An apparatus and method for monitoring the rate of gas transfer under windless conditions

Abstract

The application belongs to the technical field of environmental monitoring, and discloses a device and method for monitoring the gas transmission rate under windless conditions, which comprises an air outlet hole, an air inlet hole, a three-way valve, an upper columnar acrylic tube, an elevator, a fan, a headspace, a rope, a counterweight, an air isolation plate, a silica gel ring, a lower columnar acrylic tube, a sterile CH4-containing water body, an upper air outlet hole, a lower water inlet hole, a carmer peristaltic pump, a German TPU tube, a water-gas separation device and a greenhouse gas analyzer. While ensuring air tightness, the application prepares a water body containing high-concentration greenhouse gases, such as carbon dioxide (CO2), and diffuses under windless conditions. Through the diffusion time, the concentration difference of greenhouse gases in the water body before and after diffusion, the concentration difference of greenhouse gases in the headspace and the specific parameters of the acrylic tube, the greenhouse gas diffusion rate can be calculated. The results can enrich the research connotation of water body greenhouse gases and provide a basis for water body carbon emission to participate in the 'double carbon' strategic goal.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring technology, and in particular relates to a device and method for monitoring gas transmission rate under windless conditions. Background Technology

[0002] Aquatic ecosystems emit significant amounts of greenhouse gases, and the thin boundary layer formula is a commonly used method for estimating greenhouse gas emissions from water bodies. The gas transport rate in this method is a crucial parameter and has been shown to be related to wind speed. However, even under windless conditions, water bodies can release greenhouse gases into the atmosphere.

[0003] The closest existing technology can be found in CN105738161A, "An Automatic Greenhouse Gas Sampling Static Box for Water Surface". This device consists of a cylindrical static box supported by a float, a top gas sampling port, a built-in fan, and an automatic sampling turntable. It is used to collect greenhouse gas samples on open water surfaces for extended periods and simultaneously record environmental information. The fan promotes uniform gas distribution within the box, and the samples are transported to the analysis system through the needle-shaped gas sampling port.

[0004] However, this static chamber is constantly exposed to the external wind field, and changes in wind speed and chamber sway significantly affect the gas gradient, making it difficult to obtain the transmission rate for pure diffusion control under windless conditions. Furthermore, its water surface is permanently connected to the overhead space, lacking a liftable air-tight barrier structure, making it impossible to achieve instantaneous water-air separation and measure concentration differences before and after diffusion. In addition, the chamber's sealing relies on float contact, posing a high risk of leakage, and the lack of an internal water circulation and mixing pathway results in uneven water concentration along depth, limiting overall accuracy and repeatability. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides an apparatus and method for monitoring gas transport rate under windless conditions.

[0006] This invention is implemented as follows: a device for monitoring gas transport rate under windless conditions includes:

[0007] Air outlet, air inlet, three-way valve, upper cylindrical acrylic tube, elevator, fan, headspace, rope, counterweight, air baffle, silicone ring, lower cylindrical acrylic tube, sterile CH4-containing water, upper exhaust port, lower water inlet port, Camer peristaltic pump, German TPU (thermoplastic polyurethane elastomer) tube, water-air separation device, greenhouse gas analyzer.

[0008] The air outlet and inlet form a closed loop with the greenhouse gas analyzer to determine the headspace CH4 concentration before and after diffusion. A three-way valve controls whether water flow is required. The cylindrical acrylic tubes serve as containers for the gas and water; the upper and lower cylindrical acrylic tubes form the outer contour of this patented device, and their joints are sealed with hot melt adhesive. When high-concentration CH4 needs to diffuse, the lift mechanism is activated to raise both sides of the baffle plate, allowing the water surface to contact the headspace gas. After diffusion, the lift mechanism is adjusted to lower both sides of the baffle plate under the action of counterweights. After diffusion, the fan is turned on to ensure uniform mixing of the headspace gas, and then the headspace CH4 concentration is measured using the greenhouse gas analyzer. Before and after diffusion, sterile CH4-containing water is drawn into the water-gas separation device via a Kamer peristaltic pump, and finally, the CH4 concentration in the water can be measured using the greenhouse gas analyzer.

[0009] Furthermore, the rope is used to connect the elevator and the air vent, and the silicone ring is adhered to the inner wall to ensure good sealing of the air vent and prevent it from descending. The various pipes are connected using German TPU tubing.

[0010] Another object of the present invention is to provide a method for monitoring gas transport rate under windless conditions, comprising:

[0011] Step 1: Use a sterile acrylic cylindrical tube with a regular shape to connect pure water (boiled and then sealed for cooling), making its volume larger than the volume of the water to be diffused, and the liquid level higher than the upper vent 20-1. Then, aerate high concentration CH4 gas through the lower inlet 20-2. Finally, use a Camer peristaltic pump to connect the upper vent 20-1 and the lower inlet 20-2 to further mix the water, the purpose of which is to make the CH4 concentration the same at different depths.

[0012] Step 2: Use the Camer peristaltic pump again to pump the mixed sterile, high-concentration CH4 water from 20-2 through the lower inlet to the lower columnar acrylic tube. When the water surface is close to the upper vent 20-1, the water flow rate needs to be reduced so that the headspace gas can be discharged evenly and without forming bubbles.

[0013] Step 3: Open the air outlet and air inlet valves, and purge the headspace with pure N2 (99.99%) until the headspace is completely replaced by pure N2;

[0014] Step 4: When the water surface comes into contact with the air barrier, turn on the elevator to raise both sides of the air barrier, so that the water comes into contact with the overhead space, and start timing t1 = 0 (the start of diffusion time).

[0015] Step 5: After a period of diffusion, turn on the elevator to lower the sides of the air barrier, thereby isolating the water from the headspace. Simultaneously time t2 (end of diffusion time).

[0016] Step 6: Turn on the fan to mix the CH4 concentration in the headspace evenly, then connect the exhaust port and the inlet port of the greenhouse gas analyzer to measure the CH4 concentration in the headspace.

[0017] Step 7: Connect the upper vent and lower inlet of the Camer peristaltic pump to ensure that the CH4 concentration in the water is mixed evenly.

[0018] Step 8: Finally, open the upper vent valve and the valve for the Camer peristaltic pump to draw water from the bottom. Combined with the water-air separation device, the CH4 concentration in the water can be measured.

[0019] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0020] First, this technical solution addresses the challenge of accurately quantifying the migration rates of greenhouse gases (CO2, CH4, N2O) into the atmosphere under still water conditions. It proposes constructing a high-concentration dissolved gas water body within a sealed, regularly shaped acrylic diffuser. By controlling a windless, undisturbed environment, the concentration difference between the water body and the top gas phase space before and after diffusion is tracked, and the diffusion flux is inverted using the diffuser's geometric parameters. This method can rapidly assess gas exchange capacity under different temperature, salinity, or nutrient conditions in laboratory or semi-controlled field environments, laying an experimental foundation for carbon emission accounting in lakes, reservoirs, and even nearshore sea areas.

[0021] The experimental setup utilizes a high-transparency, corrosion-resistant acrylic tube (recommended diameter 10cm, effective height 50cm, wall thickness not less than 5mm). The upper end is sealed to the gas sampling chamber via a silicone rubber flange, while the lower end is fitted with a three-way valve for water sample collection and drainage. Pre-set graduations on the tube surface facilitate rapid reading of the water column height. The entire system uses… The O-ring and double-sided PTFE gasket ensure approximately 10⁻³ Pa·m³s. -1 Its airtightness prevents external air from being drawn in and avoids water loss due to evaporation, which could affect accuracy.

[0022] The measurement procedure consists of three steps: First, the target gas is introduced into degassed and purified water to achieve a dissolved concentration three to five times the atmospheric equilibrium concentration. Then, saturated water is injected into an acrylic tube and allowed to stand. Second, at multiple time points (0, 5, 10, 20 min), the volume fraction of the gas in the top gas phase is measured using a headspace analyzer, and the dissolved concentration in the water sample at the same time point is measured using a headspace extraction probe. Finally, the diffusion flux is calculated according to Fick's law. Specifically, the water volume is divided by the interface area and then by the observation time interval to obtain the contribution of water phase concentration change to the flux. The gas phase volume is then similarly divided by the interface area and the time interval to obtain the contribution of gas phase concentration change. Subtracting the latter from the former yields the net diffusion flux per unit area. This flux is then divided by the average concentration difference between the water and gas phases to obtain the apparent diffusion coefficient, thus quantifying the rate at which gas escapes from the water surface.

[0023] Compared with traditional wind tunnel or large-scale chamber experiments, this scheme has three major advantages: (1) it provides a windless and controllable static environment, which allows for the individual quantification of molecular diffusion contributions; (2) the high-airtight acrylic cylinder controls system leakage error to below 1%; and (3) the device has a simple structure, low cost, and is easy to modularize and connect in series, enabling multi-point parallel experiments and rapidly revealing the sensitive parameters of water bodies for greenhouse gas emissions. The research results can refine the carbon emission inventory of lakes and reservoirs, providing a quantitative basis for water area carbon sink management and greenhouse gas emission reduction policies under the "dual carbon" strategy.

[0024] Secondly, there are currently no mature commercial devices, either domestically or internationally, capable of stably, continuously, and quantitatively measuring the diffusion rate of greenhouse gas molecules in water under windless conditions. This invention proposes for the first time a design combining a liftable air-tight baffle with a high-tightness diffusion cavity to simulate still water surface conditions in a semi-controlled laboratory or field environment, simultaneously measuring the concentration changes of the gas and water phases before and after diffusion, thereby directly calculating the gas transport rate under windless conditions. This technical solution fills the domestic and international gap in accurate monitoring of gas transport under windless conditions and provides a new experimental method for research on greenhouse gas emissions from water bodies.

[0025] For a long time, researchers have hoped to directly measure the molecular diffusion rate at the water-air interface without wind speed interference, in order to distinguish the relative contributions of wind-generated turbulence and molecular diffusion to gas exchange. However, this need has remained unmet, mainly due to problems such as insufficient air tightness, difficulty in instantaneous interface separation, and the difficulty in eliminating water concentration gradients. This invention achieves air tightness better than 10... -3 Pa·m 3 s -1 The sealing structure and the air baffle driven by the elevator enable controllable contact and separation of the water and air interface. Combined with the peristaltic pump full water column mixing technology, the above-mentioned technical bottlenecks have been solved, and high-precision, repeatable, and long-term windless diffusion monitoring has been achieved. Attached Figure Description

[0026] Figure 1 This is a structural diagram of a device for monitoring gas transmission rate under windless conditions, provided in an embodiment of the present invention.

[0027] Figure 2 This is a diagram of a container for making high-concentration CH4 provided in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the air barrier provided in an embodiment of the present invention.

[0029] Figure 4 This is a flowchart of a method for monitoring gas transmission rate under windless conditions provided in an embodiment of the present invention;

[0030] Figure 5 This is a fitting graph of direct and indirect methane flux at different temperatures provided in an embodiment of the present invention.

[0031] In the diagram: 1. Air outlet; 2. Air inlet; 3. Three-way valve; 4. Upper cylindrical acrylic tube; 5. Lifting machine; 6. Fan; 7. Headspace; 8. Rope; 9. Counterweight; 10. Air baffle; 10-1. Hook; 10-2. Lotus leaf mark; 11. Silicone ring; 12. Lower cylindrical acrylic tube; 13. Sterile CH4-containing water; 14. Upper air outlet; 15. Lower water inlet; 16. Kamer peristaltic pump; 17. German TPU tube; 18. Water-air separation device; 19. Greenhouse gas analyzer; 20. Sterile acrylic cylindrical tube; 20-1 Upper air outlet; 20-2 Lower water inlet. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] like Figure 1 As shown, the lower cylindrical acrylic tube 12 is vertically fixed in the center of the platform of the elevator 5, and contains sterile CH4-containing water 13. Its upper end is tightly fitted to the gas barrier plate 10 through a silicone ring 11 to ensure complete isolation between the liquid and gas phases. The top of the gas barrier plate 10 is then connected to the upper cylindrical acrylic tube 4 to form an integrated diffuser. A headspace 7 is reserved at the top of the diffuser for enriching the escaping gas. The entire column assembly is suspended in the guide rail of the elevator 5 by ropes 8 and counterweights 9, which facilitates fine adjustment of the immersion depth of the cylinder and correction of verticality.

[0034] Sterile CH4-containing water 13 is injected through the lower inlet 15. A Kamer peristaltic pump 16 provides constant flow via a German TPU tube 17 for circulating replenishment or sample extraction. The same path can also be used to quickly drain the water after the experiment. The top vent 1 is connected to a water-gas separator 18, which removes residual water vapor from the mixed gas in the headspace 7 before the greenhouse gas analyzer 19 measures the changes in CO2, CH4, and N2O concentrations in real time. The air inlet 2 is connected to a three-way valve 3, which can be used to introduce inert gas for zeroing or introduce standard gas for instrument calibration. The upper exhaust vent 14 serves as a pressure release and safety overflow channel.

[0035] Fan 6 is installed on the outside of the device and can be turned on briefly before the test to expel the external stagnant gas and kept closed during the measurement to ensure windless conditions; rope 8 and counterweight 9 together form a pulley-type balancing mechanism, which allows the operator to raise and lower the column with one hand without shaking; the lever of three-way valve 3 is synchronously calibrated with the lifting machine 5 to ensure rapid switching between air intake, exhaust and measurement states and reduce human operation error.

[0036] At the start of the experiment, the high concentration of dissolved gas in the lower cylindrical acrylic tube 12 continuously diffuses into the headspace 7. As time progresses, the greenhouse gas concentration in the headspace 7 gradually increases, and the gas is transported through the outlet 1 to the water-gas separator 18 and then into the greenhouse gas analyzer 19. The concentration curve obtained is combined with the water concentration curve sampled from the lower inlet 15 to calculate the net diffusion flux per unit area. With the precise control of the water column height by the elevator 5, the elimination of wind speed interference by the fan 6, and the airtightness ensured by the silicone ring 11, the device can repeatedly measure the molecular diffusion rate from the water surface to the atmosphere under static and stable conditions for a long period of time, providing reliable data for the study of greenhouse gas migration under windless conditions.

[0037] An embodiment of the present invention provides a device for monitoring gas transport rate under windless conditions, comprising:

[0038] 1. Air outlet, 2. Air inlet, 3. Three-way valve, 4. Upper cylindrical acrylic tube, 5. Lifting machine, 6. Fan, 7. Headspace, 8. Rope, 9. Counterweight, 10. Air barrier, 11. Silicone ring, 12. Lower cylindrical acrylic tube, 13. Sterile CH4-containing water, 14. Upper exhaust port, 15. Lower water inlet, 16. Kamer peristaltic pump, 17. German TPU tube, 18. Water-air separation device, 19. Greenhouse gas analyzer.

[0039] like Figure 3The air outlet 1 and air inlet 2 form a closed loop with the greenhouse gas analyzer to determine the CH4 concentration in the headspace before and after diffusion. The three-way valve 3 is used to control whether the water needs to flow. The columnar acrylic tube 4 is a container for the gas and water. The upper columnar acrylic tube 4 and the lower columnar acrylic tube 12 are combined to form the outer contour of this patented device, and the joint is sealed with hot melt adhesive. When high concentrations of CH4 need to diffuse, the elevator 5 needs to be activated to raise the two sides of the air barrier 10 so that the water surface and the gas in the headspace 7 can come into contact. After diffusion, the elevator 5 is adjusted so that the two sides of the air barrier 7 can be lowered under the action of the counterweight 9. After diffusion, the fan 6 is turned on to mix the gas in the headspace 7 evenly, and then the CH4 concentration in the headspace is measured by the greenhouse gas analyzer 19. Before and after diffusion, the sterile CH4-containing water 13 is pumped into the water-gas separation device 18 by the Kamer peristaltic pump 16, and finally the CH4 concentration in the water can be measured by the greenhouse gas analyzer 19. Rope 8 is used to connect the elevator 5 and the air barrier 10. The silicone ring 11 is attached to the inner wall to ensure good sealing of the air barrier 10 and prevent it from descending. In addition, the pipes are connected by German TPU pipes 17.

[0040] The gas transmission monitoring device of this invention achieves accurate monitoring of gas diffusion rate under windless conditions through the synergistic effect of multiple functional components. The core of the device is a closed cavity composed of an upper cylindrical acrylic tube 4 and a lower cylindrical acrylic tube 12. The cavity is sealed with hot melt adhesive to form an airtight structure, and its interior is used to contain the water body 13 to be tested. A gas-isolating plate 10 is installed at the junction of the upper and lower tubes and is in sealed contact with a silicone ring 11, used to selectively isolate or open the contact between the water body and the headspace 7 at different stages of the experiment. A lifting mechanism 5 drives the gas-isolating plate 10 up and down via a rope 8 and a counterweight 9. During ascent, the contact interface between the water body and the headspace is opened; during descent, the seal is restored, thereby strictly controlling the time window for gas exchange.

[0041] In the gas collection and detection path, inlet 2 and outlet 1 serve as gas entry and exit channels, respectively. Outlet 1 is connected to greenhouse gas analyzer 19 via water vapor separator 18. Water vapor separator 18 removes water vapor at the detection front end, ensuring that the sample entering analyzer 19 is dry gas, thus avoiding water vapor interference with the accuracy of concentration measurement. Simultaneously, the three-way valve 3 allows for flexible switching of the gas path to achieve different operating modes such as headspace replacement, gas circulation, and detection. Fan 6 is positioned above headspace 7 to rapidly mix the gas after the baffle plate 10 descends to close the headspace, ensuring that the concentration becomes uniform within a short time, thereby improving analytical accuracy.

[0042] In the water circulation and sampling process, the lower inlet 15 connects to a Kamer peristaltic pump 16 and a German TPU tube 17. The peristaltic pump 16 drives the water circulation at a constant flow rate. Through this pathway, the water can be thoroughly mixed before the experiment to ensure the uniformity of gas concentration. Simultaneously, after the experiment, water samples are extracted, and after air bubbles are removed by a water-gas separator 18, they are transported to a greenhouse gas analyzer 19 for dissolved gas content determination. This structural design allows for the separate acquisition of headspace and water gas concentration data, thus providing dual data for transport rate calculations.

[0043] Before the experiment begins, water 13 is injected into the lower cylindrical acrylic tube 12 through the lower inlet 15 and gradually fills to near the outlet of the upper cylindrical acrylic tube 4. Then, inert gas is introduced into the headspace 7 through the inlet 2 and discharged through the three-way valve 3 and outlet 1, completing headspace displacement and ensuring that the headspace is initially free of the target gas. After the elevator 5 drives the baffle plate 10 to rise, the water 13 begins to contact the headspace 7, and the target gas dissolved in the water diffuses into the headspace. This process is carried out within a set time to ensure controlled diffusion.

[0044] After diffusion, the elevator 5 lowers the baffle plate 10 and, under the action of the counterweight 9, presses the silicone ring 11 to restore the seal, preventing further exchange. At this time, the fan 6 starts mixing the headspace gas, and the air inlet 2 and outlet 1 form a closed loop. The greenhouse gas analyzer 19 measures the change in the concentration of the target gas in the headspace. Simultaneously, the peristaltic pump 16 draws water, which passes through the TPU tube 17 and the water-gas separator 18 before entering the analyzer 19 for water concentration measurement, ensuring that data on the concentration changes of water and headspace are obtained within the same experimental cycle.

[0045] Finally, the data processing unit receives the output signal from the greenhouse gas analyzer 19 and, combined with the concentration changes in the headspace 7 and water body 13, calculates the rate of gas transport from the water body to the headspace. The entire experimental process is automated through the control unit, including the lifting and lowering of the elevator 5, the circulation of the peristaltic pump 16, the mixing of the fan 6, and the linkage of the analyzer 19. These components form a stable and controllable experimental system, making the measurement of gas transport rate more accurate and reliable in a windless environment, ensuring the repeatability and practicality of the method.

[0046] like Figure 2 As shown, in S101, a sterile acrylic columnar tube with a regular shape is connected to pure water (cooled water after boiling), making its volume larger than the volume of the water to be diffused, and the liquid level higher than the upper vent 20-1. Then, high concentration CH4 gas is aerated through the lower inlet 20-2. Finally, a Kamer peristaltic pump is used to connect the upper vent 20-1 and the lower inlet 20-2 to further mix the water, with the aim of making the CH4 concentration the same at different depths.

[0047] S102. Use the Camer peristaltic pump again to pump the mixed sterile, high-concentration CH4 water from 20-2 through the lower inlet hole to the lower columnar acrylic tube. When the water surface is close to the upper air outlet 20-1, the water flow rate needs to be reduced so that the headspace gas can be discharged evenly and without forming bubbles.

[0048] S103. Open the outlet and inlet valves and purge the headspace with pure N2 (99.99%) until the headspace is completely replaced by pure N2;

[0049] S104. When the water surface comes into contact with the air barrier, the elevator is turned on to raise both sides of the air barrier, so that the water comes into contact with the overhead space. The timing is synchronized to t1 = 0 (the start of diffusion time).

[0050] S105. After a period of diffusion, the elevator is turned on to lower the sides of the air barrier, thereby isolating the water body from the headspace. The timer t2 (end of diffusion time) is started simultaneously.

[0051] S106. Turn on the fan to mix the CH4 concentration in the headspace evenly, then connect the exhaust port and the inlet port of the greenhouse gas analyzer to measure the CH4 concentration in the headspace.

[0052] S107. Connect the upper vent and lower inlet ports with a Camer peristaltic pump to ensure uniform CH4 concentration in the water.

[0053] S108. Finally, open the upper vent valve and the valve for the Camer peristaltic pump to draw water from the bottom. Combined with the water-air separation device, the CH4 concentration in the water can be measured.

[0054] This invention can be applied to multiple fields such as greenhouse gas monitoring and carbon cycle research, and is particularly suitable for the following areas:

[0055] (1) Monitoring of greenhouse gas emissions from water bodies: Measurement of the diffusion rates of greenhouse gases such as CO2, CH4, and N2O in lakes, reservoirs, ponds, wetlands and nearshore sea areas under static and stable conditions.

[0056] (2) Scientific research on climate change and global carbon cycle: verify the water-air interface diffusion process model and boundary layer theory under windless conditions; improve the input parameters of the climate model by combining diffusion experiments under different temperature, salinity, pH and nutrient conditions.

[0057] (3) Related products and technology extensions: Modular windless diffusion monitoring kits that can be combined into multi-point parallel monitoring systems; production and sales of independent components such as airtight diffusion chambers, lifting and air-blocking devices, and peristaltic pump circulation systems; and on-site rapid detection kits that are compatible with portable greenhouse gas analyzers.

[0058] To verify the feasibility and accuracy of the device and method of the present invention in determining gas transport rate under windless conditions, the applicant conducted multiple sets of comparative experiments and obtained the following technical effects:

[0059] (1) Air tightness verification: With the elevator and air baffle closed, the device was filled with inert gas and left to stand for 24 hours. The rate of change of gas phase concentration was measured using a greenhouse gas analyzer. The results showed that the leakage rate was less than 1×10⁻⁶. -3 Pa·m 3 s -1 It is far superior to similar static surface tanks (usually in the 10...) -2 (At the level of magnitude), ensuring that the concentration change originates entirely from the interfacial diffusion process, rather than from the entrainment of external air or the escape of gas.

[0060] (2) Verification of water concentration uniformity: The Kamer peristaltic pump was used to circulate and mix the entire water column before and after water injection, and CH4 concentration was sampled and analyzed at different depths (0cm, 10cm, 20cm, 30cm). The concentration difference was less than ±2%, which proved that the device can effectively eliminate the vertical concentration gradient, thereby avoiding calculation errors caused by uneven water phase mixing.

[0061] (3) Verification of detectability of windless diffusion signal: Under laboratory conditions with an external wind speed of <0.05m / s, after a high concentration of dissolved CH4 water was brought into contact with an inert gas in the headspace, the CH4 concentration in the headspace increased from 0ppm to about 800ppm within 30 minutes. The signal intensity was significantly higher than the detection limit (<1ppm) of the greenhouse gas analyzer, proving that the present invention can obtain a stable and quantifiable diffusion concentration curve in a windless environment.

[0062] (4) Repeatability of the measurement results: The measurement was repeated 5 times under the same initial water concentration conditions, and the coefficient of variation of CH4 diffusion coefficient was less than 5%, indicating that the device has good experimental repeatability and result stability.

[0063] Figure 5 The results show a comparison of methane flux measured by the direct and indirect methods under three different temperature conditions (air temperature greater than water temperature, air temperature equal to water temperature, and air temperature less than water temperature). As can be seen from the three subplots, all points are closely distributed near the fitted straight line, and the slope of the linear relationship is close to 1, indicating that the results obtained by the two methods under different temperature backgrounds are highly consistent and have a good correlation.

[0064] When the air temperature is higher than the water temperature, the fitted equation is y = 1.0414x + 0.00004, and the coefficient of determination R0 is 1.0414x + 0.00004. 2=0.991, indicating that the direct measurement results and the indirect calculation results are almost completely consistent, and the quantification process of gas diffusion rate is less affected by temperature difference. When the air temperature and water temperature are equal, the fitting relationship is even tighter, y = 1.0409x + 0.00001, R 2 =0.996, achieving the optimal fitting effect and further verifying the reliability of the method.

[0065] When the air temperature is lower than the water temperature, the fitted equation is y = 1.0320x + 0.00006, R0 2 =0.940, although the correlation is slightly low, it is still at a high level. This indicates that the monitoring results of gas transport rate may be partially disturbed when the temperature difference is reversed, but the overall trend is still highly consistent, proving that the device and method of the present invention have stability and accuracy under different temperature conditions and can be effectively used for methane flux monitoring.

[0066] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A device for monitoring gas transport rate under windless conditions, characterized in that, include: Air outlet, air inlet, three-way valve, upper cylindrical acrylic tube, lower cylindrical acrylic tube, air baffle, silicone ring, elevator, rope, counterweight, fan, headspace, lower water inlet, peristaltic pump, elastic tube, water-gas separator and gas analyzer; The upper columnar acrylic tube is connected to the lower columnar acrylic tube and sealed with hot melt adhesive to form a closed cavity for accommodating the water to be tested. The air-separating plate is set at the connection of the two columnar acrylic tubes and is in sealed contact with the silicone ring, for selectively separating the water from the headspace. The elevator drives the air baffle to move up and down within the cavity via the rope and the counterweight; The air inlet and the air outlet form a closed loop with the gas analyzer to detect headspace gas concentration. The lower water inlet is connected to the water-air separation device via the peristaltic pump and the elastic tube, and is used to transport or extract water samples.

2. The apparatus according to claim 1, characterized in that, The air barrier can automatically fall back and restore the seal with the silicone ring under the action of the counterweight, thereby re-isolating the water body and headspace when monitoring stops.

3. The apparatus according to claim 1, characterized in that, The water vapor separation device is located at the front end of the gas analyzer, and the gas outlet, the water vapor separation device, and the gas analyzer are connected in sequence to remove water vapor and avoid affecting the accuracy of gas concentration measurement.

4. The apparatus according to claim 1, characterized in that, The peristaltic pump can drive water to circulate between the lower inlet and the headspace venting passage at a constant flow rate, thereby maintaining a uniform water concentration during sampling or venting.

5. A method for monitoring gas transport rate under windless conditions using the device described in claim 1, characterized in that, Includes the following steps: Step A: Prepare a water body with a high concentration of dissolved target greenhouse gas and inject it into the cavity through the lower water inlet until the water surface is close to the gas outlet. Step B involves introducing an inert gas to displace the headspace and create initial conditions without a target gas. Step C: Start the elevator to raise the air barrier and begin timing so that the water can come into contact with the headspace and diffuse. Step D involves lowering the baffle plate to restore the seal after the predetermined diffusion time has elapsed; Step E: After starting the fan to mix the headspace gas, the headspace concentration is measured using a gas analyzer. Step F involves using a peristaltic pump to extract water, which is then transported to a gas analyzer via a water-gas separator to determine the water concentration. Step G calculates the gas transport rate based on changes in headspace concentration and changes in water concentration.

6. The method according to claim 5, characterized in that, In step A, the water is circulated and mixed by a peristaltic pump before being injected into the cavity to ensure that the concentration of dissolved gas is uniform along the depth.

7. The method according to claim 5, characterized in that, When replacing the headspace in step B, the inert gas flow rate is set to be sufficient to completely replace the headspace gas without causing water surface ripples.

8. A gas transmission monitoring system, characterized in that, Includes the apparatus, control unit, and data processing unit as described in claim 1; The control unit is electrically connected to the elevator, the peristaltic pump, the fan, and the gas analyzer, and is used to execute the method of any one of claims 5 to 7 according to a preset program; The data processing unit is used to receive the concentration data output by the gas analyzer and calculate the gas transmission rate in real time.

9. A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, causes the processor to perform the method of any one of claims 5 to 7.

10. An information data processing terminal, characterized in that, It includes a processor, a memory, and a communication interface. The memory stores the computer program of claim 9. When the processor executes the computer program, it communicates with the gas transmission monitoring system of claim 8 and outputs the gas transmission rate result.

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