RU2570392C2 - Method to determine coefficient of vertical diffusion of emissions of industrial enterprises in atmospheric boundary layer - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: invention relates to the field of research or analysis of materials, namely, to determination of coefficient of vertical diffusion of emissions of industrial enterprises in atmospheric boundary layer with the help of neutron-activation analysis. The method consists in the fact that in the specified direction from an industrial enterprise at different distances from 1 to 5 km they take at least 5 samples of epiphytic moss Pylaisia polyantha (Hedw.) B.S.G. from bark of birches, aspens and poplars at the height from 1.5 to 2 m. Besides, one sample is selected on a background territory with natural-climatic conditions, identical with the researched territory, and located at the distance of more than 100 km from industrial centres in direction opposite to the preferential wind rose. Moss samples are cleaned from foreign admixtures, washed with distilled water, dried at temperature from 80 to 100°C, homogenized, and from 5 to 10 parallel representative samples are made. When using neutron-activation analysis, samples are exposed to radiation with a flux of thermal neutrons for 5 hours. After reduction of activities of Na²⁴ to safe level they determine specific activity of each sample by comparison of intensity of gamma lines of radio nuclides of chemical elements in a sample with intensity of gamma lines of standards. Values of concentrations of chemical elements in moss samples determined with the help of neutron-activation method, by the method of least squares are approximated by the dependence of the following type:

where q _b - background (natural) concentration of the chemical element in the sample chosen in the territory located at the distance from industrial enterprises from at least 100 km; x - distance from points of moss sampling to the industrial enterprise, determining at the same time numerical values of coefficients A, C and θ, then they calculate the coefficient of proportionality of vertical diffusion k₁:

where n - dimensionless parameter for interpolation of vertical profile of wind speed: u(z)=u₁zⁿ, where u₁ - average annual speed of wind at height of 1 m; H - height of an industrial enterprise stack, and use it to determine coefficient of vertical diffusion of emissions of industrial enterprises in atmospheric boundary layer according to the following formula: k_z=k₁z, where k₁ - coefficient of proportionality of vertical diffusion; z - height from earth surface.

EFFECT: invention provides for the possibility to use for any area regardless of its relief and with account of atmospheric conditions realised during exposure time.

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Description

The invention relates to the field of research or analysis of materials, namely, to determine the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere using neutron activation analysis of moss-biomonitors.

A known method for determining the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere [1. Layhtman D.L. Physics of the boundary layer of the atmosphere. L .: Gidrometeoizdat, 1970. - S. 130], based on the Solberg formula:

where R _n is the normal component of the internal friction force of atmospheric flows;

σ (z) is the length of the hodograph arc of the amount of movement of atmospheric air, measured from a point corresponding to the ground level;

z is the height from the surface of the earth, at which the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere is determined;

r is the radius of curvature of the hodograph.

To use the Solberg formula, it is necessary to measure at different heights of wind speed, air density and atmospheric pressure.

The disadvantages of the method:

1. Measurements of wind speed, atmospheric pressure and air density are carried out on the basis of a large series of (at least three) spherical observations, that is, they are labor-intensive and expensive processes.

2. The values of the coefficient of vertical diffusion of emissions of industrial enterprises obtained in this way in the surface layer of the atmosphere characterize well-defined atmospheric conditions when the wind speed, air density and atmospheric pressure, measured at different heights, can be considered constant. This condition is satisfied only for relatively short periods of observation.

3. The value of the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere, determined by this method, has a large error, since it is expressed through the derivative of the function σ (z), which is determined from experimentally measured wind speeds and air density at different heights.

A known method for determining the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere [1, p. 151-153.], Based on the formula:

where B (ε, z ₀ ) is a tabulated function depending on the parameters ε and z ₀ ;

ε is a parameter characterizing the temperature stratification of the atmosphere;

z ₀ - roughness parameter, depending on the terrain;

z ₁ - height from the surface of the earth and usually equal to 1 m;

u ₁ - wind speed at a height of z ₁ .

To implement this method, it is necessary to measure the wind speed at a height of z ₁ , as well as using spherical observations to determine the temperature gradient based on temperature measurements at different heights.

The main disadvantages of this method:

1. There are significant difficulties in determining the roughness parameter z ₀ . The data on this value presented in the literature for certain types of relief have a significant scatter. Usually the real terrain has a complex terrain that is difficult to attribute to any particular type.

2. The obtained values of the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere characterize a very definite state of the atmosphere and cannot be used for other rapidly changing conditions.

The closest is a method for determining the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere [2. Berland M.E. Prediction and regulation of air pollution. L .: Gidrometeoizdat, 1985. - S. 28], based on the formula:

k _z = k ₁ z,

where k ₁ is the coefficient of proportionality of the vertical diffusion, determined by the calculation method from the values measured experimentally,

z is the height from the surface of the earth, at which the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere is determined.

For a steady state of the atmosphere, the coefficient k ₁ is determined by the formula:

where æ = 0.38 is the aerodynamic constant of Karman;

u ₂ , u ₁ - wind speeds measured at two heights z ₂ and z ₁ .

Under nonequilibrium (unstable) conditions in the surface layer of the atmosphere, k ₁ is determined from the expression [3. Berland M.E. Current problems of atmospheric diffusion and air pollution. L .: Gidrometeoizdat, 1975. - S. 22]:

;where B is the stability parameter,

;

δT is the temperature difference at heights z ₃ and z ₂ ;

T _a - temperature on an absolute scale;

h is the height of the surface layer of the atmosphere;

g is the acceleration of gravity;

z ₁ , z ₂ , z ₃ - various heights measured from the surface of the earth.

To use this formula, it is necessary to measure temperatures at heights h, z ₂ , z ₃ , as well as wind speed at a height z ₁ of 1 m.

The main disadvantages of this method:

1. Obtained by this method, the values of the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere characterize a very definite state of the atmosphere and cannot be used for other rapidly changing conditions.

2. When calculating the coefficient of vertical diffusion of emissions of industrial enterprises in the atmospheric surface layer for unstable atmospheric conditions, difficulties arise associated with determining the roughness parameter z ₀ , since the topography is usually difficult to attribute to any one type.

3. The height of the surface layer of the atmosphere h is not unambiguous, since it varies over a wide range depending on the thermal stratification of the atmosphere, the magnitude of the wind speed, and the roughness of the earth's surface. Therefore, under various conditions, the value of the height of the atmospheric surface layer h varies from 50 to 250 m.

The objective of the invention is to develop a method for determining the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere, which can be used for any terrain, regardless of its topography and taking into account possible atmospheric conditions for this terrain.

The problem is solved due to the fact that the method for determining the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere, as in the prototype, includes measuring the wind speed at a height of 1 meter and determining the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere by the formula:

k _z = k ₁ z,

where k ₁ is the coefficient of proportionality of vertical diffusion;

z is the height from the surface of the earth at which the vertical diffusion coefficient is determined.

According to the invention, to determine the coefficient of proportionality of vertical diffusion k ₁ in a given direction from the industrial plant at different distances from 1 to 5 km, at least 5 samples of epiphytic moss Pylaisia polyantha (Hedw.) BSG are taken from the bark of birches, aspen and poplars at a height of 1, 5 to 2 m. In addition, one sample is taken in the background area with natural and climatic conditions identical with the study area and remote to a distance of more than 100 km from industrial centers in the direction opposite to the predominant rose moat.

The moss samples are cleaned of foreign matter, washed with distilled water, dried at a temperature of 80 to 100 ° C, homogenized, and 5 to 10 parallel representative samples are made. When using neutron activation analysis, the samples are irradiated with a thermal neutron flux for no more than 5 hours. After the activity of Na ²⁴ drops to a safe level, the specific activity of each sample is determined by comparing the intensity of the gamma lines of the radionuclides of chemical elements in the sample with the intensity of the gamma lines of the standards.

The values of the concentrations of chemical elements in moss samples, determined using neutron activation analysis, are approximated by the least squares method by the dependence of the form:

where q _f is the background (natural) concentration of the chemical element in the sample taken in the territory remote from industrial enterprises at a distance of at least 100 km;

x is the distance from the sampling points of the mosses to the industrial enterprise, while determining the numerical values of the empirical coefficients A, C and θ, then the proportionality coefficient of vertical diffusion k _{1 is} calculated:

where n is the dimensionless parameter for interpolating the vertical profile of the wind speed: u (z) = u ₁ z ⁿ ,

where u ₁ - the average annual wind speed at an altitude of 1 m;

H - pipe height of an industrial enterprise.

The found value of k _{1 is} used to determine the coefficient of vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere k _z .

Epiphytic moss Pylaisia polyantha (Hedw.) BSG has a long life cycle of up to 10-15 years, high accumulation abilities, wide distribution, high occurrence in various climatic zones, grow on the bark of old aspen, birch and poplar trees, therefore, they can be selected in the action area industrial enterprises. Using a specific length of moss growth allows you to vary the exposure time from 2-3 to 10-15 years, which allows you to determine the coefficient of proportionality of vertical diffusion k ₁ taking into account the topography of the underlying surface and various atmospheric conditions realized during the exposure.

The production of parallel representative samples from samples of selected epiphytic moss can reduce the measurement error without a significant increase in the cost of analysis. For analysis, it is necessary to use 5-10 parallel representative samples. The use of representative samples for neutron activation analysis provides a reliable determination of the concentrations of all chemical elements in the analyzed samples, which in turn makes it possible to construct with great accuracy and objectivity the dependence of the concentration of chemical elements in mosses on the distance from the pollution source and determine the vertical diffusion coefficient of industrial emissions in surface layer of the atmosphere.

In FIG. 1 presents a map of sampling in the zone of influence of a coal-fired CHPP-5 in Novosibirsk; numbers indicate sampling points.

In FIG. 2 presents a map of sampling in the zone of influence of the aluminum plant; numbers indicate sampling points.

Table 1 presents the average concentrations of Sm, Ce, Sr, Cs, Fe, Zn, Sc, Co, U, Eu, Yb accumulated in mosses, as well as the average values of the background (natural) concentrations of these elements (μg / g) for coal CHPP-5.

Table 2 presents the average concentrations of Al, Ba, Co, Cu, Li, Mn, Na, Sr, Ti, V accumulated in mosses, as well as the average background (natural) concentrations of these elements (μg / g) for Kandalaksha aluminum factory.

In FIG. 3 dots show the results of measurements of the concentrations of chemical elements in mosses taken in the northeast direction from the CHPP-5 of Novosibirsk, solid curves show the approximation of the measured concentrations of these elements, and the horizontal line shows the background concentrations of chemical elements in the moss Pylaisia polyantha (Hedw. ) BSG, where a) - Cs, b) - Eu.

In FIG. 4 dots depict the results of measurements of the concentrations of chemical elements in mosses taken northward from the Kandalaksha Aluminum Plant, the solid curves show the approximation of the measured concentrations for these elements, and the horizontal line shows the background concentrations of chemical elements in the moss Pylaisia polyantha (Hedw.) BSG, where a) - Al, b) - V.

Table 3 presents the numerical values of the empirical coefficients A, C, θ, the average annual wind speed u ₁ at a height of 1 meter, parameter n, as well as the vertical diffusion coefficient of the emissions of TEC-5 in Novosibirsk for different altitudes of the atmospheric surface layer.

Table 4 presents the numerical values of the coefficients A, C, θ, the average annual wind speed u ₁ at a height of 1 meter, the parameter n, as well as the vertical diffusion coefficient of emissions of the Kandalaksha aluminum plant for various heights of the atmospheric surface layer.

Samples of moss Pylaisia polyantha (Hedw.) B.S.G. in accordance with the wind rose, they were taken in the north-east direction from CHPP-5 in Novosibirsk in 2008 from the bark of old aspen and poplars at a height of 1.5-2 meters from the ground, which corresponds to the layer of air that an adult breathes: two samples three samples were taken at distances of 1-1.5 km, three samples at distances of 2-4 km (with the height of the CHPP-5 pipe H = 260 m) and two samples at distances of about 5 km (Fig. 1).

In accordance with the wind rose, samples of Pylaisia polyantha (Hedw.) BSG moss were taken northward from the Kandalaksha Aluminum Plant in 2013 at distances of 1-7 km through approximately equal sections of the path (with a pipe height of KAZ H = 120 m) (Fig. 2 )

In addition, one sample of moss was taken in the background areas remote to a distance of more than 100 km from industrial centers in the opposite direction to the predominant wind rose.

After sampling, the moss samples were cleaned of earth and various impurities, and then washed with distilled water. Samples of moss were dried to constant weight in an oven at a temperature of 80 ° -100 ° C and subjected to a homogenization process, and 5-10 parallel representative samples were made by quartering.

To study the concentrations of heavy metals and other trace elements in the selected samples of moss Pylaisia polyantha (Hedw.) BSG by the method of neutron activation analysis, tablets were pressed from each sample. For this, crushed and mixed moss was placed in a mold and a screw press was used. As a result, tablets weighing 0.1 ÷ 0.4 g with a diameter of 1 cm were obtained. All samples were weighed on an analytical balance and numbered. Each tablet was wrapped in aluminum foil. All samples were divided into several lots of 25-30 pieces. Each batch was wrapped together with IAEA standards (birch leaves - LB-1 and tobacco leaves - TOBAK-5) in a separate aluminum foil. Then, each package was placed in a high-purity aluminum canister and was irradiated in the channel of the VEK-6 reactor in a thermal neutron flux with a density of 5 × 10 ¹³ neutrons / cm ² · s for 5 hours. After irradiation, the samples were kept for a week, which is necessary for the activity of Na ²⁴ to decline to a safe level, and unpacked. All samples were placed in measuring containers, indicated by the serial number of each sample. The specific activity of each analyzed sample was measured on a semiconductor gamma spectrometer based on a semiconductor detector GC4020. The concentration of chemical elements was determined by the relative method, comparing the intensities of the analytical gamma lines of the radionuclides of the elements being determined with the intensities of the corresponding gamma lines of the standards, and the concentrations of the elements being determined were calculated [4. Kuznetsov Rafail Alekseevich. Activation analysis / R.A. Kuznetsov. - 2nd ed., Revised. and add. - Moscow, Atomizdat, 1974. - S. 37]. The measurement time was 1200-1800 seconds, depending on the specific activity of the measured samples. For processing gamma-ray spectra of equipment, the Genia-2000 program developed by CANBERRA was used. Thus, the average concentrations of the following elements in parallel moss samples taken on the territory of the coal-fired CHPP-5 in Novosibirsk were determined: Sm, Ce, Sr, Cs, Fe, Zn, Sc, Co, U, Eu, Yb (table 1) , and average concentrations of Al, Ba, Co, Cu, Li, Mn, Na, Sr, Ti, V in parallel moss samples taken at the aluminum smelter (table 2). The measurement error was 15-20%.

The average concentrations of the above chemical elements in the samples taken at different distances x from industrial enterprises were approximated using the least square method by the dependence of the species [5. Radioactive releases in the biosphere: reference book / N.G. Gusev, V.A. Belyaev. - 2nd ed., Revised. and add. - M .: Energoatomizdat, 1991. - S. 78. 6. N.K. Ryzhakova, V.F. Raputa, N.S. Rogova, A.L. Borisenko, E.A. Pokrovskaya. Spatial distribution of chemical elements of atmospheric emissions from a coal-fired power plant // Ecology and Industry of Russia, 2013, No. 1. - S. 53]:

where q _f is the background (natural) concentration of the chemical element in the sample taken in the territory remote from industrial enterprises at a distance of not less than 100 km;

x is the distance from the sampling points of mosses to an industrial enterprise;

A, C, θ are empirical coefficients, the numerical values of which are determined by the least squares method when approximating the measured concentrations of chemical elements contained in mosses by the function q (x) (table 3, 4).

The concentrations of chemical elements in mosses accumulated during the exposure are proportional to their content in the surface layer of the atmosphere, therefore, the dependence of the concentrations of chemical elements in mosses on the distance from the source has the same analytical form as the dependence of the content of pollutants in atmospheric air [2, p. 32]. Then for the empirical coefficient θ the following expression is true:

k ₁ - coefficient of proportionality of vertical diffusion;

n is a dimensionless parameter for interpolating the vertical profile of the wind speed: u (z) = u ₁ z ⁿ ,

where u ₁ - the average annual wind speed at an altitude of 1 m;

N - pipe height of an industrial enterprise, m

The expression for the coefficient of proportionality of the vertical diffusion of emissions of industrial enterprises in the surface layer of the atmosphere follows from the formula for the coefficient θ:

As can be seen from FIG. 3 and 4, the dependence of the concentrations of chemical elements on the distance x from the pollution sources is described by the function q (x).

Table 3 shows the values of empirical coefficients A, C, θ for different chemical elements determined using the least squares method, as well as the values of the coefficient of proportionality of vertical diffusion k ₁ and the coefficient of vertical diffusion of emissions of TPP-5 in the surface layer of the atmosphere k _z at an average annual speed wind at a height of 1 m u ₁ = 3.7 m / s, n = 0.2 [2, p. 28], the height of the CHPP-5 pipe H = 260 m and the height from the earth’s surface z equal to 50 m, 100 m, 150 m, 200 m and 250 m.

Table 4 shows the values of the empirical coefficients A, C, θ for different chemical elements, determined using the least squares method, as well as the values of the coefficient of proportionality of vertical diffusion k ₁ and the coefficient of vertical diffusion of emissions of the Kandalaksha aluminum plant in the surface layer of the atmosphere k _z at an average annual speed wind at a height of 1 m u ₁ = 2.3 m / s, n = 0.2 [2, p. 28], the height of the KAZ pipe H = 120 m and the height from the earth's surface z equal to 50 m, 100 m, 150 m, 200 m and 250 m.

Claims (1)

A method for determining the vertical diffusion coefficient of industrial emissions in the surface layer of the atmosphere, including measuring the wind speed at a height of 1 meter and determining the vertical diffusion coefficient of industrial emissions in the surface layer by the formula:
k _z = k ₁ z,
where k ₁ is the coefficient of proportionality of vertical diffusion; z is the height from the surface of the earth,
characterized in that at least 5 samples of the epiphytic moss Pylaisia polyantha (Hedw.) BSG from bark of birch, aspen and poplar at a height of from 1.5 to 2 m are taken in a given direction from the industrial enterprise at different distances from 1 to 5 km, except moreover, one sample is taken in the background territory with climatic conditions identical with the study area and removed more than 100 km from industrial centers in the direction opposite to the predominant wind rose, moss samples are cleaned of foreign matter, washed with distilled water, dried at a temperature of 80 to 100 ° C, homogenized, and 5 to 10 parallel representative samples are made, during neutron activation analysis, the samples are irradiated with a thermal neutron flux for no more than 5 hours, after the decrease in Na ²⁴ activities to a safe level, the specific activity of each sample by comparing the intensity of the gamma lines of radionuclides of chemical elements in the sample with the intensity of the gamma lines of standards, the concentrations of chemical elements in moss samples, determined using ytronno activation analysis, the method of least squares approximate the relation of the type:

where q _f is the background (natural) concentration of the chemical element in the sample taken in the territory remote from industrial enterprises at a distance of not less than 100 km;
x is the distance from the sampling points of mosses to an industrial enterprise, while determining the numerical values of the coefficients A, C and θ, then the coefficient of proportionality of vertical diffusion k _{1 is} calculated:

where n is a dimensionless parameter for interpolating the vertical profile of the wind speed;
u ₁ - the average annual wind speed at an altitude of 1 m;
H is the height of the pipe of an industrial enterprise, and use it to determine the coefficient of vertical diffusion of emissions of industrial enterprises in the atmospheric surface layer k _z .

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