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Qualitative determination of lead in biological material. Water quality research

In forensic chemical and chemical toxicological analysis, when examining biological material (organs of corpses, biological fluids, plants, food products, etc.) for the presence of “metallic” poisons, the mineralization method is used. These poisons in the form of salts, oxides and other compounds in most cases enter the body orally, are absorbed into the blood and cause poisoning. “Metallic” poisons will be in the body in the form of compounds with proteins, peptides, amino acids and some other substances that play an important role in life processes. The bonds of metals with most of these substances are strong (covalent). Therefore, to study biological material for the presence of “metallic” poisons, it is necessary to destroy the organic substances with which metals are associated and convert them into an ionic state. The choice of method for mineralization of organic substances depends on the properties of the elements being studied and the amount of biological material received for analysis.

Mineralization is the oxidation (burning) of organic matter (object) to release metals from their complexes with proteins and other compounds. The most widely used mineralization methods can be divided into 2 large groups:

General methods (methods of “wet” mineralization) are used in a general study of the group of “metal poisons” and are suitable for isolating all metal cations. Except mercury. For mineralization, mixtures of oxidizing acids are used: sulfuric and nitric, sulfuric, nitric and perchloric.

Private methods ("dry ashing" methods) - the method of simple combustion, the method of fusion with a mixture of nitrates and carbonates of alkali metals. Among the private methods is the method of partial mineralization (destruction), which is used to isolate inorganic mercury compounds from biological materials.

1.1. Destruction of biological material by nitric and sulfuric acids

In a Kjeldahl flask with a capacity of 500-800 ml, add 100 g of crushed biological material, add 75 ml of a mixture consisting of equal volumes of concentrated nitric and sulfuric acids and purified water. The flask with the contents in a vertical position is fixed in a tripod so that its bottom is above the asbestos mesh at a distance of 1-2 cm. A separating funnel is fixed above the Kjeldahl flask in a tripod, which contains concentrated nitric acid, diluted with an equal volume of water. Next, they begin to carefully heat the flask. Within 30-40 minutes, destruction occurs, the destruction of the formed elements of biological material. Upon completion of destruction, a translucent liquid colored yellow or brown is obtained.

Then the Kjeldahl flask with its contents is lowered onto an asbestos mesh and the heating is increased - the stage of deep liquid-phase oxidation begins. To destroy the organic substances in the flask, concentrated nitric acid diluted with an equal volume of water is added drop by drop from a dropping funnel. Mineralization is considered complete when the transparent liquid (mineralizate), when heated without adding nitric acid for 30 minutes, stops darkening, and white vapors of sulfuric anhydride are released above the liquid.

The resulting mineralizate is subjected to denitration: cool, add 10-15 ml of purified water and heat to 110-130°C, and then carefully add a formaldehyde solution drop by drop, avoiding excess. At the same time, an abundant release of brown, sometimes orange, vapors is noted. After the release of these vapors, the liquid is still heated for 5-10 minutes, and then 1-2 drops of the cooled liquid (mineralizate) are applied to a glass slide or porcelain plate and a drop of diphenylamine solution in concentrated sulfuric acid is added. The effect of the reaction is a characteristic blue color.

The negative reaction of the mineralizate with diphenylamine to nitric, nitrous acids, and also to nitrogen oxides indicates the end of the denitration process. With a positive reaction of the mineralizate with diphenylamine, denitration is repeated.

The method of mineralization of biological material with concentrated nitric and sulfuric acids has a number of advantages. Mineralization by this method occurs faster and a relatively small volume of mineralizate is obtained than using other methods. However, mineralization with a mixture of sulfuric and nitric acid is unsuitable for isolating mercury from biological material, since a significant amount of it volatilizes when the biological material is heated at the stage of deep liquid-phase oxidation.

Municipal budgetary educational institution

"Ryzhkovskaya secondary school"

Kardymovsky district of the Smolensk region

Competition of students of educational organizations

and organizations of additional education of the Smolensk region

for the best environmental project “We live in the Smolensk region”

Ecological project

“Comprehensive analysis of the content of heavy metal compounds

in the environment and their impact on organisms"

Biryukova Alina Alexandrovna

Grade: 9

FULL NAME. work manager:

Baranova Olga Alekseevna

Titkovo village

2017

Table of contents

Introduction………………………………………………………………………………….………3

Chapter I . Heavy metals……………………………………………………………….…….. 5

Chapter II . Sources of heavy metal compounds entering the environment and living organisms…………….………………………………………………………………………………..…7

2.1. The entry of heavy metal compounds into the soil………………………..………..8

2.2. Intake of heavy metal compounds into water bodies………………………………9

2.3. Release of heavy metal compounds into the atmosphere…………………………….…9

2.4. Intake of heavy metal compounds into living organisms……………………10

Chapter III . Determination of the presence of heavy metal compounds in the environment and their impact on living organisms…………………………………………………….12

3.1. Compounds of heavy metals in soil …………………………………………13

3.1.1. Methodology for determining the presence of heavy metal compounds in soil......13

3.1.2. Results of analysis of the content of heavy metal compounds in soil……..…14

3.2. Compounds of heavy metals in natural waters………………………….………...14

3.2.1. Methodology for determining the presence of heavy metal compounds in natural waters…………………………………………………………………………………..14

3.2.2. Results of analysis of the content of heavy metal compounds in natural waters…………………………………………………………………………………………....14

3.3. Compounds of heavy metals in the atmosphere………………………………………………………15

3.3.1. Methodology for determining the presence of heavy metal compounds in the atmosphere ………………………………………………………………………………………..15

3.3.2. Results of analysis of the content of heavy metal compounds in the atmosphere…………………………………………………………………………………………...16

3.4. Compounds of heavy metals and living organisms……………………………………17

3.4.1. Methodology for determining the effects of heavy metal compounds on organisms…………………………………………………………………………………………...17

3.4.2. Results of determining the impact of heavy metal compounds on living organisms…………………………………………………………………………………18

Conclusion ………………………………………………………………………………………..20

References…………………………………………………………………………..…..21

Application ……………………………………………………………..……………………….22

Introduction

The environment is the habitat of living organisms that are in contact with it throughout their lives. Organisms receive from the environment everything they need for normal life: oxygen for breathing, water, nutrients, microelements and much more. Among the chemical elements entering organisms, heavy metals in the form of ions occupy a special place.

It has been established that heavy metal ions are normally present in the environment due to their intake from natural compounds, but their natural content is extremely low. Recently, the human impact on the environment has been increasing, and now the source of heavy metal compounds is also human activity (metallurgical production, motor vehicles, fertilizers), and the number of heavy metal ions of anthropogenic origin in the environment is increasing every year. Consequently, these ions will also enter organisms in greater quantities.

Does the “more is better” rule work here? Everyone knows that living organisms contain metals, including heavy ones: for example, iron in hemoglobin, zinc in insulin and many enzymes, copper is needed for the formation of nervous tissue and in the processes of hematopoiesis, and molybdenum activates the processes of binding atmospheric nitrogen by nodule bacteria. But these and many other chemical elements - heavy metals - are required by living organisms for normal functioning in rather small quantities, while some of the heavy metals, even in trace quantities, have a toxic effect, being the strongest toxic metals (mercury, lead, cadmium).

Is human activity really a powerful source of heavy metal compounds entering the environment, and do heavy metals themselves negatively affect living organisms? The work is devoted to the study of these issues.

At the beginning of the work it was put forwardhypothesis: heavy metal compounds are present in the environment of the study area (rural area), the content of heavy metal compounds is higher, the closer the sampling area is to the road; heavy metal compounds have a depressing effect on living organisms.

Target: studying the content of heavy metal compounds in the environment (air, soil, water) and their impact on living organisms.

To achieve this goal it is necessary to decidetasks :

Study the scientific literature on this issue.

Study methods for determining heavy metal compounds in the environment.

Conduct a qualitative analysis of soil, snow, water, biological material (lichens) samples for the content of heavy metal compounds.

Determine the effects of heavy metal compounds on living organisms.

Assess the degree of environmental pollution with heavy metal compounds in the study area.

Object of study : pollution of the environment and living organisms with heavy metal compounds.

Subject of study : soil, snow, water, living organisms (lichens, watercress).

Research methods:

Theoretical method

Morphometric method

Experimental method

Organoleptic method

Mathematical method

Location of the study: Titkovo village, Kardymovsky district.

Time frame for the study: February-March 2017.

Chapter I . Heavy metals

Heavy metals are a group of chemical elements with the properties of metals and a significant atomic weight, more than 40. About forty different definitions of the term heavy metals are known, and it is impossible to point to one of them as the most accepted. Accordingly, the list of heavy metals according to different definitions will include different elements.

The term “heavy metals” is most often considered not from a chemical, but from a medical and environmental point of view. Thus, when included in this category, not only the chemical and physical properties of an element are taken into account, but also its biological activity and toxicity, as well as the volume of use in economic activities.

In works devoted to the problems of environmental pollution and environmental monitoring, todayheavy metals include more than 40 metals of the periodic table D.I. Mendeleev with an atomic mass of over 50 atomic units:V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, Sn, Hg, Pb, Bi etc. At the same time, the following conditions play an important role in the categorization of heavy metals: their high toxicity to living organisms in relatively low concentrations, as well as the ability to bioaccumulate and biomagnify. Almost all metals that fall under this definition (with the exception of lead, mercury, cadmium and bismuth, the biological role of which is currently unclear) are actively involved in biological processes and are part of many enzymes. According to the classification of N. Reimers, metals with a density of more than 8 g/cm should be considered heavy 3 . Thus, heavy metals includePb, Cu, Zn, Ni, Cd, Co, Sb, Sn, Bi, Hg .

Manyheavy metals , such as , , , , participate in biological processes and in certain quantities are necessary for the functioning of plants, animals and humans . On the other side,heavy metals and their compounds may have harmful effects on living organisms. Moreover, the negative impact of heavy metals on living organisms and human health is manifested not only in the direct effects of high concentrations, but also in long-term consequences associated with their cumulative effect. Heavy metal compounds cause a number of diseases and general inhibition of vital processes. Metals that have no useful role in biological processes, such as And , are defined astoxic metals . In particularlead, which classified as highly hazardous substances along with arsenic, cadmium, mercury, selenium, zinc, fluorine and benzaprene (GOST 3778-98).Some elements such as or , which usually have toxic effects on living organisms, may be beneficial for some species.

Chapter II . Sources of heavy metal compounds

into the environment and living organisms

Among the biosphere pollutants that are of greatest interest to various quality control services, metals (primarily heavy, that is, having an atomic weight of more than 40) are among the most important. This is largely due to the biological activity of many of them.

Sources of heavy metals are divided into natural (weathering of rocks and minerals, erosion processes, volcanic activity) and man-made (mining and processing of minerals, fuel combustion, traffic, agricultural activities). Some of the man-made emissions entering the natural environment in the form of fine aerosols are transported over significant distances and cause global pollution. The other part enters drainless reservoirs, where heavy metals accumulate and become a source of secondary pollution, i.e. the formation of dangerous pollutants during physical and chemical processes occurring directly in the environment (for example, the formation of poisonous phosgene gas from non-toxic substances). Heavy metals accumulate in the soil, especially in the upper humus horizons, and are slowly removed by leaching, consumption by plants, erosion and deflation - blowing out of soils.

The period of half-removal or removal of half of the initial concentration is a long time: for zinc - from 70 to 510 years, for cadmium - from 13 to 110 years, for copper - from 310 to 1500 years and for lead - from 740 to 5900 years. In the humus part of the soil, the primary transformation of the compounds found in it occurs.

Heavy metals have a high ability for a variety of chemical, physicochemical and biological reactions. Many of them have variable valency and participate in redox processes. Heavy metals and their compounds, like other chemical compounds, are capable of moving and being redistributed in living environments, i.e. migrate. The migration of heavy metal compounds occurs largely in the form of an organomineral component.

Possible sources of pollution of the biosphere with heavy metals of technogenic origin include enterprises of ferrous and non-ferrous metallurgy (aerosol emissions polluting the atmosphere, industrial effluents polluting surface waters), mechanical engineering (plating baths of copper plating, nickel plating, chrome plating, cadmium plating), factoriesbattery recycling, road transport.

In addition to anthropogenic sources of environmental pollution with heavy metals, there are other natural sources, such as volcanic eruptions: cadmium was discovered relatively recently in the products of the eruption of Mount Etna on the island of Sicily in the Mediterranean Sea. Increased concentrations of toxic metals in the surface waters of some lakes may occur as a result of acid rain, which leads to the dissolution of minerals and rocks washed by these lakes. All these sources of pollution cause an increase in the content of pollutant metals in the biosphere or its components (air, water, soil, living organisms) compared to the natural, so-called background level.

2.1. The entry of heavy metal compounds into the soil

Soil is the main medium into which heavy metals enter, including from the atmospherewith emissions from industrial enterprises, and lead - from vehicle exhaust gases. Heavy metals most often enter the soil from the atmosphere in the form of oxides, where they gradually dissolve, turning into hydroxides, carbonates or into the form of exchangeable cations. Soil withIt is a source of secondary pollution of surface air and waters that flow from it into the World Ocean. From the soil, heavy metals are absorbed by plants, which then become food for more highly organized animals.

The duration of residence of polluting components in the soil is much higher than in other parts of the biosphere, which leads to changes in the composition and properties of the soil as a dynamic system and ultimately causes an imbalance in ecological processes.

Under normal natural conditions, all processes occurring in soils are in balance. Changes in the composition and properties of the soil can be caused by natural phenomena, but most often humans are to blame for disturbing the equilibrium state of the soil:

atmospheric transport of pollutants in the form of aerosols and dust (heavy metals);

non-terrestrial pollution - dumps of large-scale industries and emissions from fuel and energy complexes;

plant litter. Toxic elements in any state are absorbed by the leaves or deposited on the leaf surface. Then, when the leaves fall, these compounds enter the soil .

The determination of heavy metals is primarily carried out in soils located in areas of environmental disaster, on agricultural lands adjacent to soil pollutants with heavy metals, and in fields intended for growing environmentally friendly products.

If soils are contaminated with heavy metals and radionuclides, it is almost impossible to clean them. So far, the only way is known: to sow such soils with fast-growing crops that produce large phytomass. Such crops that extract heavy metals must be destroyed after ripening. It takes decades to restore contaminated soils.

2.2. The entry of heavy metal compounds into water bodies

Metal ions are essential components of natural bodies of water. Depending on environmental conditions (pH, redox potential), they exist in different oxidation states and are part of a variety of inorganic and organometallic compounds. Many metals form fairly strong complexes with organic matter; These complexes are one of the most important forms of migration of elements in natural waters.

Heavy metals as microelements are constantly found in natural reservoirs and the organs of aquatic organisms. Depending on geochemical conditions, wide fluctuations in their level are observed.

At the same time, heavy metals and their salts are widespread industrial pollutants. They enter reservoirs both from natural sources (rocks, surface layers of soil and groundwater), and from wastewater from many industrial enterprises and atmospheric precipitation, which are polluted by smoke emissions. For example, natural sources of lead entering surface waters are the dissolution processes of endogenous (galena) and exogenous (anglesite, cerussite, etc.) minerals. A significant increase in the content of lead in the environment (including in surface waters) is associated with the combustion of coal, the use of tetraethyl lead as an anti-knock agent in motor fuel, and the discharge into water bodies with wastewater from ore processing factories, some metallurgical plants, chemical plants, mines, etc.

2.3. Release of heavy metal compounds into the atmosphere

Road transport that runs on liquid fuel (gasoline, diesel fuel and kerosene), combined heat and power plants (CHP) and combined heat and power plants (CHP) are one of the main sources of air pollution. Car exhaust emissions contain heavy metals, including lead.Higher concentrations of lead in the atmospheric air of cities with large industrial enterprises.

Intake of heavy metals into the atmosphere, % of the amount

Source

Heavy metal

Сd

Common natural source

26,3

29,0

4,5

81,0

Anthropogenic source

73,7

71,0

95,5

19,0

2.4. The entry of heavy metal compounds into living organisms

Plant foods are the main source of heavy metals in the body of humans and animals. According to data, 40–80% of heavy metals come from it, and only 20–40%. - with air and water. The chemical composition of plants, as is known, reflects the elemental composition of soils. Therefore, the excessive accumulation of heavy metals by plants is primarily due to their high concentrations in soils. Despite the significant variability of various plants to the accumulation of heavy metals, the bioaccumulation of elements has a certain tendency, which allows them to be ordered into several groups:

1) Cd, Cs, Rb - elements of intense absorption;

2) Zn, Mo, Cu, Pb, Co, As – average degree of absorption;

3) Mn, Ni, Cr – weak absorption;

4) Se, Fe, Ba, Te are elements that are difficult for plants to access. Another way for heavy metals to enter plants is through foliar absorption from air currents.

The entry of elements into plants through the leaves occurs mainly through non-metabolic penetration through the cuticle. Heavy metals absorbed by the leaves can be transferred to other organs and tissues and included in the metabolism. Lead and cadmium are highly toxic metals. In roadside plants, the amount of lead is sharply increased, it is 10–100 times higher than in plants growing far from roads. A large amount of cadmium is found in plants growing near highways. So, for example, in the needles of common spruce growing near roads, the amount of cadmium increases by 11–17 times.

The entry of heavy metals into plants can occur directly from the air with dust deposited on leaves and needles and translocation from the soil: the proportion of heavy metals in the composition of dust on the surface of leaves near the source is on average 30% of the total content of heavy metals in them. In depressions and on the windward side, this share can reach up to 60%. As you move away from the source, the role of atmospheric pollution noticeably decreases.

Chapter III . Determination of the presence of heavy metal compounds in the environment and their impact on living organisms

The method for determining the content of heavy metal ions is reduced to the analysis of melt water, water from a reservoir or water extracts using high-quality reagents.

Qualitative determination of lead ions P b 2+

Potassium iodide gives a characteristic yellow lead iodide precipitate in solution with lead ions.

Progress of the study :

1 ml of water, melt water or aqueous extract from each sample is poured into test tubes and 1 ml of KI solution and 1 ml of 6% HNO are added 3. The tubes with the contents are left for a day. In the presence of lead ions, a yellow precipitate forms when the lead content is 60 μg in the sample. At lower concentrations, the contents of the test tube turn yellow.:

R b 2+ + I - = R b I 2

Qualitative determination of iron ions

Total iron

Ammonium rhodanideN.H. 4 SCN or potassium KSCN form in an acidic environment withFe 3+ iron thiocyanates, colored blood red. Depending on the concentration of thiocyanate ion, complexes of different types can be formed.composition:

Fe 3+ +SCN - = 2+

Fe 3+ + 2 SCN - = +

Fe 3+ + 3 SCN- = Fe( SCN) 3

To 1 ml of test water add 2-3 drops of hydrochloric acid solution and2- 3 drops of reagent solution.

Atiron content0.1 mg/lappearspinkcoloring,Aatmorehigh content –red.

The maximum permissible concentration of total iron in reservoir water and drinking water is 0.3 mg/l, the limiting organoleptic hazard indicator.

Iron(II)

Potassium hexacyanoferrate(III)K 3 [ Fe( CN) 6 ] , in an acidic environment(pH ~ 3) forms with the Fe cation 2+ Turnboule blue sediment dark bluecolors:

3Fe 2+ + 2 3- =Fe 3 2

To 1 ml of test water add 2-3 drops of sulfuric acid solution and 2-3drops of reagent solution.

Iron(III)

Potassium hexacyanoferrate(II)K 4 [ Fe( CN) 6 ] in a slightly acidic environment with a cationFe 3+ forms a dark blue precipitate of Prussian blue:

4Fe 3+ + 3 4- =Fe 4 3

To 1 ml of test water add 1-2 drops of hydrochloric acid solution and 2 drops of reagent solution.

For the qualitative determination of lead and iron ions, the following equipment, reagents and materials were used.

Equipment: training scales, weights, ruler, tripod with coupling and foot, burette with stopcock, 2 ml measuring pipette, 100 ml and 50 ml beakers, 100 ml measuring cylinder, 250 ml round flat-bottomed flasks, rubber stoppers, conical funnels , filter paper, test tube rack, test tubes, scissors, spatula, glass rods, glass tubes, Petri dishes.

Reagents: concentrated nitric acid (HNO 3 ), potassium iodide solution (KI), 6% nitric acid solution (HNO 3 ), hydrogen peroxide (H 2 ABOUT 2 ), potassium thiocyanate (solution) (KSCN), sulfuric acid (solution) (H 2 SO 4 ), hexacyanoferrate (III) potassium (K 3 [ Fe( CN) 6 ]), hexacyanoferrate (II) potassium (K 4 [ Fe( CN) 6 ), hydrochloric acid (solution) (HCl), boiled water.

Materials: seeds of watercress, thalli of lichens Xanthoria wallata (goldenwort) and Parmelia furrowata.

3.1. Heavy metal compounds in soil

3.1.1. Methodology for determining the presence of heavy metal compounds in soil

Soil samples (approximately 100 g each) were taken at two points: near the highway in the immediate vicinity (Appendix, Fig. 1), in a coniferous forest belt far from the road (Appendix, Fig. 2), where mainly pine and spruce trees grow, and Some deciduous species are also found.

The soil was dried for 5 days.

We weighed 10 g of each soil sample on a pre-balanced balance.

The samples were transferred into round flat-bottomed flasks with designations (soil sample taken near the road - “p road”; soil sample taken in a forest belt - “p forest”). Pour 50 ml of boiled water into each flask, add 1 drop of concentrated nitric acid HNO 3 , shaken for 5 minutes. Left for a day (Appendix, Fig. 3).

Soil extracts were filtered into labeled beakers, using a different filter for each extract (Appendix, Fig. 4).

The resulting filtrates were used to carry out a qualitative determination of the content of lead and iron ions in the soil according to a previously described method.

3.1.2. Results of analysis of the content of heavy compounds

metals in soil

Analysis of samples for the content of lead ions in the soil gave the following results. In a test tube with an aqueous extract from soil taken near the road, no obvious precipitate formed, but the contents of the test tube turned a rich golden brown color, which indicates a fairly significant content of lead ions in this soil sample. In a test tube with an aqueous extract of soil taken in a forest belt, no sediment or obvious change in color was noted (the soil extract initially had a weak pale yellow color, which can be explained by the coloring property of the organic matter contained in the forest soil) (Appendix, Fig. 5, 6) .

Analysis of samples for the content of iron ions in the soil did not give visible changes: when adding reagents, there was no change in color and no precipitation occurred.

3.2. Compounds of heavy metals in natural waters

3.2.1. Methodology for determining the presence of heavy metal compounds in natural waters

1. We took a water sample from the reservoir into a clean container (Appendix, Fig. 7).

2. Filtered a sample of water taken from the lake into a beaker to clean the sample from mechanical impurities.

3. The resulting filtrate was used to carry out a qualitative determination of the content of lead and iron ions in the lake water according to a previously described method.

3.2.2. Compound content analysis results

heavy metals in natural waters

Analysis of samples for the content of lead ions in water gave the following result: no obvious sediment formed, but the contents of the test tube turned a barely visible pale yellow color (Appendix, Fig. 8).

Analysis of samples for the content of iron ions in water did not give visible results: when adding reagents, there was no change in color and no precipitation occurred.

3.3. Heavy metal compounds in the atmosphere

3.3.1. Methodology for determining the presence of heavy metal compounds in the atmosphere

Snow cover

Snow cover accumulates in its composition almost all substances entering the atmosphere. In this regard, it has a number of properties that make it a convenient indicator of pollution not only of precipitation itself, but also of atmospheric air. During the formation of snow cover, due to the processes of dry and wet precipitation of impurities, the concentration of pollutants in the snow turns out to be 2-3 orders of magnitude higher than in the atmospheric air. Therefore, analysis of snow samples gives results with a high degree of reliability. When sampling fromneg must be taken throughout the depth of its deposits into the containers provided for this purpose.

We took dishes for taking snow samples and made markings. Snow samples were taken in 3 places: on the side of the road (Appendix, Fig. 9), in the yard near the house (Appendix, Fig. 10), in a forest belt (Appendix, Fig. 11).

We filled the containers with snow.

We delivered snow to the classroom.

After the snow melted, the melt water was filtered to remove mechanical impurities from the samples (Appendix, Fig. 12).

The resulting filtrates from three samples were used to carry out a qualitative determination of the content of lead and iron ions in the snow (and, therefore, in the atmosphere) according to the previously described method (Appendix, Fig. 13, 14).

Lichens

The sensitivity of lichens to atmospheric pollution has been noted for a long time. Lichens are capable of accumulating elements from the environment in quantities that far exceed their physiological needs. The absence of special organs for water and gas exchange and the extremely low ability for autoregulation lead to a high degree of correspondence between the chemical composition of lichens and their environment. This quality has determined the widespread use of lichens as accumulative bioindicators of environmental pollution with heavy metals. It has been established that Co, Ni, Mo, Au are present in lichens in the same concentrations as in higher plants, and the content of Zn, Cd, Sn, Pb is much higher.

To qualitatively determine the content of heavy metal ions, we used the following method:

Lichens were collected from silver birch (Betula pendula ) and goat willow (Salix caprea ) at a height of 0.5 to 1 meter.

If possible, lichen samples were taken without bark; if it was impossible to separate the thallus from the bark, they were cut off along with it.

For analysis, thalli of the lichens Xanthoria wallata and Parmelia sulcata were collected, and a visual assessment of the condition of the thalli during collection was also carried out.

Sampling was carried out in two places: on trees near the highway (Appendix, Fig. 15, 16) and on trees growing in the forest belt (Appendix, Fig. 17).

Lichens of the same species, collected from one tree, were placed in a common bag with designations (Appendix, Fig. 18).

In the office, 25 g of lichen thalli of each type from each sample were weighed on scales and crushed.

Two weights of lichen thalli of both species (xanthoria + parmelia for each sampling site) were placed in round flat-bottomed flasks, 50 ml of boiled water was poured into each flask, 1 drop of concentrated nitric acid was added, shaken for 5 minutes, left for a day (Appendix, Fig. 3).

Then the aqueous extract was filtered and the resulting filtrates were used forconducting a qualitative determination of the content of lead and iron ions in lichen thalli (and, therefore, in the atmosphere) according to the previously described method.

3.3.2. Compound content analysis results

heavy metals in the atmosphere

Snow cover

Analysis of samples for the content of lead ions in snow gave the following results. In a test tube with melt water filtrate from snow taken on the side of the road (sample No. 3), there was no obvious precipitate, but the contents of the test tube turned bright golden, which indicates a significant content of lead ions in this snow sample. In a test tube with a filtrate of melt water from snow taken in a forest belt far from the road (sample No. 2), no sediment precipitated; the contents of the test tube acquired a faint pale yellow color. In a test tube with a filtrate of melt water from snow taken in the backyard near the house (sample No. 1), no sediment formed; the contents of the test tube turned pale yellow (Appendix, Fig. 8).

Analysis of samples for the content of iron ions in snow did not give visible results: when adding reagents, there was no change in color and no precipitation occurred.

Lichens

When visually assessing the state of the lichen thalli of Xanthoria walla and Parmelia sulciforma, some inhibition of the general condition of lichen thalli growing on trees near the road was noted: the thalli are small in size, somewhat thickened, their leafy nature is weakly traced, the thalli are firmly attached to the bark of trees (Appendix, Fig. 19). All this indicates the presence in the atmosphere of the study area (roadside zone) of substances that adversely affect living organisms - lichens.

Analysis of samples for the content of lead ions in lichen thalli gave the following results. In a test tube with an aqueous extract from lichen thalli collected from trees near the highway, no precipitate fell out, but the contents of the test tube turned into a faintly distinguishable pale yellow color, which indicates lead ions contained in the atmosphere and their accumulation in lichen thalli. In a test tube with an aqueous extract from lichen thalli collected from trees in a forest belt far from the highway, no precipitate fell out, and no color change was noted (Appendix, Fig. 6).

The analysis of samples for the content of iron ions in lichen thalli did not give visible results: when reagents were added, there was no change in color and precipitation.

General conclusion: Analyzing the results obtained in all types of experiments (the content of lead ions in soil, water, snow and lichens), we conclude that lead ions are contained in the environment. Moreover, the content of lead ions is greater the closer the sampling area is to places with high human activity (in our case, a highway), which is primarily explained by the entry of lead ions into the environment as part of vehicle exhaust gases. The negative result of tests for the content of iron ions in all variants of the experiments is most likely associated not with the complete absence of iron in the environment, but with its very low content, which cannot be determined by the methods we use and the reagents available in the laboratory.

3.4. Heavy metal compounds and living organisms

3.4.1. Methodology for determining the effects of heavy metal compounds on organisms

We used watercress as a test organism (Appendix, Fig. 20).

Watercress is an annual vegetable plant that is highly sensitive to soil contamination with heavy metals, as well as to air pollution from gaseous emissions from vehicles. This bioindicator is characterized by rapid seed germination and almost one hundred percent germination.

In addition, the shoots and roots of this plant undergo noticeable morphological changes under the influence of pollutants. Growth retardation and curvature of shoots, reduction in the length and weight of roots.

Watercress as a bioindicator is also convenient because the effect of stress can be studied simultaneously on a large number of plants in a small work area. The very short duration of the experiment is also attractive. Watercress seeds germinate on the second or third day.

To determine the impact of heavy metal ions on living organisms (cress), we took samples of melt water, samples of which had already been analyzed for the content of lead and iron ions using high-quality reagents.

Circles cut from filter paper according to the size of the Petri dishes were placed at the bottom of the Petri dishes; Petri dishes were numbered.

3 ml of melt water from the corresponding sample was poured into each Petri dish (the filter paper was completely wetted) (Appendix, Fig. 21).

Watercress seeds were placed on filter paper (20 pieces in each Petri dish) and covered with lids (Appendix, Fig. 22, 23).

After 3 days, a morphometric assessment of the lettuce seedlings was carried out (the length of the roots was measured) (Appendix, Fig. 24, 25).

The data was entered into a table, the average value of root lengths for each option was found, and conclusions were drawn

3.4.2. Compound Exposure Results

heavy metals on living organisms

Morphometric parameters of watercress seedlings

(length of spines in mm)

p/p

Sample No. 1 (snow from the yard)

Sample No. 2 (snow from the forest belt)

Sample No. 3 (snow from the road)

AVERAGE VALUE

44,74

56,24

22,4

Conclusions: lead ions contained in melt water have a depressing effect on the vital processes of organisms, the negative effect is the greater, the higher the content of lead ions in melt water. This follows from the results obtained. In the variant of experiment No. 3 (road) (Appendix, Fig. 26), morphometric changes are clearly noted: the length of the roots sharply decreases - by 20 mm or more according to average indicators. In addition, germination rate was 90%. In the variants of experiments No. 1 (yard) (Appendix, Fig. 27) and No. 2 (forest belt) (Appendix, Fig. 28), germination was 95% and 85%, respectively. Such a quantitative spread in germination in options No. 1 and No. 2 can be associated with the overall germination of seed (random factor) and a relatively small sample. The lower value of the average root length in variant No. 1 in comparison with variant No. 2 is explained by the high presence of lead ions in melt water. The negative effect of lead ions on living organisms was precisely established during the experiment.

Conclusion

The environment is a home for living organisms, and it also provides organisms with all the substances necessary for normal life. At the same time, living organisms absorb from their environment not only what they need; there is a joint absorption of a whole complex of substances and elements, some of which are not only not useful, but also have a depressing, poisonous effect on organisms; among such substances, heavy metal compounds. But usually the natural background of heavy metals in the environment is quite low, therefore, the negative impact of their compounds on plants and animals is insignificant.

Recently, the environment has been experiencing a very strong impact from humans, who negatively affect its condition and lead to severe pollution.

In the course of our research, it was found that the degree of anthropogenic impact on the environment in the area of pollution with heavy metal compounds is high. Ions of the heavy metal lead are present in the environment of the study area, and their content increases when approaching areas with a high degree of anthropogenic impact - near highways in the study area. At a distance from roads, the concentration of metal ions decreases, but, nevertheless, the content of heavy metal compounds will be higher than the natural background, because pollution spreads over large areas with moving air masses, with flows of ground and surface water, and with precipitation. Negative tests for the presence of iron ions do not mean its absence; in rural areas there are practically no sources of its entry into the environment, therefore the content of iron ions is extremely low to establish its presence. It was also found that heavy metal ions have a general inhibitory effect on the processes of growth and development of living organisms at relatively low concentrations.

The practical significance of the work lies in the fact that the results obtained can be used: when conducting classroom hours, extracurricular activities and classes devoted to problems of the ecological state of the environment (in particular, the study area); when developing booklets on the topic “The environment and the problem of its pollution by heavy metal compounds” to inform the population (including installing a sign near the reservoir “Fishing is prohibited!”). The practical results of research work can be used when writing an article for a newspaper to highlight the problem of environmental pollution.

Bibliography

Ashikhmina T.Ya. School environmental monitoring. Educational and methodological manual. M.: AGAR, 2006. 38 p.

Mansurova S.E. “We monitor the environment of our city”, M., “Vlados”, 2001.

Muravyov A.G., Pugal N.A., Lavrova V.N. Ecological Workshop: Textbook with a set of instruction cards / Ed. Ph.D. A.G. Muravyova. – 2nd ed., rev. – St. Petersburg: Christmas+, 2012. – 176 p.: ill.

Heavy metals as an environmental hazard factor: Guidelines for independent work on ecology for 3rd year full-time students / Compiled by: Yu.A. Kholopov. – Samara: SamGAPS, 2003.

Application

Fig.1. Taking a soil sample from the side of the road

Fig.2. Soil sampling in a forest belt

Fig.3. Obtaining aqueous extracts from soil and from lichen thalli

Fig.4. Obtaining soil extract filtrate

Fig.5. Soil extract filtrates

Fig.6. Results of detection of lead ions in aqueous extracts from lichen thalli and soil

Fig.7. Taking a water sample from the lake

Fig.8. Results of detection of lead ions in melt water and lake water

Fig.9. Taking a snow sample from the side of the road

Fig. 10. Taking a snow sample in the yard near the house

Fig. 11. Taking a snow sample in a forest belt

Fig. 12. Obtaining melt water filtrate

Fig. 13. Measuring a sample of melt water from a burette into a test tube

Fig. 14. Taking the required amount of reagent into a measuring pipette

Fig. 15. Collection of parmelia furrow lichen near the road

Fig. 16. Collection of Xanthoria wallii lichen near the road

Rice. 17. Collection of Parmelia furrow lichen in a forest belt

Fig. 18. Collected samples of lichen thalli

Fig. 19. Lichens on the trunk of a birch tree growing near the road

Fig.20. Test organism – watercress

Fig.21. Preparing to sow seeds

Fig.22. Sowing watercress seeds

Fig.23. Watercress seeds in Petri dishes

Fig.24. Measuring the root lengths of watercress seedlings

Fig.25. Measuring the root length of a watercress seedling

Fig.26. Watercress sprouts

(experimental option - snow taken near the road)

Fig.27. Watercress sprouts

(experimental option - snow taken from the yard of the house)

Fig.28. Watercress sprouts

(experimental version - snow taken from the forest belt)

Lesson - workshop

(project activity of 9th grade students at a general chemistry lesson when studying elements - metals)

“Study of the content of lead ions in soil and plant samples of the village of Slobodchiki and its effect on the human body.”

Prepared and carried out

teacher of biology, chemistry

Sivokha Natalya Gennadievna

The purpose of the lesson:

Show the effect of heavy metals on human health using the example of lead and study the ecological situation of the village of Slobodchiki by determining lead ions in soil and plant samples.

Lesson objectives:

Summarize the knowledge gained about heavy metals. To introduce students in more detail to lead, its biological role and toxic effects on the human body;

To expand students’ knowledge about the relationship between the use of lead metal and the ways it enters the human body;

Show the close relationship between biology, chemistry and ecology, as subjects that complement each other;

Fostering a caring attitude towards your health;

Instilling interest in the subject being studied.

Equipment: computer, multimedia projector, presentations of mini-projects completed by students, a stand with test tubes, a glass rod, a funnel with a filter, 50 ml beakers, filter paper, a measuring cylinder, a scale with weights, filter paper, scissors, an alcohol lamp or a laboratory tile.

Reagents: ethyl alcohol, water, 5% sodium sulfide solution, potassium iodide, soil samples, vegetation samples prepared by the teacher.

Why is a group of elements called "heavy metals"? (all these metals have a large mass)
What elements are heavy metals? (iron, lead, cobalt, manganese, nickel, mercury, zinc, cadmium, tin, copper, manganese)
What effect do heavy metals have on the human body?

In ancient Rome, noble people used plumbing made from lead pipes. Molten lead was poured into the joints of stone blocks and water supply pipes (it’s not for nothing that the word plumber in English means “plumber”). In addition, slaves used cheap wooden utensils and drank water directly from wells, while slave owners used expensive lead vessels. The life expectancy of wealthy Romans was much shorter than that of slaves. Scientists have suggested that the cause of early death was lead poisoning from the water used for cooking. However, this story has a continuation. In the state of Virginia (USA), burials of those years were investigated. It turned out that in fact the skeletons of slave owners contain significantly more lead than the bones of slaves. Lead was known for 6-7 thousand years BC. e. the peoples of Mesopotamia, Egypt and other countries of the ancient world. It was used to make statues, household items, and writing tablets. The alchemists called lead Saturn and designated it as the sign of this planet. Lead compounds - “lead ash” PbO, lead white 2PbCO3 Pb (OH)2 were used in Ancient Greece and Rome as components of medicines and paints. When firearms were invented, lead was used as a material for bullets. The toxicity of lead was noted as early as the 1st century BC. n. e. Greek physician Dioscorides and Pliny the Elder.

The volume of modern lead production is more than 2.5 million tons per year. As a result of industrial activities, more than 500-600 thousand tons of lead enter natural waters annually, and about 400 thousand tons settle through the atmosphere onto the Earth's surface. Up to 90% of the total amount of lead emissions comes from gasoline combustion products containing lead compounds. The main part of it enters the air with the exhaust gases of vehicles, a smaller part - when burning coal. From the air near the soil layer, lead settles into the soil and enters the water. The lead content in rain and snow water ranges from 1.6 µg/l in areas remote from industrial centers to 250-350 µg/l in large cities. It is transported through the root system to the above-ground part of plants. At 23 m from a road with traffic volumes of up to 69 thousand cars per day, bean plants accumulated up to 93 mg of lead per 1 kg of dry weight, and at 53 m – 83 mg. Corn growing 23 m from the road accumulated 2 times more lead than 53 m. Where the road network is very dense, 70 mg of lead per 1 kg of dry matter was found in fodder beet tops, and 90 mg in collected hay. Lead enters the body of animals with plant foods. Lead content in various products (in mcg); pork meat - 15, bread and vegetables - 20, fruits - 15. Lead enters the human body with plant and animal foods, settling up to 80% in the skeleton, as well as in the internal organs. Humans, who represent one of the last links in the food chain, are at greatest risk from the neurotoxic effects of heavy metals.

Determination of lead ions in plant samples.

Purpose of the work: to determine the presence of ions in plant samples.

Equipment: two beakers of 50 ml each, a measuring cylinder, a scale with weights, a glass rod, a funnel, filter paper, scissors, an alcohol lamp or a laboratory hotplate.

Reagents: ethyl alcohol, water, 5% sodium sulfide solution

Research methodology.

1. Weigh 100 g. plants, preferably of the same species, for a more accurate result (plantain), at different distances from each other.

2. Grind thoroughly, add 50 ml to each sample. mixture of ethyl alcohol and water, stir so that the lead compounds go into solution.

3. Filter and evaporate to 10 ml. Add the resulting solution dropwise to a freshly prepared 5% sodium sulfide solution.

4. If there are lead ions in the extract, a black precipitate will appear.

Determination of lead ions in soil.

The purpose of the work: to determine the presence of lead ions in the soil.

Equipment: two beakers of 50 ml each, a measuring cylinder, scales with weights, a glass rod, a funnel, filter paper.

Reagents: potassium iodide, water.

Research methodology:

1. Weigh 2 g of soil and pour it into a beaker. Then add 4 ml of water and stir well with a glass rod.

2.Filter the resulting mixture.

3. Add 1 ml of 5% potassium iodide to the filtrate. When lead ion reacts with potassium iodide, a yellow precipitate is formed.

Pb +2 + 2 I - = P bI 2 (yellow precipitate)

4.Dip the edge of a 1 cm strip of filter paper into the resulting solution. When the substance rises to the middle of the paper, take it out and put it to dry. The dried filter paper will show a clear trace of sediment. Over time (after 3-5 days), the yellow color of lead iodide will appear brighter.

Creation date: 2013/12/30

Currently, the issue of water purification and the quality of household filters worries many people.

Drinking water quality research

For the study, samples of tap water and purified water using household filters Aquaphor (jug), Aquaphor (tap), Barrier (jug) were taken. The following indicators were studied: pH value, content of zinc (II), copper (II), iron (III) ions, water hardness.

pH value

5 ml of the test water is poured into the test tube, the pH is determined using a universal indicator, and the pH value is assessed using a scale:

Pink-orange - pH=5;
Light yellow - pH=6;
Light green - pH=7;
Greenish-blue - pH=8.

Filtered water has a slightly acidic reaction medium, while the medium of unfiltered water is close to neutral.

Determination of iron ions

To 10 ml of the test water, 1-2 drops of HCl (1:2) and 0.2 ml (4 drops) of a 50% solution of potassium thiocyanate KNCS were added. The mixture is mixed and the color development is observed. This method is sensitive and can detect up to 0.02 mg/l of iron ions.

Fe3+ + 3NCS- = Fe(NCS)3

Lack of color - less than 0.05;
Barely noticeable yellowish-pink - from 0.05 to 0.1;
Weak yellowish-pink - from 0.1 to 0.5;
Yellowish-pink - from 0.5 to 1.0;
Yellowish-red - from 1.0 to 2.5;
Bright red more than 2.5.

The highest concentration of iron (III) ions is in unfiltered water.

Determination of lead ion (qualitative)

Potassium iodide gives a characteristic PbI2 precipitate in solution with lead ions. A little KI is added to the test solution, after which, by adding CH3COOH, the contents of the test tube are heated until the initially slightly characteristic yellow precipitate of PbI2 is completely dissolved. The resulting solution is cooled under the tap, and PbI2 falls out again, but in the form of beautiful golden crystals Pb2+ +2I- = PbI2. Purified and unfiltered water does not contain lead (II) ions.

Determination of copper ion (qualitative)

5 ml of the water to be tested is placed in a porcelain cup, evaporated to dryness, then 1 drop of concentrated (25%) ammonia solution is added. The appearance of an intense blue color indicates the presence of copper ions. 2Сu2+ +4NH4ОН = 22+ +4H2O

Determination of water hardness

100 ml of test water is added to a 250 ml conical flask, 5 ml of ammonia buffer solution is added, and an indicator (eriochrome black) is added at the tip of a spatula. Then the solution should be mixed and slowly titrated with a 0.05 N solution of Trilon B until the color of the indicator changes from cherry to blue.

Preparation of the eriochrome black (dry) indicator: for this, 0.25 g of the indicator is mixed with 50 g of dry sodium chloride, previously thoroughly ground in a mortar.

Preparation of a buffer solution: 10 g of ammonium chloride (NH4Cl) is dissolved in distilled water, 50 cm3 of 25% ammonia solution is added and adjusted to 500 cm3 with distilled water.

Preparation of a 0.05 N solution of Trilon B: 9.31 g of Trilon B is dissolved in distilled water and adjusted to 1 dm3. The solution is stable for several months.

The total stiffness is calculated using the formula:

F mg-eq/l = (Vml*N g-eq/l*1000 mg-eq/g eq) / V1ml,

where: V is the volume of Trilon “B” solution used for titration, ml.

N - normality of Trilon "B" solution g-eq/l.

V1 is the volume of the test solution taken for titration, ml.

When assessing water hardness, it is characterized as follows:

very soft - up to 1.5 mEq/l;
soft - from 1.5 to 4 mEq/l;
medium hardness - from 4 to 8 mEq/l;
hard - from 8 to 12 mEq/l;
very hard - more than 12 mEq/l.

Tap water is hard, water that has been purified with a Barrier filter has medium hardness, water that has been purified with an Aquaphor filter (jug and tap) is soft and of medium hardness.

Can water be harmful to health? Tap water can contain very dangerous and even toxic substances, water treatment plants are worn out, and water, before entering the house, must travel a long way through old water pipes, where it becomes contaminated with heavy metal salts and inorganic iron (rust). The need for clean water is constantly increasing, and the source water entering treatment plants becomes dirtier from year to year. After purification, the water becomes drinkable, but smells of bleach. The concentration of chlorine is not dangerous for a healthy person, but for some categories of sick people the presence of chlorine, even in small concentrations, greatly worsens their health. All this adversely affects human health. It is necessary to use filters for water purification at home. The quality of purified water at home is better than the quality of tap water. Using household filters, you can purify water that contains not only mechanical particles (sand, rust, etc.), but also various organic and inorganic compounds that are hazardous to health. Water that has been purified through a filter becomes less hard.

Filters completely remove chlorine from water, which kills bacteria and plays the role of a “preservative.” But you need to use purified water as quickly as possible after filtration, because in water devoid of a “preservative”, bacteria begin to multiply especially quickly in a clean and warm environment (water) that is pleasant for them.

So what is water? The question is far from simple... One thing we can definitely say is that water is the most unique substance on earth, on which the state of health depends.

Determination of pH of the test water: