RU2468396C1 - Method of determining atmospheric aerosol concentration in megapolises - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method involves probing the atmosphere with a hyperspectrometer mounted on spacecraft, calculating total concentration of pollutants in percentages [%]_Σ based on the ratio of total ΔW_Σ attenuation of the reference Planck light flux passing twice through the atmosphere to attenuation ΔW(O₂) thereof in the oxygen O₂ absorption band, wherein atmospheric concentration of oxygen is equal to 21%; [%]_Σ=21%·ΔW_Σ/W(O₂); calculating relative shift (λ/λ_ref) of the weight-average wavelength reference Planck solar flux; calculating, based on an empirical relationship, concentration of pollutant gases [%]_gases in the atmosphere based on the calculated relative shift (λ/λ_ref); determining the difference Δ[%]=[%]_Σ-[%]_gases between total concentration of pollutants and concentration of gases and matching the obtained difference Δ[%] with the aerosol concentration on the probed path.

EFFECT: determining atmospheric aerosol concentration in megapolises using a single spectrometric measurement technique while eliminating requirements for simultaneous measurement of reference areas.

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Description

The invention relates to the field of ecology, in particular to remote methods for monitoring natural environments, and can find application in systems of sanitary and epidemiological control of industrial regions.

Industrial progress is inevitably associated with an increase in emissions of so-called "greenhouse" gases into the atmosphere, which are one of the causes of global climate change on the planet. Monitoring the state of air pollution is an integral part of the responsibilities of states that have signed the Kyoto Protocol on environmental environmental monitoring. The main types of environmental pollution subject to global monitoring by UNEP are: carbon dioxide CO ₂ , nitrogen dioxide NO ₂ , sulfur dioxide SO ₂ . Under anticyclonal conditions in the surface layer, aerosols of both anthropogenic nature and dust haze accumulate from transboundary global transport, the concentration of which is hundreds of ppm.

There is a method of assessing the state of the atmosphere by calculating the index of its state [see, for example, “Methodology for calculating the concentration of harmful substances in atmospheric air contained in emissions of enterprises”, All-Union Normative Document, OND-86, USSR, Gidrometeoizdat, Leningrad, 1987, p. 4-5, as well as the Yearbook of the State of Atmospheric Pollution in Cities on the Territory of Russia, edited by E.Yu. Bezuglova, GGO named after A.I. Voeykova, St. Petersburg, 1994-1996. - analogue].

Usually, the state index is calculated for five components that determine the main contribution to air pollution:

where m _i [mg / m ³ ] is the average annual concentration of the i-th substance in the atmosphere;

CH _i [mg / m ³ ] - the maximum permissible sanitary norm for the concentration of the i-th substance in atmospheric air, according to GOST;

j is an indicator of the degree of isoeffectiveness of a harmful substance equal to 0.85, 1, 1.3, 1.5 for substances of hazard classes IV, III, II and I, respectively;

MPC is the maximum permissible concentration of substances in the atmosphere.

The disadvantages of the known analogues are:

- statistical instability of the method of single local measurements on the ground at control points as such;

- the uncertainty of the choice of the control points of sampling and the dependence of the measurement result on random turbulence of the atmosphere at the sampling points.

The well-known "Method for the determination of atmospheric pollution in megacities," Patent RU No. 2422859 from 06/27/2011 - the closest analogue. The closest analogue method involves remote measurement by a hyperspectrometer of the spectral characteristics of the reflected light flux from the atmosphere-underlying surface border with the simultaneous obtaining of an image of a region containing control industrial sites in the red band 570 ... 670 nm, calculation of the weighted average wavelength λ and reflected flux energy W, determination air pollution regression dependence:

q _Σ [MPC] = 1.2 (λ / λ _et ) ^1.5 · (W _et / W) ^2.6 ;

sorting the image pixels by brightness, building a histogram of their distribution and linking the average histogram value to the calculated q _Σ value, calculating the absolute distribution of atmospheric pollution over the region in the form of a Rayleigh distribution with calculated numerical characteristics, where

q _Σ is the average value of the atmospheric index of the region, MPC;

λ _et - weighted average wavelength of the reference (according to Planck) solar spectrum, equal to ~ 500 nm;

W _et - the energy of the reference solar spectrum, normalized relative to the maximum.

The disadvantages of the closest analogue are:

- the need for the mandatory presence in the image of the region of the control industrial site for calibration of the measuring path;

- the impossibility of a separate assessment of air pollution by impurity gases and aerosols.

The problem solved by the claimed method consists in quantitatively measuring the concentration of aerosols in the atmosphere by finding the difference between the integral attenuation of a reference (according to Planck) solar flux that has twice passed through the atmosphere and its attenuation when interacting with impurity gases, determined by the shift of the weighted average wavelength of the reference spectrum.

The problem is solved in that the method for determining the concentration of aerosols in the atmosphere of megacities involves sensing the atmosphere with a hyperspectrometer mounted on a space carrier, calculating the total concentration of pollutants in percent [%] _Σ with respect to the total attenuation ΔW _{Σ of the} standard attenuation, according to Planck, of the light flux that has twice passed through the atmosphere to its attenuation ΔW (O ₂ ) in the oxygen absorption band of O ₂ , the concentration of which in the atmosphere is 21%; [%] _Σ = 21% · ΔW _Σ / W (O ₂ ), calculation of the relative shift (λ / λ _et ) of the average wavelength of the reference, according to Planck, solar flux, calculation, according to the empirical dependence, the concentration of impurity gases [%] _gases in the atmosphere from the calculated relative shift (λ / λ _et ), determining the difference Δ [%] = [%] _Σ - [%] of _gases between the total concentration of impurities and the concentration of gases and identifying the resulting difference Δ [%] with the concentration of aerosols on the probed path .

The invention is illustrated by drawings, where:

figure 1 - reference (according to Planck) solar spectrum (1), its shift and absorption (2) in the atmosphere of megacities;

figure 2 - method of measuring the attenuation of the light flux, twice passed through the atmosphere;

figure 3 - absorption band (transmission) of the solar stream with atmospheric oxygen, selected as a reference;

figure 4 - the interaction of photons of the solar stream with molecules of impurity gases;

figure 5 - dependence of the relative shift of the average wavelength of the solar spectrum on the concentration (MPC) of impurity gases;

6 is a family of calculated implementation of the concentration of aerosols in the atmosphere on the probed track;

7 is a functional diagram of a device that implements the method.

The technical essence of the method is as follows.

From a mathematical point of view, for a unique solution to the problem, the number of measured quantities should be equal to the number of unknowns. In the claimed method, the concentration of aerosols is determined through the difference between the integral attenuation of the light flux and its attenuation caused only by impurity gases. Therefore, it is necessary to use two independent methods for measuring two parameters based on different physical principles. On aerosols, the light flux decays as a result of diffuse scattering. The attenuation of the light flux on impurity gases is due to resonant absorption of energy and fluorescence re-emission of absorbed energy. In accordance with the Stokes law, re-emission of energy by molecules always occurs at a large wavelength, i.e. as a result of the interaction of the light flux with molecules of impurity gases, a shift of the solar spectrum to the long-wave (red) region is observed. Thus, the selectable (measured) parameters that ensure the uniqueness of the problem being solved are: the integral damping of the light flux and the shift of the spectrum to the red region of the visible range.

A disadvantage of remote sensing methods is their dependence on the shooting conditions (viewing angle, solar height, season, day). This requires a reference calibration of the measurement path. In known analogues, the calibration of the spectrometric measurement path is carried out by means of a brightness standard illuminated by the Sun, made in the form of a milky matte plate made of MS-14 glass, installed near the entrance slit of the spectrometer. In the claimed method, the function of the solar spectrum I (λ) is used as a reference. The reference function of the solar spectrum, normalized to the maximum intensity, is illustrated in the graph of FIG. 1. The method of measuring the integral attenuation of the light flux along the propagation path that has twice passed through the atmosphere is illustrated in the graph of FIG. 2.

The Earth’s atmosphere contains a known composition of gases: nitrogen - 78%, oxygen - 21%, argon - 0.9%, in small percentages carbon dioxide, hydrogen, helium, neon and other gases [see “Soviet Encyclopedic Dictionary” edited by A.M. Prokhorov, 4th edition, Sov. Encyclopedia, 1989, Atmosphere, p. 86]. It is known from Kirchhoff’s experiments that the continuous solar spectrum, passing through the gaseous medium, becomes ruled, dark lines or absorption bands appear in it. Monatomic gases have a linear absorption spectrum that coincides in the position of the spectral lines with the emission spectrum. In the claimed method, the measurement of integral absorption is carried out on the basis of an analysis of the absorption of a light beam that has twice passed through the atmosphere in the entire visible range by comparison with the absorption of the beam in the spectral band of oxygen (O ₂ ), the concentration of which in the atmosphere is known. The method of spectrometric measurements of the light flux that has twice passed through the atmosphere is illustrated in the figure of FIG. 2.

The attenuation energy of the light flux due to absorption by harmful impurities along the propagation path that has twice passed through the atmosphere is calculated from the ratios:

ΔW _Σ = W _etal -W _whitefish (measurement);

The signal attenuation in the oxygen absorption band O _2, respectively:

ΔW (O ₂ ) = W _etal -W _whitefish (B band O ₂ );

Where does the integral concentration of impurities in the atmosphere come from (given the fact that the integral attenuation is proportional to the integral concentration):

[%] _Σ = 21% (O ₂ ) · ΔW _Σ / W (O ₂ ); ( ^* )

. Полную эталонную энергию светового потока вычисляют по соотношению Рэлея [см., например, Заездный В.М., «Основы расчетов по статистической радиотехнике», Связь-издат, М, 1964 г., стр.93-94]:The energy of one quantum (according to Planck's quantum theory) w = hν, where h is the Planck constant, ν is the frequency. Since the wavelength λ = c / ν (c is the speed of light), then the quantum energy:

. The full reference energy of the luminous flux is calculated by the Rayleigh ratio [see, for example, Zayezdny VM, “Fundamentals of calculations on statistical radio engineering”, Svyaz-publ, M, 1964, pp. 93-94]:

,

,

where I (λ _i ) is the amplitude of the reference signal on the spectral line λ _i ;

n is the number of spectral lines in the attenuation band on which harmful impurities are measured.

The stability of the measurement result, independent of systematic errors, the height of the Sun, the azimuth of sounding, the reflection coefficient from the underlying surface, is also achieved using the method of ratios of increments of measured values (formula ^* ).

Based on the foregoing, priority is given to the correct choice of the spectral absorption band for oxygen (O ₂ ). The graphs of figure 3 shows the oxygen absorption band used as a reference standard for measurements. Signal attenuation on harmful impurities is measured on all spectral components of the visible range.

As a second independent parameter, the shift of the solar spectrum to the long-wavelength region is measured. The interaction of solar radiation with anthropogenic particles occurs at the molecular level. When photons of the light flux collide with gas molecules, energy quanta (hυ ^* ) are transferred to the molecules, which transform into an excited state. The interaction of the light flux with the smog molecules is illustrated in Fig.4. For all types of possible interaction of the light flux with smog molecules over megacities, such as absorption, scattering, and fluorescence re-emission, the integral effect is to shift the spectrum of the visible range to its long-wavelength part (red region), [see, for example, R. Mežeris, Laser remote sensing, translation from English, Mir, M, 1987, p. 124, table 3.4 Wave numbers of the Raman shift at a wavelength of 337.1 nm]. Below are some extracts from this Table for some impurity smog molecules.

Type of substance molecule NO ₂ SO ₂ CO ₂ NH ₃ C ₂ H ₂ H ₂ s With NO H ₂ O The wavelength of scattered radiation, nm 345.7 350.8 352.5 378.8 380.3 369 363.9 365.9 384.4 The absolute value of the displacement Δλ, nm 8.6 13.7 15.4 42.7 43,2 32 16.8 18.8 47.3

As a result of the Raman scattering of sunlight, energy is redistributed between the spectral components of the visible range, and the recorded spectral image of anthropogenically contaminated sites acquires a predominantly reddish or dark cherry hue. The integral effect of the interaction of photons of the light flux with smog molecules consists in shifting the spectrum of the visible range to the long-wave (red) region.

The quantitative parameter of such a displacement is the weighted average wavelength λ _{sr of the} reflected flow, calculated as:

The weighted average wavelength divides the area under figure 1 in half. The weighted average wavelength of the reference (according to Planck) spectrum is λ _et ≈500 nm. Depending on the smog power (MPC), the relative displacement reaches λ / λ _fl ≈1.1 ... 1.4, as illustrated in the graph of FIG. 5. The calculated shift of the weighted average wavelength and the graph of figure 5 determine the pollution of the atmosphere by impurity gases (q). The main impurity gases subject to global monitoring by UNEP: СО ₂ , NO ₂ , SO ₂ - have approximately equal molar weight. It is known that one mole of any gas occupies a volume of 22.4 liters. This allows you to get a robust estimate of the concentration of impurity gases analytically from the relationship:

Specific calculated values are given in an example implementation.

An example implementation of the method.

The claimed method can be implemented according to the scheme of Fig.7. Functional diagram of the device contains a spacecraft (SC) observation 1, type "Resource". A hyperspectrometer 2 (of the Astrogon type) is installed on the spacecraft. Frame-by-frame shooting of the planned regions 3 is carried out by commands from the onboard control complex (BCC) 4 from the Mission Control Center (MCC) 5 via the command control radio line 6. The measurement results are recorded in the buffer memory 7 and according to the BCC commands, in the spacecraft radio visibility zones from ground points are reset via the mobile communication channel 8 to the information reception points (PPI) 9. After the preliminary processing of the frames according to service signs (number of revolution, time of shooting, coordinates of the site) on the means of 10 information They are transferred to the Thematic Processing Center 11, where through the input device 12 it is inserted into the PC 13 in a standard set of elements: a processor 14, a hard drive 15, random access memory (RAM) 16, a display 17, a printer 18, a keyboard 19. Impurity concentration measurements gases along the flight path of the spacecraft are displayed on the server 20 of the Internet.

The Astrogon-1 hyperspectrometer has several parallel spectral channels in the visible, including in the near infrared range of 0.9-1.6 μm, with a spectral resolution of 1.5 to 50 nm, a quantization resolution of 12 bits, and a field of view angle 0.11 ° [see, for example, “Vulkan-Astrogon Small Spacecraft with a high-resolution hyperspectrometer”, Engineering Note, RAKA, NIIEM, STC “Reagent”, pp. 8-10].

With the initial data of the sensing path in the oxygen absorption band of the reference (according to Planck) function of the solar spectrum (Fig. 1 (1)) and its shift (Fig. 1 (2)), the dependence of q gases on the relative shift of the spectrum (λ / λ _et ) figure 5, the calculated values of the estimated parameters are presented in table 1.

Table 1 Shift λ / λ _et q [%] _gases Attenuation in the band O ₂ ΔW _Σ (O ₂ ) The total signal attenuation ΔW _Σ Aerosol concentration, ppm 1.15 1,5 0.0026 0.0057 0.0042 fifteen 1.25 3 0.0057 0.0057 0.0048 twenty 1.4 6 0.0034 0.0057 0.0073 60

Graphs of the calculated values of the concentration of aerosols are illustrated in Fig.6.

The effectiveness of the method is characterized by the possibility of separate measurement in the atmosphere of impurity gases and aerosols according to a single spectrometric measurement technology while removing the requirements for the simultaneous measurement of control sites. The latter allows trace measurements of atmospheric pollution on a global scale on any illuminated portion of the orbit of a space carrier.

Claims (1)

A method for determining the concentration of aerosols in the atmosphere of megacities involves sensing the atmosphere with a hyperspectrometer mounted on a space carrier, calculating the total concentration of pollutants in percent [%] _Σ with respect to the total attenuation ΔW _{Σ of the} standard attenuation, according to Planck, of the light flux that has twice passed the atmosphere to its attenuation ΔW (O ₂ ) in the absorption band of oxygen O ₂ , the concentration of which in the atmosphere is 21%; [%] _Σ = 21% · ΔW _Σ / W (O ₂ ), calculation of the relative shift (λ / λ _et ) of the average wavelength of the reference, according to Planck, solar flux, calculation, according to the empirical dependence, the concentration of impurity gases [%] _gases in the atmosphere from the calculated relative shift (λ / λ _et ), determining the difference Δ [%] = [%] _Σ - [%] of _gases between the total concentration of impurities and the concentration of gases and identifying the resulting difference Δ [%] with the concentration of aerosols on the probed path .

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