A free radical activity measurement system and its application method

Abstract

This invention discloses a free radical activity measurement system and its application method, relating to the field of atmospheric environmental monitoring equipment technology. The measurement system includes a reaction module, an optical path and light intensity detection module, an air intake module, an air exhaust module, and a free radical detection module. The reaction module includes a main reaction tube and an air intake end and a sampling interface connected to the main reaction tube. The optical path and light intensity detection module emits photolysis laser and absorption laser into the main reaction tube. The air intake module introduces gas into the main reaction tube through the air intake end. The free radical detection module acquires free radicals in the main reaction tube through the sampling interface and measures the fluorescence photon signal of the free radicals. The application method involves performing a single-exponential fitting on the attenuation curve of the fluorescence photon signal to obtain the free radical activity value. This invention can monitor and dynamically adjust the concentration of free radical precursors in real time, achieving accurate measurement of free radical activity under complex external environments, with advantages of high sensitivity and low detection limit.

Description

Technical Field

[0001] This invention relates to the field of atmospheric environment monitoring equipment technology, and in particular to a free radical activity measurement system and its application method. Background Technology

[0002] Secondary air pollution, characterized by ozone, nitrates, sulfates, and secondary organic aerosols, is rapidly increasing and spreading, becoming one of the bottlenecks restricting the continuous improvement of air quality. In atmospheric photochemical processes, free radicals possess extremely strong atmospheric oxidizing capabilities, reacting with the vast majority of trace substances and promoting the transformation of primary pollutants emitted by anthropogenic activities into secondary pollutants. This is a driving force behind the formation of complex atmospheric pollution; photochemical smog, haze, and acid rain are all manifestations of complex atmospheric pollution under different spatiotemporal conditions. To further study atmospheric oxidizing capabilities and improve our understanding of the causes of air pollution processes, we need to know not only the concentration of free radicals but also their activity, which is a crucial parameter.

[0003] Free radical activity can generally be calculated using the following steps: first, the concentration of compounds reacting with free radicals is measured; second, the bimolecular reaction rate constant between the compounds and free radicals is measured in the laboratory; finally, the free radical activity is obtained by adding the products of the concentrations of various compounds and their corresponding bimolecular reaction rate constants. Because there are numerous types of compounds in the atmosphere that can react with free radicals, current technology cannot measure the concentration of all reactive species in the atmosphere. Furthermore, some bimolecular reaction rate constants cannot be measured. These uncertainties lead to significant deviations in the calculation of free radical activity, greatly affecting the prevention and control of secondary air pollution.

[0004] Therefore, it is necessary to develop a system and method that can directly measure free radical activity to obtain the free radical activity in the ambient atmosphere in real time, so as to accurately quantify the atmospheric oxidation capacity. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a free radical activity measurement system that can directly measure the free radical activity in sample gas, i.e., ambient atmosphere, in real time online.

[0006] To achieve the above objectives, the present invention adopts the following technical solution, including:

[0007] A free radical activity measurement system includes: a reaction module, an optical path and light intensity detection module, an air inlet module, an air outlet module, and a free radical detection module;

[0008] The reaction module includes: a main reaction tube, and an air inlet and a sampling interface respectively connected to the main reaction tube;

[0009] The optical path and light intensity detection module includes: a first light source for emitting a photolysis laser into the main reaction tube; the photolysis laser is used to photolyze free radical precursors to generate free radicals;

[0010] The gas inlet module is connected to the gas inlet end and is used to introduce gas into the main reaction tube; the gas inlet module introduces sample gas containing free radical precursors into the main reaction tube;

[0011] The free radical detection module is connected to the sampling interface. It acquires free radicals in the main reaction tube through the sampling interface and emits a detection laser to excite the free radicals and generate fluorescence. The free radical detection module is used to measure the fluorescence photon signal of the free radicals.

[0012] Preferably, the optical path and light intensity detection module further includes: a second light source and a second detector for emitting absorbed laser light into the main reaction tube; the absorbed laser light is absorbed by the free radical precursor in the main reaction tube and then passes through the main reaction tube to the second detector, and the second detector is used to detect the emitted light intensity of the absorbed laser light after passing through the main reaction tube.

[0013] Preferably, the main reaction tube has an irradiation window at each end, namely a first irradiation window and a second irradiation window, for sealing the main reaction tube and transmitting light. A first hollow spherical reflector is provided in the main reaction tube near the first irradiation window, and a second hollow spherical reflector is provided near the second irradiation window. The first and second hollow spherical reflectors are hollow spherical reflectors with a central through hole in the middle and an edge through hole at the edge.

[0014] The photolysis laser emitted by the first light source is collimated and expanded by the beam expander, and then enters the main reaction tube through the center of the first irradiation window and the middle through hole of the first hollow spherical reflector in sequence. It passes through the center of the main reaction tube and exits through the middle through hole of the second hollow spherical reflector and the center of the second irradiation window in sequence.

[0015] The absorbed laser emitted by the second light source enters the main reaction tube through the edge of the first illumination window and the edge through-hole of the first hollow spherical reflector in sequence. After passing through the main reaction tube, it is projected onto the second hollow spherical reflector. After being reflected multiple times between the second hollow spherical reflector and the first hollow spherical reflector, it is then projected out through the edge through-hole of the first hollow spherical reflector and the edge of the second illumination window and projects onto the second detector.

[0016] In this process, the photolysis laser and the absorption laser in the main reaction tube do not interfere with each other.

[0017] Preferably, the free radical detection module includes: a detection cavity, a detection laser source, a detection laser beam expander, and a detection laser detector;

[0018] The free radicals in the main reaction tube enter the detection cavity through the sampling interface. The detection laser source is used to emit a detection laser. After being expanded by the detection laser beam expander, the detection laser enters the detection cavity and excites the free radicals in the detection cavity to generate fluorescence. Subsequently, the detection laser is emitted from the detection cavity and irradiates the detection laser detector. The detection laser detector is used to collect the emitted energy of the detection laser. The detection cavity is equipped with a device for detecting fluorescent photon signals.

[0019] Preferably, the air inlet includes a main air inlet channel; the air outlet includes a main air outlet channel;

[0020] The main air intake channel is vertically connected to the upper sidewall of the main reaction tube near one end face; the main air outlet channel is vertically connected to the upper sidewall of the main reaction tube near the other end face; the sampling interface is connected to the lower sidewall of the main reaction tube near the main air outlet channel.

[0021] The sampling interface is conical, with the cone opening being the sampling nozzle that extends into the main reaction tube, and the bottom of the cone being connected to the free radical detection module.

[0022] The main outlet channel is connected to the air pump; the main outlet channel is also provided with an insertion port, which is connected to a temperature and humidity detection module for real-time detection of the temperature and humidity of the gas in the main reaction tube.

[0023] Preferably, the intake module further includes a first intake component for providing free radical precursors;

[0024] The first air intake assembly includes: a free radical precursor synthesis gas cylinder, a free radical precursor generator, a second zero-air cylinder, and a humidifier cylinder;

[0025] The output pipe of the free radical precursor synthesis gas cylinder is connected to the input end of the free radical precursor generator via a mass flow meter; the free radical precursor generator is equipped with an adjustable light source for photolysis of the free radical precursor synthesis gas to generate free radical precursors.

[0026] The output pipe of the second zero-air bottle is connected to two parallel branch pipes through two mass flow meters. One of the branch pipes is equipped with a humidifier bottle for generating water vapor. After the two branch pipes merge, they are first connected to the output end of the free radical precursor generator, and then connected to the air inlet. The water vapor and free radical precursor are combined into one line and enter the main reaction pipe through the air inlet.

[0027] Preferably, the intake module further includes a second intake assembly for providing dilution gas / zero air;

[0028] The second air intake assembly includes: a third zero-air cylinder and a dilution gas cylinder; the output pipe of the third zero-air cylinder is connected to the air intake end through a mass flow meter, and the zero air in the third zero-air cylinder enters the main reaction tube through the air intake end; the output pipe of the dilution gas cylinder is connected to the air intake end through a mass flow meter, and the dilution gas in the dilution gas cylinder enters the main reaction tube through the air intake end.

[0029] The present invention also provides an application method of the free radical activity measurement system, as detailed below:

[0030] S11, sample gas is introduced into the main reaction tube through the air intake module;

[0031] S12, turn on the first light source and irradiate the photolysis laser into the main reaction tube to photolyze the free radical precursors in the sample gas in the main reaction tube and generate free radicals;

[0032] S13, the free radical detection module acquires the free radicals generated in the main reaction tube in real time through the sampling interface, and measures the fluorescent photon signal of the free radicals in real time;

[0033] S14, perform single-exponential fitting on the real-time measured fluorescence photon signal of free radicals to obtain the single-exponential fitting formula for the fluorescence photon signal, and obtain the free radical activity k in the sample gas based on the single-exponential fitting formula. radical 1; The single-exponential fitting formula is shown below:

[0034]

[0035] Where S (radical) t The fluorescence photon signal measured at time t, t0 represents the fluorescence photon signal measured at the initial time; a1 represents the exponential parameter of the single exponential fitting formula.

[0036] The measured free radical activity k in the sample gas radical 1 = a1.

[0037] Preferably, the main reaction tube is further irradiated with absorbed laser light by a second light source, and the concentration of free radical precursors in the main reaction tube is detected in real time by a second detector; and a certain amount of free radical precursors or a certain amount of dilution gas is introduced into the main reaction tube through an air intake module to control the concentration of free radical precursors in the main reaction tube in real time; as detailed below:

[0038] S21, sample gas is introduced into the main reaction tube through the air intake module;

[0039] S22, turn on the second light source and irradiate the main reaction tube with an absorption laser. After the absorption laser is absorbed by the free radical precursor in the sample gas in the main reaction tube, it is emitted through the main reaction tube to the second detector. The intensity of the emitted absorption laser emitted through the main reaction tube is detected in real time by the second detector.

[0040] Based on the emitted light intensity of the absorbed laser detected in real time by the second detector, and based on the Lambert-Beer gas absorption law, the concentration of free radical precursors in the main reaction tube is calculated in real time.

[0041] S23, under the condition that the concentration of free radical precursors in the sample gas introduced into the main reaction tube changes with time.

[0042] If the concentration of free radical precursors in the main reaction tube detected by the second detector is too low, a certain amount of free radical precursors will be introduced into the main reaction tube, and the concentration of free radical precursors in the main reaction tube will be detected in real time by the second detector until the concentration of free radical precursors in the main reaction tube reaches the set value.

[0043] If the concentration of free radical precursors in the main reaction tube detected by the second detector is too high, a certain amount of dilution gas is introduced into the main reaction tube, and the concentration of free radical precursors in the main reaction tube is detected in real time by the second detector until the concentration of free radical precursors in the main reaction tube reaches the set value.

[0044] S24, turn on the first light source and irradiate the photolysis laser into the main reaction tube to photolyze the free radical precursors in the sample gas in the main reaction tube and generate free radicals;

[0045] S24, the free radical detection module acquires the free radicals generated in the main reaction tube in real time through the sampling interface, and measures the fluorescent photon signal of the free radicals in real time;

[0046] S25, perform single-exponential fitting on the real-time measured fluorescence photon signal of free radicals to obtain the single-exponential fitting formula for the fluorescence photon signal, and obtain the free radical activity k in the sample gas based on the single-exponential fitting formula. radical 1; The single-exponential fitting formula is shown below:

[0047]

[0048] Where S (radical) t The fluorescence photon signal measured at time t, t0 represents the fluorescence photon signal measured at the initial time; a2 represents the exponential parameter of the single exponential fitting formula.

[0049] If a certain amount of free radical precursor is introduced into the main reaction tube in step S23, the free radical activity k in the measured sample gas will be...radical 1 = a2 * n1; n1 is the dilution factor of the sample gas produced by introducing the free radical precursor;

[0050] If a certain amount of dilution gas is introduced into the main reaction tube in step S23, the free radical activity k in the measured sample gas will be... radical 1 = a2 * n2; n2 is the dilution factor of the sample gas produced by the introduction of dilution gas.

[0051] Preferably, before detecting the free radical activity in the sample gas, zero air and a certain amount of free radical precursors are introduced into the main reaction tube through the gas inlet module to perform background detection on the measurement system, as shown below:

[0052] S31 introduces zero air and a certain amount of free radical precursors into the main reaction tube through the air intake module;

[0053] S32, turn on the first light source and irradiate the photolysis laser into the main reaction tube to photolyze the free radical precursor in the main reaction tube and generate free radicals;

[0054] S33, the free radical detection module acquires the free radicals generated in the main reaction tube in real time through the sampling interface, and measures the fluorescent photon signal of the free radicals in real time;

[0055] S34. A single-exponential fitting is performed on the fluorescence photon signal of the free radical measured in real time to obtain the single-exponential fitting formula for the fluorescence photon signal. The background free radical activity k of the measurement system is obtained based on the single-exponential fitting formula. radical 0; The single-exponential fitting formula is shown below:

[0056]

[0057] Where S (radical) t The fluorescence photon signal measured at time t, t0 represents the fluorescence photon signal measured at time t0, i.e., the initial time; a0 is the exponential parameter of the single exponential fitting formula;

[0058] The background free radical activity k of the measurement system radical 0 = a0;

[0059] After background detection, when detecting the free radical activity in the sample gas, the measured free radical activity k in the sample gas will be... radical 1 minus the background free radical activity k of the measurement system radical 0, yielding the actual free radical activity k in the sample gas. radical , i.e., k radical =k radical 1-k radical 0.

[0060] The advantages of this invention are:

[0061] (1) The present invention can directly measure the free radical activity in the sample gas, i.e. the ambient atmosphere, in real time online.

[0062] (2) The present invention can monitor the concentration of free radical precursors in real time, which is beneficial to the accurate measurement of free radical activity under complex external environment and has the advantage of high sensitivity.

[0063] (3) The measurement system of this invention employs a design where the photolysis laser passes through the center of the main reaction tube, and the absorption laser passes through the outer ring of the photolysis laser, undergoing multiple reflections back and forth in the beaded gaps between the main reaction tubes. This design maximizes the space utilization within the main reaction tube while improving the photolysis efficiency of free radicals and the absorption optical path of the precursors. It boasts advantages such as multiple reflections, long optical path, and low detection limit, enabling the measurement of extremely low concentrations of free radical precursors. Furthermore, a beam expander is used to expand the photolysis laser beam to a certain size, ensuring the radial uniformity of the free radical concentration generated by the photolysis of free radical precursors in the main reaction tube. The outlet of the main reaction tube is equipped with laser energy monitoring, which allows for feedback control of energy changes, ensuring the free radical concentration level and improving the signal-to-noise ratio.

[0064] (4) Due to the high activity and extremely low concentration of free radicals, the free radical detection module of this invention employs highly sensitive detection technology. The free radical sampling interface uses a conical nozzle with micro-pores, which serves the following purposes: 1. To achieve ultrasonic jetting, reducing collision loss during free radical sampling, a prerequisite for free radical measurement; 2. To achieve the collimation effect of the conical nozzle with micro-pores, realizing a sampling beam for free radicals, reducing diffusion loss during sampling, and increasing the concentration of free radicals during fluorescence excitation. Furthermore, a beam expander is used after the detection laser emission to increase the contact area between the detection laser and the sampling beam, thereby improving the excitation efficiency of free radicals.

[0065] (5) The design of the gas inlet structure of the reaction module of the present invention ensures that the gas in the main reaction tube presents a stable laminar flow state, thereby ensuring that the free radicals generated by photolysis do not have obvious diffusion and collision phenomena at various positions in the main reaction tube, and ensuring that the free radicals are evenly distributed in the main reaction tube. Both the main inlet channel and the main outlet channel are perpendicular to the main reaction tube, which can increase the gas flow velocity, accelerate gas mixing and reduce collision loss, and at the same time facilitate the formation of a stable laminar flow in the main reaction tube, which can reduce the free radical loss caused by wall collision. The sampling interface is connected to the lower side wall of the main reaction tube near the outlet end, which allows the free radicals generated after photolysis of the gas entering the main reaction tube from the inlet end to have enough time to mix evenly and form a stable laminar flow before being sampled by the sampling interface.

[0066] (6) This invention can not only accurately measure the concentration of free radical precursors in real time, but also autonomously control the concentration of free radical precursors in real time. Since the concentration of free radical precursors may interfere with the measurement of free radical activity, the lower the concentration of free radical precursors, the less interference there will be, provided that the measurement of free radical activity is satisfied. Therefore, real-time monitoring and control of the concentration of free radical precursors is beneficial for the accurate measurement of free radical activity in complex external environments, and has the advantage of high sensitivity. Furthermore, the measurement system of this invention does not require external equipment to monitor the concentration of free radical precursors, realizing system integration, and the structure is simpler and more intuitive. In addition, the amount of free radical precursors generated can be controlled by adjusting the illumination area of ​​the light source in the free radical precursor generator or by adjusting the gas flow rate of the mass flow meter. By setting two branch pipes and two mass flow meters, it is convenient to adjust the water vapor concentration in the free radical precursors.

[0067] (7) Before the formal measurement, the detection limit of the measurement system is measured through the third zero-air bottle in the second air intake assembly to perform background testing on the detection system. During the measurement process, if the concentration of free radical precursors provided by the external atmosphere is found to be too high (under high pollution conditions) or the humidity detection module detects excessive humidity, causing the measurement result of the free radical detection module to be higher than the target level, dilution gas is introduced into the measurement system through the dilution gas bottle in the second air intake assembly for dilution. Finally, the obtained free radical activity is corrected according to the corresponding dilution factor. This scheme solves the problem of measuring free radical activity under high pollution background in atmospheric environmental monitoring.

[0068] (8) Because free radicals react with the ambient atmosphere, their concentration decreases, which is then detected by the free radical detection module and recorded as the decay curve of the fluorescent photon signal. Since the free radical concentration is extremely low, the concentration of the components participating in the reaction is much greater than that of the free radicals, and can be considered a constant. This satisfies the definition of a pseudo-first-order reaction in reaction kinetics. All components X in the atmosphere that react with free radicals... i The sum of the products of the free radical activity k and its corresponding reaction rate constant is the free radical activity k. radical Therefore, in this invention, the free radical activity k can be obtained by performing a single exponential fitting on the decay curve of the fluorescent photon signal. radical The value of . Attached Figure Description

[0069] Figure 1 This is a schematic diagram of a free radical activity measurement system.

[0070] Figure 2 This is a simulated optical path diagram of a beam expander device for a free radical activity measurement system.

[0071] Figure 3 This is a simulated optical path diagram inside the main reaction tube of a free radical activity measurement system.

[0072] Figure 4 This is a flow field simulation diagram inside the main reaction tube of a free radical activity measurement system;

[0073] Figure 5 This is a simulation diagram of the comparative flow field inside the main reaction tube of a free radical activity measurement system without a diffusion section.

[0074] The attached figures are labeled as follows:

[0075] 1 is the main reaction tube; 2-1 and 2-2 are irradiation windows; 3 is the main air intake channel; 4 is the first air inlet;

[0076] 5 is the second air inlet; 6 is the main air outlet channel; 7 is the insertion port; 8 is the sampling interface;

[0077] 9 is the first light source; 10-1 and 10-2 are the first reflecting mirrors; 11 is the beam expander; 11-1 is the concave lens;

[0078] 11-2 is a convex lens; 12 is the first detector; 13-1 is the detection cavity; 13-2 is the detection laser source;

[0079] 13-3 is the detection laser beam expander; 13-4 is the detection laser detector; 14 is the second light source;

[0080] 15-1 and 15-2 are the second reflecting mirrors; 15-3 and 15-4 are hollow spherical reflecting mirrors;

[0081] 16 is the second detector; 17-1 is the free radical precursor synthesis gas cylinder; 17-2 is the second zero-air cylinder;

[0082] 17-3 is the third zero-air cylinder; 17-4 is the dilution gas cylinder;

[0083] 18-1, 18-2, 18-3, 18-4, and 18-5 are mass flow meters; 19 is a free radical precursor generator; 20 is a humidifier bottle; 21 is a temperature and humidity detection module; 22 is an air pump; and 23 is a data acquisition and control module. Detailed Implementation

[0084] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0085] Example 1

[0086] Depend on Figure 1As shown, a free radical activity measurement system includes a reaction module, an optical path and light intensity detection module, an air inlet module, an air outlet module, a free radical detection module, a temperature and humidity detection module 21, and a data acquisition and control module 23.

[0087] The reaction module includes: irradiation windows 2-1 and 2-2, a main reaction tube 1, an air inlet, an air outlet, and a sampling interface 8. Irradiation windows 2-1 and 2-2 are located at both ends of the main reaction tube 1, are made of quartz material, and are used to seal the main reaction tube 1 and transmit light.

[0088] The air inlet and air outlet are respectively connected to the main reaction tube 1 and are respectively connected to the upper side wall of the main reaction tube 1. The air inlet is connected to the upper side wall near the irradiation window 2-1, and the air outlet is connected to the upper side wall near the irradiation window 2-2.

[0089] The air inlet end includes: a main air inlet channel 3, and a first air inlet 4 and a second air inlet 5 respectively connected to the main air inlet channel 3; the main air inlet channel 3 is vertically connected to the upper side wall of the main reaction tube 1 near the irradiation window 2-1. The air outlet end includes: a main air outlet channel 6, and an insertion port 7 connected to the main air outlet channel 6; the main air outlet channel 6 is vertically connected to the upper side wall of the main reaction tube 1 near the irradiation window 2-2. Both the main air inlet channel 3 and the main air outlet channel 6 are perpendicular to the main reaction tube 1, which can increase the gas flow velocity, accelerate gas mixing and reduce collision loss, and at the same time facilitate the formation of stable laminar flow in the main reaction tube 1, which can reduce free radical loss caused by wall collision.

[0090] The sampling interface 8 is also connected to the lower side wall of the main reaction tube 1, located near the outlet end, and its sampling nozzle extends into the main reaction tube 1. The sampling interface 8 is conical, with the opening serving as the sampling nozzle and the bottom connected to the free radical detection module. The connection of the sampling interface 8 to the lower side wall of the main reaction tube 1 near the outlet end allows sufficient time for the free radicals generated after photolysis of the gas entering the main reaction tube 1 from the inlet end to mix evenly and form a stable laminar flow before being sampled by the sampling interface 8.

[0091] The insertion port 7 is connected to the temperature and humidity detection module 21 and is used to monitor the temperature and humidity of the gas in the main reaction tube 1 in real time.

[0092] The main reaction tube 1, the inlet end, the outlet end, and the sampling interface 8 are all made of aluminum alloy, with the inner wall coated with a Teflon film, which can effectively reduce gas wall loss.

[0093] The air intake module includes: a first air intake component, namely a free radical precursor air intake component; a second air intake component, namely a zero air / dilution gas air intake component; and a sample gas air intake component, namely an ambient atmosphere air intake component. The free radical precursor air intake component is connected to the first air intake port 4, the zero air / dilution gas air intake component is connected to the second air intake port 5, and the ambient atmosphere air intake component is connected to the main air intake channel 3.

[0094] The sample gas inlet assembly uses a Teflon tube to directly sample the ambient atmosphere. The use of a Teflon tube can reduce sample loss during the inlet process.

[0095] The first air intake assembly includes: a free radical precursor synthesis gas cylinder 17-1, a free radical precursor generator 19, a second zero air cylinder 17-2, a humidifier 20, and mass flow meters 18-1, 18-2, and 18-3.

[0096] The output pipe of the free radical precursor synthesis gas cylinder 17-1 is connected to the free radical precursor generator 19 via a mass flow meter 18-1. The free radical precursor generator 19 is equipped with a light source. The free radical precursor synthesis gas output from the free radical precursor synthesis gas cylinder 17-1 is photolyzed by the light source in the free radical precursor generator 19 to generate free radical precursors. The amount of free radical precursors generated can be controlled by adjusting the illumination area of ​​the light source in the free radical precursor generator 19 or by adjusting the gas flow rate of the mass flow meter 18-1.

[0097] The output pipe of the second zero-air cylinder 17-2 is connected to two parallel branch pipes via mass flow meters 18-2 and 18-3, respectively. Mass flow meter 18-2 is connected to the first branch pipe, and mass flow meter 18-3 is connected to the second branch pipe. A humidifier bottle 20 is installed on the second branch pipe. The first and second branch pipes merge and are then connected to the output end of the free radical precursor generator 19. The generated water vapor and free radical precursor are combined and enter the main reaction pipe 1 through the first air inlet 4. By setting up two branch pipes and two mass flow meters, it is easy to adjust the water vapor concentration. The temperature and humidity detection module 21, which is connected to the insertion port 7 at the air outlet, can provide real-time feedback on the water vapor concentration, thereby obtaining the target water vapor concentration. The free radical precursor generator 19 and the humidifier bottle 20 are existing equipment and can be directly obtained commercially. The entire structure for the generation and concentration adjustment of free radical precursors and water vapor is simple and easy to implement.

[0098] During the measurement process, if the concentration of free radical precursors provided by the external atmosphere is found to be too low or the temperature and humidity detection module detects that the humidity is too low, a certain amount of free radical precursors will be introduced into the measurement system through the first air intake component.

[0099] The second air intake assembly includes: a third zero air cylinder 17-3, a dilution gas cylinder 17-4, and mass flow meters 18-4 and 18-5.

[0100] The output pipe of the third zero air cylinder 17-3 is connected to the second air inlet 5 via a mass flow meter 18-4, and the output pipe of the dilution gas cylinder 17-4 is connected to the second air inlet 5 via a mass flow meter 18-5.

[0101] Before the formal measurement, the detection limit of the measurement system is measured through the third zero-air cylinder 17-3 in the second air intake assembly to perform background testing on the detection system. During the measurement process, if the concentration of free radical precursors provided by the external atmosphere is found to be too high (in a highly polluted environment) or the humidity detection module detects excessively high humidity, causing the measurement result of the free radical detection module to be higher than the target level, nitrogen (N2) is introduced into the measurement system through the dilution gas cylinder 17-4 in the second air intake assembly for dilution. Finally, the obtained free radical activity is corrected accordingly according to the corresponding dilution factor. This scheme solves the problem of measuring free radical activity under high pollution background in atmospheric environmental monitoring.

[0102] The gas outlet module includes a gas pump 22; the gas pump 22 is connected to the main gas outlet channel 6 and is used to maintain a stable gas flow rate in the main reaction tube 1.

[0103] The optical path and light intensity detection module includes a first light source 9, first reflectors 10-1 and 10-2, a beam expander 11, a first detector 12, a second light source 14, second reflectors 15-1 and 15-2, hollow spherical reflectors 15-3 and 15-4, and a second detector 16.

[0104] In this process, the emitted light from the first light source 9 passes sequentially through the first reflectors 10-1 and 10-2, enters the beam expander 11 for collimation and expansion, then enters the main reaction tube 1 through the illumination window 2-1, passes through the center of the main reaction tube 1, and exits through the illumination window 2-1, illuminating the first detector 12. The first detector 12 is used to collect the light energy. Figure 2 As shown, the beam expander 11 includes a concave lens 11-1 and a convex lens 11-2 along the light propagation direction. The beam expansion can be adjusted by changing the distance between the concave lens 11-1 and the convex lens 11-2. Irradiating the center of the main reaction tube 1 with the emitted light from the first light source 9 facilitates the rapid and uniform distribution of the generated free radicals within the main reaction tube 1, reducing the radial gradient distribution of free radical concentration. The beam expander 11 also enables the emitted light from the first light source 9 to achieve a uniform radial distribution of the free radical concentration generated by photolysis, minimizing the interference of the radial concentration distribution on the free radical concentration measurement.

[0105] The emitted light from the second light source 14 passes sequentially through the second reflectors 15-1 and 15-2 and the illumination window 2-1 of the main reaction tube 1, illuminating the hollow spherical reflector 15-3. Figure 3 As shown, the emitted light from the second light source 14 enters the main reaction tube 1 through the edge through-hole on the hollow spherical reflector 15-3, and passes through the main reaction tube 1 along the periphery of the emitted light from the first light source 9, illuminating the hollow spherical reflector 15-4. After multiple reflections between the hollow spherical reflectors 15-4 and 15-3, the emitted light from the second light source 14 exits through the edge through-hole of the hollow spherical reflector 15-4, and then illuminates the second detector 16 through the illumination window 2-2. The second detector 16 is used to collect light intensity. Figure 1 As shown, hollow spherical reflectors 15-3 and 15-4 are respectively positioned in the main reaction tube 1 near the illumination windows 2-1 and 2-2. The hollow spherical reflectors 15-3 and 15-4 cause the emitted light from the second light source 14 to be reflected multiple times in the main reaction tube 1, thereby increasing the optical path and preventing the reflected light from contacting the sampling interface 8.

[0106] The free radical concentration within the main reaction tube 1 of this invention is uniform. On one hand, a beam expander 11 is used to expand the photolysis laser beam to a certain size, maximizing the radial uniformity of the free radical concentration generated by the photolysis of the free radical precursor in the main reaction tube 1. On the other hand, as... Figure 4 and Figure 5 As shown in the comparison, the darker the color of the indicator bar on the left, the greater the gas flow rate. Compared with direct connection to the inlet pipe, the design of the inlet structure of the reaction module of the present invention ensures that the gas in the main reaction tube 1 presents a stable laminar flow state, thereby ensuring that the free radicals generated by photolysis will not have obvious diffusion and collision phenomena at various positions in the main reaction tube, and ensuring that the free radicals are evenly distributed in the main reaction tube.

[0107] The free radical detection module is connected to the sampling interface 8. The gas in the main reaction tube 1 enters the free radical detection module through the sampling interface 8. The free radical detection module is used to detect free radicals in the gas. The free radical detection module includes: a detection cavity 13-1, a detection laser source 13-2, a detection laser beam expander 13-3, and a detection laser detector 13-4.

[0108] The gas in the main reaction tube 1 enters the detection chamber 13-1 through the sampling interface 8. The detection laser source 13-2 is used to emit a detection laser. After being expanded by the detection laser beam expander 13-3, the detection laser enters the detection chamber 13-1 to excite free radicals in the gas in the detection chamber 13-1 to generate fluorescence. The photomultiplier tube in the detection chamber 13-1 is used to detect the fluorescence photon signal. Subsequently, the detection laser is emitted from the detection chamber 13-1 and irradiates the detection laser detector 13-4. The detection laser detector 13-4 is used to collect the emitted laser energy.

[0109] The data acquisition and control module 23 is connected to each data acquisition device and each control device in the measurement system, and is used to receive each acquired data, control each control device, and perform related calculation tasks.

[0110] In this invention, the emitted light from the first light source 9 is a photolysis laser, used to photolyze free radical precursors to generate free radicals. The photolysis laser is collimated and expanded by the first reflectors 10-1 and 10-2 and the beam expander 11, and then irradiates the main reaction tube 1 through the transmission irradiation window 2-1 and the central through-hole of the hollow spherical reflector 15-3. The photolysis laser then passes through the center of the main reaction tube 1 and exits through the irradiation window 2-2, irradiating the first detector 12, i.e., the laser power meter. The first detector 12 is used to synchronously monitor the emitted energy of the photolysis laser. When the photolysis laser passes through the main reaction tube 1, it photolyzes the free radical precursors in the main reaction tube 1 to generate free radicals. For example, if the free radical precursor is formaldehyde, it is photolyzed to generate HO2 free radicals; if the free radical precursor is nitrous acid, it is photolyzed to generate OH free radicals; if the free radical precursor is ozone and water, it is photolyzed to generate OH free radicals, etc.

[0111] Free radicals react with the ambient atmosphere, causing their concentration to decay. This decay is detected by the free radical detection module, which records the decay curve of the fluorescent photon signal. Because the free radical concentration is extremely low, and the concentration of the reacting components is much greater than that of the free radicals, it can be considered a constant. This satisfies the definition of a pseudo-first-order reaction in reaction kinetics. All components X in the atmosphere that react with the free radicals... i The sum of the products of the free radical activity k and its corresponding reaction rate constant is the free radical activity k. radical It can be expressed by the following formula:

[0112]

[0113] Therefore, in this invention, the free radical activity k can be obtained by performing a single exponential fitting on the decay curve of the fluorescent photon signal. radical The value of S (radical). t The fluorescence photon signal measured at time t, The fluorescence photon signal measured at time t0, i.e., the initial time.

[0114] In this embodiment, the emitted light of the second light source 14 is an absorptive laser. After being reflected by the second reflectors 15-1 and 15-2, the absorptive laser passes through the illumination window 2-1 and the upper edge through-hole of the hollow spherical reflector 15-3, illuminating the main reaction tube 1. It then passes through the periphery of the emitted light of the first light source 9 (i.e., the photolysis laser) and illuminates the hollow spherical reflector 15-4. After multiple reflections between the hollow spherical reflectors 15-3 and 15-4, it passes through the upper edge through-hole of the hollow spherical reflector 15-4 and exits through the illumination window 2-2, illuminating the second detector 16 (i.e., the photodetector). The second detector 16 is used to synchronously monitor the emitted light intensity of the absorptive laser. Based on the absorption characteristics of the absorptive laser, the concentration of free radical precursors is detected. This method has a short reaction time, and when the intensity of the absorptive laser is constant, the decomposition rate of the free radical precursors remains unchanged. Therefore, it can be used for real-time detection of the concentration of free radical precursors. The formula for calculating the concentration of free radical precursors is based on the Lambert-Beer gas absorption law, as shown below:

[0115]

[0116] Where C represents the concentration of free radical precursors, L represents the optical path length, σ represents the absorption cross section of the free radical precursors, I0 represents the incident light intensity, i.e. the emitted light intensity of the absorbed laser emitted by the second light source 14, I represents the emitted light intensity, i.e. the emitted light intensity of the absorbed laser after passing through the gas mixture as monitored by the second detector 16, and λ represents the wavelength of the absorbed laser.

[0117] In this invention, the sample gas, i.e., the ambient air, is introduced into the main reaction tube 1 through the main inlet channel 3. Free radical precursors in the ambient air, or free radical precursors entering through the first inlet 4, are irradiated by the first light source 9 to generate free radicals. They are then irradiated by the second light source 14 and the concentration of free radical precursors is simultaneously monitored by the second detector 16. By monitoring the concentration of free radical precursors in real time, the concentration of free radical precursors at the inlet end can be dynamically controlled to achieve the set value. There is no need to use external equipment to monitor the concentration of free radical precursors in the main reaction tube 1, which realizes the integration of the system and makes the structure simpler, more intuitive and accurate.

[0118] The necessity of measuring the concentration of free radical precursors in this invention lies in two aspects: First, the external atmospheric environment is constantly changing, and the concentration of free radical precursors in the sample gas entering the main reaction tube 1 from the inlet end will change at any time. Second, a small amount of free radical precursors entering the main reaction tube 1 from the inlet end may be adsorbed, causing wall loss and resulting in slight changes in the concentration of free radical precursors in the main reaction tube 1 and the concentration of free radical precursors in the external atmospheric environment. Since free radical precursors are the source of free radical generation, the concentration of free radical precursors in the main reaction tube 1 directly determines the concentration of free radicals generated in the main reaction tube 1. The stability of the concentration of free radical precursors determines the stability of the concentration of generated free radicals. Therefore, the measurement of the concentration of free radical precursors in the main reaction tube 1 and the guarantee of its stability are prerequisites for the accurate measurement of free radical activity.

[0119] Example 2

[0120] Based on the free radical activity measurement system provided in Embodiment 1 above, a method for measuring free radical activity includes the following steps:

[0121] S1, Background Detection:

[0122] S101, a certain amount of zero air is introduced into the main reaction tube 1 through the third zero air bottle 17-3 in the second air intake assembly, and a certain amount of free radical precursor is introduced into the main reaction tube 1 through the first air intake assembly, i.e., the free radical precursor air intake assembly.

[0123] S102, turn on the second light source 14 and irradiate the main reaction tube 1 with an absorption laser. According to the light intensity reduction value of the absorption laser measured by the second detector 16, the background free radical precursor concentration C0 of the measurement system can be calculated by Equation 1. The background free radical precursor concentration in the main reaction tube 1 is adjusted by the first air intake component and the second air intake component so that the background free radical precursor concentration reaches the set value.

[0124] S103, turn on the first light source 9, irradiate the photolysis laser into the main reaction tube 1, photolyze the free radical precursor in the main reaction tube 1 to generate free radicals;

[0125] S104, the free radical detection module acquires the free radicals generated in the main reaction tube 1 in real time through the sampling interface 8, and measures the fluorescent photon signal of the free radicals in real time;

[0126] S105, according to Equation 3, a single-exponential fit is performed on the fluorescence photon signal of the free radical measured in real time to obtain the attenuation curve of the fluorescence photon signal, i.e., the single-exponential fit formula. Then, the background free radical activity k of the measurement system is obtained based on the fitted single-exponential fit formula. radical 0;

[0127] The single-exponential fitting formula is shown below:

[0128]

[0129] Where S (radical) t The fluorescence photon signal measured at time t, t0 represents the fluorescence photon signal measured at time t0, i.e., the initial time; a0 is the exponential parameter of the single exponential fitting formula;

[0130] The background free radical activity k of the measurement system radical 0 = a0;

[0131] S2, when the concentration of free radical precursors in the ambient atmosphere changes over time, if the concentration of free radical precursors in the ambient atmosphere can meet the set value, then the actual free radical activity k in the ambient atmosphere... radical The first measurement method is as follows:

[0132] S201, sample gas, i.e. ambient air, is introduced into the main reaction tube 1 through the air intake module;

[0133] S202, turn on the second light source 14 and irradiate the main reaction tube 1 with an absorption laser. Based on the light intensity reduction value of the absorption laser measured by the second detector 16, the concentration of free radical precursors in the ambient atmosphere can be calculated by Equation 1, and the concentration of free radical precursors in the ambient atmosphere can reach the set value.

[0134] S203, turn on the first light source 9 and irradiate the photolysis laser into the main reaction tube 1 to photolyze the free radical precursors in the atmosphere inside the main reaction tube 1 and generate free radicals;

[0135] S204, the free radical detection module acquires the free radicals generated in the main reaction tube 1 in real time through the sampling interface 8, and measures the fluorescent photon signal of the free radicals in real time;

[0136] S205, according to Equation 3, a single-exponential fitting is performed on the real-time measured free radical fluorescence photon signal to obtain the single-exponential fitting formula for the fluorescence photon signal. Based on the single-exponential fitting formula, the free radical activity k in the ambient atmosphere is obtained. radical 1;

[0137] The single-exponential fitting formula is shown below:

[0138]

[0139] Where S (radical) t The fluorescence photon signal measured at time t, The fluorescence photon signal measured at time t0, i.e., the initial time; a1 is the exponential parameter of the single exponential fitting formula; the measured free radical activity k in the ambient atmosphere.radical 1 = a1;

[0140] The measured free radical activity k in the ambient atmosphere radical 1 minus the background free radical activity k of the measurement system radical 0, to obtain the actual free radical activity k in the ambient atmosphere. radical k radical =k radical 1-k radical 0.

[0141] S3, when the concentration of free radical precursors in the ambient atmosphere changes over time, if the concentration of free radical precursors in the ambient atmosphere fails to meet the set value and is lower than the set value, then the actual free radical activity k in the ambient atmosphere... radical The second measurement method is as follows:

[0142] S301, sample gas, i.e. ambient air, is introduced into the main reaction tube 1 through the air intake module;

[0143] S302, turn on the second light source 14 and irradiate the main reaction tube 1 with an absorptive laser. Based on the light intensity reduction value of the absorptive laser measured by the second detector 16, the concentration of free radical precursors in the ambient atmosphere can be calculated using Equation 1. If the concentration of free radical precursors in the ambient atmosphere is lower than the set value, or the humidity of the sample gas is too low, a certain amount of free radical precursors is introduced into the main reaction tube 1 through the first air inlet component, and the concentration of free radical precursors in the main reaction tube 1 is detected in real time by the second detector 16 until the concentration of free radical precursors in the main reaction tube 1 reaches the set value.

[0144] S303, turn on the first light source 9 and irradiate the photolysis laser into the main reaction tube 1 to photolyze the free radical precursors in the atmosphere inside the main reaction tube 1 and generate free radicals;

[0145] S304, the free radical detection module acquires the free radicals generated in the main reaction tube 1 in real time through the sampling interface 8, and measures the fluorescent photon signal of the free radicals in real time;

[0146] S305, according to Equation 3, a single-exponential fitting is performed on the fluorescence photon signal of the free radical measured in real time to obtain the single-exponential fitting formula for the fluorescence photon signal. Based on the single-exponential fitting formula, the free radical activity k in the ambient atmosphere is obtained. radical 1;

[0147] The single-exponential fitting formula is shown below:

[0148]

[0149] Where S (radical) tThe fluorescence photon signal measured at time t, The fluorescence photon signal measured at time t0, i.e., the initial time; a21 is the exponential parameter of the single exponential fitting formula; the measured free radical activity k in the ambient atmosphere. radical 1 = a21 * n1;

[0150] n1 represents the dilution factor of the sample gas flow rate generated by the introduction of the free radical precursor. Specifically, it is the dilution factor of the increased flow rate of the free radical precursor introduced into the main reaction tube 1 through the first inlet 4 relative to the total flow rate of the free radical precursor introduced into the main reaction tube through the main inlet channel 3. In experiments, when the free radical precursor concentration is too low, adding more free radical precursor increases its concentration. However, in practice, the flow rate of this additional free radical precursor is very small, relatively low compared to the flow rate in the main reaction tube. Therefore, the dilution factor of the sample gas flow rate can be ignored, and n1 can be approximated as 1.

[0151] The measured free radical activity k in the ambient atmosphere radical 1 minus the background free radical activity k of the measurement system radical 0, to obtain the actual free radical activity k in the ambient atmosphere. radical k radical =k radical 1-k radical 0.

[0152] S4, when the concentration of free radical precursors in the ambient atmosphere changes over time, if the concentration of free radical precursors in the ambient atmosphere fails to meet the set value but exceeds the set value, then the actual free radical activity k in the ambient atmosphere... radical The third measurement method is as follows:

[0153] S401, sample gas, i.e. ambient air, is introduced into the main reaction tube 1 through the air intake module;

[0154] S402, turn on the second light source 14 and irradiate the main reaction tube 1 with an absorptive laser. Based on the light intensity reduction value of the absorptive laser measured by the second detector 16, the concentration of free radical precursors in the ambient atmosphere can be calculated using Equation 1. If the concentration of free radical precursors in the ambient atmosphere is higher than the set value, or the humidity of the sample gas is too high, a certain amount of dilution gas, i.e., nitrogen N2, is introduced into the main reaction tube 1 through the second gas inlet assembly. The concentration of free radical precursors in the main reaction tube 1 is detected in real time by the second detector 16 until the concentration of free radical precursors in the main reaction tube 1 reaches the set value.

[0155] S403, turn on the first light source 9 and irradiate the photolysis laser into the main reaction tube 1 to photolyze the free radical precursors in the atmosphere inside the main reaction tube 1 and generate free radicals;

[0156] S404, the free radical detection module acquires the free radicals generated in the main reaction tube 1 in real time through the sampling interface 8, and measures the fluorescent photon signal of the free radicals in real time;

[0157] S405, according to Equation 3, a single-exponential fitting is performed on the fluorescence photon signal of the free radical measured in real time to obtain the single-exponential fitting formula for the fluorescence photon signal. Based on the single-exponential fitting formula, the free radical activity k in the ambient atmosphere is obtained. radical 1;

[0158] The single-exponential fitting formula is shown below:

[0159]

[0160] Where S (radical) t The fluorescence photon signal measured at time t, The fluorescence photon signal measured at time t0, i.e., the initial time; a22 is the exponential parameter of the single exponential fitting formula; the measured free radical activity k in the ambient atmosphere. radical 1 = a² * n²;

[0161] n2 represents the dilution factor of the sample gas flow rate generated by the introduced dilution gas, specifically the dilution factor of the dilution gas flow rate introduced into the main reaction tube 1 by the second inlet assembly through the second inlet port 5, relative to the total flow rate of free radical precursors introduced into the main reaction tube through the main inlet channel 3. When the concentration of free radical precursors or atmospheric samples is too high, it generally indicates severely polluted air. Therefore, the dilution gas flow rate introduced into the main reaction tube 1 by the second inlet assembly through the second inlet port 5 is relatively high, and thus the sample gas flow rate dilution factor cannot be ignored.

[0162] The measured free radical activity k in the ambient atmosphere radical 1 minus the background free radical activity k of the measurement system radical 0, to obtain the actual free radical activity k in the ambient atmosphere. radical k radical =k radical 1-k radical 0.

[0163] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A free radical activity measurement system, characterized in that, include: The reaction module, optical path and light intensity detection module, air intake module, air exhaust module, and free radical detection module are all included. The reaction module includes: a main reaction tube (1), and an air inlet and a sampling interface (8) connected to the main reaction tube (1); The optical path and light intensity detection module includes: a first light source (9) for emitting a photolysis laser into the main reaction tube (1); the photolysis laser is used to photolyze free radical precursors to generate free radicals; The air intake module is connected to the air intake end and is used to introduce gas into the main reaction tube (1); the air intake module introduces sample gas containing free radical precursors into the main reaction tube (1); The free radical detection module is connected to the sampling interface (8), and obtains the free radicals in the main reaction tube (1) through the sampling interface (8), and emits a detection laser to excite the free radicals to generate fluorescence. The free radical detection module is used to measure the fluorescence photon signal of the free radicals. The optical path and light intensity detection module further includes: a second light source (14) for emitting absorbed laser light into the main reaction tube (1) and a second detector (16); after being absorbed by the free radical precursor in the main reaction tube (1), the absorbed laser light passes through the main reaction tube (1) and is emitted to the second detector (16), and the second detector (16) is used to detect the emitted light intensity of the absorbed laser light emitted after passing through the main reaction tube (1); The air intake module further includes a first air intake assembly for providing free radical precursors and a second air intake assembly for providing dilution gas / zero air; The absorption laser is irradiated into the main reaction tube (1) by a second light source (14), and the concentration of free radical precursors in the main reaction tube (1) is detected in real time by a second detector (16); and a certain amount of free radical precursors or a certain amount of dilution gas is introduced into the main reaction tube (1) through the gas inlet module to control the concentration of free radical precursors in the main reaction tube (1) in real time; as shown below: S21, sample gas is introduced into the main reaction tube (1) through the gas inlet module; S22, turn on the second light source (14) and irradiate the main reaction tube (1) with an absorption laser. After the absorption laser is absorbed by the free radical precursor in the sample gas in the main reaction tube (1), it is emitted through the main reaction tube (1) to the second detector (16). The intensity of the emitted absorption laser emitted through the main reaction tube (1) is detected in real time by the second detector (16). Based on the emitted light intensity of the absorbed laser detected in real time by the second detector (16), and based on the Lambert-Beer gas absorption law, the concentration of free radical precursors in the main reaction tube (1) is calculated in real time. S23, when the concentration of free radical precursors in the sample gas introduced into the main reaction tube (1) changes over time. If the concentration of free radical precursor in the main reaction tube (1) detected by the second detector (16) is too low, a certain amount of free radical precursor is introduced into the main reaction tube (1), and the concentration of free radical precursor in the main reaction tube (1) is detected in real time by the second detector (16) until the concentration of free radical precursor in the main reaction tube (1) reaches the set value. If the concentration of free radical precursors in the main reaction tube (1) detected by the second detector (16) is too high, a certain amount of dilution gas is introduced into the main reaction tube (1), and the concentration of free radical precursors in the main reaction tube (1) is detected in real time by the second detector (16) until the concentration of free radical precursors in the main reaction tube (1) reaches the set value. S24, turn on the first light source (9) and irradiate the main reaction tube (1) with a photolysis laser to photolyze the free radical precursors in the sample gas in the main reaction tube (1) and generate free radicals; S24, the free radical detection module acquires the free radicals generated in the main reaction tube (1) in real time through the sampling interface (8), and measures the fluorescent photon signal of the free radicals in real time; S25, perform single-exponential fitting on the real-time measured fluorescence photon signal of free radicals to obtain the single-exponential fitting formula for the fluorescence photon signal, and obtain the free radical activity k in the sample gas based on the single-exponential fitting formula. radical 1; The single-exponential fitting formula is shown below: Where S (radical) t The fluorescence photon signal measured at time t, t0 represents the fluorescence photon signal measured at the initial time; a2 represents the exponential parameter of the single exponential fitting formula. If a certain amount of free radical precursor is introduced into the main reaction tube (1) in step S23, the free radical activity k in the measured sample gas will be... radical 1 = a2 * n1; n1 is the dilution factor of the sample gas produced by introducing the free radical precursor; If a certain amount of dilution gas is introduced into the main reaction tube (1) in step S23, the free radical activity k in the measured sample gas will be... radical 1 = a2 * n2; n2 is the dilution factor of the sample gas produced by the introduction of dilution gas.

2. The free radical activity measurement system according to claim 1, characterized in that, The main reaction tube (1) has irradiation windows at both ends, namely the first irradiation window and the second irradiation window, which are used to seal the main reaction tube (1) and transmit light. A first hollow spherical reflector is provided in the main reaction tube (1) near the first irradiation window, and a second hollow spherical reflector is provided near the second irradiation window. The first and second hollow spherical reflectors are hollow spherical reflectors with a central through hole in the middle and an edge through hole at the edge of the spherical reflector. The photolysis laser emitted by the first light source (9) is collimated and expanded by the beam expander (11), and then enters the main reaction tube (1) through the center of the first irradiation window and the middle through hole of the first hollow spherical mirror in sequence. It passes through the center of the main reaction tube (1) and exits through the middle through hole of the second hollow spherical mirror and the center of the second irradiation window in sequence. The absorbed laser emitted by the second light source (14) enters the main reaction tube (1) through the edge of the first illumination window and the edge through hole of the first hollow spherical reflector in sequence. After passing through the main reaction tube (1), it is projected onto the second hollow spherical reflector. After being reflected multiple times between the second hollow spherical reflector and the first hollow spherical reflector, it is then projected out through the edge through hole of the first hollow spherical reflector and the edge of the second illumination window and projects onto the second detector (16). Among them, the photolysis laser and the absorption laser in the main reaction tube (1) do not interfere with each other.

3. The free radical activity measurement system according to claim 1, characterized in that, The free radical detection module includes: a detection cavity (13-1), a detection laser source (13-2), a detection laser beam expander (13-3), and a detection laser detector (13-4); The free radicals in the main reaction tube (1) enter the detection cavity (13-1) through the sampling interface (8). The detection laser source (13-2) is used to emit detection laser. After the detection laser is expanded by the detection laser beam expander (13-3), it enters the detection cavity (13-1) to excite the free radicals in the detection cavity (13-1) to generate fluorescence. Then, the detection laser is emitted from the detection cavity (13-1) and irradiates the detection laser detector (13-4). The detection laser detector (13-4) is used to collect the emitted energy of the detection laser. The detection cavity (13-1) is equipped with a device for detecting fluorescent photon signals.

4. The free radical activity measurement system according to claim 1, characterized in that, The air intake end includes an air intake main channel (3); the air outlet end includes an air outlet main channel (6); The main intake channel (3) is vertically connected to the upper side wall of the main reaction tube (1) near one side end face; the main exhaust channel (6) is vertically connected to the upper side wall of the main reaction tube (1) near the other side end face; the sampling interface (8) is connected to the lower side wall of the main reaction tube (1) near the main exhaust channel (6); The sampling interface (8) is conical, with the sampling nozzle extending into the main reaction tube (1) and the bottom of the cone connected to the free radical detection module. The main outlet channel (6) is connected to the air pump (22); the main outlet channel (6) is also provided with an insertion port (7), which is connected to the temperature and humidity detection module (21) for real-time detection of the temperature and humidity of the gas in the main reaction tube (1).

5. The free radical activity measurement system according to claim 1, characterized in that, The first air intake assembly includes: a free radical precursor synthesis gas cylinder (17-1), a free radical precursor generator (19), a second zero air cylinder (17-2), and a humidifier (20); The output pipe of the free radical precursor synthesis gas cylinder (17-1) is connected to the input end of the free radical precursor generator (19) through a mass flow meter; the free radical precursor generator (19) is equipped with an adjustable light source for photolysis of the free radical precursor synthesis gas to generate free radical precursors. The output pipe of the second zero-air bottle (17-2) is connected to two parallel branch pipes through two mass flow meters. One of the branch pipes is equipped with a humidifier bottle (20) for generating water vapor. After the two branch pipes merge, they are first connected to the output end of the free radical precursor generator (19), and then connected to the air inlet. The water vapor and free radical precursor are combined into one line and enter the main reaction pipe (1) through the air inlet.

6. The free radical activity measurement system according to claim 1, characterized in that, The second air intake assembly includes: a third zero-air cylinder (17-3) and a dilution gas cylinder (17-4); the output pipe of the third zero-air cylinder (17-3) is connected to the air intake end through a mass flow meter, and the zero air in the third zero-air cylinder (17-3) enters the main reaction tube (1) through the air intake end; the output pipe of the dilution gas cylinder (17-4) is connected to the air intake end through a mass flow meter, and the dilution gas in the dilution gas cylinder (17-4) enters the main reaction tube (1) through the air intake end.

7. An application method applicable to the free radical activity measurement system according to claim 1, characterized in that, The details are as follows: S11, sample gas is introduced into the main reaction tube (1) through the gas inlet module; S12, turn on the first light source (9) and irradiate the main reaction tube (1) with a photolysis laser to photolyze the free radical precursors in the sample gas in the main reaction tube (1) and generate free radicals; S13, the free radical detection module acquires the free radicals generated in the main reaction tube (1) in real time through the sampling interface (8), and measures the fluorescent photon signal of the free radicals in real time; S14, perform single-exponential fitting on the real-time measured fluorescence photon signal of free radicals to obtain the single-exponential fitting formula for the fluorescence photon signal, and obtain the free radical activity k in the sample gas based on the single-exponential fitting formula. radical 1; The single-exponential fitting formula is shown below: Where S (radical) t The fluorescence photon signal measured at time t, t0 represents the fluorescence photon signal measured at the initial time; a1 represents the exponential parameter of the single exponential fitting formula. The measured free radical activity k in the sample gas radical 1 = a1.

8. The application method of the free radical activity measurement system according to claim 7, characterized in that, Before detecting the free radical activity in the sample gas, zero air and a certain amount of free radical precursors are introduced into the main reaction tube (1) through the gas inlet module to perform background detection on the measurement system, as shown below: S31, zero air and a certain amount of free radical precursors are introduced into the main reaction tube (1) through the air intake module; S32, turn on the first light source (9) and irradiate the photolysis laser into the main reaction tube (1) to photolyze the free radical precursor in the main reaction tube (1) and generate free radicals; S33, the free radical detection module acquires the free radicals generated in the main reaction tube (1) in real time through the sampling interface (8), and measures the fluorescent photon signal of the free radicals in real time; S34. A single-exponential fitting is performed on the fluorescence photon signal of the free radical measured in real time to obtain the single-exponential fitting formula for the fluorescence photon signal. The background free radical activity k of the measurement system is obtained based on the single-exponential fitting formula. radical 0; The single-exponential fitting formula is shown below: Where S (radical) t The fluorescence photon signal measured at time t, t0 represents the fluorescence photon signal measured at time t0, i.e., the initial time; a0 is the exponential parameter of the single exponential fitting formula; The background free radical activity k of the measurement system radical 0 = a0; After background detection, when detecting the free radical activity in the sample gas, the measured free radical activity k in the sample gas will be... radical 1 minus the background free radical activity k of the measurement system radical 0, yielding the actual free radical activity k in the sample gas. radical , i.e., k radical =k radical 1-k radical 0.

Images