Method for testing migration behavior of heavy non-aqueous phase liquid

Abstract

The invention relates to a method for testing the migration behavior of a heavy non-aqueous phase liquid, which comprises the following steps of: filling an experimental device with a homogeneous or heterogeneous medium to form a medium layer; injecting tap water into the experimental device until the medium layer is completely wetted, standing for a set time, and simulating a stable underground aquifer; controlling the flow rate of the tap water introduced into the experimental device, and adding a DNAPLs pollutant solution into the dielectric layer at a set speed; shooting the migration condition of the DNAPLs pollutants in the dielectric layer at a set time interval, and drawing migration frontal surface diagrams at different times. The method has the beneficial effects that typical DNAPLs pollutants are selected as research objects, the migration condition of the DNAPLs in a medium along with time is observed through an image method, and the method has important scientific significance for finely depicting migration and transformation rules of the DNAPLs in soil and underground water and efficiently repairing a DNAPLs polluted site.

Description

Technical Field

[0001] The invention relates to the field of environmental technology, and in particular to a method for testing the migration behavior of a heavy non-aqueous phase liquid. Background Art

[0002] In recent years, with the rapid development of my country's economy, the development and application of organic compounds in the petrochemical industry in social production and life have become increasingly popular. However, due to improper production, transportation and storage, a large number of petrochemical products will continue to enter the soil and groundwater environment, seriously threatening the soil and groundwater ecosystem. These volatile organic pollutants, especially heavy non-aqueous phase liquids (DNAPLs), are difficult to dissolve in water, highly volatile, and have a greater density than water. The migration process in soil and groundwater presents a three-dimensional diffusion mode. Once DNAPLs pollutants penetrate into the aquifer, the residual DNAPLs will slowly dissolve under the action of groundwater flow, forming a stable source of pollution and endangering the groundwater environment for a long time. Therefore, studying the migration and transformation laws of DNAPLs in soil and groundwater and accurately characterizing them is a necessary prerequisite for achieving high-efficiency and low-loss remediation of DNAPLs contaminated sites.

[0003] At present, the fine characterization technologies of DNAPLs in actual contaminated sites include invasive drilling methods and non-invasive geophysical methods. These methods are only applicable to actual contaminated sites, and the characterization accuracy is not high, time-consuming and labor-intensive, and the cost is relatively high. At the same time, due to the complexity of the migration of DNAPLs in the soil and groundwater environment, the effectiveness and credibility of the results of a single monitoring method are poor. Therefore, in order to improve the identification accuracy of DNAPLs pollutants in different media and finely characterize the migration laws and pollution processes of DNAPLs, it is urgent to develop an experimental device and method that can simulate the actual site strata and test the migration behavior of DNAPLs in the laboratory. This is of great significance for the fine characterization of DNAPLs and site remediation. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for testing the migration behavior of heavy non-aqueous phase liquid, thereby overcoming the technical defects in the prior art in finely characterizing the migration laws of DNAPLs in soil groundwater environments.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: A method for testing the migration behavior of a heavy non-aqueous phase liquid, comprising the steps of:

[0006] Filling the experimental device with homogeneous or heterogeneous medium to form a medium layer;

[0007] Inject tap water into the experimental device until the medium layer is completely soaked, and let it stand for a set time to simulate a stable underground aquifer;

[0008] Controlling the flow rate of the tap water introduced into the experimental device, and adding the DNAPLs pollutant solution into the medium layer at a set speed;

[0009] The migration of the DNAPLs pollutants in the dielectric layer of the experimental device is photographed at set time intervals, and migration front diagrams of the DNAPLs pollutants in the dielectric layer at different times are plotted.

[0010] The beneficial effects of the present invention are as follows: the present method is used to study the migration law of DNAPLs in soil and groundwater media, typical DNAPLs pollutants are selected as research objects, the migration of DNAPLs in the experimental device medium over time is observed by imaging method, and the migration of DNAPLs in the soil and groundwater environment is studied, which has important scientific significance for finely characterizing the migration and transformation law of DNAPLs in soil and groundwater and realizing efficient remediation of DNAPLs contaminated sites.

[0011] Based on the above technical solution, the present invention can also be improved as follows.

[0012] Further, the experimental device comprises: a box body, and a water injection pool and a water outlet pool arranged in the box body, the water injection pool and the water outlet pool are respectively located on both sides of the length direction of the box body, a water inlet is arranged on the side of the water injection pool away from the water outlet pool, and a water outlet is arranged on the side of the water outlet pool away from the water injection pool;

[0013] A top cover is also provided on the top of the box body, and a micro hole is provided in the middle of the top cover for adding the DNAPLs pollutant into the box body.

[0014] The beneficial effects of adopting the above further scheme are: the setting of the water inlet, water injection pool, water outlet and water outlet pool simulates the input and output of the groundwater system, making the simulated experimental environment closer to the underground aquifer environment; by controlling the water flow rate of the water inlet and outlet to simulate the actual soil groundwater environment, it is convenient to simulate the flow state of the underground aquifer, and also realizes the precise control of the water flow rate. At the same time, the design of the top cover is convenient for closing the experimental environment in the box, and has good sealing, which can effectively prevent the volatilization of pollutants and eliminate the influence of the external environment; the setting of the micropores on the top cover is conducive to adding DNAPLs pollutants into the box. The migration of heavy non-aqueous phase liquid in the soil groundwater medium is simulated by this experimental device, which is of great significance for studying the migration and transformation laws and fine characterization of DNAPLs in soil groundwater, and realizing high-efficiency and low-loss repair of DNAPLs contaminated sites. At the same time, the structure of this experimental device is novel and firm.

[0015] Furthermore, the top cover is a transparent top cover, the box body is a rectangular transparent box body, the box body is divided by the water injection pool and the water outlet pool into a medium tank located between the water injection pool and the water outlet pool, and the medium tank is used to fill the medium layer;

[0016] The water injection pool and the water outlet pool have porous side walls on one side close to the medium tank;

[0017] At least one side of the porous side wall is detachably connected with a mesh to prevent the medium in the medium tank from entering the water injection pool or the water outlet pool.

[0018] The beneficial effects of adopting the above further scheme are: the box body and the top cover are made of transparent material, which is convenient for observing the migration of DNAPLs pollutants in the medium, and the migration of DNAPLs can be clearly observed, which is convenient for comparison and effect evaluation; the porous side wall structure of the injection tank and the outlet tank is used to simulate the groundwater seepage process, so that the experimental environment is closer to the real groundwater system, and the simulation experimental results are more accurate; the setting of the mesh on the porous side wall effectively prevents the medium particles in the medium tank from entering the injection tank or the outlet tank.

[0019] Furthermore, when the medium filled in the medium layer is a homogeneous medium, the step of filling the experimental device with the homogeneous medium to form the medium layer includes:

[0020] The cleaned homogeneous medium of the same mesh size is evenly laid in multiple layers in the medium tank from bottom to top. After each layer of the medium is laid or each layer of the medium of a set height is laid, the homogeneous medium is knocked and vibrated to make the homogeneous medium compact and uniform, simulating the actual soil layer.

[0021] The beneficial effects of adopting the above further scheme are: by accurately controlling the mesh number of the medium, the complexity and diversity of the soil layer can be simulated more accurately, thereby improving the accuracy and reliability of the experimental results. When conducting experiments, the type and mesh number of the medium can be selected as needed, so that the experiment can cover a wider range of soil conditions and meet the needs of different research purposes; by laying and tapping the vibrating medium layer by layer, it is ensured that the medium layer is compact and uniform, closer to the actual soil environment, thereby reducing the experimental error. In addition, this method is repeatable and comparable, which helps to repeat the experiment and obtain accurate experimental results.

[0022] Furthermore, when the medium filled in the medium layer is a non-homogeneous medium, the step of filling the non-homogeneous medium into the experimental device to form the medium layer includes:

[0023] The cleaned heterogeneous medium with different mesh sizes is evenly laid in the medium tank in multiple layers from bottom to top, and the heterogeneous medium is knocked and vibrated after each layer of the medium is laid or each layer of the medium with a set height is laid to make the heterogeneous medium compact and uniform, so as to simulate the actual soil layer;

[0024] The mesh number of the heterogeneous medium in each of the medium layers is different from the mesh number of the heterogeneous medium in other medium layers.

[0025] The beneficial effects of adopting the above further scheme are: by accurately controlling the mesh number of the medium, the complexity and diversity of the soil layer can be simulated more accurately, thereby improving the accuracy and reliability of the experimental results. When conducting experiments, the type and mesh number of the medium can be selected as needed, so that the experiment can cover a wider range of soil conditions and meet the needs of different research purposes; by laying and tapping the vibrating medium layer by layer, it is ensured that the medium layer is compact and uniform, closer to the actual soil environment, thereby reducing the experimental error. In addition, this method is repeatable and comparable, which helps to repeat the experiment and obtain accurate experimental results.

[0026] Furthermore, the mesh sizes of the heterogeneous media placed in the media tank decrease from top to bottom.

[0027] The beneficial effect of adopting the above further solution is that the simulation is closer to the actual soil layer.

[0028] Furthermore, in the step of injecting tap water into the experimental device until the medium layer is completely soaked, and letting it stand for a set time to simulate a stable underground aquifer, the water outlet is closed while injecting the tap water into the experimental device, and after the water completely soaks the medium, it is left to stand for 24-30 hours to stabilize the simulated underground aquifer.

[0029] The beneficial effects of adopting the above further scheme are: by injecting tap water and letting it stand, the medium layer fully absorbs water and reaches a saturated state. This process simulates the natural distribution and stable state of water in the underground aquifer, which helps to more accurately reflect the actual underground environment; after the medium layer reaches a stable water-bearing state, the migration behavior experiment of the heavy non-aqueous phase liquid is carried out to ensure the reliability and validity of the experimental results. The stability of the underground aquifer is crucial to assessing the potential pollution risk of heavy non-aqueous phase liquid to groundwater. By simulating a stable underground aquifer, the migration law and impact range of DNAPLs pollutants in the soil can be more accurately predicted, providing more reliable data support for the remediation of contaminated sites.

[0030] Furthermore, in the step of controlling the flow rate of the tap water introduced into the experimental device and adding the DNAPLs pollutant solution into the medium layer at a set speed, the flow rates of the water inlet and the water outlet are the same, so as to simulate the flow of an actual underground aquifer;

[0031] The DNAPLs pollutant solution dissolved and added with dye is dripped into the medium tank from the micropores of the top cover by a peristaltic pump, and the top cover and the micropores are sealed to prevent the DNAPLs pollutants from volatilizing.

[0032] The beneficial effects of adopting the above further scheme are: by keeping the flow rate of the water inlet and the water outlet consistent, the natural flow state of groundwater in the aquifer can be simulated more accurately, making the experimental environment close to the real soil environment; dripping the DNAPLs pollutant solution at a set speed can simulate the initial release and diffusion process of pollutants in groundwater, which is helpful to understand the behavioral characteristics of pollutants in the groundwater system; while dripping the pollutant solution, the top cover and micropores are closed, which effectively prevents the volatilization of DNAPLs pollutants, ensures the stability of pollutant concentration during the experiment, and improves the reliability of the experimental results.

[0033] Further, in the step of photographing the migration of DNAPLs pollutants in the dielectric layer of the experimental device at set time intervals and drawing migration front diagrams of the DNAPLs pollutants in the dielectric layer at different times,

[0034] When the medium filled in the medium tank is the homogeneous medium, take photos of the migration of the DNAPLs pollutants in the medium tank from the front of the box every 20-30 minutes, and import the photos at different times into AutoCAD software to generate a migration front map;

[0035] When the medium filled in the medium tank is the heterogeneous medium, the migration of the DNAPLs pollutants in the medium tank is photographed from the front of the box every 50-60 minutes, and the photographs at different times are imported into AutoCAD software to generate a migration front map.

[0036] The beneficial effects of adopting the above further scheme are: by setting reasonable time intervals for shooting, the migration of DNAPLs pollutants in different media over time can be accurately recorded. Different shooting intervals are set for homogeneous media and heterogeneous media, respectively, to ensure the accuracy and representativeness of the data, which is helpful to understand the migration mechanism of pollutants; by taking pictures with a camera and importing the pictures into AutoCAD software for drawing migration front maps, the migration process of pollutants that was originally difficult to directly observe can be converted into intuitive and clear images. Visualization methods make it easy for researchers to quickly understand the experimental results, and provide strong support for subsequent low-loss remediation of DNAPLs contaminated sites; through the migration front map, the migration and transformation laws of DNAPLs over time can be finely portrayed, which is of great significance for evaluating the diffusion range of pollutants, predicting pollution trends, and formulating effective control measures.

[0037] Furthermore, the homogeneous medium and the heterogeneous medium are both made of white quartz sand;

[0038] The DNAPLs pollutants are one or more of trichloroethylene, dibenzofuran or carbazole.

[0039] The beneficial effects of adopting the above further scheme are: white quartz sand makes the distribution and migration process of pollutants in the medium clearly visible; the diversity of pollutant types can simulate the behavioral characteristics of different types of DNAPLs pollutants in groundwater. DNAPLs pollutants have a variety of options. By selecting a variety of DNAPLs pollutants for experiments, the migration and transformation laws of different pollutants under the same conditions can be compared, providing rich experimental data and theoretical support for groundwater pollution remediation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A three-dimensional schematic diagram of a test device in an embodiment of the present invention;

[0041] Figure 2 It is a front view of the experimental device in the embodiment of the present invention;

[0042] Figure 3 A top view of an experimental device in an embodiment of the present invention;

[0043] Figure 4 This is a migration front diagram of DNAPLs pollutants in a homogeneous medium in Example 1 of the present invention;

[0044] Figure 5 This is a migration front diagram of DNAPLs pollutants in a heterogeneous medium in Example 2 of the present invention.

[0045] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0046] 1. Box body; 2. Water inlet; 3. Water outlet; 4. Water filling pool; 5. Water outlet pool; 6. Top cover. DETAILED DESCRIPTION

[0047] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0048] The present invention provides a method for testing the migration behavior of a heavy non-aqueous phase liquid. The method is mainly implemented based on an experimental device that can test the migration behavior of a heavy non-aqueous phase liquid. Figure 1-3 As shown, the specific experimental device includes: a box body 1, a water injection pool 4 and a water outlet pool 5 are respectively provided on both sides of the length direction of the box body 1, the water injection pool 4 and the water outlet pool 5 have roughly the same area, and a water inlet 2 is provided on the side of the water injection pool 4 away from the water outlet pool 5, and the water inlet 2 is provided in the middle of the side of the box body 1; a water outlet 3 is provided on the side of the water outlet pool 5 away from the water injection pool 4, and the water outlet 3 is provided at the other side of the box body 1 near the bottom. In addition, a top cover 6 is also provided on the top of the box body 1, and a micro hole is opened in the middle of the top cover 6; in this embodiment, the diameter of the micro hole is 3 mm.

[0049] In this embodiment, the setting of the water inlet 2, the water injection pool 4, the water outlet 3 and the water outlet pool 5 simulates the input and output of the groundwater system, making the simulated experimental environment closer to the underground aquifer environment; by controlling the water flow rate of the water inlet 2 and the water outlet 3 to simulate the actual soil groundwater environment, it is convenient to simulate the flow state of the underground aquifer, and also realizes the precise control of the water flow rate. At the same time, the design of the top cover 6 is convenient for closing the experimental environment in the box 1, and has good sealing, which can effectively prevent the volatilization of pollutants and eliminate the influence of the external environment; the setting of the micropores on the top cover 6 is conducive to adding DNAPLs pollutants into the box 1. The migration of heavy non-aqueous phase liquid in the soil groundwater medium is simulated by this experimental device, which is of great significance for studying the migration and transformation laws and fine characterization of DNAPLs in soil groundwater, and realizing high-efficiency and low-loss repair of DNAPLs contaminated sites.

[0050] like Figure 1-3 As shown, in this embodiment, the box 1 adopts a rectangular container. In order to facilitate the observation of the migration of DNAPLs pollutants in the medium, the box 1 is made of a transparent material, such as a transparent acrylic plate. Correspondingly, the top cover 6 can also be a transparent top cover made of a transparent acrylic plate. The size of the box 1 is: 70 cm long, 50 cm high, and 5 cm wide. The water inlet 2 and the water outlet 3 are both PVC valves that can adjust the water flow, which is convenient for adjusting the changes in the water flow. As a preferred embodiment, the length of the water injection pool 4 and the water outlet pool 5 is 5 cm, the height is 50 cm, and the width is 5 cm.

[0051] A medium tank is provided between the water injection tank 4 and the water outlet tank 5 in the box 1. During the experiment, a medium layer is filled into the medium tank. The water injection tank 4 and the water outlet tank 5 are both provided with porous side walls on one side close to the medium tank. The side walls of the water injection tank 4 and the water outlet tank 5 each have micropores for water flow, which can be used to simulate the actual groundwater environment.

[0052] As a preferred solution, a mesh can be detachably connected to at least one side of the porous side wall of the water injection pool 4 and the water outlet pool 5 to prevent the medium in the medium tank from entering the water injection pool 4 or the water outlet pool 5; wherein the mesh can be installed on one side of the porous side wall close to the medium tank, or the mesh can be detachably installed on both sides of the porous side wall, and no limitation is given here. In this embodiment, the mesh can be polyester mesh, and specifically 200 mesh polyester mesh can be used.

[0053] In the above scheme, the box body 1 and the top cover 6 are made of transparent material, which is convenient for observing the migration of DNAPLs pollutants in the medium and can intuitively display the migration behavior of DNAPLs pollutants under specific conditions; the porous side wall structure of the injection tank 4 and the outlet tank 5 simulates the groundwater seepage process, making the experimental environment closer to the real groundwater system and making the simulation experimental results more accurate; the setting of the mesh on the porous side wall effectively prevents the medium particles in the medium tank from entering the injection tank 4 or the outlet tank 5.

[0054] Specifically, a method for testing the migration behavior of a heavy non-aqueous phase liquid comprises the following steps:

[0055] S1: Homogeneous or heterogeneous medium is loaded into the experimental device to form a medium layer. When conducting the experiment, the same type of medium can be used for the experiment, and a homogeneous medium or a heterogeneous medium can be obtained by setting the mesh size of the medium. For example, quartz sand of different particle sizes can be loaded to simulate the actual soil stratum conditions, which is simple and convenient to operate. It can be imagined that different types of media can also be selected according to the actual soil environment to be simulated to be filled into the medium tank to simulate the actual soil layer, which is not limited here.

[0056] Specifically, in step S1, when the medium loaded into the medium tank is a homogeneous medium, the specific loading steps are:

[0057] Lay multiple layers of cleaned homogeneous media of the same mesh size evenly in the media tank from bottom to top. After laying each layer of media or laying a certain height, knock and vibrate the homogeneous media to make the homogeneous media compact and uniform, simulating the actual soil layer.

[0058] When the medium filled in the medium layer is a non-homogeneous medium, the steps of filling the non-homogeneous medium into the experimental device to form the medium layer include:

[0059] The cleaned heterogeneous media of different mesh sizes are evenly laid in multiple layers in the media tank from bottom to top. After laying each layer of the media or laying a certain height, the heterogeneous media is knocked and vibrated to make the heterogeneous media compact and uniform, simulating the actual soil layer.

[0060] The mesh number of the heterogeneous medium in each medium layer is different from the mesh number of the heterogeneous medium in other medium layers. It can be imagined that the mesh number of the heterogeneous medium in each medium layer can be reasonably set according to the actual situation of the desired simulated soil layer to achieve a simulation effect closest to the actual soil layer.

[0061] In a feasible embodiment, in order to simulate the actual soil layer, the mesh size of the heterogeneous media placed from top to bottom in the media tank decreases successively, that is, the particle size of the heterogeneous media placed from top to bottom increases successively.

[0062] In the above steps of filling the homogeneous and heterogeneous media, the overall height of the medium layer filled in the medium tank is 45-48 cm. After each layer or each 5-8 cm is laid, the homogeneous medium or heterogeneous medium is knocked and vibrated to make the medium compact and uniform.

[0063] It is conceivable that when filling homogeneous or heterogeneous media, the laying heights of the various layers of media in the multi-layer media layer may be the same or different, and may be adaptively adjusted according to experimental requirements to simulate the environment closest to the actual soil layer.

[0064] In the above scheme, by precisely controlling the mesh size of the medium, the complexity and diversity of the soil layer can be simulated more accurately, thereby improving the accuracy and reliability of the experimental results. When conducting experiments, the type and mesh size of the medium can be selected as needed, so that the experiment can cover a wider range of soil conditions and meet the needs of different research purposes; by laying and tapping the vibrating medium layer by layer, the medium layer is ensured to be compact and uniform, closer to the actual soil environment, thereby reducing the experimental error. In addition, this method is repeatable and comparable, which helps to repeat the experiment and obtain accurate experimental results.

[0065] S2: Inject tap water into the experimental device until the medium layer is completely soaked, and let it stand for a set time to simulate a stable underground aquifer.

[0066] Specifically, in step S2, tap water is introduced into the box 1 through the water inlet 2, and the water outlet 3 is closed while the water is injected. After the tap water completely soaks the medium, it is left to stand for a period of time, wherein it is left to stand for 24-30 hours, so that the simulated underground aquifer is stable.

[0067] In the above scheme, by injecting tap water and letting it stand, the medium layer fully absorbs water and reaches a saturated state. This process simulates the natural distribution and stable state of water in the underground aquifer, which helps to more accurately reflect the actual underground environment. After the medium layer reaches a stable water-bearing state, the migration behavior experiment of heavy non-aqueous phase liquid is carried out to ensure the reliability and validity of the experimental results. The stability of the underground aquifer is crucial to assessing the potential pollution risk of heavy non-aqueous phase liquid to groundwater. By simulating a stable underground aquifer, the migration law and impact range of DNAPLs pollutants in the soil can be more accurately predicted, providing more reliable data support for the remediation of contaminated sites.

[0068] S3: Control the flow rate of tap water entering the experimental device, and drip the DNAPLs pollutant solution into the medium layer at a set speed.

[0069] In step S3, the flow rates of the water inlet 2 and the water outlet 3 are the same, and the flow rate is preferably controlled at 1.5-2mL / min to simulate the smooth flow of the actual underground aquifer. In some feasible embodiments, pollutants are added to the medium tank by a peristaltic pump, wherein the peristaltic pump speed is preferably controlled at 10-15rpm, and the dissolved DNAPLs pollutant solution is dripped into the medium tank from the micropores of the top cover 6 by the peristaltic pump, and the top cover 6 and the micropores are closed at the same time to prevent the volatilization of DNAPLs pollutants. It can be imagined that during the experiment, the speed of the peristaltic pump can be adjusted according to the experimental requirements, and multiple experiments can be performed by controlling the variable of the dripping speed of the DNAPLs pollutants to make the simulation experiment closest to the situation in the actual environment.

[0070] In this embodiment, the DNAPLs pollutant can be one or more of trichloroethylene, dibenzofuran or carbazole, so as to simulate the behavioral characteristics of different types of DNAPLs pollutants in groundwater. There are many options for DNAPLs pollutants. By selecting a variety of DNAPLs pollutants for experiments, the migration and transformation laws of different pollutants under the same conditions can be compared, providing rich experimental data and theoretical support for groundwater pollution remediation.

[0071] In the above scheme, by keeping the flow rate of the water inlet 2 and the water outlet 3 consistent, the natural flow state of groundwater in the aquifer can be more accurately simulated, making the experimental environment close to the real soil environment; dripping the DNAPLs pollutant solution at a set speed can simulate the initial release and diffusion process of pollutants in groundwater, which is helpful to understand the behavioral characteristics of pollutants in the groundwater system; while dripping the pollutant solution, the top cover 6 and the micropores are closed, which effectively prevents the volatilization of DNAPLs pollutants, ensures the stability of pollutant concentration during the experiment, and improves the reliability of the experimental results.

[0072] S4: photograph the migration of DNAPLs pollutants in the dielectric layer of the experimental device at set time intervals, and draw migration front diagrams of DNAPLs pollutants in the dielectric layer at different times.

[0073] In step S4, a camera is used to photograph the migration of DNAPLs pollutants in the medium tank, wherein the camera is set in the middle front of the medium tank, that is, the camera is located directly in front of the medium tank. The time interval required for photographing is determined according to the type of medium filled in the experimental device. When the medium filled in the medium tank is a homogeneous medium, the camera takes photos of the migration of DNAPLs pollutants in the medium of the box 1 every 20-30 minutes; when the medium filled in the medium tank is a heterogeneous medium, because the migration speed of DNAPLs pollutants in the heterogeneous medium is slow, the camera is set to take photos of the migration of DNAPLs pollutants in the medium of the box 1 every 50-60 minutes.

[0074] The migration front map of DNAPLs pollutants in the medium layer was drawn using AutoCAD software, and photos at different times were imported into the AutoCAD software to independently generate the migration front map.

[0075] In the above scheme, by setting reasonable time intervals for shooting, the migration of DNAPLs pollutants in different media over time can be accurately recorded. Different shooting intervals are set for homogeneous media and heterogeneous media, respectively, to ensure the accuracy and representativeness of the data, which is helpful to understand the migration mechanism of pollutants. By taking pictures with a camera and importing the pictures into AutoCAD software for drawing migration front maps, the migration process of pollutants that was originally difficult to observe directly can be converted into intuitive and clear images. Visualization methods make it easy for researchers to quickly understand the experimental results and provide strong support for subsequent low-loss remediation of DNAPLs contaminated sites. Through the migration front map, the migration and transformation laws of DNAPLs over time can be finely portrayed, which is of great significance for evaluating the diffusion range of pollutants, predicting pollution trends, and formulating effective control measures.

[0076] Example 1

[0077] In this embodiment, an experimental device capable of testing the migration behavior of heavy non-aqueous phase liquid is used, and 200-mesh polyester mesh is installed on both sides of the medium tank of the box 1 in the early stage of the experiment to prevent the quartz sand medium from entering the water injection pool 4 and the water outlet pool 5. The medium is white quartz sand, and the DNAPLs pollutant is dibenzofuran. During the experiment, Sudan III is added to the dibenzofuran dissolved in ethanol. The visibility of dibenzofuran in the medium is significantly enhanced by adding Sudan III. The white quartz sand is combined with the pollutant added with the dye, so that the distribution and migration process of the pollutant in the medium become clearly visible; the migration behavior of dibenzofuran in the homogeneous medium is analyzed by image method, including the following steps:

[0078] Step 1, filling the homogeneous medium layer:

[0079] In this embodiment, 20-40 mesh white quartz sand is filled in the medium tank as a homogeneous medium, and the cleaned 20-40 mesh quartz sand is evenly poured into the medium tank of the box 1 through a small beaker. After each 5.0 cm quartz sand medium layer is filled, the quartz sand in the medium tank is gently tapped with a rubber hammer, and the side panels on the left and right sides of the box 1 are tapped to make the quartz sand dense and uniform, wherein the overall filling height of the quartz sand medium layer in the medium tank is 45-48 cm.

[0080] Step 2, introduce tap water into the box 1 through the water inlet 2, and close the water outlet 3 at the same time. After the water completely soaks the medium, let it stand for 24 hours to allow the simulated underground aquifer to stabilize.

[0081] By controlling the flow rates of water inlet 2 and water outlet 3 to be consistent, the flow rates of water inlet 2 and water outlet 3 are controlled to be 1.5 mL / min, thereby simulating the smooth flow of the actual underground aquifer.

[0082] Step 3, slowly drip the dibenzofuran solution dissolved in ethanol into the medium tank from the micropores of the top cover 6 through a peristaltic pump, the flow rate of the peristaltic pump is 12 rpm, and the top cover 6 and the micropores are sealed with raw tape to prevent dibenzofuran from volatilizing.

[0083] Step 4: At the same position in front of the experimental device, take photos of the migration of the dibenzofuran solution in the quartz sand medium with a camera every 30 minutes, and use AutoCAD software to draw the migration front diagram of dibenzofuran in the homogeneous medium at different times.

[0084] like Figure 4 As shown, since the quartz sand in the medium tank of the experimental device box 1 has the same particle size and large particles, the vertical migration speed of DNAPLs is faster than that in the heterogeneous medium. At this time, the longitudinal migration speed is much greater than the lateral migration speed, and the time it takes to migrate to the bottom of the device box is also shorter than that in the heterogeneous medium.

[0085] Example 2

[0086] In this embodiment, an experimental device capable of testing the migration behavior of heavy non-aqueous phase liquid is used, and 200-mesh polyester mesh is installed on both sides of the medium tank of the box 1 in the early stage of the experiment to prevent the quartz sand medium from entering the water injection pool 4 and the water outlet pool 5. The medium is white quartz sand, and the DNAPLs pollutant is dibenzofuran. During the experiment, Sudan Red III is added to the dibenzofuran dissolved in ethanol, and the migration behavior of dibenzofuran in the heterogeneous medium is analyzed by image method, which includes the following steps:

[0087] Step 1: Filling the heterogeneous medium layer:

[0088] In this embodiment, white quartz sand of different mesh sizes is used as the heterogeneous medium in the medium tank.

[0089] The medium tank of the experimental device is filled with white quartz sand of 80-120 mesh, 40-60 mesh, 20-40 mesh and 8-16 mesh from top to bottom, that is, the mesh size of the medium filled from top to bottom gradually decreases, thereby simulating a non-homogeneous soil layer. The thickness of each quartz sand medium layer is 12 cm. Then, the cleaned quartz sand of different mesh sizes is poured evenly from left to right into the medium tank of box 1 through a small beaker. After filling each 5.0 cm quartz sand medium layer, the quartz sand in the medium tank is gently tapped with a rubber hammer, and the side panels on the left and right sides of box 1 are knocked to make the quartz sand dense and uniform. The total filling height is 48 cm.

[0090] Step 2, introduce tap water into the box 1 through the water inlet 2, and close the water outlet 3 at the same time. After the water completely soaks the medium, let it stand for 24 hours to allow the simulated underground aquifer to stabilize.

[0091] By controlling the flow rates of water inlet 2 and water outlet 3 to be consistent, the flow rates of water inlet 2 and water outlet 3 are controlled to be 1.5 mL / min, thereby simulating the smooth flow of the actual underground aquifer.

[0092] Step 3, slowly drip the dibenzofuran solution dissolved in ethanol into the medium tank from the micropores of the top cover 6 through a peristaltic pump, the flow rate of the peristaltic pump is 12 rpm, and the top cover 6 and the micropores are sealed with raw tape to prevent dibenzofuran from volatilizing.

[0093] Step 4: At the same position in front of the experimental device, take photos of the migration of the dibenzofuran solution in the quartz sand medium with a camera every 60 minutes, and use AutoCAD software to draw the migration front diagram of dibenzofuran in the heterogeneous medium at different times.

[0094] like Figure 5As shown, compared with Example 1, due to the smaller particle size of the quartz sand in the upper medium tank of the experimental device box 1, the vertical migration speed of DNAPLs is slower than that in the homogeneous medium. At this time, the lateral migration speed is greater than the longitudinal migration speed, so it takes a longer time for it to migrate to the bottom of the device box 1.

[0095] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for testing the migration behavior of a heavy non-aqueous phase liquid, characterized in that the steps include: Filling the experimental device with homogeneous or heterogeneous medium to form a medium layer; Inject tap water into the experimental device until the medium layer is completely soaked, and let it stand for a set time to simulate a stable underground aquifer; Controlling the flow rate of the tap water introduced into the experimental device, and adding the DNAPLs pollutant solution into the medium layer at a set speed; The migration of the DNAPLs pollutants in the dielectric layer of the experimental device is photographed at set time intervals, and migration front diagrams of the DNAPLs pollutants in the dielectric layer at different times are plotted.

2. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 1, characterized in that: The experimental device comprises: a box (1), and a water injection pool (4) and a water outlet pool (5) arranged in the box (1); the water injection pool (4) and the water outlet pool (5) are respectively located on both sides of the length direction of the box (1); a water inlet (2) is arranged on the side of the water injection pool (4) away from the water outlet pool (5); and a water outlet (3) is arranged on the side of the water outlet pool (5) away from the water injection pool (4); The top of the box body (1) is also provided with a top cover (6), and a microhole is provided in the middle of the top cover (6) for adding the DNAPLs pollutant into the box body (1).

3. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 2, characterized in that: The top cover (6) is a transparent top cover, the box body (1) is a rectangular transparent box body, the box body (1) is divided by the water injection pool (4) and the water outlet pool (5) into a medium tank located between the water injection pool (4) and the water outlet pool (5), and the medium tank is used to fill the medium layer; The water injection pool (4) and the water outlet pool (5) have porous side walls on one side close to the medium tank; At least one side of the porous side wall is detachably connected with a mesh to prevent the medium in the medium tank from entering the water injection pool (4) or the water outlet pool (5).

4. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 3, characterized in that: When the medium filled in the medium layer is a homogeneous medium, the step of filling the experimental device with the homogeneous medium to form the medium layer includes: The cleaned homogeneous medium of the same mesh size is evenly laid in multiple layers in the medium tank from bottom to top. After each layer of the medium is laid or each layer of the medium of a set height is laid, the homogeneous medium is knocked and vibrated to make the homogeneous medium compact and uniform, simulating the actual soil layer.

5. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 4, characterized in that: When the medium filled in the medium layer is a non-homogeneous medium, the step of filling the non-homogeneous medium into the experimental device to form the medium layer includes: The cleaned heterogeneous medium with different mesh sizes is evenly laid in the medium tank in multiple layers from bottom to top, and the heterogeneous medium is knocked and vibrated after each layer of the medium is laid or each layer of the medium with a set height is laid to make the heterogeneous medium compact and uniform, so as to simulate the actual soil layer; The mesh number of the heterogeneous medium in each of the medium layers is different from the mesh number of the heterogeneous medium in other medium layers.

6. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 5, characterized in that: The mesh sizes of the heterogeneous media placed from top to bottom in the media tank decrease successively.

7. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 4 or 6, characterized in that: In the step of injecting tap water into the experimental device until the medium layer is completely soaked, and leaving it to stand for a set time to simulate a stable underground aquifer, the water outlet (3) is closed while injecting tap water into the experimental device, and after the water completely soaks the medium, the medium is left to stand for 24-30 hours to stabilize the simulated underground aquifer.

8. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 7, characterized in that: In the step of controlling the flow rate of the tap water introduced into the experimental device and adding the DNAPLs pollutant solution into the medium layer at a set speed, the flow rates of the water inlet (2) and the water outlet (3) are the same, so as to simulate the flow of an actual underground aquifer; The DNAPLs pollutant solution dissolved and added with a dye is dripped into the medium tank from the micropores of the top cover (6) by a peristaltic pump, and the top cover (6) and the micropores are sealed to prevent the DNAPLs pollutants from volatilizing.

9. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 8, characterized in that: In the step of photographing the migration of DNAPLs pollutants in the dielectric layer of the experimental device at set time intervals and drawing migration front diagrams of the DNAPLs pollutants in the dielectric layer at different times, When the medium filled in the medium tank is the homogeneous medium, the migration of the DNAPLs pollutants in the medium tank is photographed from the front of the box (1) every 20-30 minutes, and the photographs at different times are imported into AutoCAD software to generate a migration front map; When the medium filled in the medium tank is the heterogeneous medium, the migration of the DNAPLs pollutants in the medium tank is photographed from the front of the box (1) every 50-60 minutes, and the photographs at different times are imported into AutoCAD software to generate a migration front map.

10. A method for testing the migration behavior of a heavy non-aqueous phase liquid according to claim 9, characterized in that: The homogeneous medium and the heterogeneous medium are both made of white quartz sand; The DNAPLs pollutants are one or more of trichloroethylene, dibenzofuran or carbazole.

Images