Method for determining the source-dependent particle size distribution of aerosols and aerosol measurement device

Abstract

The present invention relates to a method for determining the source-dependent particle size distribution of an aerosol using an aerosol measurement device. First, a proportion parameter corresponding to the proportion of a source-dependent aerosol portion in an aerosol is determined. Further, by determining the particle size distribution of the aerosol particles, the source-dependent particle size distribution of the aerosol is determined from the proportion parameter and the particle size distribution. Regarding the device, the present invention includes an aerosol measurement device for determining the source-dependent particle size distribution of an aerosol, which can be used to determine the proportion parameter corresponding to the proportion of a source-dependent aerosol portion in an aerosol. Since the particle size distribution of the aerosol particles can be determined, the source-dependent particle size distribution of the aerosol can be determined from the proportion parameter and the particle size distribution.

Description

[Technical Field]

[0001] The present invention relates to a method and an aerosol measurement device for determining the source-dependent particle size distribution of an aerosol.

[0002] Aerosol in the sense of the present invention means a mixture of gas and solid and / or liquid suspended particles (aerosol particles), such as water droplets, soot particles, abrasion particles, pollen, bacteria, viruses, other organic substances and chemicals, etc. Particle size distribution means the concentration of aerosol particles as a function of particle size, and provides information about the frequency of each particle size in the aerosol. [Background technology]

[0003] Methods for determining the particle size distribution of aerosols are known and are used, for example, to detect fine dust pollution. In this case, the aerosol is always measured as a whole. For example, if the aerosol composition varies depending on the aerosol source, known methods do not allow for source-specific analysis. Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the present invention is therefore to develop a method and an apparatus which overcomes these drawbacks of the prior art, and in particular which should enable improved aerosol analysis. [Means for solving the problem]

[0005] This problem is solved by a method for determining the source-dependent particle size distribution of an aerosol using an aerosol measurement device, in which aerosol particles of an aerosol passing through a measurement cell are irradiated with a light beam within the measurement cell, scattered light is received by a sensor, the scattered light signals of the aerosol particles are detected spectroscopically in terms of intensity, a particle size distribution of the scattered light signals representative of the particle size distribution is created, a proportion parameter corresponding to the proportion of the source-dependent aerosol portion in the aerosol is determined, the particle size distribution of the aerosol particles is determined, and the source-dependent particle size distribution of the aerosol is determined from the proportion parameter and the particle size distribution.

[0006] Regarding the device, the problem is solved by an aerosol measurement device for determining the source-dependent particle size distribution of an aerosol, wherein aerosol particles of an aerosol in a measurement cell are arranged so that the aerosol particles can be irradiated by a light beam, the scattered light of the aerosol particles can be received by a sensor, and the scattered light signal of the aerosol particles can be detected by spectroscopy in terms of intensity, so that a particle size distribution of the scattered light signal representative of the particle size distribution can be created, a proportion parameter corresponding to the proportion of the source-dependent aerosol portion in the aerosol can be determined, the particle size distribution of the aerosol particles can be determined, and the source-dependent particle size distribution of the aerosol can be determined from the proportion parameter and the particle size distribution.

[0007] Furthermore, the object is achieved by a computer program comprising program code means which are designed to carry out the steps of the method according to the invention when the computer program is run on a computer or a corresponding computing unit.

[0008] The present invention is based on the fundamental idea that the composition of an aerosol varies depending on the aerosol source (hereinafter "source"), and therefore the aerosol has a source-dependent and a source-independent portion. An example of a source within the meaning of the present invention is a person within the aerosol's field, whose breath, as an example of a source-dependent aerosol within the meaning of the present invention, can change the aerosol's composition and, in particular, the aerosol's microbial load. For example, if a person's breath is understood as the source-dependent aerosol portion within the meaning of the present invention, then the particle size distribution of the breath is the corresponding source-dependent particle size distribution. The proportion parameter corresponds to the proportion of the source-dependent aerosol or aerosol portion within the total aerosol within the meaning of the present invention, and allows for the identification of a source-dependent particle size distribution associated with a source aerosol, e.g., a person's breath. The present invention allows for the characterization of a source-dependent particle size distribution corresponding to the source-dependent portion of (total) aerosol, thereby enabling improved aerosol analysis. The same applies to the aerosol measurement device according to the present invention.

[0009] The proportion parameter can be determined from a comparison of two size distributions of the aerosol, which may in particular involve the formation of a deviation and / or a quotient to facilitate the determination of the proportion parameter. At least one of the size distributions may be a theoretical size fraction and / or a size distribution determined by measured values. Preferably, one of the size distributions is a source-dependent size distribution.

[0010] Preferably, the proportion parameter is determined from a comparison of a parameter of at least one gaseous component of the aerosol with a source-dependent reference value, thereby making the method for determining the proportion parameter fast. The reference value may, for example, be user-defined and / or determined by prior measurement. In the case of prior measurement, the reference value is determined from a series of measurements performed over 24 hours. The gaseous component in the sense of the present invention may in particular be at least one substance from the following group: carbon oxides, nitrogen oxides, sulfur oxides, ozone, volatile organic compounds (VOCs).

[0011] Preferably, the parameter of at least one gas component is the concentration of the gas component in the aerosol, and / or the source-dependent reference value preferably corresponds to the source-dependent concentration of the gas component. Particularly preferably, to determine the proportion parameter, the carbon dioxide concentration in the aerosol is compared with a reference value in the range of 1% to 10%, in particular in the range of 3% to 5%, in particular a reference value of 4%, where the reference value of 4% (40,000 ppm) corresponds to the carbon dioxide concentration in human breath. Using the carbon dioxide concentration to determine the proportion parameter results in a particularly reliable method.

[0012] In particular, to determine the proportion of exhaled air in the aerosol as a proportion parameter, for example, the carbon dioxide concentration in the aerosol is divided by the carbon dioxide concentration in the exhaled air (4%).

[0013] To improve the accuracy of the method, the parameter and / or reference value of at least one gas component can be modified. This modification can include, for example, correcting for atmospheric influences, which can be assumed in a model and / or determined by continuous measurements over a certain period of time. In an advantageous embodiment of the invention, the correction value is determined by a series of measurements over a user-defined time interval, for example 24 hours, and in particular corresponds to the minimum value of the measurements. For example, atmospheric influences on the parameter and / or reference value can be corrected by performing a simple correction by subtracting the corresponding value. In particular, a value of approximately 0.05% can be subtracted from the determined carbon dioxide concentration in the aerosol and the carbon dioxide concentration in the exhaled breath. The correction can also include the influence of humidity, in particular relative humidity. Alternatively or additionally, the correction can include standardization.

[0014] Preferably, the method is interrupted if the rate parameter falls below a first user-defined value and / or if the rate parameter exceeds a second user-defined value, e.g., if the value of the rate parameter indicates that a source-dependent aerosol portion is absent and / or the composition of the aerosol has not changed.

[0015] The determined particle size distribution of the aerosol can be corrected to remove undesired background effects. In particular, standardization can be performed for the correction. Preferably, the correction corrects for the influence of humidity on the particle size distribution. Furthermore, the correction can also be performed based on a particle size distribution that is preferably determined theoretically and / or based on a prior measurement. In particular, the correction can be performed based on a particle size distribution determined at a user-defined concentration of carbon dioxide, for example, a carbon dioxide concentration of 400 ppm.

[0016] To speed up the method, the determined particle size distribution and / or source-dependent particle size distribution may be down-sampled and / or compressed.

[0017] The source-dependent particle size distribution can be determined by multiplying the particle size distribution of the aerosol by a proportion parameter, and preferably this is done for all particle size distribution values.

[0018] Preferably, an aerosol quality parameter corresponding to the aerosol quality is determined from at least a portion of the source-dependent particle size distribution in order to easily characterize the aerosol quality. Preferably, the quality parameter corresponds to air quality. More preferably, the determination of the quality parameter includes the sum of at least a portion of the source-dependent particle size distribution. In particular, the PM 2.5 The value of is a quality parameter in the sense of the present invention and corresponds to the proportion of aerosol particles with a size smaller than 2.5 μm contained in the source-dependent aerosol, e.g. exhaled breath. For determining the quality parameter, the source-dependent particle size distribution can be at least partially interpolated and / or integrated.

[0019] In a particularly preferred embodiment, the determination of the quality parameters includes a weighting that is dependent on, for example, the size of the aerosol particles, and / or on at least one parameter of the gas composition, and / or on the relative humidity of the aerosol.

[0020] Preferably, the determination of the proportion parameter and / or particle size distribution and / or source-dependent particle size distribution and / or quality parameter comprises the determination of individual values, respectively, and a statistical evaluation of the individual values ​​in order to improve the accuracy of the determined parameters, in particular for which a user-defined number of determinations are made over a user-defined time period and the individual values ​​are evaluated by averaging, in particular by moving averaging.

[0021] Regarding the device, the aerosol measurement device may comprise an electronic processing device designed to carry out the steps of the method according to the invention. Preferably, the aerosol measurement device comprises a gas measurement unit designed to determine the concentration of at least one gas component of the aerosol. To this end, the gas measurement unit comprises, in particular, at least one gas sensor. The gas measurement unit may be designed to detect at least one of the following substances and / or parameters, in particular, elements of the following groups: carbon oxides, nitrogen oxides, sulfur oxides, ozone, volatile organic compounds, and relative humidity.

[0022] The light beam of the aerosol measuring device comprises, in particular, polychromatic light and / or laser light. The direction of movement of the aerosol particles in the measuring cell, the direction of the light beam in the measuring cell, and the direction of the scattered light may be arranged in pairs so as to be perpendicular to each other. The aerosol measuring device preferably has an output device designed to output information, and the information on the source-dependent particle size distribution may, in particular, be assigned to a quality parameter. The output device may, in particular, comprise a display device.

[0023] In a further advantageous embodiment of the invention, the aerosol measuring device comprises a transport device for transporting the aerosol particles to the measuring cell, which transport device comprises, for example, a pump and / or a fan.

[0024] Other advantages and features will become apparent from the following description, which, in conjunction with the claims and the accompanying drawings, describes in detail an embodiment of the invention. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a schematic diagram of an aerosol measurement device within the aerosol to be measured. [Figure 2] FIG. 2 is a structural diagram of the aerosol measuring device of FIG. 1. [Figure 3] 1 is a flow chart of a method according to the present invention. [Figure 4]The first particle size distribution has a first source-dependent particle size distribution. [Figure 5] A second particle size distribution having a second source-dependent particle size distribution. [Figure 6] A third particle size distribution has a third source-dependent particle size distribution. DETAILED DESCRIPTION OF THE INVENTION

[0026] The schematic diagram in Figure 1 shows an aerosol 10 in a closed region 11, where the aerosol 10 includes solid and liquid aerosol particles 12 in a gas 13, e.g., air. The aerosol particles 11 may be, for example, water droplets, soot particles, abrasion particles, pollen, and / or other organic and chemical substances. A person is present within the region 11 as an aerosol source 14. Hereinafter, it is assumed that the aerosol 10 is primarily transformed within the region 11 by the exhaled breath of the person 14. Therefore, the aerosol 10 in the region 11 has a source-dependent aerosol portion 10a (here, exhaled breath) and a source-independent aerosol portion 10b.

[0027] In the region 11 of the aerosol 10, an aerosol measurement device 15 is arranged in the form of an aerosol spectrometer, which measures the size distribution C n particle size d p For this purpose, the aerosol particles 12 are sucked in via an inlet 16 of the aerosol measuring device 15 and a flow tube 17 by a downstream-arranged conveying device (not shown), which is designed as a pump. The flow tube 17 is arranged perpendicular to the plane of the drawing in the schematic diagram of the aerosol measuring device 15 according to FIG. 2.

[0028] The aerosol particles 12 are illuminated in the flow tube 17 perpendicular to their direction of flight by a collimated beam 18 of polychromatic light from a light source 19 and a lens 20. The resulting scattering process causes the aerosol particles 12 to emit scattered light 21, which is incident on a focusing lens 22 perpendicular to the direction of flight of the aerosol particles 12 and perpendicular to the direction of illumination of the light from the light source 19. The focusing lens 22 focuses the scattered light 21 onto an optoelectronic sensor 23, which converts the scattered light 21 into an electrical signal. An electronic processing unit 24 determines the particle size d of the aerosol particles 12. p The particle size distribution c is calculated from the electrical signal depending on n The spatial overlap of the light beam 18, the measured scattered light 21, and the detected portion of the aerosol particles 12 in the flow tube 17 determines the particle size distribution c n defines a virtual spatial measurement cell 25 in which

[0029] In the measurement, the luminosity of the scattered light 21 and the resulting electrical signal strength are also measures of the size of the aerosol particles 12, and accordingly the aerosol particles are assigned a diameter d p The measured particle size distribution c n is the particle size d p Since it depends on the formula:c n =f(d p ) applies.

[0030] Specified particle size distribution c n is the discrete particle size d p Typically, up to 256 channels are used. To improve accuracy, the particle size distribution between measurement points, c n The course of the particle size distribution c is locally interpolated using cubic splines during evaluation in the electronic processing unit 24, so that a continuous course is obtained. n is determined using 32 channel downsampling.

[0031] Specified particle size distribution c n From the reference particle size distribution c r is subtracted, but this standard particle size distribution c ris a model distribution, which corresponds to normal indoor air and has a carbon dioxide concentration of about 400 ppm.

[0032] The aerosol measuring device 15 comprises a gas measuring unit 26, which is designed as a gas sensor and measures the concentration k of carbon dioxide (CO2) in the aerosol. CO2 which corresponds to the volume fraction of CO in the aerosol 10 in the sense of the present invention. This value is transmitted to the electronic processing device 24.

[0033] In the following, the source-dependent particle size distribution c , which corresponds to the source-dependent aerosol portion 10a and is assigned to the exhaled breath of the person 14, is n An embodiment of the method according to the invention for determining the particle size distribution cn' is illustrated in accordance with Fig. 2. In the sense of the present invention, this particle size distribution cn' is called a source-dependent particle size distribution. This method allows, in particular, for determining the risk of infection in an area 11 due to the microbial load of the aerosol 10.

[0034] In the first step A of the present invention, the rate parameter f is determined. For this purpose, the CO2 concentration k in the aerosol 10 is measured by the gas sensor 26. CO2 is determined and transmitted to the electronic processing unit 24. CO2 From the above, the reference concentration k corresponds to the normal CO2 concentration in indoor air. ref In this example, the reference concentration k is reduced by approximately 0.05%. ref is determined by measuring the CO2 concentration of the aerosol 10 over a 24-hour period at one-hour intervals and forming a minimum value in this measurement. n ' corresponds to breathing air, so the reference concentration k ref is also subtracted from the CO2 concentration in the exhaled breath (here, about 4%). This results in a corrected CO2 concentration k CO2 ' and the corrected reference concentration k ref The quotient of these two values ​​gives the individual value f of the fraction parameter f of the breathing air 10a in the aerosol 10. i The individual values ​​of the rate parameter f are obtained. iis determined continuously over a period of 30 minutes, with the rate parameter f being formed as a moving average of the individual values.

[0035] In the next step B, the proportion factor f is queried as follows: if there is no person 14 in the area 11, the value of the proportion parameter f is 0, which causes the method to be interrupted C and restarted after a user-defined time interval.

[0036] If query B yields a value of the proportion parameter greater than 0, the method continues and determines the particle size distribution c of the aerosol 11. n is determined by the above-mentioned method D. The aerosol measurement device 15 measures the particle size distribution c of the aerosol 10 at a measurement cycle of once per minute. n The particle size distribution c used below is determined successively. n is formed as a moving average.

[0037] Next, the particle size distribution of aerosol 10, c n The source-dependent particle size distribution c is calculated by multiplying n ' is specified, which in this example is done for all measurement channels.

[0038] Source-dependent particle size distributionc n The specific E' is shown in Figures 4 to 6, and the particle size distribution c of aerosol 10 is shown on the left side of each figure. n is shown as an example, and the source-dependent particle size distribution c n ' is shown. Here, the particle size distribution c n , c n ' are the particle diameters d p The particle size distribution c is shown as a bar graph depending on the particle size distribution. n , c n ' each have seven measured values. The proportion coefficient is 0.28 in Figure 4, approximately 0.3 in Figure 5, and approximately 0.32 in Figure 6. From this, the proportion coefficient f is n From the particle size distribution c in Figure 6 nThis indicates that the proportion of breathable air 10a in the aerosol 10 is continuously increasing as the person 14 likely remains in the area 11 for a long time.

[0039] Source-dependent particle size distributionc n After identifying E', the source-dependent particle size distribution c n The identification of the quality parameter g assigned to the 'F' is carried out. This parameter is explained below.

[0040] Source-dependent particle size distributionc n The total number of aerosol particles g1 in ' is determined by the source-dependent particle size distribution c across all channels. n The source-dependent particle size distribution c is determined by summing n Since ' includes microbial contamination of aerosols10 by bacteria and viruses, for example, the total g1 is also used as an indicator of infection risk, and is therefore also called the "Germ Indicator."

[0041] In addition, the source-dependent aerosol portion 10a, i.e., the particle size d p The mass fraction of all aerosol particles 12 with PM 2.5 The parameter g2 is the source-dependent particle size distribution c n ', which is a further quality parameter g for fine dust pollution, especially for source-dependent aerosols 10a. Similarly, PM 2.5 The values ​​also provide information about the microbial load of the source-dependent aerosol fraction 10a, since they also include the microbial contamination of the air. Furthermore, the corrected PM 2.5 A parameter g3 is also specified.

[0042] For a comprehensive assessment of aerosol quality, the gas measurement unit 26 may further comprise components not shown in FIG. 1, such as a hygrometer for determining relative humidity, sensors for determining volatile organic compounds, ozone, nitrogen, sulfur oxides, and / or carbon monoxide. Furthermore, parameters that combine multiple values ​​of these characteristics may also be determined. For example, it is conceivable to determine an index that depends on the corrected PGV, the concentration of volatile organic compounds, CO2, and relative humidity as an indicator of infection risk.

[0043] Also, the source-dependent particle size distribution c n ', the number concentration of colony-forming particles (kbP / m 3 ) is also identified.

[0044] When the computer program according to the present invention is executed by the processing unit 24, the method steps described above are carried out sequentially.

Claims

1. The source-dependent particle size distribution (c ｎ '), comprising: The aerosol particles (12) of the aerosol (10) passing through a measurement cell (25) are irradiated with a light beam (18) in the measurement cell (25), the scattered light (21) is received by a sensor (23), and the spectral intensity of the scattered light signal (21) of the aerosol particles (12) is detected by spectroscopy, and a particle size distribution (c ｎ ) and determining a proportion parameter (f) corresponding to the proportion of the source-dependent aerosol portion (10a) in the aerosol (10) (A); and determining a particle size distribution (c) of the aerosol particles (12). ｎ ) is identified (D), and the ratio parameter (f) and the particle size distribution (c ｎ ) to the source-dependent particle size distribution (c ｎ Identify (E) determining said proportion parameter (f) from a comparison of a parameter (k) of at least one gaseous component (13) of said aerosol (10) with a source-dependent reference value (k ref ); the parameter (k) of at least one of the gaseous components (13) corresponds to the concentration of the gaseous component (13) in the aerosol (10) and / or the source-dependent reference value (k ref ) corresponds to the source-dependent concentration of the gaseous component (13), A method for identifying (A) the proportion parameter (f) by comparing the carbon dioxide concentration (k CO2 ) in the aerosol (10) with a range of 1% to 10%.

2. Two particle size distributions (c n ) are specified, and the ratio parameter (f) is a ratio of the two particle size distributions (c n ) of the aerosol (10). ｎ 2. The method of claim 1, wherein the marker is determined from a comparison of:

3. The parameter (k) and / or the reference value (k) of at least one of the gas components (13) ｒｅｆ 2. The method of claim 1, wherein:

4. 2. The method of claim 1, wherein the method is interrupted (C) if the percentage parameter (f) falls below a first user-defined value and / or if the percentage parameter (f) exceeds a second user-defined value.

5. The particle size distribution (c ｎ 2. The method of claim 1, wherein:

6. The source-dependent particle size distribution (c ｎ ') is the particle size distribution (c ｎ 2. The method of claim 1, wherein (E) is determined by multiplying (f) by the ratio parameter (f).

7. The source-dependent particle size distribution (c ｎ 2. The method of claim 1, wherein a quality parameter (g) of the aerosol (10) is determined (F) from at least a portion of the aerosol concentration (C) and the aerosol concentration (D) .

8. The determination (F) of the quality parameter (g) includes the source-dependent particle size distribution (c ｎ 8. The method of claim 7, wherein the sum of at least a portion of

9. The specification (F) of the quality parameter (g) includes the particle size (d ｐ 8. The method according to claim 7, characterized in that it comprises a weighting by the concentration (k) of at least one gaseous component (13) of the aerosol (10) and / or the relative humidity of the aerosol (10).

10. The proportion parameter (f) and / or the particle size distribution (c ｎ ) and / or the source-dependent particle size distribution (c ｎ 2. The method according to claim 1, characterized in that the determination (A) of the quality parameters (g) and / or the quality parameters (g) comprises the determination of individual values ​​and a statistical evaluation of the individual values, respectively.

11. The source-dependent particle size distribution (c ｎ An aerosol measurement device (15) for determining The aerosol particles (12) of the aerosol (10) in the measurement cell (25) are arranged so that the aerosol particles (12) can be irradiated with a light beam (18), the scattered light (21) of the aerosol particles (12) can be received by a sensor (23), and the spectral intensity of the scattered light signal (21) of the aerosol particles (12) can be detected by spectroscopy, so that the particle size distribution (c ｎ ) of the scattered light signal (21), a fraction parameter (f) corresponding to the fraction of the source-dependent aerosol fraction (10a) in the aerosol (10) can be determined, and a size distribution (c) of the aerosol particles (12) can be determined. ｎ ) can be specified, and the ratio parameter (f) and the particle size distribution (c ｎ ) to the source-dependent particle size distribution (c ｎ ') can be identified, determining said proportion parameter (f) from a comparison of a parameter (k) of at least one gaseous component (13) of said aerosol (10) with a source-dependent reference value (k ref ); the parameter (k) of at least one of the gaseous components (13) corresponds to the concentration of the gaseous component (13) in the aerosol (10) and / or the source-dependent reference value (k ref ) corresponds to the source-dependent concentration of the gaseous component (13), An aerosol measuring device, characterized in that (A) the carbon dioxide concentration (k CO2 ) in the aerosol (10) is compared with a range of 1% to 10% to determine the proportion parameter (f).

12. 12. The aerosol measurement device according to claim 11, characterized in that the aerosol measurement device (15) comprises an electronic processing device (24) designed to carry out the method according to any one of claims 1 to 10.

13. 12. Aerosol measurement device according to claim 11, characterized in that the gas measurement unit (26) is designed for detecting at least one of the following substances and / or parameters: carbon oxides, nitrogen oxides, sulfur oxides, ozone, volatile organic compounds, relative humidity.

14. 12. Aerosol measurement device according to claim 11, characterized in that the light beam (18) comprises polychromatic light.

15. The aerosol measurement device according to claim 11, characterized in that the direction of movement of the aerosol particles (12) in the measurement cell (25), the direction of the light beam (18) in the measurement cell (25), and the direction of the scattered light (21) are arranged in pairs so as to be perpendicular to each other.

16. 2. A computer program product for causing a computer or a corresponding computing unit to function as a means for carrying out the method according to claim 1 when the computer program is run on the computer or a corresponding computing unit.

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