Heavy metals are very dangerous toxic substances. Nowadays, monitoring the levels of various such substances is especially important in industrial and urban areas.
Although everyone knows what heavy metals are, not everyone knows which chemical elements still fall into this category. There are many criteria by which different scientists define heavy metals: toxicity, density, atomic mass, biochemical and geochemical cycles, distribution in nature. According to one criterion, heavy metals include arsenic (a metalloid) and bismuth (a brittle metal).
General facts about heavy metals
More than 40 elements are known that are classified as heavy metals. They have an atomic mass greater than 50 a.u. Strange as it may seem, it is these elements that are highly toxic even at low cumulation for living organisms. V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo…Pb, Hg, U, Th… they all fall into this category. Even with their toxicity, many of them are important trace elements other than cadmium, mercury, lead and bismuth for which no biological role has been found.
According to another classification (namely, N. Reimers), heavy metals are elements that have a density greater than 8 g / cm 3. Thus, there will be fewer of these elements: Pb, Zn, Bi, Sn, Cd, Cu, Ni, Co, Sb.
Theoretically, heavy metals can be called the entire periodic table of elements starting with vanadium, but researchers prove to us that this is not entirely true. Such a theory is due to the fact that not all of them are present in nature within toxic limits, and confusion in biological processes is minimal for many. This is why many include only lead, mercury, cadmium, and arsenic in this category. The United Nations Economic Commission for Europe does not agree with this opinion and considers that heavy metals are zinc, arsenic, selenium and antimony. The same N. Reimers believes that by removing rare and noble elements from the periodic table, heavy metals remain. But this is also not a rule, others add gold, platinum, silver, tungsten, iron, manganese to this class. That's why I'm telling you that it's still not clear on this topic...
Discussing the balance of ions various substances in solution, we will find that the solubility of such particles is related to many factors. The main solubilization factors are pH, the presence of ligands in solution, and redox potential. They are involved in the processes of oxidation of these elements from one oxidation state to another, in which the solubility of the ion in solution is higher.
Depending on the nature of the ions, various processes can occur in the solution:
- hydrolysis,
- complexation with different ligands;
- hydrolytic polymerization.
Due to these processes, ions can precipitate or remain stable in solution. The catalytic properties of a certain element and its availability for living organisms depend on this.
Many heavy metals form fairly stable complexes with organic substances. These complexes are part of the mechanism of migration of these elements in ponds. Almost all heavy metal chelates are stable in solution. Also, complexes of soil acids with salts of various metals (molybdenum, copper, uranium, aluminum, iron, titanium, vanadium) have good solubility in a neutral, slightly alkaline and slightly acidic environment. This fact is very important, because such complexes can move in the dissolved state over long distances. Most exposed water resources- these are low-mineralized and surface water bodies, where the formation of other such complexes does not occur. To understand the factors that regulate the level of a chemical element in rivers and lakes, their chemical reactivity, bioavailability and toxicity, it is necessary to know not only the total content, but also the proportion of free and related forms metal.
As a result of the migration of heavy metals into metal complexes in solution, the following consequences can occur:
- Firstly, the cumulation of ions of a chemical element increases due to the transition of these from bottom sediments to natural solutions;
- Secondly, there is a possibility of changing the membrane permeability of the resulting complexes, in contrast to conventional ions;
- Also, the toxicity of an element in the complex form may differ from the usual ionic form.
For example, cadmium, mercury and copper in chelated forms have less toxicity than free ions. That is why it is not correct to speak of toxicity, bioavailability, chemical reactivity only in terms of the total content of a certain element, while not taking into account the proportion of free and bound forms of a chemical element.
Where do heavy metals come from in our environment? The reasons for the presence of such elements may be wastewater from various industrial facilities involved in ferrous and non-ferrous metallurgy, mechanical engineering, and galvanization. Some chemicals are found in pesticides and fertilizers and thus can be a source of pollution for local ponds.
And if you enter into the secrets of chemistry, then the main culprit in the increase in the level of soluble salts of heavy metals is acid rain (acidification). A decrease in the acidity of the environment (a decrease in pH) entails the transition of heavy metals from poorly soluble compounds (hydroxides, carbonates, sulfates) to more readily soluble ones (nitrates, hydrosulfates, nitrites, bicarbonates, chlorides) in the soil solution.
Vanadium (V)
It should be noted first of all that contamination with this element by natural means is unlikely, because this element is very dispersed in the Earth's crust. In nature, it is found in asphalts, bitumens, coals, iron ores. Oil is an important source of pollution.
The content of vanadium in natural reservoirs
Natural reservoirs contain an insignificant amount of vanadium:
- in rivers - 0.2 - 4.5 µg / l,
- in the seas (on average) - 2 μg / l.
Anionic complexes (V 10 O 26) 6- and (V 4 O 12) 4- are very important in the processes of transition of vanadium in the dissolved state. Soluble vanadium complexes with organic substances, such as humic acids, are also very important.
Maximum allowable concentration of vanadium for the aquatic environment
Vanadium in high doses is very harmful to humans. The maximum allowable concentration for the aquatic environment (MAC) is 0.1 mg/l, and in fishery ponds, the MAC of the fish farm is even lower - 0.001 mg/l.
Bismuth (Bi)
Mainly, bismuth can enter rivers and lakes as a result of leaching processes of minerals containing bismuth. There are also man-made sources of pollution with this element. These can be glass, perfume and pharmaceutical factories.
The content of bismuth in natural reservoirs
- Rivers and lakes contain less than a microgram of bismuth per litre.
- But groundwater can contain even 20 μg / l.
- In the seas, bismuth, as a rule, does not exceed 0.02 µg/l.
Maximum allowable concentration of bismuth for the aquatic environment
Maximum allowable concentration of bismuth for the aquatic environment is 0.1 mg/l.
Iron (Fe)
Iron - chemical element not rare, it is contained in many minerals and rocks, and thus in natural reservoirs the level of this element is higher than other metals. It can occur as a result of weathering processes. rocks, destruction of these rocks and dissolution. Forming various complexes with organic substances from a solution, iron can be in colloidal, dissolved and suspended states. It is impossible not to mention the anthropogenic sources of iron pollution. Waste water from metallurgical, metal-working, paint and varnish and textile factories sometimes goes off scale due to excess iron.
The amount of iron in rivers and lakes depends on chemical composition solution, pH and partly on temperature. Weighted forms of iron compounds have a size of more than 0.45 μg. The main substances that are part of these particles are suspensions with sorbed iron compounds, iron oxide hydrate and other iron-containing minerals. Smaller particles, ie colloidal forms of iron, are considered together with dissolved iron compounds. Iron in the dissolved state consists of ions, hydroxocomplexes and complexes. Depending on the valency, it is noticed that Fe(II) migrates in the ionic form, while Fe(III) remains in the dissolved state in the absence of various complexes.
In the balance of iron compounds in aqueous solution, the role of oxidation processes, both chemical and biochemical (iron bacteria), is also very important. These bacteria are responsible for the transition of Fe(II) iron ions to the Fe(III) state. Ferric compounds tend to hydrolyze and precipitate Fe(OH) 3 . Both Fe(II) and Fe(III) are prone to the formation of hydroxo complexes of the – , + , 3+ , 4+ , + type, depending on the acidity of the solution. Under normal conditions in rivers and lakes, Fe(III) is associated with various dissolved inorganic and organic substances. At pH greater than 8, Fe(III) transforms into Fe(OH) 3 . Colloidal forms of iron compounds are the least studied.
Iron content in natural waters
In rivers and lakes, the level of iron fluctuates at the level of n * 0.1 mg/l, but can rise near swamps to several mg/l. In swamps, iron is concentrated in the form of humate salts (salts of humic acids).
Underground reservoirs with low pH contain record amounts of iron - up to several hundred milligrams per liter.
Iron is an essential micronutrient and is dependent on various important biological processes. It affects the intensity of phytoplankton development and the quality of microflora in water bodies depends on it.
The level of iron in rivers and lakes is seasonal. The highest concentrations in water bodies are observed in winter and summer due to water stagnation, but in spring and autumn the level of this element noticeably decreases due to mixing of water masses.
Thus, a large amount of oxygen leads to the oxidation of iron from the divalent form to the trivalent form, forming iron hydroxide, which precipitates.
Maximum permissible concentration of iron for the aquatic environment
Water with a large amount of iron (more than 1-2 mg / l) is characterized by poor taste. It has an unpleasant astringent taste and is unsuitable for industrial purposes.
The MPC of iron for the aquatic environment is 0.3 mg/l, and in fishery ponds the MPC of fish farms is 0.1 mg/l.
Cadmium (Cd)
Cadmium contamination can occur during soil leaching, during the decomposition of various microorganisms that accumulate it, and also due to migration from copper and polymetallic ores.
Man is also to blame for the contamination with this metal. Wastewater from various enterprises engaged in ore dressing, galvanic, chemical, metallurgical production may contain large amounts of cadmium compounds.
Natural processes to reduce the level of cadmium compounds are sorption, its consumption by microorganisms and precipitation of poorly soluble cadmium carbonate.
In solution, cadmium is, as a rule, in the form of organo-mineral and mineral complexes. Cadmium-based sorbed substances are the most important suspended forms of this element. Migration of cadmium in living organisms (hydrobionites) is very important.
Cadmium content in natural water bodies
Cadmium level in clean rivers and lakes fluctuates at a level of less than a microgram per liter, in polluted waters the level of this element reaches several micrograms per liter.
Some researchers believe that cadmium, in small amounts, may be important for the normal development of animals and humans. Elevated concentrations cadmium is very dangerous for living organisms.
Maximum allowable concentration of cadmium for the aquatic environment
MPC for the aquatic environment does not exceed 1 µg/l, and in fishery ponds the MPC for fish farms is less than 0.5 µg/l.
Cobalt (Co)
Rivers and lakes can become contaminated with cobalt as a result of leaching of copper and other ores, from soils during the decomposition of extinct organisms (animals and plants), and of course, as a result of the activity of chemical, metallurgical and metalworking enterprises.
The main forms of cobalt compounds are in dissolved and suspended states. Variations between these two states can occur due to changes in pH, temperature, and solution composition. In the dissolved state, cobalt is found in the form of organic complexes. Rivers and lakes have the characteristic that cobalt is represented by a divalent cation. In the presence of a large number of oxidizing agents in solution, cobalt can be oxidized to a trivalent cation.
It is found in plants and animals because it plays an important role in their development. It is one of the main trace elements. If there is a deficiency of cobalt in the soil, then its level in plants will be less than usual and as a result, health problems may appear in animals (there is a risk of anemia). This fact is observed especially in the taiga-forest non-chernozem zone. It is part of vitamin B 12, regulates the absorption of nitrogenous substances, increases the level of chlorophyll and ascorbic acid. Without it, plants cannot build up the required amount of protein. Like all heavy metals, it can be toxic in large quantities.
The content of cobalt in natural waters
- Cobalt levels in rivers range from a few micrograms to milligrams per litre.
- In the seas, the average level of cadmium is 0.5 µg/l.
Maximum permissible concentration of cobalt for the aquatic environment
MPC for cobalt for the aquatic environment is 0.1 mg/l, and in fishery ponds the MPC for fish farms is 0.01 mg/l.
Manganese (Mn)
Manganese enters rivers and lakes through the same mechanisms as iron. Mainly, the release of this element in solution occurs during the leaching of minerals and ores that contain manganese (black ocher, brownite, pyrolusite, psilomelane). Manganese can also come from the decomposition of various organisms. Industry has, I think, the most big role in manganese pollution (sewage from mines, chemical industry, metallurgy).
The decrease in the amount of assimilable metal in solution occurs, as in the case of other metals under aerobic conditions. Mn(II) is oxidized to Mn(IV), as a result of which it precipitates in the form of MnO 2 . Important factors in such processes are temperature, the amount of dissolved oxygen in the solution and pH. A decrease in dissolved manganese in solution can occur when it is consumed by algae.
Manganese migrates mainly in the form of suspensions, which, as a rule, indicate the composition of the surrounding rocks. They contain it as a mixture with other metals in the form of hydroxides. The predominance of manganese in colloidal and dissolved form indicates that it is associated with organic compounds forming complexes. Stable complexes are seen with sulfates and bicarbonates. With chlorine, manganese forms complexes less frequently. Unlike other metals, it is weaker retained in complexes. Trivalent manganese forms such compounds only in the presence of aggressive ligands. Other ionic forms (Mn 4+ , Mn 7+) are less rare or not found at all under normal conditions in rivers and lakes.
Manganese content in natural water bodies
The seas are considered the poorest in manganese - 2 μg / l, in rivers its content is higher - up to 160 μg / l, but underground reservoirs are champions this time - from 100 μg to several mg / l.
Manganese is characterized by seasonal fluctuations in concentration, like iron.
Many factors have been identified that affect the level of free manganese in solution: the connection of rivers and lakes with underground reservoirs, the presence of photosynthetic organisms, aerobic conditions, biomass decomposition (dead organisms and plants).
An important biochemical role of this element, because it is included in the group of microelements. Many processes are inhibited in manganese deficiency. It increases the intensity of photosynthesis, participates in nitrogen metabolism, protects cells from the negative effects of Fe (II) while oxidizing it into a trivalent form.
Maximum permissible concentration of manganese for the aquatic environment
MPC for manganese for reservoirs is 0.1 mg/l.
Copper (Cu)
Not a single microelement has such an important role for living organisms! Copper is one of the most sought after trace elements. It is part of many enzymes. Without it, almost nothing works in a living organism: the synthesis of proteins, vitamins and fats is disrupted. Without it, plants cannot reproduce. Still, an excess amount of copper causes great intoxication in all types of living organisms.
Copper levels in natural waters
Although copper has two ionic forms, Cu(II) occurs most frequently in solution. Usually, Cu(I) compounds are hardly soluble in solution (Cu 2 S, CuCl, Cu 2 O). Different aquaionic coppers can arise in the presence of any ligands.
With today's high use of copper in industry and Agriculture, this metal can cause environmental pollution. Chemical, metallurgical plants, mines can be sources of wastewater with a high content of copper. Pipeline erosion processes also contribute to copper contamination. by the most important minerals malachite, bornite, chalcopyrite, chalcosine, azurite, brontantine are considered to be high in copper.
Maximum allowable concentration of copper for the aquatic environment
The MPC of copper for the aquatic environment is considered to be 0.1 mg/l; in fish ponds, the MPC of the fish farm of copper is reduced to 0.001 mg/l.
Molybdenum (Mo)
During the leaching of minerals with a high molybdenum content, various molybdenum compounds are released. High level molybdenum can be seen in rivers and lakes that are close to beneficiation factories and non-ferrous metallurgy enterprises. Due to different processes of precipitation of sparingly soluble compounds, adsorption on the surface of different rocks, as well as consumption by aquatic algae and plants, its amount may noticeably decrease.
Mostly in solution, molybdenum can be in the form of the MoO 4 2- anion. There is a possibility of the presence of molybdenum-organic complexes. Due to the fact that loose finely dispersed compounds are formed during the oxidation of molybdenite, the level of colloidal molybdenum increases.
The content of molybdenum in natural reservoirs
Molybdenum levels in rivers range between 2.1 and 10.6 µg/l. In the seas and oceans, its content is 10 µg/l.
At low concentrations, molybdenum helps the normal development of the organism (both vegetable and animal), because it is included in the category of microelements. Also he is integral part various enzymes such as xanthine oxylase. With a lack of molybdenum, a deficiency of this enzyme occurs and thus negative effects can occur. An excess of this element is also not welcome, because normal metabolism is disturbed.
Maximum permissible concentration of molybdenum for the aquatic environment
MPC of molybdenum in surface water oyomah should not exceed 0.25 mg/l.
Arsenic (As)
Contaminated with arsenic are mainly areas that are close to mineral mines with a high content of this element (tungsten, copper-cobalt, polymetallic ores). A very small amount of arsenic can occur during the decomposition of living organisms. Thanks to aquatic organisms, it can be assimilated by these. Intensive assimilation of arsenic from solution is observed during the period of rapid development of plankton.
The most important arsenic pollutants are considered to be the enrichment industry, pesticide and dye factories, and agriculture.
Lakes and rivers contain arsenic in two states: suspended and dissolved. The proportions between these forms may vary depending on the pH of the solution and the chemical composition of the solution. In the dissolved state, arsenic can be trivalent or pentavalent, entering into anionic forms.
Arsenic levels in natural waters
In rivers, as a rule, the content of arsenic is very low (at the level of µg/l), and in the seas - an average of 3 µg/l. Some mineral water may contain large amounts of arsenic (up to several milligrams per litre).
Most of the arsenic can contain underground reservoirs - up to several tens of milligrams per liter.
Its compounds are highly toxic to all animals and to humans. In large quantities, the processes of oxidation and oxygen transport to the cells are disrupted.
Maximum allowable concentration of arsenic for the aquatic environment
MPC for arsenic for the aquatic environment is 50 μg/l, and in fishery ponds, the MPC for fish farms is also 50 μg/l.
Nickel (Ni)
Nickel content in lakes and rivers is influenced by local rocks. If there are deposits of nickel and iron-nickel ores near the reservoir, the concentration can be even higher than normal. Nickel can enter lakes and rivers when plants and animals decompose. Blue-green algae contain record amounts of nickel compared to other plant organisms. Important waste waters with a high nickel content are released during the production of synthetic rubber, during nickel plating processes. Nickel is also released in large quantities during the combustion of coal and oil.
High pH can cause nickel to precipitate in the form of sulfates, cyanides, carbonates or hydroxides. Living organisms can reduce the level of mobile nickel by consuming it. The processes of adsorption on the rock surface are also important.
Water can contain nickel in dissolved, colloidal and suspended forms (the balance between these states depends on the pH of the medium, temperature and water composition). Iron hydroxide, calcium carbonate, clay adsorb nickel-containing compounds well. Dissolved nickel is in the form of complexes with fulvic and humic acids, as well as with amino acids and cyanides. Ni 2+ is considered the most stable ionic form. Ni 3+ is usually formed at high pH.
In the mid-1950s, nickel was added to the list of trace elements because it plays an important role in various processes as a catalyst. In low doses, it has a positive effect on hematopoietic processes. Large doses are still very dangerous for health, because nickel is a carcinogenic chemical element and can provoke various diseases of the respiratory system. Free Ni 2+ is more toxic than in the form of complexes (approximately 2 times).
Nickel level in natural waters
Maximum allowable concentration of nickel for the aquatic environment
MPC for nickel for the aquatic environment is 0.1 mg/l, but in fishery ponds the MPC for fish farms is 0.01 mg/l.
Tin (Sn)
natural springs tin are minerals that contain this element (stannin, cassiterite). Anthropogenic sources are plants and factories for the production of various organic paints and the metallurgical industry working with the addition of tin.
Tin is a low-toxic metal, which is why eating from metal cans we do not risk our health.
Lakes and rivers contain less than a microgram of tin per liter of water. Underground reservoirs may contain several micrograms of tin per liter.
Maximum permissible concentration of tin for the aquatic environment
Maximum allowable concentration of tin for the aquatic environment is 2 mg/l.
Mercury (Hg)
Mainly, elevated level mercury in water is seen in areas where there are deposits of mercury. The most common minerals are livingstone, cinnabar, metacinnabarite. Wastewater from pharmaceutical, pesticide, and dye factories can contain important amounts of mercury. Another important source of mercury pollution is thermal power plants(which use coal as fuel).
Its level in solution decreases mainly due to marine animals and plants, which accumulate and even concentrate mercury! Sometimes the mercury content in marine life rises several times more than in the marine environment.
Natural water contains mercury in two forms: suspended (in the form of sorbed compounds) and dissolved (complex, mineral compounds of mercury). In certain areas of the oceans, mercury can appear as methylmercury complexes.
Mercury and its compounds are highly toxic. At high concentrations, it has a negative effect on nervous system, provokes changes in the blood, affects the secretion of the digestive tract and motor function. The products of mercury processing by bacteria are very dangerous. They can synthesize organic substances based on mercury, which are many times more toxic than inorganic compounds. When eating fish, mercury compounds can enter our body.
Maximum permissible concentration of mercury for the aquatic environment
The MPC of mercury in ordinary water is 0.5 µg/l, and in fishery ponds the MAC of fish farms is less than 0.1 µg/l.
Lead (Pb)
Rivers and lakes can be polluted with lead in a natural way when lead minerals are washed off (galena, anglesite, cerussite), and in an anthropogenic way (burning coal, using tetraethyl lead in fuel, discharges from ore-dressing factories, wastewater from mines and metallurgical plants). The precipitation of lead compounds and the adsorption of these substances on the surface of various rocks are the most important natural methods for lowering its level in solution. From biological factors, hydrobionts lead to a decrease in the level of lead in solution.
Lead in rivers and lakes is in suspended and dissolved form (mineral and organo-mineral complexes). Also, lead is in the form of insoluble substances: sulfates, carbonates, sulfides.
Lead content in natural waters
We have heard a lot about the toxicity of this heavy metal. It is very dangerous even in small quantities and can cause intoxication. Lead enters the body through the respiratory and digestive systems. Its excretion from the body is very slow, and it can accumulate in the kidneys, bones and liver.
Maximum allowable concentration of lead for the aquatic environment
MPC for lead for the aquatic environment is 0.03 mg/l, and in fishery ponds the MPC for fish farms is 0.1 mg/l.
Tetraethyl lead
It serves as an antiknock agent in motor fuels. Thus, vehicles are the main sources of pollution with this substance.
This compound is highly toxic and can accumulate in the body.
Maximum allowable concentration of tetraethyl lead for the aquatic environment
The maximum permissible level of this substance is approaching zero.
Tetraethyl lead is generally not allowed in the composition of waters.
Silver (AG)
Silver mainly enters rivers and lakes from underground reservoirs and as a consequence of the discharge of wastewater from enterprises (photographic enterprises, enrichment factories) and mines. Another source of silver can be algicidal and bactericidal agents.
In solution, the most important compounds are the silver halide salts.
Silver content in natural waters
In clean rivers and lakes, the silver content is less than a microgram per liter, in the seas - 0.3 µg / l. Underground reservoirs contain up to several tens of micrograms per liter.
Silver in ionic form (at certain concentrations) has a bacteriostatic and bactericidal effect. In order to be able to sterilize water with silver, its concentration must be greater than 2 * 10 -11 mol / l. Biological role silver in the body is still not well known.
Maximum allowable concentration of silver for the aquatic environment
The maximum permissible silver for the aquatic environment is 0.05 mg / l.
AT Russian Federation the quality of drinking water must meet certain requirements established by SanPiN 2.1.4.10749-01 "Drinking water". In the European Union (EU), the directive "On the quality of drinking water intended for human consumption" 98/83/EC defines the standards. World Organization(WHO) establishes water quality requirements in the 1992 Guidelines for the Control of Drinking Water Quality. There are also U.S. Environmental Protection Agency (U.S.EPA) regulations. In the norms, there are slight differences in various indicators, but only water of the appropriate chemical composition ensures human health. The presence of inorganic, organic, biological contaminants, as well as an increased content of non-toxic salts in amounts exceeding those specified in the requirements presented, leads to the development various diseases.
The main requirements for drinking water are that it must have favorable organoleptic characteristics, be harmless in its chemical composition and safe in epidemiological and radiation terms. Before water is supplied to distribution networks, at water intake points, external and internal water supply networks, the quality of drinking water must comply with hygienic standards.
Table 1. Requirements for the quality of drinking water
| Indicators | Units | Maximum Permissible Concentrations (MAC), not more than | Harm factor | Hazard Class | WHO | U.S.EPA | EU |
| Hydrogen indicator | pH | 6-9 | - | - | 6,5-8,5 | 6,5-8,5 | |
| Total mineralization (dry residue) | mg/l | 1000 (1500) | - | - | 1000 | 500 | 1500 |
| General hardness | mg-eq./l | 7,0 (10) | - | - | - | - | 1,2 |
| Oxidability permanganate | mg/l | 5,0 | - | - | - | - | 5,0 |
| Oil products, total | mg/l | 0,1 | - | - | - | - | - |
| Surfactants (surfactants), anionic | mg/l | 0,5 | - | - | - | - | - |
| Phenolic index | mg/l | 0,25 | - | - | - | - | - |
| Alkalinity | mgHCO3-/l | - | - | - | - | - | 30 |
| Phenolic index | mg/l | 0,25 | - | - | - | - | - |
| inorganic substances | |||||||
| Aluminum (Al 3+) | mg/l | 0,5 | With. -t. | 2 | 0,2 | 0,2 | 0,2 |
| Ammonia nitrogen | mg/l | 2,0 | With. -t. | 3 | 1,5 | - | 0,5 |
| Asbestos | Mill.fiber/l | - | - | - | - | 7,0 | - |
| Barium (Ba2+) | mg/l | 0,1 | -"- | 2 | 0,7 | 2,0 | 0,1 |
| Beryllium (Be2+) | mg/l | 0,0002 | - | 1 | - | 0,004 | - |
| Boron (V, total) | mg/l | 0,5 | - | 2 | 0,3 | - | 1,0 |
| Vanadium (V) | mg/l | 0,1 | With. -t. | 3 | 0,1 | - | - |
| Bismuth (Bi) | mg/l | 0,1 | With. -t. | 2 | 0,1 | - | - |
| Iron (Fe, total) | mg/l | 0,3 (1,0) | org. | 3 | 0,3 | 0,3 | 0,2 |
| Cadmium (Cd, total) | mg/l | 0,001 | With. -t. | 2 | 0,003 | 0,005 | 0,005 |
| Potassium (K+) | mg/l | - | - | - | - | - | 12,0 |
| Calcium (Ca+2) | mg/l | - | - | - | - | - | 100,0 |
| Cobalt (Co) | mg/l | 0,1 | With. -t. | 2 | - | - | - |
| Silicon (Si) | mg/l | 10,0 | With. -t. | 2 | - | - | - |
| Magnesium (Mg+2) | mg/l | - | With. -t. | - | - | - | 50,0 |
| Manganese (Mn, total) | mg/l | 0,1 (0,5) | org. | 3 | 0,5 (0,1) | 0,05 | 0,05 |
| Copper (Cu, total) | mg/l | 1,0 | -"- | 3 | 2,0 (1,0) | 1,0-1,3 | 2,0 |
| Molybdenum (Mo, total) | mg/l | 0,25 | With. -t. | 2 | 0,07 | - | - |
| Arsenic (As, total) | mg/l | 0,05 | With. -t. | 2 | 0,01 | 0,05 | 0,01 |
| Nickel (Ni, total) | mg/l | 0,1 | With. -t. | 3 | - | - | - |
| Nitrates (according to NO 3 -) | mg/l | 45 | With. -t. | 3 | 50,0 | 44,0 | 50,0 |
| Nitrites (according to NO 2 -) | mg/l | 3,0 | - | 2 | 3,0 | 3,5 | 0,5 |
| Mercury (Hg, total) | mg/l | 0,0005 | With. -t. | 1 | 0,001 | 0,002 | 0,001 |
| Lead (Pb, total) | mg/l | 0,03 | -"- | 2 | 0,01 | 0,015 | 0,01 |
| Selenium (Se, total) | mg/l | 0,01 | - | 2 | 0,01 | 0,05 | 0,01 |
| Silver (Ag+) | mg/l | 0,05 | - | 2 | - | 0,1 | 0,01 |
| Hydrogen sulfide (H 2 S) | mg/l | 0,03 | org. | 4 | 0,05 | - | - |
| Strontium (Sg 2+) | mg/l | 7,0 | -"- | 2 | - | - | - |
| Sulphates (S0 4 2-) | mg/l | 500 | org. | 4 | 250,0 | 250,0 | 250,0 |
| Fluorides F - (for climatic regions) | |||||||
| I and II | mg/l | 1,5 | With. -t. | 2 | 1,5 | 2,0-4,0 | 1,5 |
| III | mg/l | 1,2 | -"- | 2 | |||
| Chlorides (Сl -) | mg/l | 350 | org. | 4 | 250,0 | 250,0 | 250,0 |
| Chromium (Cr 3+) | mg/l | 0,5 | With. -t. | 3 | - | 0.1 (total) | - |
| Chromium (Cr 6+) | mg/l | 0,05 | With. -t. | 3 | 0,05 | 0,05 | |
| Cyanides (CN -) | mg/l | 0,035 | -"- | 2 | 0,07 | 0,2 | 0,05 |
| Zinc (Zn2+) | mg/l | 5,0 | org. | 3 | 3,0 | 5,0 | 5,0 |
s.-t. – sanitary-toxicological; org. – organoleptic.
Vladimir Khomutko
Reading time: 5 minutes
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The problem of the presence of oil products in water and how to deal with it
Among the most common and toxically hazardous substances that serve as sources of pollution of the natural aquatic environment, experts include petroleum products (NP).
Oil and its derivatives are unstable mixtures of hydrocarbons of the saturated and unsaturated groups, as well as their derivatives different kind. Hydrochemistry conditionally interprets the concept of "petroleum products", limited only to their hydrocarbon aliphatic, aromatic and acyclic fractions, which constitute the main and most common part of the oil and its components released during the oil refining process. To denote the content of oil products in water, in international practice there is the term Hydrocarbon Oil Index (“hydrocarbon oil index”).
The maximum permissible concentration (MPC) in water of oil and oil products for cultural and domestic and household water use facilities is at around 0.3 milligrams per cubic decimeter, and for fishery water use facilities - 0.05 milligrams per cubic decimeter.
The determination of oil products contained in water is possible using various instruments and methods, which we will briefly discuss in this article.
To date, there are four main methods for determining the concentration of oil and its derivatives in water, which are based on different physical properties determined oil products:
- gravimetry method;
- IR spectrophotometry;
- fluorimetric method;
- gas chromatography technique.
The methodology for applying one or another method of measuring the content of oils and oil products in water, as well as MPC standards for various kinds petroleum products, is regulated by environmental normative documents federal significance (abbreviated as PND F).
gravimetric method
Its use is regulated by PND F number 14.1:2.116-97.
Its essence is the extraction (dehydration) of oil products from the samples provided for analysis using an organic solvent, followed by separation from polar compounds using column chromatography on aluminum oxide of other classes of compounds, after which the content of the substance in water is quantified.
In wastewater studies, this method is used at concentrations ranging from 0.30 to 50.0 milligrams per cubic decimeter, which does not allow determining the compliance of water with MPC standards at fisheries water use facilities.
Another significant disadvantage of this method is the long period of time required for measurements. Therefore, it is not used in the current technological control in production, as well as in other cases where the speed of obtaining results is of paramount importance.
Experts attribute the absence of standard calibrations for samples, which are typical for other methods of analysis, to the advantages of this technique.
The error when using this method with a P value of 0.95 (±δ, %) in the analysis of natural waters varies from 25 to 28 percent, and in the analysis of waste water - from 10 to 35.
IR spectrophotometry
The use of this technique is regulated by PND F number 14.1: 2: 4.168, as well as guidelines MUK 4.1.1013-01.
The essence of this technique for determining the content of oil products in water is the isolation of dissolved and emulsified oil contaminants by extracting them with carbon tetrachloride, followed by chromatographic separation of the oil product from other compounds of the organic group, on a column filled with aluminum oxide. After that, the determination of the amount of NPs in water is carried out according to the intensity of absorption in the infrared region. C-H spectrum connections.
Infrared spectroscopy is currently one of the most powerful analytical techniques, and is widely used in both applied and fundamental research. Its application is also possible for the needs of the current control of the production process.
The most popular technique for such spectral IR analysis today is Fourier IR. Spectrometers based on this technique, even those in the lower and middle price niche, are already competing in their parameters with such traditional instruments as diffraction spectrometers. They are now widely used in numerous analytical laboratories.
In addition to optics, the standard package of such devices necessarily includes a control computer, which not only performs the function of controlling the process of obtaining the required spectrum, but also serves for operational processing of the received data. Using such IR spectrometers, it is quite easy to obtain the vibrational spectrum of the compound presented for analysis.
The main advantages of this technique are:
- small quantities of initial samples of analyzed water (from 200 tons to 250 milliliters);
- high sensitivity of the method (determination step - 0.02 milligrams per cubic decimeter, which allows you to determine the compliance of the results with the MPC standards for fishery reservoirs).
The most important disadvantage of this method of analysis (especially when using a photocolorimetric end), experts call a high degree of its dependence on the type of oil product being analyzed. Determination with a photocolorimeter requires the construction of separate calibration curves for each type of oil product. This is due to the fact that the discrepancy between the standard and the analyzed oil product significantly distorts the results.
This method is used at NP concentrations from 0.02 to 10 milligrams per cubic decimeter. The measurement error at P equal to 0.95 (±δ,%) ranges from 25 to 50 percent.
Regulated by PND F number 14.1:2:4.128-98.
The essence of this technique is the dehydration of petroleum products, followed by their extraction from water with hexane, then purification of the resulting extract (if necessary) and subsequent measurement of the fluorescent intensity of the extract, which arises from optical excitation. To measure the intensity of fluorescence, a Fluorat-2 liquid analyzer is used.
The undoubted advantages of this method include:
Aromatic hydrocarbons for excitation and subsequent registration of fluorescent radiation require various conditions. Experts note the dependence of spectral changes in fluorescence on the wavelength possessed by the exciting light. If excitation occurs in the near part of the ultraviolet spectrum, and even more so in its visible region, then fluorescence appears only in polynuclear hydrocarbons.
Since their share is quite small and directly depends on the nature of the studied oil product, there is a high degree of dependence of the obtained analytical signal on a specific type of oil product. When exposed to ultraviolet radiation, only some hydrocarbons luminesce, mainly high molecular weight aromatic hydrocarbons from the group of polycyclic hydrocarbons. Moreover, the intensity of their radiation varies greatly.
In this regard, in order to obtain reliable results, it is necessary to have a standard solution that contains the same luminescent components (and in the same relative proportions) that are present in the analyzed sample. This is most often difficult to achieve, therefore, the fluorimetric method for determining the content of oil products in water, which is based on recording the intensity of fluorescent radiation in the visible part of the spectrum, is unsuitable for mass analyzes.
This method can be applied at oil concentrations ranging from 0.005 to 50.0 milligrams per cubic decimeter.
The error of the results obtained (at P equal to 0.95, (±δ, %)) ranges from 25 to 50 percent.
The use of this technique is regulated by GOST No. 31953-2012.
This technique is used to determine the mass concentration of various petroleum products both in drinking (including packaged in containers) and in natural (both surface and underground) water, as well as in water contained in household and drinking sources. This method is also effective in the analysis of waste water. The main thing is that the mass concentration of oil products should not be less than 0.02 milligrams per cubic decimeter.
The essence of the gas chromatography method is the extraction of NP from the analyzed water sample using an extractant, its subsequent purification from polar compounds using a sorbent, and the final analysis of the resulting substance on a gas chromatograph.
The result is obtained after summing up the areas of the chromatographic peaks of the released hydrocarbons and by subsequent calculation of the OP content in the analyzed water sample using a predetermined calibration dependence.
With the help of gas chromatography, not only the total concentration of oil products in water is determined, but also their specific composition is identified.
Gas chromatography is generally a technique based on the separation of thermostable volatile compounds. Approximately five percent of the total number of organic compounds known to science meet these requirements. However, they occupy 70-80 percent of the total number of compounds used by man in production and everyday life.
The role of the mobile phase in this technique is played by a carrier gas (usually an inert group), which flows through the stationary phase with much larger area surfaces. As the carrier gas of the mobile phase is used:
- hydrogen;
- nitrogen;
- carbon dioxide;
- helium;
- argon.
Most often, the most accessible and inexpensive nitrogen is used.
It is with the help of the carrier gas that the components to be separated are transported through the chromatographic column. In this case, this gas does not interact either with the separated components themselves, or with or with the substance of the stationary phase.
The main advantages of gas chromatography:
- the relative simplicity of the equipment used;
- a fairly wide field of application;
- the possibility of high-precision determination of sufficiently small concentrations of gases in organic compounds;
- the speed of obtaining the results of the analysis;
- a wide range of both used sorbents and substances for stationary phases;
- a high level of flexibility that allows you to change the separation conditions;
- possibility of chemical reactions in a chromatographic detector or in a chromatographic column, which significantly increases the coverage of chemical compounds subjected to analysis;
- increased information content when used with other instrumental methods of analysis (for example, with mass spectrometry and Fourier-IR spectrometry).
The error of the results of this technique (P equals 0.95 (±δ,%)) ranges from 25 to 50 percent.
It should be noted that only the method of measuring the content of oil products in water using gas chromatography is standardized in international organization according to standardization, which we all know under the abbreviation ISO, since only it makes it possible to identify the types of oil and oil product pollution.
Regardless of the methodology used, constant monitoring of the waters used in production and in the domestic sphere is vital. According to environmentalists, in some Russian regions More than half of all diseases are related in one way or another to the quality of drinking water.
High concentration of oil products in water
Moreover, according to the same scientists, improving the quality of drinking water alone can extend life by five to seven years. All these factors indicate the importance of constant monitoring of the state of water near oil industry enterprises, which are the main sources of environmental pollution by oil and its derivatives.
Timely detection of exceeding the MPC of oil products in water will allow avoiding large-scale disturbances of the ecosystem, and timely taking the necessary measures to eliminate the current situation.
However, environmental scientists need government support to work effectively. And not so much in the form of cash subsidies, but in the creation of a regulatory framework that regulates the responsibility of national economy enterprises for violation of environmental standards, as well as in strict control over the implementation of adopted standards.
PEEP - the maximum permissible concentration of a substance in the water of a reservoir for drinking and domestic water use, mg / l. This concentration should not have a direct or indirect effect on the human body throughout life, as well as on the health of subsequent generations, and should not worsen the hygienic conditions for water use. PEEP.r. - The maximum permissible concentration of a substance in the water of a reservoir used for fishery purposes, mg/l.
The assessment of the quality of aquatic ecosystems is based on normative and directive documents using direct hydrogeochemical assessments. In table. 2.4, as an example, the criteria for assessing the chemical pollution of surface waters are given.
For water, maximum permissible concentrations of more than 960 chemical compounds have been established, which are combined into three groups according to the following limiting hazard indicators (LPV): sanitary-toxicological (s.-t.); general sanitary (gen.); organoleptic (org.).
MPC of some harmful substances in the aquatic environment are presented in Table. 2.1.4.
The highest requirements are placed on drinking water. State standard on water used for drinking and Food Industry(SanPiN 2.1.4.1074-01), determines the organoleptic indicators of water that are favorable for humans: taste, smell, color, transparency, as well as the harmlessness of its chemical composition and epidemiological safety.
Table 2.1.4
MPC of harmful substances in water bodies of domestic and drinking
cultural and household water use, mg/l
(GN 2.1.5.689-98)
| Substances | LPV | MPC |
| 1 | 2 | 3 |
| />Bor | S.-t. | 0,5 |
| Bromine | S.-t. | 0,2 |
| Bismuth | S.-t. | 0,1 |
| Hexachlorobenzene | S.-t. | 0,05 |
| Dimethylamine | S.-t. | 0,1 |
| Difluorodichloromethane (freon) | S.-t. | 10 |
| diethyl ether | Org. | 0,3 |
| Iron | Org. | 0,3 |
| Isoprene | Org. | 0,005 |
| Cadmium | S.-t. | 0,001 |
| Karbofos | Org. | 0,05 |
| Kerosene: | | |
| oxidized | Org. | 0,01 |
| Lighting (GOST 4753-68) | Org. | 0,05 |
| Technical | Org. | 0,001 |
| Acid: | | |
| benzoic | Tot. | 0,6 |
| Diphenylacetic | Tot. | 0,5 |
| oily | Tot. | 0,7 |
| Ant | Tot. | 3,5 |
| Acetic | Tot. | 1,2 |
| Synthetic fatty acids | Tot. | 0,1 |
| C5-C20 | | |
| Manganese | Org. | 0,1 |
| Copper | Org. | 1 |
| methanol | St. | 3 |
| Molybdenum | St. | 0,25 |
| Urea | Tot. | 1 |
| Naphthalene | Org. | 0,01 |
| Oil: | | |
| polysulphurous | Org. | 0,1 |
| durable | Org. | 0,3 |
| Nitrates for: | | |
| NO3- | St. | 45 |
| NO2- | St. | 3,3 |
| Polyethyleneamine | St. | 0,1 |
| Thiocyanates | St. | 0,1 |
| Mercury | St. | 0,0005 |
| Lead | St. | 0,03 |
| carbon disulfide | Org. | 1 |
| Turpentine | Org. | 0,2 |
| Sulfides | Tot. | Absence |
| Tetraethyl lead | St. | Absence |
| Tributyl Phosphate | Tot. | 0,01 |
Drinking water at any time of the year should not contain less than 4 g / m of oxygen, and the presence of mineral impurities (mg / l) in it should not exceed: sulfates (SO4 -) - 500; chlorides (Cl -) - 350; iron (Fe2+ + Fe3+) - 0.3; manganese (Mn2+) - 0.1; copper (Cu2+) - 1.0; zinc (Zn2+) - 5.0; aluminum (Al) - 0.5; metaphosphates (PO3 ") - 3.5; phosphates (PO4
3") - 3.5; dry residue - 1000. Thus, water is suitable for drinking if its total mineral content does not exceed 1000 mg / l. Very low mineral content of water (below 1000 mg / l) also worsens its taste, and water , generally devoid of salts (distilled), is harmful to health, since its use disrupts digestion and the activity of endocrine glands.Sometimes, in agreement with the sanitary and epidemiological service, a dry residue content of up to 1500 mg / l is allowed.
Indicators characterizing the pollution of reservoirs and drinking water with substances classified as hazard classes 3 and 4, as well as physiochemical properties and organoleptic characteristics of water are additional. They are used to confirm the degree of intensity of anthropogenic pollution of water sources, established by priority indicators.
The application of different criteria for assessing water quality should be based on the advantage of the requirements of the water use whose criteria are more stringent. For example, if a water body simultaneously serves drinking and fisheries purposes, then more stringent requirements (environmental and fisheries) may be imposed on the assessment of water quality.
PCP-10 (indicator of chemical pollution). This indicator is especially important for areas where chemical pollution is observed for several substances at once, each of which many times exceeds the MPC. It is calculated only when identifying areas of environmental emergency and areas of environmental disaster.
The calculation is carried out for ten compounds that maximally exceed the MPC, according to the formula:
PKhZ-10 = C1 / MPC1 + C2 / MPC2 + C3 / MPC3 + ... C10 / MPC10,
where Cb C2, C3 ... Cb - concentration of chemicals in water: MPC - fisheries.
When determining PCP-10 for chemicals for which there is no relatively satisfactory value of water pollution, the C/MAC ratio is conditionally taken equal to 1.
To establish PCP-10, it is recommended to analyze water according to the maximum possible number of indicators.
Additional indicators include generally accepted physicochemical and biological characteristics giving general idea on the composition and quality of water. These indicators are used to additionally characterize the processes occurring in water bodies. In addition, additional characteristics include indicators that take into account the ability of pollutants to accumulate in bottom sediments and hydrobionts.
The coefficient of bottom accumulation of CDA is calculated by the formula:
KDA \u003d Sd.o. / Sv,
where Sd. about. and Sv - the concentration of pollutants in bottom sediments and water, respectively.
Accumulation coefficient in hydrobionts:
Kn \u003d Sg / Sv,
where Cr is the concentration of pollutants in hydrobionts.
Critical concentrations of chemicals (CC) are determined according to the methodology for determining the critical concentrations of pollutants developed by the State Committee for Hydrometeorology in 1983.
The average CC values of some pollutants are, mg/l: copper - 0.001 ... 0.003; cadmium - 0.008 ... 0.020; zinc - 0.05...0.10; PCB - 0.005; benzo(a)pyrene - 0.005.
When assessing the state of aquatic ecosystems, sufficiently reliable indicators are the characteristics of the state and development of all ecological groups of the aquatic community.
When identifying the zones under consideration, indicators are used for bacterio-, phyto-, and zooplankton, as well as for ichthyofauna. In addition, to determine the degree of toxicity of waters, an integral indicator is used - biotesting (for lower crustaceans). In this case, the corresponding toxicity of the water mass should be observed in all main phases of the hydrological cycle.
The main indicators for phyto- and zooplankton, as well as for zoobenthos, were adopted on the basis of data from regional hydrobiological control services that characterize the degree of ecological degradation of freshwater ecosystems.
The parameters of the indicators proposed for the allocation of zones in a given territory should be formed on the basis of materials of sufficiently long observations (at least three years).
It should be borne in mind that the indicator values of species may be different in different climatic zones.
When assessing the state of aquatic ecosystems, indicators of ichthyofauna are important, especially for unique, specially protected water bodies and reservoirs of the first and highest fishery category.
BOD - biological need in oxygen - the amount of oxygen used in the biochemical processes of oxidation of organic substances (excluding nitrification processes) for a certain time of sample incubation (2, 5, 20, 120 days), mg O2 /l of water (BODp - for 20 days, BOD5 - for 5 days).
The oxidative process under these conditions is carried out by microorganisms that use organic components as food. The BOD method is as follows. The investigated waste water after two hours of settling is diluted clean water, taken in such an amount that the oxygen contained in it is sufficient for the complete oxidation of all organic substances in the wastewater. Having determined the content of dissolved oxygen in the resulting mixture, it is left in a closed bottle for 2, 3, 5, 10, 15 days, determining the oxygen content after each of the listed time periods (incubation period). The decrease in the amount of oxygen in water shows how much of it was spent during this time on the oxidation of organic substances in the wastewater. This amount, related to 1 liter of waste water, is an indicator of biochemical oxygen consumption. sewage for a given period of time (BOD2, BODz, BOD5, BODcu, BOD15).
It should be noted that biochemical oxygen consumption does not include its consumption for nitrification. Therefore, a complete BOD should be carried out before the start of nitrification, which usually begins after 15-20 days. The BOD of wastewater is calculated using the formula:
BOD = [(a1 ~ b1) ~ (a2 ~ b2)] X 1000
V'
where ai is the oxygen concentration in the sample prepared for determination at the beginning of incubation (on the “zero day”), mg/l; а2 - oxygen concentration in the diluting water at the beginning of incubation, mg/l; b1 - oxygen concentration in the sample at the end of incubation, mg/l; b2 is the oxygen concentration in the dilution water at the end of incubation, mg/l; V is the volume of waste water contained in 1 liter of the sample after all dilutions, ml.
COD is the chemical oxygen demand determined by the bichromate method, i.e. the amount of oxygen equivalent to the amount of consumed oxidant required for the oxidation of all reducing agents contained in water, mg O2/l of water.
Chemical oxygen consumption, expressed as the number of milligrams of oxygen per 1 liter of wastewater, is calculated by the formula:
HPC - 8(a - b)x N1000
V'
where a is the volume of Mohr's salt solution used for titration in a blank experiment, ml; b is the volume of the same solution used for sample titration, ml; N is the normality of the titrated solution of Mohr's salt; V is the volume of analyzed waste water, ml; 8 - oxygen equivalent.
In relation to BODp/COD, the efficiency of biochemical oxidation of substances is judged.
MAXIMUM PERMISSIBLE CONCENTRATION (MPC) OF HARMFUL SUBSTANCES- this is the maximum concentration of a harmful substance, which for a certain time of exposure does not affect human health and its offspring, as well as the components of the ecosystem and the natural community as a whole.
Many pollutants enter the atmosphere from various industrial productions and vehicles. To control their content in the air, well-defined standardized environmental standards are needed, and therefore the concept of the maximum permissible concentration was introduced. MPC values for air are measured in mg/m 3 . MPCs have been developed not only for air, but also for food products, water (drinking water, water of reservoirs, sewage), soil.
The maximum concentration for the working area is considered to be such a concentration of a harmful substance that, during daily work during the entire working period, cannot cause disease during work or in the long-term life of this and subsequent generations.
Limit concentrations for atmospheric air are measured in settlements and refer to a certain period of time. For air, a maximum single dose and an average daily dose are distinguished.
Depending on the MPC value chemical substances in the air are classified according to the degree of danger. For extremely hazardous substances(mercury vapor, hydrogen sulfide, chlorine) MPC in the air of the working area should not exceed 0.1 mg/m 3 . If the MPC is more than 10 mg/m 3, then the substance is considered to be of low hazard. Examples of such substances include ammonia.
| Table 1. MAXIMUM PERMISSIBLE CONCENTRATIONS some gaseous substances in atmospheric air and air industrial premises | ||
| Substance | MPC in atmospheric air, mg / m 3 | MPC in the air prod. rooms, mg / m 3 |
| nitrogen dioxide | Maximum single 0.085 Average daily 0.04 |
2,0 |
| sulphur dioxide | Maximum single 0.5 Average daily 0.05 |
10,0 |
| carbon monoxide | Maximum single 5.0 Average daily 3.0 |
During the working day 20.0 Within 60 min.* 50.0 Within 30 minutes* 100.0 Within 15 min.* 200.0 |
| Hydrogen fluoride | Maximum single 0.02 Average daily 0.005 |
0,05 |
| * Repeated works in conditions high content CO in the air of the working area can be carried out with a break of at least 2 hours | ||
MPCs are set for the average person, however, people weakened by disease and other factors may feel uncomfortable at concentrations of harmful substances that are lower than the MPC. This, for example, applies to heavy smokers.
The values of the maximum permissible concentrations of certain substances in a number of countries differ significantly. Thus, the MPC of hydrogen sulfide in the atmospheric air with a 24-hour exposure in Spain is 0.004 mg/m 3, and in Hungary - 0.15 mg/m 3 (in Russia - 0.008 mg/m 3).
In our country, the standards for the maximum permissible concentration are developed and approved by the bodies of the sanitary and epidemiological service and government bodies in the field of environmental protection. Environmental quality standards are the same for the entire territory of the Russian Federation. Taking into account the natural and climatic features, as well as the increased social value of individual territories, maximum permissible concentration standards can be established for them, reflecting special conditions.
With the simultaneous presence in the atmosphere of several harmful substances of unidirectional action, the sum of the ratios of their concentrations to the MPC should not exceed one, but this is far from always the case. According to some estimates, 67% of the Russian population lives in regions where the content of harmful substances in the air is above the established maximum permissible concentration. In 2000, the content of harmful substances in the atmosphere in 40 cities with a total population of about 23 million people from time to time exceeded the maximum permissible concentration by more than ten times.
When assessing the risk of pollution, studies carried out in biosphere reserves. But in large cities, the natural environment is far from ideal. So, according to the content of harmful substances, the Moscow River within the city is considered a “dirty river” and a “very dirty river”. At the exit of the Moskva River from Moscow, the content of oil products is 20 times higher than the maximum permissible concentrations, iron - 5 times, phosphates - 6 times, copper - 40 times, ammonium nitrogen - 10 times. The content of silver, zinc, bismuth, vanadium, nickel, boron, mercury and arsenic in the bottom sediments of the Moskva River exceeds the norm by 10–100 times. Heavy metals and other toxic substances from water enter the soil (for example, during floods), plants, fish, agricultural products, drinking water, both in Moscow and downstream in the Moscow region.
Chemical methods for assessing the quality of the environment are very important, but they do not provide direct information about the biological hazard of pollutants - this is the task of biological methods. Maximum allowable concentrations are certain standards for the sparing effect of pollutants on human health and the natural environment.
Elena Savinkina
