CONTENTS
Introduction
1. Soil cover and its use
2. Soil erosion (water and wind) and methods of combating it
3. Industrial soil pollution
3.1 Acid rain
3.2 Heavy metals
3.3 Lead toxicity
4. Soil hygiene. Waste disposal
4.1 The role of soil in metabolism
4.2 Ecological relationships between soil and water and liquid waste (wastewater)
4.3 Limits of soil load with solid waste (household and street garbage, industrial waste, dry sludge after sewage sedimentation, radioactive substances)
4.4 The role of soil in the spread of various diseases
4.5 Harmful effects of the main types of pollutants (solid and liquid wastes) leading to soil degradation
4.5.1 Neutralization of liquid waste in soil
4.5.2.1 Neutralization of solid waste in soil
4.5.2.2 Garbage collection and removal
4.5.3 Final removal and rendering harmless
4.6 Disposal of radioactive waste
Conclusion
List of sources used
Introduction.
A certain part of the soil, both in Russia and throughout the world, leaves agricultural use every year for various reasons, discussed in detail in the UIR. Thousands or more hectares of land suffer from erosion, acid rain, improper cultivation and toxic waste. To avoid this, you need to become familiar with the most productive and inexpensive reclamation measures (For the definition of reclamation, see the main part of the work) that increase the fertility of the soil cover, and above all with the negative impact on the soil itself, and how to avoid it.
These studies provide insight into the harmful effects on soil and have been conducted through a number of books, articles and scientific journals dealing with soil issues and environmental protection.
The problem of soil pollution and degradation has always been relevant. Now we can add to what has been said that in our time the anthropogenic influence has a strong impact on nature and is only growing, and the soil is one of the main sources of food and clothing for us, not to mention the fact that we walk on it and will always be in close contact with her.
1. Soil cover and its use.
Soil cover is the most important natural formation. Its importance for the life of society is determined by the fact that soil is the main source of food, providing 97-98% of the food resources of the planet's population. At the same time, the soil cover is a place of human activity on which industrial and agricultural production is located.
Highlighting the special role of food in the life of society, V.I. Lenin pointed out: “The real foundations of the economy are the food fund.”
The most important property of the soil cover is its fertility, which is understood as the totality of soil properties that ensure the yield of agricultural crops. Natural soil fertility is regulated by reserve nutrients in the soil and its water, air and thermal regimes. The role of soil cover in the productivity of terrestrial ecological systems is great, since soil nourishes land plants with water and many compounds and is an essential component of the photosynthetic activity of plants. Soil fertility also depends on the amount of solar energy accumulated in it. Living organisms, plants and animals inhabiting the Earth record solar energy in the form of phyto- or zoomass. The productivity of terrestrial ecological systems depends on the thermal and water balance of the earth's surface, which determines the variety of forms of exchange of matter and matter within the geographic envelope of the planet.
Analyzing the importance of land for social production, K. Marx identified two concepts: earth-matter and earth-capital. The first of these should be understood the earth that arose in the process of its evolutionary development without the will and consciousness of people and is the place of human settlement and the source of his food. From the moment when land, in the process of development of human society, becomes a means of production, it appears in a new quality - capital, without which the labor process is unthinkable, “... because it gives the worker... a place on which he stands... , and its process - the scope of action...”. It is for this reason that the earth is a universal factor in any human activity.
The role and place of land are different in various spheres of material production, primarily in industry and agriculture. In the manufacturing industry, construction, and transport, the earth is the place where labor processes take place regardless of the natural fertility of the soil. Land plays a different role in agriculture. Under the influence of human labor, natural fertility turns from potential into economic. The specificity of the use of land resources in agriculture leads to the fact that they act in two different qualities, as an object of labor and as a means of production. K. Marx noted: “By the mere new investment of capital in plots of land... people increased land-capital without any increase in the matter of the earth, i.e., the space of the earth.”
Land in agriculture acts as a productive force due to its natural fertility, which does not remain constant. With rational use of land, such fertility can be increased by improving its water, air and thermal conditions through reclamation measures and increasing the content of nutrients in the soil. On the contrary, with irrational use of land resources, their fertility decreases, resulting in a decrease in agricultural yields. In some places, cultivation of crops becomes completely impossible, especially on saline and eroded soils.
At a low level of development of the productive forces of society, the expansion of food production occurs due to the involvement of new lands in agriculture, which corresponds to the extensive development of agriculture. This is facilitated by two conditions: the availability of free land and the possibility of farming at an affordable average level of capital costs per unit area. This use of land resources and farming is typical of many developing countries in the modern world.
During the era of scientific and technological revolution, there was a sharp distinction between the farming system in industrialized and developing countries. The former are characterized by the intensification of agriculture using the achievements of scientific and technological revolution, in which agriculture develops not due to an increase in the area of cultivated land, but due to an increase in the amount of capital invested in the land. The well-known limitation of land resources for most industrialized capitalist countries, the increasing demand for agricultural products throughout the world due to high rates of population growth, and a higher culture of agriculture contributed to the transfer of agriculture in these countries back to the 50s on the path of intensive development. The acceleration of the process of intensification of agriculture in industrialized capitalist countries is associated not only with the achievements of scientific and technological revolution, but mainly with the profitability of investing capital in agriculture, which concentrated agricultural production in the hands of large landowners and ruined small farmers.
Agriculture developed in other ways in developing countries. Among the acute natural resource problems of these countries, the following can be identified: low agricultural standards, which caused degradation of soils (increased erosion, salinization, decreased fertility) and natural vegetation (for example, tropical forests), depletion of water resources, desertification of lands, especially clearly manifested in African countries. continent. All these factors related to the socio-economic problems of developing countries have led to chronic food shortages in these countries. Thus, at the beginning of the 80s, in terms of provision per person with grain (222 kg) and meat (14 kg), developing countries were inferior to industrialized capitalist countries, respectively, several times. Solving the food problem in developing countries is unthinkable without major socio-economic transformations.
In our country, the basis of land relations is the national (national) ownership of land, which arose as a result of the nationalization of all land. Agrarian relations are built on the basis of plans according to which agriculture should develop in the future, with financial and credit assistance from the state and the supply of the required number of machines and fertilizers. Paying agricultural workers according to the quantity and quality of work stimulates a constant increase in their living standards.
The use of the land fund as a whole is carried out on the basis of long-term state plans. An example of such plans was the development of virgin and fallow lands in the east of the country (mid-50s), thanks to which it became possible to introduce more than 41 million hectares of new areas into arable land in a short period of time. Another example is a set of measures related to the implementation of the Food Program, which provides for accelerating the development of agricultural production based on improving farming standards, extensive land reclamation activities, as well as the implementation of a broad program of socio-economic reconstruction of agricultural areas.
The world's land resources as a whole make it possible to provide food for more people than is currently available and will be the case in the near future. At the same time, due to population growth, especially in developing countries, the amount of arable land per capita is decreasing.
heavy metal plant soil
The content of HMs in soils depends, as has been established by many researchers, on the composition of the original rocks, the significant diversity of which is associated with the complex geological history of the development of the territories (Kovda, 1973). The chemical composition of soil-forming rocks, represented by rock weathering products, is predetermined by the chemical composition of the original rocks and depends on the conditions of supergene transformation.
In recent decades, anthropogenic activities of mankind have been intensively involved in the processes of migration of heavy metals 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, the global release of Pb from natural sources per year is 12 thousand tons. and anthropogenic emissions 332 thousand tons. (Nriagu, 1989). Involving 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 volume of pollutants containing heavy metals increases every year and damages the natural environment, undermines the existing ecological balance and negatively affects human health.
The main sources of anthropogenic entry of heavy metals into the environment are thermal power plants, metallurgical enterprises, quarries and mines for the extraction of polymetallic ores, transport, chemicals protection of agricultural crops from diseases and pests, combustion of oil and various wastes, production of glass, fertilizers, cement, etc. The most powerful halos of HMs arise around ferrous and especially non-ferrous metallurgy enterprises as a result of atmospheric emissions (Kovalsky, 1974; Dobrovolsky, 1983; Israel, 1984; Geochemistry..., 1986; Sayet, 1987; Panin, 2000; Kabala, Singh, 2001). The effect of pollutants extends over tens of kilometers from the source of elements entering the atmosphere. Thus, metals in amounts from 10 to 30% of the total emissions into the atmosphere are distributed over a distance of 10 km or more from an industrial enterprise. In this case, combined pollution of plants is observed, consisting of the direct deposition of aerosols and dust on the surface of leaves and the root absorption of heavy metals accumulated in the soil over a long period of time of receipt of pollution from the atmosphere (Ilyin, Syso, 2001).
Based on the data below, one can judge the size of mankind’s anthropogenic activity: the contribution of technogenic lead is 94-97% (the rest is natural springs), cadmium - 84-89%, copper - 56-87%, nickel - 66-75%, mercury - 58%, etc. At the same time, 26-44% of the global anthropogenic flow of these elements falls on Europe, and the share of the European territory former USSR- 28-42% of all emissions in Europe (Vronsky, 1996). The level of technogenic fallout of heavy metals from the atmosphere in different regions of the world is not the same 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.
A study of the share 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 combustion of petroleum products; 86% of lead enters the atmosphere from vehicles (Vronsky, 1996). A certain amount of heavy metals is also supplied to the environment by agriculture, 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 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 production of building materials - 8.1% (Alekseev, 1987; Ilyin, 1991). HM (with the exception of mercury) are mainly introduced into the atmosphere as part of 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, elements contained in these types of fuel 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 power plants (Maistrenko et al., 1996). Every year, only when burning coal, mercury is released into the atmosphere 8700 times more than can be included in the natural biogeochemical cycle, uranium - 60 times, cadmium - 40 times, yttrium and zirconium - 10 times, tin - 3-4 times. 90% of cadmium, mercury, tin, titanium and zinc that pollute the atmosphere enter it when burning coal. This significantly affects the Republic of Buryatia, where energy enterprises using coal are the largest polluters of the atmosphere. Among them (in terms of contribution to total emissions) Gusinoozerskaya State District Power Plant (30%) and Thermal Power Plant-1 in Ulan-Ude (10%) stand out.
Visible soiling atmospheric air and soil occurs due to transport. Most heavy metals contained in dust and gas emissions industrial enterprises, as a rule, are more soluble than natural compounds (Bolshakov et al., 1993). Large industrialized cities stand out among the most active sources of heavy metals. Metals accumulate relatively quickly in urban soils and are removed extremely slowly from them: the half-life of zinc is up to 500 years, cadmium - up to 1100 years, copper - up to 1500 years, lead - up to several thousand years (Maistrenko et al., 1996). In many cities around the world, high rates of HM pollution have led to disruption of the basic agroecological functions of soils (Orlov et al., 1991; Kasimov et al., 1995). Growing agricultural plants used for food near these areas is potentially dangerous, since crops accumulate excess amounts of HMs, which can lead to various diseases in humans and animals.
According to a number of authors (Ilyin, Stepanova, 1979; Zyrin, 1985; Gorbatov, Zyrin, 1987, etc.), the degree of soil contamination with HMs is more correctly assessed by the content of their most bioavailable mobile forms. However, maximum permissible concentrations (MPC) of mobile forms of most heavy metals have not currently been developed. Therefore, literature data on the level of their content leading to adverse environmental consequences can serve as a criterion for comparison.
Below are short description properties of metals relating to the characteristics of their behavior in soils.
Lead (Pb). Atomic mass 207.2. The priority 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 is 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% mobile Pb). At high values pH lead is fixed in the soil chemically 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 and 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 maximum permissible concentration of lead for soils in Russia corresponds to 30 mg/kg (Instructive..., 1990), in Germany - 100 mg/kg (Kloke, 1980).
High concentrations of lead in soils can be associated with both natural geochemical anomalies and anthropogenic impact. In case of technogenic pollution, the highest concentration of the element is usually found in the top layer of soil. 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 - 545 mg/kg (Reutse, Kirstea, 1986).
The lead content in soils in Russia varies significantly depending on the type of soil, the proximity of industrial enterprises and natural geochemical anomalies. In soils of residential areas, especially those associated with the use and production of lead-containing products, the content of this element is often tens or more times higher than the maximum permissible concentration (Table 1.4). According to preliminary estimates, up to 28% of the country's territory has Pb content in the soil, on average, below the background level, and 11% can be classified as a risk zone. At the same time, in the Russian Federation the problem of soil contamination with lead is primarily a problem in residential areas (Snakin et al., 1998).
Cadmium (Cd). Atomic mass 112.4. Cadmium is close in chemical properties to zinc, but differs from it by greater mobility in acidic environments and better accessibility to plants. In the soil solution, the metal is present in the form of Cd2+ 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) . Clarke 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 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 Quaternary sediments of Western Siberia, the concentration of cadmium varies within the range of 0.01-0.08 mg/kg.
The mobility of cadmium in soil depends on the environment and redox potential (Heavy..., 1997).
The average cadmium content in world soils is 0.5 mg/kg (Sayet et al., 1990). Its concentration in the soil cover of the European part of Russia is 0.14 mg/kg - in sod-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 permissible content (ATC) of cadmium for sandy and sandy loam soils in Russia is 0.5 mg/kg, in Germany the MPC of cadmium is 3 mg/kg (Kloke, 1980).
Contamination of soil with cadmium is considered one of the most dangerous environmental phenomena, since it accumulates in plants above the norm even with weak soil contamination (Cadmium..., 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 (Reutse, Cirstea, 1986).
Zinc (Zn). Atomic mass 65.4. Its clarke in the earth's crust is 83 mg/kg. Zinc is concentrated in clayey sediments and shales in quantities from 80 to 120 mg/kg (Kabata-Pendias, Pendias, 1989), in colluvial, 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 pH. When the pH increases, the element passes into organic complexes and binds to the soil. Zinc ions also lose mobility, entering the interpacket spaces of the montmorillonite crystal lattice. Zn forms stable forms with organic matter, so in most cases it accumulates in soil horizons with a high humus content and in peat.
The reasons for the increased zinc content 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 has led in some areas to its extremely high accumulation in the upper soil layer - up to 66,400 mg/kg. In garden soils, up to 250 or more mg/kg of zinc accumulates (Kabata-Pendias and Pendias, 1989). The MPC of zinc for sandy and sandy loam soils is 55 mg/kg; German scientists recommend a MPC of 100 mg/kg (Kloke, 1980).
Copper (Cu). Atomic mass 63.5. Clark in the earth's crust is 47 mg/kg (Vinogradov, 1962). Chemically, copper is a low-active metal. The fundamental factor influencing the value of Cu content is its concentration in soil-forming rocks (Goryunova et al., 2001). Of the igneous rocks, the largest amount of the element accumulates in basic rocks - basalts (100-140 mg/kg) and andesites (20-30 mg/kg). Cover and loess-like loams (20-40 mg/kg) are less rich in copper. Its lowest content is observed in sandstones, limestones and granites (5-15 mg/kg) (Kovalsky, Andriyanova, 1970; Kabata-Pendias, Pendias, 1989). The metal concentration 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 - 18 mg/kg (Kovda, 1989). Sandy loam 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 can be 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, Andriyanova, 1970; Alekseev, 1987, etc.). The largest amount of copper in the soil is associated with oxides of iron, manganese, hydroxides of iron and aluminum, and, especially, with montmorillonite and vermiculite. Humic and fulvic acids are capable of forming stable complexes with copper. At pH 7-8, the solubility of copper is the lowest.
The average copper content in world soils 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 and 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, the south of Western Siberia - 30.6 mg/kg (Ilyin, 1973), Siberia and the Far East - 27.8 mg/kg (Makeev, 1973). The maximum permissible concentration of copper in Russia is 55 mg/kg (Instructive..., 1990), the maximum permissible concentration for sandy and sandy loam 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 the 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 largest amount of metal, while sedimentary and acidic rocks contain it in much lower concentrations - 5-90 and 5-15 mg/kg, respectively (Reutse , Cîrstea, 1986; Kabata-Pendias, Pendias, 1989). Great importance The granulometric composition of soil-forming rocks plays a role in the accumulation of nickel. Using the example of soil-forming rocks of Western Siberia, it is clear 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 nickel content in soils largely depends on the supply of this element to the soil-forming rocks (Kabata-Pendias and Pendias, 1989). The highest concentrations of nickel are usually 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 top layer of soil also depends on the degree of technogenic pollution. In areas with a developed metalworking industry, very high accumulation of nickel is found in soils: in Canada its gross content reaches 206-26000 mg/kg, and in Great Britain the content of mobile forms reaches 506-600 mg/kg. In 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 soils on agricultural land), 2.8% of the soil cover is contaminated with this element. The share 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 lands contaminated with copper (3.8%) (Aristarkhov, Kharitonova, 2002). According to land monitoring data from the State Station of Agrochemical Service “Buryatskaya” for 1993-1997. on the territory of the Republic of Buryatia, an excess of the maximum permissible concentration of nickel was registered on 1.4% of the lands from the surveyed agricultural area, among which the soils of the Zakamensky (20% of the land - 46 thousand hectares are contaminated) and Khorinsky districts (11% of the land - 8 thousand hectares are contaminated).
Chromium (Cr). Atomic mass 52. In natural compounds, chromium has a valency of +3 and +6. Most of the Cr3+ is present in chromite FeCr2O4 or other spinel minerals, where it replaces Fe and Al, to which it is very close in its geochemical properties and ionic radius.
Clarke of chromium in the earth's crust - 83 mg/kg. Its highest concentrations among igneous rocks are typical for ultramafic and basic rocks (1600-3400 and 170-200 mg/kg, respectively), the lowest 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 clayey sediments and shales (60-120 mg/kg), the minimum in sandstones and limestones (5-40 mg/kg) (Kabata-Pendias, Pendias, 1989). The metal content 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 cover loams averages 75-95 mg/kg (Yakushevskaya, 1973). Soil-forming rocks of Western Siberia contain on average 58 mg/kg Cr, and its amount is closely related to the granulometric composition of the rocks: sandy and sandy loam rocks - 16 mg/kg, and medium loamy and clayey rocks - about 60 mg/kg (Ilyin, Syso, 2001) .
In soils, most chromium is present in the form of Cr3+. In an acidic environment, the Cr3+ ion is inert; at pH 5.5, it almost completely precipitates. The Cr6+ 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 increasing pH, the adsorption of Cr6+ decreases, and Cr3+ increases. Soil organic matter stimulates the reduction of Cr6+ to Cr3+.
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), and the distribution along the soil profile depends on the characteristics of soil formation, in particular on the granulometric composition of genetic horizons. The average chromium content 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 soils of the USA is 54 mg/kg, China - 150 mg/kg (Kabata-Pendias, Pendias, 1989), Ukraine - 400 mg/kg (Bespamyatnov, 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. In the soils of the Urals, formed on serpentinites, the metal contains up to 10,000 mg/kg, in Western Siberia - 86 - 115 mg/kg (Yakushevskaya, 1973; Krasnokutskaya et al., 1990; Ilyin, Syso, 2001).
The contribution of anthropogenic sources to the supply of chromium is very significant. Chromium metal is primarily used for chrome plating as a component of alloy steels. Soil contamination with Cr is noted due to emissions from cement factories, 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 or more mg/kg (Kabata-Pendias, Pendias, 1989), which is especially characteristic major cities(Table 1.4). In Buryatia, according to land monitoring data carried out by the State Station of Agrochemical Service “Buryatskaya” for 1993-1997, 22 thousand hectares are contaminated with chromium. Excesses of MPC by 1.6-1.8 times were noted in Dzhidinsky (6.2 thousand hectares), Zakamensky (17.0 thousand hectares) and Tunkinsky (14.0 thousand hectares) regions.
Standardization of heavy metal content
in soil and plants is extremely complex due to the impossibility of fully taking into account all environmental factors. Thus, changing only the agrochemical properties of the soil (medium reaction, humus content, degree of saturation with bases, particle size distribution) can reduce or increase the content of heavy metals in plants several times. There are conflicting data even about the background content of some metals. The results given by researchers sometimes differ by 5-10 times.
Many scales have been proposed
environmental regulation of heavy metals. In some cases, the highest content of metals observed in ordinary anthropogenic soils is taken as the maximum permissible concentration; in others, the content that is the limit for phytotoxicity is taken. In most cases, MPCs have been proposed for heavy metals that are several times higher than the upper limit.
To characterize technogenic pollution
for heavy metals, a concentration coefficient is used equal to the ratio of the concentration of the element in contaminated soil to its background concentration. When polluted by several heavy metals, the degree of pollution is assessed by the value of the total concentration index (Zc). The scale of soil contamination with heavy metals proposed by IMGRE is presented in Table 1.
Table 1. Scheme for assessing soils for agricultural use according to the degree of contamination with chemicals (Goskomhydromet of the USSR, No. 02-10 51-233 dated 12/10/90)
| Soil category by degree of contamination | Zc | Pollution relative to MPC | Possible uses of soils | Necessary activities |
| Acceptable | <16,0 | Exceeds background, but not higher than MPC | Use for any crop | Reducing the impact of soil pollution sources. Reduced availability of toxicants for plants. |
| Moderately dangerous | 16,1- 32,0 | Exceeds the MPC for limiting general sanitary and water migration indicators of harmfulness, but is lower than the MPC for the translocation indicator | Use for any crops subject to quality control of crop products | Activities similar to category 1. If there are substances with a limiting migration water indicator, the content of these substances in surface and ground waters is monitored. |
| Highly dangerous | 32,1- 128 | Exceeds the MPC with a limiting translocation hazard indicator | Use for industrial crops without obtaining food and feed from them. Avoid chemical-concentrating plants | Activities similar to categories 1. Mandatory control over the content of toxicants in plants used as food and feed. Limiting the use of green mass for livestock feed, especially concentrator plants. |
| Extremely dangerous | > 128 | Exceeds MPC in all respects | Exclude from agricultural use | Reducing pollution levels and sequestration of toxicants in the atmosphere, soil and waters. |
Officially approved MPCs
Table 2 shows the officially approved maximum concentration limits and permissible levels of their content according to hazard indicators. In accordance with the scheme adopted by medical hygienists, the regulation of heavy metals in soils is divided into translocation (transition of the element into plants), migratory water (transition into water), and general sanitary (effect on the self-purifying ability of soils and soil microbiocenosis).
Table 2. Maximum permissible concentrations (MAC) of chemicals in soils and permissible levels of their content in terms of harmfulness (as of 01/01/1991. State Committee for Nature Protection of the USSR, No. 02-2333 dated 12/10/90).
| Name of substances | MPC, mg/kg soil, taking into account background | Harmfulness indicators | ||
| Translocation | Water | General sanitary | ||
| Water-soluble forms | ||||
| Fluorine | 10,0 | 10,0 | 10,0 | 10,0 |
| Movable forms | ||||
| Copper | 3,0 | 3,5 | 72,0 | 3,0 |
| Nickel | 4,0 | 6,7 | 14,0 | 4,0 |
| Zinc | 23,0 | 23,0 | 200,0 | 37,0 |
| Cobalt | 5,0 | 25,0 | >1000 | 5,0 |
| Fluorine | 2,8 | 2,8 | - | - |
| Chromium | 6,0 | - | - | 6,0 |
| Gross content | ||||
| Antimony | 4,5 | 4,5 | 4,5 | 50,0 |
| Manganese | 1500,0 | 3500,0 | 1500,0 | 1500,0 |
| Vanadium | 150,0 | 170,0 | 350,0 | 150,0 |
| Lead ** | 30,0 | 35,0 | 260,0 | 30,0 |
| Arsenic** | 2,0 | 2,0 | 15,0 | 10,0 |
| Mercury | 2,1 | 2,1 | 33,3 | 5,0 |
| Lead+mercury | 20+1 | 20+1 | 30+2 | 30+2 |
| Copper* | 55 | - | - | - |
| Nickel* | 85 | - | - | - |
| Zinc* | 100 | - | - | - |
* - gross content - approximate.
** - contradiction; for arsenic, the average background content is 6 mg/kg, the background content of lead usually also exceeds the MPC standards.
Officially approved by the UEC
The ADCs developed in 1995 for the gross content of 6 heavy metals and arsenic make it possible to obtain a more complete description of soil contamination with heavy metals, since they take into account the level of reaction of the environment and the granulometric composition of the soil.
Table 3. Approximate permissible concentrations (ATC) of heavy metals and arsenic in soils with different physicochemical properties (gross content, mg/kg) (addition No. 1 to the list of MPC and APC No. 6229-91).
| Element | Soil group | UDC taking into account the background | Aggregate state of the place in soils | Hazard classes | Peculiarities actions on the body |
| Nickel | Sandy and sandy loam | 20 | Solid: in the form of salts, in sorbed form, as part of minerals | 2 | Low toxicity for warm-blooded animals and humans. Has a mutagenic effect |
| <5,5 | 40 | ||||
| Close to neutral (loamy and clayey), рНKCl >5.5 | 80 | ||||
| Copper | Sandy and sandy loam | 33 | 2 | Increases cellular permeability, inhibits glutathione reductase, disrupts metabolism by interacting with -SH, -NH2 and COOH- groups | |
| Acidic (loamy and clayey), pH KCl<5,5 | 66 | ||||
| Close to neutral (loamy and clayey), pH KCl>5.5 | 132 | ||||
| Zinc | Sandy and sandy loam | 55 | Solid: in the form of salts, organo-mineral compounds, in sorbed form, as part of minerals | 1 | Deficiency or excess causes developmental deviations. Poisoning due to violation of technology for applying zinc-containing pesticides |
| Acidic (loamy and clayey), pH KCl<5,5 | 110 | ||||
| Close to neutral (loamy and clayey), pH KCl>5.5 | 220 | ||||
| Arsenic | Sandy and sandy loam | 2 | Solid: in the form of salts, organo-mineral compounds, in sorbed form, as part of minerals | 1 | Poisonous, inhibiting various enzymes, negative effect on metabolism. Possibly carcinogenic |
| Acidic (loamy and clayey), pH KCl<5,5 | 5 | ||||
| Close to neutral (loamy and clayey), pH KCl>5.5 | 10 | ||||
| Cadmium | Sandy and sandy loam | 0,5 | Solid: in the form of salts, organo-mineral compounds, in sorbed form, as part of minerals | 1 | It is highly toxic, blocks sulfhydryl groups of enzymes, disrupts the metabolism of iron and calcium, and disrupts DNA synthesis. |
| Acidic (loamy and clayey), pH KCl<5,5 | 1,0 | ||||
| Close to neutral (loamy and clayey), pH KCl>5.5 | 2,0 | ||||
| Lead | Sandy and sandy loam | 32 | Solid: in the form of salts, organo-mineral compounds, in sorbed form, as part of minerals | 1 | Versatile negative action. Blocks -SH groups of proteins, inhibits enzymes, causes poisoning and damage to the nervous system. |
| Acidic (loamy and clayey), pH KCl<5,5 | 65 | ||||
| Close to neutral (loamy and clayey), pH KCl>5.5 | 130 |
It follows from the materials that the requirements are mainly for bulk forms of heavy metals. Among the mobile ones are only copper, nickel, zinc, chromium and cobalt. Therefore, the currently developed standards no longer satisfy all requirements.
is a capacity factor, reflecting primarily the potential danger of contamination of plant products, infiltration and surface waters. Characterizes the general contamination of the soil, but does not reflect the degree of availability of elements for the plant. To characterize the state of soil nutrition of plants, only their mobile forms are used.
Definition of movable forms
They are determined using various extractants. The total amount of the mobile form of the metal is using an acidic extract (for example, 1N HCL). The most mobile part of the mobile reserves of heavy metals in the soil goes into the ammonium acetate buffer. The concentration of metals in a water extract shows the degree of mobility of elements in the soil, being the most dangerous and “aggressive” fraction.
Standards for movable forms
Several indicative normative scales have been proposed. Below is an example of one of the scales of maximum permissible mobile forms of heavy metals.
Table 4. Maximum permissible content of the mobile form of heavy metals in soil, mg/kg extractant 1N. HCl (H. Chuljian et al., 1988).
| Element | Content | Element | Content | Element | Content |
| Hg | 0,1 | Sb | 15 | Pb | 60 |
| Cd | 1,0 | As | 15 | Zn | 60 |
| Co | 12 | Ni | 36 | V | 80 |
| Cr | 15 | Cu | 50 | Mn | 600 |
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PAGE_BREAK-- heavy metals, which characterizes a wide group of pollutants, has recently become widespread. In various scientific and applied works, authors interpret the meaning of this concept differently. In this regard, the amount of elements classified as heavy metals varies widely. Numerous characteristics are used as membership criteria: atomic mass, density, toxicity, prevalence in the natural environment, degree of involvement in natural and man-made cycles. In some cases, the definition of heavy metals includes elements classified as brittle (for example, bismuth) or metalloids (for example, arsenic).
In works devoted to the problems of environmental pollution and environmental monitoring, today heavy metals include more than 40 metals of the periodic table D.I. Mendeleev with an atomic mass of over 50 atomic units: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, Sn, Hg, Pb, Bi etc. At the same time, there is a lot important role The following conditions play a role in the categorization of heavy metals: their high toxicity to living organisms in relatively low concentrations, as well as the ability to bioaccumulate and biomagnify. Almost all metals that fall under this definition (with the exception of lead, mercury, cadmium and bismuth, the biological role of which is currently unclear) are actively involved in biological processes, 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 include 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 engaged in practical activities related to organizing observations of the state and pollution of the environment, compounds of these elements are far from equivalent as pollutants. Therefore, in many works, the scope of the group of heavy metals is narrowed, in accordance with priority criteria determined by the direction and specifics of the work. Thus, in the now classic works of Yu.A. Israel in the list of chemical substances to be determined in natural environments at background stations in biosphere reserves, in section heavy metals named Pb, Hg, Cd, As. On the other hand, according to the decision of the Task Force on Heavy Metal Emissions, working under the auspices of the United Nations Economic Commission for Europe and collecting and analyzing information on pollutant emissions in European countries, only Zn, As, Se and Sb were attributed to heavy metals. According to N. Reimers’ definition, noble and rare metals stand apart from heavy metals, respectively, they 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 essential components of natural bodies of water. Depending on environmental conditions (pH, redox potential, presence of ligands), they exist in different oxidation states and are part of a variety of inorganic and organometallic compounds, which can be truly dissolved, colloidal dispersed, or part of mineral and organic suspensions.
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 their 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 migration of elements in natural waters. Most organic complexes are formed via the chelate cycle and are stable. 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 environments. Therefore, organometallic complexes are capable of migrating in natural waters over very long distances. This is especially important for low-mineralized and primarily surface waters, in which the formation of other complexes is impossible.
To understand the factors that regulate the concentration of metal 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 related forms metal
The transition of metals in an aqueous environment into a metal complex form has three consequences:
1. An increase in the total concentration of metal ions may occur 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 may change greatly as a result of complexation.
So, chelate forms Cu, Cd, Hg less toxic than free ions. To understand the factors that regulate the concentration of the metal 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.
Sources of water pollution with heavy metals are wastewater from electroplating shops, mining enterprises, ferrous and non-ferrous metallurgy, and machine-building plants. Heavy metals are found in fertilizers and pesticides and can enter water bodies through agricultural runoff.
Increased concentrations of heavy metals in natural waters are often associated with other types of pollution, such as acidification. Acid precipitation contributes to a decrease in pH and the transition of metals from a state sorbed on mineral and organic substances to a free state.
First of all, those metals of interest are those that most pollute the atmosphere due to their use in significant quantities in industrial 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
V - high, U - moderate, N - 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 pollution of natural waters with vanadium is oil and its refined products.
In natural waters it occurs in very low concentrations: in river water 0.2 - 4.5 μg/dm3, in sea water - on average 2 μg/dm3
In water it forms stable anionic complexes (V4O12)4- and (V10O26)6-. In the migration of vanadium, the role of dissolved complex compounds with organic substances, especially with humic acids, is significant.
Elevated concentrations of vanadium are harmful to human health. The MPC of vanadium is 0.1 mg/dm3 (the limiting hazard indicator is sanitary-toxicological), the MPCv is 0.001 mg/dm3.
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 production, and some glass industry enterprises.
It is found in submicrogram concentrations in unpolluted surface waters. The highest concentration was found in groundwater and is 20 μg/dm3, in sea waters - 0.02 μg/dm3. The MAC 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 the water in a dissolved, colloidal and suspended state. Significant amounts of iron come from underground runoff and wastewater from metallurgical, metalworking, textile, paint and varnish industries and agricultural runoff.
Phase equilibria depend on chemical composition water, pH, Eh and to some extent temperature. In routine analysis weighted form emit particles larger than 0.45 microns. It consists predominantly of iron-containing minerals, iron oxide hydrate and iron compounds sorbed in suspensions. The truly dissolved and colloidal forms are usually considered together. Dissolved iron is represented by compounds in ionic form, in the form of a hydroxo complex and complexes with dissolved inorganic and organic substances of natural waters. It is mainly Fe(II) that migrates in ionic form, and Fe(III) in the absence of complexing substances cannot be in a dissolved state in significant quantities.
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) transforms into Fe(III), which, when hydrolyzed, precipitates in the form of Fe(OH)3. Both Fe(II) and Fe(III) are characterized by a tendency to form hydroxo complexes of the type +, 4+, +, 3+, - and others, coexisting in solution in different concentrations depending on pH and generally determining the state of the iron-hydroxyl system. The main form 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 consists of iron oxide hydrate Fe(OH)3 and complexes with organic substances.
The iron content in surface waters of land is tenths of a milligram; near swamps it is a few milligrams. An increased iron content 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 high-quality composition microflora in the reservoir.
Iron concentrations are subject to marked seasonal fluctuations. Typically, in reservoirs with high biological productivity during the period of summer and winter stagnation, there is a noticeable increase in the concentration of iron in the bottom layers of water. Autumn-spring mixing of water masses (homothermy) 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 through 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 waters with wastewater from lead-zinc plants, ore processing plants, a number of chemical enterprises (sulfuric acid production), galvanic production, and also with mine waters. A 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 organomineral complexes. The main suspended form of cadmium is its sorbed compounds. A significant portion of cadmium can migrate within the cells of aquatic organisms.
In unpolluted and slightly polluted river 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 processes of animals and humans. In elevated concentrations it is toxic, especially in combination with other toxic substances.
The maximum permissible concentration is 0.001 mg/dm3, the maximum permissible concentration is 0.0005 mg/dm3 (the limiting sign of harm is toxicological).
Cobalt compounds enter natural waters as a result of leaching processes 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 decomposition of plant and animal organisms.
Cobalt compounds in natural waters are in a dissolved and suspended state, the quantitative relationship between which is determined by the chemical composition of the water, temperature and pH values. Dissolved forms are represented mainly by complex compounds, incl. with organic substances of natural waters. Compounds of divalent cobalt are most typical for surface waters. In the presence of oxidizing agents, trivalent cobalt can exist in noticeable concentrations.
Cobalt is one of the biologically active elements and is always found in the body of animals and plants. Insufficient cobalt content in soils is associated with insufficient cobalt content in plants, which contributes to the development of anemia in animals (taiga-forest non-chernozem zone). As part of vitamin B12, cobalt very actively influences the supply of nitrogenous substances, increases the content of chlorophyll and ascorbic acid, activates biosynthesis and increases the content of protein nitrogen in plants. However, increased concentrations of cobalt compounds are toxic.
In unpolluted and slightly polluted river waters, its content ranges from tenths to thousandths of a milligram per 1 dm3, the average content in sea water is 0.5 μg/dm3. The maximum permissible concentration is 0.1 mg/dm3, the maximum permissible concentration 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, braunite, manganite, black ochre). Significant amounts of manganese come from the decomposition of aquatic animals and plant organisms, especially blue-greens, diatoms and higher aquatic plants. Manganese compounds are carried into reservoirs with wastewater from manganese enrichment factories, 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 the rocks drained by the waters, as well as colloidal hydroxides of heavy metals and sorbed manganese compounds. Organic substances and the processes of complex formation of manganese with inorganic and organic ligands are of significant importance in the migration of manganese in dissolved and colloidal forms. Mn(II) forms soluble complexes with bicarbonates and sulfates. Complexes of manganese with chlorine ions 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) is not found 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.
Manganese concentrations in surface waters are subject to seasonal fluctuations.
The factors that determine 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 to the bottom of water bodies.
The role of manganese in the life of higher plants and algae in water bodies is very large. Manganese promotes the utilization of CO2 by plants, which increases the intensity of photosynthesis and 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 reservoirs for sanitary use, the maximum permissible concentration (MPC) (for manganese ion) is set to 0.1 mg/dm3.
Below are maps of the distribution of average concentrations of metals: manganese, copper, nickel and lead, constructed 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 substances and, accordingly, metals have significantly decreased.
Impact on health. Many metals are part of dust and have a significant impact on health.
Manganese enters the atmosphere from emissions from ferrous metallurgy (60% of all manganese emissions), mechanical engineering and metalworking (23%), non-ferrous metallurgy (9%), and numerous small sources, for example, from welding.
High concentrations of manganese lead to neurotoxic effects, progressive damage to the central nervous system, and pneumonia.
The highest concentrations of manganese (0.57 - 0.66 μg/m3) are observed in large centers of metallurgy: Lipetsk and Cherepovets, as well as Magadan. Most 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 active centers of redox enzymes. Insufficient copper content in soils negatively 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 most common in natural waters. Of the Cu(I) compounds, the most common are Cu2O, Cu2S, and CuCl, which are sparingly soluble in water. 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 water, and aldehyde reagents used to destroy algae. Copper can result from corrosion of copper piping and other structures used in water supply systems. In groundwater, the copper content is determined by 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 water use is 0.1 mg/dm3 (the limiting sign of hazard is general sanitary), in the water of fishery reservoirs - 0.001 mg/dm3.
City
Norilsk
Monchegorsk
Krasnouralsk
Kolchugino
Zapolyarny
Emissions M (thousand tons/year) of copper oxide and average annual concentrations q (μg/m3) of copper.
Copper enters the air with emissions from metallurgical production. In solid 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 approximately 25% of copper emissions are carried out in Revda and 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 were noted in the cities of Lipetsk and Rudnaya Pristan. Copper concentrations have also increased in the cities of the Kola Peninsula, in Zapolyarny, Monchegorsk, Nikel, Olenegorsk, as well as in Norilsk.
Copper emissions from industrial sources decreased by 34%, average concentrations by 42%.
Molybdenum
Molybdenum compounds enter surface waters as a result of leaching from exogenous molybdenum-containing minerals. 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 very likely that it exists in the form of organomineral complexes. The possibility of some accumulation in the colloidal state follows from the fact that the oxidation products of molybdenite are loose, finely dispersed substances.
In river waters, molybdenum was 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 molybdenum deficiency, the enzyme is formed in insufficient quantities, which causes negative reactions in the body. In elevated concentrations, molybdenum is harmful. With an excess of molybdenum, metabolism is disrupted.
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 pyrite, realgar, orpiment), as well as from zones of oxidation of polymetallic, copper-cobalt and tungsten rocks. Some arsenic comes from soils and also from decomposition of plant and animal organisms. The 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 plankton development.
Significant amounts of arsenic enter water bodies from wastewater from processing plants, dye production waste, tanneries and pesticide plants, as well as from agricultural lands where pesticides are used.
In natural waters, arsenic compounds are in a dissolved and suspended state, the relationship between which is determined by the chemical composition of the 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 an average of 3 µg/dm3, in underground waters it is found 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 and inhibit the oxygen supply to organs and tissues.
The maximum permissible concentration for arsenic is 0.05 mg/dm3 (the limiting hazard indicator is sanitary-toxicological) and the maximum permissible concentration for arsenic is 0.05 mg/dm3.
The presence of nickel in natural waters is due to the composition of the rocks through which the water passes: it is found in places where sulfide copper-nickel ores and iron-nickel ores are deposited. It enters water from soils and from plant and animal organisms during their decay. Increased nickel content 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 concentration factories. Huge nickel emissions accompany the burning of fossil fuels.
Its concentration may 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 composition of the water, temperature and pH values. Sorbents for nickel compounds can be iron hydroxide, organic substances, highly dispersed calcium carbonate, and clays. Dissolved forms are primarily complex ions, most commonly with amino acids, humic and fulvic acids, and also as a strong cyanide complex. The most common nickel compounds in natural waters are those in which it is found in the +2 oxidation state. Ni3+ compounds are usually formed in an alkaline environment.
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 approximately 2 times more toxic than its complex compounds.
In unpolluted and slightly polluted river waters, the concentration of nickel usually ranges from 0.8 to 10 μg/dm3; in polluted ones it amounts to 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 groundwater washing nickel-containing rocks, the concentration of nickel sometimes increases 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.
Increased nickel content in the environment leads to the emergence of endemic diseases, bronchial cancer. Nickel compounds belong to group 1 carcinogens.
The map shows several points with high average nickel concentrations 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 M (thousand tons/year) and average annual concentrations q (µg/m3) of nickel.
It enters natural waters as a result of leaching processes of tin-containing minerals (cassiterite, stannin), as well as with wastewater from various industries (dying of fabrics, synthesis of organic paints, production of alloys with the addition of tin, etc.).
The toxic effect of tin is small.
In unpolluted surface waters, tin is found in submicrogram concentrations. In groundwater its concentration reaches a few micrograms per 1 dm3. The maximum permissible concentration 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, livingstonite), during the decomposition of aquatic organisms that accumulate mercury. Significant quantities 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 end up in water bodies as a result of wet and dry deposition.
A 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 substances and bottom sediments.
In surface waters, mercury compounds are in a dissolved and suspended state. The ratio between them depends on the chemical composition of the water and pH values. Suspended mercury is sorbed mercury compounds. Dissolved forms are undissociated molecules, complex organic and mineral compounds. Mercury can be present in the water of water bodies 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.
The maximum permissible concentration of mercury is 0.0005 mg/dm3 (the limiting sign of hazard is sanitary-toxicological), the maximum permissible concentration is 0.0001 mg/dm3.
Natural sources of lead entering surface waters are the dissolution processes 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 anti-knock agent in motor fuel, and the discharge into water bodies with wastewater from ore processing factories, some metallurgical plants, chemical plants, mines, etc. Significant factors in reducing the concentration of lead in water are its adsorption by suspended substances and precipitation with them into bottom sediments. Lead, among other metals, is extracted and accumulated by aquatic organisms.
Lead is found in natural waters in a dissolved and suspended (sorbed) state. In dissolved form it is found 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 concentration of lead 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 does the concentration of lead sometimes reach several milligrams per 1 dm3.
The limiting indicator of the harmfulness of lead is sanitary-toxicological. The maximum permissible concentration for lead is 0.03 mg/dm3, the maximum permissible concentration for lead is 0.1 mg/dm3.
Lead is contained in emissions from metallurgy, metalworking, electrical engineering, petrochemical and motor transport enterprises.
The impact of lead on health occurs through inhalation of lead-containing air and ingestion of lead through 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.
Over seven years, lead emissions from industrial sources fell by 60% due to production cuts and many plant closures. The sharp decrease in industrial emissions is not accompanied by a decrease in vehicle emissions. Average lead concentrations decreased by only 41%. The differences in lead emission reductions and concentrations may be explained by under-reporting of vehicle emissions in previous years; Currently, the number of cars and the intensity of their traffic have increased.
Tetraethyl lead
It enters natural waters due to its use as an antiknock agent in motor fuel of water vehicles, as well as with surface runoff from urban areas.
This substance is characterized by high toxicity and has cumulative properties.
The sources of silver entering surface waters are groundwater and wastewater from mines, processing plants, and photographic enterprises. Increased silver content 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 ranges 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 even in small concentrations they sterilize water (the lower limit of the bactericidal effect of silver ions is 2.10-11 mol/dm3). The role of silver in the body of animals and humans has not been sufficiently studied.
The MPC of silver is 0.05 mg/dm3.
Antimony enters surface waters due to the leaching of antimony minerals (stibnite, senarmontite, valentinite, servantite, stibiocanite) and with wastewater from rubber, glass, dyeing, and match factories.
In natural waters, antimony compounds are in a dissolved and suspended state. Under the redox conditions characteristic of surface waters, the existence of both trivalent and pentavalent antimony is possible.
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. The MPC of antimony is 0.05 mg/dm3 (the limiting hazard indicator is sanitary-toxicological), the 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 amounts come from the decomposition of organisms and plants from soils. Significant quantities may enter water bodies with wastewater from electroplating shops, dyeing shops of textile factories, tanneries and chemical industry enterprises. 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, remains of plant and animal organisms. In dissolved form, chromium can be found in the form of chromates and dichromates. Under aerobic conditions, Cr(VI) transforms into Cr(III), the salts of which hydrolyze in neutral and alkaline media to release hydroxide.
In unpolluted and slightly polluted river waters, the chromium content ranges from a few 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 the range of n.10 - n.102 µg/dm3.
Compounds of Cr(VI) and Cr(III) in increased quantities have carcinogenic properties. Cr(VI) compounds are more dangerous.
It enters natural waters as a result of the processes of destruction and dissolution of rocks and minerals occurring in nature (sphalerite, zincite, goslarite, smithsonite, calamine), as well as with wastewater from ore processing factories and electroplating shops, production of parchment paper, mineral paints, viscose fiber and etc.
In water it exists mainly in ionic form or in the form of its mineral and organic complexes. Sometimes found in insoluble forms: as hydroxide, carbonate, sulfide, etc.
In river waters, the concentration of zinc usually ranges from 3 to 120 μg/dm3, in sea waters - from 1.5 to 10 μg/dm3. The content in ore waters and especially in mine waters with low pH values can be significant.
Zinc is one of the active microelements that influence the growth and normal development of organisms. At the same time, many zinc compounds are toxic, primarily its sulfate and chloride.
The MPC for Zn2+ is 1 mg/dm3 (the limiting indicator of harm is organoleptic), the MPC for Zn2+ is 0.01 mg/dm3 (the limiting indicator of harm is toxicological).
Heavy metals already occupy the second place in terms of danger, inferior to pesticides and significantly ahead of such well-known pollutants as carbon dioxide and sulfur, and 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 priority pollutants, monitoring of which is mandatory in all environments. In various scientific and applied works, authors interpret the meaning of the concept of “heavy metals” differently. In some cases, the definition of heavy metals includes elements classified as brittle (for example, bismuth) or metalloids (for example, arsenic).
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 flow from it into the World Ocean. From the soil, heavy metals are absorbed by plants, which then become food for more highly organized animals.
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--PAGE_BREAK-- 3.3. Lead toxicity
Currently, lead ranks first among the causes of industrial poisoning. This is due to its widespread use in various industries. Workers mining lead ore, in lead smelters, in the production of batteries, during soldering, in printing houses, in the production of crystal glass or ceramic products, leaded gasoline, lead paints, etc. are exposed to lead. Lead pollution of atmospheric air, soil and water in the vicinity of such industries, as well as near major highways, poses 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 public policy on legal, regulatory and economic regulation of the impact of lead on the environment and public health, on reducing emissions (discharges, waste) of lead and its compounds into the environment, and completely stopping the production of lead-containing gasoline.
Due to extremely unsatisfactory educational work to explain to the population the degree of danger of the effects of heavy metals on the human body, in Russia the number of contingents with professional 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 (battery production), instrument making, printing and non-ferrous metallurgy, in them, intoxication is caused by exceeding the maximum permissible concentration (MPC) of lead in the air of the working area by 20 or more times.
A significant source of lead is automobile exhaust fumes, 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 of the largest sources of lead emissions in the country: in the cities of Krasnouralsk, Kirovograd and Revda.
The chimneys of the Krasnouralsk copper smelter, built during the years of Stalinist industrialization and using equipment from 1932, annually spew 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 a maximum permissible concentration of MPC = 130 μ/kg. Water samples in the water supply of a neighboring village. Oktyabrsky, fed by an underground water source, exceeded the maximum permissible concentration by up to two times.
Lead pollution of the environment affects human health. Exposure to lead 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 under the influence of lead menstrual function is disrupted, premature births, miscarriages and fetal death are more common due to the penetration of lead through the placental barrier. Newborn babies 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 aged 4 years and older revealed a significant delay in mental development in 75.7%, and mental retardation, including mental retardation, was found in 6.8% of the children examined.
Preschool-age children are most susceptible to the harmful effects of lead because their nervous systems are in the developing stages. Even at low doses, lead poisoning causes a decrease in intellectual development, attention and ability to concentrate, a lag in reading, and leads to the development of aggressiveness, hyperactivity and other problems in the child’s behavior. These developmental abnormalities can be long-lasting and irreversible. Low birth weight, stunting and hearing loss also result from 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 numerous environmental disasters in the former Soviet Union that have come to light in last years. Most of the territory of Russia experiences a load from lead deposition that exceeds the critical load for the normal functioning of the ecosystem. In dozens of cities, lead concentrations in the air and soil exceed the values corresponding to the maximum permissible concentrations.
The highest level of air pollution with lead, exceeding the maximum permissible concentration, 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 discharge 35 tons of lead annually through sewer system. An analysis of the distribution of lead discharges into water bodies in Russia shows that the 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 for now Russia's economic crisis is overshadowing environmental problems. In a long-running industrial depression, Russia lacks the means to clean up past pollution, but if the economy begins to recover and factories return to work, pollution could only worsen.
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 populated areas and their surroundings has long been different from natural, biologically valuable soil, which plays an important role in maintaining ecological balance. The soil in cities is subject to the same harmful effects as the urban air and hydrosphere, so significant degradation occurs everywhere. Soil hygiene is not given enough 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 quantity of the latter (primarily the quality of groundwater) is determined by the condition 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, the breakdown of waste that enters it and its mineralization occurs; Ultimately, the soil compensates for the lost minerals at their expense.
If, as a result of overloading the soil, any of the components of its mineralizing ability is lost, this will inevitably lead to a disruption of the self-purification mechanism and to complete degradation of the soil. And, on the contrary, creating optimal conditions for self-purification of the soil helps maintain ecological balance and conditions for the existence of all living organisms, including humans.
Therefore, the problem of neutralizing waste that has harmful biological effects is not limited to the issue of their removal; it is a more complex hygienic problem, since soil is the link between water, air and humans.
4.1.
The role of soil in metabolism
The biological relationship between soil and humans is carried out mainly through metabolism. The soil is like a supplier minerals, necessary for the metabolic cycle, for the growth of plants consumed by humans and herbivores, which in turn are eaten by humans and carnivores. Thus, the soil provides food for many representatives of the plant and animal world.
Consequently, the deterioration of soil quality, a decrease in its biological value, and its ability to self-purify cause a biological chain reaction, which, in the case of prolonged harmful effects, can lead to a variety of health disorders among the population. Moreover, if mineralization processes are slowed down, nitrates, nitrogen, phosphorus, potassium, etc. formed during the breakdown of substances can enter groundwater used for drinking purposes and cause serious diseases (for example, nitrates can cause methemoglobinemia, primarily in infants).
Consumption of water from iodine-poor soil can cause endemic goiter, etc.
4.2.
Ecological relationship between soil and water and liquid waste (wastewater)
Man extracts from the soil the water necessary to maintain metabolic processes and life itself. Water quality depends on soil conditions; it always reflects the biological state of a given soil.
This especially applies to groundwater, the biological value of which is significantly determined by the properties of soil and soil, the latter’s ability to self-purify, its filtration capacity, the composition of its macroflora, microfauna, etc.
The direct influence of soil on surface waters is less significant; it is associated mainly with precipitation. For example, after heavy rains, various pollutants are washed from the soil into open bodies of water (rivers, lakes), including artificial fertilizers (nitrogen, phosphate), pesticides, herbicides; in areas of karst and fractured deposits, pollutants can penetrate through cracks into deep-lying The groundwater.
Inadequate wastewater treatment can also cause harmful biological effects on the soil and ultimately lead to soil degradation. Therefore, soil protection in populated areas is one of the main requirements for protecting the environment as a whole.
4.3.
Limits of soil load with solid waste (household and street garbage, industrial waste, dry sludge remaining after sedimentation of wastewater, radioactive substances, etc.)
The problem is compounded by the fact that, as a result of the generation of increasing amounts of solid waste in cities, the soil in their surroundings is subject to increasingly significant stress. The properties and composition of the soil are deteriorating at an increasingly rapid pace.
Of the 64.3 million tons of paper produced in the United States, 49.1 million tons end up in waste (of this amount, 26 million tons are “supplied” household, and 23.1 million tons - distribution network).
In connection with the above, the removal and final neutralization of solid waste represents a very significant, more difficult to implement hygienic problem in the conditions of increasing urbanization.
The final neutralization of solid waste in contaminated soil seems possible. However, due to the constantly deteriorating ability of urban soil to self-purify, final neutralization 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 activity in cities, has long become unsuitable for this purpose.
The mechanisms of self-purification and mineralization occurring in the soil, the role of the bacteria and enzymes involved in them, as well as 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 natural soil, as well as at clarifying the question of what amount of solid waste (and what its composition) can lead to disruption of the biological balance of the soil.
Amount of household waste (garbage) per inhabitant of some major cities of the world
It should be noted that the hygienic condition of soil in cities quickly deteriorates as a result of its overload, although the ability of the soil to self-purify is the main hygienic requirement for maintaining biological balance. The soil in cities is no longer able to cope with its task without human help. The only way out of this situation position - full 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 entering the soil, which it is not able to cope with. For example, soil contamination with arsenic has been established in the vicinity of superphosphate production plants (within a radius of 3 km). As is known, some pesticides, such as organochlorine compounds that enter 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 enter groundwater sooner or later, as a result of which not only the biological balance of the soil is disrupted, 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 heat-hardening plastics.
The problem of waste has increased these days 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 city problem has spread to the city's surrounding areas.
4.4.
The role of soil in the spread of various diseases
Soil plays a certain 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 fever, 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, and the causative agent of paratyphoid fever - from 30 to 60 days. (From the point of view of the spread of infectious diseases, urban soil poses a much greater danger than field soil fertilized with manure.)
To determine the degree of soil contamination, a number of authors use the determination of bacterial count (Escherichia coli), as in determining water quality. Other authors consider it advisable to determine, in addition, the number of thermophilic bacteria taking part in the mineralization process.
The spread of infectious diseases through soil is greatly facilitated by irrigation of land with wastewater. At the same time, the mineralization properties of the soil deteriorate. Therefore, irrigation with wastewater should be carried out under constant strict sanitary supervision and only outside the urban area.
4.5.
Harmful effects of the main types of pollutants (solid and liquid waste) leading to soil degradation
4.5.1.
Neutralization of liquid waste in soil
In a number settlements where there is no sewage system, some waste, including manure, is neutralized in the soil.
As you know, this is the simplest method of neutralization. However, it is only permissible if we are dealing with biologically complete 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 structures for the neutralization of liquid waste.
In some places, waste is neutralized in compost pits. From a technical standpoint, this solution is challenging. In addition, liquids can 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, which worsens the mineralization properties of the soil to an even greater extent than human and animal feces. Therefore in compost pits It is permissible to discharge only wastewater that has been pre-sedimented. Otherwise, the filtration capacity of the soil is disrupted, then the soil loses the remaining protective properties, pores gradually become clogged, etc.
The use of human feces to irrigate agricultural fields represents a second method of neutralizing liquid waste. This method poses 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 fertilizer. Here two opposing points of view collide. According to hygienic requirements, feces are subject to almost complete destruction, and from the point of view of the national economy they represent a valuable fertilizer. Fresh feces cannot be used to water 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 no longer represent almost any value as a fertilizer.
Feces can be used as fertilizer only in specially designated areas - with constant sanitary and hygienic control, especially over the state of groundwater, quantity, flies, etc.
The requirements for the removal and soil neutralization of animal feces are, in principle, no different from the requirements for the neutralization of human feces.
Until recently, manure represented in agriculture a significant source of valuable nutrients necessary to increase 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 neutralization, manure is also dangerous, just like unneutralized human feces. Therefore, before being taken out to the fields, manure is allowed to ripen so that during this time the necessary biothermal processes can occur in it (at a temperature of 60-70°C). After this, the manure is considered “mature” and freed from most of the pathogens it contains (bacteria, worm eggs, etc.).
It must be remembered that manure storage facilities can provide ideal breeding grounds for flies that contribute to the spread of various intestinal infections. It should be noted that flies most readily choose pig manure for reproduction, then horse manure, sheep manure, and then last resort cow Before transporting manure to fields, it must be treated with insecticides.
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The chemical composition of soils in different territories is heterogeneous and the distribution of chemical elements contained in soils across the territory is uneven. For example, being predominantly in a dispersed state, heavy metals are capable of forming local bonds, where their concentrations are many hundreds and thousands of times higher than clarke levels.
A number of chemical elements are necessary for the normal functioning of the body. Their deficiency, excess or imbalance can cause diseases called microelementoses 1, or biogeochemical endemics, which can be both natural and man-made. In their distribution, an important role is played by water, as well as food products, into which chemical elements enter from the soil through food chains.
It has been experimentally established that the percentage of HMs in plants is influenced by the percentage of HMs in the soil, atmosphere, and water (in the case of algae). It was also noticed that on soils with the same content of heavy metals, the same crop produces different yields, although the climatic conditions also coincided. Then the dependence of yield on soil acidity was discovered.
The most studied soil contaminations are cadmium, mercury, lead, arsenic, copper, zinc and manganese. Let us consider soil contamination with these metals separately for each. 2
Cadmium (Cd)
The cadmium content in the earth's crust is approximately 0.15 mg/kg. Cadmium is concentrated in volcanic (in quantities from 0.001 to 1.8 mg/kg), metamorphic (in quantities from 0.04 to 1.0 mg/kg) and sedimentary rocks (in quantities from 0.1 to 11.0 mg/kg). Soils formed on the basis of such initial materials contain 0.1-0.3; 0.1 - 1.0 and 3.0 - 11.0 mg/kg cadmium, respectively.
In acidic soils, cadmium is present in the form of Cd 2+, CdCl +, CdSO 4, and in calcareous soils - in the form of Cd 2+, CdCl +, CdSO 4, CdHCO 3 +.
The uptake of cadmium by plants decreases significantly when acidic soils are limed. In this case, an increase in pH reduces the solubility of cadmium in soil moisture, as well as the bioavailability of soil cadmium. Thus, the cadmium content in beet leaves on calcareous soils was lower than the cadmium content in the same plants on unlimed soils. A similar effect has been shown for rice and wheat -->.
The negative effect of increasing pH on cadmium availability is associated with a decrease not only in the solubility of cadmium in the soil solution phase, but also in root activity, which affects absorption.
Cadmium is rather little mobile in soils, and if cadmium-containing material is added to its surface, the bulk of it remains untouched.
Methods for removing contaminants from soil include either removing the contaminated layer itself, removing cadmium from the layer, or covering the contaminated layer. Cadmium can be converted into complex insoluble compounds by available chelating agents (eg ethylenediaminetetraacetic acid). .
Because of the relatively rapid uptake of cadmium from soil by plants and the low toxicity of commonly occurring concentrations, cadmium can accumulate in plants and enter the food chain faster than lead and zinc. Therefore, cadmium poses the greatest danger to human health when introducing waste into soil.
A procedure for minimizing the amount of cadmium that can enter the human food chain from contaminated soils is to grow non-food crops or crops that absorb small amounts of cadmium in the soil.
In general, crops grown on acidic soils absorb more cadmium than those grown on neutral or alkaline soils. Therefore, liming of acidic soils is an effective means of reducing the amount of absorbed cadmium.
Mercury (Hg)
Mercury is found in nature in the form of metal vapor Hg 0 formed during its evaporation from the earth's crust; in the form of inorganic salts Hg(I) and Hg(II), and in the form of an organic compound of methylmercury CH 3 Hg +, monomethyl and dimethyl derivatives CH 3 Hg + and (CH 3) 2 Hg.
Mercury accumulates in the upper horizon (0-40 cm) of the soil and weakly migrates into its deeper layers. Mercury compounds are highly stable soil substances. Plants growing on mercury-contaminated soil absorb significant amounts of the element and accumulate it in dangerous concentrations, or do not grow.
Lead (Pb)
According to experiments conducted in sandy culture conditions with the introduction of threshold soil concentrations of Hg (25 mg/kg) and Pb (25 mg/kg) and exceeding the threshold concentrations by 2-20 times, oat plants grow and develop normally up to a certain level of contamination. As the concentration of metals increases (for Pb starting from a dose of 100 mg/kg), the appearance plants. At extreme doses of metals, plants die within three weeks from the start of the experiments. The content of metals in biomass components is distributed in descending order as follows: roots - aboveground part - grain.
The total input of lead into the atmosphere (and therefore partially into the soil) from motor transport in Russia in 1996 was estimated at approximately 4.0 thousand tons, including 2.16 thousand tons contributed by freight transport. The maximum load of lead occurred in the Moscow and Samara regions, followed by the Kaluga, Nizhny Novgorod, Vladimir regions and other constituent entities of the Russian Federation located in the central part of the European territory of Russia and the North Caucasus. The highest absolute emissions of lead were observed in the Ural (685 t), Volga (651 t) and West Siberian (568 t) regions. And the most adverse impact of lead emissions was noted in Tatarstan, Krasnodar and Stavropol territories, Rostov, Moscow, Leningrad, Nizhny Novgorod, Volgograd, Voronezh, Saratov and Samara regions (newspaper “ Green World”, special issue No. 28, 1997).
Arsenic (As)
Arsenic is found in the environment in a variety of chemically stable forms. Its two main oxidation states are As(III), and As(V). Pentavalent arsenic is common in nature in the form of a variety of inorganic compounds, although trivalent arsenic is easily detected in water, especially under anaerobic conditions.
Copper(Cu)
Natural copper minerals in soils include sulfates, phosphates, oxides and hydroxides. Copper sulfides can form in poorly drained or flooded soils where reducing conditions occur. Copper minerals are usually too soluble to remain in free-draining agricultural soils. In metal-contaminated soils, however, the chemical environment may be controlled by non-equilibrium processes leading to the accumulation of metastable solid phases. It is assumed that covellite (CuS) or chalcopyrite (CuFeS 2) may also be present in restored soils contaminated with copper.
Trace amounts of copper may occur as isolated sulfide inclusions in silicates and can isomorphously replace cations in phyllosilicates. Clay minerals that are unbalanced in charge absorb copper nonspecifically, but oxides and hydroxides of iron and manganese show a very high specific affinity for copper. High molecular weight organic compounds can be solid absorbents for copper, while low molecular weight organic substances tend to form soluble complexes.
The complexity of soil composition limits the ability to quantitatively separate copper compounds into specific chemical forms. indicates --> Availability large mass copper conglomerates are found both in organic substances and in Fe and Mn oxides. The introduction of copper-containing waste or inorganic copper salts increases the concentration of copper compounds in the soil that can be extracted with relatively mild reagents; Thus, copper can be present in the soil in the form of labile chemical forms. But the easily soluble and replaceable element - copper - forms a small amount of forms capable of absorption by plants, usually less than 5% of the total copper content in the soil.
Copper toxicity increases with increasing soil pH and when soil cation exchange capacity is low. Enrichment of copper through extraction occurs only in the surface layers of the soil, and grain crops with deep root systems do not suffer from this.
The environment and plant nutrition can influence copper phytotoxicity. For example, copper toxicity to lowland rice was clearly observed when the plants were watered with cold rather than warm water. The fact is that microbiological activity is suppressed in cold soil and creates those reducing conditions in the soil that would facilitate the precipitation of copper from solution.
Copper phytotoxicity occurs initially from an excess of available copper in the soil and is enhanced by soil acidity. Since copper is relatively inactive in the soil, almost all copper entering the soil remains in upper layers. The addition of organic substances to copper-contaminated soils can reduce toxicity due to the adsorption of the soluble metal by the organic substrate (in this case, Cu 2+ ions are converted into complex compounds less accessible to the plant) or by increasing the mobility of Cu 2+ ions and leaching them from the soil in the form of soluble organocopper complexes.
Zinc (Zn)
Zinc can be present in the soil in the form of oxosulfates, carbonates, phosphates, silicates, oxides and hydroxides. These inorganic compounds are metastable in well-drained agricultural land. Sphalerite ZnS appears to be the thermodynamically dominant form in both reduced and oxidized soils. Some association of zinc with phosphorus and chlorine is evident in reduced sediments contaminated with heavy metals. Therefore, relatively soluble zinc salts should be found in metal-rich soils.
Zinc is isomorphously replaced by other cations in silicate minerals and can be occluded or coprecipitated with manganese and iron hydroxides. Phyllosilicates, carbonates, hydrated metal oxides, and organic compounds absorb zinc well, using both specific and nonspecific binding sites.
The solubility of zinc increases in acidic soils, as well as during complex formation with low molecular weight organic ligands. Reducing conditions can reduce the solubility of zinc due to the formation of insoluble ZnS.
Zinc phytotoxicity usually occurs when plant roots come into contact with a solution in the soil that contains excess zinc. Transport of zinc through soil occurs through exchange and diffusion, with the latter process being dominant in soils low in zinc. Metabolic transport is more significant in high-zinc soils, in which soluble zinc concentrations are relatively stable.
The mobility of zinc in soils increases in the presence of chelating agents (natural or synthetic). The increase in soluble zinc concentration caused by the formation of soluble chelates compensates for the decrease in mobility caused by the increase in molecular size. Plant tissue zinc concentrations, total uptake, and toxicity symptoms are positively correlated with the zinc concentration in the solution bathing the plant roots.
Free Zn 2+ ion is predominantly absorbed by the root system of plants, therefore the formation of soluble chelates promotes the solubility of this metal in soils, and this reaction compensates for the reduced availability of zinc in chelated form.
The initial form of metal contamination affects the potential for zinc toxicity: the availability of zinc to plants in fertilized soils with an equivalent total content of this metal decreases in the order ZnSO 4 >sludge >garbage compost.
Most experiments on soil contamination with Zn-containing sludge did not show a decrease in yield or their obvious phytotoxicity; However, their long-term application at high speed can damage plants. A simple application of zinc in the form of ZnSO 4 causes a decrease in crop growth in acidic soils, while its long-term application in almost neutral soils goes unnoticed.
Zinc reaches toxic levels in agricultural soils typically from surface zinc; it usually does not penetrate deeper than 15-30 cm. The deep roots of certain crops can avoid contact with excess zinc due to their location in uncontaminated subsoil.
Liming of soils contaminated with zinc reduces the concentration of the latter in field crops. Additions of NaOH or Ca(OH) 2 reduce the toxicity of zinc in vegetable crops grown on high-zinc peat soils, although in these soils the uptake of zinc by plants is very limited. Iron deficiency caused by zinc can be eliminated by adding iron chelates or FeSO 4 to the soil or directly to the leaves. Physically removing or burying the zinc-contaminated top layer may avoid toxic effects of the metal on plants altogether.
Manganese
In soil, manganese is found in three oxidation states: +2, +3, +4. For the most part, this metal is associated with primary minerals or with secondary metal oxides. In the soil, the total amount of manganese ranges from 500 to 900 mg/kg.
The solubility of Mn 4+ is extremely low; trivalent manganese is very unstable in soils. Most of the manganese in soils is present in the form of Mn 2+, while in well-aerated soils most of it in the solid phase is present in the form of oxide, in which the metal is in oxidation state IV; in poorly aerated soils, manganese is slowly restored by the microbial environment and passes into the soil solution, thus becoming highly mobile.
The solubility of Mn 2+ increases significantly at low pH values, but the uptake of manganese by plants decreases.
Manganese toxicity often occurs where total manganese levels are moderate to high, soil pH is quite low, and soil oxygen availability is low (i.e., reducing conditions exist). To eliminate the effects of these conditions, the soil pH should be increased by liming, efforts should be made to improve soil drainage, and the flow of water should be reduced, i.e. generally improve the structure of a given soil.