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Soil is one of the main elements of the natural environment, which can negatively affect human health and living conditions as a result of the migration of various chemical compounds, biological organisms and their metabolic products. Moreover, this influence is carried out indirectly, since, unlike water and atmospheric air, direct human contact with soil in modern conditions limited except for the possibility of wound infection.
Soil value:
1. Epidemiological.
The point is that in the soil, despite the antagonism of soil microflora, pathogens of many infectious diseases can remain viable and virulent for a long time. For example, in the soil, especially in its deep layers, the pathogens of typhoid fever can survive up to 400 days, the dysentery bacillus up to 40-57 days. Spores of pathogenic anaerobic microorganisms (spores of tetanus bacillus, the causative agent of gas gangrene, botulism and anthrax) can persist for a long time, up to 20-25 years.
Human infection through contaminated soil can occur in different ways. For example, infection with tetanus and gas gangrene is possible when contaminated soil comes into direct contact with mechanically damaged skin during field work.
Pathogens of intestinal infections can be transmitted in 2 ways: 1) the body of a sick person - soil - groundwater - susceptible organism (outbreaks of typhoid fever, dysentery caused by drinking well water); 2) the patient’s body – soil – food products of plant origin – susceptible organism.
Soil dust can spread pathogens of a number of infectious diseases (mycobacterium tuberculosis, polio viruses, etc.), which are contracted when healthy people inhale such dust.
2. Soil is the environment that determines the circulation of chemicals in the external environment - human system. It is that element of the earth's biosphere that forms chemical composition food consumed by humans, drinking water and atmospheric air. It affects the body through direct contact or through media in contact with the soil along ecological chains.
There are several ways soil can affect the human body:
Through drinking water. Chemical compounds found in the soil with surface runoff enter from the surface into open bodies of water or migrate into the depths of the soil, penetrating into underground horizons (ground and interstratal waters). Contamination of water from surface and underground water sources used in water supply to populated areas may be due to the accumulation of various compounds in the soil. For example, it is possible that nitrates may appear in groundwater due to excessive use of nitrogen mineral fertilizers or organic soil pollution;
Through food (soil – plant – food – man; soil – plant – animals – food – man). Soil is an element of the biosphere that forms the chemical composition of food consumed by humans, since substances that fall into it can accumulate in plants, be included in food chains and thus affect human health;
Through atmospheric air. Chemical substances entering the soil undergo evaporation and sublimation, enter the atmospheric air and can accumulate in it to concentrations exceeding the maximum permissible concentration and reach levels hazardous to humans. This is primarily due to changes in the composition of soil air (accumulation of carbon dioxide, methane, hydrogen in it as a result of soil contamination with organic substances), which can lead to intoxication.
The unfavorable indirect influence of soil on the human body manifests itself in the form of diseases.
The composition of the soil can be determined by natural processes occurring in the earth's crust or by technogenic influence on it. There are territories in which the soil composition is characterized by increased or decreased content of microelements and a violation of their optimal relationship with each other. Such regions are called biogeochemical provinces (natural and artificial).
Natural biogeochemical provinces– these are territories characterized by an anomalous level of content and ratio of microelements, which is caused by natural processes occurring in the earth’s crust. This leads to a corresponding change in the chemical composition of water and food grown in a given area. Populations living in such regions develop endemic diseases.
Low levels of iodine in the soil lead to low iodine content in plants, and then in animal meat, as well as in water. As a result, the population's diet turns out to be deficient in iodine, which becomes the cause of endemic goiter. This disease is associated with the development of endemic cretinism, deafness and mental retardation.
Urovsky disease is also an endemic disease. This is deforming osteoarthritis, which begins at the age of 8-20 years, occurs chronically without characteristic changes in the internal organs. An increased content of strontium and a decreased content of calcium in the soil and plants was revealed, with a lesser deficiency of barium, phosphorus, copper, iodine and cobalt. Microelementosis caused by selenium deficiency (Keshan disease), caries, and fluorosis have also been described.
Artificial (man-made) provinces– these are territories that are characterized by anomalous content and ratio of macro- and microelements due to economic activity person. Their appearance is associated with the use of pesticides, mineral fertilizers, plant growth stimulants, the entry of industrial emissions into the soil, Wastewater.
The population living in these provinces for a long time is constantly exposed to the adverse effects of exogenous chemicals, therefore, in these territories there is an increase in the level of morbidity, congenital deformities and developmental anomalies, disorders of physical and mental development.
3. Soil is a natural environment for waste disposal, since it is characterized by a self-purification process. Soil is the element of the biosphere in which detoxification of exogenous organic and inorganic substances entering it occurs.
Sources of soil pollution are divided into chemical (inorganic and organic) and biological (viruses, bacteria, protozoa, helminth eggs, etc.).
Chemical substances are divided into the following groups:
1. chemicals introduced into the soil systematically, purposefully (agrochemicals - pesticides, mineral fertilizers, soil structure formers, plant growth stimulants). Agrochemicals are necessary to improve the agrotechnical properties of the soil, increase its fertility and protect cultivated plants from pests. Only in case of excessive application of these drugs do they become soil pollutants;
2. chemical substances that enter the soil accidentally, with man-made liquid, solid and gaseous waste (substances that enter the soil along with domestic and industrial wastewater, atmospheric emissions from industrial enterprises, exhaust gases from vehicles). These compounds can have toxic, allergenic, mutagenic, embryotropic and other effects.
Soil self-cleaning ability
The self-cleaning ability of soil is determined by mechanical, physicochemical, biochemical and biological processes occurring in the soil. The process of neutralizing organic matter is very complex and is carried out mainly by natural soil microflora, represented mainly by saprophytic microorganisms. Since microorganisms do not have special bodies digestion, all substances necessary for life enter the cell by osmotic absorption through the smallest pores of the membrane. These pores are so small that complex molecules (proteins, fats, carbohydrates) do not penetrate through them. In the process of evolution, microorganisms have developed the ability to release hydrolytic enzymes into the environment, which prepare the complex substances contained in it for assimilation by the microbial cell. All microbial enzymes are divided into two groups according to the nature of their action: exoenzymes, which act outside the cell, and endoenzymes, which act inside the cell. Exoenzymes are involved in the preparation of nutrients for their absorption by the cell. Endoenzymes promote the absorption of food.
The self-cleaning process occurs in two directions:
1. mineralization.
Mineralization can occur under aerobic conditions with sufficient oxygen availability and anaerobic conditions.
Under aerobic conditions, the organic substrate decomposes to carbon dioxide, water, nitrates, and phosphates. Polysaccharides that enter the soil are converted into monosaccharides, which are then partially used for the synthesis of glycogen in various microbial cells, and most of them are broken down into carbon dioxide. Fats are broken down into fatty acids with the release of energy. Proteins are broken down into amino acids. Most amino acids are used as plastic material for biosynthesis by microorganisms. The other part undergoes deamination to form ammonia, water and carbon dioxide. Nitrogen-containing organic substances enter the soil not only in the form of protein, but also amino acids and products of protein metabolism (urea). They undergo a process of nitrification - urea, under the influence of urobacteria and their enzyme urease, is hydrolyzed and also forms ammonium carbonate, which is then converted into nitrogenous compounds (nitrites) by bacteria of the genus Bac. Nitrosomonos, and then into nitrogen compounds (nitrates) by bacteria Bac. Nitrobacter. Nitrates are the final product of the breakdown of protein substances and in this form they serve as plant nutrition. In the same way, hydrogen sulfide is converted into sulfuric acid and sulfuric acid salts (sulfates), carbon dioxide into carbon dioxide salts (carbonates), phosphorus into phosphoric acid (phosphates).
Under anaerobic conditions, the decomposition of carbohydrates and fats occurs to hydrogen, carbon dioxide, methane and other gases.
2. humification is a complex biochemical anaerobic process of transformation of a dead organic substrate into a complex organic complex of great agrotechnical and hygienic importance.
From an agrotechnical point of view, humus determines soil fertility. Humus is obtained as a result of the vital activity of microorganisms and is a mass of complex chemical composition rich in organic matter (humin, lignin, carbohydrates, fats, proteins). Humification occurs under natural conditions in the soil and during the neutralization of waste in composts. At a certain stage of decomposition of organic matter, humus becomes stable, slowly decomposes, gradually releasing nutrients to plants. Although humus contains a lot of organic matter, it is not capable of rotting, does not emit an odor, and does not attract flies. During the process of humification, many pathogenic microorganisms die, although the causative agents of some infectious diseases (spores of anthrax bacilli) remain viable for a long time.
Soil is the surface layer of the earth's crust, which is a complex of mineral and organic particles with a huge number of microbes. The vegetation of the area and the chemical composition of plant and animal origin depend on the type of soil and its chemical composition. The depth of location and composition of groundwater depend on the physicochemical properties of the soil and underlying rocks. The type of soil affects the climate of the area, the topography of the soil is taken into account when planning populated areas, the ability of the soil to self-purify is used to neutralize liquid and solid waste.
Soil varies according to physical properties(particle size, porosity, humidity, air permeability), chemical composition (mineral compounds and organic substances) and microflora. Depending on the composition and particle size, clayey, loamy, sandy loam and sandy soils are distinguished.
The soil microflora is diverse: bacteria, fungi, filterable viruses, . Most soil microbes - (see). The number of microorganisms and their species composition are determined by the physical and chemical properties of the soil, humidity and air permeability. Thus, in the upper layers of the soil favorable conditions are created for the development of aerobic microbes (see Aerobes), and in the deeper layers, where the oxygen content is lower, anaerobic microorganisms predominate (see Anaerobes). Pathogenic microbes enter the soil with the excrement of humans and animals, with sputum, saliva and other secretions, with the corpses of people and animals that have died from infectious diseases. Most pathogenic microorganisms survive in the soil from several hours to several months (Flexner's dysentery bacteria survive in different soils from 25 to 100 or more days, bacteria of the typhoparatyphoid group - up to 400 days). Spore-forming bacteria, the causative agents of botulism, remain viable for a long time. Helminth eggs enter the soil with feces; some of them remain viable in the soil for several years.
Human infection can occur through direct contact with soil, through vegetables grown on soil and not washed before consumption, through products contaminated with flies (see). A serious danger is the penetration of pathogenic bacteria and viruses from the soil into water supply sources - rivers, reservoirs, ground and artesian waters. Contamination of water supply sources is possible when rain and melt water flow into a reservoir, or when pollution seeps through the soil from absorption wells, cesspools, and garbage dumps that are not equipped with waterproof receptacles for solid and liquid waste.
Physico- Chemical properties and soil microflora have important for its self-purification, i.e., the processing of organic substances that enter the soil as a result of the vital activity of living organisms, and are also introduced with industrial and household waste and garbage. The process of transformation of organic substances in the soil occurs constantly and consists of decomposition into simpler substances and the formation of mineral salts, and then in the subsequent synthesis of complex chemical compounds - humus substances (humus), which play a large role in soil fertility. At the same time, the number of microbes in the soil decreases, helminth eggs die and toxic compounds are destroyed. The ability of the soil to self-purify is not unlimited, and if the soil is excessively polluted, the processing and neutralization of waste and waste introduced into it no longer occurs. Toxic substances that can enter the soil with industrial waste and when using pesticides have an adverse effect on the self-purification of the soil (see).
Sanitary protection of soil from contamination by solid and liquid waste occupies an important place in the system of measures for the prevention of infectious diseases and the spread of helminths.
Sanitary soil protection is of particular importance in rural populated areas, where there are relatively little developed various systems cleaning. Among the priority measures for sanitary protection of the soil in these conditions should be: regular removal of liquid and solid waste and their proper neutralization - solid waste is neutralized by composting (see), liquid waste - in the fields of sewage disposal and plowing (see Sewage disposal); installation of waterproof cesspools in bathrooms of residential and public buildings and garbage dumps; installation of local sewerage for public buildings, children's and medical institutions; manure collection and composting; fight against flies. monitoring the condition of the soil is carried out using helminthological, bacteriological and chemical research methods.
Soil is the upper layer of the earth's crust (lithosphere), exposed to climate, vegetation, and the activity of living beings (microbes, worms, insects, etc.).
Humans play a huge role in the formation of soil and changes in its composition. A lot of various chemicals are introduced into the soil: fertilizers, pesticides, waste from industrial and construction activities of humans.
Great changes are also taking place in the soil of populated areas, especially in old and large cities, where natural soil, characteristic of the surrounding area, is completely replaced by an artificial one: bulk soil, displaced soil. As a result, the properties and composition of the soil in populated areas change, the groundwater level decreases, the soil biocenosis changes, inorganic and often toxic substances accumulate, pathogenic microbes, viruses, and helminths enter the soil. As a result, biological processes in the soil slow down and even stop completely; Green plantings cannot grow on such modified soil.
The quality of groundwater and open reservoirs depends on the purity of the soil and its composition. Pathogenic microbes and viruses persist in the soil for a long time, and geohelminth eggs mature. The soil may contain toxic substances that enter it with waste and industrial emissions, pesticides used in agriculture. Radioactive waste entering the soil causes an increase in the level of natural radioactive background.
The properties of soil self-purification are of great positive importance: the decomposition and synthesis of organic substances, including waste, as a result of the vital activity of ammonifying, nitrifying, humifying bacteria, fungi, and actinomycetes. As a result of the cycle of substances in the soil, organic substances (humus) and mineral salts, harmless to humans and very useful for plants, accumulate.
Sanitary protection of soil is an important section of the activities of sanitary inspection bodies. The hygienic criterion for the sanitary condition of the soil is the detection in it of substances and organisms that can cause harm to human health, well-being or worsen his living conditions (through food, water, air, Construction Materials). Sanitary supervision of soil conditions is carried out using helminthological, bacteriological, chemical and radiological research methods. To evaluate the results of the study, the following indicators can be recommended (see table).
The causative agent of infectious diseases - they are divided into 2 groups:
1. permanently living in the soil. These include pathogens of gas gangrene, anthrax, tetanus, botulism, actinomycosis (Their viability is up to 25 years)
1. Microorganisms temporarily present in the soil are pathogens of intestinal infections, pathogens of typhoid-parotiphoid diseases, dysentery bacteria, Vibrio cholerae; The causative agents of tuberculosis and the causative agents of tularemia can be present in the soil both permanently and temporarily. Pathogenic viruses can also be found in soil, including polio virus, ECHO virus, and Coxsackie virus.
The bulk of microorganisms die when they enter the soil, but individual microbes can survive in it for quite a long time. The typhoid bacillus persists in the soil for more than 13 months, the diphtheria bacillus from 1.5 to 5 weeks, etc. The survival of microorganisms depends on the type of soil, humidity, temperature, the presence of a biological substrate on which they develop, and the presence of antagonism.
The causative agent of anthrax persists in the soil for the longest time. The soil may contain pathogens of helminth infections; geo- and biohelminths are distinguished. For biohelminths, soil is a transmission factor, but they do not develop there. Biohelminths include roundworms, pinworms, whipworms, hookworms...
The role of soil in the spread of ascariasis and trichuriasis is especially great. For geohelminths, the soil creates favorable conditions for the maturation of eggs to the invasive stage.
In soil heavily contaminated with organic matter, pathogens can remain viable for a long time. In particular, dysentery bacteria survive in the soil for up to 100 days, polio viruses for up to 150 days, bacteria of the typhoid-paratyphoid group for up to 400 days, roundworm eggs for up to a year, and anthrax spores for decades.
The degree of soil contamination can be judged according to sanitary number, which is calculated as the ratio of humus nitrogen to total soil organic nitrogen. With self-purification of the soil and mineralization of organic matter, the amount of humus nitrogen increases and, consequently, the sanitary number increases, approaching unity.
Soil contaminated with organic matter promotes the development of rodents, which are carriers of especially dangerous infections: rabies, plague, tularemia. Contaminated soil is a favorable place for the development of flies (their development period is 4-7 days). The soil is a natural recipient of all waste from human activity. Prevention of soil-transmitted diseases is the sanitary protection of the soil in populated areas, sanitary measures for proper organization collection and disposal of sewage and waste.
1. The reason for the development of methemoglobinemia in humans may be the introduction into the soil of:
a) potash fertilizers
b) phosphate fertilizers
c) nitrogen fertilizers
d) pesticides
2. If contaminated soil gets into a human wound, it can cause the development of:
a) cholera
b) salmonellosis
c) gas gangrene
d) tetanus
3. Indicators of the sanitary condition of the soil are:
a) sanitary number
b) coli titer
c) titer of anaerobes
d) the number of helminth eggs per gram of soil
e) the number of earthworms per square meter soil
4. The following pathogens cannot remain viable in the soil for a long time:
a) Bac.anthracis
c) Cl.perfringens
d) Cl.Botulinum
5. “Healthy soil” should be:
a) coarse-grained, wet, highly porous
b) coarse-grained, dry, with low porosity
c) fine-grained, dry, low porosity
d) fine-grained, wet, with high porosity
6.Soil has a great influence on:
a) microclimate of the area
b) microrelief of the area
c) construction and improvement of populated areas
d) development of vegetation
7.Transmission of pathogens of intestinal diseases to humans from soil occurs:
a) through food products
b) through damaged skin
c) with water from underground sources
d) from surface waters
8.Select the appropriate indicators of standards characteristic of clean soil:
9. Soil is a transmission factor for which infectious diseases:
a) tuberculosis
c) typhoid fever
d) dysentery
e) diphtheria
e) anthrax
10. An increased content of nitrates in the soil with a low amount of chlorides indicates:
a) about long-standing soil contamination
b) about recent soil contamination
c) about constant soil pollution
d) about periodic soil contamination
11.Find the logically correct endings of the statements:
12.Select the appropriate characteristics:
13.Choose the correct conclusions:
14. Choose the correct conclusions:
Sample answers to Test control on the topic:
Soil, its physical and chemical properties,
Hygienic and environmental significance
- A B C D
- A B C D
- B, C, D
- A, B, D
- A, B, D
- 1-B, 2-A, 3-B
- 1-B, 2-A, 3-B
- 1-B, G, D, F 2-A, B
- 1-G, 2-B, 3-A
- 1-B, 2-G, 3-A
Topic: 2.2. Water, its physical and chemical properties, hygienic and environmental significance.
Plan.
1. General information about the hydrosphere. Hydrosphere, structure of the hydrosphere.
2. Epidemiological significance of water.
3. Chemical composition of water.
4. Sources of water supply.
5. Self-purification in the hydrosphere.
Water is the most precious gift of nature. This is one of the most essential natural components of the large biological cycle on which the entire ecological system is based. Water occupies a special position among the natural resources of the Earth - it is irreplaceable. The reserves of metals will run out - perhaps it will be possible to make do with plastics; If there is not enough plant and animal proteins, they will learn to obtain synthetic ones. Even instead of ordinary air, an artificial mixture of gases is suitable in some cases. Water will be necessary in all ages and everywhere where earthly forms of life exist.
Majority natural resources The planet, unfortunately, is not being restored. This applies, for example, to oil, coal, non-ferrous and precious metals etc. Water resources have a remarkable feature - the ability to be renewed in the process of circulation in the ocean-atmosphere-earth-ocean system. A gigantic mechanism works in nature, returning fresh water flowing from the continents into the oceans and seas back to land. This mechanism was “launched” by the energy of the Sun hundreds of millions of years ago.
From biology we know that life originated in an aquatic environment. For many species of animals and plants, water continues to be a habitat. In the process of evolution, the lives of many living beings
moved to land. Despite this, even in the most highly organized human mammal, fertilization occurs in a liquid medium; the embryo is surrounded by amniotic fluid throughout its development.
It is customary to divide water into intracellular, which is 72% in the body, and extracellular, 28%. Extracellular water is located inside the vascular bed, it is part of the blood, lymph, cerebrospinal fluid, it fills the intercellular space.
All processes in the body, chemical, physical-chemical, etc., are carried out in an aquatic environment. Water in the body serves as a solvent for food and metabolism, water transports substances dissolved in it, water weakens friction between contacting surfaces in the human body, water participates in the thermoregulation of the body due to evaporation, water is of primary importance in the excretory function of the body.
Water enters the body through the digestive tract in the form of liquid or water contained in dense food products. A small part of water is formed in the body itself during the metabolic process.
When there is an excess of water in the body, water poisoning occurs. With a lack of water in the body, metabolism is disrupted. The human body is unable to cope with significant dehydration. The loss of 1-1.5 liters of water already causes the need to restore water balance, a signal of which is a feeling of thirst. If water losses are not restored, then as a result of disruption of physiological processes, performance decreases, and when high temperature air, thermoregulation is disrupted and the body may overheat. Losing 15-20% of body weight in water can lead to death.
Without food, but with water, a person can live up to 2 months or more. But in the absence of water, he will live only a few days. The fact is that as a result of vital activity, excreta are constantly formed in the body, or as it is now fashionable to call them “slags”, which poison the body. These substances are released only by body fluids, urine, sweat, evaporation from time to time. lungs. If excreta is not excreted, the body will become poisoned with its own decay products, which will ultimately lead to death.
The balance of water in the body consists of its consumption and excretion.
In a normal physiological state, the human body secretes about 0.5 liters per day. with sweat, the same amount evaporates from the surface of the lungs; when breathing, slightly less - 0.4 liters is excreted in the urine. And from this it follows that the same amount of water should enter the body, that is, about 3 liters.
The physiological need for water of one person over 70 years of life is 5Ot. minimum. With the growing population on the globe, people's need for water increases sharply. In a modern city, 300-500 liters are required daily for household needs alone. water per person.
2. The epidemiological significance of water is due to the fact that it can be one of important ways spread of many infectious diseases. Cholera, typhoid fever, paratyphoid fever, bacterial and amoebic dysentery, infectious enteritis, inf. are transmitted by water. hepatitis and other diseases, including those caused by enteroviruses. The causative agents of these diseases contaminate water when secretions of patients and bacteria carriers enter it. The cause of water contamination can also be mass bathing, shipping with the discharge of sewage into the reservoir, seepage of liquid from cesspool toilets into groundwater, etc.
The causative agents of typhoid fever and dysentery persist for 2-12 days, and in frozen water they can persist throughout the winter. Even longer survival times for Vibrio cholerae. It is believed that they not only remain viable for up to 5 months or more, but also reproduce not only in river water, but also in tap water.
The third condition is that pathogens of infectious diseases must come from drinking water into the human body. This condition may
be realized in case of violation of technology at water intakes or improper operation of the water supply network.
An indirect indicator of bacterial contamination of water is E. coli. This microbe is a permanent resident of the human intestine. In external environment excreted in feces. Consequently, the bacterial indicators (coli-titer, norm 300, and coli-index 3 or less) are nothing more than the permissible norm for fecal contamination of water.
3.Chemical composition of water
In nature, water is never found in the form of a chemically pure compound. Possessing the properties of a universal solvent, it constantly carries large quantity various elements and compounds, the composition of which is determined by the conditions of water formation and the composition of aquifers.
Waters with a high content of mudflows have a brackish or bitter taste. Chlorides give water a salty taste, and sulfates give it a bitter taste. Water s. increased mineralization affects the secretory activity of the stomach, disrupts the water-salt balance, as a result of which the metabolism in the body is disrupted (mineralization limit 1000 mg/l).
The presence of calcium and magnesium salts causes water hardness. As water hardness increases, culinary processing of foods deteriorates; soap and hard water dissolve poorly. detergents, hard water can clog skin pores, which leads to premature fading, hard water contributes to the formation of scale in teapots, etc. There have long been assumptions about the role of salts that cause water hardness in the development of urolithiasis. Currently, urologists identify so-called stone zones of territory in which urolithiasis can be considered an endemic disease. There is evidence that water with a low content of hardness salts contributes to the development of cardiovascular diseases. Research results indicate that each element contained in drinking water has a physiological development not on its own, but in combination with others.
The influence of the elements fluorine and iodine on the body has been most studied. These chemical elements are washed out of the soil by water. They are capable of causing endemic diseases. A lack of iodine causes endemic goiter, a lack of fluoride causes dental caries, and an excess of fluoride causes fluorosis. The detailed effect of these elements is discussed in the chapter "Soil"
There may also be nitrogen-containing chemicals in the water. The presence of ammonia nitrogen and nitrites indicates that protein residues, animal corpses, urine, and feces are decomposing in the water. Nitrates are the end product of the oxidation of ammonium mudflows. The presence of nitrates in water in the absence of ammonium salts and nitrites indicates a relatively long-standing ingress of nitrogen-containing substances into the water, which; have already managed to mineralize..
Enrichment of water with bound nitrogen and nitrates leads to excessive algae growth. Wells begin to “bloom” due to the rapid development of blue-green algae. Increased nitrates in open waters also lead to excessive algae growth. When they die, they undergo anaerobic bacterial decomposition. This leads to oxygen deficiency and death of fish and other aquatic animals. This phenomenon is widely observed in the rivers of our country. Nitrates themselves are not known to promote the formation of methemoglobin. Their harmful effect occurs when, under the influence of intestinal microflora, they are reduced to nitrites. The absorption of nitrites leads to an increase in the content of methemoglobin in the blood.
In recent years, the attention of ecologists has been attracted by nitrosamines, substances formed by the interaction of nitrates with aliphatic and aromatic amines. These compounds are widely used in industry. Nitrosamines are highly active carcinogens. The variety of possible ways for nitrosamines to enter water from domestic drinking water supplies and their good solubility make drinking water one of the main ways for nitrosamines to enter the human body.
More often than not, nature is our natural healer. The use, in particular, of the influence of meteorological conditions is the basis of climatotherapy. Here, in addition to the well-known main friends of our health - the sun, air and water, other factors also play an important role - mineral waters, healing mud, etc.
The main thing in the therapeutic effect mineral waters the presence of minerals in their composition. Wide application They are found in the treatment of diseases of the gastrointestinal tract, the treatment of the gallbladder, pancreas, etc. Carbon dioxide baths give, for example, a good effect in diseases of the cardiovascular and respiratory systems. Hydrogen sulfide baths improve the functioning of the nervous and cardiovascular systems and have a beneficial effect on the course of metabolic processes.
In our country, some mineral waters and healing muds are unique in nature.
However, when using the gifts of nature to improve health, it is absolutely necessary to take into account the individual characteristics of a person, his age, and the nature of the illness.
Our planet is richly supplied with water. The Earth's hydrosphere contains approximately 1.5 billion km 3, but more than 96% of it is salt water of the seas and oceans, covering almost 7% the entire surface of the Earth.
Less 3% All water reserves are fresh water. Moreover, its main reserves are underground and glacial. Scientists have calculated that of the huge reserves of water on Earth, only 1% is suitable for drinking, and 1/5 of this water is concentrated in Lake Baikal.
The prospect of desalinating seawater, the amount of which is practically unlimited, seems tempting, but desalination requires enormous energy. The more polluted the environment, the more difficult it is to meet the population's water needs. While water bodies are becoming increasingly polluted and water is losing its biological value, the world's population is increasing at a rapid pace. A serious contradiction arises that needs to be resolved.
4. Sources of water supply.
The sources of centralized water supply are surface water (their share is 68%) and groundwater (32%).
Atmospheric water (snow, rainwater) for domestic and drinking water supply is used only in low-water areas, the Arctic and the South. This water is slightly mineralized, very soft, contains little organic matter and is free from pathogenic microorganisms.
Groundwater, located underground, forms several aquifers depending on its location.
Atmospheric precipitation, filtering through the pores of permeable rocks and accumulating above the first waterproof layer from the surface (clay, granite, waterproof limestone), forms the first aquifer, which is called groundwater. Depending on local conditions, the depth of ground water reservoirs varies from ]%^ 2 up to several tens of meters. During filtration, water is freed from suspended particles and microorganisms and enriched with mineral salts.
Groundwater is transparent and has low color. The amount of dissolved salts is small, but increases with increasing depth. With fine-grained rocks (starting from a depth of 5-6 m), the water contains almost no microorganisms.
Groundwater, due to its availability, is widely used in rural areas by constructing wells.
It should be noted that the first aquifer is easily contaminated by both pathogenic microorganisms and toxic chemicals due to domestic or technogenic soil contamination.
Groundwater can penetrate into the area between two layers of rock - the waterproof bed and the waterproof roof. Such waters are called inter-stratal. Depending on local conditions, interstratal waters can form second, third, and fourth aquifer levels. Water at these levels can fill the entire space and, if the roof is drilled, rises to the surface of the earth, and sometimes even pours out in a fountain. This water is called artesian
Interstratal waters have a stable mineral composition, their temperature ranges from 5-12 ° C. However, there are underground waters with excess salts: very hard, salty, bitterly salty, rich in fluorine, iron, hydrogen sulfide or radioactive substances.
Due to the fact that interstratal waters pass a long way underground, and covered on top with one or more waterproof layers that protect them from contamination from the soil surface, they are free from bacteria and, as a rule, can be used for drinking water supply without being subjected to disinfection. Thanks to the constant and high flow rate (from 1 to 20 m 3 / h and more), as well as good quality interstratal waters represent the best source of water supply for water supply systems of small and medium power.
Groundwater can independently come to the surface of the earth. This - springs. Springs can be formed by both groundwater and interstratal waters. The quality of spring water is good in most cases and depends on the aquifer feeding the spring. With proper capture - enclosing water in pipes to prevent pollution and a well-organized water collection area - this water can be used for drinking purposes.
Open bodies of water include lakes, rivers, streams, canals and reservoirs. All open bodies of water are subject to pollution by precipitation, melt and rainwater flowing from the surface of the earth. Particularly heavily polluted areas of the reservoir adjacent to settlements and places of discharge of domestic and industrial wastewater. To eliminate epidemiological danger, the water of all open reservoirs needs to be thoroughly checked.
The organoleptic properties and chemical composition of water from open reservoirs depend on a number of conditions. Clay rocks cause high turbidity, and open reservoirs in wetlands are characterized by high color.
Surface waters are usually soft and slightly mineralized. They are characterized by changes in water quality depending on the season (melting snow, rainfall). If it is necessary to use an open reservoir for centralized water supply, preference is given to large and flowing reservoirs that are sufficiently protected from pollution by wastewater.
1. Self-purification in the hydrosphere.
Each body of water is a complex living system inhabited by plants, specific organisms, including microorganisms that constantly multiply and die, which ensures self-purification of reservoirs. The factors of self-purification of reservoirs are numerous and diverse. Conventionally, they can be divided into three groups: physical, chemical and biological.
Physical factors- this is the dilution, dissolution and mixing of incoming contaminants, the deposition of insoluble sediments in water, including microorganisms. A decrease in water temperature inhibits the self-purification process, and ultraviolet radiation and an increase in water temperature accelerates this process.
From chemical factors self-purification should be noted oxidation of organic and inorganic substances. Often, an assessment of the self-purification of a reservoir is given by the biochemical oxygen demand (BOD) and by specific compounds in the water - hydrocarbons, resins, phenols, etc.
Sanitary regime A body of water is characterized primarily by the amount of oxygen dissolved in it. It should be at least 4 mg/l at any time of the year.
TO biological factors Self-purification of water bodies includes the proliferation of algae, mold and yeast fungi in the water. In addition to plants, representatives of the animal world also contribute to self-purification: mollusks, some types of amoebas.
Self-purification of contaminated water is accompanied by an improvement in its organoleptic properties and freedom from pathogenic microorganisms. The speed of self-purification depends on the degree of water contamination and the season of the year. With slight contamination, the water generally purifies itself in 3-4 days.
Pollution of the reservoir with chemicals (nitrogen, phosphorus), aromatic hydrocarbons and petroleum products has a negative impact on the self-purification process. Self-purification of water from oil lasts for a long time (months, and on rivers with low current even years).
Sanitary rules suggest choosing water supply sources in the following order:
1. Interstratal pressure (artesian) waters.
2. Interlayer free-flow waters.
3. Groundwater.
4. Open reservoirs.
1. By what system does water renewal occur during its cycle?
2. What does intracellular and extracellular water mean?
3. What essential functions What does water do in the body?
4. How much liquid should a person consume per day?
5. What conditions are necessary for the spread of infectious diseases through water?
6. How do you determine whether the water in your home is soft or hard?
7. What are the consequences of drinking water with increased hardness?
8. What consequences does the increased content of nitrates in water bodies lead to?
9. How do nitrosamines affect the human body?
10. What is the importance of mineral waters?
II. What percentage of all the Earth's waters is suitable for drinking?
Epidemiological significance of soil is that in it, despite the antagonism of soil saprophytic microflora, pathogens of infectious diseases can remain viable, virulent and pathogenic for quite a long time. Thus, in the soil, especially in its deep layers, typhoid Salmonella can survive up to 400 days. During this time, they can contaminate underground water supplies and infect humans. Not only pathogenic microorganisms, but also viruses can persist in the soil for quite a long time.
Spores of anaerobic microorganisms, which are constantly found in the soil of populated areas, persist in the soil for a particularly long time (20-25 years). These include the causative agents of tetanus, gas gangrene, botulism, and anthrax. A long stay in the soil of these pathogenic microorganisms and their spores is the cause of the occurrence of corresponding infectious diseases when contaminated soil enters a human wound or the consumption of contaminated food products.
Contaminated soil can act as a factor in the transmission of pathogens of both anthroponotic and zoonotic infections to humans. Among anthroponotic ones are intestinal infections of a bacterial nature (typhoid fever, paratyphoid A and B, bacterial and amoebic dysentery, cholera, salmonellosis, escherichiosis), viral etiology (hepatitis A, enteroviral infections - polio, Coxsackie, ECHO) and protozoal nature (amoebiasis , giardiasis). Zooanthroponoses that can spread through the soil include: leptospirosis, in particular the anicteric form, water fever, infectious jaundice, or Vasiliev-Weil disease, brucellosis, tularemia, anthrax. Mycobacterium tuberculosis can also be transmitted through soil. The role of soil in the transmission of helminthic infestations (ascariasis, trichocephalosis, diphyllobothriasis, hookworm disease, strongyloidiasis) is especially great. These infections and infestations are characterized by a fecal-oral transmission mechanism, which is the leading mechanism for intestinal infections, and one of the possible ones for others.
Fecal-oral mechanism of transmission of infectious diseases through the soil - a multi-stage process characterized by a sequential alternation of three phases: release of the pathogen from the body into the soil; presence of the pathogen in the soil; the introduction of a pathogen into a species-determined organism of a biological host and comes down to the following. Pathogenic microorganisms or eggs of geohelminths with the excrement of a sick person or carrier of infection or a sick animal (in zooanthroponotic infections) enter the soil, in which they retain viability, pathogenic and virulent properties for some time. While in the soil, pathogens of infectious diseases can enter the water of underground and surface sources, and from there into drinking water, from which they enter the human body. In addition, pathogens can get from the soil onto vegetables, berries and fruits, and onto your hands. They are also spread by rodents, flies and other insects.
There is a known case of an epidemic of typhoid fever that affected 60% of pupils in 36 days kindergarten. Sand on playgrounds turned out to be contaminated. Typhoid fever pathogens entered children's bodies through sand-contaminated hands. There is evidence of the penetration of typhoid and dysentery pathogens from contaminated soil into groundwater, which led to outbreaks of intestinal infections in the population who used well water.
It should be noted that anthrax spores, mycobacterium tuberculosis, polio viruses, Coxsackie and ECHO, and the causative agents of some other respiratory tract infections can spread with soil dust, i.e., by airborne dust, causing corresponding infectious diseases. In addition, people can become infected with anthrax through direct contact with contaminated soil (through broken skin).
Spore-forming clostridia enter the soil mainly with animal and human excrement. Clostridium botulism spores are found not only in cultivated but also in uncultivated soil. They were isolated in soil samples from California (70% of cases), the North Caucasus (40%), they were found in the coastal zone of the Azov Sea, in silt and sea water, on the surface of vegetables and fruits, in the intestines of healthy animals, fresh red fish (sturgeon, beluga, etc.), in the intestines (15-20%) and in the tissues (20%) of sleeping fish. Violation of food processing technology at enterprises Food Industry and at home, especially canned vegetables, meat and fish, as well as when smoking and salting fish, making sausages leads to the proliferation of botulism bacillus and the accumulation of botulinum toxin. Eating such foods leads to the development of a serious illness with symptoms of damage to the central nervous system.
Spores of the causative agents of tetanus and gas gangrene enter the human body through damaged skin and mucous membranes (small, usually puncture wounds, abrasions, splinters, through necrotic tissue in burns). Soil and soil dust in tetanus are one of the factors of transmission of infection.
Soil plays a specific role in the spread of geohelminthiasis - ascariasis, trichuriasis, hookworm, strongyloidiasis. The (immature) eggs of Ascaris lumbricoides, Trichiuris trichiura, Ancylostoma duodenale and Stronguloides stercoralis released into the soil are not capable of causing invasion. Optimal conditions for the development (ripening) of eggs in the soil are created at a temperature of 12 to 38 ° C, sufficient humidity and the presence of free oxygen. Depending on the conditions, the maturation of geohelminth eggs lasts from 2-3 weeks to 2-3 months. Only after this do they become invasive, that is, capable of causing illness when entering the human body through contaminated hands, vegetables, fruits and other food products. Geohelminth eggs, falling on the soil surface, die, but at a depth of 2.5 to 10 cm, protected from insolation and drying, they remain viable, according to the latest data, for up to 7-10 years.
The epidemiological significance of soil also lies in the fact that soil contaminated with organic substances is a habitat and breeding place for rodents (rats, mice), which are not only carriers, but also sources of many dangerous zooanthroponoses - plague, tularemia, leptospirosis, rabies.
In addition, flies live and breed in the soil, which are active carriers of pathogens of intestinal and other infectious diseases.
Finally, natural disinfection of wastewater and waste from the pathogenic microorganisms and helminths they contain can occur in the soil.
Soil is a natural environment for the neutralization of liquid and solid household and industrial waste. This is the life support system of the Earth, that element of the biosphere in which detoxification (neutralization, destruction and transformation into non-toxic compounds) of the bulk of exogenous organic and inorganic substances entering it occurs. According to the famous hygienist of the 19th century. Rubner, soil is "... the only place that satisfies all the requirements and is given by nature itself for the neutralization of pollution. But its detoxification ability has a limit, or threshold, of ecological adaptive capacity." When the threshold of the ecological adaptive capacity of the soil is exceeded, the values of natural self-purification processes characteristic of a given type of soil are violated, and it begins to release biological and chemical pollutants into plants, atmospheric air, surface and groundwater, which can accumulate in environments in contact with the soil in quantities dangerous to the soil. health of people, animals and plants.
Organic substances that enter the soil (proteins, fats, carbohydrates of plant residues, excrement or carcasses of animals, liquid or solid household waste, etc.) decompose until the formation of inorganic substances (mineralization process). In parallel, in the soil there is a process of synthesis from organic waste substances of a new complex organic substance of the soil - humus. The described process is called humification, and both biochemical processes (mineralization and humification), aimed at restoring the natural state of the soil, are its self-purification. This term also refers to the process of liberating soil from biological contaminants, although in this case we should talk about natural processes of its disinfection. As for the processes of self-purification of soil from ECS, it is more correct to call them processes of soil detoxification, and all processes together - processes of soil neutralization. G
Soil self-purification process removal of foreign organic matter is very complex and is carried out mainly by saprophytic soil microorganisms. Penetration of nutrients necessary for existence into the microbial cell occurs due to osmotic absorption through small pores in the cell wall and cytoplasmic membrane. The pores are so small that complex molecules of proteins, fats and carbohydrates do not penetrate through them. Only when complex substances are broken down into simpler molecules (amino acids, monosaccharides, fatty acids) can nutrients enter the microbial cell. To implement this method of nutrition, in the process of evolution, microorganisms have developed the ability to release hydrolytic enzymes into the environment, which prepare the complex substances contained in it for assimilation by the microbial cell. All enzymes of microorganisms are divided into two groups according to the place of their action: exoenzymes that act outside the cell, and endoenzymes that act inside the cell. Exoenzymes are involved in preparing nutrients for entry into the cell, and endoenzymes contribute to their absorption. The nature of the action of enzymes is different. Esterases (lipases), which break down fats, are found in many molds and bacteria. Proteases that break down protein molecules are secreted by many putrefactive bacteria, etc.
