Method and device for measuring surface area of aerosol in atmospheric environment

Abstract

The invention discloses a method and a device for measuring the surface area of aerosol in an atmospheric environment. According to the invention, a drying tube, a first optical particle spectrometer and a second optical particle spectrometer are adopted to obtain dried and non-dried particle size distribution of aerosol; the second total scattering intensity is obtained by directly adopting the scattering intensity distribution spectrum obtained by calculating the wet particle size aerosol, the first total scattering intensity is obtained by combining the dry particle size aerosol with the scattering intensity distribution spectrum obtained by calculating the moisture absorption growth model, and the initial value of the moisture absorption growth factor is changed by utilizing a gradient descent method; performing inversion until the first total scattering intensity is equal to the second total scattering intensity to obtain an aerosol moisture absorption growth factor; the instrument cost is remarkably reduced, a humidifying unit is not needed to control the humidity of instrument equipment, and the maintenance difficulty is remarkably reduced; according to the method, the moisture absorption growth factor is obtained through inversion by using the measured particle size spectrum distribution of the whole aerosol, the surface area of the aerosol is calculated according to the particle size after moisture absorption growth and the dry concentration under the environment humidity, and the error is smaller.

Description

TECHNICAL FIELD

[0001] The present application relates to atmospheric aerosol measurement technology, and in particular to a method for measuring the surface area of atmospheric aerosols and a measuring device thereof. BACKGROUND

[0002] Atmospheric aerosols have unique environmental, health, and climate effects. The surface area of aerosols significantly affects their optical properties, such as scattering and absorption capacity, changes cloud macro and micro characteristics, and indirectly affects the Earth's radiation balance. At the same time, it can significantly reduce atmospheric visibility and promote the transformation and secondary generation of pollutants; the surface area of aerosols provides adsorption sites for pollutants, and many harmful substances such as heavy metals and organic matter will adhere to the surface of aerosols. A larger surface area means that more pollutants can be adsorbed and transported, increasing the risk of human exposure to harmful substances. Accurate acquisition of the surface area of atmospheric aerosols helps to improve air quality models, making them more accurately simulate the physical and chemical processes, transport, and transformation of aerosols, and improve the ability to predict and assess air pollution. It helps to better understand the interaction between aerosols and the climate system, improve the simulation accuracy and reliability of climate models, and provide scientific basis for the prediction and response of climate change. However, current methods for obtaining the surface area of atmospheric aerosols mostly rely on measuring their chemical composition and aerosol size distribution characteristics, which have high measurement time resolution, complex process, and high cost, limiting their widespread application in atmospheric aerosol water content. SUMMARY

[0003] To solve the above problems of the prior art, the present application provides a method for measuring the surface area of atmospheric aerosols and a measuring device thereof, which uses the measurement data of two optical particle spectrometers (OPS) to obtain the surface area of aerosols, has high measurement time resolution, simple equipment, easy maintenance, and can meet the needs of aircraft observation and vertical observation.

[0004] One object of the present application is to provide a method for measuring the surface area of atmospheric aerosols.

[0005] The method for measuring the surface area of atmospheric aerosols of the present application comprises the following steps:

[0006] 1) Measuring device:

[0007] After the environmental aerosol is sampled from the sampling port, it is divided into two paths. One path passes through a drying tube, and a first optical particle spectrometer OPS1 is used to measure the particle size distribution PNSD1 of the dried aerosol, and a first temperature and humidity probe is used to measure the temperature T1 of the dried aerosol and the relative humidity RH1 of the dried aerosol. The other path is not dried, and a second optical particle spectrometer OPS2 is used to measure the particle size distribution PNSD2 of the undried aerosol. Meanwhile, a second temperature and humidity probe and a third temperature and humidity probe are used to measure the inlet temperature T2 of the undried aerosol, the relative humidity RH2 of the inlet of the undried aerosol, the outlet temperature T3 of the undried aerosol, and the relative humidity RH3 of the outlet of the undried aerosol before and after the second optical particle spectrometer OPS2.

[0008] 2) Calculate the equivalent relative humidity:

[0009] The inlet water vapor content e2 of the second optical particle spectrometer OPS2 is calculated using the inlet temperature T2 of the undried aerosol and the relative humidity RH2 of the inlet of the undried aerosol:

[0010]

[0011] The outlet water vapor content e3 of the second optical particle spectrometer OPS2 is calculated using the outlet temperature T3 of the undried aerosol and the relative humidity RH3 of the outlet of the undried aerosol:

[0012]

[0013] The equivalent water content e0 in the second optical particle spectrometer OPS2 is obtained as:

[0014]

[0015] The equivalent temperature T0 in the second optical particle spectrometer OPS2 is:

[0016]

[0017] The equivalent relative humidity RH0 of the aerosol in the second optical particle spectrometer OPS2 is calculated using the equivalent temperature T0 and the equivalent water content e0 in the second optical particle spectrometer OPS2:

[0018]

[0019] 3) Inverse the hygroscopic growth factor:

[0020] Based on the particle size distribution PNSD1 of the dried aerosol and the particle size distribution PNSD2 of the undried aerosol, the equivalent relative humidity RH0 of the aerosol in the second optical particle spectrometer OPS2, and the commonly used complex refractive index RI0 of the aerosol, the hygroscopic growth factor κ of the aerosol is calculated as follows:

[0021] (1) The second total scattering intensity S2 is obtained by directly using the scattering intensity distribution spectrum calculated from wet particle size aerosol:

[0022] a. Particle size distribution of undried aerosols. PNSD2 represents different particle sizes Dp1, Dp2, ... Dp n The undried concentrations of the aerosols were N 21 N 22 …N 2n n is the number of different particle size types;

[0023] b. Using the Mie scattering model, the commonly used complex refractive index combinations for calculating particle size and aerosols are (Dp1,RI0), (Dp2,RI0)...(Dp... n The scattering intensities under RI0) are S 21 ,S 22 …S 2n The corresponding scattering intensity distribution spectrum S′ is obtained directly from wet particle size aerosol calculations. 2i for:

[0024] c. Based on the scattering intensity distribution spectrum obtained directly from wet particle size aerosols, the corresponding second total scattering intensity S2 is:

[0025]

[0026] (2) The first total scattering intensity S1 is obtained by calculating the scattering intensity distribution spectrum of dry particle size aerosol combined with the hygroscopic growth model:

[0027] a. An initial value for the hygroscopic growth factor is arbitrarily set. The particle size distribution after aerosol drying, PNSD1, represents different particle sizes Dp1, Dp2, ... Dp. n The concentrations of the dried aerosols were N 11 N 12 …N 1n ;

[0028] b. Using Capacola The theoretical formula calculates the aerosol particle sizes Dp1, Dp2, ... Dp under the conditions of relative humidity RH1 to equivalent relative humidity RH0 and equivalent temperature T0 after drying. n Particle size Dp after hygroscopic growth at equivalent relative humidity 11 ,Dp 12 ,…Dp 1n ;

[0029] c. Calculate the particle size Dp of the corresponding aerosol after the i-th wet growth using the volume-weighted average method. 1i aerosol complex refractive index RI 1i :

[0030] where i = 1, 2…n

[0031] where, RI water is the complex refractive index of water;

[0032] d. Calculate the particle size after wet growth and the complex refractive index combination of the aerosol (Dp 11 , RI 11 ), (Dp 12 , RI 12 )…(Dp 1n , RI 1n ) using the Mie scattering model, and the scattering intensity is S 11 , S 12 …S 1n respectively; the corresponding scattering intensity distribution spectrum S′ 1i calculated by the dry particle size aerosol combined with the hygroscopic growth model is:

[0033] e. The corresponding first total scattering intensity S1 is obtained according to the scattering intensity distribution spectrum calculated by the dry particle size aerosol combined with the hygroscopic growth model:

[0034]

[0035] (3) The first total scattering intensity S1 and the second total scattering intensity S2 are essentially the same, which are the total scattering intensity of the wet particle size aerosol. The initial value of the hygroscopic growth factor is changed using the gradient descent method until the first total scattering intensity S1 and the second total scattering intensity S2 are equal or the deviation between them is less than a set threshold, so that the value κ0 of the hygroscopic growth factor when meeting this condition is the finally obtained aerosol hygroscopic growth factor;

[0036] 4) Calculate the particle size after hygroscopic growth under the ambient humidity of the gas environment:

[0037] An environmental humidity is measured by a temperature and humidity probe, and the aerosol hygroscopic growth factor obtained by step 3) is used to calculate the particle size of the aerosol after hygroscopic growth under the measured ambient humidity according to the kappa-Kohlrausch (κ- ) theoretical formula: n 31 32 3n

[0038]

[0039] where RH4 is the ambient humidity, and D 3i ​​​​Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. s / a Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. water Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. w Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water.

[0040] 5) Calculate the surface area of the aerosol:

[0041] Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. 11 Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. 12 Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. 1n Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water.

[0042] Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water.

[0043]

[0044] Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water.

[0045] Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water.

[0046] Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. ) is:

[0047]

[0048] Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. 1i Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. i Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. s / a Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. water Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. w Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water.

[0049] Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. -6 Dpi is the i-th particle diameter after hygroscopic growth under ambient humidity, κ is the hygroscopic growth factor of aerosol, σ is the surface tension of aerosol, R is the Avogadro constant, M is the molar mass of water, T0 is the equivalent temperature, and ρ is the density of water. -5 .

[0050] Another object of the present application is to provide a device for measuring the surface area of atmospheric aerosol.

[0051] The atmospheric environmental aerosol surface area measuring device of the present application comprises a drying tube, first and second optical particle spectrometers and first to third temperature and humidity probes; wherein the inlet of the environmental aerosol is connected to the inlet of the drying tube and the gas inlet of the second optical particle spectrometer through pipelines respectively; the outlet of the drying tube is connected to the gas inlet of the first optical particle spectrometer; the gas outlet of the first optical particle spectrometer is provided with the first temperature and humidity probe; the gas inlets and outlets of the second optical particle spectrometer are provided with the second and third temperature and humidity probes respectively; after the sampling of the environmental aerosol, one of the two routes passes through the drying tube, and the particle size distribution of the dried aerosol is measured by the first optical particle spectrometer, and the temperature and relative humidity of the dried aerosol are measured by the first temperature and humidity probe; the other route is not dried, and the particle size distribution of the undried aerosol is measured by the second optical particle spectrometer, and the inlet temperature and relative humidity of the undried route and the outlet temperature and relative humidity of the undried route are measured by the second and third temperature and humidity probes respectively before and after the second optical particle spectrometer; the equivalent relative humidity is calculated according to the temperature and humidity of the gas inlets and outlets of the second optical particle spectrometer; the particle size of the aerosol after hygroscopic growth under the equivalent relative humidity is calculated by using the kappa-Koehler theoretical formula, the first total scattering intensity is obtained by combining the dry particle size aerosol with the scattering intensity distribution spectrum calculated by the hygroscopic growth model, and the second total scattering intensity is directly calculated by using the wet particle size aerosol; the initial value of the hygroscopic growth factor is changed by using the gradient descent method until the first total scattering intensity and the second total scattering intensity are equal or the deviation between them is less than a set threshold, so as to meet the condition, and the value of the hygroscopic growth factor is the finally obtained aerosol hygroscopic growth factor; the particle size after hygroscopic growth under the environmental humidity is calculated by using the kappa-Koehler theoretical formula according to the aerosol hygroscopic growth factor, and the surface area of the aerosol is calculated according to the particle size after hygroscopic growth under the environmental humidity and the dry concentration.

[0052] The present application adopts the drying tube and the first and second optical particle spectrometers to obtain the particle size distribution of the dried and undried aerosols, and the hygroscopic growth factor is inversely obtained by using the measured whole aerosol particle size spectrum distribution; the present application does not use the differential electrical mobility analyzer, so the instrument cost is significantly reduced; and the humidifying unit is not needed to control the humidity of the instrument equipment, so the maintenance difficulty is significantly reduced; in the inverse method of the present application, the hygroscopic growth factor is inversely obtained by using the measured whole aerosol particle size spectrum distribution, and the surface area of the aerosol is calculated according to the particle size after hygroscopic growth under the environmental humidity and the dry concentration, so the error is smaller. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 It is a schematic diagram of the atmospheric environmental aerosol surface area measuring device of the present application;

[0054] Figure 2Flow chart of the atmospheric ambient aerosol surface area measurement method of the present application. DETAILED DESCRIPTION

[0055] The present application will be further described in connection with the accompanying drawings and specific embodiments.

[0056] The atmospheric ambient aerosol surface area measurement method of the present embodiment, as shown in Figure 2 includes the following steps:

[0057] 1) Measurement device:

[0058] As shown in Figure 1 , after sampling the ambient aerosol from the sampling port, it is divided into two paths. One path passes through the drying tube, and the first optical particle spectrometer OPS1 is used to measure the particle size distribution PNSD1 of the dried aerosol, and the first temperature and humidity probe is used to measure the temperature T1 and the relative humidity RH1 of the dried aerosol. The other path is not dried, and the second optical particle spectrometer OPS2 is used to measure the particle size distribution PNSD2 of the undried aerosol, and the second and third temperature and humidity probes are used to measure the inlet temperature T2 and the relative humidity RH2 of the undried inlet, and the outlet temperature T3 and the relative humidity RH3 of the undried outlet before and after the second optical particle spectrometer OPS2;

[0059] 2) Calculate the equivalent relative humidity:

[0060] Using the undried inlet temperature T2 and the undried inlet relative humidity RH2, the water vapor content e2 of the inlet of the second optical particle spectrometer OPS2 is calculated as:

[0061]

[0062] Using the undried outlet temperature T3 and the undried outlet relative humidity RH3, the water vapor content e3 of the outlet of the second optical particle spectrometer OPS2 is calculated as:

[0063]

[0064] The equivalent water content e0 in the second optical particle spectrometer OPS2 is obtained as:

[0065]

[0066] The equivalent temperature T0 in the second optical particle spectrometer OPS2 is:

[0067]

[0068] The equivalent relative humidity RH0 of the aerosol in the second optical particle spectrometer OPS2 is calculated using the equivalent temperature T0 and the equivalent water content e0 in the second optical particle spectrometer OPS2:

[0069]

[0070] 3) Hygroscopic growth factor K:

[0071] (1) The second total scattering intensity S2 is obtained from the scattering intensity distribution spectrum calculated directly using the wet particle diameter aerosol:

[0072] a. The particle size distribution PNSD2 of the aerosol before drying represents the concentrations N n , N 21 , …, N 22 of the aerosol at different particle diameters Dp1, Dp2, …, Dp 2n , and n is the number of different particle size categories;

[0073] b. The scattering intensity S n , S 21 , …, S 22 of the aerosol at different particle diameters and the commonly used complex refractive index combination (Dp1, RI0), (Dp2, RI0), …, (Dp 2n , RI0) is calculated using the Mie scattering model, and RI0 = 1.46; and the scattering intensity distribution spectrum S′ 2i calculated directly using the wet particle diameter aerosol is:

[0074] c. The corresponding second total scattering intensity S2 is obtained from the scattering intensity distribution spectrum calculated directly using the wet particle diameter aerosol:

[0075]

[0076] (2) The first total scattering intensity S1 is obtained from the scattering intensity distribution spectrum calculated using the dry particle diameter aerosol combined with the hygroscopic growth model:

[0077] a. An initial value of the hygroscopic growth factor is arbitrarily set, and the particle size distribution PNSD1 of the aerosol after drying represents the concentrations N n , N 11 , …, N 12 of the aerosol at different particle diameters Dp1, Dp2, …, Dp 1n ;

[0078] b. The scattering intensity S Theoretical formula, under the conditions of relative humidity RH1 after drying to equivalent relative humidity RH0 and equivalent temperature T0, the particle size Dp of aerosol after hygroscopic growth from different particle sizes Dp1, Dp2, … Dpn is calculated n 11 12 1n

[0079]

[0080] 1i i s / a water w

[0081] c. Using the method of volume-weighted average, the complex refractive index RI of the aerosol corresponding to the particle size Dp of the i-th particle size of the aerosol after hygroscopic growth at the equivalent relative humidity is calculated 1i 1i

[0082]

[0083] water

[0084] d. Using the Mie scattering model, the scattering intensity of the combination of the particle size and the complex refractive index of the aerosol after hygroscopic growth is calculated, respectively (Dp, RI), (Dp, RI) … (Dp, RI) under the condition of (Dp, RI), (Dp, RI) … (Dp, RI) 11 11 12 12 1n 1n 11 12 1n 1i

[0085]

[0086] e. According to the scattering intensity distribution spectrum calculated by the dry particle size aerosol combined with the hygroscopic growth model, the corresponding first total scattering intensity S1 is obtained as follows: ​​​​​​​​​​​​​​​​​​​​​​​​​

[0087]

[0088] (3) The first total scattering intensity S1 and the second total scattering intensity S2 are essentially the same, and are the total scattering intensity of the wet particle size aerosol. The initial value of the hygroscopic growth factor is changed by using the gradient descent method until the first total scattering intensity S1 and the second total scattering intensity S2 are equal or the deviation of the two is less than 10 -5 , to meet this condition, the value of the hygroscopic growth factor κ0 is the final inversion of the aerosol hygroscopic growth factor;

[0089] 4) Calculate the particle size of the aerosol after hygroscopic growth:

[0090] An environmental humidity is measured by a temperature and humidity probe, and the aerosol hygroscopic growth factor obtained by step 3) is used to calculate the particle size of the aerosol after hygroscopic growth from different particle sizes Dp1, Dp2, … Dpn to the environmental humidity according to the kappa-Kohlrausch theoretical formula: n 31 32 3n

[0091]

[0092] where RH4 is the environmental humidity, D 3i is the particle size of the i-th particle size after hygroscopic growth at the environmental humidity, κ is the hygroscopic growth factor of the aerosol, σ s / a is the surface tension of the aerosol, R is the Avogadro constant, M water is the molar mass of water, T0 is the equivalent temperature, and ρ w is the density of water.

[0093] 5) Calculate the surface area of the aerosol:

[0094] According to the particle size after hygroscopic growth at the environmental humidity and the dry concentration N 11 , N 12 … N 1n , the surface

[0095] product W of the aerosol is calculated:

[0096]

[0097] where i = 1, …, n.

[0098] ​​​​Finally, it is to be understood that the embodiments are for purposes of illustration only and that various changes and modifications can be made by those skilled in the art without departing from the scope of the application as disclosed in the specification and appended claims. Therefore, the scope of the application is not to be limited to the embodiments disclosed but is to be accorded the full scope permissible by the appended claims.

Claims

1. A method of measuring the surface area of an atmospheric aerosol, characterized in that, The measurement method comprises the following steps: 1) Measurement device: After sampling the ambient aerosol from the sampling port, it is divided into two paths. One path passes through the drying tube, and the particle size distribution PNSD1 of the dried aerosol is measured by using the first optical particle spectrometer. The temperature T1 and the relative humidity RH1 of the dried aerosol are measured. The other path is not dried, and the particle size distribution PNSD2 of the undried aerosol is directly measured by using the second optical particle spectrometer. The inlet temperature T2 and the relative humidity RH2 of the undried aerosol before the second optical particle spectrometer and the outlet temperature T3 and the relative humidity RH3 of the undried aerosol after the second optical particle spectrometer are measured. 2) Calculation of equivalent relative humidity: The water vapor content of the inlet and outlet of the second optical particle spectrometer is calculated by using the inlet and outlet temperature and relative humidity of the undried aerosol, and the equivalent water content and equivalent temperature in the second optical particle spectrometer are obtained. Then, the equivalent relative humidity of the aerosol in the second optical particle spectrometer is calculated. 3) Hygroscopic growth factor K: (1) The second total scattering intensity S2 is obtained by directly using the scattering intensity distribution spectrum calculated by the wet particle size aerosol. (2) The first total scattering intensity S1 is obtained by the scattering intensity distribution spectrum calculated by the dry particle size aerosol combined with the hygroscopic growth model. (3) The initial value of the hygroscopic growth factor is changed by using the gradient descent method until the first total scattering intensity S1 and the second total scattering intensity S2 are equal or the deviation between them is less than a set threshold. The value of the hygroscopic growth factor when the condition is met is the finally obtained aerosol hygroscopic growth factor. 4) Calculation of the particle size after hygroscopic growth under the atmospheric humidity: Using the aerosol hygroscopic growth factor obtained by inverting step 3), the ambient humidity at which the aerosol absorbs moisture and grows from different particle sizes Dp1, Dp2,... Dp n to the ambient humidity is calculated according to the kappa-Kola theory formula 31 , D 32 , …D 3n ; 5) Calculation of the surface area of the aerosol: The particle diameter after hygroscopic growth under an environmental humidity and the concentration N of the dry state 11 ,N 12 …N 1n The surface area W of the aerosol is calculated.

2. The measurement method of claim 1, wherein, In step 2), the equivalent relative humidity is calculated, comprising the following steps: The water vapor content e2 of the inlet of the second optical particle spectrometer is calculated by using the inlet temperature T2 and the relative humidity RH2 of the undried aerosol: The water vapor content e3 of the outlet of the second optical particle spectrometer is calculated by using the outlet temperature T3 and the relative humidity RH3 of the undried aerosol: The equivalent water content e0 in the second optical particle spectrometer is obtained: The equivalent temperature T0 in the second optical particle spectrometer is: The equivalent relative humidity RH0 of the aerosol in the second optical particle spectrometer is calculated by using the equivalent temperature T0 and the equivalent water content e0 in the second optical particle spectrometer:

3. The measurement method of claim 1, wherein, In step 3)(1), the second total scattering intensity S2 is obtained by directly using the scattering intensity distribution spectrum calculated by the wet particle size aerosol, comprising the following steps: a. The aerosol non-dried particle size distribution PNSD2 represents different particle sizes Dp1, Dp2,... Dpn n The non-dried concentration of the lower aerosol is N 21 ,N 22 …N 2n n is the number of different particle size classes; b.Using Mie scattering model to calculate particle size and commonly used complex refractive index combination of aerosol is (Dp1, RI0), (Dp2, RI0)…(Dp n ,RI0) under the scattering intensity of S 21 ,S 22 …S 2n ; the corresponding direct use of wet particle size aerosol calculated scattering intensity distribution spectrum S′ 2i : c. The corresponding second total scattering intensity S2 is obtained according to the scattering intensity distribution spectrum calculated by the wet particle size aerosol:

4. The measurement method of claim 1, wherein, In step 3)(2), the first total scattering intensity S1 is obtained by the scattering intensity distribution spectrum calculated by the dry particle size aerosol combined with the hygroscopic growth model, comprising the following steps: a. An initial value of a hygroscopic growth factor is arbitrarily set, and the particle size distribution PNSD1 of the dried aerosol indicates different particle sizes Dp1, Dp2,... Dp n The concentrations of the dried aerosol are N 11 ,N 12 …N 1n ; b. Using the kappa-cola theory formula, the particle size Dp of the aerosol after the moisture absorption growth under the conditions of the relative humidity RH1 after drying to the equivalent relative humidity RH0 and the equivalent temperature T0 is calculated from different particle sizes Dp1, Dp2, … Dp n to the equivalent relative humidity 11 ,Dp 12 ,…Dp 1n ; c. The complex refractive index R1 of the aerosol corresponding to the particle size Dp of the i-th wet-grown aerosol is calculated using the volume-weighted average method 1i 1i :​ where i = 1, 2...n wherein R1 water is the complex refractive index of water; d. The scattering intensity of the aerosol with the wet growth particle size and the complex refractive index combination (Dp 11 ,RI 11 ), (Dp 12 ,RI 12 )…(Dp 1n ,RI 1n ) is S 11 , S 12 …S 1n , respectively. The corresponding scattering intensity distribution spectrum S′ 1i calculated by the dry particle size aerosol combined with the hygroscopic growth model is: e. The corresponding first total scattering intensity S1 is obtained according to the scattering intensity distribution spectrum calculated by the dry particle size aerosol combined with the hygroscopic growth model:

5. The method of claim 1, wherein, In step 3)(2), the initial value of the hygroscopic growth factor is 0.01-1.

6. The measurement method of claim 1, wherein, In (3) of step 3), the threshold is set to 10 -6 ~ 10 -5 .

7. The method of measuring of claim 1, wherein, In step 4), the particle size after hygroscopic growth under ambient humidity is calculated according to the following formula: where RH4 is the environmental humidity, D 3i is the particle diameter of the i-th particle diameter after hygroscopic growth under the environmental humidity, K is the hygroscopic growth factor of the aerosol, σ s / a is the surface tension of the aerosol, R is the Avogadro constant, M water is the molar mass of water, T0 is the equivalent temperature, p w is the density of water, Dp i is the i-th particle diameter.

8. The method of measuring of claim 1, wherein, In step 5), the surface area W of the aerosol is calculated according to the following formula: where i = 1,..., n, D 3i Dp,i is the dry concentration of the i-th particle size, Dp 1i Dp,i is the dry concentration of the i-th particle size, Dp i Dp,i is the i-th particle size.

9. A device for measuring an aerosol hygroscopic growth factor based on double OPS, characterized by, The measuring device comprises a drying tube, first and second optical particle spectrometers, and first to third temperature and humidity probes; wherein the inlet of the ambient aerosol is connected to the inlet of the drying tube and the gas inlet of the second optical particle spectrometer through pipelines respectively; the outlet of the drying tube is connected to the gas inlet of the first optical particle spectrometer; the gas outlet of the first optical particle spectrometer is provided with the first temperature and humidity probe; the gas inlets and outlets of the second optical particle spectrometer are provided with the second and third temperature and humidity probes respectively; after sampling, the ambient aerosol is divided into two paths, one of which passes through the drying tube, and the particle size distribution of the dried aerosol is measured by the first optical particle spectrometer, and the temperature and relative humidity of the dried aerosol are measured by the first temperature and humidity probe; the other path is not dried, and the particle size distribution of the undried aerosol is measured by the second optical particle spectrometer, and the inlet temperature and relative humidity of the undried aerosol and the outlet temperature and relative humidity of the undried aerosol are measured by the second and third temperature and humidity probes respectively before and after the second optical particle spectrometer; the equivalent relative humidity is calculated according to the temperatures and humidities of the gas inlets and outlets of the second optical particle spectrometer; the particle size of the aerosol after hygroscopic growth under the equivalent relative humidity is calculated by using the kappa-Kohlrausch theory formula, the first total scattering intensity is obtained by combining the scattering intensity distribution spectrum of the dry particle aerosol with the hygroscopic growth model, and the second total scattering intensity is directly obtained by using the wet particle aerosol; the initial value of the hygroscopic growth factor is changed by using the gradient descent method until the first total scattering intensity and the second total scattering intensity are equal or the deviation between them is less than a set threshold, so as to meet the condition, and the value of the hygroscopic growth factor is the finally obtained aerosol hygroscopic growth factor; the particle size after hygroscopic growth under ambient humidity is calculated by using the kappa-Kohlrausch theory formula according to the finally obtained aerosol hygroscopic growth factor, and the surface area of the aerosol is calculated according to the particle size after hygroscopic growth under ambient humidity and the concentration after drying.

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