Device and method for measuring in-situ sediment water interface greenhouse gas emission

Abstract

The invention discloses a device and method for measuring greenhouse gas emission of an in-situ sediment water interface, the device comprises a regular cylindrical body, a balancing weight, a water pumping pipe, a rope, an in-situ water body, an overwater platform, a winch and a water suction pump, the regular cylindrical body is placed on an in-situ sediment under the in-situ water body, the balancing weight is installed on the regular cylindrical body, and the rope is connected with the water pumping pipe. The winch is connected with the regular column through a rope, and the water suction pump is communicated with the regular column through a water suction pipe. The method has the beneficial effects that the response relationship between the in-situ sediment-water interface greenhouse gas concentration and the time can be reflected; the sediment depth measurer can measure the depth of the sediment and verify whether the stainless steel regular columnar body completely covers the sediment-water interface or not; the specific scale parameters of the stainless steel regular columnar body with the regular shape are known, so that the greenhouse gas flux of the in-situ sediment water interface is favorably calculated; in a disturbed hydrological environment, the sealing performance of the device can be ensured; the method is suitable for rivers, lakes and reservoirs and is low in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water greenhouse gas emission monitoring, in particular to a device and method for measuring in-situ sediment-water interface greenhouse gas emission. BACKGROUND

[0002] According to the latest scientific assessment, the global greenhouse gas emissions of aquatic ecosystems (such as oceans, lakes, reservoirs, ponds, rivers, etc.) account for about 10-15%. With climate warming, this proportion may also rise. As an important source of greenhouse gases (mainly CO2 and CH4) in aquatic ecosystems, it is particularly important to calculate how much greenhouse gas produced by sediments can be emitted to water to evaluate the carbon cycle of aquatic ecosystems.

[0003] 1. A monitoring device for measuring sediment-water interface greenhouse gas flux is disclosed in Chinese patent (publication number: CN115078642A), which includes a support frame and a gas analyzer. The support frame is designed as a double-layer hollow nested structure. An upper transmission pipe is arranged on the upper side wall of the support frame, one end of the upper transmission pipe extends into the interior of the support frame, and the end is connected with an upper water inlet. An upper filter is arranged at the outlet of the upper water inlet, and the other end of the upper transmission pipe is connected with the gas analyzer. A lower transmission pipe is arranged on the lower side wall of the support frame, one end of the lower transmission pipe extends into the interior of the support frame, and the end is connected with a lower water inlet. A lower filter is arranged at the outlet of the lower water inlet, and the other end of the lower transmission pipe is connected with the gas analyzer.

[0004] The device has the following defects: the device adopts a "double-layer hollow nested support frame" structure and is not equipped with any sediment depth measurement or interface coverage verification component. In actual monitoring, it is impossible to confirm whether the support frame completely fits and covers the sediment-water interface (such as the possibility of covering only the water body without contacting the sediment due to insufficient depth of the support frame, or disturbing the sediment due to excessive depth of the support frame), which directly causes the monitoring area to deviate from the "true in-situ interface", and the data representativeness is seriously insufficient.

[0005] Greenhouse gas flux calculation needs to rely on core parameters such as "fixed area of monitoring area" and "internal space volume", but the device does not clearly indicate the "regular shape" and "precise scale parameters" (such as inner diameter and height) of the internal space of the support frame. For example, if the support frame is a non-regular hollow structure, its cross-sectional area is difficult to accurately quantify, which leads to a large error in subsequent flux calculation (flux = concentration change x volume ÷ time ÷ area), and the in-situ emission rate cannot be accurately reflected.

[0006] 2. Collection device and determination method for determining contribution of endogenous greenhouse gas emission in shallow water body (publication number: CN113358426B). The collection device comprises a bottom ring, a plurality of intermediate parts are threadedly connected to the bottom ring, a top ring is threadedly connected to the topmost intermediate part, a water inlet and outlet is formed in the middle of each of the plurality of intermediate parts, a sealing cover plate is arranged at the position corresponding to the water inlet and outlet, and a spring is arranged between the sealing cover plate and the intermediate part. Through the arrangement of the intermediate part, the top ring and the bottom ring, and under the joint action of the inner thread and the outer thread, the intermediate part, the top ring and the bottom ring can form a box body with a height meeting the sampling environment and requirements. The greenhouse gases generated by the water body, the water-gas interface, the sediment and the water body can be collected respectively, and the contribution value of the water-gas interface greenhouse gas emission can be calculated by using a calculation formula. The structure is simple, stable and can be disassembled and carried, and the use is convenient.

[0007] The device has the following defects: the monitoring box body is formed by assembling the bottom ring, the intermediate part and the top ring, although the height can be adjusted, the assembly process relies on manual splicing, and the fitting degree of the box body and the sediment interface is easily affected by water flow and sediment disturbance (for example, water flow in shallow water area easily causes the box body to deviate, and the bottom ring cannot completely fit the surface of the sediment). In essence, it still belongs to "simulation in-situ monitoring in controllable environment", rather than "in-situ monitoring in real natural water body", and cannot accurately reflect the natural gas release condition of the sediment; There is no sediment depth measurement function, and it is impossible to verify whether the assembled box body completely covers the sediment-water interface, which may cause the monitoring data to contain the gas signals of the non-target interface (such as only monitoring the water body without covering the surface layer of the sediment); The internal space shape of the assembled box body is affected by the "intermediate part splicing accuracy" (such as irregular shape caused by splicing gap), and the scale parameter (such as cross-sectional area) is not fixed, so the subsequent flux calculation result deviation can be more than 20% (refer to the accurate calculation logic reverse deduction of the regular columnar body of the invention), which cannot meet the accurate monitoring requirement.

[0008] Although it is emphasized that it can be disassembled and carried, but in the field application, the connection of the bottom ring and the intermediate part needs to be adjusted many times (such as thread tightening, sealing inspection), which is extremely difficult to operate in flowing water body or soft sediment area - not only easy to destroy the in-situ environment due to assembly delay (such as disturbing the sediment to cause the gas to release in advance), but also may cause the external water body to mix due to the sealing not being tight, further polluting the monitoring sample.

[0009] However, at present, most of the devices for studying sediment greenhouse gas are used for simulation in-situ monitoring rather than in-situ monitoring, so this cannot accurately reflect the in-situ sediment-water interface greenhouse gas release condition.

[0010] The CO2 / CH4 flux calculation formula is as follows:

[0011] F = (C2 - C1) * V * A * M / (T2 - T1) -2 h -1 ), C1 and C2 are CO2 / CH4 concentrations (umol L -1 ), V is the corresponding water volume (L), A is the inner surface area of the device (m 2 ), T1 and T2 are the time before and after monitoring (h). M is the molar mass of CO2 / CH4.

[0012] Therefore, in view of the above technical problems, it is necessary to provide a simple device and method for measuring in-situ sediment-water interface greenhouse gas emissions: the present application can ensure the sealing of the device in a disturbed hydrological environment, and the scientific and reasonable design can realize the accurate measurement of the greenhouse gas emission flux of the sediment-water interface. SUMMARY

[0013] The purpose of the present application is to provide a simple device and method for measuring in-situ sediment-water interface greenhouse gas emissions: the present application can ensure the sealing of the device in a disturbed hydrological environment, and the scientific and reasonable design can realize the accurate measurement of the greenhouse gas emission flux of the sediment-water interface.

[0014] In order to solve the above technical problems, the present application provides the following technical scheme: A device for measuring in-situ sediment-water interface greenhouse gas emissions, comprising a regular columnar body, a counterweight, a water pumping pipe, a rope, an in-situ water body, a water platform, a winch and a water pump, the regular columnar body is placed on the in-situ sediment under the in-situ water body, the counterweight is installed on the regular columnar body, the water platform floats on the in-situ water body, the winch and the water pump are installed on the water platform, the winch is connected with the regular columnar body through the rope, and the water pump is communicated with the regular columnar body through the water pumping pipe.

[0015] Preferably, the regular columnar body is provided with a water inlet and a water outlet.

[0016] Preferably, the water inlet is inclined upward.

[0017] Preferably, the water outlet is communicated with the water pumping pipe.

[0018] Preferably, the regular columnar body is a stainless steel tank.

[0019] Preferably, the inner diameter of the columnar body is 50 cm, the water inlet is inclined by 30-45°, and the device is completely placed in water (there is no air in the device).

[0020] Preferably, the counterweight is a lead block.

[0021] A method for determining greenhouse gas emissions at the water interface of in-situ sediments, comprising the following steps: S1. On the water platform, first put the assembled regular column with rope and counterweight and the water pipe into the water, so that there is no air inside the regular column and it is in a vertical state. S2. Turn on the power of the winch and let the regularly shaped stainless steel column with the counterweight descend vertically and slowly, while simultaneously lowering the water pipe until the rope is no longer vertical (indicating that the device has reached the bottom of the water), then turn off the winch. S3. Let it stand for a period of time, turn on the power of the water pump (start timing at this moment), and after the water without bubbles comes up, use the water vapor separation device to separate water vapor, and then use the greenhouse gas analyzer to measure the concentration of greenhouse gases in the water. After the measurement is completed, turn off the water pump. S4. After a specific period of time, turn the power to the water pump back on (start another timer at this point), and then repeat the greenhouse gas monitoring operation in S3. S5. Based on the concentration at the water interface of the in-situ sediments before and after two separate in-situ sediment tests, the time interval, and the inner diameter of the regularly shaped columnar sediment, the greenhouse gas generation rate at the water interface of the in-situ sediments can be calculated.

[0022] Preferably, a sediment depth measuring device is installed inside the regular columnar body, and the water-gas separation device, greenhouse gas analyzer, and sediment depth measuring device are all connected to the measurement and control module.

[0023] Preferably, the sediment depth measuring device is an ultrasonic sensor to ensure that the detected sediment depth must be >5cm.

[0024] Beneficial effects of this invention: 1. This invention can reflect the response relationship between greenhouse gas concentration at the in-situ sediment-water interface and time; 2. The sediment depth measuring instrument of the present invention can measure the sediment depth and verify whether the stainless steel regular columnar body completely covers the sediment-water interface; 3. The present invention uses a regularly shaped stainless steel column with known specific dimensional parameters, which is beneficial for calculating the greenhouse gas flux at the in-situ sediment-water interface.

[0025] 4. This invention can ensure the airtightness of the device in disturbed hydrological environments; applicable scenarios (rivers, lakes, reservoirs, etc.), low cost (<5000 yuan / set) Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Fig. 1 This is a schematic diagram of the overall structure of the present invention; Fig. 2 This is a schematic diagram of the regular columnar structure of the present invention; Fig. 3 This is a block diagram of the measurement and control module of the present invention; Fig. 4 This is a flow chart of CO2 / CH4 throughput according to the present invention.

[0028] The attached figures are labeled as follows: 1. In-situ sediment; 2. Regular columnar body; 201. Inlet; 202. Outlet; 203. Sediment depth measuring device; 3. Counterweight; 4. Pumping pipe; 5. Rope; 6. In-situ water body; 7. Floating platform; 8. Winch; 9. Pump; 10. Water-gas separator; 11. Greenhouse gas analyzer; 12. Measurement and control module. Detailed Implementation

[0029] 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 with reference to the accompanying drawings. 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.

[0030] like Figs. 1 to 4 As shown, one embodiment of the present invention is provided: An apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments includes a regular column 2, a counterweight 3, a pumping pipe 4, a rope 5, an in-situ water body 6, a floating platform 7, a winch 8, and a pump 9. The regular column 2 is placed on in-situ sediments 1 below the in-situ water body 6. The counterweight 3 is installed on the regular column 2. The floating platform 7 floats on the in-situ water body 6. The winch 8 and the pump 9 are installed on the floating platform 7. The winch 8 is connected to the regular column 2 via the rope 5, and the pump 9 is connected to the regular column 2 via the pumping pipe 4.

[0031] Furthermore, the regular columnar body 2 is provided with an inlet 201 and an outlet 202.

[0032] Furthermore, the water inlet 201 is inclined upwards.

[0033] Furthermore, the outlet 202 is connected to the pumping pipe 4.

[0034] Furthermore, the regular columnar body 2 is made of stainless steel.

[0035] Furthermore, the inner diameter of the column is 50cm, and the water inlet is tilted at 30-45° to ensure that the device is completely submerged in water (there must be no air inside the device).

[0036] Furthermore, the counterweight 3 is made of lead.

[0037] A method for determining greenhouse gas emissions at the water interface of in-situ sediments, comprising the following steps: S1. On the water platform 7, the assembled regular columnar body 2 with rope 5 and counterweight 3 and the water pipe 4 are first put into the water so that there is no air inside the regular columnar body 2 and it is in a vertical state. S2. Turn on the power of the winch and let the regularly shaped stainless steel column 2 with the counterweight 3 descend vertically and slowly, while simultaneously lowering the water pipe 4, until the rope 5 is no longer vertical (indicating that the device has reached the bottom of the water), then turn off the winch 8. S3. Let stand for 5-10 minutes, turn on the power of the water pump 9 (start timing at this moment), and after the water without bubbles comes up, use the water vapor separation device 10 to separate water and gas, and then use the greenhouse gas analyzer 11 to measure the concentration of greenhouse gases in the water. After the measurement is completed, turn off the water pump 9. S4. After 30-120 minutes, turn on the power to the water pump 9 again (start timing another time at this moment), and then repeat the greenhouse gas monitoring operation in S3. S5. Based on the concentration at the water interface of the in-situ sediments before and after two separate in-situ sediment tests, the time interval, and the inner diameter of the regularly shaped columnar sediment, the greenhouse gas generation rate at the water interface of the in-situ sediments can be calculated.

[0038] Furthermore, a sediment depth measuring device 203 is installed inside the regular columnar body 2, and the water-gas separation device 10, greenhouse gas analyzer 11, and sediment depth measuring device 203 are all connected to the measurement and control module 12.

[0039] Furthermore, the sediment depth measuring device 203 is an ultrasonic sensor, ensuring that the detected sediment depth must be 5 cm. The device includes a sediment depth measuring device 203 (ultrasonic, 40 kHz), a water-gas separation device 10 (water-gas separation efficiency >95%), and a greenhouse gas analyzer (accuracy, 0.01 ppm).

[0040] Beneficial effects of this invention: 1. This invention can reflect the response relationship between greenhouse gas concentration at the water interface of in-situ sediments and time; 2. The sediment depth measuring device 203 of the present invention can measure the sediment depth and verify whether the stainless steel regular columnar body completely covers the sediment-water interface; 3. The present invention uses regularly shaped stainless steel columnar bodies with known specific dimensional parameters, which is beneficial for calculating the greenhouse gas flux at the in-situ sediment-water interface.

[0041] 4. In disturbed hydrological environments, the present invention can ensure the airtightness of the device; applicable scenarios (rivers, lakes, reservoirs, etc.), low cost (<5000 yuan / set).

[0042] The steps for drawing the flux quantization formula and calculating flux are as follows: S21. Collect / determine all parameters required for the formula; S22. Verify the consistency of parameter units; S23. Calculate the concentration difference and time difference; S24. Substitute into the formula to calculate the flux F; S25. Result verification and correction; S26. Output the final result.

[0043] The in-situ sediment 1 produces gases such as CO2 and CH4. The regularly shaped stainless steel column 2 is lowered and opened. When inserted into the in-situ sediment 1, it will completely cover a sediment-water interface area with a fixed area. The inlet 201 is used for water intake during pumping. It is tilted upward to prevent large-volume impurities from entering the monitoring system. The outlet 202 is the water pumping channel during monitoring. The sediment depth measuring device 203 is used to measure the sediment depth and to ultimately verify whether the regularly shaped stainless steel column 2 completely covers the sediment-water interface. The counterweight 3 ensures that the regularly shaped stainless steel column 2 can move vertically downward. The pumping pipe 4 is used to connect the outlet 202 and the pumping pump 9. One end of the rope 5 is fixed directly above the regularly shaped stainless steel column 2, and the other end is connected to the winch 8. The floating platform 7 is used for operation and placement of monitoring equipment such as the winch 8 and the pumping pump 9.

[0044] This technical solution ensures that the regularly shaped stainless steel columnar body can completely cover a fixed area of ​​sediment-water interface and form a closed space with it. At the same time, it measures the concentration of greenhouse gases in the water and the size of the regularly shaped stainless steel columnar body by pumping water at a fixed time on the water platform, and then calculates the greenhouse gas flux at the sediment-water interface in situ. This will provide strong data support for the carbon cycle of water bodies.

[0045] The inlet 201 is tilted upward to prevent large impurities from entering the monitoring system. The outlet 202 is the pumping channel during monitoring. The sediment depth measuring instrument 203 is used to measure the sediment depth and to ultimately verify whether the regularly shaped stainless steel column 2 completely covers the sediment-water interface.

[0046] The concentrations of dissolved CH4 and CO2 in water were determined using a water-gas separator, and the results are shown in Table 1 below:

[0047] Experimental group 1 was a shallow lake (6.7 m deep, CH4 flux 0.41 mg / m³). -2 h -1 CO2 flux 1.28 mg m -2 h -1 Experimental group 2 was located upstream of the reservoir (water depth 9.4 m, CH4 flux 0.51 mg / m³). -2 h -1 CO2 flux 1.59 mg m -2 h -1 .

[0048] Table 1 shows that the device and method can accurately and clearly determine the response relationship between greenhouse gas concentration at the water interface of in-situ sediments and time.

[0049] This invention addresses the aforementioned shortcomings through structural innovation, process optimization, and controllable parameters, and its advantages are supported by clear monitoring data, as detailed below: Advantage 1: Accurately verifies interface coverage, ensuring the authenticity of the monitoring area. Innovation: A sediment depth measuring device 203 is installed inside the stainless steel column 2, which can directly measure the sediment depth and verify whether the column completely covers the sediment-water interface; Addressing the shortcomings: Overcoming the problem of existing patents' inability to verify coverage effectiveness, ensuring that the monitoring area is a "real in-situ sediment-water interface"; Application value: For example, if the sediment depth in the monitoring area is 12cm, the insertion depth of the columnar body can be confirmed by measuring instrument to be ≥12cm, avoiding monitoring deviations caused by insufficient coverage.

[0050] Advantage 2: Regular columnar bars + well-defined parameters support accurate flux calculation Innovation: A regularly shaped stainless steel column is used, whose dimensional parameters such as inner diameter and height are known (e.g., in the embodiment, the inner diameter can be set to 10cm, and the cross-sectional area = πr). 2 ≈78.5 cm 2 (The volume can be calculated accurately), providing key parameters for flux calculation; The problem addressed is that the existing patents' "fuzzy parameters lead to inaccurate flux calculations"; Data Support: Combining the monitoring data in Table 1 of the application document, the flux can be accurately calculated. Advantage 3: Establishes a concentration-time dynamic response relationship to reflect the true release pattern. Innovation: By following the steps of "resting → initial monitoring → specific time intervals → secondary monitoring" (S3-S4), the changes in greenhouse gas concentration over time are captured, and a dynamic response relationship is established. Addressing the shortcomings: Overcoming the problem that existing patents "cannot reflect dynamic patterns over time"; Experimental Group 1: Within 28 minutes, the CH4 concentration increased by 55.26% (0.38→0.59), and the CO2 concentration increased by 16.90% (1.42→1.66), clearly demonstrating the dynamic characteristics of "continuous gas release" from the sediments; Experimental Group 2: The CH4 concentration increased by 88.24% (0.34→0.64) within 32 minutes, reflecting the difference in release rate in different monitoring areas. This type of dynamic data cannot be obtained by existing patents and can provide key "time dimension" support for the assessment of carbon cycle in aquatic ecosystems.

[0051] Advantage 4: Strong adaptability to on-site conditions and easy to operate Innovation: The combination of "floating platform + winch + lead counterweight" enables the columnar body to descend vertically and slowly (S2), avoiding water flow disturbance of sediment; no complicated assembly is required, and the lowering is controlled only by the winch, resulting in high operational efficiency; The problem addressed is to circumvent the issues of CN113358426B, namely, "complex assembly and susceptibility to disturbance." Application value: It can be stably applied in real-world scenarios such as natural lakes and rivers, ensuring that the monitoring process does not damage the original environment and further improving the authenticity of the data.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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; and these 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. An apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments, characterized in that: The system includes a regular column (2), a counterweight (3), a pumping pipe (4), a rope (5), an in-situ water body (6), a floating platform (7), a winch (8), and a pump (9). The regular column (2) is placed on the in-situ sediment (1) under the in-situ water body (6). The counterweight (3) is installed on the regular column (2). The floating platform (7) floats on the in-situ water body (6). The winch (8) and the pump (9) are installed on the floating platform (7). The winch (8) is connected to the regular column (2) through the rope (5). The pump (9) is connected to the regular column (2) through the pumping pipe.

2. The apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments as described in claim 1, characterized in that: The regular columnar body (2) is provided with an inlet (201) and an outlet (202).

3. The apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments as described in claim 1, characterized in that: The water inlet (201) is set at an upward angle.

4. The apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments as described in claim 1, characterized in that: The outlet (202) is connected to the pumping pipe (4).

5. The apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments as described in claim 1, characterized in that: The regular columnar body (2) is made of stainless steel.

6. The apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments as described in claim 1, characterized in that: The inner diameter of the column is 50cm, and the water inlet is tilted at 30-45° to ensure that the device is completely submerged in water.

7. The apparatus for measuring greenhouse gas emissions at the water interface of in-situ sediments as described in claim 1, characterized in that: The counterweight (3) is made of lead.

8. A method for measuring greenhouse gas emissions from an in-situ sediment-water interface as described in any one of claims 1-7, characterized in that: The method and steps are as follows: S1. On the water platform (7), the assembled regular columnar body (2) with rope (5) and counterweight (3) and the water pipe (4) are first placed in the water so that there is no air inside the regular columnar body (2) and it is in a vertical state. S2. Turn on the power of the winch (9) and let the regularly shaped stainless steel column (2) with the counterweight (3) descend vertically and slowly, and simultaneously lower the water pipe (4) until the rope (5) is no longer vertical and then turn off the winch (8). S3. After standing for a period of time, turn on the power of the water pump (9). After the water without bubbles comes up, use the water vapor separation device (10) to separate the water vapor. Then use the greenhouse gas analyzer (11) to measure the concentration of greenhouse gases in the water. After the measurement is completed, turn off the water pump (9). S4. After a specific period of time, turn on the power to the water pump (9) again, and then repeat the greenhouse gas monitoring operation in S3. S5. Based on the concentration at the water interface of the in-situ sediments before and after two separate in-situ sediment tests, the time interval, and the inner diameter of the regularly shaped columnar sediment, the greenhouse gas generation rate at the water interface of the in-situ sediments can be calculated.

9. The method for determining greenhouse gas emissions at the water interface of in-situ sediments as described in claim 8, characterized in that: The regular columnar body (2) is equipped with a sediment depth measuring device (203), and the water-gas separation device (10), greenhouse gas analyzer (11), and sediment depth measuring device (203) are all connected to the measurement and control module (12).

10. The method for determining greenhouse gas emissions at the water interface of in-situ sediments as described in claim 9, characterized in that: The sediment depth measuring device (203) is an ultrasonic sensor, ensuring that the detected sediment depth is >5cm.

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