Atmospheric nitrogen trioxide transport efficiency calibration and its reactive activity measurement system and method

Abstract

The application discloses a system for calibrating atmospheric nitrogen trioxide transmission efficiency and measuring reaction activity, comprising a dynamic humidity adjustment calibration module, a nitrogen trioxide dynamic stable source synthesis module, a reaction time measurement module and a double-channel resonant cavity measurement system module; the dynamic humidity adjustment calibration module and the nitrogen trioxide dynamic stable source synthesis module are arranged in parallel, and the two modules are connected with the reaction time measurement module after being combined; and the outlet end of the reaction time measurement module is connected with the double-channel resonant cavity test system module. The application further discloses a method for calibrating atmospheric nitrogen trioxide transmission efficiency and measuring reaction activity. The application has the beneficial effects that the nitrogen trioxide, nitrogen pentoxide, reaction concentration and reaction time after being corrected by temperature and humidity and balance are further simulated by a reaction simulation program, so that the reaction activity of atmospheric nitrogen trioxide is obtained, and the measurement error is reduced.

Description

Technical Field

[0001] This invention relates to the field of atmospheric environmental monitoring, and more particularly to a system and method for calibrating atmospheric nitrogen trioxide transport efficiency and measuring its reactivity. Background Technology

[0002] In 1971, Levy et al. first proposed that the troposphere is primarily an oxidizing atmosphere driven by free radical chemical reactions. Atmospheric oxidation capacity is a key factor playing a dominant role in regional pollution, global climate change, and the impact of atmospheric ecological environment. Understanding the chemical processes of nitrogen oxides is crucial to understanding atmospheric oxidation. Atmospheric oxidation capacity is mainly determined by free radical concentration and free radical reactivity (total removal rate):

[0003]

[0004] It is generally believed that atmospheric oxidation capacity during the day is mainly provided by chain reaction processes composed of OH free radicals, while atmospheric oxidation capacity at night is mainly manifested by NO3 free radicals. NO3 free radicals are key species in nighttime atmospheric chemistry and are the main oxidants of VOCs (volatile organic compounds) at night, especially exhibiting high reactivity to unsaturated olefin BVOCs (such as isoprene and monoterpenes).

[0005] Currently, while the technology for measuring NO3 concentration is relatively mature, research on its reactivity measurement technology is still relatively limited, making it impossible to quantitatively characterize the nighttime atmospheric oxidation capacity. Furthermore, the concentration and oxidizing capacity of NO3 free radicals in the atmosphere are closely related to the photochemical reaction conditions of the atmosphere the following day. Therefore, given my country's complex atmospheric conditions, conducting large-scale, highly sensitive, and accurate detection of NO3 free radicals and N2O5, as well as the determination of NO3 reactivity, in different regions and seasons is of practical significance for analyzing nighttime atmospheric chemical processes.

[0006] The usual methods for determining the reactivity of NO3 involve measuring the concentrations of various VOCs and calculating the reactivity based on the reaction rate constant, or calculating the reactivity using the NO3 steady-state assumption. In practical applications, due to limitations in conditions and technology, it is impossible to measure all VOCs that react with NO3. Furthermore, the steady-state assumption does not hold true under many unsteady-state conditions (such as exceptionally clean weather, high NO2 concentrations, low winter temperatures, or conditions influenced by other air masses, such as significant near-surface NO interference in urban areas). Therefore, establishing a kNO3 measurement method suitable for field applications is of great significance.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The technical problem to be solved by this invention is: how to solve the problem that current methods for measuring the reactivity of NO3 cannot be used under non-steady-state conditions, thereby providing a system and method for calibrating atmospheric nitrogen trioxide transport efficiency and measuring its reactivity that can be used in field applications.

[0009] The present invention solves the above-mentioned technical problems through the following technical means:

[0010] The atmospheric nitrogen trioxide transport efficiency calibration and reactivity measurement system includes a dynamic humidity adjustment calibration module, a nitrogen trioxide dynamic stable source synthesis module, a reaction time measurement module, and a dual-channel resonant cavity measurement system module. The dynamic humidity adjustment calibration module and the nitrogen trioxide dynamic stable source synthesis module are set in parallel, and after they are combined, they are connected to the reaction time measurement module. The outlet end of the reaction time measurement module is connected to the dual-channel resonant cavity test system module.

[0011] The nitrogen trioxide dynamic stable source synthesis module includes a NO standard gas pipeline, a high-purity air pipeline, an ozone generator, an air compressor, a reaction flow pipe, and a first heating and temperature control device. The high-purity air pipeline is connected to the ozone generator and the air compressor in sequence. The outlet end of the air compressor is mixed with the NO standard gas pipeline and then connected to the reaction flow pipe. The first heating and temperature control device is connected to the outside of the reaction flow pipe.

[0012] This invention uses a dynamic humidity calibration module to calibrate the humidity of zero air, reducing measurement errors caused by humidity. Ozone is generated by an ozone generator in a dynamic nitrogen trioxide (NO3) source synthesis module, and pressure control is more flexible via an air compressor. The pressurized environment helps the reaction equilibrium move towards N2O5 formation, prolongs the residence time in the reaction flow tube, and helps reduce NO3 wall loss. A first heating and temperature control device controls the temperature of the reaction process to ensure stability, providing stable temperature and pressure conditions for field experiments. This invention, based on a dynamic humidity calibration module, a reaction time measurement module, a dual-channel resonant cavity measurement system module, and a reaction simulation program, obtains the concentrations of NO3, dinitrogen pentoxide, and the reaction time after temperature, humidity, and equilibrium correction. Furthermore, the reaction simulation program obtains the reactivity of atmospheric NO3, thereby reducing errors.

[0013] Preferably, the dynamic humidity adjustment calibration module includes a zero-air duct and an ambient atmospheric duct, wherein the zero-air duct and the ambient atmospheric duct are connected in parallel and their outlets converge.

[0014] The zero-air pipeline is divided into two paths. One path extends into a gas washing bottle, is moistened, and then exits to merge with the other path.

[0015] Preferably, the system also includes a filter and a plurality of first mass flow meters, wherein the filter is connected to the ambient air duct, and the first mass flow meters are respectively connected to two pipes of the zero air duct and the ambient air duct.

[0016] Since the humidity difference between dry zero air and humid ambient air can cause measurement errors, this invention calibrates the humidity of the zero air first to reduce these errors.

[0017] Preferably, a second mass flow meter is connected to the NO standard gas pipeline, and a third mass flow meter is connected to the high-purity air pipeline.

[0018] Preferably, the ozone generator includes a mercury lamp device, a circulating gas pipeline, and a vacuum pump; the circulating gas pipeline is connected to the inside of the mercury lamp device in a loop, the vacuum pump is connected to the circulating gas pipeline, and the circulating gas pipeline is provided with a circulating gas inlet and a circulating gas outlet.

[0019] Preferably, the ozone generator further includes a second heating and temperature control device and a fan. Part of the circulating gas pipe is spiral-shaped and located in the second heating and temperature control device. The fan is connected to the second heating and temperature control device. A temperature measuring device is installed inside the mercury lamp device and is connected to the second heating and temperature control device.

[0020] The pressure inside the reaction flow tube is controlled in real time by using an oil-free scroll air compressor, a small orifice, and a pressure gauge. Finally, with the cooperation of a second heating and temperature control device and a circulating gas pipeline, N2O5 is pyrolyzed into NO3 under stable temperature and pressure conditions, ensuring the stability of NO3 and forming the basis for the field experimental conditions.

[0021] Preferably, the reaction time measurement module includes a conical air inlet module, a reaction chamber module, an air outlet module, and a sampling tube; the small end of the conical air inlet module is an air inlet for a mixture of ambient air and nitrogen trioxide, the large end of the conical air inlet module is connected to the reaction chamber module, the air outlet module is connected to the other end of the reaction chamber module, and the sampling tube can extend movably into the reaction chamber module.

[0022] Preferably, the gas outlet module has multiple exhaust ports, the sampling tube is arranged along the central axis of the reaction chamber module, and the exhaust ports are arranged symmetrically along the horizontal plane of the sampling tube.

[0023] This invention also discloses a method for measuring the reactivity of atmospheric nitrogen trioxide, comprising the following steps:

[0024] Step S1: The dynamic stable source synthesis module for nitrogen trioxide synthesizes NO3 and N2O5 in real time and releases them stably;

[0025] Step S2: In the dynamic humidity adjustment calibration module, obtain the relative humidity of the sampled atmosphere; humidify a portion of the zero air, then combine the humidified zero air and dynamically adjust the proportion of the humidified zero air in the total zero air to obtain zero air with the same humidity as the sampled gas.

[0026] Step S3: The two gases from the nitrogen trioxide dynamic stable source synthesis module and the dynamic humidity adjustment calibration module are mixed and then enter the reaction time measurement module. After the reaction is completed in the reaction time measurement module, they enter the dual-channel resonant cavity measurement system module. The wall loss coefficient and reaction residence time t are obtained through the reaction simulation program.

[0027] Step S4: In the dual-channel resonant cavity measurement system module, the measured NO3 concentration is obtained by switching between ambient air and humidified zero air, and the atmospheric nitrogen trioxide reactivity is calculated.

[0028] Preferably, in step S4, in the dual-channel resonant cavity measurement system module, the intensity of transmitted light after multiple reflections by a photomultiplier tube (PMT) within the high-precision cavity is collected and fitted to obtain the ring-down time τ. The concentration is then calculated based on the ring-down time with and without the target gas in the cavity. The measured NO3 concentration is recorded as follows by switching between ambient air and humidified zero air: and

[0029] Through formula By combining the reaction simulation program with corrections, the reactivity of atmospheric nitrogen trioxide was calculated.

[0030] The advantages of this invention are:

[0031] This invention uses a dynamic humidity calibration module to calibrate the humidity of zero air, reducing measurement errors caused by humidity. Ozone is generated by an ozone generator in a dynamic nitrogen trioxide (NO3) source synthesis module. The pressure is more flexibly controlled by an air compressor; the pressurized environment helps the reaction equilibrium move towards N2O5 formation, prolongs the residence time in the reaction flow tube, and helps reduce NO3 wall loss. The first heating and temperature control device controls the temperature of the reaction process to ensure stability, providing the necessary temperature and pressure conditions for field experiments. This invention, based on the dynamic humidity calibration module, reaction time measurement module, and dual-channel resonant cavity measurement system module combined with a reaction simulation program, obtains the concentrations of NO3, dinitrogen pentoxide, and the reaction time after temperature, humidity, and equilibrium correction. Furthermore, the reaction simulation program obtains the reactivity of atmospheric NO3, further reducing errors.

[0032] Since the humidity difference between dry zero air and humid ambient air can cause measurement errors, this invention calibrates the humidity of the zero air first to reduce these errors.

[0033] The pressure inside the reaction flow tube is controlled in real time by using an oil-free scroll air compressor, a small orifice, and a pressure gauge. Finally, with the cooperation of a second heating and temperature control device and a circulating gas pipeline, N2O5 is pyrolyzed into NO3 under stable temperature and pressure conditions, ensuring the stability of NO3 and forming the basis for the field experimental conditions.

[0034] The system of this invention is simple to operate and can directly obtain the concentrations of nitrogen trioxide and dinitrogen pentoxide in the ambient atmosphere, as well as the reactivity of nitrogen trioxide in the ambient atmosphere. It can be used to assess the nocturnal chemical reactivity of the troposphere and has good application prospects.

[0035] The method for measuring the reactivity of atmospheric nitrogen trioxide provided by this invention is easy to operate, and has high measurement stability and detection sensitivity, making it widely applicable. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the ambient atmospheric nitrogen trioxide reactivity measurement system according to an embodiment of the present invention;

[0037] Figure 2 This is a schematic diagram of the dynamic humidity adjustment calibration module according to an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the nitrogen trioxide dynamic stabilization source synthesis module according to an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the ozone generator in the nitrogen trioxide dynamic stabilization source synthesis module of this invention.

[0040] Figure 5 This is a schematic diagram of the reaction time measurement module according to an embodiment of the present invention;

[0041] Numbering on the map:

[0042] 1. Dynamic humidity calibration module; 11. Gas scrubbing bottle; 12. Filter; 13. Temperature and humidity sensor; 14. First mass flow meter;

[0043] 2. Module for synthesizing a dynamically stable source of nitrogen trioxide;

[0044] 21. NO standard gas pipeline; 211. Second mass flow meter; 22. High-purity air pipeline; 221. Third mass flow meter;

[0045] 23. Ozone generator; 231. Mercury lamp device; 2311. Synthetic ozone outlet; 232. Circulating gas pipeline; 2321. Circulating gas inlet; 2322. Circulating gas outlet; 233. Secondary heating and temperature control device; 234. Fan; 235. Vacuum pump;

[0046] 24. Air compressor; 25. Reaction flow tube; 26. Pressure gauge; 27. First heating and temperature control device; 28. Gas outlet pipe of the nitrogen trioxide synthesis mixer;

[0047] 3. Reaction time measurement module; 31. Conical air inlet module; 32. Reaction chamber module; 33. Air outlet module; 34. Sampling tube;

[0048] 4. Dual-channel resonant cavity measurement system module. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0050] Example 1:

[0051] like Figure 1 As shown, the atmospheric nitrogen trioxide transport efficiency calibration and reactivity measurement system includes a dynamic humidity adjustment calibration module 1, a nitrogen trioxide dynamic stable source synthesis module 2, a reaction time measurement module 3, and a dual-channel resonant cavity measurement system module 4. The dynamic humidity adjustment calibration module 1 and the nitrogen trioxide dynamic stable source synthesis module 2 are connected in parallel, and after they are combined, they are connected to the reaction time measurement module 3. The outlet end of the reaction time measurement module 3 is connected to the dual-channel resonant cavity test system module 4.

[0052] Combination Figure 2 As shown, the dynamic humidity adjustment calibration module 1 is used to adjust the humidity of the zero air and ambient air. Specifically, the dynamic humidity adjustment calibration module 1 includes two pipelines: a zero air pipeline and an ambient atmosphere pipeline. The zero air pipeline is used to introduce zero air, and the ambient atmosphere pipeline is used to introduce ambient air.

[0053] A gas scrubbing bottle 11 is installed on the zero-air pipeline. The zero-air inlet is divided into two paths: one path enters the gas scrubbing bottle 11, while the other path does not pass through the gas scrubbing bottle 11. Finally, the two paths of zero-air converge. The gas scrubbing bottle 11 on the zero-air pipeline is used to humidify the zero-air.

[0054] A filter 12 is installed on the pipeline that leads to the ambient air to filter impurities in the ambient air.

[0055] The dynamic humidity adjustment calibration module 1 also includes a temperature and humidity sensor 13 and three first mass flow meters 14. The temperature and humidity sensor 13 can be installed at the rear end of the ambient air pipeline and the zero-air pipeline to measure the humidity of the ambient air, facilitating the adjustment of the zero-air humidity. One of the first mass flow meters 14 is installed at the port where the zero-air enters the gas scrubbing bottle 11 to control the mass of air entering the gas scrubbing bottle 11. Specifically, ambient air is introduced into the ambient air pipeline, and the relative humidity of the environment is detected by the temperature and humidity sensor 13, thereby controlling the mass of zero air entering the gas scrubbing bottle 11. A portion of the zero air passes through the gas scrubbing bottle 11, while a portion does not. The gas scrubbing bottle 11 is filled with 2L of high-performance liquid chromatography-grade water to humidify the zero air. The proportion of zero air passing through the gas scrubbing bottle 11 in the total zero-air flow is dynamically adjusted by the first mass flow meter 14 to obtain zero air with the same humidity as the ambient air. A second mass flow meter 14' is installed on the pipeline that does not pass through the gas scrubbing bottle 11, and a third first mass flow meter 14 is also installed on the ambient air pipeline.

[0056] This is because this embodiment ultimately requires measuring the concentration of NO3 after mixing dry air with NO3, as well as the concentration of NO3 after mixing ambient air with NO3, to calculate the reaction activity. However, the humidity difference between dry dry air and humid ambient air can introduce measurement errors. Therefore, the humidity of the dry air needs to be calibrated beforehand to reduce these errors.

[0057] like Figure 3 As shown, the nitrogen trioxide dynamic stable source synthesis module 2 includes a NO standard gas pipeline 21, a high-purity air pipeline 22, an ozone generator 23, an air compressor 24, a reaction flow pipe 25, a pressure gauge 26, a first heating and temperature control device 27, and a nitrogen trioxide synthesis mixer outlet pipe 28.

[0058] A high-purity air duct 22 connects to an ozone generator 23, which in turn connects to an air compressor 24. A NO standard gas duct 21 connects to the outlet duct of the air compressor 24. A mixture of NO standard gas and ozone enters the reaction flow tube 25 via this duct. A pressure gauge 26 is connected to the reaction flow tube 25. A first heating and temperature control device 27 includes a heating wire and a temperature controller. The heating wire is wrapped around the outside of the reaction flow tube 25 and the outlet pipe 28 of the nitrogen trioxide mixer. The temperature controller is connected to the heating wire and used to control the heating temperature. There can be two first heating and temperature control devices 27, one for controlling the reaction flow tube 25 and the other for controlling the outlet pipe 28 of the nitrogen trioxide mixer. The outlet end of the reaction flow tube 25 is connected to the outlet pipe 28 of the nitrogen trioxide mixer.

[0059] Specifically, a second mass flow meter 211 and a third mass flow meter 221 are connected to the NO standard gas pipeline 21 and the high-purity air pipeline 22, respectively, to control the flow rates of the NO standard gas and the high-purity air. The high-purity air enters the ozone generator 23 through the high-purity air pipeline 22, producing ozone (O3). The ozone is pressurized by the air compressor 24 and then mixed with the NO standard gas. The mixed gas enters the reaction flow pipe 25, where the O3 produced by the ozone generator 23 reacts with NO through the reactions NO + O3 → NO2 + O2, NO2 + O3 → NO3 + O2, and NO3 + NO2 → N2O5, generating a mixture of NO3 and N2O5 containing small amounts of NO2 and O3. This NO3 and N2O5 mixture is then pyrolyzed to convert into NO3, and subsequently diluted by mixing with the ambient atmosphere containing reactive gases. By using a method of pyrolysis followed by dilution, the NO2 level in the mixed gas can be reduced while ensuring the concentration of synthesized NO3.

[0060] like Figure 4 As shown, in this embodiment, the ozone generator 23 includes a mercury lamp device 231, a circulating gas pipeline 232, a second heating and temperature control device 233, a fan 234, and a vacuum pump 235. One end of the mercury lamp device 231 is connected to a high-purity air pipeline 22, and the other end is connected to a synthetic ozone outlet 2311. A mercury lamp is installed inside the mercury lamp device 231, and a rotatable light shield is connected to the outside of the mercury lamp. The circulating gas pipeline 232 passes through the mercury lamp device 231 and controls the temperature of the mercury lamp device 231. Part of the circulating gas pipeline 232 is spiral-shaped and located inside the second heating and temperature control device 233. The second heating and temperature control device 233 can heat the circulating gas pipeline 232 and is connected to a temperature measuring device. The temperature measuring device is connected inside the mercury lamp device 231 to measure the temperature inside the mercury lamp device 231. The second heating and temperature control device 233 can be a box-type structure, with heating elements connected inside the box, and the circulating gas in the circulating gas pipeline 232 is heated by electric heating or other means. A fan 234 is also connected to the housing of the second heating and temperature control device 233. The fan 234 can cool the circulating air pipe 232 inside the housing, which is also for temperature regulation. A vacuum pump 235 is connected to the circulating air pipe 232 to circulate the circulating air. The circulating air pipe 232 is provided with a circulating air inlet 2321 and a circulating air outlet 2322.

[0061] The high-purity air enters the mercury lamp device 231 of the ozone generator 23 through the high-purity air pipe 22. Ozone is generated under the 185nm ultraviolet light of the mercury lamp. With a fixed high-purity air flow rate, the ozone generation rate is altered by adjusting the rotating light-shielding cover to change the shading area; a smaller shading area results in a higher ozone concentration, and vice versa. The circulating air is temperature-controlled by a fan 234 and a second heating and temperature control device 233. The temperature of ozone synthesis is controlled through heat transfer between the circulating air and the mercury lamp. This is because the mercury lamp releases heat during operation, and temperature stability affects the concentration stability of the NO3 synthesis reactant, O3. Therefore, temperature control within the mercury lamp device 231 is necessary to ensure and regulate ozone concentration, and further ensure the stability of the synthesized NO3 concentration.

[0062] In this embodiment, the circulating gas is powered by a vacuum pump 235 to drive its flow. The circulating gas is ambient air used for heat exchange with the mercury lamp. The circulating gas inlet 2321 replenishes the circulating gas and balances the pressure. After heat exchange with the mercury lamp, the circulating gas is discharged from the circulating gas outlet 2322. When the temperature is low, the fan 234 stops rotating, and the heating device heats the circulating gas, which then transfers heat to the mercury lamp. When the temperature is high, the fan 234 starts rotating to cool the circulating gas, thereby lowering the mercury lamp temperature.

[0063] In this embodiment, as Figure 3 As shown, combined with Figure 4 As shown, the synthesized ozone enters the air compressor 24 through the synthesized ozone outlet 2311. In this embodiment, the air compressor 24 is an oil-free scroll air compressor. The ozone is pressurized in the air compressor 24 and mixed with the NO standard gas introduced into the NO standard gas pipeline 21. The flow ratio is controlled by the second mass flow meter 211 and the third mass flow meter 221.

[0064] In this embodiment, the outlet pressure plate of the reaction flow tube 25 is provided with a small hole with a diameter of 5mm. An oil-free scroll air compressor allows for more flexible pressure control. The pressurized environment helps the reaction equilibrium move towards the formation of N2O5, prolongs the residence time within the reaction flow tube 25, and helps reduce NO3 wall loss. In this embodiment, the pressure within the reaction flow tube 25 is controlled in real time using an oil-free scroll air compressor, the small hole, and a pressure gauge 26. Finally, the second heating and temperature control device 233, under stable temperature and pressure conditions, pyrolyzes N2O5 into NO3, ensuring the stability of NO3 and forming the basis for the field experimental conditions.

[0065] like Figure 5As shown, the reaction time measurement module 3 includes a conical air inlet module 31, a reaction chamber module 32, an air outlet module 33, and a sampling tube 34. The small end of the conical air inlet module 31 is the air inlet for a mixture of ambient air and nitrogen trioxide. The large end of the conical air inlet module 31 is connected to the reaction chamber module 32 by bolts. The other end of the air outlet module 33 is connected to the reaction chamber module 32 by bolts. The sampling tube 34 passes through the air outlet module 33 and extends into the reaction chamber module 32. The length of the sampling tube 34 is adjustable.

[0066] The exhaust module 33 has exhaust ports located symmetrically on both sides of the sampling tube 34, and the sampling tube 34 is fixed with a stainless steel tube. This design allows the "dead volume" formed during the gas extraction process to be discharged through the exhaust ports, making the flow field more stable during the reaction process and ensuring that the sampling port is always at the same horizontal centerline position as the reaction flow tube 25, thereby reducing losses during the measurement process.

[0067] The ambient air, after humidity adjustment, reacts with the synthesized stable concentration of NO3 in the conical air inlet module 31 of the reaction time measurement module 3. The reaction occurs in the reaction chamber module 32. The residence time in the reaction chamber module 32 is adjusted by adjusting the position of the sampling tube 34. The longer the sampling tube 34 is inserted into the reaction chamber module 32, the shorter the residence time, and vice versa.

[0068] In this embodiment, the dual-channel resonant cavity measurement system module 4 is existing technology, including a laser, optical isolator, reflector, 50 / 50 beam splitter, high-reflectivity mirror, a high-precision cavity connected to the flow tube for measuring NO3 and N2O5 concentrations, heating and temperature control device, photomultiplier tube, acquisition card, acquisition program, reaction simulation and data processing program, as well as NO standard gas, NO burette, FeSO4 purification tube, mass flow meter, and other devices. The gas flow rate is controlled by the mass flow meter. The heating and temperature control device is used to pyrolyze N2O5 and keep the cavity warm. The cavity structure adopts a cage structure, and stainless steel clamps are added to improve the thermal stability of the cavity.

[0069] In module 4 of the dual-channel resonant cavity measurement system, the intensity of transmitted light after multiple reflections by a photomultiplier tube (PMT) within the high-precision cavity is collected and fitted to obtain the ring-down time τ. The concentration is then calculated based on the ring-down time with and without the analyte gas in the cavity. The measured NO3 concentration is denoted as [NO3] by switching between ambient air and humidified zero air. t Amb and Through formula By combining the reaction simulation program with corrections, the reactivity of atmospheric nitrogen trioxide was calculated.

[0070] This embodiment uses a dynamic stable nitrogen trioxide source synthesis module 2 and a dual-channel resonant cavity measurement system module 4 to calibrate the transmission efficiency under field experimental conditions. Based on a dynamic humidity adjustment calibration module, a reaction time measurement module, and a dual-channel resonant cavity measurement system module, combined with a reaction simulation program, it obtains the concentrations of nitrogen trioxide and dinitrogen pentoxide after temperature, humidity, and equilibrium correction, as well as the reaction time. Furthermore, the reaction simulation program is used to obtain the reactivity of atmospheric nitrogen trioxide. In addition, this embodiment's system is simple to operate and can directly obtain the concentrations of atmospheric nitrogen trioxide and dinitrogen pentoxide, as well as the reactivity of atmospheric nitrogen trioxide. It can be used to assess the nocturnal chemical reactivity of the troposphere, showing promising application prospects.

[0071] Example 2:

[0072] A method for measuring the reactivity of atmospheric nitrogen trioxide, using the system described in Example 1 above, includes the following steps:

[0073] Step S1: The nitrogen trioxide dynamic stable source synthesis module 2 synthesizes NO3 and N2O5 in real time and releases them stably. The sampling transmission efficiency of the dual-channel resonant cavity measurement system module 4 under the external field experimental conditions is calibrated by the step-by-step calibration method (the method in the prior art).

[0074] Step S2: In the dynamic humidity adjustment calibration module 1, the ambient relative humidity is monitored by transmitting a small amount of sampled gas (i.e., ambient air) to the temperature and humidity sensor 13. A portion of the total zero air flow is humidified by passing through the gas scrubbing bottle 11, while a portion does not pass through the gas scrubbing bottle 11 and is then combined. By dynamically adjusting the proportion of zero air passing through the gas scrubbing bottle 11 in the total flow, zero air with the same humidity as the sampled gas is obtained.

[0075] The purpose of this step is to calculate the reaction activity by measuring both the concentration of NO3 in the dry air mixture and the concentration in the ambient air mixture. However, the humidity difference between the dry air and the ambient air can introduce measurement errors. Therefore, we need to calibrate the humidity of the dry air first to reduce these errors.

[0076] Step S3: The two gases from the nitrogen trioxide dynamic stable source synthesis module 2 and the dynamic humidity adjustment calibration module 1 are mixed and then enter the reaction time measurement module 3. After the reaction is completed in the reaction time measurement module 3, they enter the dual-channel resonant cavity measurement system module 4 for docking. The wall loss coefficient and reaction residence time t are obtained through the reaction simulation program.

[0077] Step S4: In the dual-channel resonant cavity measurement system module 4, the transmitted light intensity after multiple reflections by the high-reflection mirror inside the high-precision cavity is collected by a photomultiplier tube (PMT) and fitted to obtain the ring-down time τ. The concentration is then calculated based on the ring-down time with and without the target gas inside the cavity. The measured NO3 concentration is recorded as follows by switching between ambient air and humidified zero air: and Through formula By combining the reaction simulation program with corrections, the reactivity of atmospheric nitrogen trioxide was calculated.

[0078] The method for measuring the reactivity of atmospheric nitrogen trioxide (kNO3) provided in this embodiment is easy to operate, and has high measurement stability and detection sensitivity, making it widely applicable.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for calibrating atmospheric nitrogen trioxide transport efficiency and measuring its reactivity, characterized in that, It includes a dynamic humidity adjustment calibration module, a nitrogen trioxide dynamic stable source synthesis module, a reaction time measurement module, and a dual-channel resonant cavity measurement system module; the dynamic humidity adjustment calibration module and the nitrogen trioxide dynamic stable source synthesis module are set in parallel, and after they are combined, they are connected to the reaction time measurement module. The output end of the reaction time measurement module is connected to the dual-channel resonant cavity test system module. The nitrogen trioxide dynamic stable source synthesis module includes a NO standard gas pipeline, a high-purity air pipeline, an ozone generator, an air compressor, a reaction flow pipe, and a first heating and temperature control device; the high-purity air pipeline is connected to the ozone generator and the air compressor in sequence, and the outlet end of the air compressor is mixed with the NO standard gas pipeline and then connected to the reaction flow pipe, and the first heating and temperature control device is connected to the outside of the reaction flow pipe; The dynamic humidity adjustment calibration module includes a zero-air duct and an ambient atmospheric duct, wherein the zero-air duct and the ambient atmospheric duct are connected in parallel and their outlets converge. The zero-air pipeline is divided into two paths, one of which extends into a gas washing bottle to be moistened and then discharged to merge with the other path. The ozone generator includes a mercury lamp device, a circulating gas pipeline, and a vacuum pump; the circulating gas pipeline forms a loop connection with the inside of the mercury lamp device, the vacuum pump is connected to the circulating gas pipeline, and the circulating gas pipeline is provided with a circulating gas inlet and a circulating gas outlet. The ozone generator also includes a second heating and temperature control device and a fan. Part of the circulating gas pipe is spiral-shaped and located in the second heating and temperature control device. The fan is connected to the second heating and temperature control device. A temperature measuring device is installed inside the mercury lamp device and is connected to the second heating and temperature control device. The reaction time measurement module includes a conical air inlet module, a reaction chamber module, an air outlet module, and a sampling tube. The small end of the conical air inlet module is an air inlet for a mixture of ambient air and nitrogen trioxide. The large end of the conical air inlet module is connected to the reaction chamber module. The air outlet module is connected to the other end of the reaction chamber module. The sampling tube can be movably extended into the reaction chamber module.

2. The atmospheric nitrogen trioxide transport efficiency calibration and reactivity measurement system according to claim 1, characterized in that, It also includes a filter and multiple first mass flow meters, the filter being connected to the ambient air duct, and the first mass flow meters being connected to two pipes of the zero air duct and the ambient air duct, respectively.

3. The atmospheric nitrogen trioxide transport efficiency calibration and reactivity measurement system according to claim 1, characterized in that, A second mass flow meter is connected to the NO standard gas pipeline, and a third mass flow meter is connected to the high-purity air pipeline.

4. The atmospheric nitrogen trioxide transport efficiency calibration and reactivity measurement system according to claim 1, characterized in that, The gas outlet module has multiple exhaust ports, the sampling tube is arranged along the central axis of the reaction chamber module, and the exhaust ports are arranged symmetrically along the horizontal plane of the sampling tube.

5. A method for calibrating atmospheric nitrogen trioxide transport efficiency and measuring its reactivity, characterized in that, The atmospheric nitrogen trioxide transport efficiency calibration and reactivity measurement system according to any one of claims 1-4 includes the following steps: Step S1: The dynamic stable source synthesis module for nitrogen trioxide synthesizes NO3 and N2O5 in real time and releases them stably; Step S2: In the dynamic humidity adjustment calibration module, obtain the relative humidity of the sampled atmosphere; humidify a portion of the zero air, then combine the humidified zero air and dynamically adjust the proportion of the humidified zero air in the total zero air to obtain zero air with the same humidity as the sampled gas. Step S3: The two gases from the nitrogen trioxide dynamic stable source synthesis module and the dynamic humidity adjustment calibration module are mixed and then enter the reaction time measurement module. After the reaction is complete in the reaction time measurement module, they enter the dual-channel resonant cavity measurement system module. The wall loss coefficient and reaction residence time t are obtained through the reaction simulation program. Step S4: In the dual-channel resonant cavity measurement system module, the measured NO3 concentration is obtained by switching between ambient air and humidified zero air, and the atmospheric nitrogen trioxide reactivity is calculated.

6. The method for calibrating atmospheric nitrogen trioxide transport efficiency and measuring its reactivity according to claim 5, characterized in that, In step S4, within the dual-channel resonant cavity measurement system module, the intensity of transmitted light after multiple reflections by a photomultiplier tube (PMT) within the high-precision cavity is collected and fitted to obtain the ring-down time τ. The concentration is then calculated based on the ring-down time with and without the analyte gas within the cavity. The measured NO3 concentration is recorded as follows by switching between ambient air and humidified zero air: and ; Through formula By combining the reaction simulation program with corrections, the reactivity of atmospheric nitrogen trioxide was calculated.

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