• Domestic science and medicine in the 19th - early 20th centuries Chemistry of the 19th century in medicine
• What are peptides? Types and types of peptides. All about peptides and anti-aging cosmetics with peptides Additional peptides are not formed
• Toxic effect on humans of hazardous chemicals
• Radioautography Method of autoradiography in cytology
• Identification of bacteria by antigenic structure
• Organic matter in wastewater What are organic compounds in water
• Hydrogen index (pH factor)
• What is the pH of water and why is it important to know it?
• Redox potential Redox systems
• Reversible redox system Reversible redox systems

Chapter 11. ECOLOGICAL ASPECTS OF CHEMICAL ELEMENTS

Chapter 11. ECOLOGICAL ASPECTS OF CHEMICAL ELEMENTS

Chemical elements are one of the components of the ecological portrait of a person.

A.V. rocky

11.1. CURRENT PROBLEMS OF SUSTAINABLE DEVELOPMENT OF THE BIOSPHERE OF RUSSIA

Anthropogenic pollution of the environment has a significant impact on the health of plants and animals (Ermakov V.V., 1995). The annual production of world land vegetation before its disturbance by man had a value close to 172 10 9 tons of dry matter (Bazilevich NI, 1974). As a result of the impact, its natural production has now decreased by at least 25% (Panin M.S., 2006). In the publications of V.V. Ermakova (1999), Yu.M. Zakharova (2003), I.M. Donnik (1997), M.S. Panina (2003), G.M. Hove (1972), D.R. Burkitt (1986) et al. showed the increasing aggressiveness of anthropogenic impacts on the environment (OS) that take place in the territories of developed countries.

V.A. Kovda, back in 1976, provided data on the ratio of natural biogeochemical cycles and the anthropogenic contribution to natural processes; since then, technogenic flows have increased. According to his data, biogeochemical and technogenic flows of the biosphere are estimated by the following values:

According to the World Health Organization (WHO), out of more than 6 million known chemical compounds, up to 500,000 are used, of which 40,000 have properties that are harmful to humans, and 12,000 are toxic. By 2000, the consumption of mineral and organic raw materials increased dramatically and reached 40-50 thousand tons per inhabitant of the Earth. Accordingly, the volumes of industrial, agricultural and household waste are increasing. By the beginning of the 21st century, anthropogenic pollution has brought mankind to the brink of an ecological catastrophe (Ermakov V.V., 2003). Therefore, the analysis of the ecological state of the Russian biosphere and the search for ways of ecological rehabilitation of its territory are very relevant.

Currently, about 7 billion tons of waste is generated annually at the enterprises of the mining, metallurgical, chemical, woodworking, energy, building materials and other industries of the Russian Federation. Only 2 billion tons, or 28% of the total volume, is used. In this regard, about 80 billion tons of solid waste alone have been accumulated in the dumps and sludge storages of the country. About 10 thousand hectares of land suitable for agriculture are annually alienated for landfills for their storage. The largest amount of waste is obtained during the extraction and enrichment of raw materials. Thus, in 1985, the volume of overburden, associated rocks and tailings in various industries of the USSR was 3,100 and 1,200 million m 3, respectively. A large amount of waste is generated during the harvesting and processing of wood raw materials. At logging sites, wastes account for up to 46.5% of the total volume of timber exported. In our country, more than 200 million m 3 of wood waste is generated annually. Somewhat less waste is produced at ferrous metallurgy enterprises: in 1984, the output of fire-liquid slag amounted to 79.7 million tons, including 52.2 million tons of blast-furnace, 22.3 million tons of steel and 4.2 million tons of ferroalloys. In the world, non-ferrous metals are annually smelted approximately 15 times less than ferrous ones. However, in the production of non-ferrous metals in the process of ore enrichment, from 30 to 100 tons of crushed tailings are formed per 1 ton of concentrates, and during the smelting of ore

for 1 ton of metal - from 1 to 8 tons of slag, sludge and other waste (Dobrovolsky IP, Kozlov Yu. E. et al., 2000).

Every year, enterprises of chemical, food, mineral fertilizers and other industries generate more than 22 million tons of gypsum-containing waste and about 120-140 million tons of sewage sludge (in dry form), about 90% of which are obtained by neutralizing industrial wastewater. More than 70% of waste heaps in Kuzbass are on fire. At a distance of several kilometers from them, the concentrations of SO 2 , CO, CO 2 are significantly increased in the air. The concentration of heavy metals in soils and surface waters sharply increases, and in the areas of uranium mines - radionuclides. Open pit mining leads to landscape disturbances, which are commensurate in scale with the consequences of major natural disasters. Thus, numerous chains of deep (up to 30 m) sinkholes were formed in the mining area in Kuzbass, stretching for more than 50 km, with a total area of ​​up to 300 km 2 and sink volumes of more than 50 million m 3.

Currently, vast areas are occupied by solid waste from thermal power plants: ash, slag, similar in composition to metallurgical ones. Their annual output reaches 70 million tons. The degree of their use is within 1-2%. According to the Ministry of Natural Resources of the Russian Federation, the total area of ​​land occupied by waste from various industries, as a whole, exceeds 2000 km2.

More than 40 billion tons of crude oil are produced annually in the world, of which about 50 million tons of oil and oil products are lost during production, transportation and processing. Oil is considered one of the most widespread and most dangerous pollutants in the hydrosphere, since about a third of it is produced on the continental shelf. The total mass of oil products annually entering the seas and oceans is approximately estimated at 5-10 million tons.

According to NPO Energostal, the degree of purification of exhaust gases from ferrous metallurgy dust exceeds 80%, and the degree of utilization of solid capture products is only 66%. At the same time, the coefficient of utilization of iron-containing dusts and slags is 72%, while for other types of dusts it is 46%. Practically at all enterprises, both metallurgical and thermal power plants, the issues of cleaning aggressive low-percentage sulfur-containing gases are not solved. Emissions of these gases in the USSR amounted to 25 million tons. Emissions of sulfur-containing gases into the atmosphere only from the commissioning of gas cleaning facilities at 53 power units of the country

in the period from 1975 to 1983 decreased from 1.6 to 0.9 million tons. Problems of neutralization of galvanic solutions are poorly solved. Even slower are the issues of disposal of waste generated during the neutralization and processing of spent pickling solutions, chemical production solutions and wastewater. In Russian cities, up to 90% of wastewater is discharged into rivers and reservoirs in an untreated form. Currently, technologies have been developed that make it possible to convert toxic substances into low-toxic and even biologically active substances that can be used in agriculture and other industries.

Modern cities emit about 1000 compounds into the atmosphere and water environment. In urban air pollution, one of the leading places is occupied by motor vehicles. In many cities, exhaust gases account for 30%, and in some - 50%. In Moscow, about 96% CO, 33% NO 2 and 64% hydrocarbons enter the atmosphere due to motor transport.

According to the impact factors, their level, duration of action and distribution area, the natural and technogenic biogeochemical provinces of the Urals are classified as areas with the highest degree of environmental distress (Ermakov V.V., 1999). In recent years, the Ural region has been a leader in terms of total emissions of harmful substances into the atmosphere. According to A.A. Malygina et al., the Urals ranks first in Russia in air and water pollution, and second in soil pollution. According to the State Statistics Committee of Russia, the share of the Sverdlovsk region in the Ural region accounts for 31% of all harmful emissions and the same volume of polluted wastewater. The share of the Chelyabinsk region in the pollution of the region is 25%, Bashkortostan - 20%, Perm region - 18%. Ural enterprises dispose of 400 million tons of toxic waste of all hazard classes.

The Chelyabinsk region is one of the country's largest producers of ferrous metals. It has 28 enterprises of the metallurgical complex. More than 10 mining enterprises operate in the region to provide them with raw materials. As of 1993, the metallurgical enterprises of the region accumulated about 180 million tons of blast-furnace slag, 40 million tons of steel-smelting and more than 20 million tons of ferrochrome production slag, as well as a significant amount of dust and sludge. The possibility of processing waste into various building materials for the needs of the national economy has been established. In the Chelyabinsk region, 3 times more

waste per capita than in Russia as a whole. Over 2.5 billion m 3 of various rocks, 250 million tons of slag and ash from thermal power plants have been accumulated in the dumps of the region. Of the total volume of overburden, only 3% is processed. At metallurgical enterprises, out of 14 million tons of annually formed slags, only 40-42% are used, of which 75% are blast-furnace slags, 4% are steel-smelting, 3% are ferroalloy and 17% non-ferrous metallurgy slags, and only about 1% are TPP ash. According to I.A. Myakishev, 74,736 tons of gaseous and liquid emissions were released into the atmosphere of Chelyabinsk in 1997.

Violation of micro- and macro-elemental homeostasis in the body is determined by natural and technogenic pollution of the biosphere, which leads to the formation of wide areas of technogenic microelementoses around territorial-industrial complexes. The health of not only people directly involved in the production process is suffering, but also those living in the neighborhood of enterprises. As a rule, they have a less pronounced clinical picture and can take a latent form of certain pathological conditions. It is shown that near industrial enterprises located in the city among residential areas, lead concentrations exceed background values ​​by 14-50 times, zinc - by 30-40 times, chromium - by 11-46 times, nickel - by 8-63 times.

Chelyabinsk is one of the 15 cities in Russia with a consistently high level of air pollution and ranks 12th. An analysis of the ecological situation and the state of health of the population of the city of Chelyabinsk made it possible to establish that Chelyabinsk belongs to the "zones of ecological emergency" in terms of the level of pollution. Life expectancy is 4-6 years less compared to similar indicators in Russia (see Fig. 10.6).

Residents living for a long time in conditions of natural and man-made pollution are exposed to abnormal concentrations of chemical elements that have a noticeable effect on the body. One of the manifestations is a change in the composition of the blood, the cause of which is a violation of the intake of iron, microelements (Cu, Co) into the body, associated both with their low content in food, and with a high content in food of compounds that prevent the absorption of iron in the gastrointestinal tract.

When monitoring biological and veterinary parameters in 56 farms in different regions of the Urals (Donnik I.M., Shkuratova I.A., 2001), five variants of territories were conditionally identified, differing in ecological characteristics:

Territories polluted by emissions from large industrial enterprises;

Territories contaminated as a result of the activities of the Mayak Production Association with long-lived radionuclides - strontium-90 and cesium-137 (East Ural radioactive trace - EURT);

Territories experiencing a load from industrial enterprises and at the same time located in the EURTS zone;

Geochemical provinces with a high natural content of heavy metals (Zn, Cu, Ni) in soil, water, as well as anomalous concentrations of radon-222 in the ground air and water;

Territories that are relatively favorable in environmental terms, free from industrial enterprises.

11.2. ECOLOGICAL-ADAPTIVE PRINCIPLE OF SUSTAINABLE DEVELOPMENT OF THE BIOSPHERE

The diversity of soil and water resources in Russia in terms of agrochemical and agrophysical indicators and their pollution with diverse natural and technogenic pollutants is a barrier that prevents the body from providing the body with a balanced micro- and macroelement composition in a biologically active non-toxic form. Geochemical ecology is engaged in the study of the mechanisms of the biological action of micro- and macroelements, as well as toxic applications in medicine, animal husbandry and crop production.

The main task of geochemical ecology is to elucidate the processes of adaptation of organisms to environmental conditions (adaptation), the processes of migration of chemical elements, forms of migration and the influence of technogenic processes, the study of the points of application of chemical elements of the environment to metabolic processes, the identification of causal dependencies of normal and pathological reactions of organisms on environmental factors environment. Under natural conditions and in experiment constitute the ultimate goal of this section of ecology

(Kowalsky V.V., 1991).

Geochemical ecology - This is the area of ​​system ecology, where the main factor of influence is a chemical element and is divided into particular areas according to the object of influence: the geochemical ecology of humans, plants and animals. Modern ecology is an integrating science (Reimers N.F., 1990). He links ecology with 28 natural sciences.

Technogenic pollution of the environment affects the life expectancy of the population. Currently, the birth rate of the population does not always exceed the death rate. In the conditions of the Southern Urals, the mortality rate is 16 per 1000 people (Shepelev V.A., 2006).

The modern stage of the evolution of the biosphere is the stage of correction of human technogenic activity and the beginning of the emergence of intelligent noospheric technologies (Ermakov V.V., 2003). Achieving sustainable development depends, first of all, on the creation and development of environmentally friendly technologies in industry and agriculture. Medicine and agriculture should switch to a strategy of adaptation to the biosphere, according to which it is necessary to take into account the biochemical characteristics of the territory and the basic ecological principles that govern the self-reproduction of living systems. Ecological adaptive principle - the main principle that allows natural ecosystems to maintain their stable state indefinitely, is that the restoration and disposal of waste occurs within the biogeochemical cycle of chemical elements. Since atoms do not arise, do not turn into one another and do not disappear, they can be endlessly used for food purposes, being in a variety of compounds, and their supply will never be depleted. The cycle of elements that existed for centuries included only biogenic elements. However, the extraction from the bowels of the earth in recent decades and the dispersion in the biosphere of chemical elements unusual for living organisms have led to the fact that they are included in biogeochemical cycles involving humans and animals.

Since the United Nations Conference on Environment and Development in Rio de Janeiro in 1992, sustainable development has become a mainstream strategy for national and international development in the field of environmental protection. Sustainable development is a process of change in which the exploitation of resources, the direction of investment, the orientation of technological development must be in harmony with each other to meet the needs of people, both now and in the future. The sustainable development strategy is aimed at meeting the basic needs of people by ensuring economic growth within the ecological boundaries (see the diagram), represented by one of the most important aspects in the field of environmental medicine - the problem of environmental rehabilitation. The first step is to

The main development is the development of specific projects that can develop into a powerful alternative to the current development model. In 2002, an international conference "Sustainable Development of Chelyabinsk and the Region" was held, at which a pilot project on the use of phosphorus-containing metal complexonates was recognized as one of the priorities. The most important step in environmental rehabilitation is the development and implementation of a system for preventing the occurrence of man-made anomalies. Low-waste technologies for the regeneration and disposal of industrial waste, inorganic acids and salts of transition metals using chelating agents for the purification of industrial solutions to obtain metal complexonates for medicine, agriculture and industry; technologies for treating hydrolytic acids, which will reduce the volume of wastewater, solid and gaseous waste, should be widely implemented. These innovations will reduce the volume of wastewater by 2 times, the total salt content by 4-5 times, titanium, iron and aluminum by 10-13 times, magnesium by 5-7 times. Technologies make it possible to obtain rare-earth metals of a high degree of purification (Zholnin A.V. et al., 1990).

The relevance of the problem of human and animal health in connection with the environmental situation is obvious. The solution to this problem is aimed at creating a basis for technological solutions implemented in the form of compact industries, the products of which trigger the compensatory mechanism of natural complexes of individual biological species. This approach makes it possible to exploit the potential

nature through optimal self-regulation, i.e. the only solution to problems is to increase the efficiency of self-defense of the biological system and the natural environment from environmentally hazardous factors by using ready-made technology products that trigger self-defense mechanisms.

The first biospheric studies were carried out by Georges Cuvier (XIX century). He was the first to connect the evolution of the animal world of the Earth with geological catastrophes. This contributed to the formation in the future of ideas about the combination of evolutionary and spasmodic development, as well as biogeochemical unity of the habitat.

niya and living organisms. Despite modern attempts to classify chemical elements, we adhere to the quantitative characteristics given by V.I. Vernadsky and then A.P. Vinogradov. At present, the theory of macro- and microelements has evolved noticeably, and the accumulated knowledge about the properties and biological role of chemical elements is concentrated in a new scientific direction - "elementology", the prototype of which is laid down in bioinorganic chemistry (Zholnin A.V., 2003).

In conditions of ecological trouble, a promising direction is the ecological-adaptive principle, the purpose of which is to correct states of disadaptation using mild adaptogens, antioxidants, immunotropic agents that improve the state of functional systems involved in the biotransformation of elements, detoxification of the body. Prevention and correction of metabolic disorders with the help of phosphorus-containing metal complexonates is very effective (Zholnin A.V., 2006). The digestibility of micro and macro elements increases to 90-95%. The use of micro and macro elements in the form of inorganic compounds is not effective enough, since they are in a biologically inactive form. Their digestibility under these conditions is within 20-30%, as a result of which the body's need for micro- and macroelements is not satisfied even with sufficiently dosed and prolonged use. An analysis of the interaction between the technosphere and the biosphere allows us to consider them together as a single system - the ecosphere, in which all modern socio-, ecological-economic problems are concentrated. The principles of integrity are very important for understanding the problems of modern ecology, the main of which are the endurance of living nature and the dependence of human society on it. Mankind must learn to live in harmony with nature, with its laws, and must be able to predict the impact of the consequences of its activities on biological systems at all levels, including the ecosphere.

Based on the presented brief review of the ecological, biogeochemical situation in Russia, there is no doubt about the need to adopt a new methodological approach to the study of natural and anomalous and man-made pollution of the biosphere, which are different in terms of their entry into the body, toxicity, concentration, forms, duration of action, biochemical reactions. body systems in response to pollutants.

11.3. BIOGEOCHEMICAL PROVINCE

The consequence of technogenesis as a powerful anthropogenic factor reflecting the state of society's technology is the withdrawal (concentration) of some chemical elements (Au, Ag, Pb, Fe) and the dispersion of others (Cd, Hg, As, F, Pb, Al, Cr) in the biosphere or a combination both processes at the same time.

The localization and intensity of the influx of technogenic flows of chemical elements determine the formation man-made anomalies and biogeochemical provinces(BGHP) with varying degrees of environmental tension. Within such territories, under the influence of toxic substances, pathological disorders occur in humans, animals and plants.

In modern conditions of ever-increasing technogenic transformation of nature, the principle of the adequacy of the materials and technologies used for the productivity and resources of the biosphere is of cardinal importance. Biogenic migration of chemical elements is not unlimited. It strives for its maximum manifestation within certain limits corresponding to the homeostasis of the biosphere as the main property of its sustainable development.

The concept of "biogeochemical province" was introduced by Academician A.P. Vinogradov: “Biogeochemical provinces are areas on earth that differ from neighboring areas in terms of the content of chemical elements in them and, as a result, cause a different biological reaction from the local flora and fauna.” As a result of a sharp insufficiency or excess of the content of any element within a given BHCP, biogeochemical endemia- a disease of humans, plants and animals.

Territories within which people, animals and plants are characterized by a certain chemical elemental composition are called biogeochemical provinces.

Biogeochemical provinces are taxa of the biosphere of the third order - territories of various sizes within subregions of the biosphere with constant characteristic reactions of organisms (for example, endemic diseases). Pathological processes caused by deficiency, excess and imbalance of trace elements in the body A.P. Avtsyn (1991) called microelementoses.

The uneven distribution of chemical elements in space is a characteristic property of the geochemical structure of the earth's crust. Significant and stable content deviations

any element in a particular region are called geochemical anomalies.

To characterize the heterogeneity of chemical elements in the earth's crust, V.I. Vernadsky used clarke concentration K to:

where A is the content of the element in the rock, ore, etc.; K medium - the average clarke value of an element in the earth's crust.

The average clarke value of an element in the earth's crust characterizes the so-called geochemical background. If the concentration clarke is greater than one, this indicates enrichment in the element; if less, it means a decrease in its content compared to the data for the earth's crust as a whole. Localities with the same type of anomalies are combined into biogeochemical provinces. Biogeochemical provinces can be both depleted in some element(K to< 1), and enriched with it(Kk > 1).

There are two types of biogeochemical provinces - natural and technogenic. Technogenic provinces are formed as a result of the development of ore deposits, emissions from the metallurgical and chemical industries, and the use of fertilizers in agriculture. Natural biogeochemical provinces are formed as a result of the activity of microorganisms, so it is necessary to pay attention to the role of microorganisms in creating the geochemical features of the environment. Deficiency and excess of elements can lead to the formation of biogeochemical provinces due to both the lack of elements (iodine, fluoride, calcium, copper and other provinces) and their excess (boron, molybdenum, fluoride, nickel, beryllium, copper, etc.). An interesting and important problem is the deficiency of bromine within the continental regions, mountainous regions and the excess of bromine in coastal and volcanic landscapes.

From a biogeochemical point of view, a number of zones of ecological tension can be considered as biogeochemical provinces - local areas of the biosphere - with a sharp change in the chemical elemental composition of the environment and organisms with a violation of local biogeochemical cycles of vital chemical elements, their compounds, associations and the manifestation of pathological specific reactions. The classification of biogeochemical provinces according to the ecological state of the territories is considered in the section.

In accordance with the genesis, BHCPs are subdivided into primary, secondary, natural, natural-technogenic and technogenic, and

torionally, they can be zonal, azonal within a region and a subregion. The ecological analysis of BGCP according to the impact factors and distribution area shows that the following azonal and subregional provinces are the most environmentally unfavorable in Russia:

Polymetallic with dominant associations of Cu-Zn, Cu-Ni, Pb-Zn, Cu-Ni-Co (Southern Urals, Bashkortostan, Chara, Norilsk, Mednogorsk);

Nickel provinces (Norilsk, Monchegorsk, Nikel, Polyarny, Arctic, Tuva);

Lead (Altai, Caucasus, Transbaikalia);

mercury (Altai, Sakha, Kemerovo region);

With an excess of fluorine (Kirovsk, Eastern Transbaikalia, Krasnoyarsk, Bratsk);

Subregional provinces with a high content of boron and beryllium (Southern Urals).

Of the natural and natural-technogenic biogeochemical provinces with an excess of copper, nickel and cobalt in the environment and organisms of animals, a number of local territories of the Urals should be noted. These provinces attracted the attention of scientists as early as the 1950s. Later, the South Ural subregion of the biosphere was studied in more detail. It is singled out as an independent biogeochemical taxon based on the following factors: the presence of heterogeneous metallogenic belts - copper ore and mixed copper ore, enriching soils with microelements such as Cu, Zn, Cd, Ni, Co, Mn, which leads to various body reactions to an excess of these elements , and the geographical position of the subregion of the biosphere, characterized by climatic unity. Exploitation of Cu-Zn and Ni-Co deposits of the sub-region of the biosphere for almost a century has led to the formation of technogenic provinces, which stand out at the level of the current geochemical state of the biosphere.

In this subregion, the Baimak copper-zinc biogeochemical province (Baimak, Sibay), as well as the Yuldybaev and Khalilov Ni-Co-Cu provinces have been identified. In pasture plants of the first province, the concentration of copper and zinc in pasture plants varies between 14-51 (copper) and 36-91 (zinc) mg/kg of dry matter. The content of metals in plants of other provinces is: 10-92 (nickel), 0.6-2.4 (cobalt), 10-43 (copper) mg/kg. In the southern regions of the Chelyabinsk region, the content of selenium in soils and plants

very low (0.01-0.02 mg/kg), therefore, in these areas, the disease of animals with white muscle disease was noted.

In the districts of the Chelyabinsk region (Nagaybaksky, Argayashsky, near the cities of Plast, Kyshtym, Karabash), the content of selenium in soil, water and feed is high - up to 0.4 mg / kg or more (Ermakov V.V., 1999). The concentrations of metals in plants growing in the zone of metallurgical enterprises (Mednogorsk) are apparently more significant. Given the frequent cases of copper and nickel toxicoses among animals (copper jaundice, hypercuprosis, nickel eczematous dermatosis, nickel keratosis, necrosis of the extremities) and biogeochemical criteria for nickel, the considered biogeochemical provinces can be attributed to risk and crisis zones (Ermakov V.V., 1999; Gribovsky G.P., 1995).

In the Urals, there are geochemical anomalies of gold ore zones, characterized by a natural release of salts of heavy metals into soil and water. In these zones, the natural content of arsenic reaches 250 MPC, lead 50 MPC, the content of mercury and chromium in soils is increased. The zone of the Soimanovskaya valley from the city of Miass to the city of Kyshtym, including the city of Karabash, is rich in outcrops of the soil layer of copper, zinc, and lead, reaching over 100 MPC. Outcrops of cobalt, nickel, chromium stretch along the entire region, sometimes creating up to 200 MPC for agricultural soils. Features of natural and technogenic anomalies in the Southern Urals form geochemical provinces on its territory, the elemental composition of which can have a pronounced effect on the elemental composition of drinking water, animals, plants and humans.

The study of technogenic provinces is a new extremely complex scientific problem, the solution of which is necessary for a general ecological assessment of the functioning of the biosphere in the modern era and the search for more rational technologies. The complexity of the problem lies in the need to differentiate technogenic and natural flows and forms of migration of chemical elements, the interaction of technogenic factors, and the manifestation of unforeseen biological reactions in organisms. It should be recalled that it was this scientific direction, along with geochemical ecology, that contributed in our country to the development of the doctrine of micro- and macro-elemental homeostasis and their correction. According to V.I. Vernadsky, the leading factor of the biosphere is chemical - "Approaching geochemically and to the study of geological phenomena, we cover all the nature around us in the same atomic aspect." Under his influence,

a new field of knowledge was born - "geochemical environment and health"

(Kowalsky V.V., 1991).

In the Kartalinsky and Bredinsky districts of the Chelyabinsk region, epidemic osteodystrophy is widespread in cattle, caused by impaired calcium-phosphorus metabolism. The cause of the disease is an excess of strontium, barium and nickel. Elimination of calcium and phosphorus deficiency allows to stop the disease. In the Sosnovsky district of the Chelyabinsk region, cattle were found to be deficient in copper, zinc, manganese and iodine. The biological systems of many territories of the Chelyabinsk region have a high iron content. Accordingly, the biotic concentration of copper, manganese and vitamin E in the animal feed ration increases. Consequently, an excess of iron can lead to the development of a deficiency of these elements in the body with clinical manifestations. For example, the reproductive function of the body is disturbed.

The data obtained show the relevance of zonal mapping of territories according to the biogeochemical principle with the compilation of a database of an ecological portrait of the population, farm animals and plants. The accumulation of statistical knowledge will make it possible to proceed to the implementation of the ecologically adaptive principle, i.e. to the development and implementation of a set of regional measures to eliminate the maladaptation of biological systems in territories of varying degrees of toxic and prooxidant pressure. Such information will be in demand not only by medical institutions, but also by environmental monitoring stations, sanatorium and resort institutions, demographic services, institutes and organizations of the agro-industrial complex.

11.4. ENDEMIC DISEASES

Along with diseases caused by anthropogenic factors of environmental pollution (technogenic), there are diseases associated with the characteristics of biogeochemical provinces (naturally abnormal).

Diseases and syndromes, in the etiology of which the main role is played by the lack of nutrients (essential) elements or an excess of both biogenic and toxic microelements, as well as their imbalance, including abnormal ratios of micro- and macroelements

cops are represented by a working classification of human microelementoses (Table 11.1).

It has been established that in some biogeochemical provinces there is an excess or deficiency of certain microelements, a balanced mineral nutrition of the body is not provided, which leads to the occurrence of diseases in this territory.

Diseases caused by an excess or deficiency of elements in a certain area are called endemic diseases. They are endemic. Symptoms of diseases - hypomicroelementosis - are presented in table. 11.2.

Table 11.1. Human microelementoses

Table 11.2. Typical symptoms of deficiency of chemical elements in the human body

As follows from the table, with a lack of iron in the body, anemia develops, since it is part of the hemoglobin in the blood. The daily intake of this element in the body should be 12 mg. However, an excess of iron causes siderosis of the eyes and lungs, which is associated with the deposition of iron compounds in the tissues of these organs in the Urals in the mountainous regions of Satka. In Armenia, soils have an increased content of molybdenum, so 37% of the population suffers gout. The lack of copper in the body leads to the destruction of blood vessels, pathological growth of bones, defects in the connective tissue. In addition, copper deficiency contributes to cancer in the elderly. Excess copper in the organs (hypermicroelementosis) leads to mental disorders and paralysis of some organs (Wilson's disease). Copper deficiency causes brain disease in children (Menies syndrome), because the brain lacks cytochrome oxidase. In the Urals, iodine deficiency in food - from a lack of iodine develops Graves' disease. In Transbaikalia, China, Korea, the population is affected by deforming arthrosis (Urov's disease). A feature of the disease is softening and curvature of the bones. The soils of these territories have an increased

the content of Sr, Ba and reduced Co, Ca, Cu. The existence of a correlation between a low content of Ca and an increased content of Sr, an analogue of calcium, which is more chemically active, has been established. Therefore, Ca-Sr metabolism in the bone tissue is disturbed in case of Urov's disease. There is an internal redistribution of elements, calcium is displaced by strontium. As a result, strontium rickets develops. The replacement of some elements by others is due to the proximity of their physicochemical characteristics (ion radius, ionization energy, coordination number), the difference in their concentrations and chemical activity. Sodium is replaced by lithium, potassium by rubidium, barium, molybdenum by vanadium. Barium, having the same radius as potassium, competes in biochemical processes. As a result of this interchangeability, hypokalemia develops. Barium ions, penetrating into bone tissue, cause an endemic disease Papping.

11.5. POSSIBLE CASES OF DISTURBANCE OF METAL LIGAND HOMEOSTASIS OF THE ORGANISM

It is typical for an organism to maintain a constant level of concentration of metal ions and ligands, i.e. maintenance of metal-ligand balance (metal-ligand homeostasis). It can be broken for a number of reasons.

First reason. Toxicant ions (Mt) enter the body from the environment (Be, Hg, Co, Te, Pb, Sr, etc.). They form stronger complex compounds with bioligands than biometals. As a result of the higher chemical activity and lower solubility of the compounds formed at the nodes of the crystal lattice, along with calcium hydroxide phosphate Ca 5 (PO 4) 3 OH and instead of it, compounds of other metals similar in properties to calcium (isomorphism) can be precipitated: beryllium, cadmium, barium, strontium. In this competitive complexation for the phosphate ion, they outperform calcium.

The presence of even small concentrations of heavy metals in the environment causes pathological changes in the body. The maximum allowable concentration of cadmium compounds in drinking water is 0.01 mg/l, beryllium - 0.0002 mg/l, mercury - 0.005 mg/l, lead - 0.1 mg/l. Beryllium ions disrupt the process of calcium incorporation into bone tissue, causing it to soften, which leads to berylliosis (beryllium rickets). Replacement of calcium ions

strontium leads to the formation of a less soluble compound Sr 5 (PO 4) 3 OH. The substitution of calcium ions by ions of the radionuclide strontium-90 is especially dangerous. The radionuclide, being included in the bone tissue, becomes an internal source of radiation, which leads to the development of leukemia, sarcoma.

Hg, Pb, Fe ions are soft acids, and form stronger compounds with sulfur ions than biometal ions, which are hard acids. Thus, there is a competition for the -S-H ligand between the toxicant and the microelement. The former wins the competition by blocking the active sites of enzymes and excluding them from metabolic control. The metals Hg, Pb, Bi, Fe and As are called thiol poisons. Arsenic (V) and especially arsenic (III) compounds are very toxic. The chemistry of toxicity can be explained by the ability of arsenic to block the sulfhydryl groups of enzymes and other biologically active compounds.

The second reason. The body receives a microelement necessary for the life of the organism, but in much higher concentrations, which may be due to the characteristics of biogeochemical provinces or the result of unreasonable human activity. For example, to control pests of grapes, drugs are used, the active principle of which is copper ions. As a result, the soil, water and grapes have an increased content of copper ions. An increased content of copper in the body leads to damage to a number of organs (inflammation of the kidneys, liver, myocardial infarction, rheumatism, bronchial asthma). Diseases caused by an increased content of copper in the body are called hypercupremia. Occupational hypercupreosis also occurs. An excess of iron in the body leads to the development of siderosis.

Third reason. Imbalance of trace elements is possible as a result of non-receipt or insufficient intake, which can also be associated with the characteristics of biogeochemical provinces or with production. For example, almost two thirds of the territory of our country are characterized by a lack of iodine, in particular, in mountainous areas, along river valleys, this causes endemic enlargement of the thyroid gland and goiter in humans and animals. Preventive iodization contributes to the prevention of endemics and epizootics.

The lack of fluorine leads to fluorosis. Cobalt ions are deficient in oil production sites.

Fourth reason. Increasing the concentration of toxic particles containing nitrogen, phosphorus, oxygen and sulfur, capable of forming strong bonds with biometal ions (CO, CN - , -SH). There are several ligands in the system and one metal ion capable of forming a complex compound with these ligands. In this case, competing processes are observed - competition between ligands for a metal ion. The process of formation of the most durable complex will prevail. M6L6 + Lt - MbLt + Lb, where Mb is a biogenic metal ion; Lb - bioligand; Lt is a toxic ligand.

The complex forms a ligand with a higher complexing ability. In addition, it is possible to form a mixed-ligand complex, for example, an iron (II) ion in hemoglobin forms a complex with carbon monoxide CO, which is 300 times stronger than a complex with oxygen:

The toxicity of carbon monoxide is explained in terms of competing complexation, the possibility of shifting the ligand-exchange equilibrium.

Fifth reason. Changes in the degree of oxidation of the central atom of a microelement or changes in the conformational structure of the biocomplex, changes in its ability to form hydrogen bonds. For example, the toxic effect of nitrates and nitrites is also manifested in the fact that under their influence hemoglobin is converted into methemoglobin, which is not able to transport oxygen, which leads to hypoxia of the body.

11.6. TOXIC AND NON-TOXIC ELEMENTS. THEIR POSITION IN THE PERIODIC SYSTEM OF D. I. MENDELEEV

Conventionally, elements can be divided into toxic and non-toxic. Toxic elements are chemical elements that have a negative effect on living organisms, which manifests itself only when a certain concentration and form is reached, determined by the nature of the organism. The most toxic elements are located in the periodic system compactly in periods 4.5 and 6 (Table 11.3).

With the exception of Be and Ba, these elements form stable sulfide compounds. Salts of copper, silver, gold interacting with alkali metal sulfides with hydrogen sulfide to form insoluble compounds. The cations of these metals interact with substances that include groups containing sulfur. The toxicity of copper compounds is due to the fact that copper ions interact with sulfhydryl groups -SH (protein binding) and amino groups -NH 2 (protein blocking). In this case, bioclusters of the chelate type are formed. Mercury aminochloride can interact in biological systems with sulfhydryl groups of proteins according to the reaction:

Table 11.3. The position of toxic elements in the periodic system of D. I. Mendeleev

There is an opinion that the main reason for the toxic effect is associated with the blocking of certain functional groups or the displacement of metal ions from some enzymes, such as Cu, Zn. Hg, Pb, Be, Co, Cd, Cr, Ni, which compete with biometals in the process of complexation and can displace them from biocomplexes, are especially toxic and widespread:

where Mb is a biogenic metal ion; Mt - ion of a toxic element; Lb - bioligand.

Toxicity is defined as a measure of any abnormal change in body function due to the action of a chemical agent. Toxicity is a comparative characteristic, this value allows you to compare the toxic properties of various substances (Table 11.4). Biogenic elements ensure the maintenance of the dynamic balance of the vital processes of the organism. Toxic elements, as well as an excess of nutrients, can cause irreversible

changes in dynamic balance in biological systems, leading to the development of pathology.

Table 11.4. Comparative toxicity of metal ions

Elements are distributed unevenly in organs, tissues and cells. It depends on the chemical properties of the element, the route of its entry and the duration of action.

The damaging effect of a substance is manifested at various structural levels: molecular, cellular and at the level of the organism. The most important anomalous effects occur at the molecular level: inhibition of enzymes, irreversible conformational changes in macromolecules and, as a consequence, changes in the rate of metabolism and synthesis, and the occurrence of mutations. Toxic manifestations depend on the concentration and dose of the substance. Doses can be qualitatively subdivided into categories according to the degree of increase in effect:

1) without noticeable effects;

2) stimulation;

3) therapeutic effect;

4) toxic or damaging effect;

5) lethal outcome.

Not all substances can cause stimulation and therapeutic effects. The maximum toxicity is exhibited by the most chemically active particles, coordinatively unsaturated ions, which include ions of free metals. The information accumulated by toxicology convincingly shows that the toxicity of inorganic metal compounds - oxides and salts - is a function of the toxicity of metals in elemental form. Thus, oxidation does not have a decisive effect on toxicity, but only changes its degree to one degree or another. All metal oxides are less toxic than their salts, and with an increase in the toxicity of the element, the difference in the degree of toxicity between oxides and salts decreases. Reducing the electrophilic properties of the ion, respectively, leads to a decrease in its toxic effect on the body.

Chelation of free metal ions with polydentate ligands transforms them into stable, more coordinatively saturated particles, incapable of destroying biocomplexes and, consequently, low toxicity. They are membrane-permeable, capable of being transported and excreted from the body. So, the toxicity of an element is determined by its nature, dose and molecular form, which contains the element. Consequently, there are no toxic elements, only toxic concentrations and forms.

The toxic effect of compounds at different structural levels manifests itself unevenly. Structures in which the cumulation of the element is maximum are subjected to the greatest toxic effect. In this regard, the concepts of critical concentration for a cell and an organ, the critical effect (Yershov Yu.A., Pletneva TV, 1989) were introduced.

Table 11.5. Biogeochemical properties of technogenic environmental pollutants, which are most widely used in production activities (according to A.R. Tairova, A.I. Kuznetsov, 2006)

Note: B - high; U - moderate; H - low.

The critical concentration of an element for a cell is such a minimum concentration, upon reaching which abnormal functional changes occur in the cell - reversible or irreversible. The existence of a critical concentration of a toxic element for a cell is associated with the presence in the cell of a certain reserve of regulation of functions and indicates the existence of cellular homeostasis of the toxic effect of the element in the body.

The critical concentration of an element for an organ is such an average concentration, upon reaching which a violation of its function is observed. The critical concentration for an organ can be much greater or less than the critical concentration for an individual cell. An organ critical for a given element is the first organ in which the element has reached a critical concentration under given conditions (WHO Hygiene Criteria, 1981). In some cases, it is more correct to speak not about an organ, but about a critical system (enzyme, organelle, cell, organ, functional system).

To establish the nature of the dependence of the concentration of the element on the total dose, toxic-kinetic models allow (Filonov A.A., 1973; Soloviev V.N. et al., 1980).

Rice. 11.1. General toxic-kinetic model of the passage of inorganic substances through the body (Yershov Yu.A., Pleteneva T.V., 1989)

Such models reflect the kinetics of the entry of chemical agents into the body, their transformation, absorption and excretion from the body.

(Fig. 11.1).

The toxic effects of some elements are presented in table. 11.6.

Continuation of the table. 11.6Table 11.6. Toxicity effects of some chemical elements

The end of the table. 11.6

Note. The effects of element toxicity should be used when considering the biomedical significance of chemical elements.

Microelementology studies two types of problems. Firstly, these are concentration intervals, forms of microelement compounds and conditions in which a biogenic effect is manifested, the value of which is comparable to the value of vitamins that are not synthesized in the body, but are essential nutrients. With hypomicroelementoses - diseases caused by ME deficiency, deficiency diseases occur. Secondly, the limits of toxicity, the cumulative effects of trace elements as environmental pollutants.

With various forms of contact of organisms with these elements, diseases and intoxication syndromes - toxicopathies occur. The complexity of the problem lies not only in the fact that the manifestations of insufficiency and intoxication are extremely diverse, but also in the fact that essential trace elements themselves, under certain conditions, cause toxic reactions, and pollutants at a certain dose and exposure can be useful. (reverse effect). This is closely related to their mutual influence, which can be both synergistic and antagonistic. Much in microelementology, especially in the problem of ME imbalance in the body, has not yet been sufficiently studied.

11.7. MECHANISMS OF PROTECTION OF THE INTERNAL ENVIRONMENT OF THE ORGANISM FROM XENOBIOTS

Nature has shown great concern for maintaining the metal-ligand homeostasis of the body, for maintaining the purity of the internal environment of the body. Ensuring the removal of waste is sometimes even more important than feeding the cage. Nutrients are delivered by one system - the circulatory system, and waste is removed by two - the circulatory and lymphatic systems. Small "garbage" seems to go straight into the blood, and large - into the lymph. In the lymph nodes, the lymph is cleared of toxic waste.

There are the following mechanisms for protecting the internal environment of the body.

1. Barriers that prevent xenobiotics from entering the internal environment of the body and especially important organs (the brain, genital and some other endocrine glands). These barriers are formed by single or multilayer cell layers. Each cell is covered with a membrane that is impenetrable to many substances. The role of barriers in animals and humans is performed by the skin, the inner surface of the gastrointestinal tract and the respiratory tract. If a xenobiotic penetrates into the blood, then in the central nervous system, endocrine glands, it will be met by histohematic barriers, i.e. barriers between tissue and blood.

2. Transport mechanisms ensure the removal of xenobiotics from the body. They are found in many human organs. The most powerful are in the cells of the liver and renal tubules. Special formations were found in the ventricles of the brain, which move foreign substances from the cerebrospinal fluid (liquid,

washing the brain) into the blood. There are, as it were, two types of excretion of xenobiotics: those that purify the internal environment of the whole organism, and those that maintain the purity of the internal environment of one organ. The principle of operation of the excretion system is the same: transport cells form a layer, one side of which borders on the internal environment of the body, and the other on the external one. The cell membrane does not allow xenobiotics to pass through, but this membrane contains a carrier protein that recognizes a “harmful” substance and transfers it to the external environment. Anions are excreted by one type of carrier, and cations by another. More than two hundred carriers have been described, s-element complexonates are among them. But transport systems are not omnipotent. With a high concentration of poison in the blood, they do not have time to utilize completely toxic particles, and a third defense mechanism comes to the rescue.

3. Enzymatic systems that convert xenobiotics into compounds are less toxic and easier to remove from the body. They catalyze the processes of xenobiotic interaction with molecules of other substances. Interaction products are easily removed from the body. The most powerful enzymatic systems are found in liver cells. In most cases, it can cope with this task and neutralize hazardous substances.

4. Tissue depot, where, as if under arrest, neutralized xenobiotics can accumulate and remain there for a long time. But this is not a means of complete protection against xenobiotics in extreme conditions.

That is why the idea arose to artificially create protection systems similar to the best examples of natural biological systems.

11.8. DEINTOXICATION THERAPY

Detoxification therapy - This is a complex of therapeutic measures aimed at removing the poison from the body or neutralizing the poison with the help of antidotes. Substances that eliminate the effects of poisons on biological structures and inactivate poisons through chemical reactions are called antidotes.

The development of physical and chemical biology has created opportunities for the development and application of various methods for cleansing the body of toxic molecules and ions. Methods used to detoxify the body dialysis, sorption and chemical reactions. Dialysis

referred to as renal methods. In hemodialysis, the blood is separated from the dialysate by a semi-permeable membrane, and toxic particles from the blood passively pass through the membrane into the liquid in accordance with the concentration gradient. Apply compensatory dialysis, vividializ. The essence of compensatory dialysis lies in the fact that the fluid in the dialyzer is washed not with a pure solvent, but with solutions with different concentrations of substances. On the principle of compensation vividiffusion The device was designed and named "artificial kidney" with which you can purify the blood of metabolic products and, therefore, temporarily protect the function of a diseased kidney. An indication for the use of an "artificial kidney" is acute renal failure with uremia after blood transfusion, with burns, toxicosis of pregnancy, etc. Modeling the natural mechanisms of blood detoxification in various sorption devices using carbon sorbents, immunosorbents, ion exchange resins, and others is called hemosorption. It, like its varieties of plasma and lymph sorption, is used to remove various toxic substances, viruses, and bacteria from the blood. Highly specific sorbents for specific metabolites, ions, and toxins have been created. They have a unique ability to remove hydrophobic macromolecular compounds from the body, among which there are many highly toxic and ballast substances (cholesterol, bilirubin, etc.). Sorption methods allow you to influence the immunoreactivity of the body by removing immunoglobulins, complement, antigen-antibody complexes.

Of the sorption methods, enterosorption has found wide application. Enterosorption- a method based on binding and excretion from the gastrointestinal tract with a therapeutic or prophylactic purpose of endogenous and exogenous substances, supramolecular structures and cells. Enterosorbents - medicinal preparations of various structures - carry out the binding of exogenous and endogenous substances in the gastrointestinal tract by adsorption, absorption, ion exchange and complex formation.

Enterosorbents are classified according to their chemical structure: activated carbons, silica gels, zeolites, alumogels, aluminosilicates, oxide and other inorganic sorbents, dietary fiber, organo-mineral and composite sorbents.

Bacterial toxins, bioactive intestinal peptides, toxic metabolites, radionuclides are removed from the body by enterosorption using carbon sorbents or carbon-mineral sorbents with a positively charged surface. Used in complex

therapy of a number of diseases: psoriasis, bronchial asthma, gastrointestinal diseases. Good results were obtained by plasma sorption, which combines two methods of detoxification: hemosorption and plasmapheresis.

One of the most important directions in solving the problem of detoxification of the body is the development and use of artificial cleaning organs: "artificial kidney" and "auxiliary liver". The device "auxiliary liver", developed by Professor V.E. Ryabinin, takes on most of the work on detoxifying the body and improving metabolism. He created a drug made from pork liver, which interacts with the patient's blood through a semi-permeable membrane. The action of the drug is based on the principles of functioning of cytochrome P 450. It retains its functional activity during continuous work in the liver for 6-8 hours. Within an hour after the start of the experiment, up to 84% of ammonia is removed from the blood, and after two hours - 91%. This method can be used for acute and chronic liver diseases, infectious diseases, injuries and burns.

One of the most widely used, affordable and simple method of detoxification is the chemical method. Chemical methods of biotransformation of "harmful" particles for the body are very diverse:

1) neutralization of a toxicant by chemical interaction with it, i.e. direct action on a toxic particle;

2) elimination of the toxic effect by influencing the enzymes, receptors of the body that control the physiological processes of the utilization of toxicants in the body, i.e. indirect effect on the toxicant.

Substances used as detoxifiers make it possible to change the composition, size, charge sign, properties, solubility of a toxic particle, turn it into a low-toxic one, stop its toxic effect on the body, remove it from the body.

Of the chemical methods of detoxification, chelation therapy is widely used, based on the chelation of toxic particles of s-element complexonates. Chelating agents provide detoxification of the body through their direct interaction with the toxicant, the formation of a bound, durable form suitable for transport and excretion from the body. This is the mechanism of detoxification of heavy metal ions by tetacin, trimefacin.

Precipitation reactions are also used for detoxification. The simplest antidote for barium ions, strontium is an aqueous solution of sodium sulfate. Redox reactions also

change for detoxification. With salts of heavy metals, sodium thiosulfate gives poorly soluble sulfides, and it is used as an antidote for heavy metal poisoning:

The thiosulfate ion donates a sulfur atom to the cyanide ion, thereby converting it into a non-toxic rhodanide ion:

As an antidote for heavy metal compounds, aqueous solutions of sodium sulfide, the so-called alkaline hydrogen sulfide drink, are also used. As a result of the formation of poorly soluble compounds, toxic ions are isolated and excreted from the gastrointestinal tract. In case of hydrogen sulfide poisoning, the victim is allowed to breathe moistened bleach, from which a small amount of chlorine is released. In case of bromine poisoning, ammonia vapors are inhaled.

Destructive for proteins are biotransformations associated with the action of strong oxidizing agents, which convert sulfur compounds to an oxidation state of +6. Oxidizing agents such as, for example, hydrogen peroxide, oxidize disulfide bridges and sulfhydryl groups of proteins into sulfo groups R-SO 3 H, which means their denaturation. Radiation damage to cells changes their redox potential. To maintain the potential as a radioprotector - a drug that protects the body from radiation damage - p-mercaptoethylamine (mercamin) is used, the oxidation of which with active oxygen forms during the radiolysis of water leads to the formation of cystamine:

The sulfide group can participate in hemolytic processes with the formation of low-reactive R-S radicals. This property of mercamin also serves as protection against the action of free radical particles - products of water radiolysis. Consequently, the balance of thiol disulfide is associated with the regulation of the activity of enzymes and hormones, the adaptation of tissues to the action of oxidizing agents, reducing agents and radical particles.

In the intensive care of endotoxicosis, chemical methods (protectors, antidotes) and efferent methods are used together.

detoxification - plasmapheresis with indirect electrochemical oxidation of blood and plasma. This set of methods underlies the design of the "liver-kidney" apparatus, which is already being used in the clinic.

11.9. QUESTIONS AND TASKS FOR SELF-CHECKING OF PREPAREDNESS FOR LESSONS AND EXAMS

1. Give the concept of biogeochemical provinces.

2. What is the basis for the use of s-element complexonates as therapeutic drugs for poisoning with heavy metal compounds?

3. Physical and chemical bases of biotoxic action (Pb, Hg, Cd, nitrites and nitrosamines).

4. The mechanism of the toxic action of heavy metal ions based on the theory of hard and soft acids and bases.

5. Principles of chelation therapy.

6. Detoxification preparations for chelation therapy.

7. What properties of nitrogen compounds determine their toxic effect on the body?

8. What properties of hydrogen peroxide determine its toxic effect?

9. Why are thiol-containing enzymes irreversibly "poisoned" by Cu 2+, Ag + ions?

10. What is the possible chemistry of the antitoxic action of Na 2 S 2 O 3 5H 2 O in case of poisoning with compounds of mercury, lead, hydrocyanic acid?

11. Give a definition of geochemical ecology, an ecological portrait of a person.

11.10. TESTS

1. In case of heavy metal poisoning, methods are used:

a) enterosorption;

b) chelation therapy;

c) precipitation;

2. A substance may manifest its toxic nature by:

a) the form of receipt;

b) concentration;

c) the presence of other substances in the body;

d) All of the above answers are correct.

3. The average concentration at which a violation of the function of an organ is observed is called:

a) the maximum allowable concentration;

b) mortality index;

c) critical concentration;

d) biotic concentration.

4. Substances that cause the development of cancerous tumors are called:

a) strumogens;

b) mutagens;

c) carcinogens;

d) teratogens.

5. Molybdenum compounds are substances:

a) highly toxic;

b) moderate toxicity;

c) low toxicity;

d) do not show toxic properties.

6. Graves' disease is:

a) hypermacroelementosis;

b) hypermicroelementosis;

c) hypomacroelementosis;

d) hypomicroelementosis.

7. Hydrogen peroxide converts sulfur amino acids into sulfur:

a)-1;

b) 0;

General chemistry: textbook / A. V. Zholnin; ed. V. A. Popkova, A. V. Zholnina. - 2012. - 400 p.: ill.

In the 1980s and 1990s, environmental issues were widely discussed by scientists, politicians and in the media. Much attention was given to global and regional issues such as carbon dioxide (CO 2 ) emissions associated with global warming and stratospheric ozone depletion due to chlorofluorocarbon (CFC) emissions. However, problems of local importance were considered no less seriously, since their consequences are more obvious and immediate. Issues related to the pollution of water resources by leaching products coming from landfills and the formation of radon in residential buildings are now the property of not only a few narrow specialists, but also the concern of a wide range of the population. It should be noted that many of these problems require an understanding of the mechanisms of chemical reactions, and therefore environmental chemistry is becoming a particularly important and relevant discipline.

Environmental chemistry is currently becoming one of the leading disciplines due to the ever-increasing impact of anthropogenic chemical compounds on the environment. This course outlines the basic principles required for the study of environmental chemistry and shows how these principles are applied on local and global scales and how the effect of geochemical processes is manifested on a time scale.

The goal of the Chemical Foundations of Ecology course is to introduce students to some of the fundamental chemical principles that are used in environmental chemistry and to illustrate their application in various situations, both globally and regionally.

The main idea of ​​this course is the need to understand how natural geochemical processes occur and how they acted on various time scales. This understanding provides basic information on the basis of which it is possible to quantify the consequences of human intervention in chemical processes. The course does not attempt to provide an exhaustive overview, but includes topics covering fundamental chemical principles.

Explanatory note

The program "Chemical Foundations of Ecology" is a modified one (Shustov S.B., Shustova L.V. "Chemistry and Ecology", Nizhny Novgorod, 1994, Nizhny Novgorod Humanitarian Center). The program promotes the integration of natural sciences and humanities, strengthens the system of environmental knowledge.

The program can be implemented in the curriculum of grades 9-11, involves the removal of unreasonable prejudices against chemistry as the “main culprit” of environmental ills, an assessment of its positive role in the modern solution of environmental problems, the formation of an optimistic view of the future and faith in the human mind.

Target

Lay the foundations for the perception of the basic course of chemistry from the standpoint of environmental issues, develop natural science knowledge, and introduce students to the vision of the chemical aspects of ecology.

Tasks

1. Development of cognitive interest in environmental problems.

2. Development of personal self-education.

3. Creation of a comfortable environment, an atmosphere of cooperation.

4. Formation of public activity on environmental issues.

5. Formation of special knowledge and skills.

Expected results

Students should rethink the foundations of the basic course of chemistry from the standpoint of environmental issues, correct the stereotype of attitude towards chemistry as the “main culprit” of environmental problems. The implementation of the program will provide an opportunity to influence the formation of life principles among high school students based on the cooperation of man with nature, the upbringing of a responsible attitude towards nature.

In addition, a comfortable, favorable environment and an atmosphere of cooperation in the classroom contributes to self-education.

Methods for testing knowledge, skills, and frequency

Starting, intermediate and final testing.

Introduction. 2 hours (1+1)

Chemistry is the science of substances and their transformations. Ecology is a science that studies the relationship of organisms between themselves and the environment. The relationship of chemistry and ecology, their role in the knowledge of the surrounding world. Nature protection is a set of measures for the protection and conservation of natural objects and the rational use of natural resources. The dual role of man in the environment.

Practical part. Interviewing (survey) school students in order to identify their attitude to nature and its protection and comparing their answers with their personal attitude to the problem.

Topic number 1. The most important chemical concepts. 3 hours (2+1)

Chemical substances and chemical reactions. Simple and complex substances. Main classes of substances. Graphic representation of substances. Equations of chemical reactions. Familiarity with safety precautions when working in a chemical laboratory.

Practical part. Comparison of physical phenomena and chemical reactions. Demonstration of changing the color of indicators in various environments.

Topic number 2. Basic ecological concepts. 4h. (3+1)

Ecological filters. Organism, Food chains. The concept of MPC. Ecological pyramid of numbers and masses. Biosphere. Noosphere. Levels of environmental problems: local, regional, global. Ecological crisis.

Practical part. Determining the level of environmental problems.

Topic number 3. The human body is a chemical laboratory. 4 hours (3+1)

Chemical organization of organisms. The concept of organic substances: proteins, fats, carbohydrates, nucleic acids, hormones, vitamins. Inorganic substances: water, salts of sodium, potassium, calcium. Compounds of iron, copper, cobalt, phosphorus and their biorol. Causes of rapid aging of the body. Orthobiosis is a healthy lifestyle.

Practical part. Familiarization with the composition of tooth enamel and dentin. Causes of caries.

Topic № 4. Earth's atmosphere and its protection. 4 hours (2+2)

The atmosphere is the air environment. Air and its components. Composition of inhaled and exhaled air. Air hygiene. Harm to human health by smoking. Causes of the greenhouse effect, the destruction of the ozone layer and possible consequences. Atmospheric protection. Ecological clean fuels. Alternative energy sources.

Practical part. Game: "If I were a mayor..." Project competition: "Clean transport modes of the 21st century".

Topic number 5. Hydrosphere and its protection. 4 hours (2+2)

Water, its composition and properties. The hydrosphere is the aquatic habitat of organisms. The main sources and ways of pollution of water bodies: extraction and transportation of oil, coal, ores, industrial, agricultural and domestic effluents. The problem of scarcity of fresh water and its solution.

Practical part. 1. Simulation game: "Operational meeting" (problem: oil in the sea). 2. Environmental forecasting. Assessment of the situation: drivers wash cars on the shore of a reservoir. Development of a project for an environmentally friendly site for washing cars.

Topic number 6. Lithosphere and its protection. 4 hours (2+2)

Lithosphere and its boundaries. Soil and its functions. Soil pollution with heavy metals (sources, consequences, protection). The accumulation of pesticides in the soil is a chemical means of controlling weeds and plant diseases. The impact of pesticides on the natural environment. Alternative methods of pest control. The problem of urban and industrial landfills and ways to solve it.

Practical part. Round table "Pesticides and the environment". Drawing up a memo to the summer resident.

Topic number 7. Chemistry at home. 4 hours (2+2)

The main substances used in everyday life, their properties. Safety precautions when handling household chemicals. First aid for chemical poisoning and burns. Ethanol (composition, properties, dual role in relation to humans)

Practical part. 1. Acquaintance with the main groups of substances used in everyday life. Home Safety Contest. 2. Discussion: Ethanol: facts for and against.

Topic number 8. The earth is our common home. 4 hours (2+2)

Cycle of substances in the biosphere. The abundance of elements in the earth's crust. The concept of methods for controlling the flow of metals into plant and animal organisms. Xentobiotics are substances that are not characteristic of living organisms (cosmetics, aerosols). Ecopoisoning. Allergy as a result of environmental poisoning. Ways to preserve the purity of the biosphere. The role of ecology, chemistry in solving environmental problems.

The program is designed for 34 hours, of which - 20 hours of theory, 14 hours of practice.

Educational and thematic plan

No. p / p

Title of sections, topic

Number of hours

Total

theory

practice

Introduction

The most important chemical concepts

Earth's atmosphere and its protection

Hydrosphere and its protection

Lithosphere and its protection

Chemistry at home

Earth is our common home

TOTAL:

34

20

14

Methodological support

Theme

Form of occupation

Techniques, methods

Methodological and didactic materials

Technical equipment

Summing up form

Introduction

group work

Interviewing

group task

Conversation

Cards

Summarizing

interviewing

The most important chemical concepts

Practical lesson

Group tasks

tables

Scheme

Solutions of acids, alkalis, salts and various indicators

abstract

Basic ecological concepts

group

Individual

Practical

Lecture

Conversation

Slides

tables

Screen

Presentation

The human body is a chemical laboratory

group

Practical

Lecture

Didactic cards

Practical work

tables

Scheme

Didactic cards

Report

Hydrosphere and its protection

Group work Simulation game Prediction Simulation

Group and individual tasks Conversation

Didactic cards Tables Slides

Screen

simulation game

Lithosphere and its protection

Group work Round table

Lecture Conversation Individual tasks

Didactic flashcards Video

Video recorder

Round table Drawing up a memo to the summer resident

Atmosphere and its protection

Group work Individual work

The game

Lecture Creative tasks Group tasks

tables

Scheme

Slides

Screen

Competition

projects

Chemistry at home

Practical tasks Discussion

Individual tasks Group tasks Conversation

Didactic cards

Substances used in everyday life

Discussion "Ethanol: pros and cons"

Earth is our common home

Group lessons Practical class Conference

Lecture

Conversation

Group tasks

tables

Scheme

slides

Screen

Conference "Chemistry and Ecology"

Bibliography

Shustov S. B., Shustova L. V. Chemistry and ecology. Textbook for students. N. Novgorod, 1994 Nizhny Novgorod Humanitarian Center.

E. Grosse, H. Weissmantel. Chemistry for the Curious. Leningrad, "Chemistry", 1985

V.I. Golik, V.I. Komashchenko, K. Drebenstedt. Environmental protection. Moscow, 2005

A.F. Sergeeva. Harvest without chemistry or ecology of six acres. Rostov-Phoenix, 2001

G.P. Polyashov. Treatment without chemicals. Proven traditional medicine. Golden book of folk medicine. EXMO, 2005

Today there is no need to convince anyone of the great importance for all mankind of issues related to the problem of environmental protection. This problem is complex and multifaceted. It includes not only purely scientific aspects, but also economic, social, political, legal, aesthetic ones.

The processes that determine the current state of the biosphere are based on chemical transformations of substances. Chemical aspects of the problem of environmental protection form a new branch of modern chemistry, called chemical ecology. This direction considers the chemical processes occurring in the biosphere, chemical pollution of the environment and its impact on the ecological balance, characterizes the main chemical pollutants and methods for determining the level of pollution, develops physical and chemical methods to combat environmental pollution, and searches for new environmentally friendly energy sources. and etc.

Understanding the essence of the problem of environmental protection, of course, requires familiarity with a number of preliminary concepts, definitions, judgments, a detailed study of which should contribute not only to deeper insight into the essence of the problem, but also to the development of environmental education. .Geological spheres of the planet, as well as the structure of the biosphere and the chemical processes occurring in it are summarized in Scheme 1.

Usually there are several geospheres. The lithosphere is the outer solid shell of the Earth, consisting of two layers: the upper one, formed by sedimentary rocks, including granite, and the lower one, basalt. The hydrosphere is all the oceans and seas (World Ocean), which make up 71% of the Earth's surface, as well as lakes and rivers. The depth of the ocean averages 4 km, and in some depressions - up to 11 km. Atmosphere - a layer above the surface of the lithosphere and hydrosphere, reaching 100 km. The lower layer of the atmosphere (15 km) is called the troposphere. It includes water vapor suspended in the air, moving with uneven heating of the planet's surface. The stratosphere extends above the troposphere, at the borders of which the northern lights appear. In the stratosphere, at an altitude of 45 km, there is an ozone layer that reflects cosmic radiation that is harmful to life and, in part, ultraviolet rays. Above the stratosphere extends the ionosphere - a layer of rarefied gas from ionized atoms.

Among all the spheres of the Earth, the biosphere occupies a special place. The biosphere is the geological shell of the Earth, together with the living organisms inhabiting it: microorganisms, plants, animals. It includes the upper part of the lithosphere, the entire hydrosphere, the troposphere, and the lower part of the stratosphere (including the ozone layer). The boundaries of the biosphere are determined by the upper limit of life, limited by the intense concentration of ultraviolet rays, and the lower limit, limited by the high temperatures of the earth's interior; the extreme limits of the biosphere reach only lower organisms - bacteria. occupies a special place in the biosphere ozone protective layer. The atmosphere contains only about. % of ozone, however, he created such conditions on Earth, thanks to which life originated and continues to develop on our planet.

In the biosphere, continuous cycles of substances and energy are carried out. Basically the same elements are constantly involved in the cycle of matter: hydrogen, carbon, nitrogen, oxygen, sulfur. From inanimate nature, they pass into the composition of plants, from plants - into animals and humans. The atoms of these elements are kept in the circle of life for hundreds of millions of years, which is confirmed by isotopic analysis data. These five elements are called biophilic (life-loving), while not all of their isotopes, but only light ones. So, of the three isotopes of hydrogen, only is biophilic. Of the three natural isotopes of oxygen biophilic only, and from carbon isotopes - only.

The role of carbon in the origin of life on Earth is truly enormous. There are reasons to believe that during the formation of the earth's crust, part of the carbon entered into its deep layers in the form of minerals such as carbides, while the other part was retained by the atmosphere in the form of CO. The decrease in temperature at certain stages of the formation of the planet was accompanied by the interaction of CO with water vapor by the kcal reaction, so that by the time liquid water appeared on Earth, atmospheric carbon should have been in the form of carbon dioxide. In accordance with the scheme of the carbon cycle below, atmospheric carbon dioxide is extracted by plants (1), and carbon enters the body of animals through food links (2):

The respiration of animals and plants and the smoldering of their remains constantly return huge masses of carbon to the atmosphere and ocean waters in the form of carbon dioxide (3, 4). At the same time, there is some removal of carbon from the cycle due to the partial mineralization of the remains of plants (5) and animals (6).

An additional, and more powerful, removal of carbon from the circulation is the inorganic process of weathering of rocks (7), in which the metals contained in them under the influence of the atmosphere turn into carbonic salts, which are then washed out by water and carried by rivers to the ocean, followed by partial sedimentation. According to rough estimates, up to 2 billion tons of carbon are bound annually during the weathering of rocks from the atmosphere. Such a grandiose consumption cannot be compensated by various free-flowing natural processes (volcanic eruptions, gas sources, the action of limestone formed during thunderstorms, etc.), leading to the reverse transition of carbon from minerals into the atmosphere (8). Thus, both the inorganic and organic stages of the carbon cycle are aimed at reducing the content in the atmosphere. In this regard, it should be noted that conscious human activity significantly affects the overall carbon cycle and, affecting essentially all areas of the processes occurring during the natural cycle, ultimately compensates for the leakage from the atmosphere. Suffice it to say that due to the combustion of only one coal, the atmosphere annually (in the middle of our century) returned in the form of more than 1 billion tons of carbon. Taking into account the consumption of other types of fossil fuels (peat, oil, etc.), as well as a number of industrial processes leading to the release, it can be assumed that this figure is actually even higher.

Thus, the influence of man on the cycles of carbon transformations in its direction is directly opposite to the total result of the natural cycle:

The energy balance of the Earth is composed of various sources, but the most important of them are solar and radioactive energy. During the evolution of the Earth, radioactive decay was intense, and 3 billion years ago there was 20 times more radioactive heat than now. At present, the heat of the sun's rays falling on the Earth greatly exceeds the internal heat from radioactive decay, so that the main source of heat can now be considered the energy of the Sun. The sun gives us kcal of heat per year. According to the diagram above, 40% of solar energy is reflected by the Earth into the world space, 60% is absorbed by the atmosphere and soil. Part of this energy is spent on photosynthesis, part goes to the oxidation of organic substances, and part is conserved in coal, oil, and peat. Solar energy excites on the Earth climatic, geological and biological processes of grandiose scales. Under the influence of the biosphere, solar energy is converted into various forms of energy, which cause huge transformations, migrations, and the circulation of substances. Despite its grandiosity, the biosphere is an open system, as it constantly receives a stream of solar energy.

Photosynthesis includes a complex set of reactions of different nature. In this process, the bonds in the molecules and are rearranged, so that instead of the previous carbon-oxygen and hydrogen-oxygen bonds, a new type of chemical bonds arises: carbon-hydrogen and carbon-carbon:

As a result of these transformations, a carbohydrate molecule appears, which is a concentrate of energy in the cell. Thus, chemically, the essence of photosynthesis lies in the rearrangement of chemical bonds. From this point of view, photosynthesis can be called the process of synthesis of organic compounds, which is due to light energy. The overall photosynthesis equation shows that, in addition to carbohydrates, oxygen is also formed:

but this equation does not give an idea of ​​its mechanism. Photosynthesis is a complex, multi-stage process in which, from a biochemical point of view, the central role belongs to chlorophyll, a green organic substance that absorbs a quantum of solar energy. The mechanism of photosynthesis processes can be represented by the following scheme:

As can be seen from the diagram, in the light phase of photosynthesis, the excess energy of "excited" electrons generates for the process: photolysis - with the formation of molecular oxygen and atomic hydrogen:

and the synthesis of adenosine triphosphoric acid (ATP) from adenosine diphosphoric acid (ADP) and phosphoric acid (P). In the dark phase, the synthesis of carbohydrates takes place, for the implementation of which the energy of ATP and hydrogen atoms is consumed, which appear in the light phase as a result of the conversion of the light energy of the Sun. The total productivity of photosynthesis is enormous: every year the Earth's vegetation sequesters 170 billion tons of carbon. In addition, plants involve billions of tons of phosphorus, sulfur and other elements in the synthesis, as a result of which about 400 billion tons of organic substances are synthesized annually. Nevertheless, for all its grandiosity, natural photosynthesis is a slow and inefficient process, since a green leaf uses only 1% of the solar energy incident on it for photosynthesis.

As noted above, as a result of the absorption of carbon dioxide and its further transformations during photosynthesis, a carbohydrate molecule is formed, which serves as a carbon skeleton for building all organic compounds in the cell. Organic substances that have arisen in the process of photosynthesis are characterized by a high supply of internal energy. But the energy accumulated in the final products of photosynthesis is not available for direct use in chemical reactions occurring in living organisms. The transfer of this potential energy into an active form is carried out in another biochemical process - respiration. The main chemical reaction of the process of respiration is the absorption of oxygen and the release of carbon dioxide:

However, the breathing process is very complex. It includes the activation of hydrogen atoms of an organic substrate, the release and mobilization of energy in the form of ATP, and the generation of carbon skeletons. In the process of respiration, carbohydrates, fats and proteins in the reactions of biological oxidation and the gradual restructuring of the organic skeleton give up their hydrogen atoms with the formation of reduced forms. The latter, when oxidized in the respiratory chain, release energy, which is accumulated in an active form in coupled reactions of ATP synthesis. Thus, photosynthesis and respiration are different, but very closely related aspects of the overall energy exchange. In the cells of green plants, the processes of photosynthesis and respiration are closely linked. The process of respiration in them, as in all other living cells, is ongoing. During the day, along with respiration, photosynthesis occurs in them: plant cells convert light energy into chemical energy, synthesizing organic matter, and releasing oxygen as a by-product of the reaction. The amount of oxygen released by a plant cell during photosynthesis is 20-30 times greater than its absorption in the simultaneous respiration process. Thus, during the day, when both processes are going on in plants, the air is enriched with oxygen, and at night, when photosynthesis stops, only the respiration process is preserved.

The oxygen necessary for breathing enters the human body through the lungs, whose thin and moist walls have a large surface (about 90) and are permeated with blood vessels. Getting into them, oxygen forms with hemoglobin enclosed in red blood cells - erythrocytes - a fragile chemical compound - oxyhemoglobin, and in this form it is carried by red arterial blood to all tissues of the body. In them, oxygen is split off from hemoglobin and is included in various metabolic processes, in particular, it oxidizes organic substances that have entered the body in the form of food. In tissues, carbon dioxide joins hemoglobin, forming a fragile compound - carbhemoglobin. In this form, and also partially in the form of salts of carbonic acid and in a physically dissolved form, carbon dioxide with a current of dark venous blood enters the lungs, where it is excreted from the body. Schematically, this process of gas exchange in the human body can be represented by the following reactions:

Typically, air inhaled by a person contains 21% (by volume) and 0.03%, and exhaled - 16% and 4%; per day a person exhales 0.5. Similar to oxygen, carbon monoxide (CO) reacts with hemoglobin, and the resulting compound is Heme. CO is much more durable. Therefore, even at low concentrations of CO in the air, a significant part of hemoglobin is associated with it and ceases to participate in the transfer of oxygen. When the content in the air is 0.1% CO (by volume), i.e. at a ratio of CO and 1: 200, hemoglobin binds equal amounts of both gases. Because of this, when inhaling air poisoned with carbon monoxide, death from suffocation can occur, despite the presence of excess oxygen.

Fermentation as a process of decomposition of sugary substances in the presence of a special kind of microorganisms occurs so often in nature that alcohol, although in negligible quantities, is a constant component of soil water, and vapors: it is always contained in small quantities in the air. The simplest fermentation scheme can be represented by the equation:

Although the mechanism of fermentation processes is complex, it can still be argued that phosphoric acid derivatives (ATP), as well as a number of enzymes, play an extremely important role in it.

Decay is a complex biochemical process, as a result of which excrement, corpses, plant remains return to the soil the bound nitrogen previously taken from it. Under the influence of special bacteria, this bound nitrogen eventually passes into ammonia and ammonium salts. In addition, during decay, part of the bound nitrogen passes into free nitrogen and is lost.

As follows from the diagram above, part of the solar energy absorbed by our planet is "conserved" in the form of peat, oil, coal. Powerful shifts of the earth's crust buried huge plant masses under layers of rocks. During the decomposition of dead plant organisms without access to air, volatile decay products are released from them, and the residue is gradually enriched with carbon. This has a corresponding effect on the chemical composition and calorific value of the decomposition product, which, depending on its characteristics, is called peat, brown and black coal (anthracite). Like plant life, animal life of past eras also left us a valuable legacy - oil. Modern oceans and seas contain huge accumulations of protozoa in the upper layers of the water to a depth of about 200 m (plankton) and in the near-bottom region of not very deep places (benthos). The total mass of plankton and benthos is estimated at a huge figure (~ t). Being the basis of nutrition for all more complex marine organisms, plankton and benthos are now unlikely to accumulate as remains. However, in distant geological epochs, when the conditions for their development were more favorable, and there were much fewer consumers than now, the remains of plankton and benthos, and also, possibly, of more highly organized animals that died in masses due to various reasons, could become the main building material for the formation of oil. Crude oil is a black or brown oily liquid insoluble in water. It consists of 83-87% carbon, 10-14% hydrogen and small amounts of nitrogen, oxygen and sulfur. Its calorific value is higher than that of anthracite and is estimated at 11,000 kcal/kg.

Biomass is understood as the totality of all living organisms of the biosphere, i.e. the amount of organic matter and the energy contained in it of the entire population of individuals. Biomass is usually expressed in weight units in terms of dry matter per unit area or volume. The accumulation of biomass is determined by the vital activity of green plants. In biogeocenoses, they, as producers of living matter, play the role of "producers", herbivorous and carnivorous animals, as consumers of living organic matter, play the role of "consumers", and the destroyers of organic residues (microorganisms), bringing the decay of organic matter to simple mineral compounds, - "reducers". A special energy characteristic of biomass is its ability to reproduce. By definition, V.I. Vernadsky, "living matter (a set of organisms), like a mass of gas, spreads over the earth's surface and exerts a certain pressure in the environment, bypasses obstacles that impede its progress, or takes possession of them, covers them. This movement is achieved through the reproduction of organisms." On the land surface, the increase in biomass occurs in the direction from the poles to the equator. In the same direction, the number of species participating in biogeocenoses also increases (see below). Soil biocenoses cover the entire land surface.

Soil is a loose surface layer of the earth's crust, modified by the atmosphere and organisms and constantly replenished with organic residues. The thickness of the soil, along with the surface biomass and under its influence, increases from the poles to the equator. The soil is densely populated by living organisms, and continuous gas exchange takes place in it. At night, when cooling and compressing gases, a certain amount of air penetrates into it. Air oxygen is absorbed by animals and plants and is part of chemical compounds. Nitrogen that enters the air is captured by some bacteria. During the day, when the soil is heated, ammonia, hydrogen sulfide and carbon dioxide are released from it. All processes occurring in the soil are included in the cycle of substances in the biosphere.

Earth's hydrosphere, or World Ocean, occupies more than 2/3 of the planet's surface. The physical properties and chemical composition of the ocean waters are very constant and create an environment conducive to life. Aquatic animals excrete during respiration, and algae enrich the water during photosynthesis. Photosynthesis of algae occurs mainly in the upper layer of water - at a depth of up to 100 m. The plankton of the ocean accounts for 1/3 of the photosynthesis that occurs on the entire planet. Biomass is mostly dispersed in the ocean. On average, the biomass on Earth, according to modern data, is approximately t, the mass of green land plants is 97%, animals and microorganisms are 3%. In the oceans, living biomass is 1000 times less than on land. The use of solar energy on the ocean area - 0.04%, on land - 0.1%. The ocean is not as rich in life as it was assumed until recently.

Humanity makes up only a small part of the biomass of the biosphere. However, having mastered various forms of energy - mechanical, electrical, atomic - it began to exert a tremendous influence on the processes occurring in the biosphere. Human activity has become such a powerful force that this force has become commensurate with the natural forces of nature. An analysis of the results of human activity, the impact of this activity on the biosphere as a whole, led academician V.I. Vernadsky to the conclusion that at present humanity has created a new shell of the Earth - "intelligent". Vernadsky called it "noosphere". The noosphere is "the collective mind of man, concentrated both in its potentialities and in the kinetic effects on the biosphere. These effects, however, for centuries were of a spontaneous, and sometimes predatory nature, and the consequence of such an impact was threatening environmental pollution, with all the ensuing consequences."

Consideration of issues related to the problem of environmental protection requires clarification of the concept " environment". This term refers to our entire planet plus a thin shell of life - the biosphere, plus outer space that surrounds us and affects us. However, often, for simplicity, the environment means only the biosphere and part of our planet - the earth's crust. According to V.I. Vernadsky, the biosphere is “the area of ​​existence of living matter.” Living matter is the totality of all living organisms, including man.

Ecology as the science of the relationships between organisms, as well as between organisms and the environment, pays special attention to the study of those complex systems (ecosystems) that arise in nature based on the interaction of organisms with each other and the inorganic environment. Hence, an ecosystem is a set of living and non-living components of nature that are in interaction. This concept is applied to units of various lengths - from an anthill (microecosystem) to an ocean (macroecosystem). The biosphere itself is a gigantic ecosystem of the globe.

The connections between the components of the ecosystem arise primarily on the basis of food connections and ways of obtaining energy. According to the method of obtaining and using nutrient materials and energy, all organisms of the biosphere are divided into two sharply different groups: autotrophs and heterophores. Autotrophs are able to synthesize organic substances from inorganic compounds (, etc.). From these energy-poor compounds, cells synthesize glucose, amino acids, and then more complex organic compounds - carbohydrates, proteins, etc. The main autotrophs on Earth are the cells of green plants, as well as some microorganisms. Heterotrophs are not able to synthesize organic substances from inorganic compounds. They need the delivery of ready-made organic compounds. Heterotrophs are the cells of animals, humans, most microorganisms and some plants (for example, fungi and green plants that do not contain chlorophyll). In the process of feeding, heterotrophs ultimately decompose organic matter to carbon dioxide, water, and mineral salts, i.e. substances suitable for reuse by autotrophs.

Thus, a continuous circulation of substances occurs in nature: the chemicals necessary for life are extracted by autotrophs from the environment and returned to it through a number of heterotrophs. This process requires a constant supply of energy from outside. Its source is the radiant energy of the sun. The movement of matter caused by the activity of organisms occurs cyclically, and it can be used again and again, while energy in these processes is represented by a unidirectional flow. The energy of the Sun is only transformed by organisms into other forms - chemical, mechanical, thermal. In accordance with the laws of thermodynamics, such transformations are always accompanied by the dissipation of part of the energy in the form of heat. Although the general scheme of the circulation of substances is relatively simple, in real conditions of nature this process takes on very complex forms. Not a single type of heterotrophic organisms is able to immediately break down the organic matter of plants to final mineral products (, etc.). Each species uses only a part of the energy contained in organic matter, bringing its decay to a certain stage. Remains unsuitable for this species, but still rich in energy, are used by other organisms. Thus, in the process of evolution, chains of interconnected species have developed in the ecosystem, successively extracting materials and energy from the original food substance. All species that make up the food chain subsist on the organic matter generated by green plants.

In total, only 1% of the radiant energy of the Sun falling on plants is converted into the energy of synthesized organic substances that can be used by heterotrophic organisms. Most of the energy contained in plant foods is spent in the animal body on various life processes and, turning into heat, is dissipated. At the same time, only 10-20% of this food energy goes directly to the construction of a new substance. Large losses of useful energy predetermine the fact that food chains consist of a small number of links (3-5). In other words, as a result of energy losses, the amount of organic matter formed at each subsequent level of food chains decreases sharply. This important rule is called ecological pyramid rule and on the diagram it is represented by a pyramid, in which each subsequent level corresponds to a plane parallel to the base of the pyramid. There are different categories of ecological pyramids: the pyramid of numbers - reflecting the number of individuals at each level of the food chain, the pyramid of biomass - reflecting the amount of organic matter, respectively, the pyramid of energy - reflecting the amount of energy in food.

Any ecosystem consists of two components. One of them is organic, representing a complex of species that form a self-sustaining system in which the circulation of substances is carried out, which is called biocenosis, the other is an inorganic component that gives shelter to biocenosis and is called bioton:

Ecosystem = bioton + biocenosis.

Other ecosystems, as well as geological, climatic, cosmic influences in relation to this ecological system act as external forces. The stability of an ecosystem is always associated with its development. According to modern views, the ecosystem has a tendency to develop towards its stable state - a mature ecosystem. This change is called succession. The early stages of succession are characterized by low species diversity and low biomass. The ecosystem in the initial stage of development is very sensitive to disturbances, and a strong impact on the main energy flow can destroy it. In mature ecosystems, flora and fauna increase. In this case, damage to one component cannot have a strong impact on the entire ecosystem. Hence, a mature ecosystem has a high degree of stability.

As noted above, geological, climatic, hydrogeological and cosmic influences in relation to a given ecological system act as external forces. Among the external forces that affect ecosystems, human impact occupies a special place. The biological laws of the structure, functioning and development of natural ecosystems are associated only with those organisms that are their necessary components. In this regard, a person, both socially (individual) and biologically (organism), is not included in natural ecosystems. This follows at least from the fact that any natural ecosystem in its origin and development can do without a person. Man is not a necessary element of this system. In addition, the emergence and existence of organisms is due only to the general laws of the ecosystem, while a person is generated by society and exists in society. Man as a person and as a biological being is a component of a special system - human society, which has historically changing economic laws of food distribution and other conditions of its existence. At the same time, the elements necessary for life, such as air and water, a person receives from outside, since human society is an open system into which energy and matter come from outside. Thus, a person is an "external element" and cannot enter into permanent biological relations with elements of natural ecosystems. On the other hand, acting as an external force, man has a great influence on ecosystems. In this regard, it is necessary to point out the possibility of the existence of two types of ecosystems: natural (natural) and artificial. Development (succession) natural ecosystems obeys the laws of evolution or the laws of cosmic influences (permanence or catastrophes). artificial ecosystems- these are aggregates of living organisms and plants living in conditions that a person has created with his labor, his thought. The power of human impact on nature is manifested precisely in artificial ecosystems, which today cover most of the Earth's biosphere.

Ecological human interference has obviously always taken place. All previous human activity can be viewed as a process of subordinating many or even all ecological systems, all biocenoses to human needs. Human intervention could not but affect the ecological balance. Even ancient man, burning forests, violated the ecological balance, but he did it slowly and on a relatively small scale. Such interference was more local in nature and did not cause global consequences. In other words, human activity of that time took place in conditions close to equilibrium. However, now the impact of man on nature, due to the development of science, technology and technology, has taken on such a scale that the violation of the ecological balance has become threatening on a global scale. If the process of human impact on ecosystems were not spontaneous, and sometimes predatory, then the issue of the ecological crisis would not be so acute. Meanwhile, human activity today has become so commensurate with the powerful forces of nature that nature itself is no longer able to cope with the loads it experiences.

Thus, the main essence of the problem of environmental protection lies in the fact that mankind, thanks to its labor activity, has become such a powerful nature-forming force that its influence began to manifest itself much faster than the influence of the natural evolution of the biosphere.

Although the term "environmental protection" is very common today, it still does not strictly reflect the essence of the matter. Physiologist I.M. Sechenov once pointed out that a living organism cannot exist without interaction with the environment. From this point of view, the term "environmental management" seems to be more rigorous. In general, the problem of rational use of the environment is to find mechanisms that ensure the normal functioning of the biosphere.

TEST QUESTIONS

1. Define the term "environment".

2. What is the main essence of the problem of environmental protection?

3. List the various aspects of the problem of environmental protection.

4. Define the term "chemical ecology".

5. List the main geospheres of our planet.

6. Specify the factors that determine the upper and lower limits of the biosphere.

7. List the biophilic elements.

8. Comment on the impact of human activity on the natural cycle of carbon transformations.

9. What can you say about the mechanism of photosynthesis?

10. Give a diagram of the breathing process.

11. Give a diagram of fermentation processes.

12. Define the terms "producer", "consumer", "reducer".

13. What is the difference between "autotrophs" and "heterotrophs"?

14. Define the term "noosphere".

15. What is the essence of the "ecological pyramid" rule?

16. Define the terms "bioton" and "biocenosis".

17. Define the term "ecosystem".

Microelements and enzymes. Introduction to metalloenzymes. Specific and non-specific enzymes. The role of metal ions in enzymes. Horizontal similarity in the biological action of d-elements. Synergism and antagonism of elements.

The propensity of ions of d-elements to hydrolysis and polymerization

In acidic environments, ions of the d-element are in the form of hydrated ions [M(H 2 O) m] n+. With an increase in pH, hydrated ions of many d-elements, due to the large charge and small size of the ion, have a high polarizing effect on water molecules, an acceptor capacity for hydroxide ions, undergo cationic hydrolysis, and form strong covalent bonds with OH - . The process ends either with the formation of basic salts [M (OH) m] (m-n) +, or insoluble hydroxides M (OH) n, or hydroxo complexes [M (OH) m] (n-m) -. The process of hydrolytic interaction can proceed with the formation of multinuclear complexes as a result of the polymerization reaction.

2. 4. Biological role of d-elements (transitional elements)

Elements, the content of which does not exceed 10 -3%, are part of enzymes, hormones, vitamins and other vital compounds. For protein, carbohydrate and fat metabolism are necessary: ​​Fe, Co, Mn, Zn, Mo, V, B, W; in the synthesis of proteins involved: Mg, Mn, Fe, Co, Cu, Ni, Cr, in hematopoiesis - Co, Ti, Cu, Mn, Ni, Zn; in breath - Mg, Fe, Сu, Zn, Mn and Co. Therefore, microelements are widely used in medicine, as microfertilizers for field crops, top dressing in animal husbandry, poultry farming and fish farming. Trace elements are part of a large number of bioregulators of living systems, which are based on biocomplexes. Enzymes are special proteins that act as catalysts in biological systems. Enzymes are unique catalysts with unsurpassed efficiency and high selectivity. An example of the efficiency of the decomposition reaction of hydrogen peroxide 2H 2 O 2 ® 2H 2 O +O 2 in the presence of enzymes is shown in table 6.

Table 6. Activation energy (E o) and relative rate of H 2 O 2 decomposition reaction in the absence and presence of various catalysts

More than 2,000 enzymes are currently known, many of which catalyze a single reaction. The activity of a large group of enzymes is manifested only in the presence of certain non-protein compounds, called cofactors. Metal ions or organic compounds act as cofactors. Approximately one third of the enzymes are activated by transition metals.

Metal ions in enzymes perform a number of functions: they are the electrophilic group of the active center of the enzyme and facilitate interaction with negatively charged regions of the substrate molecules, form a catalytically active conformation of the enzyme structure (zinc and manganese ions are involved in the formation of the helical structure of RNA), participate in the transport of electrons (complexes electron transfer). The ability of a metal ion to perform its role in the active center of the corresponding enzyme depends on the ability of the metal ion to complex, the geometry and stability of the complex formed. This provides an increase in the selectivity of the enzyme with respect to substrates, activation of bonds in the enzyme or substrate through coordination and change in the shape of the substrate in accordance with the steric requirements of the active site.

Biocomplexes differ in stability. Some of them are so durable that they are constantly in the body and perform a specific function. In cases where the bond between the cofactor and the enzyme protein is strong and it is difficult to separate them, it is called a "prosthetic group". Such bonds have been found in enzymes containing a heme complex of iron with a porphin derivative. The role of metals in such complexes is highly specific: replacing it with even an element with similar properties leads to a significant or complete loss of physiological activity. These enzymes are to specific enzymes.

Examples of such compounds are chlorophyll, polyphenyloxidase, vitamin B 12 , hemoglobin and some metalloenzymes (specific enzymes). Few enzymes are involved in only one specific or single reaction.

The catalytic properties of most enzymes are determined by the active center formed by various microelements. Enzymes are synthesized for the duration of the function. The metal ion acts as an activator and can be replaced by another metal ion without loss of the physiological activity of the enzyme. These are assigned to non-specific enzymes.

The following are enzymes in which different metal ions perform similar functions.

Table 7. Enzymes in which different metal ions perform similar functions

One trace element can activate the work of various enzymes, and one enzyme can be activated by various trace elements. Enzymes with microelements in the same oxidation state +2 have the greatest similarity in biological action. As can be seen, the trace elements of transition elements in their biological action are characterized by more horizontal similarity than vertical similarity in the periodic system of D.I. Mendeleev (in the Ti-Zn series). When deciding on the use of one or another trace element, it is necessary to take into account not only the presence of mobile forms of this element, but also others that have the same oxidation state and can replace each other in the composition of enzymes.

An intermediate position between specific and nonspecific enzymes is occupied by some metalloenzymes. Metal ions act as a cofactor. Increasing the strength of the enzyme biocomplex increases the specificity of its biological action. The efficiency of the enzymatic action of the metal ion of the enzyme is influenced by its degree of oxidation. According to the intensity of influence, microelements are arranged in the following row:

Ti 4+ ®Fe 3+ ®Cu 2+ ®Fe 2+ ®Mg 2+ ®Mn 2+ . The Mn 3+ ion, in contrast to the Mn 2+ ion, is very strongly associated with proteins, and Fe 3+ together with oxygen-containing groups is predominantly a part of metalloproteins.

Trace elements in the complexonate form act in the body as a factor that apparently determines the high sensitivity of cells to trace elements through their participation in creating a high concentration gradient. The values ​​of atomic and ionic radii, ionization energies, coordination numbers, the tendency to form bonds with the same elements in bioligand molecules determine the effects observed during the mutual substitution of ions: it can occur with increased (synergism), and with the inhibition of their biological activity (antagonism) element being replaced. Ions of d-elements in the +2 oxidation state (Mn, Fe, Co, Ni, Zn) have similar physicochemical characteristics of atoms (electronic structure of the outer level, close radii of ions, type of hybridization of orbitals, close values ​​of stability constants with bioligands). The similarity of the physicochemical characteristics of the complexing agent determines the proximity of their biological action and interchangeability. The above transitional elements stimulate the processes of hematopoiesis, enhance metabolic processes. The synergism of elements in the processes of hematopoiesis is possibly associated with the participation of ions of these elements in various stages of the process of synthesis of human blood cells.

For s - elements of group I, in comparison with other elements of their period, a small charge of the nuclei of atoms, a low ionization potential of valence electrons, a large size of the atom and its increase in the group from top to bottom are characteristic. All this determines the state of their ions in aqueous solutions in the form of hydrated ions. The greatest similarity of lithium with sodium determines their interchangeability, synergy of their action. Destructive properties in aqueous solutions of potassium, rubidium and cesium ions, ensures their better membrane permeability, interchangeability and synergism of their action. The concentration of K + inside cells is 35 times higher than outside it, and the concentration of Na + in the extracellular fluid is 15 times higher than inside the cell. These ions are antagonists in biological systems. s - Group II elements in the body are in the form of compounds formed by phosphoric, carbonic and carboxylic acids. Calcium, contained mainly in bone tissue, is close in its properties to strontium and barium, which can replace it in bones. In this case, both cases of synergy and antagonism are observed. Calcium ions are also antagonists of sodium, potassium and magnesium ions. The similarity of the physicochemical characteristics of the Be 2+ and Mg 2+ ions determines their interchangeability in compounds containing Mg–N and Mg–O bonds. This can explain the inhibition of magnesium-containing enzymes when beryllium enters the body. Beryllium is a magnesium antagonist. Consequently, the physicochemical properties and biological action of microelements are determined by the structure of atoms. Most of the biogenic elements are members of the second, third and fourth periods of the D.I. Mendeleev. These are relatively light atoms, with a relatively small charge of the nuclei of their atoms.

2. 4. 2. The role of compounds of transition elements in the transfer of electrons in living systems.

In a living organism, many processes have a cyclic, wave-like character. The underlying chemical processes must be reversible. The reversibility of processes is determined by the interaction of thermodynamic and kinetic factors. Reversible reactions include those with constants from 10 -3 to 10 3 and with a small value of DG 0 and DE 0 of the process. Under these conditions, the concentrations of the initial substances and reaction products can be in comparable concentrations, and by changing them in a certain range, it is possible to achieve the reversibility of the process. From the kinetic standpoint, there should be low activation energies. Therefore, metal ions (iron, copper, manganese, cobalt, molybdenum, titanium, and others) are a convenient carrier of electrons in living systems. The addition and release of an electron cause changes only in the electronic configuration of the metal ion, without significantly changing the structure of the organic component of the complex. A unique role in living systems is assigned to two redox systems: Fe 3+ /Fe 2+ and Cu 2+ /Cu + . Bioligands stabilize the oxidized form to a greater extent in the first pair, and predominantly the reduced form in the second pair. Therefore, in systems containing iron, the formal potential is always lower, and in systems containing copper, often higher, redox systems containing copper and iron cover a wide range of potentials, which allows them to interact with many substrates, accompanied by moderate changes in DG 0 and DE 0 , which meets the conditions of reversibility. An important stage of metabolism is the splitting of hydrogen from nutrients. In this case, hydrogen atoms pass into the ionic state, and the electrons separated from them enter the respiratory chain; in this chain, passing from one compound to another, they give up their energy to form one of the main sources of energy, adenosine triphosphoric acid (ATP), and they themselves, ultimately, get to the oxygen molecule and attach to it, forming water molecules. The bridge along which the electrons oscillate are complex compounds of iron with a porphyrin core, similar in composition to hemoglobin.

A large group of iron-containing enzymes that catalyze the process of electron transfer in mitochondria is called cytochromes(c. x.), In total, about 50 cytochromes are known. Cytochromes are iron porphyrins in which all six orbitals of the iron ion are occupied by donor atoms, the bioligand. The difference between cytochromes is only in the composition of the side chains of the porphyrin ring. Variations in the structure of the bioligand cause a difference in the magnitude of the formal potentials. All cells contain at least three structurally related proteins, called cytochromes a, b, c. In cytochrome c, the connection with the histidine residue of the polypeptide chain is carried out through the porphyrin core. The free coordination site in the iron ion is occupied by the methionine residue of the polypeptide chain:

One of the mechanisms of the functioning of cytochromes, which make up one of the links in the electron transport chain, is the transfer of an electron from one substrate to another.

From a chemical point of view, cytochromes are compounds that exhibit redox duality under reversible conditions.

Electron transfer by cytochrome c is accompanied by a change in the oxidation state of iron:

c. X. Fe 3+ + e "c.xFe 2+

The oxygen ions react with the hydrogen ions of the environment and form water or hydrogen peroxide. Peroxide is quickly decomposed by a special enzyme catalase into water and oxygen according to the scheme:

2H 2 O 2 ®2H 2 O + O 2

The enzyme peroxidase accelerates the oxidation reactions of organic substances with hydrogen peroxide according to the scheme:

These enzymes have a heme in their structure, in the center of which there is iron with an oxidation state of +3 (2 section 7.7).

In the electron transport chain, cytochrome c transfers electrons to cytochromes called cytochrome oxidases. They contain copper ions. Cytochrome is a single electron carrier. The presence of copper in one of the cytochromes along with iron turns it into a two-electron carrier, which makes it possible to control the rate of the process.

Copper is part of an important enzyme - superoxide dismutase (SOD), which utilizes the toxic superoxide ion O 2 - in the body by the reaction

[SOD Cu 2+] + ® O 2 - [SOD Cu +] + O 2

[SOD Cu +] + O 2 - + 2H + ® [SODCu 2+] + H 2 O 2

Hydrogen peroxide decomposes in the body under the action of catalase.

Currently, about 25 copper-containing enzymes are known. They form a group of oxygenases and hydroxylases. The composition, the mechanism of their action is described in work (2, section 7.9.).

Complexes of transition elements are a source of microelements in a biologically active form with high membrane permeability and enzymatic activity. They are involved in protecting the body from "oxidative stress". This is due to their participation in the utilization of metabolic products that determine the uncontrolled oxidation process (by peroxides, free radicals, and other oxygen-active particles), as well as in the oxidation of substrates. The mechanism of the free-radical reaction of substrate oxidation (RN) with hydrogen peroxide with the participation of an iron complex (FeL) as a catalyst can be represented by reaction schemes.

RN + . OH ® R . + H 2 O; R. + FeL ® R + + FeL

substrate

R + + OH - ® RON

Oxidized substrate

The further course of the radical reaction leads to the formation of products with a higher degree of hydroxylation. Other radicals act similarly: HO 2. , O 2 . , . About 2 - .

2. 5. General characteristics of the p-block elements

Elements in which the completion of the p-sublevel of the outer valence level is called p-elements. The electronic structure of the valence level ns 2 p 1-6. The electrons of the s- and p-sublevels are valence.

Table 8. The position of the p-elements in the Periodic Table of the Elements.

Period	Group
IIIA	IVA	VA	VIA	VIIA	VIIIA
		(C)	(N)	(o)	(F)	Ne
			(P)	(S)	(Cl)	Ar
	Ga					kr
	In	sn	Sb	Te	(I)	Xe
	Tl	Pb	Bi	Po	At	Rn
	p 1	p 2	p 3	p 4	p 5	R 6
() - irreplaceable elements, - biogenic elements

In periods from left to right, the charge of the nuclei increases, the influence of which prevails over the increase in the forces of mutual repulsion between electrons. Therefore, the ionization potential, electron affinity, and, consequently, the acceptor ability and non-metallic properties increase in periods. All elements lying on the diagonal Br - At and above are non-metals and form only covalent compounds and anions. All other p-elements (with the exception of indium, thallium, polonium, bismuth, which exhibit metallic properties) are amphoteric elements and form both cations and anions, and both are strongly hydrolyzed. Most non-metal p-elements are biogenic (with the exception of noble gases, tellurium and astatine). Of the p-elements - metals - only aluminum is considered biogenic. Differences in the properties of neighboring elements, as inside; and for the period: they are much more pronounced than those of the s-elements. p-Elements of the second period - nitrogen, oxygen, fluorine have a pronounced ability to participate in the formation of hydrogen bonds. Elements of the third and subsequent periods lose this ability. Their similarity lies only in the structure of the outer electron shells and those valence states that arise due to unpaired electrons in unexcited atoms. Boron, carbon, and especially nitrogen, are very different from the rest of the elements of their groups (the presence of d- and f-sublevels).

All p-elements, and in particular the p-elements of the second and third periods (C, N, P, O, S, Si, Cl) form numerous compounds with each other and with s-, d- and f-elements. Most compounds known on Earth are p-element compounds. The five main (macrobiogenic) p-elements of life - O, P, C, N and S - are the main building material from which the molecules of proteins, fats, carbohydrates and nucleic acids are composed. Of the low molecular weight compounds of p-elements, oxoanions are of greatest importance: CO 3 2-, HCO 3 -, C 2 O 4 2-, CH3COO -, PO 4 3-, HPO 4 2-, H 2 PO 4 -, SO 4 2- and halide ions. p-Elements have many valence electrons with different energies. Therefore, the compounds show different degrees of oxidation. For example, carbon exhibits various oxidation states from -4 to +4. Nitrogen - from -3 to +5, chlorine - from -1 to +7.

During the reaction, the p-element can donate and accept electrons, acting respectively as a reducing agent or an oxidizing agent, depending on the properties of the element with which it interacts. This gives rise to a wide range of compounds formed by them. The mutual transition of p-element atoms of different oxidation states, including through metabolic redox processes (for example, the oxidation of an alcohol group to their aldehyde and then to carboxyl, and so on) causes a wealth of their chemical transformations.

A carbon compound exhibits oxidizing properties if, as a result of a reaction, carbon atoms increase the number of its bonds with atoms of less electronegative elements (metal, hydrogen) because, by attracting common bond electrons, the carbon atom lowers its oxidation state.

CH 3 ® -CH 2 OH ® -CH \u003d O ® -COOH ® CO 2

The redistribution of electrons between an oxidizing agent and a reducing agent in organic compounds can only be accompanied by a shift in the total electron density of a chemical bond to the atom that acts as an oxidizing agent. In the case of strong polarization, this bond may break.

Phosphates in living organisms serve as structural components of the skeleton, cell membranes and nucleic acids. Bone tissue is built mainly from hydroxyapatite Ca 5 (PO 4) 3 OH. Phospholipids are the basis of cell membranes. Nucleic acids are composed of ribose or deoxyribose phosphate chains. In addition, polyphosphates are the main source of energy.

In the human body, NO is necessarily synthesized using the enzyme NO-synthase from the amino acid arginine. The lifetime of NO in the cells of the body is about a second, but their normal functioning is not possible without NO. This compound provides: relaxation of the smooth muscles of the vascular muscles, regulation of the work of the heart, effective functioning of the immune system, transmission of nerve impulses. NO is expected to play an important role in learning and memory.

Redox reactions involving p-elements underlie their toxic effects on the body. The toxic effect of nitrogen oxides is associated with their high redox ability. Nitrates ingested in food are reduced to nitrites in the body.

NO 3 - + 2H + + 2e ® NO 2 + H 2 O

Nitrites are highly toxic. They convert hemoglobin to methemoglobin, which is a product of hydrolysis and oxidation of hemoglobin.

As a result, hemoglobin loses its ability to transport oxygen to the cells of the body. The body develops hypoxia. In addition, nitrites, as salts of a weak acid, react with hydrochloric acid in the gastric contents, forming nitrous acid, which forms carcinogenic nitrosamines with secondary amines:

The biological effect of high molecular weight organic compounds (amino acids, polypeptides, proteins, fats, carbohydrates and nucleic acids) is determined by atoms (N, P, S, O) or formed groups of atoms (functional groups), in which they act as chemically active centers, donors electron pairs capable of forming coordination bonds with metal ions and organic molecules. Therefore, p-elements form polydentate chelating compounds (amino acids, polypeptides, proteins, carbohydrates and nucleic acids). They are characterized by complexation reactions, amphoteric properties, and anionic hydrolysis reactions. These properties determine their participation in the main biochemical processes, in ensuring the state of isohydria. They form protein, phosphate, hydrogen carbonate buffer systems. They participate in the transport of nutrients, metabolic products, and other processes.

3. 1. The role of the environment. Chemistry of atmospheric pollution. The role of the doctor in protecting the environment and human health.

A. P. Vinogradov showed that the surface of the earth is heterogeneous in chemical composition. Plants and animals, as well as humans, located on the territory of different zones, use nutrients that are not the same in chemical composition and respond to this with certain physiological reactions and a certain chemical composition of the body. The effects caused by trace elements depend on their intake in the body. The concentrations of biometals in the body during its normal functioning are maintained at a strictly defined level (biotic dose) with the help of appropriate proteins and hormones. Stocks of biometals in the body are systematically replenished. They are found in sufficient quantities in the food taken. The chemical composition of plants and animals going for food affects the body.

Intensive industrial production has led to environmental pollution with "harmful" substances, including compounds of transition elements. In nature, there is an intensive redistribution of elements in biogeochemical provinces. The main way (up to 80%) of their intake with the body is our food. Given the anthropogenic pollution of the environment, it is necessary to take radical measures to rehabilitate the environment and the people living in it. This problem in many European countries is put ahead of the problems of economic growth and is among the priorities. In recent years, the emission of various pollutants has increased. The forecast for the development of industry allows us to conclude that there will be a further increase in the amount of emissions and environmental pollutants.

The real zones in which, as a result of vital activity, the circulation of elements is carried out, are called ecosystems or, as Academician V.N. Sukachev, biogeocenoses. Man is an integral part of ecosystems on our planet. In his life, a person can disrupt the course of the natural biogenic cycle. The environment is polluted by many industries. According to the teachings of V. I. Vernadsky, the shell of our planet, changed by human economic activity, is called noosphere. It covers the entire biosphere and goes beyond its limits (stratosphere, deep mines, wells, etc.). The main role in the noosphere is played by technogenic migration of elements - technogenesis. Research on the geochemistry of the noosphere is the theoretical basis for the rational use of natural resources and the fight against environmental pollution. Gaseous, liquid, solid environmental pollution form toxic aerosols (fog, smoke) in the surface layer of the atmosphere. When the atmosphere is polluted with sulfur dioxide, high humidity in the absence of temperature, toxic smog is formed. The main harm to the environment is caused by the oxidation products of SO 2, SO 3 and acids H 2 SO 3 and H 2 SO 4. As a result of emissions of sulfur oxide, nitrogen in industrial regions, "acid" rains are observed. Rainwater containing high concentrations of hydrogen ions can leach out toxic metal ions:

ZnO(t) + 2H + = Zn 2+ (p) + H 2 O

During the operation of an internal combustion engine, nitrogen oxides are released, the conversion product of which is ozone:

N 2 + O 2 "2NO (in the engine cylinder)

Of great concern to society are environmental problems, the chemical essence of which is to protect the biosphere from an excess of carbon and methane oxides, creating a "greenhouse effect", sulfur and nitrogen oxides, leading to "acid rain"; halogen derivatives (chlorine, fluorine) hydrocarbons that violate the "Earth's ozone shield"; carcinogenic substances (polyaromatic hydrocarbons and products of their incomplete combustion) and other products. Nowadays, not only the problem of environmental protection is becoming relevant, but also the protection of the internal environment. There is a growing number of substances entering the living organism, which are alien, alien to life and are called xenobiotics. According to the World Health Organization, there are about 4 million of them. They enter the body with food, water and air, as well as in the form of drugs (dosage forms).

This is due to the low culture of manufacturers and consumers of chemicals who do not have professional chemical knowledge. Indeed, only ignorance of the properties of substances, the inability to foresee the consequences of their excessive use can cause irreparable losses of nature, of which man is an integral element. Indeed, until now, some manufacturers, and even medical workers, are likened to Bulgakov's miller, who wanted to immediately recover from malaria with an incredible (shock) dose of quinine, but did not have time - he died. The role of various chemical elements in environmental pollution and the occurrence of diseases, including occupational ones, has not yet been sufficiently studied. It is necessary to analyze the entry into the environment of various substances as a result of human activity, the ways they enter the human body, plants, their interaction with living organisms at different levels and develop a system of effective measures aimed at both preventing further environmental pollution and creating the necessary biological means of protecting the internal environment of the body. Medical workers are obliged to take part in the development and implementation of technical, preventive, sanitary and hygienic and health-improving measures.

3.2 Biochemical provinces. endemic diseases.

The zones within which animals and plants are characterized by a certain chemical elemental composition are called biogeochemical provinces. Biogeochemical provinces are taxa of the biosphere of the third order - territories of various sizes within subregions of the biosphere with constant characteristic reactions of organisms (for example, endemic diseases). Distinguish - two kinds of biogeochemical provinces - natural and technogenic, arising from the | development of ore deposits, emissions from the metallurgical and chemical industries, the use of fertilizers in agriculture. It is necessary to pay attention to the role of microorganisms in creating the geochemical features of the environment. Deficiency and excess of elements can lead to the formation of biogeochemical provinces, due to both the lack of elements (iodine, fluorine, calcium, copper, and other provinces) and their excess (boric, molybdenum, fluorine, copper, etc.). An interesting and important problem is the deficiency of bromine within the continental regions, mountainous regions and the excess of bromine in coastal and volcanic landscapes. In these regions, the evolution of the central nervous system proceeded qualitatively differently. A biogeochemical province has been discovered in the Southern Urals on nickel-enriched rocks. It is characterized by ugly forms of grasses, diseases of sheep associated with an increased content of nickel in the environment.

The ratio of biogeochemical provinces with their ecological state made it possible to distinguish the following territories: a) with a relatively satisfactory ecological situation - (zone of relative well-being); b) with reversible, limited, and in most cases remedied environmental violations - (zone of ecological risk); c) with a sufficiently high degree of trouble observed over a long period over a large territory, the elimination of which requires significant costs and time - (zone of ecological crisis); d) with a very high degree of ecological trouble, almost irreversible environmental disturbances that have a clear localization -( ecological disaster zone).

According to the impact factor, its level, duration of action and distribution area, the following natural and technogenic biogeochemical provinces have been identified as risk and crisis zones:

1. polymetallic (Pb, Cd, Hjg, Cu, Zn) with dominant Cu-Zn, Cu-Ni, Pb-Zn associations, including:

· enriched with copper (Southern Urals, Bashkortostan, Norilsk, Mednogorsk);

· enriched with nickel (Norilsk, Monchegorsk, Nickel, Polyarny, Tuva, Southern Urals);

· enriched with lead (Altai, Caucasus, Transbaikalia);

· enriched with fluorine (Kirovsk, Krasnoyarsk, Bratsk);

· with a high content of uranium and radionuclides in the environment (Transbaikalia, Altai, South Urals).

2. biogeochemical provinces with microelement deficiencies (Se, I, Cu, Zn, etc.).

Ecological aspects of the chemistry of elements

Microelements and enzymes. Introduction to metalloenzymes. Specific and non-specific enzymes. The role of metal ions in enzymes. Horizontal similarity in the biological action of d-elements. Synergism and antagonism of elements.

The propensity of ions of d-elements to hydrolysis and polymerization

In acidic environments, ions of the d-element are in the form of hydrated ions [M(H 2 O) m] n+. With an increase in pH, hydrated ions of many d-elements, due to the large charge and small size of the ion, have a high polarizing effect on water molecules, an acceptor capacity for hydroxide ions, undergo cationic hydrolysis, and form strong covalent bonds with OH - . The process ends either with the formation of basic salts [M (OH) m] (m-n) +, or insoluble hydroxides M (OH) n, or hydroxo complexes [M (OH) m] (n-m)-. The process of hydrolytic interaction can proceed with the formation of multinuclear complexes as a result of the polymerization reaction.

2. 4. Biological role of d-elements (transitional elements)

Elements, the content of which does not exceed 10 -3%, are part of enzymes, hormones, vitamins and other vital compounds. For protein, carbohydrate and fat metabolism are necessary: ​​Fe, Co, Mn, Zn, Mo, V, B, W; in the synthesis of proteins involved: Mg, Mn, Fe, Co, Cu, Ni, Cr, in hematopoiesis - Co, Ti, Cu, Mn, Ni, Zn; in breath - Mg, Fe, Сu, Zn, Mn and Co. For this reason, microelements are widely used in medicine, as microfertilizers for field crops, as a top dressing in animal husbandry, poultry farming and fish farming. Trace elements are part of a large number of bioregulators of living systems, which are based on biocomplexes. Enzymes are special proteins that act as catalysts in biological systems. Enzymes are unique catalysts with unsurpassed efficiency and high selectivity. An example of the efficiency of the decomposition reaction of hydrogen peroxide 2H 2 O 2 ® 2H 2 O +O 2 in the presence of enzymes is shown in table 6.

Table 6. Activation energy (E o) and relative rate of H 2 O 2 decomposition reaction in the absence and presence of various catalysts

More than 2,000 enzymes are known today, many of which catalyze a single reaction. The activity of a large group of enzymes is manifested only in the presence of certain non-protein compounds, called cofactors. Metal ions or organic compounds act as cofactors. Approximately one third of the enzymes are activated by transition metals.

Metal ions in enzymes perform a number of functions: they are the electrophilic group of the active center of the enzyme and facilitate interaction with the negatively charged regions of the substrate molecules; they form a catalytically active conformation of the enzyme structure (zinc and manganese ions take part in the formation of the helical structure of RNA), take part in the transport of electrons (electron transfer complexes). The ability of a metal ion to perform its role in the active center of the corresponding enzyme depends on the ability of the metal ion to complex, the geometry and stability of the complex formed. This provides an increase in the selectivity of the enzyme with respect to substrates, activation of bonds in the enzyme or substrate through coordination and change in the shape of the substrate in accordance with the steric requirements of the active center.

Biocomplexes differ in stability. Some of them are so durable that they are constantly in the body and perform a specific function. In cases where the bond between the cofactor and the enzyme protein is strong and it is difficult to separate them, it is called a "prosthetic group". Such bonds have been found in enzymes containing a heme-complex compound of iron with a porphin derivative. The role of metals in such complexes is highly specific: replacing it with even an element with similar properties leads to a significant or complete loss of physiological activity. These enzymes are to specific enzymes.

Examples of such compounds are chlorophyll, polyphenyl oxidase, vitamin B 12, hemoglobin, and some metalloenzymes (specific enzymes). Few enzymes take part in only one specific or single reaction.

The catalytic properties of most enzymes are determined by the active center formed by various microelements. Enzymes are synthesized for the duration of the function. The metal ion acts as an activator and can be replaced by another metal ion without loss of the physiological activity of the enzyme. These are assigned to non-specific enzymes.

The following are enzymes in which different metal ions perform similar functions.

Table 7. Enzymes in which different metal ions perform similar functions

One trace element can activate the work of various enzymes, and one enzyme can be activated by various trace elements. Enzymes with microelements in the same oxidation state +2 have the greatest similarity in biological action. As can be seen, the trace elements of transition elements in their biological action are characterized by more horizontal similarity than vertical similarity in the periodic system of D.I. Mendeleev (in the Ti-Zn series). When deciding on the use of one or another trace element, it is extremely important to take into account not only the presence of mobile forms of this element, but also others that have the same oxidation state and can replace each other in the composition of enzymes.

An intermediate position between specific and nonspecific enzymes is occupied by some metalloenzymes. Metal ions act as a cofactor. Increasing the strength of the enzyme biocomplex increases the specificity of its biological action. The efficiency of the enzymatic action of the metal ion of the enzyme is influenced by its degree of oxidation. According to the intensity of influence, microelements are arranged in the following row:

Ti 4+ ®Fe 3+ ®Cu 2+ ®Fe 2+ ®Mg 2+ ®Mn 2+ . The Mn 3+ ion, in contrast to the Mn 2+ ion, is very strongly associated with proteins, and Fe 3+ together with oxygen-containing groups is predominantly a part of metalloproteins.

Trace elements in the complexonate form act in the body as a factor that apparently determines the high sensitivity of cells to trace elements through their participation in creating a high concentration gradient. The values ​​of atomic and ionic radii, ionization energies, coordination numbers, the tendency to form bonds with the same elements in bioligand molecules determine the effects observed during the mutual substitution of ions: it can occur with increased (synergism), and with the inhibition of their biological activity (antagonism) element being replaced. Ions of d-elements in the +2 oxidation state (Mn, Fe, Co, Ni, Zn) have similar physicochemical characteristics of atoms (electronic structure of the outer level, close radii of ions, type of hybridization of orbitals, close values ​​of stability constants with bioligands). The similarity of the physicochemical characteristics of the complexing agent determines the proximity of their biological action and interchangeability. The above transitional elements stimulate the processes of hematopoiesis, enhance metabolic processes. The synergy of elements in the processes of hematopoiesis is possibly associated with the participation of ions of these elements in various stages of the process of synthesis of human blood cells.

For s - elements of group I, in comparison with other elements of their period, a small charge of the nuclei of atoms, a low ionization potential of valence electrons, a large size of the atom and its increase in the group from top to bottom are characteristic. All this determines the state of their ions in aqueous solutions in the form of hydrated ions. The greatest similarity of lithium with sodium determines their interchangeability, synergy of their action. Destructive properties in aqueous solutions of potassium, rubidium and cesium ions, ensures their better membrane permeability, interchangeability and synergy of their action. The concentration of K + inside cells is 35 times higher than outside it, and the concentration of Na + in the extracellular fluid is 15 times higher than inside the cell. These ions are antagonists in biological systems. s - Elements of group II in the body are in the form of compounds formed by phosphoric, carbonic and carboxylic acids. Calcium, contained mainly in bone tissue, is close in its properties to strontium and barium, which can replace it in bones. In this case, both cases of synergism and antagonism are observed. Calcium ions are also antagonists of sodium, potassium and magnesium ions. The similarity of the physicochemical characteristics of Be 2+ and Mg 2+ ions determines their interchangeability in compounds containing Mg–N and Mg–O bonds. This can explain the inhibition of magnesium-containing enzymes when beryllium enters the body. Beryllium is a magnesium antagonist. Consequently, the physicochemical properties and biological action of microelements are determined by the structure of atoms. Most of the biogenic elements are members of the second, third and fourth periods of the D.I. Mendeleev. These are relatively light atoms, with a relatively small charge of the nuclei of their atoms.

2. 4. 2. The role of compounds of transition elements in the transfer of electrons in living systems.

In a living organism, many processes have a cyclic, wave-like character. The underlying chemical processes must be reversible. The reversibility of processes is determined by the interaction of thermodynamic and kinetic factors. Reversible reactions include those with constants from 10 -3 to 10 3 and with a small value of DG 0 and DE 0 of the process. Under these conditions, the concentrations of the initial substances and reaction products can be in comparable concentrations, and by changing them in a certain range, it is possible to achieve the reversibility of the process. From the kinetic point of view, there should be low activation energies. For this reason, metal ions (iron, copper, manganese, cobalt, molybdenum, titanium, and others) are a convenient carrier of electrons in living systems. The addition and release of an electron cause changes only in the electronic configuration of the metal ion, without significantly changing the structure of the organic component of the complex. A unique role in living systems is assigned to two redox systems: Fe 3+ /Fe 2+ and Cu 2+ /Cu + . Bioligands stabilize the oxidized form to a greater extent in the first pair, and predominantly the reduced form in the second pair. For this reason, in systems containing iron, the formal potential is always lower, and in systems containing copper, the formal potential is often higher. Redox systems containing copper and iron cover a wide range of potentials, which allows them to interact with many substrates, accompanied by moderate changes in DG 0 and DE 0, which meets the conditions of reversibility. An important stage of metabolism is the splitting of hydrogen from nutrients. In this case, hydrogen atoms pass into the ionic state, and the electrons separated from them enter the respiratory chain; in this chain, passing from one compound to another, they give up their energy to the formation of one of the basic energy sources, adenosine triphosphoric acid (ATP), and they themselves, ultimately, get to the oxygen molecule and attach to it, forming water molecules. The bridge along which the electrons oscillate are complex compounds of iron with a porphyrin core, similar in composition to hemoglobin.

A large group of iron-containing enzymes that catalyze the process of electron transfer in mitochondria is commonly called cytochromes(c. x.), In total, about 50 cytochromes are known. Cytochromes are iron porphyrins, in which all six orbitals of the iron ion are occupied by donor atoms, the bioligand. The difference between cytochromes is only in the composition of the side chains of the porphyrin ring. Variations in the structure of the bioligand cause a difference in the magnitude of the formal potentials. All cells contain at least three structurally related proteins, called cytochromes a, b, c. In cytochrome c, the connection with the histidine residue of the polypeptide chain is carried out through the porphyrin core. The free coordination site in the iron ion is occupied by the methionine residue of the polypeptide chain:

One of the mechanisms of the functioning of cytochromes, which make up one of the links in the electron transport chain, is the transfer of an electron from one substrate to another.

From a chemical point of view, cytochromes are compounds that exhibit redox duality under reversible conditions.

Electron transfer by cytochrome c is accompanied by a change in the oxidation state of iron:

c. X. Fe 3+ + e "c.xFe 2+

The oxygen ions react with the hydrogen ions of the environment and form water or hydrogen peroxide. Peroxide is quickly decomposed by a special enzyme catalase into water and oxygen according to the scheme:

2H 2 O 2 ®2H 2 O + O 2

The enzyme peroxidase accelerates the oxidation reactions of organic substances with hydrogen peroxide according to the scheme:

These enzymes have heme in their structure, in the center of which there is iron with an oxidation state of +3 (2 section 7.7).

In the electron transport chain, cytochrome c transfers electrons to cytochromes called cytochrome oxidases. Οʜᴎ contain copper ions. Cytochrome is a single electron carrier. The presence of copper, along with iron, in one of the cytochromes turns it into a two-electron carrier, which makes it possible to control the rate of the process.

Copper is part of an important enzyme - superoxide dismutase (SOD), which utilizes the toxic superoxide ion O 2 - in the body by the reaction

[SOD Cu 2+] + ® O 2 - [SOD Cu +] + O 2

[SOD Cu +] + O 2 - + 2H + ® [SODCu 2+] + H 2 O 2

Hydrogen peroxide decomposes in the body under the action of catalase.

About 25 copper-containing enzymes are known today. Οʜᴎ make up a group of oxygenases and hydroxylases. The composition, the mechanism of their action is described in work (2, section 7.9.).

Complexes of transition elements are a source of microelements in a biologically active form with high membrane permeability and enzymatic activity. Οʜᴎ take part in protecting the body from "oxidative stress". This is due to their participation in the utilization of metabolic products that determine the uncontrolled oxidation process (by peroxides, free radicals, and other oxygen-active particles), as well as in the oxidation of substrates. The mechanism of the free-radical reaction of substrate oxidation (RN) with hydrogen peroxide with the participation of an iron complex (FeL) as a catalyst can be represented by reaction schemes.

RN + . OH ® R . + H 2 O; R. + FeL ® R + + FeL

substrate

R + + OH - ® RON

Oxidized substrate

The further course of the radical reaction leads to the formation of products with a higher degree of hydroxylation. Other radicals act similarly: HO 2. , O 2 . , . About 2 - .

2. 5. General characteristics of the p-block elements

Elements in which the completion of the p-sublevel of the outer valence level is called p-elements. The electronic structure of the valence level ns 2 p 1-6. The electrons of the s- and p-sublevels are valence.

Table 8. The position of the p-elements in the Periodic Table of the Elements.

Period	Group
IIIA	IVA	VA	VIA	VIIA	VIIIA
		(C)	(N)	(o)	(F)	Ne
			(P)	(S)	(Cl)	Ar
	Ga					kr
	In	sn	Sb	Te	(I)	Xe
	Tl	Pb	Bi	Po	At	Rn
	p 1	p 2	p 3	p 4	p 5	R 6
() - irreplaceable elements, - biogenic elements

In periods from left to right, the charge of the nuclei increases, the influence of which prevails over the increase in the forces of mutual repulsion between electrons. For this reason, the ionization potential, electron affinity, and, consequently, the acceptor ability and non-metallic properties increase in periods. All elements lying on the diagonal Br - At and above are non-metals and form only covalent compounds and anions. All other p-elements (with the exception of indium, thallium, polonium, bismuth, which exhibit metallic properties) are amphoteric elements and form both cations and anions, and both are strongly hydrolyzed. Most non-metal p-elements are biogenic (with the exception of noble gases, tellurium and astatine). Of the p-elements - metals - only aluminum is considered biogenic. Differences in the properties of adjacent elements, both inside; and for the period: they are much more pronounced than those of the s-elements. p-Elements of the second period - nitrogen, oxygen, fluorine have a pronounced ability to participate in the formation of hydrogen bonds. Elements of the third and subsequent periods lose this ability. Their similarity lies only in the structure of the outer electron shells and those valence states that arise due to unpaired electrons in unexcited atoms. Boron, carbon, and especially nitrogen, are very different from the rest of the elements of their groups (the presence of d- and f-sublevels).

All p-elements, and especially p-elements of the second and third periods (C, N, P, O, S, Si, Cl) form numerous compounds with each other and with s-, d- and f-elements. Most compounds known on Earth are ϶ᴛᴏ compounds of p-elements. The five main (macrobiogenic) p-elements of life - O, P, C, N and S - are the main building material from which molecules of proteins, fats, carbohydrates and nucleic acids are composed. Of the low molecular weight compounds of p-elements, oxoanions are of greatest importance: CO 3 2-, HCO 3 -, C 2 O 4 2-, CH3COO -, PO 4 3-, HPO 4 2-, H 2 PO 4 -, SO 4 2- and halide ions. p-Elements have many valence electrons with different energies. Therefore, compounds show different degrees of oxidation. For example, carbon exhibits various oxidation states from -4 to +4. Nitrogen - from -3 to +5, chlorine - from -1 to +7.

During the reaction, the p-element can donate and accept electrons, acting respectively as a reducing agent or an oxidizing agent, depending on the properties of the element with which it interacts. This gives rise to a wide range of compounds they form. The mutual transition of p-element atoms of different oxidation states, including through metabolic redox processes (for example, the oxidation of an alcohol group to their aldehyde and then to carboxyl, and so on) causes a wealth of their chemical transformations.

A carbon compound exhibits oxidizing properties if, as a result of a reaction, carbon atoms increase the number of its bonds with atoms of less electronegative elements (metal, hydrogen) because, by attracting common bond electrons, the carbon atom lowers its oxidation state.

CH 3 ® -CH 2 OH ® -CH \u003d O ® -COOH ® CO 2

The redistribution of electrons between the oxidizing agent and the reducing agent in organic compounds can only be accompanied by a shift in the total electron density of the chemical bond to the atom that acts as the oxidizing agent. In the case of strong polarization, this bond may break.

Phosphates in living organisms serve as structural components of the skeleton of cell membranes and nucleic acids. Bone tissue is built mainly from hydroxyapatite Ca 5 (PO 4) 3 OH. Phospholipids are the basis of cell membranes. Nucleic acids are composed of ribose or deoxyribose phosphate chains. In addition, polyphosphates are the main source of energy.

In the human body, NO is necessarily synthesized using the enzyme NO-synthase from the amino acid arginine. The lifetime of NO in the cells of the body is about a second, but their normal functioning is not possible without NO. This compound provides: relaxation of the smooth muscles of the vascular muscles, regulation of the work of the heart, effective functioning of the immune system, transmission of nerve impulses. NO is expected to play an important role in learning and memory.

Redox reactions, in which p-elements take part, underlie their toxic effect on the body. The toxic effect of nitrogen oxides is associated with their high redox ability. Nitrates ingested in food are reduced to nitrites in the body.

NO 3 - + 2H + + 2e ® NO 2 + H 2 O

Nitrites are highly toxic. Οʜᴎ convert hemoglobin to methemoglobin, which is a product of hydrolysis and oxidation of hemoglobin.

As a result, hemoglobin loses its ability to transport oxygen to the cells of the body. The body develops hypoxia. At the same time, nitrites, as salts of a weak acid, react with hydrochloric acid in the gastric contents, forming nitrous acid, which forms carcinogenic nitrosamines with secondary amines:

The biological effect of high-molecular organic compounds (amino acids, polypeptides, proteins, fats, carbohydrates and nucleic acids) is determined by atoms (N, P, S, O) or groups of atoms (functional groups) formed in which they act as chemically active centers , donors of electron pairs capable of forming coordination bonds with metal ions and organic molecules. Therefore, p-elements form polydentate chelating compounds (amino acids, polypeptides, proteins, carbohydrates, and nucleic acids). It is worth saying that they are characterized by complexation reactions, amphoteric properties, anionic type hydrolysis reactions. These properties determine their participation in basic biochemical processes, in ensuring the state of isohydria. Οʜᴎ form protein, phosphate, hydrogen carbonate buffer systems. They participate in the transport of nutrients, metabolic products, and other processes.

3. 1. The role of the environment. Chemistry of atmospheric pollution. The role of the doctor in protecting the environment and human health.

A. P. Vinogradov showed that the surface of the earth is heterogeneous in chemical composition. Plants and animals, as well as humans, located on the territory of different zones, use nutrients that are not the same in chemical composition and respond to this with certain physiological reactions and a certain chemical composition of the body. The effects caused by trace elements depend on their intake in the body. The concentrations of biometals in the body during normal functioning are maintained at a strictly defined level (biotic dose) with the help of appropriate proteins and hormones. Stocks of biometals in the body are systematically replenished. Οʜᴎ are contained in sufficient quantities in the food taken. The chemical composition of plants and animals going for food affects the body.

Intensive industrial production has led to environmental pollution with "harmful" substances, including compounds of transitional elements. In nature, there is an intensive redistribution of elements in biogeochemical provinces. The main way (up to 80%) of their intake with the body is our food. Given the anthropogenic pollution of the environment, it is extremely important to take radical measures to rehabilitate the environment and the people living in it. This problem in many European countries is put ahead of the problems of economic growth and is among the priorities. In recent years, the emission of various pollutants has increased. The forecast for the development of industry allows us to conclude that there will be a further increase in the amount of emissions and environmental pollutants.

The real zones in which, as a result of vital activity, the circulation of elements is carried out, are called ecosystems or, as Academician V.N. Sukachev, biogeocenoses. Man is an integral part of ecosystems on our planet. In his life, a person can disrupt the course of the natural biogenic cycle. The environment is polluted by many industries. According to the teachings of V. I. Vernadsky, the shell of our planet, changed by human economic activity, is called noosphere. It covers the entire biosphere and goes beyond its limits (stratosphere, deep mines, wells, etc.). The main role in the noosphere is played by technogenic migration of elements - technogenesis. Research on the geochemistry of the noosphere is the theoretical basis for the rational use of natural resources and the fight against environmental pollution. Gaseous, liquid, solid environmental pollution form toxic aerosols (fog, smoke) in the surface layer of the atmosphere. When the atmosphere is polluted with sulfur dioxide, high humidity in the absence of temperature, a toxic smell is formed. The main harm to the environment is caused by the oxidation products of SO 2, SO 3 and acids H 2 SO 3 and H 2 SO 4. As a result of emissions of sulfur oxide, nitrogen in industrial regions, "acid" rains are observed. Rainwater containing high concentrations of hydrogen ions can leach out toxic metal ions:

ZnO(t) + 2H + = Zn 2+ (p) + H 2 O

During the operation of an internal combustion engine, nitrogen oxides are released, the conversion product of which is ozone:

N 2 + O 2 "2NO (in the engine cylinder)

Of great concern to society are environmental problems, the chemical essence of which is to protect the biosphere from an excess of carbon and methane oxides, which create a "greenhouse effect", sulfur and nitrogen oxides, leading to "acid rain"; halogen derivatives (chlorine, fluorine) hydrocarbons that violate the "Earth's ozone shield"; carcinogenic substances (polyaromatic hydrocarbons and products of their incomplete combustion) and other products. Nowadays, not only the problem of environmental protection is becoming relevant, but also the protection of the internal environment. There is a growing number of substances entering the living organism, which are alien, alien to life and are called xenobiotics. According to the World Health Organization, there are about 4 million of them. Οʜᴎ enter the body with food, water and air, as well as in the form of medicines (dosage forms).

This is due to the low culture of manufacturers and consumers of chemicals, who do not have professional chemical knowledge. Indeed, only ignorance of the properties of substances, the inability to foresee the consequences of their excessive use can cause irreparable losses of nature, of which man is an integral element. Indeed, until now, some manufacturers, and even medical workers, are likened to Bulgakov's miller, who wanted to immediately recover from malaria with an incredible (shock) dose of quinine, but did not have time - he died. The role of various chemical elements in environmental pollution and the occurrence of diseases, including occupational ones, has not yet been sufficiently studied. It is necessary to analyze the entry into the environment of various substances as a result of human activity, the ways they enter the human body, plants, their interaction with living organisms at different levels and develop a system of effective measures aimed at both preventing further environmental pollution and creating the necessary biological means of protecting the internal environment of the body. Medical workers are obliged to take part in the development and implementation of technical, preventive, sanitary and hygienic and health-improving measures.

3.2 Biochemical provinces. endemic diseases.

The zones within which animals and plants are characterized by a certain chemical elemental composition are called biogeochemical provinces. Biogeochemical provinces are taxa of the biosphere of the third order - territories of various sizes within subregions of the biosphere with constant characteristic reactions of organisms (for example, endemic diseases). Distinguish - two kinds of biogeochemical provinces - natural and technogenic, arising from the | development of ore deposits, emissions from the metallurgical and chemical industries, the use of fertilizers in agriculture. It is necessary to pay attention to the role of microorganisms in creating the geochemical features of the environment. Deficiency and excess of elements can lead to the formation of biogeochemical provinces, due to both the lack of elements (iodine, fluorine, calcium, copper, and other provinces) and their excess (boric, molybdenum, fluorine, copper, etc.). An interesting and important problem is the deficiency of bromine within continental regions, mountainous regions, and the excess of bromine in coastal and volcanic landscapes. In these regions, the evolution of the central nervous system proceeded qualitatively differently. A biogeochemical province has been discovered in the Southern Urals on nickel-enriched rocks. It is worth saying that it is characterized by ugly forms of grasses, diseases of sheep associated with an increased content of nickel in the environment.

The ratio of biogeochemical provinces with their ecological state made it possible to distinguish the following territories: a) with a relatively satisfactory ecological situation - (zone of relative well-being); b) with reversible, limited, and in most cases remedied environmental violations - (zone of ecological risk); c) with a sufficiently high degree of trouble observed over a long period over a large territory, the elimination of which requires significant costs and time - (zone of ecological crisis); d) with a very high degree of ecological trouble, almost irreversible environmental disturbances that have a clear localization -( ecological disaster zone).

According to the impact factor, its level, duration of action and distribution area, the following natural and technogenic biogeochemical provinces have been identified as zones of risk and crisis:

1. polymetallic (Pb, Cd, Hjg, Cu, Zn) with dominant Cu-Zn, Cu-Ni, Pb-Zn associations, including:

· enriched with copper (Southern Urals, Bashkortostan, Norilsk, Mednogorsk);

· enriched with nickel (Norilsk, Monchegorsk, Nickel, Polyarny, Tuva, Southern Urals);

· enriched with lead (Altai, Caucasus, Transbaikalia);

· enriched with fluorine (Kirovsk, Krasnoyarsk, Bratsk);

· with a high content of uranium and radionuclides in the environment (Transbaikalia, Altai, South Urals).

2. biogeochemical provinces with microelement deficiencies (Se, I, Cu, Zn, etc.).

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