Qualitative analysis of lead content in biological material. Determination of lead in urban vegetation

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Course work

Determination of lead in urban vegetation

Introduction

lead titrimetric metal reagent

Lead is a toxic substance, the accumulation of which affects whole line systems of the body and which is especially harmful for young children.

Childhood exposure to lead is estimated to contribute to approximately 600,000 new cases of intellectual disability in children each year.

Lead exposure is estimated to cause 143,000 deaths per year, with the heaviest burden in developing regions.

In the body, lead enters the brain, liver, kidneys and bones. Over time, lead accumulates in teeth and bones. Human exposure is typically determined using blood lead levels.

There is no known level of lead exposure that is considered safe.

The main sources of lead pollution are motor vehicles using lead - containing gasoline, metallurgical plants, smoke sources such as thermal power plants, etc.

Plants absorb lead from soil and air.

They perform a useful role for humans, acting as adsorbents for lead in the soil and air. Dust containing lead accumulates on plants without spreading.

According to the data on the content of mobile forms of heavy metals in plants, one can judge the contamination of a certain space with them.

In this course work The lead content in the vegetation of the urban area is being studied.

1. Leeliterature review

The literature review is based on the book “Analytical Chemistry of Elements. Lead".

1. 1 AboutGeneral information about lead

Svinemts (lat. Plumbum; denoted by the symbol Pb) is an element of the 14th group (outdated classification - the main subgroup of group IV), the sixth periodic table chemical elements D.I. Mendeleev, with atomic number 82 and thus contains the magic number of protons. The simple substance lead (CAS number: 7439-92-1) is a malleable, relatively fusible metal of a silvery-white color with a bluish tint. Known since ancient times.

The lead atom has the electronic structure 1s 2 2s 2 p 6 3s 2 p 6 d 10 4s 2 p 6 d 10 f 14 5s 2 p 6 d 10 6s 2 p 2 . The atomic mass is assumed to be 207.2, but its fluctuations by 0.03 - 0.04 a.c. are possible.

Lead is a component of more than 200 minerals, but only three of them (galena, anglesite, cerussite) are found in nature in the form of industrial deposits of lead ores. The most important of these is galena PbS (86.5% Pb).

Under the influence of substances dissolved in natural waters and during weathering, it turns into anglesite PbSO 4 (63.3% Pb), which, as a result of double exchange with calcium and magnesium carbonates, forms cerussite PbCO 3 (77.5% Pb).

In terms of industrial production, lead ranks fourth in the group of non-ferrous metals, second only to aluminum, copper and zinc.

To obtain lead highest value have polymetallic sulfide and mixed ores, since pure lead ores are rare.

It is used for radiation protection purposes, as a structural material in chemical industry, for the production of protective coatings for electrical cables and battery electrodes. Large quantities of lead are used to make various alloys: with bismuth (coolant in nuclear technology), with tin and small additions of gold and copper (solders for the manufacture of printed circuits), with antimony, tin and other metals (solders and alloys for printing and antifriction purposes). The ability to form intermetallic compounds is used to produce lead telluride, from which IR ray detectors and converters of thermal radiation energy into electrical energy are prepared. Large share lead is used for the synthesis of organometallic compounds.

Many lead - containing organic compounds are products of “minor” chemistry, but are of great practical importance. These include lead stearate and phthalate (thermal and light stabilizers for plastics), basic lead fumarate (thermal stabilizer for electrical insulators and vulcanizing agent for chlorosulfopolyethylene), lead diamyldithiocarbamate (multifunctional lubricating oil additive), lead ethylenediaminetetraacetate (radiocontrast agent), lead tetraacetate (oxidizing agent in organic chemistry). Among the practically important inorganic compounds we can name lead oxide (used in the production of glasses with a high refractive index, enamels, batteries and high-temperature lubricants); lead chloride (production of current sources); basic carbonate, lead sulfate and chromate, red lead (paint components); titanate - zirconate. lead (production of piezoelectric ceramics). Lead nitrate is used as a titrant.

The exceptional diversity and importance of the mentioned applications of lead have stimulated the development of numerous methods for the quantitative analysis of various objects. 1.2. Lead content in natural objects

The earth's crust contains 1.6*10 -3% by mass Pb. The cosmic abundance of this element, according to various authors, varies from 0.47 to 2.9 atoms per 106 silicon atoms. For solar system the corresponding value is 1.3 atoms per 10 6 silicon atoms.

Lead is found in high concentrations in many minerals and ores, in micro- and ultra-microquantities - in almost all objects of the surrounding world.

Other objects contain lead (% by weight); rain water - (6-29) *10 -27, water open sources- 2 * 10 -8, sea waters - 1.3 open ocean waters on the surface - 1.4 * 10 -9, at a depth of 0.5 and 2 km - 1.2 * 10 -9 and 2 * 10 -10, respectively , granites, black shale, basalts - (1 - 30)*10 -4, sedimentary clay minerals - 2*10 -3, volcanic rocks of the Pacific belt - 0.9*10 -4, phosphorites - from 5*10 -4 to 3*10 -2 .

Brown coal - from 10 -4 to 1.75 * 10 -2 , oil - 0.4 4 * 10 -4 , meteorites - from 1.4 * 10 -4 to 5.15 * 10 -2 .

Plants: average content - 1*10 -4, in areas of lead mineralization - 10 -3, food 16*10 -6, puffball mushrooms collected near the highway - 5.3*10 -4, ash: lichens - 10 - 1, coniferous trees - 5*10 -3, deciduous trees and shrubs - up to 3*10 -3. General content lead (in tons): in the atmosphere - 1.8 * 10 4 , in soils - 4.8 * 10 9 , in sediments - 48 * 10 12 , in ocean waters - 2.7 * 10 7 , in river waters and lakes - 6.1 * 10 -4 , in groundwater - 8.2 * 10 4 , in water and land organisms: living - 8.4 * 10 4 , dead - 4.6 * 10 6 .

1.2 Issources of lead pollution

Sources of lead in various areas Human and animal habitats are divided into natural (volcanic eruptions, fires, decomposition of dead organisms, sea and wind dust) and anthropogenic (activities of lead producing and processing enterprises, combustion of fossil fuels and waste from its processing).

In terms of the scale of emissions into the atmosphere, lead ranks first among microelements.

A significant portion of the lead contained in coal is released into the atmosphere when burned along with flue gases. The activity of just one thermal power plant, consuming 5000 tons of coal per day, annually releases 21 tons of lead and comparable amounts of other harmful elements into the air. A significant contribution to air pollution with lead comes from the production of metals, cement, etc.

The atmosphere is polluted not only by stable but also by radioactive isotopes of lead. Their source is radioactive inert gases, of which the longest-living, radon, even reaches the stratosphere. The resulting lead partially returns to the earth with precipitation and aerosols, polluting the soil surface and water bodies.

1.3 Thattoxicity of lead and its compounds

Lead is a poison that affects all living things. It and its compounds are dangerous not only due to their pathogenic effect, but also due to the cumulative therapeutic effect, high accumulation rate in the body, low rate and incomplete excretion with waste products. Lead Hazard Facts:

1. Already at a concentration of 10 -4% in the soil, lead inhibits the activity of enzymes, and highly soluble compounds are especially harmful in this regard.

2. The presence of 2*10 -5% lead in water is harmful to fish.

3. Even low concentrations of lead in water reduce the amount of carotenoid and chlorophyll in algae.

4. Many cases of occupational diseases have been registered among those working with lead.

5. Based on the results of 10 years of statistics, a correlation has been established between the number of deaths from lung cancer and the increased content of lead and other metals in the air of areas of industrial enterprises consuming coal and petroleum products.

The degree of toxicity depends on the concentration, physicochemical state and nature of lead compounds. Lead is especially dangerous in a state of molecular ion dispersion; it penetrates from the lungs into the circulatory system and from there is transported throughout the body. Although lead and its inorganic compounds act qualitatively similarly, their toxicity increases in sync with their solubility in biological fluids of the body. This does not diminish the danger of poorly soluble compounds that change in the intestine with a subsequent increase in their absorption.

Lead inhibits many enzymatic processes in the body. With lead intoxication, serious changes occur in the nervous system, thermoregulation, blood circulation and trophic processes are disrupted, the immunobiological properties of the body and its genetic apparatus change.

1. 4 OSadditive and titrimetric methods

1. Gravimetric method - the formation of weight forms of lead with organic and inorganic reagents is used. Among inorganic ones, preference is given to lead sulfate and chromate. Methods based on their precipitation are comparable in selectivity and conversion factor, but the determination of Pb in the form of chromate requires less time. It is recommended to obtain both sediments using “homogeneous” precipitation methods.

Organic reagents provide weight forms suitable for the determination of smaller quantities of Pb, with more favorable conversion factors than lead chromate or lead sulfate.

Advantages of the method: crystallinity of the precipitate and high accuracy of results in the absence of interfering impurities. Relative error of determination 0.0554-0.2015 Pb< 0,3%. С применением микроаппаратуры выполнены определения 0,125-4,528 мг РЬ с относительной погрешностью < 0,8%. Однако присутствие свободной HN0 3 недопустимо, а содержание солей alkali metals and ammonium should be as small as possible.

2. Precipitation titration with visual indicators. Titration with organic and inorganic reagents is used. In the absence of impurity ions precipitated by chromate, direct titrimetric methods with indication of the titration end point (ETP) by a change in the color of methyl red or adsorption indicators are most convenient. The best option for the titrimetric determination of Pb by the chromate method is the precipitation of PbCr0 4 from an acetic acid solution, followed by dissolving the precipitate in 2 M HC1 or 2 M HC10 4, adding excess potassium iodide and titrating the liberated iodine with Na 2 S 2 0 3.

3. Titration with EDTA solutions. Due to the versatility of EDTA as an analytical reagent for most cations, the question arises of increasing the selectivity of Pb determination. To do this, they resort to preliminary separation of mixtures, the introduction of masking reagents and regulation of the reaction of the medium to pH values > 3. Usually, titration is carried out in a slightly acidic or alkaline medium.

The end point of the titration is most often indicated using metallochromic indicators from the group of azo- and triphenylmethane dyes, derivatives of diatomic phenols and some other substances, the colored Pb complexes of which are less stable than ethylenediaminetetraacetate of lead. In weakly acidic media, titrate against 4 - (2-pyridylazo)-resorcinol, thiazolyl-azo-and-cresol, 2 - (5-bromo-2-pyridylazo) - 5-diethylaminophenol, 1 - (2-pyridylazo) - 2-naphthol , 2 - (2-thiazolylazo) - resorcinol, azo derivatives of 1-naphthol4-sulfonic acid, xylenol orange, pyrocatechol violet, methylxylenol blue, pyrogallol and bromopyrogallol red, methylthymol blue, hematoxylin, sodium rhodizonate, alizarin S and dithizone.

In alkaline environments, eriochrome black T, sulfarsazene, 4 - (4,5 - dimegyl-2-thiazolylazo) - 2-methylresorcinol, a mixture of acid alizarin black SN and eriochrome red B, pyrocatecholphthalein, strong solochrome 2 RS, methylthymol blue and murexide ( titration of total amounts of Pb and Cu).

4. Titration with other complexing substances. The formation of chelates with DCTA, TTGA, and sulfur-containing complexing agents is used.

1.5 Fotometric methods of analysisabout light absorption and scattering

1. Determination as sulfide. The origins of this method and its first critical assessment date back to the beginning of our 20th century. The color and stability of PbS sol depend on the particle size dispersed phase, which is influenced by the nature and concentration of dissolved electrolytes, the reaction of the medium and the method of preparation. Therefore, these conditions must be strictly observed.

The method is not very specific, especially in an alkaline environment, but the convergence of results in alkaline solutions is better. In acidic solutions, the sensitivity of determination is lower, but it can be slightly increased by adding electrolytes, for example NH 4 C1, to the analyzed sample. The selectivity of determination in an alkaline medium can be improved by introducing masking complexing agents.

2. Determination in the form of complex chlorides. It has already been indicated that Pb chlorine complexes absorb light in the UV region, and the molar extinction coefficient depends on the concentration of Cl ions - In a 6 M HCl solution, the absorption maxima of Bi, Pb and Tl are sufficiently distant from each other, which makes it possible to simultaneously determine them by light absorption at 323, 271 and 245 nm, respectively. The optimal concentration range for determining Pb is 4-10*10-4%.

3. Determination of Pb impurities in concentrated sulfuric acid is based on the use of characteristic absorption at 195 nm relative to a standard solution, which is prepared by dissolving lead in H2S04 (special purity).

Determination using organic reagents.

4. In the analysis of various natural and industrial objects, the photometric determination of Pb using dithizone, due to its high sensitivity and selectivity, occupies a leading place. In various variants of existing methods, the photometric determination of Pb is performed at the wavelength of the maximum absorption of dithizone or lead dithizonate. Other variants of the dithizone method are described: photometric titration without phase separation and a non-extraction method for the determination of lead in polymers, in which a solution of dithizone in acetone is used as a reagent, diluted with water before use to a concentration of the organic component of 70%.

5. Determination of lead by reaction with sodium diethyldithiocarbamate. Lead is easily extracted by CCl4 in the form of colorless diethyldithiocarbamate at various pH values. The resulting extract is used in the indirect method for determining Pb, based on the formation of an equivalent amount of yellow-brown copper diethyldithiocarbamate as a result of exchange with CuS04.

6. Determination by reaction with 4 - (2-pyridylazo) - resorcinol (PAR). The high stability of the red Pb complex with PAR and the solubility of the reagent in water are the advantages of the method. For the determination of Pb in some objects, for example in steel, brass and bronze, a method based on the formation of a complex with this azo compound is preferable to the dithizone one. However, it is less selective and therefore, in the presence of interfering cations, requires preliminary separation by the HD method or extraction of lead dibenzyldithiocarbamate with carbon tetrachloride.

7. Determination by reaction with 2 - (5-chloropyridip-2-azo) - 5-diethylaminophenol and 2 - (5-bromopyridyl-2-azo) - 5-diethylaminophenol. Both reagents form 1:1 complexes with Pb with almost identical spectrophotometric characteristics.

8. Determination by reaction with sulfarsazene. The method uses the formation of a reddish-brown water-soluble complex of composition 1: 1 with an absorption maximum at 505-510 nm and a molar extinction coefficient of 7.6 * 103 at this wavelength and pH 9-10.

9. Determination by reaction with arsenazo 3. This reagent, in the pH range 4-8, forms a blue complex with a composition of 1:1 with lead with two absorption maxima - at 605 and 665 nm.

10. Determination by reaction with diphenylcarbazone. In terms of reaction sensitivity, when extracting the chelate in the presence of KCN, and in terms of selectivity, it approaches dithizone.

11. Indirect method for determining Pb using diphenylcarbazide. The method is based on the precipitation of lead chromate, its dissolution in 5% HC1 and the photometric determination of dichromic acid by reaction with diphenylcarbazide using a filter with a maximum transmission at 536 nm. The method is time-consuming and not very accurate.

12. Determination by reaction with xylenol orange. Xylenol orange (KO) forms a 1:1 complex with lead, the optical density of which reaches its limit at pH 4.5-5.5.

13. Determination by reaction with bromopyrogalpol red (BOD) in the presence of sensitizers. Diphenylguanidinium, benzylthiuronium and tetraphenylphosphonium chlorides are used as sensitizers that increase the color intensity but do not affect the position of the absorption maximum at 630 nm, and cetyltrimethylammonium and cetylpyridinium bromides at pH 5.0.

14. Determination by reaction with glycinthymol blue. The complex with glycinthymol blue (GBL) of composition 1:2 has an absorption maximum at 574 nm and a corresponding molar extinction coefficient of 21300 ± 600.

15. Determination with methylthymol blue is performed under conditions similar to those for the formation of a complex with GTS. In terms of sensitivity, both reactions are close to each other. Light absorption is measured at pH 5.8-6.0 and a wavelength of 600 nm, which corresponds to the position of the absorption maximum. The molar extinction coefficient is 19,500. Interference from many metals is eliminated by masking.

16. Determination by reaction with EDTA. EDTA is used as a titrant in indicator-free and indicator photometric titrations (PT). As in visual titrimetry, reliable FT with EDTA solutions is possible at pH > 3 and titrant concentration of at least 10-5 M.

Luminescent analysis

1. Determination of Pb using organic reagents

A method has been proposed in which the intensity of chemiluminescence emission is measured in the presence of Pb due to the catalytic oxidation of luminol with hydrogen peroxide. The method was used to determine from 0.02 to 2 μg Pb in 1 ml of water with an accuracy of 10%. The analysis lasts 20 minutes and does not require preliminary sample preparation. In addition to Pb, the oxidation reaction of luminol is catalyzed by traces of copper. The method, which is much more complex in its hardware design, is based on the use of the fluorescence quenching effect of fluores-132 derivatives and is valuable in the formation of chelates with lead. More selective in the presence of many geochemical satellites of Pb, although less sensitive, is a fairly simple method based on increasing the fluorescence intensity of the water-blue lumogen in a dioxane-water mixture (1: 1) in the presence of Pb.

2. Methods of low-temperature luminescence in frozen solutions. Freezing the solution is most easily solved in the method for determining lead in HC1, based on photoelectric recording of the green fluorescence of chloride complexes at -70°C.

3. Analysis of the luminescence burst during defrosting of samples. The methods of this group are based on a shift in the luminescence spectra when the analyzed sample is thawed and measurement of the observed increase in radiation intensity. The maximum wavelength of the luminescence spectrum at -196 and -70°C is 385 and 490 nm, respectively.

4. A method is proposed based on measuring the analytical signal at 365 nm in the quasi-line luminescence spectrum of CaO-Pb crystal phosphorus cooled to liquid nitrogen temperature. This is the most sensitive of all luminescent methods: if an activator is applied to the surface of tablets (150 mg CaO, diameter 10 mm, pressing pressure 7-8 MN/m2), then the detection limit on the ISP-51 spectrograph is 0.00002 μg. The method is characterized by good selectivity: a 100-fold excess of Co, Cr(III), Fe (III), Mn(II), Ni, Sb (III) and T1 (I) does not interfere with the determination of Pb. Bi can also be determined simultaneously with Pb.

5. Determination of lead by the luminescence of a chloride complex sorbed on paper. In this method, luminescent analysis is combined with the separation of Pb from interfering elements using a ring bath. The determination is carried out at ordinary temperature.

1.6 Alelectrochemical methods

1. Potentiometric methods. Direct and indirect determination of lead is used - titration with acid-base, complexometric and precipitation reagents.

2. Electrogravimetric methods use the deposition of lead on electrodes, followed by weighing or dissolution.

3. Coulometry and coulometric titration. Electrogenerated sulfhydryl reagents are used as titrants.

4. Volt-amperometry. Classical polarography, which combines rapidity with fairly high sensitivity, is considered one of the most convenient methods for determining Pb in the concentration range of 10-s-10 M. In the vast majority of works, lead is determined by the reduction current of Pb2+ to Pb° on a mercury dropping electrode (DRE), usually occurring reversibly and in the diffusion mode. As a rule, cathodic waves are well expressed, and polarographic maxima are especially easily suppressed by gelatin and Triton X-100.

5. Amperometric titration

In amperometric titration (AT), the equivalence point is determined by the dependence of the current value of the electrochemical transformation of Pb and (or) titrant at a certain value of the electrode potential on the titrant volume. Amperometric titration is more accurate than the conventional polarographic method, does not require mandatory temperature control of the cell, and is less dependent on the characteristics of the capillary and indifferent electrolyte. It should be noted that the AT method has great potential, since analysis is possible using an electrochemical reaction involving both Pb itself and the titrant. Although the total time spent on AT execution is greater, it is fully compensated by the fact that there is no need for calibration. Titration is used with solutions of potassium dichromate, chloranilic acid, 3,5-dimethyldimercapto-thiopyrone, 1,5-6 is (benzylidene)-thio-carbohydrazone, thiosalicylamide.

1.7 FiPhysical methods for lead determination

Lead is determined by atomic emission spectroscopy, atomic fluorescence spectrometry, atomic absorption spectrometry, X-ray methods, radiometric methods, radiochemical and many others.

2 . ExperimentalPart

2.1 MehDefinition code

This work uses the determination of lead in the form of a dithizonate complex.

Figure 1 - structure of dithizone:

The maximum absorption of lead dithizonate complexes is 520 nm. Photometry is used against a solution of dithizone in CCl 4 .

Double ashing of the test sample is carried out - dry and “wet” method.

Double extraction and reaction with auxiliary reagents serve to separate interfering impurities and ions, and increase the stability of the complex.

The method is highly accurate.

2. 2 Etctests and reagents

Spectrophotometer with cuvettes.

Drying cabinet.

Muffle furnace.

Electric stove.

Electronic balance

Drip funnel 100 ml.

Chemical vessels.

A weighed portion of dry plant material 3 pcs. 10 gr.

0.01% solution of dithizone in CCl 4 .

0.02 N HCl solution.

0.1% hydroxylamine solution.

10% solution of yellow blood salt.

10% solution of ammonium citrate.

10% HCl solution.

Ammonia solution.

Soda solution.

Indicators are thymol blue and phenol red.

Standard solutions of lead, with its content from 1,2,3,4,5,6 µg/ml.

2. 3 Etcpreparation of solutions

1. 0.1% hydroxylamine solution.

W=m water/m solution =0.1%. The mass of the solution is 100 g. Then the weight is 0.1 g. Dissolved in 99.9 ml of double-distilled water.

2.10% solution of yellow blood salt. W=m water/m solution =10%. The mass of the solution is 100 g. Then the weight is 10 g. Dissolved in 90 ml of double-distilled water.

3.10% ammonium citrate solution. W=m water/m solution =10%. The mass of the solution is 100 g. Weight - 10 g. Dissolved in 90 ml of double-distilled water.

4.10% HCl solution. Prepared from concentrated HCl:

You need 100 ml of solution with W=10%. d conc HCl = 1.19 g/ml. Therefore, it is necessary to take 26 g of concentrated HCl, V = 26/ 1.19 = 21.84 ml. 21.84 ml of concentrated HCl was diluted to 100 ml with double-distilled water in a 100 ml volumetric flask to the mark.

5. 0.01% solution of dithizone in CCl4. W=m water/m solution =10%. The mass of the solution is 100 g. Then the weight is 0.01 g. Dissolved in 99.9 ml CCl 4.

6. Soda solution. Prepared from dry Na 2 CO 3 .

7. 0.02 N HCl solution. W=m v-va /m r-ra =? Conversion to mass fraction. 1 liter of 0.02 N HCl solution contains 0.02 * 36.5 = 0.73 g of HCl solution. d conc HCl = 1.19 g/ml. Therefore, you need to take 1.92 g of concentrated HCl, volume = 1.61 ml. 1.61 ml of concentrated HCl was diluted to 100 ml with double-distilled water in a 100 ml volumetric flask to the mark.

9. A solution of the thymol blue indicator was prepared from a dry substance by dissolving it in ethyl alcohol.

2. 4 Mehshaking influences

In an alkaline environment containing cyanide, dithizone extracts thallium, bismuth and tin (II) together with lead. Thallium does not interfere with colorimetric determination. Tin and bismuth are removed by extraction in an acidic medium.

The determination does not interfere with silver, mercury, copper, arsenic, antimony, aluminum, chromium, nickel, cobalt and zinc in concentrations not exceeding twelve times the concentration of lead. The interfering influence of some of these elements, if present in fiftyfold concentration, is eliminated by double extraction.

Determination is hampered by manganese, which, when extracted in an alkaline medium, catalytically accelerates the oxidation of dithizone with atmospheric oxygen. This interference is eliminated by adding hydroxylamine hydrochloride to the extracted sample.

Strong oxidizing agents interfere with the determination because they oxidize dithizone. Their reduction with hydroxylamine is included in the determination.

2. 5 Thoseexperimental technique

The plant material was dried in a drying oven in a crushed state. Drying was carried out at a temperature of 100 0 C. After drying to an absolutely dry state, the plant material was thoroughly crushed.

Three 10 g portions of dry material were taken. They were placed in a crucible and placed in a muffle furnace, where they were ashed for 4 hours at a temperature of 450 0 C.

Afterwards, the plant ash was soaked in nitric acid while heating and dried (from here on - the operations are repeated for all samples).

Then the ash was again treated with nitric acid, dried on an electric stove and placed in a muffle furnace for 15 minutes at a temperature of 300 0 C.

Afterwards, the clarified ash was dug in with hydrochloric acid, dried, and dug in again. The samples were then dissolved in 10 ml of 10% of hydrochloric acid.

Next, the solutions were placed in 100 ml dropping funnels. 10 ml of a 10% solution of ammonium citrate was added, then the solution was neutralized with ammonia until the color of thymol blue turned blue.

After this, extraction was carried out. 5 ml of a 0.01% solution of dithizone in CCl 4 was added. The solution in the dropping funnel was shaken vigorously for 5 minutes. The dithizone layer, after being separated from the main solution, was drained separately. The extraction operation was repeated until the initial color of each new portion of dithizone stopped turning red.

The aqueous phase was placed in a dropping funnel. It was neutralized with a soda solution until the color changed from phenol red to orange. Then 2 ml of a 10% yellow blood salt solution, 2 ml of a 10% ammonium citrate solution, and 2 ml of a 1% hydroxylamine solution were added.

Then the solutions were neutralized with a soda solution until the color of the indicator (phenol red) turned crimson.

Next, 10 ml of a 0.01% solution of dithizone in CCl 4 was added, the sample was vigorously shaken for 30 seconds, then the dithizone layer was poured into a cuvette and spectophotometered against a solution of dithizone in CCl 4 at 520 nm.

The following optical densities were obtained:

The calibration graph was constructed under the same conditions; standard solutions of lead concentrations from 1 to 6 μg/ml were used. They were prepared from a lead solution with a concentration of 1 μg/ml.

2.6 ReExperiment resultsenta and statistical processing

Data for constructing a calibration graph

Calibration chart

According to the calibration graph, the concentration of lead in one kilogram of dry plant mass is equal to

1) 0.71 mg/kg

2) 0.71 mg/kg

3) 0.70 mg/kg

What follows from the determination conditions is that the lead concentration in the standards is measured in μg/ml; for the analysis, the lead content was measured in 10 ml, recalculated for one kilogram of dry plant material.

Average mass value: X av = 0.707 g.

Variance =0.000035

Standard deviation: = 0.005787

Youwater

1. Based on a literature review.

Using a literature review, we studied general information about the element, its methods of determination, the most suitable of them is selected according to its accuracy and compliance with those used in everyday practice.

2. Based on the results of the experiment.

The experiment showed that the method can be used to determine low lead contents; the results are highly accurate and repeatable.

3. In accordance with MPC.

List of references used

1. Polyansky N.G. Svinets.-M.: Nauka, 1986. - 357 p. (Analytical chemistry of elements).

2. Vasiliev V.P. Analytical chemistry. At 2 p.m. 2. Physico-chemical methods of analysis: Textbook. For chemical technology Specialist. Vuzov.-M.: Higher. school, 1989. - 384 p.

3. Fundamentals of analytical chemistry. In 2 books. Book 2. Methods chemical analysis: Textbook. For universities/Yu.A. Zolotov, E.N. Dorokhova, V.I. Fadeeva and others. Ed. Yu.A. Zolotova. - 2nd ed., revised. And additional - M.: Higher. school, 2002. - 494 p.

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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. Stir and observe color development. 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 intense of 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:

Barrier - pink-orange (pH=5);
Aquaphor (jug) - pink-orange (pH=5);
Aquaphor (tap) - pink-orange (pH=5);
Unfiltered water is light yellow (pH=6).

Results of determination of iron (III) ions:

Barrier - Barely noticeable yellowish-pink from 0.05 to 0.1;
Aquaphor (jug) - absence less than 0.05;
Aquaphor (faucet) - absence less than 0.05;
Unfiltered water - yellowish-pink from 0.5 to 1.0.

Results of determination of lead (II) ions:

Barrier - no sediment. In 3 drops the water became discolored;
Aquaphor (jug) - no sediment. In 2 drops the water became discolored;
Aquaphor (tap) - no sediment. In 2 drops the water became discolored;
Unfiltered water - no sediment. In 10 drops the water became discolored.

Hardness of the tested water:

Barrier - 7 mEq/l;
Aquaphor (jug) - 5 mEq/l;
Aquaphor (tap) - 4 mEq/l;
Unfiltered water - 9 mEq/l.

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 environmental situation 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 considered 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 water supply 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 rich 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 examined. It turned out that in fact the skeletons of slave owners contain significantly more lead than the bones of slaves. Lead was known 6-7 thousand years BC. e. peoples of Mesopotamia, Egypt and other countries ancient world. It was used to make statues, household items, and writing tablets. Alchemists called lead Saturn and designated it with 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 back in the 1st century. 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 major 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.

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.

Essay

The course work contains: ___ pages, 4 tables, 2 figures, 8 literary sources. The object of research in the course work is food products of complex chemical composition.

The purpose of the work is to determine the lead content in food products and compare it with the MPC.

The research method is atomic absorption.

Sample preparation methods are given. Data on the content of lead compounds in food objects (objects) were analyzed and summarized.

Area of application: analytical and toxicological chemistry, laboratories for standardization and quality of food products produced by light industry, pharmaceutical chemistry.

Keywords: LEAD, ATOMIC ABSORPTION SPECTROSCOPY, ABSORPTION, STANDARD SOLUTION, CALIBRATION GRAPH, CONTENTS, MPC

Introduction

1. Literature review

1.3 Sample preparation

2. Experimental part

conclusions

Introduction

The use of materials containing lead and its compounds has led to the pollution of many environmental objects. Determination of lead in metallurgical products, biological materials, soils, etc. presents difficulties because it is usually accompanied by other divalent metals. To solve such an analytical problem, the atomic absorption method of determination has become widespread due to the availability of equipment, high sensitivity and sufficient accuracy.

Food products can contain not only useful substances, but also quite harmful and dangerous for the human body. Therefore, the main task of analytical chemistry is food quality control.

Namely, this course work uses the atomic absorption method for determining lead in coffee.

1. Literature review

1.1 Chemical properties of lead

In the periodic table D.I. Mendeleev lead is located in group IV, the main subgroup and has atomic weight 207, 19. Lead in its compounds can be in the oxidation state +4, but the most characteristic for it is +2.

In nature, lead occurs in the form of various compounds, the most important of which is the lead luster PbS. Lead prevalence in earth's crust is 0.0016 wt. %.

Lead is a bluish-white heavy metal with a density of 11.344 g/cm 3. It is very soft and can be easily cut with a knife. Lead melting point 327.3 O C. In air, lead quickly becomes covered with a thin layer of oxide, protecting it from further oxidation. In the voltage series, lead comes immediately before hydrogen; its normal potential is - 0.126 V.

Water by itself does not react with lead, but in the presence of air, lead is gradually destroyed by water to form lead hydroxide:

Pb+O 2+ H2 O=2Pb(OH) 2

However, when it comes into contact with hard water, lead becomes covered with a protective film of insoluble salts (mainly lead sulfate and basic lead carbonate), which prevents further action of water and the formation of hydroxide.

Diluted salt and sulfuric acid do not act on lead due to the low solubility of the corresponding lead salts. Lead easily dissolves in nitric acid. Organic acids, especially acetic acid, also dissolve lead in the presence of atmospheric oxygen.

Lead also dissolves in alkalis, forming plumbites.

1.2 Physiological role of lead

The metabolism of lead in humans and animals has been studied very little. Biological role it is also not completely clear. It is known that lead enters the body with food (0.22 mg), water (0.1 mg) and dust (0.08 mg). Typically, the lead content in a man's body is about 30 µg%, and in women it is about 25.5 µg%.

From a physiological point of view, lead and almost all its compounds are toxic to humans and animals. Lead, even in very small doses, accumulates in the human body, and its toxic effect gradually increases. When lead poisoning occurs, gray spots appear on the gums and functions are impaired. nervous system, pain is felt in the internal organs. Acute poisoning leads to severe damage to the esophagus. For people who work with lead, its alloys or compounds (for example, printing workers), lead poisoning is an occupational disease. The dangerous dose for an adult lies in the range of 30-60 g Pb (CH3COO) 2 * 3H 2ABOUT .

1.3 Sample preparation

The selection and preparation of laboratory samples is carried out in accordance with the normative and technical documentation for this type of product. Two parallel samples are taken from the combined laboratory sample.

Products with a high sugar content (confectionery, jams, compotes) are treated with sulfuric acid (1: 9) at the rate of 5 cm 3 acid per 1 g of dry matter and incubated for 2 days.

Products with a fat content of 20-60% (cheese, oil seeds) are treated with nitric acid (1:

) based on 1.5 cm 3 acid per 10 g of dry matter and incubated for 15 minutes.

Samples are dried in an oven at 150 O C (if there are no aggressive acid fumes) on an electric stove with low heat. To speed up sample drying, simultaneous irradiation of samples with an IR lamp can be used.

Dried samples are carefully charred on an electric stove or gas burner until the emission of smoke stops, preventing ignition and emissions.

Place the crucibles in a cold electric furnace and increase its temperature by 50 O Every half hour, bring the oven temperature to 450 O C. At this temperature, mineralization is continued until gray ash is obtained.

The ash cooled to room temperature is moistened dropwise with nitric acid (1:

) based on 0.5-1 cm 3 weighed acids, evaporated in a water bath and dried on an electric stove with low heat. Place the ash in an electric furnace and bring its temperature to 300 O C and kept for 0.5 hours. This cycle (acid treatment, drying, ashing) can be repeated several times.

Mineralization is considered complete when the ash becomes white or slightly colored without charred particles.

Wet mineralization. The method is based on complete decomposition organic matter samples when heated in a mixture of concentrated nitric acid, sulfuric acid and hydrogen peroxide and is intended for all types of food products, butter and animal fats.

A weighed portion of liquid and puree products is added to a flat-bottomed flask, wetting the walls of a 10-15 cm glass 3bidistilled water. You can take the sample directly into a flat-bottomed flask.

A sample of solid and pasty products is taken onto an ash-free filter, wrapped in it and placed with a glass rod on the bottom of a flat-bottomed flask.

Drink samples are taken with a pipette, transferred to a Kjeldahl flask and evaporated on an electric stove to 10-15 cm3 .

A weighed portion of dry products (gelatin, egg powder) is placed in a flask and 15 cm is added 3bidistilled water, stir. Gelatin is left for 1 hour to swell.

Sample mineralizationMineralization of samples of raw materials and food products except vegetable oils, margarine, edible fats:

Nitric acid is added to the flask to calculate 10 cm 3for every 5 g of product and incubate for at least 15 minutes, then add 2-3 clean glass beads, close with a pear-shaped stopper and heat on an electric stove, first weakly, then more strongly, evaporating the contents of the flask to a volume of 5 cm3 .

Cool the flask, add 10 cm 3nitric acid, evaporate to 5 cm 3. This cycle is repeated 2-4 times until the brown fumes stop.

Add 10 cm to the flask 3nitric acid, 2 cm 3sulfuric acid and 2 cm 3hydrogen peroxide for every 5 g of product (mineralization of dairy products is carried out without adding sulfuric acid).

To remove residual acids, add 10 cm 3double-distilled water, heat until white vapor appears and then boil for another 10 minutes. Cool. Adding water and heating is repeated 2 more times.

If a precipitate forms, add 10 cm 3bidistilled water, 2 cm 3sulfuric acid, 5 cm 3hydrochloric acid and boil until the precipitate dissolves, adding evaporating water. After dissolving the precipitate, the solution is evaporated in a water bath to wet salts.

Mineralization of vegetable oils, margarine, edible fats:

lead food chemistry

The flask with the sample is heated on an electric stove for 7-8 hours until a viscous mass is formed, cooled, and 25 cm 3nitric acid and carefully heat again, avoiding violent foaming. After foaming stops, add 25 cm 3nitric acid and 12 cm 3hydrogen peroxide and heat until a colorless liquid is obtained. If the liquid darkens, periodically add 5 cm 3nitric acid, continuing heating until mineralization is complete. Mineralization is considered complete if the solution remains colorless after cooling.

Acid extraction. The method is based on the extraction of toxic elements with dilute (1:

) by volume with hydrochloric acid or diluted (1: 2) by volume with nitric acid and is intended for vegetable and butter oils, margarine, edible fats and cheeses.

Extraction is carried out in a heat-resistant sample of the product. Add 40 cm into the flask using a cylinder. 3solution of hydrochloric acid in double-distilled water (1:

) by volume and the same amount of nitric acid (1: 2). Several glass beads are added to the flask, a refrigerator is inserted into it, placed on an electric stove, and boiled for 1.5 hours from the moment of boiling. Then the contents of the flask are slowly cooled to room temperature without removing the refrigerator.

The flask with the extraction mixture of butter, fats or margarine with acid is placed in a cold water bath to solidify the fat. The hardened fat is pierced with a glass rod, the liquid is filtered through a filter moistened with the acid used for extraction into a quartz or porcelain bowl. The fat remaining in the flask is melted in a water bath, add 10 cm 3acids, shake, cool, after cooling the fat is calcined and the liquid is poured through the same filter into the same bowl, then washed 5-7 cm 3bidistilled water.

The extraction mixture of vegetable oil and acid is transferred to a separatory funnel. The flask is rinsed 10 cm 3acid, which is poured into the same funnel. After phase separation, the lower aqueous layer is poured through an acid-soaked filter into a quartz or porcelain bowl, the filter is washed 5-7 cm 3bidistilled water.

The extraction mixture of cheese and acid is filtered through an acid-soaked filter into a quartz or porcelain bowl. The flask is rinsed 10 cm 3acid, which is filtered through the same filter, then the filter is washed 5-7 cm 3bidistilled water.

The filtered extract is carefully evaporated and charred on an electric stove, and then ashed in an electric oven.

1.4 Lead determination methods

1.4.1 Concentration of trace amounts of lead ion using nanometer particles of titanium dioxide (anatase) for the purpose of their subsequent determination by inductively coupled plasma atomic emission spectrometry with electrothermal evaporation of the sample

Inductively coupled plasma atomic emission spectrometry ( ISP-AES) -a widely used and very promising method of elemental analysis. However, it has some disadvantages, including relatively low detection sensitivity, low sputtering efficiency, spectral interference and other matrix effects. Therefore, ICP-AES does not always meet the requirements modern science and technology. The combination of ICP-AES with electrothermal evaporation of the sample (ETI-ICP-AES) significantly expands the capabilities of the method. By optimizing the pyrolysis and evaporation temperatures, analyte elements can be evaporated sequentially, separating them from the sample matrix. This method has the advantages of high sample introduction efficiency, the ability to analyze small sample quantities, low absolute detection limits, and the ability to directly analyze solid samples.

Analysis tools and conditions.An ICP generator with a power of 2 kW and a frequency of 27 ± 3 MHz was used; ISP burner; graphite furnace WF-1A; diffraction spectrometer RO5-2 with diffraction grating 1300 lines/mm with linear dispersion 0.8 nm/mm; pH meter Mettle Toledo 320-S; sedimentation centrifuge model 800.

Standard solutions and reagents.Stock standard solutions with a concentration of 1 mg/ml are prepared by dissolving the corresponding oxides (spectroscopic purity) in diluted HC1, followed by dilution with water to a given volume. A suspension of polytetrafluoroethylene was added to each standard solution to a concentration of 6% w/v.

We used Triton X-100 reagent grade (USA). The remaining reagents used were of spectroscopic grade; double distilled water. Titanium dioxide nanoparticles with a diameter of less than 30 nm.

Method of analysis.The required volume of solution containing metal ions is placed in a 10 ml graduated test tube and the pH is adjusted to 8.0 using 0.1 M HC1 and an aqueous solution of NH 3. Then 20 mg of titanium dioxide nanoparticles are added to the test tube. Shake the test tube for 10 minutes. (preliminary experiments showed that this is sufficient to achieve adsorption equilibrium). The tube is left for 30 minutes, then the liquid phase is removed using a centrifuge. After washing the precipitate with water, 0.1 ml of a 60% polytetrafluoroethylene suspension, 0.5 ml of a 0.1% agar solution, 0.1 ml are added to it. Triton X-100 and diluted with water to 2.0 ml. The mixture is then dispersed using an ultrasonic vibrator for 20 minutes to achieve homogeneity of the suspension before it is introduced into the evaporator. 20 μl of the suspension is added to the graphite furnace after heating and stabilization of the ICP. After drying, pyrolysis and evaporation, the sample vapor is transferred to the ICP by a current of carrier gas (argon); atomic emission signals are recorded. Before each sample injection, the graphite furnace is heated to 2700°C to clean it.

Application of the method.The developed method is used to determine Pb 2+in samples of natural lake water and river water. Water samples were filtered through a 0.45 µm membrane filter immediately after sampling and then analyzed.

1.4.2 Determination of lead combining real-time concentration followed by reversed-phase HPLC

Instruments and reagents. A diagram of the HPLC system with real-time concentration ("on-line") is shown in Fig. 1.1 The system consists of a Waters 2690 Alliance pump (in diagram 2), a Waters 515 pump (1), a Waters 996 photodiode array detector (7) , six-way switch tap (4), large volume injection device (holds up to 5.0 ml of sample) (3) and columns (5,6). The concentrating column was Waters Xterra™ RP 18(5 µm, 20 x 3.9 mm), Waters Xterra™ RP analytical column 18(5 µm, 150 x 3.9 mm). pH was determined with a Beckman F-200 pH meter, and optical density was measured with a Shimadzu UV-2401 spectrophotometer.

Fig 1.1Schematic of a real-time concentration system using a switch tap

All solutions were prepared using ultrapure water obtained using the Milli-Q50 Sp Reagent Water System (Millipore Corporation). A standard solution of lead (P) with a concentration of 1.0 mg/ml, working solutions with an ion concentration of 0.2 μg/ml are prepared by diluting standard ones. Use tetrahydrofuran (THF) for HPLC (Fisher Corporation), pyrrolidine-acetic acid buffer solution with a concentration of 0.05 mol/L. Before use, glassware was soaked for a long time in a 5% nitric acid solution and washed with clean water.

Experimental technique. The required volume of a standard solution or sample is added to a 25 cm volumetric flask. 3, add 6 ml of solution T 4CPP with a concentration of 1 x10 -4mol/l in THF and 4 ml of pyrrolidine-acetic acid buffer solution with a concentration of 1 x10 -4mol/l and pH 10, dilute to the mark with water and mix thoroughly. The mixture is heated in a boiling water bath for 10 minutes. After cooling, dilute to the THF mark for subsequent analysis. The solution (5.0 ml) is introduced into the dispenser and sent to a concentrating column using mobile phase A at a rate of 2 cm3/min. Upon completion of concentration by eliminating the six-way valve, metal chelates with T 4CPPs adsorbed at the top of the concentrating column are eluted with a flow of mobile phases A and B at a rate of 1 ml/min in the opposite direction and sent to the analytical column. The three-dimensional chromatogram was recorded in the wavelength range of maximum absorption 465 nm using a detector with a photodiode array.

1.4.3 Stripping voltammetric determination of lead using a glassy carbon electrode system

Instruments and reagents.For the studies, we used an electrode system, which was an assembly of three identical glassy carbon (GC) electrodes (indicator, auxiliary, comparison) pressed into a common tetrafluoroethylene housing. The length of each electrode protruding from the housing is 5 mm. The surface of one of them, chosen as an indicator, was electrochemically treated with an asymmetric current at densities in the range of 0.1-5 kA/m 2recommended for metals. The optimal surface renewal time was found experimentally and was 10-20 s. The indicator electrode served as the anode, and the stainless steel electrode served as the cathode. We used 0.1 M aqueous solutions of acids, salts, alkalis, as well as 0.1 M solutions of alkalis or salts in a mixture of organic solvents with water in a ratio of 1: 19 by volume. The condition of the treated surface was observed visually using a Neophot 21 microscope with an increase of about 3000.

Method of analysis.After processing, the electrode assembly was used to determine 3*10 -6M lead (II) by stripping voltammetry against a background of 1*10 -3M HNO 3. After electrolysis at – 1.5 V for 3 min with stirring with a magnetic stirrer, a voltammogram was recorded on a PA-2 polarograph. The potential of the lead anodic peak remained constant and amounted to - 0.7 V. The linear potential scan rate was 20 mV/s, the scan amplitude was 1.5 V, the current sensitivity was 2 * 10-7 A/mm.

Aqueous solutions of LiNO 3, NaNO 3, KNO 3as a processing electrolyte, they allow one to obtain stable heights already in the second measurement with satisfactory reproducibility (2.0, 2.9 and 5.4%, respectively). The greatest sensitivity of readings is achieved when using an electrolyte having a smaller cation.

1.4.4 Atomic absorption determination of lead by dosing suspensions of carbonized samples using Pd-containing activated carbon as a modifier

Analytical measurements were carried out on a SpectrAA-800 atomic absorption spectrometer with a GTA-100 electrothermal atomizer and a PSD-97 autosampler (Varian, Australia). We used graphite tubes with pyrolytic coating and an integrated platform (Varian, Germany), hollow cathode lamps for lead (Hitachi, Japan) and cadmium (Varian, Australia). Integral absorption measurements with correction for nonselective light absorption (deuterium system) were carried out at a spectral slit width of 0.5 nm and a wavelength of 283.3 nm. Argon "highest grade" served as a shielding gas. The temperature program for the atomizer operation is given in Table 1.1

Table 1.1 Temperature program for the operation of the electrothermal atomizer GTA-100

StageTemperature,°CDrying 190Drying 2120Pyrolysis1300Cooling50Atomization23OOCleaning2500

Palladium-containing compositions based on activated carbon and carbonized hazelnut shells were studied as modifiers for the atomic absorption determination of Pb in a graphite furnace. The metal content in them was 0.5-4%. To assess the changes occurring with the components of the synthesized modifiers under reducing conditions implemented during the analysis, the materials were treated with hydrogen at room temperature.

A solution with a known concentration of Pb was prepared by diluting GSO No. 7778-2000 and No. 7773-2000 with 3% HNO 3. The concentration range of working standard solutions of the element for constructing calibration dependencies was 5.0-100 ng/ml. Deionized water was used to prepare solutions .

When constructing pyrolysis and atomization curves, we used both a standard solution of the element and a carbonized “Standard sample of the composition of ground wheat grain ZPM-01”. In the first case, 1.5 ml of a standard solution of the element (50 ng/ml Pd in 5% HNO 3) and 10-12 mg of palladium-containing activated carbon; the suspension was homogenized and dosed into a graphite furnace. In the second, the same amount of modifier was added to the prepared suspension of carbonized sample (5-10 mg of sample in 1-2 ml of 5% HNO3 ).

1.4.5 Photometric determination and concentration of lead

Lead acetate of analytical grade was used in this work. The compounds (Fig. 1, which are dibasic acids) were obtained by azo coupling of a solution of 2-hydroxy-4 (5) - nitrophenyldiazonium chloride and the corresponding hydrazone. Solutions of formazans in ethanol were prepared by precise weighing.

The optical density of solutions was measured on a Beckman UV-5270 spectrophotometer in quartz cuvettes (l = 1 cm). The concentration of hydrogen ions was measured using an I-120M ion meter.

The reagents react with lead ions, forming colored compounds. The bathochromic effect during complex formation is 175 - 270 nm. Complexation is influenced by the nature of the solvent and the structure of the reagents (Fig. 1).

The optimal conditions for the determination of lead are a water-ethanol medium (1:

) and pH 5.5-6.0, created by an ammonium acetate buffer solution. The detection limit for lead is 0.16 µg/ml. Analysis duration 5 min.

The most interesting is the use of formazan as a reagent for the concentration and subsequent photometric determination of lead. The essence of the concentration and subsequent determination of lead (II) using formazan is that the lead complex is extracted from a water-ethanol solution in the presence of Ni, Zn, Hg, Co, Cd, Cr, Fe ions with a chloroform solution of formazan.

For comparison, we used the method for determining lead with sulfarsazen (GOST, MU issue 15, No. 2013-79). The results of the analysis of model solutions using two methods are given in Table 1.2 Comparison of variances using the F-criterion showed that Fexp< Fтеор (R= 0.95; f 1=f 2= 5); This means that the variances are homogeneous.

Table 1.2 results of determination of lead in model solutions (n=6; P=0.95)

Introduced, µg/mlFoundFoundFexpF theorsulfarsazen, µg/mlS r formazan, µg/mlS r 4.14 2.10 3.994.04 ±0.28 2.06±0.29 3.92 ±0.17 0.29 3.92 ±0.172.8 5.5 1.74.14 ±0.07 2.10 ±0.08 3.99 ± 0.072.1 *10 -2 2.5*10-2 2.1*10-23.97 3.57 3.374.53

2. Experimental part

Measuring instruments, reagents and materials:

When performing this method, the following measuring instruments, devices, reagents and materials are used:

· Atomic absorption spectrometer

· Spectral lamp with hollow cathode

· Compressor for supplying compressed air

· Gearbox - according to GOST 2405

· Laboratory beakers, capacity 25-50 cm3 - according to GOST 25336

· Measuring flasks of the second accuracy class with a capacity of 25-100 cm3

· Laboratory funnels according to GOST 25336

· Distilled water

· Concentrated nitric acid, x. h., GOST 4461-77

· Standard lead solution (c = 10-1 g/l)

Determination conditions:

§ Wavelength when determining lead? =283.3 nm

§ Monochromator slit width 0.1 nm

§ Lamp current 10 mA

Method of measurement:

Atomic absorption spectroscopy is based on the absorption of radiation in the optical range by unexcited free lead atoms formed when the analyzed sample is introduced into a flame at a wavelength ? =283.3 nm.

Safety requirements:

When performing all operations, it is necessary to strictly observe the safety rules when working in a chemical laboratory, corresponding to GOST 126-77 "Basic safety rules in a chemical laboratory", including rules for safe work with electrical devices with voltages up to 1000 volts.

Preparation of lead calibration solutions:

Solutions are prepared using a standard lead solution with a concentration

c= 10-1 g/l.

To construct a calibration curve, use solutions of the following concentrations:

*10-4, 3*10-4, 5*10-4, 7*10-4, 10*10-4g/l

Standard solution with a volume of 10 cm 3add to a 100 ml flask and fill to the mark with distilled water. In 5 volumetric flasks with a capacity of 100 ml add 1, 3, 5, 7, 10 ml of intermediate solution (solution of concentration 10 -2g/l). Make up to the mark with distilled water. Construct a gradation graph in coordinates A, y. e from s, g/l

Table 2.1 Measurement results

concentration, g/lSignal, u. e. 0.000130.0003150.0005280.0007390.001057

Sample preparation:

I take a sample of coffee weighing 1.9975 g.

I add it to a 100 ml glass.

I dissolve the sample in 20 ml of concentrated nitric acid.

I evaporate the contents of the glass in a water bath to half the original volume, stirring occasionally.

The solution in the beaker after evaporation is cloudy, therefore, using a laboratory funnel and a paper filter, I filter the contents of the beaker into a 25 ml beaker.

I add the filtered solution into a 25 ml flask and bring it to the mark with distilled water.

I thoroughly mix the contents of the flask.

I add part of the solution from the flask into a pipette, which serves as a sample to determine the lead content.

To determine an unknown concentration, the solution is introduced into the atomizer and after 10-15 seconds the readings of the device are recorded. The average readings of the device are plotted on the ordinate axis of the calibration graph, and the corresponding concentration value, сх g/l, is found on the abscissa axis

To calculate the concentration in the sample, I use the calculation formula:

С =0.025*Сх*10-4*1000/ Мnav (kg)

Table 2.2 Measurement results

ProbaSignal, u. e. AverageC X , g/l 123 coffee15141514,666672.9*10 -4cheese00000apples juice00000grape juice00000cream3222.333337.8*10 -5water00000shampoo00000

Based on the tabular data, I calculate the concentration of lead in the samples:

Sample MPC, mg/kg coffee 10 cream

C (Pb in coffee sample) = 3.6 mg/kg

C (Pb in cream sample) = 0.98 mg/kg

conclusions

The work describes methods for determining lead using various physical and chemical methods.

Sample preparation methods for a number of food objects are presented.

Based on literature data, the most convenient and optimal method for determining lead in various food products and natural objects was selected.

The method used is characterized by high sensitivity and accuracy, along with the absence of a response to the presence of other elements, which allows one to obtain true values of the content of the desired element with a high degree of reliability.

The chosen method also makes it possible to conduct research without any particular difficulties in sample preparation and does not require masking of other elements. In addition, the method allows you to determine the content of other elements in the test sample.

Based on the experimental part, we can conclude that the lead content in Black Card coffee does not exceed the maximum permissible concentration, therefore the product is suitable for sale.

List of used literature

1. Glinka N.I. General chemistry. - M.: Nauka, 1978. - 403 p.

Zolotov Yu.A. Fundamentals of analytical chemistry. - M.: Higher. school; 2002. - 494 p.

Remy G. Course general chemistry. - M: Ed. foreign lit., 1963. - 587 p.

GOST No. 30178 - 96

Yiping Hang. // Journal. analyte khim., 2003, T.58, No. 11, p.1172

Liang Wang. // Journal. analyte khim., 2003, T.58, No. 11, p.1177

Nevostruev V.A. // Journal. analyte khim., 2000, T.55, No. 1, p.79

Burilin M.Yu. // Journal. analyte khim., 2004, T.61, No. 1, p.43

Maslakova T.I. // Journal. analyte khim., 1997, T.52, No. 9, p.931

Bashurova Maria

This work examines one of the main environmental problems of our time: environmental pollution with one of the heavy metals - lead. Behind recent years Poisoning with compounds of this particular metal is most often recorded.

Here, for the first time, the amount of lead compounds emitted by road transport was calculated for the village of Novoorlovsk. As a result of qualitative reactions, lead compounds were found in environment Novoorlovsk village.

The main sources of pollution with lead compounds in the village of Novoorlovsk were also identified.

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Scientific and practical conference “Step into the future”

Content Study

lead compounds

In the environment of Novoorlovsk

Completed by: Maria Viktorovna Bashurova

10th grade student at the Novoorlovsk Secondary Municipal Educational Institution

comprehensive school".

Head: Gordeeva Valentina Sergeevna

Chemistry teacher, Municipal Educational Institution "Novoorlovskaya Secondary"

comprehensive school".

Russian Federation

Transbaikal region, Aginsky district, Novoorlovsk

2010

Introduction

1.1 Characteristics and use of lead and its compounds.

1.2 Sources of contamination with lead compounds.

Chapter 2. Study of the content of lead compounds in the environment of Novoorlovsk.

2.1. Research methods.

2.3. Conclusions from the research results.

Conclusion.

Bibliographic list.

Applications.

Bashurova Maria

Introduction.

The role of metals in the development and establishment of the technical culture of mankind is exceptionally great. The historically established names “Bronze Age” and “Iron Age” indicate the strong influence of metals and their alloys on all areas of production development. And in our daily practice we come across metals every minute. And we ourselves have metals. They are used to carry out various processes in the body. But metals are not always necessary. Many of them are even dangerous for the body. For example, some metals are extremely toxic to vertebrates even in small doses (mercury, lead, cadmium, thallium), others cause toxic effects in large doses, although they are trace elements (for example, copper, zinc). In invertebrate animals that have hard integuments, lead is most concentrated in them. In vertebrates, lead accumulates to the greatest extent in bone tissue, in fish - in gonads, in birds - in feathers, in mammals - in the brain and liver.

Lead is a metal that, upon contact with the skin and when ingested into the body, causes the largest number of severe diseases, therefore, in terms of the degree of impact on living organisms, lead is classified as a highly hazardous substance along with arsenic, cadmium, mercury, selenium, zinc, fluorine and benzaprene (GOST 3778-98).

Cars with lead batteries have a huge impact on lead pollution. Exhaust gases are the most important source of lead. An increase in lead in the soil usually leads to its accumulation by plants. Many data show a sharp increase in lead levels in plants growing along the edges of highways. Water pollution with lead is caused by industrial wastewater containing toxic amounts of lead salts, as well as lead pipes. Toxic substances contained in waters are very dangerous for humans, as they actively accumulate in food chains.

According to the analytical agency "Avtostat" in Russia in 2009. there are approximately 41.2 million vehicles. The composition of the vehicle fleet by type of fuel used is as follows: the number of vehicles using gas as fuel does not exceed 2%. The rest of the cars use diesel fuel – 37% or “leaded” gasoline – 61%.

One of the important problems of any region is contamination of soil, water, and air with heavy metals.

When conducting this study we put forward hypothesis that lead compounds are present in the environment of Novoorlovsk.

An object research – pollution of the environment with lead compounds.

Item research – highway and cars passing along it; the soil; snow; plants.

Purpose of the study:study the content of lead compounds emitted into the air; accumulated in soil, plants, snow.

To achieve this goal, we decided on the following: tasks:

1. Study scientific literature and Internet sites regarding the stated purpose of the research.

2. Conduct qualitative analysis samples of soil, snow and plants for the content of lead compounds.

3. Find out the level of pollution of the environment in a given area with lead compounds.

4. Determine the amount of lead compounds emitted by vehicles.

5. Determine the main sources of pollution with lead compounds in this area.

Scientific novelty . As a result of the work, a qualitative analysis of soil, snow and plant samples taken from the environment of the village of Novoorlovsk was carried out for the content of lead compounds. The amount of lead compounds emitted by motor vehicles has been determined. The main sources of pollution with lead compounds in this area have been identified.
Practical significance of the work.Methods for detecting the content of lead compounds in soil, snow, and plants that can be used have been studied. It has been established that lead compounds are found near the main sources of pollution. It was determined during the research that the main sources of pollution with lead compounds are the highway, the Central Boiler House, and JSC Novoorlovsky Mining and Processing Plant.

“Study of the content of lead compounds in the environment of the village of Novoorlovsk”

Bashurova Maria

Russian Federation, Trans-Baikal Territory, Aginsky district, Novoorlovsk

Municipal educational institution "Novoorlovsk secondary school", 10th grade

Chapter 1. Environmental pollution with lead compounds.

1.1. Characteristics and use of lead and its compounds.

Lead - Pb (Plumbum), serial number 82, atomic weight 207.21. This bluish-gray metal has been familiar since time immemorial. The origin of the name “lead” - from the word “wine” - is associated with the use of this metal in the manufacture of vessels for storing wine. A number of experts believe that lead played a decisive role in the fall of the Roman Empire. In ancient times, water flowed from lead-lined roofs through lead gutters into lead-lined barrels. Lead cauldrons were used to make wine. Most ointments, cosmetics and paints contained lead. All this may have led to a decrease in the birth rate and the emergence of mental disorders among the aristocrats.

He is malleable and soft. Even a fingernail leaves a mark on it. Lead melts at a temperature of 327.4 degrees. In air it quickly becomes covered with a layer of oxide. Nowadays, lead is experiencing a “second youth”. Its main consumers are the cable and battery industries, where it is used to make shells and plates. It is used to make tower casings, refrigerator coils and other equipment at sulfuric acid plants. It is indispensable in the manufacture of bearings (babbitt), printing alloy (garth) and some types of glass. Of the lead compounds, lead nitrate Pb(NO) is of greatest practical importance 3 ) 2 , which is used in pyrotechnics - in the manufacture of lighting, incendiary, signal and smoke compositions; Lead dihydroxycarbonate – Pb 3 (OH) 2 (CO 3 ) 2 – used for the preparation of high-quality paint – white lead. True, it has a small flaw: under the influence of hydrogen sulfide, it gradually fades. This is why ancient oil paintings become so dark. Red lead (Pb) is produced in large quantities 3 O 4 ) is a bright red substance from which ordinary oil paint is obtained. Lead pigment lead chromate PbCrO is also widely used for the preparation of paints. 4 (“yellow crown”). The starting product for the preparation of lead compounds is lead acetate Pb 3 (CH 3 COO) 2 . Although its compound is poisonous, its 2% solution is used in medicine for lotions on inflamed body surfaces, as it has astringent and analgesic properties. Alkylated compounds have the most highly toxic properties, in particular tetraethyl lead (C 2 N 5 ) 4 Pb and tetramethyl lead (CH 3 ) 4 Pb is a volatile, toxic liquid substance. Tetraethyl lead (TEL) is an antiknock agent for motor fuel, which is why it is added to gasoline.

1.2. Sources of contamination with lead compounds.

Lead gets into water in various ways. In lead pipes and other places where contact of this metal with water and atmospheric oxygen is possible, oxidation processes occur: 2Pb + O 2 +2H 2 O→2Pb(OH) 2.

In alkalized water, lead can accumulate in significant concentrations, forming plumbites: Pb(OH) 2 +2OHֿ→PbO 2 ²ֿ+2H 2 O.

If there is CO in the water 2 , then this leads to the formation of fairly highly soluble lead bicarbonate: 2Pb+O 2 →2PbO, PbO+CO 2 →Pb CO 3, PbCO 3 +H 2 O+CO 2 →Pb(HCO 3) 2.

Lead can also get into water from soils contaminated with it, as well as through direct waste discharges into rivers and seas. There is a problem of contamination of drinking water in areas where smelters are located or where industrial waste with high lead content is stored.

The highest concentrations of lead are found in soil along highways, and also where metallurgical plants or factories producing lead-containing batteries or glass are located.

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.

Most lead enters the human body through food. The highest levels of lead are found in canned food in tin containers, fresh and frozen fish, wheat bran, gelatin, shellfish and crustaceans. High levels of lead are found in root vegetables and other plant products grown on lands near industrial areas and along roads. Drinking water, atmospheric air, smoking are also sources of lead compounds entering the human body.

1.3. Consequences of lead compounds entering the human body.

In 1924 in the USA, when the production of gasoline required large quantities of thermal power plants, accidents began at the factories where it was synthesized. There were 138 poisonings recorded, of which 13 were fatal. This was the first recorded lead poisoning.

Like radiation, lead is a cumulative poison. Once in the body, it accumulates in the bones, liver and kidneys. Obvious symptoms of lead poisoning are: severe weakness, abdominal cramps and paralysis. The constant presence of lead in the blood is asymptomatic, but also dangerous. It affects the formation of hemoglobin and causes anemia. Mental disorders may occur.

Currently, lead ranks first among the causes of industrial poisoning. Lead contamination of atmospheric air, soil and water in the vicinity of such industries, as well as near major highways, poses a threat of lead exposure to the population living in these areas, and especially children, who are more sensitive to the effects of heavy metals.

Lead poisoning (saturnism) is an example of the most common environmental disease. In most cases, we are talking about the absorption of small doses and their accumulation in the body until its concentration reaches the critical level necessary for toxic manifestations.
The target organs for lead poisoning are the hematopoietic and nervous systems, and the kidneys. Saturnism causes less significant damage to the gastrointestinal tract. One of the main signs of the disease is anemia. At the level of the nervous system, damage to the brain and peripheral nerves is noted. Lead toxicity can be largely prevented, especially in children. Laws prohibit the use of lead-based paints, as well as the presence of lead in them. Compliance with these laws can at least partially solve the problem of these “silent epidemics.” The following classification of lead poisoning, approved by the Ministry of Health of the Russian Federation, is generally accepted:

1. Carriage of lead (in the presence of lead in the urine and the absence of symptoms of poisoning).

2. Mild lead poisoning.

3. Lead poisoning of moderate severity: a) anemia (hemoglobin below 60% - up to 50%); b) mildly expressed lead colic; c) toxic hepatitis.

4. Severe lead poisoning: a) anemia (hemoglobin below 50%); b) lead colic (severe form); c) lead paralysis.

In the treatment of lead poisoning, drugs such as tetacin and pentacin are used. (Appendix 1) Preventive measures are also necessary. (Appendix 2)

Chapter 2. Study of the content of lead compounds in the environment of Novoorlovsk

2.1. Research methods.

To calculate the amount of harmful emissions from motor vehicles in 1 hourwe used the methodology approved by order of the State Committee for Ecology of Russia No. 66 of February 16, 1999.

On a highway, determine a section of road 100 m long.

Calculate the total distance (S) covered by all cars in 1 hour: S = N*100m.
Taking measurements of emissions from cars per 1 km, calculate how many emissions of lead compounds were produced by cars in 1 hour.
Calculate the approximate amount of lead compounds emitted per 1 hour along the total distance traveled.

To determine the content of lead compounds on the surface of the earth (in snow)We used a technique from a school workshop.

To take a sample, you will need containers with a capacity of at least 250 ml.
The container is immersed in the snow with an open end, trying to reach its lower layer.
The sample is removed and taken to the laboratory for melting.
From each sample, 100 ml of liquid is poured and filtered.
1 ml of melt water from each sample is poured into test tubes and 1 ml of KI solution and 1 ml of 6% HNO are added 3 .
Changes in the test tubes are determined.

To determine the content of lead compounds in soilWe used a technique from a school workshop:

Soil samples are taken.
The soil is dried for 5 days.
From each sample, 10 mg portions are taken and placed in test tubes.
Add 10 ml of distilled water to each test tube.
Mix the contents of the tubes for 10 minutes and leave for a day.

6. After 24 hours, add 1 ml of KI and HNO to the test tubes 3 and note the changes.

To determine the content of lead compounds in plantsWe used a technique from a school workshop:

50 pieces of leaves or 50 g of grass are selected.
The plant material is dried and crushed.
The plant mass is placed in test tubes, filled with 20 ml of distilled water and left for a day.

4. After 24 hours, 1 ml of KI and HNO is added 3

5. Mark changes.

2.2. Research results.

The research was carried out in the summer and autumn of 2010.

To calculate the amount of harmful emissions from motor vehicles in 1 hour, a highway passing in the center of the village of Novoorlovsk was selected. As a result of these calculations, we found that 0.644 g of lead compounds are released into the air in 1 hour (Appendix 3).

To determine the content of lead compounds in the environment, we took five samples each on the soil surface (in snow), in soil, in plants in certain areas: 1. Road near the school 2. Central boiler house 3. JSC Novoorlovsky GOK 4. Forest 5 The road along the dacha cooperative. We assessed the level of contamination with lead compounds by the degree of color of the sediment: intense yellow - strong level of contamination; yellowish – medium level; no yellow precipitate – low level.

In the course of studying the content of lead compounds on the soil surface (in snow), it was found that on the side of the road near the school, the Central Boiler House and JSC Novoorlovsky Mining and Processing Plant the most high level lead compounds. This can be seen from the bright yellow sediment that was obtained during the experiment and was a qualitative indicator of lead content. (Appendix 4)

When studying the content of lead compounds in the soil, it turned out that there was a high level of contamination with lead compounds on the side of the road near the school and JSC Novoorlovsky Mining and Processing Plant. (Appendix 5)

Analysis of plant mass showed that plants growing near the Central Boiler House, JSC Novoorlovsky GOK and the road along the dacha cooperative accumulate the largest amount of lead compounds in their tissues. (Appendix 6)

We obtained the lowest level of contamination of the soil surface (snow), soil and plants with lead compounds in samples taken in the forest.

All our results were communicated to the population in the form of bulletins and leaflets about the dangers of pollution with lead compounds. (Appendix 7.8)

2.3. Conclusions.

Experimental data confirmed that the source of lead compounds in our village is the central highway, as well as the Novoorlovsky GOK CJSC and the boiler house.
Lead compounds have been found on the soil surface (snow), in soil and in plants.

3. As a result of calculating the amount of harmful emissions from motor vehicles, we found that 0.644 g of lead compounds are released into the air in 1 hour.

4. Lead compounds are the cause of many serious diseases in humans.

“Study of the content of lead compounds in the environment of the village of Novoorlovsk”

Bashurova Maria

Russian Federation, Trans-Baikal Territory, Aginsky district, Novoorlovsk

Municipal educational institution "Novoorlovsk secondary school", 10th grade

Conclusion.

This work shows that the highway and cars passing along it can become a rather strong source of heavy metals in the environment. Lead from gasoline enters the exhaust gases and then into the atmosphere. The level of pollution will also depend on the traffic load of the road. Since the soil and plants near the road are heavily contaminated with lead, it is impossible to use the land for growing agricultural products and grazing livestock, and the plants cannot be used to feed farm animals.

As a result of the work, a qualitative analysis of soil, snow and plant samples taken from the environment of the village of Novoorlovsk was carried out for the content of lead compounds. The amount of lead compounds emitted by motor vehicles has been determined.

Educational work is needed among the local population, especially owners of summer cottages close to the highway.

We have developed information bulletins and leaflets that provide recommendations for reducing the impact of the highway on vegetable gardens:

If possible, remove your site from the source of pollution by not using land directly adjacent to the highway.
Do not use the soil on the site; plant it with plants more than 1 meter high (corn, dill, etc.)
In the future, remove these plants from the garden without using them.

List of sources used:

1. Vishnevsky L.D. Under the sign of carbon: Elements of group IV of the periodic table D.I. Mendeleev. M.: Education, 1983.-176 p.

2. Lebedev Yu.A. The Marathon Runner's Second Wind (About Lead). M.: Metallurgy, 1984 – 120 p.

3. Mansurova S.E. School workshop “Looking after the environment of our city.” M.: Vlados, 2001.-111 p.

4. Nekrasov B.V. Fundamentals of general chemistry. Volume 2. M.: Publishing house "Chemistry", 1969 - 400 p.

5. Nikitin M.K. Chemistry in restoration. L.: Chemistry, 1990. – 304 p.

6. Nikolaev L.A. Metals in living organisms. M.: Education, 1986. – 127 p.

7. Petryakov-Sokolov I.V. Popular library of chemical elements. Volume 2. M.: Publishing house “Nauka”, 1983. – 574 p.

8. Ruvinova E.I. Lead pollution and children's health. "Biology", 1998 No. 8 (February).

9. Sumakov Yu.G. Living devices. M.: Knowledge, 1986. – 176 p.

10. Sudarkina A.A. Chemistry in agriculture. M.: Education, 1986. – 144 p.

11. Shalimov A.I. The alarm of our alarm: ecological reflections. L.: Lenizdat, 1988. – 175 p.

12. Shannon S. Nutrition in the atomic age, or how to protect yourself from small doses of radiation. Minsk: Publishing House “Belarus”, 1991. – 170 p.

Slide captions:

Bashurova Maria 10th grade Novoorlovsk secondary school

Topic of work: STUDYING THE CONTENT OF LEAD COMPOUNDS IN THE ENVIRONMENT OF NOVOORLOVSK

Sources of lead contaminants: automobile batteries, aircraft engine emissions, lead-based oil paints, bone meal fertilizers, ceramic coatings on porcelain, cigarette smoke, lead or lead-lined pipes, the process of extracting lead from ore, exhaust fumes, solders, plants grown near highways

Hypothesis of work: Lead compounds are present in the environment of Novoorlovsk.

Purpose of the work: to study the content of lead compounds emitted into the air, accumulated in soil, plants, and snow.

Lead - Pb (Plumbum) serial number 82 atomic weight 207.21 This is a bluish-gray metal. He is malleable and soft. Melt = 327.4 degrees. In air it quickly becomes covered with a layer of oxide.

Lead Applications: Battery and Cable Industry. Indispensable in the manufacture of bearings, printing alloy and some types of glass.

Lead compounds: Pb (N O3)2 - lead nitrate, Pb 3(OH)2(CO 3)2 - lead dihydroxocarbonate (Pb 3 O 4) - minium (C2H5)4 Pb - tetraethyl lead (TES) (CH3)4 Pb – tetramethyl lead

Sources of lead compounds entering the human body: Food (canned food in tin containers, fresh and frozen fish, wheat bran, gelatin, shellfish and crustaceans.) Drinking water Atmospheric air Smoking

Lead is a cumulative poison. Accumulates in bones, liver and kidneys.

Saturnism is lead poisoning. Symptoms: severe weakness, abdominal spasms, paralysis, mental disorders

Name of the group of cars Quantity per 20 minutes, pcs Quantity per hour (N), pcs Total distance traveled per hour by all cars, km Emissions per 1 km by one car, g/km Emissions per 1 km by all cars, g/km Emissions for the total distance, g/km Passenger cars 6 18 1.8 0.019 0.342 0.62 Diesel cars 2 6 0.6 - - - Carburetor trucks with a load capacity of up to 3 tons 1 3 0.3 0.026 0.078 0.02 Carburetor trucks with a load capacity of more 3 t - - - 0.033 - - Carburetor buses 1 3 0.3 0.041 0.123 0.004 Diesel trucks 2 6 0.6 - - - Diesel buses 1 3 0.3 - - - Gas cylinder buses running on compressed natural gas - - - - - - Total 13 39 3.9 0.119 0.543 0.644

Sampling sites: 1. Road near the school 2. Central boiler house 3. JSC "Novoorlovsky GOK" 4. Forest 5. Road along the dacha cooperative.

Content of lead compounds on the soil surface (in snow). Sample tube number Sample collection site Presence of sediment Pollution level 1 Road near the school Yellow sediment Strong 2 Central boiler house Yellow sediment Strong 3 JSC Novoorlovsky GOK Yellow sediment Strong 4 Forest No sediment Weak 5 Road along the dacha cooperative Yellowish sediment Medium

Sources of lead compounds in Novoorlovsk: Central boiler house Highway CJSC Novoorlovsky GOK

Lead is dangerous for humans!!!

Thank you for your attention!

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Annex 1.

Treatment of lead poisoning.For acute poisoning, complexing agents are used, among which thetacin and pentacin are the most effective when administered intravenously (6 g of the drug per course of treatment in the form of a 5% solution). Agents that stimulate hematopoiesis are also used: iron preparations, campolon, cyanocobalamin, ascorbic acid. To reduce pain during colic, warm baths, 0.1% atropine sulfate solution, 10% sodium bromide solution, 0.5% novocaine solution, and a milk diet are recommended. To reduce vegetative-asthenic phenomena, you can use intravenous glucose with thiamine and ascorbic acid, bromine, caffeine, pine baths, and a galvanic collar. For encephalopathies, dehydrating agents are prescribed (25% magnesium sulfate solution, 2.4% aminophylline solution, 40% glucose solution); for polyneuropathy - thiamine, anticholinesterase drugs, four-chamber baths, massage, physical therapy.

To remove lead from the depot, liver diathermy and intravenous administration of a 20% sodium hyposulfite solution are used.

Protective agents: B vitamins, vitamin C, vitamin D, calcium, magnesium, zinc, pectin compounds, sodium alginate, various varieties of cabbage.

Appendix 2.

Prevention of lead poisoning.The main measure to prevent lead poisoning is to replace it with other, less toxic substances in those industries where it is used. For example, lead white is replaced with titanium-zinc, instead of lead gaskets for cutting files, gaskets made of a tin-zinc alloy are used, lead pastes for finishing passenger car bodies are replaced with pastes made of plastic materials. During technological processes, as well as when transporting lead and lead-containing materials, it is necessary to hermetically seal sources of dust emission, to equip powerful aspiration ventilation with cleaning of air contaminated with dust and lead vapor before releasing it into the atmosphere. It is prohibited to use the labor of women and teenagers in lead smelting processes. It is necessary to observe such personal hygiene measures as sanitation of the oral cavity, washing hands with a 1% solution of acetic acid, the use of special clothing and respirators, and therapeutic and preventive nutrition.

Appendix 3.

Results of the performed methodology

determination of emissions of lead compounds from motor vehicles.

Vehicle group name	Quantity in 20 minutes, pcs.	Quantity per hour (N), pcs.	The general path covered in an hour by all vehicles, Km	Emissions per 1 km per vehicle, g/km	Emissions per 1 km for all vehicles, g/km	Emissions over the total distance, g/km
Cars				0,019	0,342	0,62
Passenger diesel
Carburetor trucks with a lifting capacity of up to 3 tons				0,026	0,078	0,02
Carburetor trucks with a load capacity of more than 3 tons				0,033
Carburetor buses				0,041	0,123	0,004
Diesel trucks
Diesel buses
Gas tanks running on compressed natural gas
Total				0,119	0,543	0,644

Appendix 4.

Sample tube number	Sample collection area	Presence of sediment	Pollution level
	Road near school	Yellow precipitate	Strong
	Central boiler room	Yellow precipitate	Strong
	CJSC Novoorlovsky GOK	Yellow precipitate	Strong
	Forest	No sediment	Weak
		Yellowish sediment	Average

Appendix 5.

Sample tube number	Sample collection area	Presence of sediment	Pollution level
	Road near school	Yellow precipitate	Strong
	Central boiler room	Yellowish sediment	Average
	CJSC Novoorlovsky GOK	Yellow precipitate	Strong
	Forest	Yellowish	Weak
	Road along the dacha cooperative	Yellowish sediment	Average

Appendix 6.

Sample tube number	Sample collection area	Presence of sediment	Pollution level
	Road near school	Yellowish sediment	Average
	Central boiler room	Yellow precipitate	Strong
	CJSC Novoorlovsky GOK	Yellow precipitate	Strong
	Forest	No sediment	Weak
	Road along the dacha cooperative	Yellow	Strong