Atmospheric sampling device for measuring reaction activity of hydroxyl radicals

Abstract

The invention discloses an atmosphere sampling device for hydroxyl radical reaction activity measurement, and relates to the technical field of atmosphere hydroxyl radical reaction activity measurement, the atmosphere sampling device comprises an OH precursor gas path, an atmosphere sample gas path and a test gas path; the OH precursor gas circuit is used for introducing zero air and comprises a zero air sample introduction pipeline, a first flow meter, an ultraviolet lamp, a water bath bottle and a second flow meter which are sequentially connected along the gas transmission direction; the atmosphere sample gas path is used for introducing an atmosphere sample or zero air and comprises an atmosphere sample introduction pipeline, a filter, a third flowmeter, a first three-way joint and a second three-way joint which are sequentially connected along the gas transmission direction; the inspection gas circuit is used for introducing standard reactive gas and comprises a standard gas sample introduction pipeline and a fourth flow meter which are sequentially connected along the gas transmission direction; the second flowmeter is connected to a bypass of the first three-way joint; the fourth flowmeter is connected to a bypass of the second three-way connector; and a sample outlet of the second three-way joint is connected to the laser flash photolysis-magnetic rotation spectrometer. The invention provides a sample introduction device for atmospheric kOH'measurement based on a laser flash photolysis method, integrates sample introduction, OH precursor generation and an inspection gas path, and is convenient for switching of a system in different modes.

Description

Technical Field

[0001] This invention relates to the technical field of atmospheric hydroxyl radical reactivity measurement, and in particular to an atmospheric sampling device for measuring hydroxyl radical reactivity. Background Technology

[0002] Hydroxyl radicals (OH) are the most important oxidizing agents in the atmosphere, and OH has high reactivity (kJ). OH ') is a key photochemical parameter, and its measurement is of great significance in the study of atmospheric chemical mechanisms, model development, and analysis of pollution causes.

[0003] Laser flash optical spectroscopy-magnetic rotation spectroscopy (LP-FRS) is a method for directly measuring atmospheric kJ / m³. OH The key method involves generating a high concentration of OH pulses within the measurement chamber through flash photolysis of precursors (ozone and water vapor system), while simultaneously introducing the atmospheric sample to be tested. Reactive components in the atmospheric sample react with OH, causing a decrease in OH concentration. Mid-infrared magnetic rotation spectroscopy is used to monitor the OH concentration signal changes in real time, recording a time-resolved OH decay curve. The decay rate k of OH caused by reactive components in the sample gas is obtained in real time by fitting the OH decay curve to the e-exponential method. This rate is then corrected by a dilution factor f to obtain the atmospheric concentration k. OH ′,k OH ′=k·f.

[0004] Current research on LP-FRS technology mainly focuses on the measurement part of the system and is committed to developing small, portable, and highly sensitive measurement devices. Examples include academic papers [Wei, et al. Time-resolved laser-flash photolysis faradayrotation spectrometer: a new tool for total OH reactivity measurement and freeradical kinetics research, Analytical Chemistry, 2020, 92, 4334-4339] and [Fang, et al. Development of a portable laser-flash photolysis faradayrotation spectrometer for measuring atmospheric total OH reactivity, Atmospheric Measurement Techniques, 2025, 18, 1243-1256], a hydroxyl radical reactivity measurement device disclosed in Chinese invention patent publication number CN109856065A, and a compact and efficient pump-probe optical system disclosed in Chinese invention patent publication number CN118758882A.

[0005] The sample introduction gas path is also a crucial component of the LP-LRS method. The LP-FRS gas path system is extremely complex, involving atmospheric sample introduction, precursor generation for the photolysis system, and gas paths for system performance testing. However, currently, there are no sample introduction devices specifically developed for the LP-FRS method; all rely on temporary gas path setups at the experimental or measurement site. Switching between functional modes requires disassembly and reconstruction, or the temporary addition of piping and valves, which is highly inconvenient. Furthermore, atmospheric sample introduction losses, trace volatiles from piping and connectors, and residues contaminated by ambient air during piping disassembly are often significant causes of instrument zero drift, chemical interference, and measurement inaccuracies. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides an atmospheric sampling device for measuring the reactivity of hydroxyl radicals. It highly integrates atmospheric sampling, OH precursor generation and test gas path, and the gas path function is easy to switch. It also has the advantage of being pollution-free.

[0007] To achieve the above objectives, the present invention adopts the following technical solution, including:

[0008] An atmospheric sample introduction device for measuring the reactivity of hydroxyl radicals includes: an OH precursor gas path, an atmospheric sample gas path, and a test gas path;

[0009] The OH precursor gas path is used to introduce zero air, and includes a zero air injection pipe, a first flow meter, an ultraviolet lamp, a water bath bottle, and a second flow meter connected in sequence along the gas transmission direction;

[0010] The atmospheric sample gas path is used to introduce atmospheric samples or zero air, and includes an atmospheric sample inlet pipe, a filter, a third flow meter, a first tee connector and a second tee connector connected in sequence along the gas transmission direction.

[0011] The test gas path is used to introduce standard reactive gas, including a standard gas inlet pipe and a fourth flow meter connected sequentially along the gas transmission direction;

[0012] The second flow meter is connected to the bypass of the first tee connector; the fourth flow meter is connected to the bypass of the second tee connector; and the sample outlet of the second tee connector is connected to a laser flash photolysis-magnetic rotation spectrometer.

[0013] Preferably, the zero air inlet pipe, atmospheric inlet pipe, and standard gas inlet pipe are Teflon pipes; the first tee connector and the second tee connector are Teflon tee compression fittings.

[0014] Preferably, after the zero air is introduced into the zero air inlet pipe, the flow rate is controlled by the first flow meter, and then ozone is generated by ultraviolet light irradiation and humidification is carried out by water bath bottle in sequence. The humidified gas containing ozone is connected to the bypass of the first tee connector after passing through the second flow meter. The second flow meter is operated in the monitoring mode to monitor the flow rate of the zero air after ozone generation and humidification in real time.

[0015] After the atmospheric sample or zero air is introduced into the atmospheric sampling pipe, the particulate matter is removed by the filter and the flow rate is controlled by the third flow meter. Then it passes through the first tee connector and the second tee connector in sequence.

[0016] After the standard reactive gas is introduced into the standard gas inlet pipeline, the flow rate is controlled by the fourth flow meter before it is connected to the bypass of the second tee connector.

[0017] The laser flash photolysis-magnetic rotation spectrometer is used to flash photolyze precursors to generate OH, and then react the OH with reactive components in standard reactive gases or atmospheric samples to measure the reactivity of OH.

[0018] Preferably, the set value of the first flow meter is less than 500 mL / min; the second flow meter operates in the monitoring mode to monitor ozone generated by light and zero air velocity after humidification in real time; the set value of the third flow meter is less than 10 L / min; and the range of the fourth flow meter does not exceed 500 mL / min.

[0019] Preferably, the ultraviolet lamp is a mercury lamp with a wavelength of 254 nm.

[0020] Preferably, the flow rate dilution factor f for measuring the atmospheric hydroxyl radical reactivity can be calculated using the following formula;

[0021]

[0022] Preferably, when the device is operating in the atmospheric hydroxyl radical reactivity measurement mode, the OH precursor gas path and the atmospheric sample gas path are opened, the OH precursor gas path is vented with zero air to generate the precursor, and the atmospheric sample gas path is vented with an atmospheric sample; the test gas path is closed, and the standard reactive gas is not allowed to be vented.

[0023] Preferably, when the device is operating in performance testing mode, the OH precursor gas path, the atmospheric sample gas path, and the test gas path are all opened. Zero air is introduced into the OH precursor gas path to generate the precursor, zero air is introduced into the atmospheric sample gas path, and standard reactive gas is introduced into the test gas path. The set value of the fourth flow meter 33 is adjusted up in sequence according to the gradient to verify the linear fitting of the kinetic reaction rate constant.

[0024] The standard chemical reaction rate constant between the standard reactive gas and OH was obtained by querying a kinetic database.

[0025] Preferably, the OH precursor gas path, atmospheric sample gas path, and test gas path are integrated inside the chassis;

[0026] Each flow meter communicates with the outside world via the communication interface on the chassis panel to set and control the flow rate;

[0027] The power supply for each flow meter and UV lamp is provided through the power interface on the chassis panel;

[0028] The control panel is equipped with an atmospheric sampling ferrule straight connector, a zero air sampling ferrule straight connector, a standard gas sampling ferrule straight connector, a sample outlet ferrule straight connector, and a water bath replenishment ferrule straight connector, which are respectively connected to the zero air sampling pipeline inlet, the atmospheric sampling pipeline inlet, the standard gas sampling pipeline inlet, the second tee connector outlet, and the water bath bottle inlet.

[0029] Preferably, all ferrule connectors are made of Teflon.

[0030] The advantages of this invention are:

[0031] (1) This invention relates to atmospheric k based on laser flash photolysis. OH The measurement provides a sample introduction device that integrates sample introduction, OH precursor generation, and test gas path, facilitating system switching between different modes.

[0032] (2) The atmospheric sampling device of the present invention for measuring the reactivity of hydroxyl radicals uses all-Teflon pipes, connectors and other accessories to reduce atmospheric sampling loss and the infiltration of unknown pollution sources, thereby reducing atmospheric KOH Interference during measurement. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the gas path structure of the atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to the present invention.

[0034] Figure 2 This is a schematic diagram of the overall atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1-OH precursor gas path, 11-including zero air, 12-zero air inlet pipe, 13-first flow meter, 14-UV lamp, 15-water bath bottle, 16-second flow meter, 2-atmospheric sample gas path, 21-atmospheric sample, 22-atmospheric inlet pipe, 23-filter, 24-third flow meter, 25-first tee connector, 26-second tee connector, 3-test gas path, 31-standard reactive gas, 32-standard gas inlet pipe, 33-fourth flow meter, 4-laser flash photolysis-magnetic rotation spectrometer, 5-chassis, 51-communication interface, 52-power interface, 53-atmospheric inlet ferrule straight connector, 54-zero air inlet ferrule straight connector, 55-standard gas inlet ferrule straight connector, 56-sample outlet ferrule straight connector, 57-water bath replenishment ferrule straight connector. Detailed Implementation

[0037] 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.

[0038] Example 1

[0039] Depend on Figure 1 As shown, this embodiment 1 provides an atmospheric sample introduction device for measuring the reactivity of hydroxyl radicals, including: OH precursor gas path 1, atmospheric sample gas path 2 and test gas path 3.

[0040] The OH precursor gas path 1 is used to introduce zero air 11, including a zero air injection pipe 12, a first flow meter 13, an ultraviolet lamp 14, a water bath bottle 15, and a second flow meter 16 connected in sequence along the gas transmission direction.

[0041] The atmospheric sample gas path 2 is used to introduce atmospheric sample 21 or zero air 11, and includes an atmospheric sample inlet pipe 22, a filter 23, a third flow meter 24, a first tee connector 25, and a second tee connector 26 connected in sequence along the gas transmission direction.

[0042] The test gas path 3 is used to introduce standard reactive gas 31, and includes a standard gas injection pipe 32 and a fourth flow meter 33 connected in sequence along the gas transmission direction.

[0043] After zero air 11 is introduced into zero air inlet pipe 12, the flow rate is controlled by the first flow meter 13, and the set value of the first flow meter 13 is less than 500 mL / min; then ozone is generated by irradiation with ultraviolet lamp 14 and humidification is carried out by water bath bottle 15. The humidified gas (precursor) containing ozone passes through the second flow meter 16 and is connected to the bypass of the first three-way connector 25; the second flow meter 16 is operated in the monitoring mode to monitor the flow rate of zero air after ozone generation by light and humidification in real time.

[0044] Atmospheric sample 21 or zero air 11 is introduced into atmospheric inlet pipe 22. After particulate matter is removed by filter 23, the flow rate is controlled by third flow meter 24. The set value of third flow meter 24 is less than 10L / min. Then it passes through first tee connector 25 and second tee connector 26 in sequence.

[0045] Standard reactive gas 31 is introduced into the standard gas inlet pipe 32, and the flow rate is controlled by the fourth flow meter 33. The range of the fourth flow meter 33 does not exceed 500 mL / min; then it is connected to the bypass of the second tee connector 26.

[0046] The sample outlet of the second three-way connector 26 is connected to a laser flash photolysis-magnetic rotation spectrometer 4 for measuring the reactivity of hydroxyl radicals. Specifically, the laser flash photolysis-magnetic rotation spectrometer 4 generates a high concentration of OH pulses within the measurement chamber by flash photolysis of the precursor (ozone and water vapor system), while simultaneously introducing the atmospheric sample 21 or standard reactive gas 31. The reactive components in the atmospheric sample 21 or standard reactive gas 31 react with OH, causing the OH concentration to decay. The OH concentration signal change is monitored in real time using mid-infrared magnetic rotation spectroscopy, and a time-resolved OH decay curve is recorded. The OH decay rate k caused by the reactive components is obtained in real time by fitting the OH decay curve with the e-exponential method. This k is then corrected by a dilution factor f to obtain the final k value. OH ',k OH = k·f.

[0047] The zero-air inlet pipe 12, atmospheric inlet pipe 22, and standard gas inlet pipe 32 are Teflon pipes. The first tee connector 25 and the second tee connector 26 are Teflon tee compression fittings. The first flow meter 13, the second flow meter 16, the third flow meter 24, and the fourth flow meter 33 are mass flow meters. The ultraviolet lamp 14 is a pen-shaped low-pressure mercury lamp with a wavelength of 254nm.

[0048] When the device is operating in the atmospheric hydroxyl radical reactivity measurement mode, OH precursor gas path 1 and atmospheric sample gas path 2 are opened. Zero air 11 is introduced into OH precursor gas path 1 to generate precursors, and atmospheric sample 21 is introduced into atmospheric sample gas path 2. Test gas path 3 is closed, and standard reactive gas 31 is not allowed to be introduced.

[0049] When the device is operating in performance testing mode, the OH precursor gas path 1, atmospheric sample gas path 2, and test gas path 3 are all opened. Zero air 11 is introduced into the OH precursor gas path 1 to generate the precursor. The atmospheric sample gas path 2 is replaced with zero air 11. Standard reactive gas 31 is introduced into the test gas path 3. The set value of the fourth flow meter 33 is gradually increased in a gradient until the measured hydroxyl radical reactivity value reaches approximately 100s. -1 And ensure that there are at least 5 measured gradient values ​​per interval for linear fitting verification of the kinetic reaction rate constant.

[0050] The standard reactive gas 31 can be an inorganic reactive standard gas such as methane, carbon monoxide, or nitric oxide, or an organic reactive standard gas such as isoprene or α-pinene. The standard chemical reaction rate constant between the standard reactive gas 31 and the hydroxyl radical can be found in the kinetic database. The performance is verified by comparing the standard chemical reaction rate constant with the linearly fitted chemical reaction rate constant. The flow rate of the standard reactive gas 31 controlled by the fourth flow meter 33 needs to be converted into volumetric flow rate according to the mass flow rate conversion coefficient.

[0051] The flow rate dilution factor f for measuring the reactivity of atmospheric hydroxyl radicals can be calculated using the following formula:

[0052]

[0053] Example 2

[0054] Depend on Figure 2 As shown, this embodiment provides an atmospheric sampling device for measuring the reactivity of hydroxyl radicals. The OH precursor gas path 1, the atmospheric sample gas path 2, and the test gas path 3 are integrated inside the device casing 5.

[0055] The first flow meter 13, the second flow meter 16, the third flow meter 24, and the fourth flow meter 33 are CS200 mass flow meters from Beijing Qixing Huachuang Company. They communicate with an external computer via the communication interface (USB interface) 51 on the front panel of the chassis 5 for flow rate setting and control. Power is supplied to each flow meter and the UV lamp 14 through the power interface 52 on the front panel of the chassis 5. The front panel of the chassis 5 is equipped with an atmospheric sample inlet ferrule straight connector 53, a zero-air inlet ferrule straight connector 54, a standard gas inlet ferrule straight connector 55, a sample outlet ferrule straight connector 56, and a water bath replenishment ferrule straight connector 57. All ferrule straight connectors are made of Teflon.

[0056] 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. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals, characterized in that, include: OH precursor gas path (1), atmospheric sample gas path (2) and test gas path (3); The OH precursor gas path (1) is used to introduce zero air (11), including a zero air injection pipe (12), a first flow meter (13), an ultraviolet lamp (14), a water bath bottle (15), and a second flow meter (16) connected in sequence along the gas transmission direction; The atmospheric sample gas path (2) is used to introduce atmospheric sample (21) or zero air (11), including an atmospheric sample inlet pipe (22), a filter (23), a third flow meter (24), a first tee connector (25), and a second tee connector (26) connected in sequence along the gas transmission direction; The test gas path (3) is used to introduce standard reactive gas (31), including a standard gas injection pipe (32) and a fourth flow meter (33) connected in sequence along the gas transmission direction; The second flow meter (16) is connected to the bypass of the first three-way connector (25); the fourth flow meter (33) is connected to the bypass of the second three-way connector (26); and the sample outlet of the second three-way connector (26) is connected to the laser flash photolysis-magnetic rotation spectrometer (4).

2. The atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 1, characterized in that, The zero air inlet pipe (12), atmospheric inlet pipe (22) and standard gas inlet pipe (32) are Teflon pipes; the first tee connector (25) and the second tee connector (26) are Teflon tee fittings.

3. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 1, characterized in that, After the zero air (11) is introduced into the zero air inlet pipe (12), the flow rate is controlled by the first flow meter (13). Then, ozone is generated by irradiation with an ultraviolet lamp (14) and humidified by a water bath bottle (15). The humidified gas containing ozone passes through the second flow meter (16) and is connected to the bypass of the first three-way connector (25). The second flow meter (16) is in the monitoring mode and is used to monitor the flow rate of the zero air after irradiation and humidification in real time. After the atmospheric sample (21) or zero air (11) is introduced into the atmospheric sampling pipe (22), the particulate matter is removed by the filter (23), and the flow rate is controlled by the third flow meter (24). Then it passes through the first three-way connector (25) and the second three-way connector (26) in sequence. After the standard reactive gas (31) is introduced into the standard gas inlet pipe (32), the flow rate is controlled by the fourth flow meter (33) and then connected to the bypass of the second three-way connector (26); The laser flash photolysis-magnetic rotation spectrometer (4) is used to flash photolyze precursors to generate OH and to react OH with reactive components in a standard reactive gas (31) or an atmospheric sample (21) to measure the reactivity of OH.

4. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 1, characterized in that, The set value of the first flow meter (13) is less than 500 mL / min; the second flow meter (16) operates in the monitoring mode to monitor ozone generated by light and zero air velocity after humidification in real time; the set value of the third flow meter (24) is less than 10 L / min; and the range of the fourth flow meter (33) does not exceed 500 mL / min.

5. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 1, characterized in that, The ultraviolet lamp (14) is a mercury lamp with a wavelength of 254nm.

6. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 1, characterized in that, The flow rate dilution factor f for measuring the reactivity of atmospheric hydroxyl radicals can be calculated using the following formula:

7. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 1, characterized in that, When the device is operating in the atmospheric hydroxyl radical reactivity measurement mode, the OH precursor gas path (1) and the atmospheric sample gas path (2) are opened. Zero air (11) is introduced into the OH precursor gas path (1) to generate the precursor, and atmospheric sample (21) is introduced into the atmospheric sample gas path (2). The test gas path (3) is closed, and the standard reactive gas (31) is not allowed to be introduced.

8. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 1, characterized in that, When the device is in performance testing mode, the OH precursor gas path (1), atmospheric sample gas path (2) and test gas path (3) are all opened. Zero air (11) is introduced into the OH precursor gas path (1) to generate the precursor. Zero air (11) is introduced into the atmospheric sample gas path (2). Standard reactive gas (31) is introduced into the test gas path (3). The set value of the fourth flow meter 33 is adjusted up in sequence according to the gradient to verify the linear fitting of the kinetic reaction rate constant. The standard chemical reaction rate constant between the standard reactive gas (31) and OH was obtained by querying a kinetic database.

9. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to any one of claims 1-8, characterized in that, The OH precursor gas path (1), atmospheric sample gas path (2), and test gas path (3) are integrated inside the chassis (5); Each flow meter communicates with the outside world through the communication interface (51) on the chassis (5) panel to set and control the flow rate; The power supply for each flow meter and UV lamp (14) is provided through the power interface (52) on the front panel of the chassis (5); The control panel (5) is equipped with an atmospheric sampling ferrule straight connector (53), a zero air sampling ferrule straight connector (54), a standard gas sampling ferrule straight connector (55), an outlet ferrule straight connector (56), and a water bath replenishment ferrule straight connector (57), which are respectively connected to the inlet of the zero air sampling pipeline (12), the inlet of the atmospheric sampling pipeline (22), the inlet of the standard gas sampling pipeline (32), the outlet of the second tee connector (26), and the inlet of the water bath bottle (15).

10. An atmospheric sampling device for measuring the reactivity of hydroxyl radicals according to claim 9, characterized in that, All ferrule connectors are made of Teflon.

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