Methods for determining air dust levels are divided into two groups:
With the release of a dispersed phase from an aerosol - weight or mass (gravimetric), counting (conimetric), radioisotope, photometric;
Without isolating the dispersed phase from the aerosol - photoelectric, optical, acoustic, electrical.
The basis for hygienic regulation of dust content in the air working area The weight method is used. The method is based on drawing dust-laden air through a special filter that traps dust particles. Knowing the mass of the filter before and after sampling, as well as the amount of filtered air, the dust content per unit volume of air is calculated.
The essence of the counting method is as follows: a certain volume of dust-laden air is selected, from which dust particles are deposited onto a special membrane filter. Then the number of dust particles is counted, their shape and dispersion are examined under a microscope. Dust concentration using the counting method is expressed by the number of dust particles in 1 cm 3 of air.
The radioisotope method for measuring dust concentration is based on the property of radioactive radiation (usually α-radiation) to be absorbed by dust particles. Dust concentration is determined by the degree of attenuation of radioactive radiation when passing through a layer of accumulated dust.
approved by the Ministry of Health and Social Development regulatory documents to determine dust content:
MU No. 4436-87 “Measurement of aerosol concentrations of predominantly fibrogenic action”;
MU No. 4945-88 “Guidelines for the determination of harmful substances in welding aerosol (solid phase and gases).”
Measuring dust content by gravimetric method
When measuring dust concentration, a pre-weighed “clean” filter AFA-VP-20 (AFA-VP-10) is fixed in a cartridge (allonge), which is connected with a hose to a PU-3E aspirator and such an amount of air is drawn through the filter so that the sample of collected dust is from 1.0 to 50.0 mg (for AFA-VP-10 from 0.5 to 25.0 mg).
The analytical aspiration filter (AFA) is made from filter fabric FPP-15, which has a charge of static electricity. The use of analytical filters of the AFA type makes it possible to analyze the air environment with a high degree of accuracy. They have high retention capacity, low aerodynamic resistance to air flow, high throughput (up to 100 l/min), low weight, low hygroscopicity, and the ability to determine dust concentration regardless of its physical and chemical properties. For ease of handling, the edges of the filters are crimped and placed in protective cages (Fig. 2).
Rice. 2. AFA type filter
1 – filtration material; 2 – protective clip
Aspirators are used for sampling. Methods and equipment used to determine dust concentration must ensure the determination of dust concentration at a level of 0.3 MAC with a relative standard error not exceeding ±40% at 95% probability. At the same time, for all types of samplers, the relative standard error in determining dust at the MPC level should not exceed ±25%. For sampling, it is recommended to use filters AFA-VP-10, 20, AFA-DP-3.
After sucking out the dusty air, the filter is removed from the allonge, re-weighed on an analytical balance with an accuracy of 0.1 mg, and the mass of a sample of dust ΔP on the filter is determined by the difference in the masses of the “clean” and “dirty” filters.
Dust concentration under operating conditions:
, mg/m 3 (1)
where ΔР = Р к – Рн – mass of dust captured by the filter, mg; Р n and Р к – mass of the AFA filter, respectively, before and after aspiration, mg; V deputy– volume of air from which dust was separated on the filter, m3.
Simultaneously with taking air samples for dust content, temperature (T, 0 C) and air pressure (B, mm Hg) are measured to bring the volume of air under operating conditions V deputy, from which dust was isolated on the filter, to standard conditions (760 mm Hg .st. and 20 0 C):
, m 3 (2)
Then the concentration of dust in the air under standard conditions:
, mg/m 3 (3)
The results of measurements and calculations are used for sanitary and hygienic assessment of the air in the working area according to the dust factor, correlating with maximum permissible concentrations (MPC), as well as to determine the effectiveness of methods and means of combating dust.
ASSESSMENT OF DUST CONTAINMENT IN THE AIR OF AN EDUCATIONAL INSTITUTION AND ITS TERRITORY
Shatilov Evgeniy
2nd year, PU No. 60, Kansk
Khartonen Marina Nikolaevna
scientific supervisor, teacher of the second category, teacher of chemistry, biology, master of teaching, vocational school No. 60. Kansk
Fomina Snezhanna Valerievna
scientific supervisor, teacher highest category, physical education teacher, head of physical education at PU No. 60, Kansk
Introduction
Modern ecology is a science that understands the fundamentals of the sustainability of life at all levels of its organization. Ecology is the scientific basis for competent relationships between society and nature, rational use natural resources, and thereby maintaining humanity on Earth. One of the most pressing global environmental problems is the problem of environmental pollution, and, in particular, the atmosphere.
Purpose: Experimental study of air dust content assessment educational institution and its territory.
Objectives: Studying the characteristics of the functioning of urban ecosystems;
Study of types of pollution;
Analysis of dust content in the air in an educational institution and on its territory
Object: Educational institution of vocational school No. 60 in Kansk, Krasnoyarsk Territory and its territory
Subject: Tree leaves and school classrooms
Features of urban ecosystems.
Characteristics modern stage social development are the rapid growth of cities and the increase in the number of people living in them. The process of growth of cities, urban population, increasing the role of cities, widespread urban lifestyle is called urbanization (from the Latin Urbos - city). New research is studying the urban environment, its main components and the factors influencing them, and the history of its formation. scientific field knowledge - urban ecology, or city ecology. Urban systems are open, probabilistic, controllable systems. Important feature urban systems is their anthropocentrism. Famous ecologist N.F. Reimers wrote: “It is necessary to turn to man and save the Earth from our own zeal. The very goal of development has changed. Until recently, it seemed that it was enough to feed a person and make him rich. Now it turns out that in order to live a long time and not get sick, this is not enough. We also need a favorable living environment. The appeal to man led to a new form of anthropocentrism - anthropocentrism. Finally the last one, and most important component urban systems - population as a result of the active transformative activity of mankind a new ecological environment with a high concentration of anthropogenic factors. One of the acute problems of such urban communities is environmental pollution.
Pollution as one of the problems of the urban ecosystem.
Types of pollution.
According to the definition of one of the leading ecologists of Russia N.F. Reimers, environmental pollution is the introduction into the environment or the emergence of new, usually not characteristic of it, physical, chemical, informational or biological factors, or an excess of the natural level of these factors in the environment, leading to negative consequences. There are many types of pollution. T.V. Stadnitsky and A.I. Rodionov distinguishes the following types of ecosystem pollution: parametric, biocenotic, stationary-destructive. ingredient.
Dust pollution as a negative environmental factor.
Air dust is the most important environmental factor that accompanies us everywhere. Dust - fine solids organic or mineral origin. There is no harmless dust. The environmental hazard of dust to humans is determined by its nature and concentration in the air. Dust can be divided into two large groups: fine and coarse. It is very important to be able to assess air quality by the dust content in it and present its environmental hazard. Therefore, I decided to study the dust content of the air on the territory of the educational institution and in the premises of our school
Practical part.
Studying the degree of air dust in various places of the educational institution
To get the job done I needed some clear adhesive film.
I collected leaves from different parts of the educational institution and at different heights:
Table 1.
Sample collection sites
I applied an adhesive transparent film to the surface of the leaves. Then I removed the film from the leaves along with a layer of dust and glued it to a sheet of white paper. I compared the prints with each other. The samples were arranged according to the degree of contamination, starting with the greatest. I received the following results:
Table 2.
Sample contamination results
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Degree of pollution |
Sample No. |
Thus, the amount of dust in samples collected near the highway is significantly greater than in samples collected at the school site. And the amount of dust on samples collected at a height of 30 cm significantly exceeds the amount of dust on samples taken at a height of 2 m. Based on the results of the study, I concluded that green spaces play an important role in cleaning the atmospheric air from dust. I also conducted an experiment to determine the relative dust content of the air in classrooms. To complete the work I needed: water, a microscope with an X-8 lens (eight-fold magnification), a pipette, cover glasses and slides for the microscope. I applied 1 drop of water to four glass slides. Slides were placed for 15 minutes at a height of 1 m from the floor: 1. Slide No. 1 in the classroom during recess, 2. Slide No. 2 in the corridor during recess, 3. Slide No. 3 in the classroom during the lesson, 4. Slide #4 in the hallway during class. Then he covered the drop with the dust particles deposited on it with a cover glass, thus preparing a microslide. The micropreparation was placed on the microscope stage. I achieved such a magnification that in the field of view of the microscope there was as much as possible large area drops. He counted the number of dust particles in a drop and described their composition: Table 3. Dust research results Thus, the relative dustiness of classrooms during recess is much greater than during class. During recess there is more dust in the school corridors, and during lessons there is more dust in the classroom. This is due to the location of the main number of students. Conclusion Ambient air pollution is of greater concern to people than any other type of environmental destruction. As for the dust content in the air at our school and on its territory, I believe that the main measures to reduce it should be: 1. reducing overall air pollution in the city and in our area; 2. increasing the amount of green space on its territory, especially that part of it that borders the highway (it is estimated that one hectare of lawn binds 60 tons of dust); 3. to reduce the amount of dust in the school premises, carry out regular wet cleaning classrooms and corridors; 4. All students are required to have replacement shoes throughout the school year. References:
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A well-studied and long-used method for assessing dust content in the air of industrial enterprises is the weight method, the essence of which is to determine the weight gain when passing a certain volume of test air through a filter. Cotton (absorbent) or glass wool are usually used as filters. IN glass tube, called dust, or allonge, with ground stoppers, place 0.5 g of hygroscopic or 2 g of glass wool so that the thickness of the filter layer is 3-4 cm. The density of the filter should be such that when passing through the tube 15-20 ml of air into minute the filter resistance was approximately 100 mm water. Art.
The equipped and tested dust tube is brought to a constant weight by drying. A sample is taken at the breathing level of the worker, recording the volume of air passed through. To obtain a more accurate result, at least two samples are taken at each measurement point.
After completing the measurements, the dust tube is brought back to a constant weight by drying. The difference in the weight of the tube before and after passing dusty air characterizes the dust content in the volume of air passed through the tube. An idea of the dust content of the air under study is given by subsequent recalculation per unit volume (cubic meter of air) and comparison with the established sanitary standard.
In some cases, it is necessary, along with the dust concentration, to also know the particle size (dispersity) of the dust, and sometimes the number of dust particles contained in a unit volume of air. For this purpose, the method of direct observation and counting using a microscope can be used.
In production conditions, when using the gravimetric method, commercially available aerosol analytical filters of the AFA type made of perchlorovinyl fiber are usually used. IN lately In the study of dusty flows, radioisotope, optical, electron probe and other methods have become widespread.
Now the industry has mastered the production of various instruments and installations for the analysis of aerosols: radioisotope dust meter “Priz-2” (determination of dust concentrations in the air of the working area in the range of 1–500 mg/m3); control and measuring complex "Post-1" (automatic measurement and recording of contents in atmospheric air dust and soot), integrated laboratory "Post-2", automatic single-channel sampler APP-6-1 (sampling aerosol from the air for
determination of concentrations by direct method), individual dust dosimeter DP-1 (aerosol sampling to determine concentrations by direct method when air dust content is more than 15 mg/m3), sampling device PU-ER-220, sampling device PU-ER-12 (air sampling with subsequent determination of concentration, dispersed, mineral, chemical, microbiological composition and study of aerosol properties with the parallel use of gravimetric, optical, granulometric, electron probe and microbiological analysis of deposited aerosol particles)
Name the types of artificial grounding conductors.
Extension and contour + horizontal and vertical (conditional)
20. How can you reduce the resistance of the ground electrode?
The total grounding resistance depends, as mentioned above, on the resistance of the soil layers adjacent to the ground electrode. Therefore, it is possible to reduce the grounding resistance by lowering resistivity soil only in a small area around the ground electrode.
An artificial reduction in soil resistivity is achieved either chemically using electrolytes, or by laying grounding conductors in pits with bulk coal, coke, or clay.
Dustiness
1, What is called dust?
Dust is defined as crushed particles of a solid substance that can remain suspended in the air for some time.
2. What is the hygienic hazard of dust?
Dust is a hygienic hazard, as it negatively affects the human body. Under the influence of dust, diseases such as pneumoconiosis, eczema, dermatitis, conjunctivitis, etc. can occur. The finer the dust, the more dangerous it is for humans. The most dangerous particles for humans are considered to be particles ranging in size from 0.2 to 7 microns, which, when entering the lungs during breathing, are retained in them and, accumulating, can cause illness.
There are three ways dust can enter the human body: through the respiratory system, gastrointestinal tract and skin.
3, what is the maximum permissible concentration of a harmful substance?
Maximum permissible concentration (MPC) is a sanitary and hygienic standard approved by law. MPC means this concentration chemical elements and their connections in environment, which, when exposed to everyday life for a long time on the human body, does not cause pathological changes or diseases established modern methods research at any time in the life of the present and subsequent generations.
The essence of the gravimetric method for determining dust concentration.
The essence of the method is that a certain volume of dust-laden air is passed through a highly efficient filter and the mass concentration of dust is calculated by increasing the mass and volume of filtered air:
5. How is dust count concentration measured?
Its essence lies in the preliminary separation of dust from the air and its deposition on glass slides, followed by counting the number of particles using a microscope. By dividing the calculated number of particles by the volume of air from which they are deposited, we obtain the countable concentration of dust (particles/l):
6. How is the volume of air sucked through the filter measured using the gravimetric method for measuring dust concentration?
V0 – volume of filtered air reduced to normal conditions(temperature 0 °C and barometric pressure B0 = 760 mm Hg), m3.
where P0, P – barometric pressure, Pa, respectively, under normal and operating conditions (P0 = 101325 Pa, P = B×133.322 Pa); T – air temperature at the place of dust collection, °C; V – volume of air passed through the filter at temperature T and pressure B, m3,
Where w– volumetric speed of air suction through the filter, l/min;
t– duration of sampling, min.
7. What sanitary and technical measures can reduce dust concentrations in workplaces to the MAC level?
7.4. To reduce dust and create acceptable microclimate parameters in vehicle cabins, it is necessary to seal doors and windows and use installations for cleaning, heating or cooling air.
7.5. Application in sections of machines with engines internal combustion without effective means Neutralization and purification of exhaust gases is not permitted. Neutralizers and cleaning agents must ensure that the content of harmful substances in the air of the working area is at levels not exceeding the maximum permissible concentration. The use of leaded gasoline is prohibited.
7.6. The traffic schedule of vehicles should not allow their accumulation with running engines on work sites, ledges, or sections of the road. The minimum distance between heavy-duty dump trucks (10 tons and above) must be at least 30 m. When organizing loading operations, preference should be given to a loop pattern for vehicle access to the loading site.
7.7. The rock mass loaded into the body of a dump truck, wagon or onto a conveyor belt must be irrigated during the warm season. The irrigation torch must cover the loading area.
7.8. To improve air exchange in the sections, guides and protective aerodynamic devices should be provided to regulate natural air flows.
7.9. During long-term inversions and calm conditions in case of accumulation of harmful gases at workplaces in stagnant zones For cuts with a depth of more than 100 m, artificial ventilation must be provided using special devices.
7.10. When designing, manufacturing or importing mining, transport and other machines, one should take into account their possible use in various climatic-geographical regions and mountain-geological zones of the country (presence of: polar day and night, permafrost, specific rocks, strong winds, calms, temperature inversions, a wide temperature range of outside air from + 40 ° C to - 60 ° C, prolonged fogs), as well as the content of toxic substances in exhaust gases, which must comply with domestic standards.
performed by aspiration weight (gravimetric) method using an electric aspirator (Fig. 2).
Rice. 2. Electric aspirator for collecting single dust samples
Dust is a dispersed system, where the crushed substance (dispersed phase) is in a continuous dispersed medium, i.e. These are suspended in the air, slowly settling solid particles ranging in size from 0.001 to 100 microns or an aerosol.
The principle of operation of the electric aspirator is to draw a certain volume of air through the aspirator.
torus with the deposition of dust particles on a paper filter. The method is based on collecting dust from air sucked through a filter at a standard aspiration rate of 10-20 l/min. followed by conversion to 1 m 3 of air (1 m 3 = 1000 l). Air analysis can be carried out both in samples taken once (duration of sampling 15-20 minutes), and repeatedly at least 10 times a day at regular intervals with averaging of the data obtained (the frequency of sampling during the day determines the boron to assess the type of MPC - average daily or maximum one-time). Air sampling is carried out in the breathing zone. To take a sample, the filter is fixed in the allonge (cartridge) of the electric aspirator, and air is passed through it at a speed of 20 l/min. ( V ) for 10 minutes. ( T ). The volume of the selected air sample is calculated using the formula:
υ=Т V,
Where T – sampling time, min., V – sampling rate, l/min. A non-hygroscopic aerosol filter, which consists of ultra-thin polymer fibers fixed in a paper ring, is weighed on an analytical balance with an accuracy of 0.1 mg to ( A 1 ) and after ( A 2 ) air sampling. Dust content X 3 air in 1 m is calculated using the formula:
X = [(A 2 − A 1) 1000]/ υ,
Where X – dust content in the air, mg/m3; A 1 And A 2 − filter weight before and after sampling, mg; υ − air volume, l.
For the hygienic assessment of air pollution by dust, the established dust content is compared with the maximum or average daily maximum permissible concentration of non-toxic dust in the atmospheric air; characterize dispersed and chemical composition, morphological structure, electrical state, nature (organic, inorganic, mixed) and mechanism of formation (aerosol disintegration or condensation).
Hygienic dust standards for atmospheric air
− maximum one-time MPC mr 2 = 0.5 mg/m 3,
− average daily maximum permissible concentration s/s 3 = 0.15 mg/m 3 .
In health care facilities, requirements for dust content in the air are determined by the classification of premises by cleanliness and are limited to particle sizes of 0.5 microns and 5.0 microns.
IN production premises: MPC of non-toxic dust = 10 mg/m 3 , MPC of dust containing free silicon dioxide = 1-2 mg/m 3 .
3. Determination of microbial air pollution osu-
It is carried out by the aspiration method in Kro-tov’s modification. The Krotov apparatus is an aspirator with a removable lid. The air being tested is sucked in at a speed of 20-25 l/min. through a wedge-shaped slot in the cover of the device. When transferring the Krotov apparatus from one room to another, its surface is treated with a disinfectant solution. An air sample is taken for 10 minutes. ( T ) at a speed of 20 l/min ( V ). The volume of the selected air sample is calculated using the formula.
