From Big Medical Encyclopedia

WATER (H 2 O) — oxide of hydrogen. It is eurysynusic in the nature century. V.'s number in the World Ocean apprx. 1,4 billion km 3 , in underground sources — 60 million km3, in lakes — 0,75 million km 3 , in the rivers — 0,0012 million km 3 . The sea V. differing in high salinity makes 95,5% of all water resources of the planet. All natural waters are closely connected among themselves, forming continuous circulation.

The total quantity of water stocks of our country considerably exceeds water resources of other countries. In the territory of our country distribution of water resources very unevenly proceeds apprx. 200 000 rivers 3 000 000 km long, however: 85% of drains to the ocean are the share of the rivers flowing across the territory of sparsely populated areas. It is counted that at an average drain (per capita), equal 20 thousand m 3 in a year, in the southern areas the size of a drain decreases to 0,3 — 1,5 thousand m 3 , for the basin of the Black Sea it is equal to 1,9 thousand m 3 in a year. More than a half of volume of V., to-ruyu bear the rivers, it falls on time of floods. The drain of the Po River is uneven to years.

Physical and chemical properties.

Century — the simplest and most widespread compound of hydrogen and oxygen in the nature. Weight is 1 cm 3 Century at 0 ° weight of 1 cm is equal to 0,999968 g, 3 ice — 0,91674 g; t ° kip at 760 mm of mercury. t ° is equal 100 °, froze at 760 mm of mercury. — 0 °, density at 4 ° — 1,0, at 10 ° — 0,999727; density of ice at 0 ° — 0,9168; the specific heat of V. at 15 ° — 1,0 kcal, ice at 0 ° — 0,487 kcal; surface intention at 20 ° — 72,7 dynes/cm (1 dynes/cm = 10 - 3 N/m); viscosity at 0 ° — 1,789, at 20 ° — 1,002 centipoise (1 spz — 10 - 3 Н×сек/м 2 ); dielectric permeability at 0 ° — 87,8, at 18 ° — 80,1, at 25 ° — 78,3; specific conductivity of pure V. at 0 ° — 1,47×10 - 8 , at 18 ° — 4,41×10 - 8 , at 50 ° — 18,9×10 - 8 ohm - 1 ×см - 1 .

Pure V. very badly carries electric current, but the nek-swarm has measurable conductivity, edges is explained by insignificant dissociation of V. H and OH-ions. In 1 l of V. (t ° 25 °) only one ten-million share breaks up to ions (10 - 7 ) gram molecule, forming equal number of H+ and OH-of ions, i.e. [H + ] = [OH - ] = 10 - 7 g ion/l. The work of concentration of hydrogen and hydroxylic ions at a constant temperature is a constant and is called ionic product of V., is expressed in a g ion/l:

[H + ] × [OH - ] = 10 - 7 ×10 - 7 = 10 - 14 ,

[H + ] × [OH - ] = 10 - 14 .

At temperature increase from 0 to 4 ° V.'s density increases, and higher than 4 ° decreases. Melting of ice is followed not by expansion, but compression, at the same time there is a big increase in specific heat. It is capable to absorb a significant amount of heat energy century, without being exposed to big heating. This property is used in the water heating or cooling systems.

Is universal solvent firm century, liquid and gases and participates as Wednesday in the majority of the chemical reactions happening in the nature and an organism. Abnormal properties B. are explained by features of its structure. In a molecule B. both atomic nuclei of hydrogen form with an atomic nucleus of oxygen a corner apprx. 106 °. Because of asymmetry of a structure of a molecule B. has sharply expressed dipolar property and it is capable to form addition products. So, the structure of ice is presented in the form of network of the crossed chains of the molecules B. connected by hydrogen bindings. Liquid V. represents mix of two structures. One of them are fragments of a little spoiled structure of ice, another — strongly spoiled structure of ice, in a cut the most part of hydrogen bindings is destroyed.

Along with the molecules B. having usual a pier. the weight 18,0160, the molecules containing a deuterium, hyzone, heavy isotopes of oxygen meet. Such V. is called heavy. The quantity of molecules of heavy V. in natural sources does not exceed 0,02%. On physical. to properties heavy V. differs from ordinary. Data on heavy V.'s action on an organism are contradictory.

The hygienic characteristic

Depending on the content of salts of alkaline earth metals (calcium and magnesium) causing V.'s rigidity distinguish V. soft, moderately rigid and rigid. GOST 2874 — 73 allows in drinking water total hardness no more than 7 mg-ekv/l. In exceptional cases in coordination with bodies a dignity. supervision big rigidity of V., but not higher than 10 mg-ekv/l is admissible.

On the nature of use distinguish V. drinking, technical, etc. The most high requirements are imposed to drinking V.: it shall not contain pathogenic bacteriums, viruses, eggs of helminths, toxic agents in the quantities capable to cause any adverse changes in an organism.

By origin natural waters subdivide on atmospheric (a rain, snow, etc.), underground (soil, soil, interbedded), superficial fresh (waters of the rivers, lakes, ponds, water reservoirs) and sea.

Gigabyte. V.'s characteristic of various origin is not identical. Atmospheric V. in areas with an uncontaminated air is rather pure, in areas with a polluted air may contain a significant amount of dust, soot and other impurity. Atmospheric V. can sometimes be used for the economic and drinking purposes.

General scheme of a bedding of underground waters: 1 — the water-bearing horizon of interreservoir pressure waters (artesian); 2 — the water-bearing horizon of interreservoir free-flow waters; 3 — the water-bearing horizon of subsoil waters; 4 — the well feeding on a subsoil water; 5 — the well feeding on interreservoir free-flow water; 6 — the well feeding on interreservoir pressure (artesian) water. Shooters showed penetration of surface waters into the water-bearing horizons.

Underground waters collect as a result of filtering of an atmospheric precipitation through the soil and waters of superficial sources through their bed. Ground underground waters are located at the Earth's surface, not protected almost from pollution, their volume is changeable, for water supply interest is not of.

Subsoil underground waters are located in the water-bearing horizon (a layer of water-permeable, moisture capacious or not moisture capacious breed, watered) on waterproof layer, the first from the Earth's surface. Subsoil waters belong to not pressure head, are widely used as power supplies of wells and wells. Replenishment of reserves of these waters happens due to filtering of surface waters from the big areas of a zone of food. The composition of ground waters is quite steady. At the correct operation of the water-bearing horizon and at observance of requirements a dignity. protection of a zone of food and the place of a water intake subsoil waters can be used for the economic and drinking purposes.

Interreservoir waters are located in the water-bearing horizons placed between two waterproof layers. In certain cases interreservoir waters are under pressure, and V. in the wells eating from these water-bearing horizons rises to the level corresponding to a pressure of the horizon. Features of an arrangement of subsoil and interreservoir waters are shown in the drawing. Replenishment of reserves of interreservoir waters happens in places of an exit (wedging out) to a surface of the water-bearing horizon. The composition of these waters, as a rule, differs in big constancy. They are well protected from direct pollution from a surface and can serve for hozyaystvennopityevy water supply.

Considerable fluctuations of chemical structure and temperature of underground waters are the indicator signaling about danger of pollution of the water-bearing horizon.

Surface waters are concentrated in fluid and standing reservoirs. Fluid reservoirs (rivers) contain V.'s stocks which are filled up by atmospheric drains and underground waters. Unlike underground, surface waters are characterized by rather smaller constancy of chemical players which are changed depending on an atmospheric precipitation on seasons of year. Surface waters differ in the low content of salts and a significant amount of the weighed and colloid substances.

Century in standing reservoirs (lakes, ponds) the hl is replenished. obr. due to inflows and an atmospheric precipitation, but also their underground food is possible. Owing to almost total absence of the movement B. of pollution, coming to standing reservoirs, constitute big danger.

A specific place is held by artificial water reservoirs (see), the movements B. which are characterized by very small speeds

Value of water for a human body

contains In an organism of the adult apprx. 65%B. The organism is younger, the it is more ud. V.'s weight in its structure. So, the 6 weeks embryo contains 97,5% of V., in a newborn organism — 70 — 83%. Is a part of all tissues of human body century: in its blood apprx. 81%, in dense tissues (muscle) — 75%, in bones — apprx. 20%. V.'s role as environments for the chemical reactions which are made in the course of a metabolism is big. In fluid medium there is a digestion of food and absorption in blood of nutrients. Every day went to a gleam. - kish. a path 1500 ml of saliva, 2500 ml of a gastric juice, 700 ml of juice of a pancreas, 3000 ml of intestinal juice are allocated. By means of V. harmful products of exchange are brought out of an organism. Century in an organism can be the free (mobile), making a basis extracellular and intracellular liquid; the constitutional, entering component in molecules of proteins, fats and carbohydrates; the colloid systems connected, being a part.

The adult uses on average 2,5 l of V. a day. From this number of 1,2 l 1,0 l — of V. which arrived with food and 0,3 l — on V. are the share of drinking V., edges it is formed in the organism in the course of a metabolism. The same number of V. is brought out of an organism: through kidneys apprx. 50% of this volume, with then through skin — 32%, with expired air through lungs — 13%, through intestines — 5%.

V.'s lack of an organism is hard transferred by the person (see. Dehydration of an organism ).

V.'s surplus leads to an overload of cardiovascular system, causes exhausting sweating (see), followed by loss of salts and water-soluble vitamins, weakens an organism.

In the course of evolution in an organism the difficult and thin mechanism providing a normal water balance was developed. At a lack of V.'s organism there is a feeling of thirst which is expressed a peculiar feeling of dryness in oral cavities and throats. It was experimentally shown that the center regulating water exchange is localized in a trunk part of a brain. Disturbance of optimum ratios between V., salts and organic matters of blood therefore the osmotic pressure of liquid of an organism (increases see is the main reason for emergence of thirst. Water salt metabolism ).

Sanitary and hygienic requirements

V. is necessary for drink, and also for various economic and household and utility needs of the population (see. Water supply ). Quality of V. received by the population by means of the decentralized water handling is defined by all-hygienic requirements which bases were developed by F. F. Erisman. The indicators characterizing epidemiol have the greatest value. danger of Century. The close attention is paid to organoleptic indicators since V. with off-flavor, taste, muddy, color even if it also does not constitute direct health hazard, will not be used by the population. As for chemical structure of V., at its assessment it is necessary to consider local features of formation of a water source. So-called indirect indicators of pollution of V. the garbage constituting danger in epidemiol, the relation are taken into account: biogenic elements (ammonia, nitrates, nitrites), chlorides, organic matters, etc. The data of sanitary and topographical inspection of a water source allowing to receive data on V.'s reliability about a dignity have huge value. - epid, positions (see. Sources of water supply ). A. A. Minkh (1971) recommends to use the following indicative standards at assessment of V. received from mine and boring wells: transparency — not less than 30 cm; chromaticity on a scale — no more than 40 °, a smell and smack — no more than 2 — 3 points, total hardness — to 14 mg-ekv/l, the content of fluorine — to 1,5 mg/l, the content of nitrates — to 10 mg/l (on nitrogen), the content of nitrites — to 0,002 mg/l, the content of ammonium salts - — to 0,1 mg/l, oxidability — to 4 mg/l of O 2 , microbic number 300 — 400 in 1 ml, a coli-index — not less than 100 ml, a coli-index — no more than 10 (see. Coli-index, coli-index , Microbic number ).

Requirements to V. arriving to the population through system of the centralized water supply (see. Water supply system ), GOST 2874 — 73 are normalized. This GOST provides indicators, the general for all water supply systems. According to GOST 2874 — 73 began to smell also V.'s smack at 20 ° shall not exceed 2 points, chromaticity on a scale — no more than 20 °, a turbidity on a standard scale — no more than 1,5 mg/l, total hardness — no more than 7 mg-ekv/l. GOST are established extreme concentration: for lead — no more than 0,1 mg/l, arsenic — no more than 0,05 mg/l, fluorine — from 0,7 to 1,5 mg/l, copper — no more than 1,0 mg/l, zinc — no more than 5,0 mg/l. In GOST it is specified that admissible concentration of other harmful substances is established in each separate case by the Chief health officer of the USSR. The great value is attached bacterial, to indicators: total number of bacteria shall not exceed 100 in 1 ml, a coli-index — no more than 3. For water supply systems in which various methods of processing of V. are used, implementation of additional requirements is provided: lack of chlorphenolic smells, content of residual chlorine in the next point from the pump station — from 0,3 to 0,5 mg/l, the content of iron — no more than 0,3 mg/l etc.

For those cases when V. of a source does not conform to requirements of GOST 2874 — 73, a dignity. the legislation recommends to be guided by GOST 2761 — 57 «Sources of the centralized economic and drinking water supply», and also «Rules of protection of surface waters from pollution by drain waters». These documents allow to receive the answer to a question whether it is possible usual means, to-rymi the water equipment has, to bring initial V. to quality drinking and whether this task (is real see. Neutralization of water , Disinfecting of water ).

The source can be used for economic and drinking water supply if V.'s quality in it conforms to the following requirements: the size of a solid residue — no more than 1000 mg/l, the content of sulfates — no more than 500 mg/l, chlorides — no more than 350 mg/l, the size of total hardness — no more than 7 mg-ekv/l. Content of salts of group of heavy metals, radioelements and other harmful substances shall not exceed maximum allowable concentration. Use of water sources which V. has a smell and smack, intensity the exceeding 2 points is considered inadmissible; content of iron (total) in V. of underground sources shall be no more than 1 mg/l.

Hygienic control

researches of its organoleptic indicators and chemical structure are made For hygienic evaluation test of V., used also bacterial., gelmintol., virusol. and gidrobiol. methods of a research. GOST 2874 — 73 defines an order and contents a gigabyte. control of quality V. Posledny shall be carried out according to the special plan of SES.

Frequency of laboratory researches B. from sources is defined by degree their dignity. reliability. At waterworks the research B. shall be made after each stage of its processing. In the course of control of distribution network of test are selected from outside water analyses and cranes of internal water supply systems and in the most characteristic points of network: the next to the pump station, the most remote, the most sublime, at the deadlocks and points raising special doubts in the relation of quality of V. Kolichestvo of tests is established depending on the number of the people using this water supply system.

Gigabyte. control of subjects to the centralized and decentralized water supply is among the most important sections in activity of health officers. In the course of visit and check of these objects representatives dignity. supervision reveal defects in a dignity. a state and the maintenance of water handling also put forward necessary a dignity. - a gigabyte. requirements.

To number of the main documents, to-rymi shall be guided a dignity. bodies in the course of precautionary supervision of water supply, belong first of all «Bases of the water legislation of USSR and federal republics». In this major document ways of improvement and a dignity are accurately defined. protection of water sources of our country. «Bases» prohibit commissioning of the new and reconstructed enterprises, utility and other objects which are not provided with the devices preventing harmful effects of drains on water sources. «Bases» provide obligation of careful attitude to water resources.

Current dignity. supervision of subjects to water supply is exercised according to «The instruction about work of the health officer on housing-and-municipal sanitation of SES». Great importance of work in the area a dignity. supervision of water supply it is emphasized in the special order M3 USSR «About strengthening of sanitary inspection behind water supply and channeling of the inhabited places and sanitary protection of reservoirs».

Influence of composition of water on living conditions and health of the population

Water of natural sources always contains a nek-swarm the number of various chemical connections, various microbic flora, eggs of helminths, viruses which can become the reason of intoxications, and also diseases of local and epidemic character.

The structure and properties of microorganisms of water sources studies a dignity. microbiology. The aqueous medium has a number of the features favorable for life of microorganisms: availability of the dissolved salts, rather constant temperature, etc. Along with it the microbes getting to a water source meet influence of some negatively influencing factors (ultraviolet radiation, a lack of feedstuffs, the competition of natural inhabitants of a water source). Therefore in water sources saprophytic microorganisms prevail. Among them there can be cocci, bacilli, spirochetes, viruses, fungi, etc.

Among the chemical connections which are found in natural water sources there can be substances possessing toxic action (compounds of chrome, arsenic, cyanide, pesticides, etc.) - As a rule, the content of harmful substances in a reservoir is not enough, but these trace amounts are entered into an organism systematically throughout long time. In most cases in reservoirs there is not one, and several toxic agents that strengthens their action on an organism.

From 50th years there was a danger of pollution of water artificial radioisotopes which can kumulirovatsya in some bodies and to become the reason hron, radiation injury. This danger does especially important protection of natural waters from pollution by radioactive materials.

Can become soiled carcinogenic substances and among them most often century polycyclic aromatic hydrocarbons which content increases parallel to growth of the general pollution of the used waters. Along with them at V. there can be carcinogenic substances of other structure. Serious fears are caused by a possibility of pollution of natural waters of a nitrozoaminama. Biol, by researches it is established that possess cancerogenic action dialkyl, alkyl, aryl, diaryl and various cyclic nitrozoamina, and also a number of nitrozoamid. Arylamines at which the NH2 group is located in an aromatic ring are cancerogenic it is equivalent to the second situation in naphthalene or in parasituation in bifenilny connection.

In water there can be also substances strengthening blastomogenic effect of carcinogens (cocarcinogens), in particular synthetic poverkhnostnoaktivny substances which concern to group of cocarcinogens.

Pollution of natural waters pesticides among which very poisonous drugs, such as hexachlorane, polychlorpinene, heptachlor, etc. (occur see can constitute big danger. Pesticides ).

Among substances, even phenol, oil and oil products are most spread in the most trace amounts worsening organoleptic properties B. Phenol at V.'s chlorination forms stable compounds (chlorphenols) possessing a strong specific smell. Getting to a reservoir, oil and oil products spread on a surface, last cuts settle on a bottom, easy — are dissolved in Century. Crude oil emulsions are evenly distributed in a layer of Century. For film formation on V.'s surface enough minute quantities of oil. Threshold concentration on a smell for the majority of oil products make 0,3 mg/l, for polysulphide nefty — 0,1 mg/l. The threat to health of the population connected with pollution of reservoirs puts forward a problem of protection of natural waters against pollution as a first-priority public task.

Century of natural sources can serve as an etiological factor of emergence of some hron, noninfectious diseases. And. P. Vinogradov (1938 — 1949) created the doctrine about biogeochemical provinces — areas with a ratio of microelements, adverse for an organism, in objects of the environment (the soil, water, plants) where local diseases, specific to this area, develop. Is among natural endemiya fluorosis (see). An endemia of a fluorosis are widespread quite widely. So, according to R. D. Gabovich and G. D. Ovrutsky (1969), about one thousand messages on the local centers of a fluorosis in different districts of our planet are published. In the USSR the centers of a fluorosis in a number of the areas of RSFSR, USSR, and also in Georgia, Azerbaijan, Moldova, Kazakhstan are studied (S. V. Moiseyev, 1938; T. A. Nikolaeva, 1949; A. N. Krepkogorsky, 1958; R. D. Gabovich, I. V. Babel, 1968, etc.). Some data on dependence of its distribution on the content of fluorine in water are presented in table 1.

Along with the materials characterizing fluorine as the element promoting development of a fluorosis are available this, testimonial that fluorine can play a role of the anticarious agent. Anticarious effect of fluorine was studied in an experiment in detail and shown in the observations made in the settlements which are supplied with V. which is artificially enriched with fluorine (see. Fluoration of water ).

In the biogeochemical provinces poor in iodine, the disease of a local craw is widespread (see. Craw local ). It is known that the daily need of an organism for iodine makes 120 — 200 mkg. With water no more than 15 — 20% come to an organism. Thus, not poverty of V. is iodine the main reason of development of a local craw, and a lack of iodine of food. However on the content of iodine in V. it is possible to judge existence of this microelement in the soil, plants, milk, meat of domestic animals. Therefore, the content of iodine in V. has alarm value.

Also urovsky disease is among local diseases (see. Kashina-Beck disease ), meeting in East Asia. Most of researchers connects it with features of structure of V. or the soil. Value for chemical structure of V. of such microelements as strontium, nickel, boron, cobalt, selenium, bromine, silver, molybdenum, manganese, etc. is studied. This results from the fact that representation about biol extended, roles of microelements, use for the economic and drinking purposes of the underground waters which are quite often containing the increased quantity of various microelements considerably increased; at last, the range of sensitive methods of definition of microelements in external environment extended.

According to the nature of action on an organism the studied microelements can be divided into microelements which influence is connected with their surplus — molybdenum, selenium, boron, nickel and others or these by a shortcoming — iodine, copper, cobalt (see. Microelements ).

In areas with hard waters disturbance of purine and calcic exchange, increase in content of calcium in urine, reduction of a daily urine, atsidotichesky shift in urine and other changes showing that in an organism predisposition to formation of an urolitiazis is created is sometimes observed.

The use of V. containing the increased amount of sodium chloride is considered as one of the factors promoting development of hypertensive states now. The increased amount of nickel and boron in V. causes change of activity of intestinal enzymes and promotes development of subacid states.

The question of influence of nitric nitrogen underwent attentive studying. The last contains in uncontaminated waters in the quantity which is not exceeding 0,1 mg/l. Since the time of F. F. Erisman was considered that nitric nitrogen can serve only as the indicator of old pollution of V. protein-bearing garbage. Therefore as the indirect indicator of organic pollution of V. nitric nitrogen did not testify to serious danger in epid, the relation; direct action on an organism of big concentration of nitric nitrogen (to 30 — 40 mg/l) was denied. However in 40 — the 50th years 20 century separate messages that as a result of dilution of food mixes B., containing large amounts of nitrates, babies can have diseases connected with development appeared methemoglobinemias (see). It was established that at the diseased the nitrate methemoglobinemia observed the reduction of gastric acidity preceding this state and development of the dispeptic phenomena. These states are some kind of premises for change of the hemoglobin content occurring under the influence of nitrites. The last are formed as a result of life activity of nitratvosstanavlivayushchy microflora (colibacilli, stafilokokk, etc.). edges can get in went. - kish. a path with contaminated drinking Century. Detailed studying of conditions of emergence of a nitrate methemoglobinemia showed that this disease can develop not only at babies, but also at children of advanced ages. It formed the basis for inclusion in GOST 2874 — 73 requirements of an upper limit of admissible content of nitrates in V. at the level of 10 mg/l.

Biogeochemical provinces with a ratio, adverse for an organism, and other microelements in the environment are known. So, in areas poor in cobalt an acobaltosis, hypo - and avitaminosis of B12 meets; in areas rich with boron local enterita of the cattle are noted; in areas there is a lot of nickel at page - x. animals cases of «a nickel blindness» meet; in the areas rich with molybdenum, urine of animals contains the increased quantity uric to - you; in the areas rich with copper, anemia of page is observed - x. animals; in areas a lot of selenium is registered «an alkaline disease» of the cattle. Local diseases of the population are well studied only in cases of a lack of iodine, a shortcoming and excess of fluorine. However lack of the expressed endemiya in areas where are observed enzooty of page - x. animals, it is impossible to consider as lack of influence of microelement structure of V., adverse for the person, and food.

Thus, the question of influence of chemical structure of V. on the state of health of the population and on function of an organism of people needs further studying.

Water as the habitat

Water as the habitat of various organisms is characterized by a number of features: gas structure, salinity, factor of pressure, temperature schedule, fluctuations of a light status. Oxygen gets into V. from air, without mixing up with it and without forming any connections. Partially V. is enriched with oxygen as a result of process of photosynthesis, nevertheless it contains oxygen 30 times smaller, than air. Water organisms the oxygen which is generally dissolved in V., in most cases all body surface breathe, is more rare by means of the branchiate device. Some vertebrata (whales, turtles, snakes) who are for the second time water kept air breath. Get into V. and other gases of the atmosphere, forming the so-called underwater troposphere. These gases are necessary for the normal course of vital processes of aquatic organisms.

Oceanic and sea V.'s salinity fluctuates from 37 — 38%0 (The Mediterranean and Red seas, the Persian Gulf) to 5 — 13% about (The Azov and Caspian seas). Fresh-water reservoirs have rather low content of salts. It causes distinctions of flora and fauna of sea and fresh-water reservoirs. Internal environment of aquatic organisms in the sea of an izotonichn or poorly a gipertonichn. Internal environment of fresh-water invertebrates in relation to water of a gipertonichn. Sea fishes (except cartilaginous) have gipotonichny, and fresh-water generally gipertonichny internal environment. Turgor of algas is increased. Lack of vacuoles is characteristic of sea protozoa.

Temperature variations of an aqueous medium have much smaller amplitude, than temperature variations of the air environment. Water, in particular sea, Wednesday in general is characterized by stability of a temperature schedule and its weak fluctuations.

The light status of an aqueous medium is characterized by what in the seas and oceans of 90% of body of water is in a full gloom.

The population of an aqueous medium on a behavior pattern and distributions in body of water is subdivided into two biol, groups: inhabitants of thickness of waters — pelagos, inhabitants of a bottom — benthos (see). In turn pelagos includes representatives plankton (see) and nekton (set of water animals, actively floating and overcoming force of a current). The organisms capable to lead alternately a pelagic, benthic life, treat group of a pelagobentos.

A pelagic zone, for a cut existence of a sunlight and lack of substrate is characteristic, inhabit the floating and soaring forms. The small sizes of a body, strong flattening or a partition of a body therefore its surface increases are characteristic of planktonts and buoyancy increases. Decrease in specific weight is reached by a reduction of skeletal educations, removal from a body of heavy products of metabolism and accumulation of substances with a small ud. it is powerful, e.g. fat. Increase in buoyancy is reached by existence of gas vacuoles. The movement in the thickness of V. is carried out by means of flagellums, cilia, the active movements of extremities and trunks, a reactive way. Vertical migrations as a result of change ud are characteristic. body weight, connected with change of illumination, temperature, the gas mode and salinity. In sea phytoplankton a specific place is held by one-celled seaweed, and in zooplankton — foraminifera, radiolarias, coelenterates, some groups of worms, etc.

The streamline shape of a body, a specific structure of integuments, mucifying on a body surface is characteristic of organisms of nekton. The movement happens generally to the help of fins and a reactive way. Horizontal migrations have fodder, spawning and zimovalny character. Oxygen absorption, dissolved in V., happens to the help of special bodies — a zhaber, tracheas, lungs. In case of sharp deterioration in the respiratory environment these organisms are capable to move actively to considerable distances in search of other conditions. Fishes, squids and marine mammals treat nektonny animals.

Benthic organisms live on the surface of soil and in its thickness. Adaptation of aquatic organisms to such way of life consists in development of ability to deduction in a certain place, to protection against burial by the substances accumulating on a bottom, and in necessary cases and to migrations. Protection against backfilling by the accumulating substances is carried out at the expense of a pulling of a body or an attachment to the objects towering over soil.

Density of an aqueous medium causes a possibility of existence of organisms without strong cover or skeletal education. Also forms of food of ground organisms are peculiar. Not movably or polupodvizhno attached, they eat plankton brought by water flows; organisms meet osmotic type of food (sea hedgehogs, ofiura, starfishes).

Various seaweed, in structure of a zoo-benthos — a sponge, coelenterates, worms, mollusks, erinaceouses, astsidiya, and also some fishes are a part of a phytobenthos.

The list of inhabitants of reservoirs, community of aquatic organisms is defined by features of an aqueous medium. Different forms of water organisms need various living conditions. Amplitude of change of this or that factor, to-ruyu it is capable to transfer this or that look, is called ecological valence.

On character biocenosis (see) it is possible to judge extent of pollution of a reservoir. Kolkvitts and Marsson (R. Kolkwitz, M. Marsson) suggested to divide all reservoirs on a scale of saprobity (grech, sapros rotten) on poly-, meso - and oligosaprobic. In polysaprobic reservoirs almost completely there is no oxygen, a significant amount contains hydrogen sulfide and carbon dioxide gas, there are nerazlo-being proteins. The number of the found types is limited, but the quantity of organisms (weight them) is very high. Mezosaprobny reservoirs share on alpha and beta mezosaprobnye. In an alpha mezosaprobnykh reservoirs the ammonia, amino acids testimonial of considerable pollution meet, but free oxygen already appears. Species composition of aquatic organisms is more extensive, than in polysaprobic reservoirs (a bacterium, blue-green, the elementary, rotifers, etc.). In a beta mezosaprobnykh reservoirs there is a lot of oxygen, but there are such products of proteinaceous disintegration as ammonia, nitrites and nitrates. Species composition of aquatic organisms is wider, but the number of organisms is small (diatomic, green, protococcal, etc.). In oligosaprobic reservoirs of V. differs in high degree of purity, but the mass of organisms is small.

It is offered to consider also for assessment of extent of pollution of reservoirs availability of toxicants in them. Depending on extent of pollution of reservoirs distinguish polimezo-and oligotoksobny zones (a toksobnost — property of organisms to exist in the waters containing toxicants).

Water as a spreading factor of causative agents of infectious diseases

in an extreme antiquity it was known that developing of infectious diseases is connected with consumption V. Hippocrates believed that crude V. is hazardous to health. During epidemic of cholera in 1849 in London I. Snow claimed that the flash happened owing to the use of V. containing sewage.

Epidemiol, a role of the contaminated V. was evidence-based by works of JI. Pasteur who found in it there are a lot of different microorganisms, and R. Koch who found in India in tanks for V. of cholera vibrioes.

Mechanisms and factors of infection of water. Causative agents of infectious diseases can get to water sources with the crude drains of infectious diseases hospitals, veterinary clinics, with sewer waters. Open reservoirs, besides, become soiled emissions of river crafts and storm waters.

Infection of people can occur if disease-producing factors in one way or another got to a reservoir, kept at the same time the viability in V. and the infected V. got into a human body.

Before the combination of such conditions met quite often, and as a result of it quite often there were water epidemics of intestinal infections. With development of technology of water supply, strengthening sanitary protection of reservoirs (see) danger of water epidemics considerably decreased. Though frequency and scales of water: flashes were reduced, nevertheless at strong pollution of V. and at disturbance a dignity. requirements in the course of its cleaning and V.'s disinfecting distribution of causative agents of infectious diseases by the waterway is possible. The possibility of secondary infection of V. in a distribution system of a water supply system is not excluded. There can easily be a pollution and microbic planting of V. at the decentralized water supply. Infection during the bathing in strongly contaminated reservoirs is possible.

Preservation of causative agents of infectious diseases in water. Distribution of causative agents of diseases of the waterway is favored by ability of a number of microorganisms quite long time to keep the viability in V. (tab. 2).

Great attention is deserved by danger of distribution by the waterway of various helminths. Can get into intestines of the person of egg of helminths under a condition if people drink the crude river V., wash it fruit and vegetables. Infection with helminths can occur also during bathing in the contaminated reservoir. The contaminated reservoirs promote distribution of activators schistosomatosis (see), diphyllobotriasis (see; etc.

Infection through V. is most probable at the decentralized type of water supply when V. is not exposed to disinfecting. Special danger is constituted by V.'s use for the drinking purposes from open reservoirs which easily are exposed to infection.

At the centralized water supply danger of distribution of causative agents of infections by the waterway can be reduced to zero.

Danger of spread of diseases of the waterway is most big concerning intestinal infections: cholera (see), typhoid (see), paratyphus (see), dysentery (see), etc. With water also activators of ikterogemorragichesky can be transferred hay fever (see), sapa (see), malignant anthrax (see), tuberculosis (see).

Prevention of distribution of causative agents of infections by the waterway consists first of all in strict a dignity. to protection of sources of the centralized and decentralized water supply, in observance a dignity. requirements to the device and operation of the constructions intended for a fence, processing, storage and distribution of Century.



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I. I. Belyaev.