain(the surveyed area is located in the floodplain of the Sviyagi River), which will immediately affect the food chains. In these samples, a low content of humus (2-4%) is observed. Accordingly, there is no soil ability to form organo-metallic complexes.

Based on laboratory studies of soils for the content of Cu, Cd, Zn, Pb, conclusions were drawn about their concentrations in the soils of the surveyed area. In the samples of 2005, an excess of the MPC of Cu by 1-1.2 times, Cd by 6-9 times was revealed, and the content of Zn and Pb did not exceed the MPC. In samples taken in 2006 for household plots the concentration of Cu did not exceed the MPC, the content of Cd is less than in the samples taken along the road, but still exceeds the MPC at different points from 0.3 to 4.6 times. The content of Zn is increased only at the 5th point and is 23.3 mg/kg of soil at a depth of 0-5 cm (MPC 23 mg/kg), and at a depth of 5-10 cm 24.8 mg/kg.

Based on the results of the study, the following conclusions were drawn: soils are characterized by a neutral reaction of the soil solution; soil samples have low humus content; on the territory of the Zheleznodorozhny district of Ulyanovsk, pollution of the soil with heavy metals of varying intensity is observed; found that in some samples a significant excess of MPC, especially observed in soil studies on the concentration of cadmium; to improve the ecological and geographical state of the soil in this area, it is recommended to grow heavy metal accumulator plants and manage the ecological properties of the soil itself through its artificial design; it is necessary to carry out systematic monitoring and identify the most polluted and hazardous areas for public health.

Bibliographic link

The total contamination of the soil characterizes the gross amount of heavy metal. The availability of elements for plants is determined by their mobile forms. Therefore, the content of mobile forms of heavy metals in the soil - the most important indicator, which characterizes the sanitary and hygienic situation and determines the need for reclamation detoxification measures.
Depending on the extractant used, different quantity mobile form of heavy metal, which with a certain convention can be considered available to plants. For the extraction of mobile forms of heavy metals, various chemical compounds are used that have unequal extractive powers: acids, salts, buffer solutions, and water. The most common extractants are 1N HCl and ammonium acetate buffer pH 4.8. At present, not enough experimental material has been accumulated to characterize the dependence of the content of heavy metals in plants, which are extracted by various chemical solutions, on their concentration in the soil. The complexity of this situation is also due to the fact that the availability of a mobile form of heavy metal for plants depends largely on the properties of the soil and the specific characteristics of plants. At the same time, the behavior of each element in the soil has its own specific patterns inherent in it.
To study the influence of soil properties on the transformation of heavy metal compounds, model experiments were carried out with soils with sharply different properties (Table 8). The extractants used were a strong acid, 1N HNO3, a neutral salt Ca(NO3)2, an ammonium acetate buffer solution, and water.

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 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 environments at background stations biosphere reserves, In chapter 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 organics; 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 sea ​​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 chemical composition 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 water bodies 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 sedimentation to the bottom. 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 later data is considered 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.

City

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. A decrease in the concentrations of molybdenum compounds occurs as a result of precipitation of sparingly soluble compounds, adsorption processes 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 xanthine oxidase enzyme. 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. AT 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. 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 of 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 dichromates. 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 weak 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 large highways poses a threat of lead exposure to the population living in these areas, and especially 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.

Children preschool age are most susceptible to the harmful effects of lead, as their nervous system is in the process of formation. Even at low doses, lead poisoning causes a decrease intellectual development, attention and ability to concentrate, lagging behind in reading, leads to the development of aggressiveness, hyperactivity and other problems in the child's behavior. 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 experts 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 the economic crisis in Russia overshadows ecological 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 pace.

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 for the disposal of solid waste biochemical processes occurring in the soil, its neutralizing and disinfecting ability, however, urban soil as a result of centuries of human habitation and activity 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 distribution 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 represents a significant great danger than the soil in the fields 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 degrades 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 mechanization. Agriculture, due in part 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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