Testing device for simulating pollutant migration process under temperature-moisture coupling effect

Abstract

The invention provides a test device for simulating a pollutant migration process under a temperature-moisture coupling effect, and belongs to the field of soil environment scientific research. The test device comprises variable-pressure gas supply equipment, a soil column pipe, exhaust equipment, a rainfall simulation system, evaporation and illumination simulation equipment and a data acquisition and analysis system. The variable-pressure gas supply equipment comprises a pollution gas storage tank and a pressure controller; the soil column pipe comprises an air inlet cavity, a simulated soil column cavity and an exhaust cavity, and a sampling hole is reserved in the simulated soil column cavity; the data acquisition and analysis equipment comprises a distributed optical fiber, a data acquisition instrument, a computer and a gas chromatograph. The test device and the test method provided by the invention can accurately control temperature and humidity, simulate rainfall, evaporation and illumination, are suitable for various soil types, record data in real time through a high-precision monitoring system, and reveal diffusion, convection and adsorption rules of gas in the soil.

Description

Technical Field

[0001] The invention relates to the field of soil environmental science research, and in particular to a test device for simulating a pollutant migration process under the coupling effect of temperature and moisture. Background Art

[0002] In the fields of landfills, water resources management, and environmental science, it is crucial to understand the migration mechanism of polluted gases in soil. However, due to the complexity and heterogeneity of soil structure, the migration process of polluted gases in soil is difficult to directly observe and analyze. At present, the gas migration mechanism is mainly explored through theoretical models and numerical simulations, but these methods are often based on simplified assumptions and lack experimental verification. Therefore, the development of an experimental device and experimental method that can simulate the pollutant migration process under the coupling of temperature and moisture is of great significance for a deep understanding of the migration mechanism of polluted gases, assessing soil environmental risks, and formulating corresponding management measures.

[0003] Currently, in the prior art:

[0004] Chinese patent CN118425474A provides a "temperature control test device for simulating the impact of groundwater level changes and rainfall on soil pollution". The temperature control test device includes a test soil column, a rainfall simulation component, a groundwater level simulation component, a temperature control component and a pollutant addition cylinder; the rainfall simulation component simulates rainfall conditions of different intensities and durations, the groundwater level simulation component simulates the rise and fall of the groundwater level, controls the fluctuation amplitude of the groundwater level, and the temperature control component simulates the ambient temperature, providing a controllable, safe and efficient platform that can help researchers to have a deeper understanding of the impact mechanism of groundwater level changes and rainfall on soil pollution, explore the impact of the fluctuation amplitude and period of the groundwater level, soil characteristics and groundwater level depth on the phase distribution, adsorption-desorption, migration and diffusion of organic composite pollutants, and provide a scientific basis for the prevention and control of soil pollution.

[0005] Chinese patent CN104777271A provides "A multifunctional dry and wet deposition trickling filtration test system", which includes a gas mixing system, a liquid circulation system and a trickling filtration experimental system. The invention can use polluted gases of different concentrations to perform flux exchange diffusion and leaching trickling filtration on the soil at different humidity, simulate dry and wet deposition migration scenarios, and compare with the deposition flux and distribution concentration of pollutants. Through the migration numerical model, the migration and accumulation process of pollutants in the atmosphere-soil is quantitatively described, revealing the influence of factors such as pollutant characteristics on the migration process of pollutants.

[0006] Comprehensive analysis of the test equipment of the above units shows that there are still the following deficiencies:

[0007] 1) The ambient temperature is not accurately simulated and controlled. In soil, temperature has an important influence on the migration of gas in the soil. It will change the thermal motion rate of gas molecules and thus affect the diffusion rate of gas.

[0008] 2) The simulation of humidity cannot reflect the dynamic changes of ambient humidity, but the overall simulation of humidity is not comprehensive and accurate enough.

[0009] 3) Single soil type: The diversity of soil types has not been fully considered, and there is a lack of research on types such as sandy soil, loam and clay.

[0010] 4) Fixed soil properties: issues such as soil compaction, natural fluctuations in water content, and the evolution of soil microbial communities Summary of the invention

[0011] The technical problem to be solved by the present invention is that the existing technology has insufficient research on the migration mechanism of polluted gases in soil, and provides a test device and test method that can comprehensively, accurately and realistically simulate the migration process of polluted gases in soil. The device can reveal the migration laws of polluted gases in soil, such as diffusion, convection and adsorption, and provide strong support for research and application in related fields.

[0012] In order to achieve the above-mentioned object, the present invention provides a test device for simulating the pollutant migration process under the temperature-moisture coupling effect, the test device comprises a variable pressure gas supply device, a soil column pipe, an exhaust device, a simulated rainfall system, simulated evaporation and illumination equipment, and a data acquisition and analysis system:

[0013] The variable pressure gas supply equipment includes a polluted gas storage tank, a lower valve and a pressure controller connected in sequence; the exhaust equipment includes a waste gas collection tank, an upper valve and a pressure gauge connected in sequence;

[0014] The soil column tube is a hollow circular tube with closed ends and placed vertically, and is composed of three cavities, which are, from bottom to top, an air inlet cavity, a simulated soil column cavity and an exhaust cavity; an air inlet port is opened at the bottom of the air inlet cavity, and the pressure controller is connected to the air inlet port through a section of air inlet pipe, and the top of the air inlet cavity is separated from the simulated soil column cavity by a horizontally placed porous plate; the simulated soil column cavity is filled with soil compacted to a specified dry density in layers to form a test soil column; an exhaust port is opened at the top of the exhaust cavity, and the pressure gauge is connected to the exhaust port through a section of exhaust pipe; a plurality of sampling holes are evenly arranged along a vertical line on the tube wall corresponding to the simulated soil column cavity, and each sampling hole is provided with a plug;

[0015] The simulated rainfall system includes a rainmaker, a peristaltic pump and a water storage tank. The rainmaker is a cylinder containing a cavity, the cross-sectional diameter of which is adapted to the diameter of the exhaust cavity, and is installed on the upper part of the exhaust cavity. A water inlet is opened on the top of the rainmaker, and a plurality of water outlets are evenly opened on the bottom to achieve uniform simulated rainfall on the test soil column. One end of the peristaltic pump is connected to the water storage tank, and the other end is connected to the water inlet on the top of the rainmaker through a section of water inlet pipe.

[0016] The simulated evaporation and illumination equipment includes a fan and a heat source, both of which are installed on the inner wall of the top of the soil column tube and located above the rainmaker;

[0017] The data acquisition and analysis equipment comprises a distributed optical fiber, a data acquisition instrument, a gas chromatograph and a computer; the distributed optical fiber is arranged in a simulated soil column cavity and penetrates the test soil column.

[0018] Preferably, the ratio of the air inlet cavity, the simulated soil column cavity and the exhaust cavity is 1:5-8:1.

[0019] Preferably, a flow meter is installed between the air inlet and the pressure controller, and between the air outlet and the pressure gauge respectively.

[0020] Preferably, sealing rings are installed at the contact point between the air inlet pipe and the air inlet port, and at the contact point between the exhaust pipe and the exhaust port, so as to ensure the sealing during the test.

[0021] Preferably, the gas chromatograph is connected to a computer, and is used to analyze the contaminated soil samples obtained through the sampling holes, and send the analysis results to the computer; the distributed optical fiber is buried in the center of the test soil column, and is used to measure the temperature and moisture at different depths of the test soil column. One end of the data acquisition instrument is connected to the distributed optical fiber, and the other end is connected to the computer, and the acquisition results are sent to the computer.

[0022] Preferably, the distributed optical fiber test temperature has an accuracy of 0.1°C, the moisture content has an accuracy of 0.1%, and the data output point interval is 1 cm.

[0023] Preferably, the experiment simulating the pollutant migration process under the temperature-moisture coupling effect comprises the following steps:

[0024] Step 1: close the upper valve and the lower valve, and seal the multiple sampling holes with plugs; then compact the soil layer by layer to a certain dry density and place it in the simulated soil column cavity; set the power of the peristaltic pump and supply water to make the rainmaker rain steadily; turn on the fan and heat source;

[0025] Step 2: Open the lower valve to allow the polluted gas to enter the bottom of the soil. After 1 minute, close the lower valve to ensure the airtightness of the device. At the same time, open the plug of the sampling hole every 1 minute to take samples and use a gas chromatograph to detect the concentration of polluted gas at different depths. Use Comsol numerical simulation software to fit the diffusion coefficient of the polluted gas.

[0026] Step 3: Open the upper valve and the lower valve to allow the polluted gas to enter the bottom of the soil, change the intake pressure through the pressure controller, and record the intake pressure, intake flow, exhaust flow, and exhaust pressure after the exhaust flow is stable; gradually increase the intake pressure, record the intake pressure, intake flow, exhaust flow, and exhaust pressure, and use Darcy's law to calculate the permeability coefficient of the polluted gas in the soil;

[0027] Repeat steps 2-3 by changing the temperature and rainfall conditions, that is, simulating the transmission process of polluted gases under different temperature-moisture coupling conditions, and obtaining data on multiple groups of diffusion coefficients of polluted gases and multiple groups of permeability coefficients of polluted gases in soil;

[0028] Step 4: Use distributed optical fiber to record the temperature and moisture of soil at different depths, transmit the collected data to a data acquisition instrument, and then transmit it to a computer through the data acquisition instrument.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention provides a comprehensive and accurate test device for simulating the transport mechanism of gas in soil. The corresponding simulation test using the test device can reveal the migration laws of polluted gas in soil, such as diffusion, convection and adsorption.

[0031] 2. The present invention can reflect the comprehensive effects of various complex factors under natural conditions by controlling light, rainfall, wind speed, etc., making the research results more realistic.

[0032] 3. By changing the soil type, the present invention can simulate the gas migration process under different soil textures, pore structures, particle size distributions, and water content conditions to meet various research needs.

[0033] 4. The distributed optical fiber of the monitoring system can quickly and accurately monitor soil temperature and moisture; the data analyzer records key data such as polluted gas flow and pressure difference in real time, providing researchers with detailed data support.

[0034] 5. The present invention has a compact structure, is easy to operate, and is easy to maintain and upgrade, and is suitable for various laboratories and scientific research sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1It is a schematic diagram of the structure of the test device for simulating the pollutant migration process under the temperature-moisture coupling effect of the present invention.

[0036] In the figure: 1. Computer; 2. Data acquisition instrument; 3. Sampling hole; 4. Distributed optical fiber; 5. Rainmaker; 6. Fan; 7. Heat source; 8. Waste gas collection tank; 9. Water storage tank; 10. Peristaltic pump; 11. Simulated soil column cavity; 12. Air inlet cavity; 13. Flow meter; 14. Pressure controller; 15. Polluted gas storage tank; 16. Porous plate; 17. Exhaust cavity; 18. Pressure gauge; 19. Upper valve; 20. Gas chromatograph; 21. Lower valve. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Figure 1 The schematic diagram of the structure of the test device for simulating the migration process of pollutants under the coupling effect of temperature and moisture of the present invention is as follows: Figure 1 It can be seen that the present invention provides a test device for simulating the pollutant migration process under the temperature-moisture coupling effect, and the test device includes a variable pressure gas supply device, a soil column pipe, an exhaust device, a simulated rainfall system, simulated evaporation and lighting equipment, and a data acquisition and analysis system.

[0039] The variable pressure gas supply equipment includes a polluted gas storage tank 15, a lower valve 21 and a pressure controller 14 which are connected in sequence; the exhaust equipment includes a waste gas collection tank 8, an upper valve 19 and a pressure gauge 18 which are connected in sequence.

[0040] In this embodiment, the pollutant gas is benzene vapor.

[0041] The soil column tube is a hollow circular tube with closed ends and placed vertically, and is composed of three cavities, which are, from bottom to top, an air inlet chamber 12, a simulated soil column chamber 11 and an exhaust chamber 17; an air inlet port is opened at the bottom of the air inlet chamber 12, and the pressure controller 14 is connected to the air inlet port through a section of air inlet pipe, and the top of the air inlet chamber 12 is separated from the simulated soil column chamber 11 by a horizontally placed porous plate 16, and the simulated soil column chamber 11 is filled with soil that is compacted to a specified dry density in layers to form a test soil column, and an exhaust port is opened at the top of the exhaust chamber 17, and the pressure gauge 18 is connected to the exhaust port through a section of exhaust pipe; a plurality of sampling holes 3 are evenly arranged along a vertical line on the tube wall corresponding to the simulated soil column chamber 11, and each sampling hole 3 is provided with a plug.

[0042] In this embodiment, the ratio of the air inlet cavity 12, the simulated soil column cavity 11 and the exhaust cavity 17 is 1:5-8:1. In addition, in this embodiment, the total length of the soil column tube is 70cm-90cm, and the inner diameter is 12cm-18cm.

[0043] In this embodiment, the porous plate 16 is a circular flat plate with a diameter slightly smaller than the inner diameter of the soil column tube, and is horizontally installed at the top of the air inlet cavity 12 by three buckles attached to the inner wall of the soil column tube. In this embodiment, the buckle is detachable, that is, the buckle position can be adjusted according to the test needs to change the length of the simulated soil column cavity 11 to meet the needs of various tests. The circular flat plate is evenly distributed with a plurality of air holes. When the soil is fine-grained soil, the hole diameter is 1mm-2mm, and when the soil is coarse-grained soil, the hole diameter is 3mm-5mm.

[0044] The simulated rainfall system includes a rainmaker 5, a peristaltic pump 10 and a water reservoir 9. The rainmaker 5 is a cylinder containing a cavity, and its cross-sectional diameter is adapted to the diameter of the exhaust cavity 17, and is installed on the upper part of the exhaust cavity 17. A water inlet is opened at the top of the rainmaker 5, and a plurality of water outlets are evenly opened at the bottom to achieve uniform simulated rainfall on the test soil column. One end of the peristaltic pump 10 is connected to the water reservoir 9, and the other end is connected to the water inlet at the top of the rainmaker 5 through a section of water inlet pipe.

[0045] The simulated evaporation and illumination device comprises a fan 6 and a heat source 7 , both of which are installed on the inner wall of the top of the soil column pipe and located above the rainmaker 5 .

[0046] The data acquisition and analysis equipment includes a distributed optical fiber 4, a data acquisition instrument 2, a gas chromatograph 20 and a computer 1. The distributed optical fiber is arranged in the simulated soil column cavity 11 and penetrates the test soil column.

[0047] In this embodiment, the gas chromatograph 20 is connected to the computer 1, and is used to analyze the contaminated soil samples obtained through the sampling holes 3, and send the analysis results to the computer 1. The distributed optical fiber 4 is buried at the center of the test soil column, and is used to measure the temperature and moisture at different depths of the test soil column. One end of the data acquisition instrument 2 is connected to the distributed optical fiber 4, and the other end is connected to the computer 1, and the acquisition results are sent to the computer 1. The distributed optical fiber 4 has a test temperature accuracy of 0.1°C, a moisture content accuracy of 0.1%, and a data output point interval of 1 cm.

[0048] In this embodiment, a flow meter 13 is installed between the air inlet and the pressure controller 14 and between the air outlet and the pressure gauge 18 respectively.

[0049] In this embodiment, sealing rings are installed at the contact point between the air inlet pipe and the air inlet port, and at the contact point between the exhaust pipe and the exhaust port, so as to ensure the sealing during the test.

[0050] In this embodiment, the above-mentioned test device is used to conduct a test to simulate the migration process of pollutants under the temperature-moisture coupling effect, including the following steps:

[0051] Step 1, close the upper valve 19 and the lower valve 21, and seal the multiple sampling holes 3 with plugs; then compact the soil layer by layer to a certain dry density and place it in the simulated soil column cavity 11; set the power of the peristaltic pump 10 and supply water to make the rainmaker 5 rain steadily; turn on the fan 6 and the heat source 7;

[0052] Step 2, open the lower valve 21 to allow the polluted gas to enter the bottom of the soil, and close the lower valve 21 after 1 minute to ensure the airtightness of the device; at the same time, open the plug of the sampling hole 3 every 1 minute to take samples and use the gas chromatograph 20 to detect the concentration of the polluted gas at different depths; use Comsol numerical simulation software to fit the diffusion coefficient of the polluted gas;

[0053] Step 3, open the upper valve 19 and the lower valve 21 to allow the polluted gas to enter the bottom of the soil, change the intake pressure through the pressure controller 14, and record the intake pressure, intake flow, exhaust flow, and exhaust pressure after the exhaust flow is stable; gradually increase the intake pressure, record the intake pressure, intake flow, exhaust flow, and exhaust pressure, and use Darcy's law to calculate the permeability coefficient of the polluted gas in the soil;

[0054] Repeat steps 2-3 by changing the temperature and rainfall conditions, that is, simulating the transmission process of polluted gases under different temperature-moisture coupling conditions, and obtaining data on multiple groups of diffusion coefficients of polluted gases and multiple groups of permeability coefficients of polluted gases in soil;

[0055] Step 4, using the distributed optical fiber 4 to respectively record the temperature and moisture of the soil at different depths, transmit the collected data to the data acquisition device 2, and then transmit it to the computer 1 through the data acquisition device 2.

[0056] As can be seen from the above, the test device of the present invention can be used to adjust rainfall, wind speed, temperature and moisture to simulate a more realistic environment, reduce the system error of indoor tests, and conduct multiple tests. Based on the observation results, the transmission process of polluted gases under different temperature-moisture coupling conditions can be obtained.

[0057] The experimental device for simulating the pollutant migration process under the temperature-moisture coupling provided by the present invention can realize the study of the migration process of polluted gas in soil under the temperature-moisture coupling and in different soil types.

Claims

1. A test device for simulating the migration process of pollutants under the coupling effect of temperature and moisture, characterized in that: The test device includes a variable pressure gas supply device, a soil column pipe, an exhaust device, a simulated rainfall system, simulated evaporation and lighting equipment, and a data acquisition and analysis system: The variable pressure gas supply equipment comprises a polluted gas storage tank (15), a lower valve (21) and a pressure controller (14) which are connected in sequence; the exhaust equipment comprises an exhaust gas collection tank (8), an upper valve (19) and a pressure gauge (18) which are connected in sequence; The soil column tube is a hollow circular tube with closed ends and placed vertically, and is composed of three cavities, which are, from bottom to top, an air inlet cavity (12), a simulated soil column cavity (11) and an exhaust cavity (17); an air inlet is opened at the bottom of the air inlet cavity (12), and the pressure controller (14) is connected to the air inlet through a section of air inlet pipe, and the top of the air inlet cavity (12) is separated from the simulated soil column cavity (11) by a horizontally placed porous plate (16); the simulated soil column cavity (11) is filled with soil compacted to a specified dry density in layers to form a test soil column; an exhaust port is opened at the top of the exhaust cavity (17), and the pressure gauge (18) is connected to the exhaust port through a section of exhaust pipe; a plurality of sampling holes (3) are evenly arranged along a vertical line on the tube wall corresponding to the simulated soil column cavity (11), and each sampling hole (3) is provided with a plug; The simulated rainfall system comprises a rainmaker (5), a peristaltic pump (10) and a water storage tank (9); the rainmaker (5) is a cylinder containing a cavity, the cross-sectional diameter of which matches the diameter of the exhaust cavity (17), and is installed on the upper part of the exhaust cavity (17); a water inlet is opened at the top of the rainmaker (5), and a plurality of water outlets are evenly opened at the bottom to achieve uniform simulated rainfall on the test soil column; one end of the peristaltic pump (10) is connected to the water storage tank (9), and the other end is connected to the water inlet at the top of the rainmaker (5) through a section of water inlet pipe; The simulated evaporation and illumination device comprises a fan (6) and a heat source (7), both of which are installed on the inner wall of the top of the soil column tube and located above the rainmaker (5); The data acquisition and analysis equipment comprises a distributed optical fiber (4), a data acquisition instrument (2), a gas chromatograph (20) and a computer (1); the distributed optical fiber (4) is arranged in a simulated soil column cavity (11) and penetrates the test soil column.

2. The test device for simulating the pollutant migration process under the temperature-moisture coupling effect according to claim 1 is characterized in that: The ratio of the air intake cavity (12), the simulated soil column cavity (11) and the exhaust cavity (17) is 1:5-8:

1.

3. The test device for simulating the pollutant migration process under the temperature-moisture coupling effect according to claim 1 is characterized in that: A flow meter (13) is installed between the air inlet and the pressure controller (14), and between the air outlet and the pressure gauge (18).

4. The test device for simulating the pollutant migration process under the temperature-moisture coupling effect according to claim 1, characterized in that: Sealing rings are installed at the contact point between the air inlet pipe and the air inlet port, and at the contact point between the exhaust pipe and the exhaust port to ensure the sealing during the test.

5. The test device for simulating the pollutant migration process under the temperature-moisture coupling effect according to claim 1, characterized in that: The gas chromatograph (20) is connected to the computer (1) and is used to analyze the contaminated soil samples obtained through the sampling holes (3) and send the analysis results to the computer (1); the distributed optical fiber (4) is buried at the center of the test soil column and is used to measure the temperature and moisture at different depths of the test soil column; one end of the data acquisition instrument (2) is connected to the distributed optical fiber (4) and the other end is connected to the computer (1) to send the collection results to the computer (1).

6. The test device for simulating the pollutant migration process under the temperature-moisture coupling effect according to claim 5, characterized in that: The distributed optical fiber (4) has a temperature test accuracy of 0.1°C, a moisture content accuracy of 0.1%, and a data output point interval of 1 cm.

7. The test device for simulating the pollutant migration process under the temperature-moisture coupling effect according to any one of claims 1 to 6, characterized in that: The experiment simulating the pollutant migration process under the temperature-moisture coupling effect includes the following steps: Step 1, close the upper valve (19) and the lower valve (21), and seal the multiple sampling holes (3) with plugs; then compact the soil in layers to a certain dry density and place it in the simulated soil column cavity (11); set the power of the peristaltic pump (10) and supply water so that the rainmaker (5) can rain steadily; turn on the fan (6) and the heat source (7); Step 2, open the lower valve (21) to allow the polluted gas to enter the bottom of the soil body, and close the lower valve (21) after 1 minute to ensure the airtightness of the device; at the same time, open the plug of the sampling hole (3) every 1 minute to take samples and use a gas chromatograph (20) to detect the concentration of the polluted gas at different depths; use Comsol numerical simulation software to fit the diffusion coefficient of the polluted gas; Step 3, opening the upper valve (19) and the lower valve (21) to allow the polluted gas to enter the bottom of the soil, changing the intake pressure through the pressure controller (14), and recording the intake pressure, intake flow, exhaust flow, and exhaust pressure after the exhaust flow is stable; gradually increasing the intake pressure, recording the intake pressure, intake flow, exhaust flow, and exhaust pressure, and using Darcy's law to calculate the permeability coefficient of the polluted gas in the soil; Repeat steps 2-3 by changing the temperature and rainfall conditions, that is, simulating the transmission process of polluted gases under different temperature-moisture coupling conditions, and obtaining data on multiple groups of diffusion coefficients of polluted gases and multiple groups of permeability coefficients of polluted gases in soil; Step 4, using the distributed optical fiber (4) to respectively record the temperature and moisture of the soil at different depths, transmitting the collected data to the data acquisition device (2), and then transmitting it to the computer (1) through the data acquisition device (2).

Images