A device, method for monitoring soil gas composition

Abstract

The application discloses a device and method for monitoring soil gas composition, which comprises a porous pipeline, a first valve, a second valve and a fluid source storage container; the porous pipeline is used for laying in the soil of a monitoring area, and the pipe wall of the porous pipeline is provided with a plurality of air permeable holes; the first valve is connected between the outlet of the fluid source storage container and the inlet of the porous pipeline; the second valve is arranged at the outlet of the porous pipeline; and the fluid source storage container is used for storing a liquid fluid which can react with soil gas. According to the scheme, the monitoring pipe network can be laid in the soil of the monitoring area by using the porous pipeline, and a large number of monitoring instruments are not needed, and a monitoring well is not needed to be constructed in the monitoring area, so that the monitoring cost is low; and the monitoring area is wide, the pipeline construction cost is low, the porous pipeline can be laid on a large scale and in a large area, the soil gas in a large monitoring area can be monitored by using the porous pipeline without a large cost under the condition of guaranteeing the monitoring demand, and long-term monitoring can be realized.

Description

Technical Field

[0001] This invention relates to the field of soil gas monitoring technology, and in particular to an apparatus and method for monitoring soil gas composition. Background Technology

[0002] Soil gas refers to the gas contained in the pores of soil and rock below the surface and above the capillary layer that is not filled with water. Soil gas can be used to study various geological problems and environmental surveys, such as exploration of oil, uranium, and geothermal reservoirs, exploration of active faults, earthquakes, and volcanoes, and monitoring of pollutants and underground gas leaks (such as CO2). The composition of soil gas varies significantly under different soil atmospheres, and its main components include gases such as CO2, H2, CH4, and Rn. Traditional methods for monitoring soil gas composition involve directly using instruments to monitor soil gas in the monitoring area or collecting soil gas on-site for laboratory analysis. Among these methods, direct monitoring using instruments in the monitoring area is the most convenient, but the high cost of the instruments makes large-scale application difficult. Soil gas sampling is divided into passive sampling, which involves placing adsorbents below the surface to collect soil gas, and active sampling, which involves constructing soil gas monitoring wells. For various reasons, active sampling has a wider range of applications than passive sampling. Common active sampling monitoring wells include borehole-inserted monitoring wells, drill rod-inserted monitoring wells, and soil gas wells converted from groundwater wells. Borehole-inserted monitoring wells offer high reliability and sampling precision, and can collect soil gas samples from greater depths. They are the most widely used, but their construction process is complex and time-consuming, resulting in high costs and limiting their large-scale application. Drill rod-inserted wells have shorter construction times and lower costs, but their shallower sampling depth (generally no more than 4 meters) limits monitoring effectiveness and makes long-term monitoring impossible. Furthermore, soil atmosphere modification requires excavating the soil from its original environment, modifying it using various physical and chemical techniques, and then reintroducing it into the original environment. This process is complex and costly.

[0003] In summary, traditional methods for monitoring soil gas composition and for modifying soil atmosphere have the following drawbacks:

[0004] 1. Traditional methods for monitoring soil gas composition are complex, requiring the construction of monitoring wells for soil gas sampling and testing, which has drawbacks such as high monitoring costs and difficulty in large-scale, long-term application of monitoring.

[0005] 2. Traditional soil atmosphere modification methods are complex, requiring the excavation and modification of the original soil followed by backfilling, which has drawbacks such as high modification costs and difficulty in large-scale soil atmosphere modification. Summary of the Invention

[0006] In view of this, the present invention provides a device for monitoring soil gas composition, which has the following beneficial effects:

[0007] 1. The device has a simple structure. It only requires the use of porous pipes to lay a monitoring network in the soil of the monitoring area. There is no need to use a large number of additional monitoring instruments or to build monitoring wells in the monitoring area. The total cost is easy to control and a low-cost monitoring system can be quickly formed.

[0008] 2. Wide monitoring area: Due to the low construction cost of pipelines, they can be laid on a large scale and over a large area. While ensuring monitoring needs, it is not necessary to invest too much cost to use porous pipelines for soil gas monitoring in a large monitoring area.

[0009] 3. It can be monitored for a long time. The porous pipeline itself has good pressure resistance and corrosion resistance, and can be buried in the soil for a long time. At the same time, the monitoring system has few electrical devices, is simple to maintain, and can work underground for a long time to effectively monitor the soil gas composition in the monitoring area.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] An apparatus for monitoring soil gas composition includes: a porous pipeline, a first valve, a second valve, and a fluid source storage container;

[0012] The porous pipeline is used to lay in the soil within the monitoring area, and its pipe wall has multiple vent holes. The first valve is connected between the outlet of the fluid source storage container and the inlet of the porous pipeline. The second valve is located at the outlet of the porous pipeline. The fluid source storage container can be used to store liquid fluids that chemically react with soil gas in the soil.

[0013] Preferably, the pipe body of the porous pipeline is made of a porous material with air-loving and liquid-repellent properties.

[0014] Preferably, the material of the porous pipe body includes plastic, ceramic or quartz sand.

[0015] Preferably, the fluid source storage container can be used to store gaseous fluid or a mixture of gaseous fluid and liquid fluid.

[0016] Preferably, it further includes:

[0017] A water quality sensor is installed inside the porous pipe.

[0018] Preferably, the plurality of vent holes are divided into multiple groups and are evenly distributed along the circumference of the porous pipe body. Each group contains multiple vent holes, which are equidistantly distributed along the axial direction of the pipe body.

[0019] Preferably, the porous pipeline includes a grid-shaped porous pipeline;

[0020] The first valve is connected between the outlet of the fluid source storage container and the inlet of the grid-shaped porous pipe; the second valve is located at the outlet of the grid-shaped porous pipe.

[0021] Preferably, the inlet and outlet of the porous pipe are distributed at the same height, and both are lower than the middle part of the porous pipe;

[0022] The device for monitoring soil gas composition also includes:

[0023] A pressure pump connected between the outlet of the fluid source storage container and the inlet of the porous pipeline.

[0024] A method for monitoring soil gas composition, using the apparatus for monitoring soil gas composition as described above, includes the following steps:

[0025] S1. Close the second valve and open the first valve to allow the liquid fluid in the fluid source storage container to flow into the porous pipeline, and close the first valve after the liquid fluid fills the porous pipeline;

[0026] S2. After the liquid fluid reacts with the soil gas in the porous pipeline for a preset time, open the second valve, collect a fluid sample from the outlet of the porous pipeline, and test it.

[0027] Preferably, before step S1, the method further includes:

[0028] S0. Determine the storage type of liquid fluid in the fluid source storage container based on the soil gas composition in the monitoring area.

[0029] As can be seen from the above technical solution, the device for monitoring soil gas composition provided by the present invention has the following beneficial effects:

[0030] 1. The device has a simple structure. It only requires the use of porous pipes to lay a monitoring network in the soil of the monitoring area. There is no need to use a large number of additional monitoring instruments or to build monitoring wells in the monitoring area. The total cost is easy to control and a low-cost monitoring system can be quickly formed.

[0031] 2. Wide monitoring area: Due to the low construction cost of pipelines, they can be laid on a large scale and over a large area. While ensuring monitoring needs, it is not necessary to invest too much cost to use porous pipelines for soil gas monitoring in a large monitoring area.

[0032] 3. It can be monitored for a long time. The porous pipeline itself has good pressure resistance and corrosion resistance, and can be buried in the soil for a long time. At the same time, the monitoring system has few electrical devices, is simple to maintain, and can work underground for a long time to effectively monitor the soil gas composition in the monitoring area.

[0033] The present invention also provides a method for monitoring soil gas composition. Since the above-mentioned device for monitoring soil gas composition is used, it has corresponding beneficial effects, which can be referred to the foregoing description and will not be repeated here. Attached Figure Description

[0034] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the structure of a device for monitoring soil gas composition provided in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram illustrating the fluid movement during internal monitoring of a porous pipeline, as provided in an embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram illustrating the fluid movement during soil atmosphere modification within a porous pipeline, as provided in an embodiment of the present invention.

[0038] Among them, 10 is soil, 11 is soil gas, 20 is porous pipe, 21 is sampling port, 22 is liquid fluid, 23 is pipe wall, 24 is gas fluid, 30 is first valve, 40 is fluid source storage container, and 50 is second valve. Detailed Implementation

[0039] This invention discloses a simple and effective method for monitoring soil gas composition and modifying soil atmosphere. It can effectively monitor soil gas composition for a long period of time, and modify soil atmosphere based on the monitored soil gas data. It is low in cost and can be carried out on a large scale for a long period of time.

[0040] 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.

[0041] The device for monitoring soil gas composition provided in this embodiment of the invention, such as... Figure 1 As shown, it includes: a porous pipe 20, a first valve 30, a second valve 50, and a fluid source storage container 40;

[0042] The porous pipe 20 is used to lay in the soil 10 in the monitoring area, and its pipe wall 23 has multiple vent holes; the first valve 30 is connected between the outlet of the fluid source storage container 40 and the inlet of the porous pipe 20; the second valve 50 is set at the outlet of the porous pipe 20; the fluid source storage container 40 can be used to store the liquid fluid 22 that reacts chemically with the soil gas 11 of the soil 10.

[0043] It should be noted that this scheme uses porous pipes 20 to lay a monitoring network in the soil 10 within the monitoring area. The inlet end of the monitoring network is connected to the outlet of the fluid source storage container 40 through a first valve 30, and the outlet end of the monitoring network is equipped with a second valve 50, which serves as the sampling port 21. Figure 2 As shown, soil gas 11 in soil 10 can pass through the vents of porous pipe 20 and enter the pipe to react chemically with liquid fluid 22. A liquid sample is then collected from the outlet of the monitoring network, and the composition of the liquid sample is detected. The composition of soil gas 11 is then determined based on the changes in the liquid sample composition; that is, the composition of soil gas 11 is monitored based on the changes in the composition of the liquid fluid within the porous pipe 20. Specifically, the effective components in soil gas 11 (such as CO2) react chemically with the liquid fluid, causing changes in the composition of the liquid fluid. These changes are then monitored to determine the composition of the soil gas 11 (e.g., pH, Fe). 2+ / Fe 3+ Ca 2+ This allows us to understand the effective components of the soil gas 11 that reacts with the liquid fluid. In other words, the liquid fluid within the porous pipe 20 can circulate and fully react with the soil gas 11 in the monitoring area. Regularly collected fluid samples from the porous pipe 20 are monitored to track changes in its composition, thus revealing the composition of the soil gas 11. Of course, the liquid fluid 22 within the porous pipe 20 is unlikely to diffuse through the pores into the soil 10. Furthermore, the breakthrough pressure of the liquid fluid within the porous pipe 20 satisfies p... c =2σ / r;

[0044] Where p c The breakthrough pressure of the liquid fluid in the porous pipe 20 is such that if the pressure exceeds this, the liquid fluid will pass through the vent holes of the porous pipe 20 and enter the soil 10.

[0045] σ is the surface tension between the liquid surfaces, and r is the radius of the porous pipe.

[0046] As can be seen from the above technical solutions, the device for monitoring soil gas composition provided in the embodiments of the present invention has the following beneficial effects:

[0047] 1. The device has a simple structure. It only requires the use of porous pipes to lay a monitoring network in the soil of the monitoring area. There is no need to use a large number of additional monitoring instruments or to build monitoring wells in the monitoring area. The total cost is easy to control and a low-cost monitoring system can be quickly formed.

[0048] 2. Wide monitoring area: Due to the low construction cost of pipelines, they can be laid on a large scale and over a large area. While ensuring monitoring needs, it is not necessary to invest too much cost to use porous pipelines for soil gas monitoring in a large monitoring area.

[0049] 3. It can be monitored for a long time. The porous pipeline itself has good pressure resistance and corrosion resistance, and can be buried in the soil for a long time. At the same time, the monitoring system has few electrical devices, is simple to maintain, and can work underground for a long time to effectively monitor the soil gas composition in the monitoring area.

[0050] In other words, the device for monitoring soil gas composition provided by this invention can be applied to various geological engineering fields that require soil gas composition as a reference, such as geothermal reservoir exploration, seismic exploration, and geological storage assessment.

[0051] In this design, the porous pipe 20 is made of a porous material with air- and liquid-repellent properties, allowing soil gas 11 or gaseous fluid to pass through the pores of the porous pipe 20, while preventing liquid fluid 22 from diffusing into the soil 10. In other words, this design uses an air- and liquid-repellent porous material to create the porous pipe 20 and bury it in the soil 10. This allows the liquid fluid injected into the porous pipe 20 to react with the soil gas 11 penetrating the pipe. By monitoring changes in the liquid fluid composition, the composition of the soil gas 11 can be monitored. Furthermore, the porous pipe 20 is manufactured using a single-piece molding process using an air- and liquid-repellent porous material. Naturally, the pores of the porous pipe 20 are also small pores manufactured using a single-piece molding process.

[0052] Specifically, in order to better enable the porous tube 20 to exhibit liquid repellency when in contact with liquid, the material of the porous tube 20 body preferably includes plastic, ceramic or quartz sand.

[0053] Furthermore, it should be noted that different materials used in the porous pipe 20 result in different surface wettability; surface wettability refers to the ability of a droplet to spread on a solid material surface. When a droplet lands on a solid material surface, after the gas, liquid, and solid phases reach equilibrium, the angle formed between the tangent of the droplet at the gas-liquid-solid three-phase intersection and the gas-solid interface boundary line is the three-phase contact angle. When the contact angle of a water droplet on a solid surface is greater than 150° and the roll-off angle is less than 10°, the solid surface is considered a superhydrophobic surface. This scheme uses porous material pipes 20 made of materials such as plastic, ceramic, and quartz sand. These pipes exhibit lipolytic properties when in contact with liquids. This ensures that when the porous pipes 20 are buried in the soil 10, the liquid fluid cannot penetrate the pipe walls due to the lipolytic properties, while the gaseous fluid remains unaffected. Only the gaseous fluid can diffuse between the inside and outside of the porous pipes 20. In this way, the soil gas 11 in the monitoring area can react with the liquid fluid inside the pipes after passing through the porous pipes 20. The liquid fluid inside the porous pipes 20 will circulate along the pipe network within the monitoring area. Since only the gaseous fluid can pass through the porous pipes 20, monitoring the changes in the liquid fluid inside the porous pipes 20 can effectively reveal the composition of the soil gas 11 in the monitoring area.

[0054] Furthermore, the fluid source storage container 40 can be used to store gaseous fluid 24 or a mixture of gaseous fluid 24 and liquid fluid 22. This design allows for the injection of specific gaseous fluid 24 or a mixture of gaseous fluid 24 and liquid fluid 22 into the porous pipe 20 according to soil atmosphere modification needs. This allows the gaseous fluid 24 to diffuse through the vents into the soil 10, thereby improving the soil atmosphere. This soil atmosphere modification method is simple, effective, low-cost, and suitable for large-scale soil atmosphere modification.

[0055] Furthermore, based on the soil atmosphere modification goals, this scheme stores gaseous fluid 24 or a mixed fluid containing gaseous fluid 24 within the fluid source storage container 40, wherein, for example... Figure 3 As shown, gaseous fluid 24 is used as the modification gas. Gaseous fluid 24, or a mixture containing gaseous fluid 24, is injected into the porous pipe 20, allowing the modification gas to diffuse through the vents into the soil 10 in the monitoring area, thereby altering the atmosphere and affinity of the soil 10. Furthermore, it should be noted that this scheme can determine the type of modification gas based on the original soil atmosphere and the soil atmosphere to be modified. After passing through the pipe wall of the porous pipe 20, the modification gas reacts with the soil 10. After sufficient reaction (generally 7-14 days), the original atmosphere of the soil can be altered, including the affinity, pH, and other atmosphere of the soil 10.

[0056] Furthermore, the device for monitoring soil gas composition provided in this embodiment of the invention further includes:

[0057] A water quality sensor is installed inside the porous pipe 20.

[0058] It should be noted that this solution has multiple water quality sensors installed in the porous pipe 20 to monitor changes in pH, ORP and ion content of substances inside the liquid fluid in real time, thereby determining the composition of soil gas 11, which can help to achieve online rapid monitoring of the composition of soil gas 11.

[0059] Specifically, the multiple vents are divided into multiple groups and are evenly distributed along the circumference of the porous pipe 20. Each group contains multiple vents, which are equidistantly distributed along the axial direction of the pipe. This design facilitates a uniform and sufficient reaction between the soil gas 11 and the liquid fluid within the porous pipe 20, thereby helping to better ensure the accuracy of soil gas 11 composition monitoring.

[0060] Furthermore, such as Figure 1 As shown, the porous pipe 20 includes a grid-shaped porous pipe;

[0061] The first valve 30 is connected between the outlet of the fluid source storage container 40 and the inlet of the grid-shaped porous pipeline; the second valve 50 is located at the outlet of the grid-shaped porous pipeline. In other words, this scheme designs the porous pipeline 20 as a grid-shaped monitoring network to increase the monitoring range of soil gas 11 components. Of course, the porous pipeline 20 can also adopt other pipeline shapes, such as spiral porous pipelines, etc., which will not be elaborated here.

[0062] Furthermore, such as Figure 1 As shown, the inlet and outlet of the porous pipe 20 are distributed at the same height and are both lower than the middle part of the porous pipe 20, so that the liquid fluid enters and exits the porous pipe 20 at a low level.

[0063] The device for monitoring soil gas composition also includes:

[0064] A pressure pump is connected between the outlet of the fluid source storage container 40 and the inlet of the porous pipe 20. This pressure pump provides the power to transport liquid or gaseous fluids. In other words, the inlet and outlet of the porous pipe 20 in this design are low-lying, and the pressure pump provides the fluid transport power, thus better ensuring that the liquid or gaseous fluid fills the middle section of the porous pipe 20.

[0065] This invention also provides a method for monitoring soil gas composition, using the apparatus for monitoring soil gas composition as described above, and comprising the following steps:

[0066] S1. Close the second valve and open the first valve to allow the liquid fluid in the fluid source storage container to flow into the porous pipeline, and close the first valve after the liquid fluid fills the porous pipeline;

[0067] S2. After the liquid fluid reacts with the soil gas in the porous pipeline for a preset time, the second valve is opened to collect a fluid sample from the outlet of the porous pipeline and perform analysis. Since this scheme uses the aforementioned device for monitoring soil gas composition, it has corresponding beneficial effects, as detailed above, which will not be repeated here.

[0068] In this scheme, in order to better monitor the composition of soil gas 11, the following steps are included before step S1:

[0069] S0. Determine the storage type of liquid fluid in the fluid source storage container based on the soil gas composition in the monitoring area.

[0070] It should be noted that the composition of soil gas in the monitoring area can be determined by testing instruments, on-site measurement, or laboratory measurement by collecting soil gas samples.

[0071] The following is a further description of this solution with reference to specific embodiments:

[0072] This invention was used at a CO2 geological storage site to monitor the CO2 content in the soil gas of the storage area in order to assess the safety status of the storage area.

[0073] The porous pipe 20 is made of breathable, hydrophobic porous ceramic material. In cross-section, the porous pipe 20 consists of liquid fluid 22, pipe wall 23 and gas fluid 24 from the inside to the outside.

[0074] The first valve 30 and the second valve 50 are used, wherein the second valve 50 is a sampling valve. The first valve 30 and the second valve 50 are standard ball valves to control the injection of liquid fluid in the porous pipeline 20. Fluid samples in the porous pipeline 20 are collected by opening and closing the first valve 30 and the second valve 50.

[0075] In this example, the liquid fluid in the fluid source storage container 40 is pure water, which is readily available and can react with CO2.

[0076] The working steps of this device are as follows:

[0077] 1. A monitoring network is laid in the soil 10 of the sealed area using a porous pipe 20. In this example, the porous pipe 20 is buried at a depth of about 1m. The porous pipe 20 is connected to the fluid source storage container 40 through the first valve 30, and the water in the fluid source storage container 40 can be controlled to be injected into the porous pipe 20 through the first valve 30. The end of the porous pipe 20 is connected to the second valve 50.

[0078] 2. Open the first valve 30 and close the second valve 50. Water in the fluid source storage container 40 will be injected into the porous pipe 20. After the porous pipe 20 is full of water, close the first valve 30. After the water in the porous pipe 20 reacts with CO2 in the soil for 14 days, open the second valve 50 to collect water samples from the porous pipe 20 and test their composition to understand the changes in CO2 content in the soil atmosphere.

[0079] 3. For soil atmosphere that needs to be modified, the neutral soil atmosphere can be modified to be slightly acidic. The fluid in the fluid source storage container 40 can be replaced with gaseous CO2 fluid. By opening the first valve 30 and closing the second valve 50, CO2 can be injected into the porous pipe 20 and allowed to slowly diffuse into the soil 10 through the pipe wall of the porous pipe 20, thereby modifying the atmosphere and affinity of the soil 10.

[0080] In summary, this invention discloses a method for monitoring soil gas composition and soil atmosphere modification, specifically involving a subsurface monitoring method. This method includes the following steps: ① A monitoring network is laid in the soil 10 using porous pipes 20. The porous pipes 20 are made of porous materials with special permeability, such as those that are gas-loving and liquid-repellent, allowing soil gas outside the porous pipes 20 to pass through while preventing liquid inside the pipes from diffusing into the soil. The inlet of the monitoring network is connected to a fluid source storage container 40 via a first valve 30; ② Based on the soil atmosphere of the monitoring area, a suitable monitoring fluid is selected as the liquid fluid, and changes in soil gas composition and atmosphere are monitored based on changes in the fluid composition of the porous pipes 20; ③ As needed, a specific gas is injected through the porous pipes 20, and the gas diffuses into the soil through the porous pipes, improving the soil atmosphere.

[0081] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0082] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A device for monitoring soil gas composition, characterized in that, include: Porous pipe (20), first valve (30), second valve (50) and fluid source storage container (40); The porous pipe (20) is used to lay on the soil (10) in the monitoring area and serve as a monitoring network. Its pipe wall (23) has multiple vent holes. The first valve (30) is connected between the outlet of the fluid source storage container (40) and the inlet of the porous pipe (20). The second valve (50) is located at the outlet of the porous pipe (20). The outlet of the porous pipe (20) serves as a sampling port (21). The fluid source storage container (40) can be used to store liquid fluid (22) that reacts chemically with the soil gas (11) of the soil (10). The body of the porous pipe (20) is made of a porous material with air-loving and liquid-repellent properties; The material of the porous pipe (20) includes plastic, ceramic or quartz sand; wherein the material of the porous pipe (20) is a breathable and hydrophobic porous ceramic. The fluid source storage container (40) can be used to store gaseous fluid (24) or a mixture of gaseous fluid (24) and liquid fluid (22); wherein the gaseous fluid (24) is a soil atmosphere modification gas.

2. The device for monitoring soil gas composition according to claim 1, characterized in that, Also includes: A water quality sensor is installed inside the porous pipe (20).

3. The device for monitoring soil gas composition according to claim 1, characterized in that, The multiple air vents are divided into multiple groups and are evenly distributed along the circumference of the porous pipe (20). Each group has multiple air vents and they are equidistantly distributed along the axial direction of the pipe.

4. The device for monitoring soil gas composition according to claim 1, characterized in that, The porous pipeline (20) includes a grid-shaped porous pipeline; The first valve (30) is connected between the outlet of the fluid source storage container (40) and the inlet of the grid-shaped porous pipeline; the second valve (50) is located at the outlet of the grid-shaped porous pipeline.

5. The device for monitoring soil gas composition according to claim 1, characterized in that, The inlet and outlet of the porous pipe (20) are at the same height and are both lower than the middle part of the porous pipe (20); The device for monitoring soil gas composition also includes: A pressure pump connected between the outlet of the fluid source storage container (40) and the inlet of the porous pipeline (20).

6. A method for monitoring soil gas composition, characterized in that, Monitoring using the apparatus for monitoring soil gas composition as described in any one of claims 1-5 includes the following steps: S1. Close the second valve and open the first valve to allow the liquid fluid in the fluid source storage container to flow into the porous pipeline, and close the first valve after the liquid fluid fills the porous pipeline; S2. After the liquid fluid reacts with the soil gas in the porous pipeline for a preset time, open the second valve, collect a fluid sample from the outlet of the porous pipeline, and test it.

7. The method for monitoring soil gas composition according to claim 6, characterized in that, Before step S1, the following is also included: S0. Determine the storage type of liquid fluid in the fluid source storage container based on the soil gas composition in the monitoring area.

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