Device and method for simulating migration of pollutants under mining and tidal conditions

Abstract

The invention discloses a device for simulating migration of pollutants under mining and tidal conditions. The device comprises an aquifer loading tank, a pollution tank simulation pollution source and a plastic pipe simulation pumping well are arranged in the tank; the left side and the right side of the aquifer loading groove are divided into a salt water chamber and a fresh water chamber by acrylic plates with seepage holes; the same constant water head device is arranged in the salt-fresh water chamber; and a tide device is arranged on the salt water chamber to simulate the tidal effect of seawater. The positions of the pollution tank and the pumping well are not fixed and can be adjusted; a plurality of salinity concentration monitoring devices are arranged on the rear side of the aquifer loading groove; the inhomogeneous medium of the coastal zone aquifer is simulated by filling the aquifer loading groove with sand samples in a layered manner, so that seawater invasion is simulated. The device can simulate the migration of pollutants in the aquifer under different tide conditions and exploitation conditions, monitor the concentration change of the pollutants and the water pressure change of each part in the horizontal direction in real time, and can simulate the migration situation of the pollutants under the combined action of tide coupling underground water exploitation.

Description

Technical Field

[0001] The present invention belongs to the field of coastal hydrogeological research, and particularly relates to a device and method for simulating the migration of pollutants in heterogeneous aquifers in the coastal zone under the coupling of tidal action and groundwater extraction. Background Art

[0002] The coastal zone has always been a heavily polluted area in the economic development of coastal regions. The coastal aquifer is also a highly vulnerable ecological region, which is not only affected by inland pollutants carried during the process of groundwater flowing into the sea, but also affected by seawater intrusion. In addition, due to tidal effects and inland artificial groundwater extraction, the flow and migration of pollutants in the coastal aquifer system are relatively complex. Therefore, considering the heterogeneity of the coastal aquifer, it is of great practical significance and value to study the migration law of land-source pollutants in coastal groundwater, with particular emphasis on the comprehensive influence of artificial conditions (groundwater extraction) and natural conditions (tidal action) on pollutants in the coastal aquifer. Summary of the Invention

[0003] Object of the Invention: The technical problem to be solved by the present invention is to provide an experimental device for simulating the influence of tidal action and groundwater extraction on pollutants in coastal groundwater and its usage method.

[0004] Technical Solution: To solve the above technical problem, the present invention provides a device for simulating the migration of pollutants in heterogeneous aquifers in the coastal zone under the coupling of tidal action and groundwater extraction, which includes an aquifer loading tank (8) used as a seepage chamber, and the tank body is placed on a bracket (14); a pollution tank (2) is arranged in the aquifer loading tank (8) to simulate the pollution source, and a plastic pipe (4) is used to simulate a pumping well; the left and right sides of the aquifer loading tank (8) are separated by a first acrylic plate with seepage holes (7) and a second acrylic plate with seepage holes (9) to form a saltwater chamber (6) and a freshwater chamber (10);

[0005] The same constant head device (17) is arranged in the saltwater chamber (6) and the freshwater chamber (10); the saltwater chamber (6) and the freshwater chamber (10) are respectively connected to a saltwater tank (12) and a freshwater tank (15) below them; a tidal device (1) is arranged on the saltwater chamber (6) to simulate the seawater tidal action;

[0006] Among them, the saltwater chamber (6), the saltwater tank (12), and the first peristaltic pump (13) are connected by rubber tubes to form a seawater simulation device; the freshwater chamber (10), the freshwater tank (15), and the second peristaltic pump (16) are connected by rubber tubes to form a freshwater simulation device.

[0007] Furthermore, filter meshes are covered on both the first acrylic plate with seepage holes (7) and the second acrylic plate with seepage holes (9).

[0008] Furthermore, circular water-permeable holes are evenly arranged at the bottom of the pollution tank (2), and a filter screen is covered at the bottom thereof to prevent sand samples from entering the pollution tank (2).

[0009] Furthermore, 72 sampling ports (18) in 6 rows and 12 columns are arranged at the rear side of the aquifer loading tank (8) as monitoring holes for extracting the solution concentrations at different positions in real time. A faucet is provided at the sampling port for directly taking stable water samples. Moreover, a filter screen is pasted inside the sampling port to isolate sand grains.

[0010] Furthermore, transparent rubber hoses are installed on the faucets of the 12 sampling ports (19) at the lowermost layer and are placed on the left outer wall of the saltwater chamber (6) for monitoring the water head changes at different positions in real time.

[0011] In addition, the present invention provides a specific implementation and operation method for simulating the migration of pollutants in a heterogeneous coastal aquifer under the coupling of tidal action and groundwater extraction conditions by using the device described in any one of the above. The method includes the following steps:

[0012] Step S1: Simulate the heterogeneous aquifer medium according to the experimental requirements. Prepare sand samples of different particle sizes. Inject water with a height of 20 cm into the aquifer loading tank (8), put the dry sand samples into the water for soaking to fully saturate the sand. Repeat the operation, and help to compact the sand samples when increasing the depth each time until the required height of the sand samples for the experiment is reached.

[0013] Step S2: Paste filter screens at the lower ends of the prepared pumping well (4) and the customized pollution tank (2) to isolate sand grains. Place the pollution tank (2) for simulating the pollutant injection at a distance d1 from the saltwater chamber and at a depth h from the bottom of the loading tank (8); insert the pumping well (4) for simulating groundwater extraction into the sand samples and place it at a distance d2 from the saltwater chamber.

[0014] Step S3: Connect the third peristaltic pump (3) and the pollution tank (2) with a rubber hose, and connect the fourth peristaltic pump (5) and the pumping well (4). Preset the injection rate v1 of the pollutants and the pumping rate v2 required for the experiment according to the experimental needs.

[0015] Step S4: Fix the tidal device (1) on the upper part of the saltwater chamber (6), and preset the tidal amplitude and period conditions required for the experiment; connect the tidal device (1) and the saltwater constant head device (17), insert the steel bar at the upper part of the saltwater constant head device (17) into the fixing ring of the tidal device (1), and use nuts to fix it above and below the fixing ring.

[0016] Step S5: Close the drain valve (11), and turn on the first peristaltic pump (13) and the second peristaltic pump (16) to form a stable water circulation in both the seawater simulation device and the fresh water simulation device, so as to form a stable flow in the aquifer in the aquifer loading tank (8).

[0017] Step S6: Adjust and fix the heights of the saline water head and the fresh water head according to the experiment. Meanwhile, adjust the water volume in the saline water tank (12) to keep the saline water head stable.

[0018] Step S7: Prepare seawater and pollutant solutions in two prepared containers respectively to simulate seawater intrusion and the migration of pollutants. Add a certain amount of NaCl and the corresponding tracer into each container so that when the prepared seawater solution replaces the fresh water in the saline water tank (12) at the beginning of the experiment, the seawater concentration in the saline water chamber (6) is 35 g / L. Connect the pollution tank (2) and the container with the configured pollutants through a rubber tube so that the pollutant concentration entering the pollution tank (2) from the container through the third peristaltic pump (3) is also 35 g / L.

[0019] Step S8: Check whether the saline and fresh water heads are stable, and observe whether the water head state in the rubber tube on the left outer wall of the saline water chamber (6) is normal. If there are bubbles in the rubber tube resulting in the inability to accurately display the water head height at the sampling port (19) at the bottom layer of the aquifer loading tank (8), adjust it so that the water head state in the rubber tube on the left outer wall of the saline water chamber (6) is normal.

[0020] Step S9: Place the camera in front to start video recording for the experiment. Put the seawater with the tracer into the saline water tank (12) so that the seawater enters the saline water chamber (6) from the saline water tank (12) to simulate seawater intrusion. Observe the seawater intrusion situation until a stable saline water wedge is formed. Take samples through the rear sampling hole (18) at regular intervals, record the seawater conductivity, and record the length, height of the saline water wedge and the water level data at the same time.

[0021] Step S10: After the saline water wedge is stable, turn on the third peristaltic pump (3) and the third peristaltic pump (5). Start pumping water while releasing pollutants, and turn on the tidal device (1) at the same time to simulate the migration of pollutants in the heterogeneous coastal aquifer under the coupling of tidal action and groundwater extraction.

[0022] Step S11: During the experiment, record the size of the saline water wedge and the infiltration area of the pollutants and record the time nodes. Take samples at regular intervals to measure the conductivity of the saline water and the pollutants, record and draw the conductivity change graph. End this group of experiments when the pollutants are pumped out or come into contact with the saline water wedge, and turn off the video recording.

[0023] Advantageous effects: Compared with the prior art, the technical solution of the present invention has the following advantageous technical effects:

[0024] The present invention can simulate the migration of pollutants in the aquifer under different tidal conditions and extraction conditions, monitor the change of pollutant concentration and the water pressure change at each part in the horizontal direction in real time, can simulate the migration situation of pollutants under the combined action of tidal coupling and groundwater extraction, and study the laws therein. Description of the Drawings

[0025] Figure 1 is a schematic diagram of the overall structure of the simulation device;

[0026] Figure 2 is Figure 1 the front view of the brackish water chamber in

[0027] Figure 3 is Figure 1 a schematic diagram of the position of the back sampling hole in the aquifer loading tank in Specific Embodiment Method

[0029] Next, the technical solution of the present invention will be clearly and completely described in conjunction with the drawings. It should be noted that the embodiments described in the present invention are part of the embodiments of the present invention, rather than all of the embodiments.

[0030] As Figures 1 - 3 shown, this embodiment provides a device for simulating the migration of pollutants in heterogeneous coastal aquifers under the coupling of tidal action and groundwater extraction conditions. Figure 1 For the overall structure of this device, it includes an aquifer loading tank (8), which is used as a seepage chamber, and the tank body is placed on a bracket (14); a pollution tank (2) is provided in the aquifer loading tank (8) to simulate the pollution source, and a plastic pipe (4) is used to simulate the pumping well; the left and right sides of the aquifer loading tank (8) are separated by a first acrylic plate with seepage holes (7) and a second acrylic plate with seepage holes (9) to form a brackish water chamber (6) and a fresh water chamber (10).

[0031] The same constant head device (17) is provided in the brackish water chamber (6) and the fresh water chamber (10); the brackish water chamber (6) and the fresh water chamber (10) are respectively connected to the brackish water tank (12) and the fresh water tank (15) below them; a tidal device (1) is provided on the brackish water chamber (6) to simulate the seawater tidal action.

[0032] Among them, the brackish water chamber (6), the brackish water tank (12), and the first peristaltic pump (13) are connected by rubber tubes to form a seawater simulation device; the fresh water chamber (10), the fresh water tank (15), and the second peristaltic pump (16) are connected by rubber tubes to form a fresh water simulation device.

[0033] Specifically, the size of the aquifer loading tank (8) is 200 cm × 25 cm × 80 cm, and it is separated from the brackish water chamber (6) and the fresh water chamber (10) by acrylic plates with holes. At the same time, in order to prevent the sand grains in the seepage chamber from flowing out of the two side boundaries, filter meshes are covered on both side plates. During the experiment, this aquifer loading tank (8) is used to simulate the coastal aquifer.

[0034] Specifically, the size of the saltwater chamber (6) and the freshwater chamber (10) is the same, which is 20 cm × 25 cm × 80 cm, and the same constant head device (17) is installed inside, such as Figure 2 shown. During the experiment, after fixing the hollow cylinder constant head device (17) at the required head height, the water overflowing from the saltwater and freshwater chambers (6) and (10) will flow back into the lower saltwater and freshwater tanks (12) and (15) to maintain a stable head.

[0035] Specifically, the size of the saltwater tank (12) and the freshwater tank (15) is the same, which is 25 cm × 25 cm × 70 cm. The water in the tanks is pumped into the upper saltwater and freshwater chambers (6) and (10) through the first peristaltic pump (13) and the second peristaltic pump (16) respectively. At the same time, a drain pipe (11) is installed at the bottom of the saltwater tank (12) to drain water, which can also control the water volume in the device during the experiment.

[0036] Specifically, a cubic pollution tank (2) customized with acrylic plates is installed in the aquifer loading tank (8) to simulate a continuous pollution source with a fixed concentration. The size of the pollution tank (2) is 24 cm × 24 cm × 20 cm. Circular permeable holes are evenly arranged at the bottom of the pollution tank (2), and a filter screen is covered at the bottom to prevent sand samples from entering the pollution tank (2). In this embodiment, the bottom of the pollution tank (2) is 50 cm away from the bottom of the boundary. During the experiment, the pollutant solution in the pollution tank (2) maintains a stable pollutant head through the third peristaltic pump (3) to simulate the infiltration of pollutants into groundwater at a constant rate. At the same time, an impermeable plastic pipe is arranged on the right side of the pollution tank (2) to simulate a pumping well (4), and the groundwater in the seepage chamber is pumped out from the pumping well (4) through the fourth peristaltic pump (5) to simulate groundwater extraction.

[0037] Specifically, as Figure 3 shown, 72 sampling ports (18) in 6 rows and 12 columns are arranged at the rear side of the aquifer loading tank (8) as monitoring holes, which can be used to extract the solution concentration at different positions in real time. A faucet is installed at the sampling port, which can be used to directly obtain a stable water sample. A filter screen is pasted inside the sampling port to isolate sand grains to prevent blockage.

[0038] Furthermore, transparent rubber hoses are installed on the faucets of the 12 sampling ports (19) at the bottom layer and placed on the left outer wall of the saltwater chamber (6) to monitor the head change at different positions in real time.

[0039] In addition, for the specific operation method of using this two-dimensional groundwater test flume to simulate the migration of pollutants in heterogeneous coastal aquifers under the coupling of tidal action and groundwater extraction, the following steps can be referred to:

[0040] Step S1, simulate the heterogeneous aquifer medium according to the experimental requirements, and prepare sand samples of different particle sizes. Inject water to a height of 20 cm into the aquifer loading tank (8), put the dry sand samples into the water to soak, and fully saturate the sand. Repeat the operation, and help to compact the sand samples every time the depth increases until the height of the sand samples required for the experiment is reached;

[0041] Step S2, paste filters on the lower ends of the prepared pumping well (4) and the customized pollution tank (2) to isolate sand grains. According to the experimental requirements, place the pollution tank (2) for simulating the pollutant injection at a distance of d1 from the saltwater chamber and at a depth of h from the bottom of the loading tank (8); insert the pumping well (4) for simulating groundwater extraction into the sand samples as well, and place it at a distance of d2 from the saltwater chamber;

[0042] Step S3, connect the third peristaltic pump (3) and the pollution tank (2) with a rubber tube, and connect the fourth peristaltic pump (5) and the pumping well (4). Preset the injection rate v1 of the pollutants and the pumping rate v2 required for the experiment according to the experimental needs;

[0043] Step S4, fix the tidal device (1) on the upper part of the saltwater chamber (6), and preset the tidal amplitude and period conditions required for the experiment; connect the tidal device (1) and the saltwater constant head device (17), put the steel bar on the upper part of the saltwater constant head device (17) into the fixing ring of the tidal device (1), and use nuts to fix it above and below the fixing ring;

[0044] Step S5, close the drain valve (11), and turn on the first peristaltic pump (13) and the second peristaltic pump (16) to form a stable water cycle in both the seawater simulation device and the fresh water simulation device, and form a stable flow in the aquifer in the aquifer loading tank (8);

[0045] Step S6, adjust and fix the saltwater head height and the fresh water head height according to the experiment, and at the same time adjust the water volume in the saltwater tank (12) to keep the saltwater head stable;

[0046] Step S7, prepare seawater and pollutant solutions in two prepared containers respectively to simulate seawater intrusion and the migration of pollutants. Add a certain amount of NaCl and the corresponding tracer into each container so that when the prepared seawater solution replaces the fresh water in the saltwater tank (12) at the beginning of the experiment, the seawater concentration in the saltwater chamber (6) is 35 g / L; connect the pollution tank (2) and the container configured with pollutants through a rubber tube so that the pollutant concentration entering the pollution tank (2) from the container through the third peristaltic pump (3) is also 35 g / L;

[0047] Step S8: Check whether the fresh-salt water head is stable, and observe whether the water head state in the rubber tube on the left outer wall of the salt water chamber (6) is normal. If there are bubbles in the rubber tube, resulting in the inability to accurately display the water head height at the lowest sampling port (19) of the aquifer loading tank (8), adjust it until the water head state in the rubber tube on the left outer wall of the salt water chamber (6) is normal;

[0048] Step S9: Place the camera in the front to start video recording for the experiment. Pour the seawater with tracer into the salt water tank (12), so that the seawater enters the salt water chamber (6) from the salt water tank (12) to simulate seawater intrusion. Observe the seawater intrusion situation until a stable salt water wedge is formed. During the process, take samples through the rear sampling hole (18) at regular intervals, record the seawater conductivity, and simultaneously record the length, height of the salt water wedge and the water level data;

[0049] Step S10: After the salt water wedge is stable, turn on the third peristaltic pump (3) and the third peristaltic pump (5). While releasing pollutants, start pumping water, and at the same time turn on the tidal device (1) to simulate the migration of pollutants in the heterogeneous coastal aquifer under the condition of coupling tidal action and groundwater extraction;

[0050] Step S11: During the experiment, record the size of the salt water wedge, the infiltration area of the pollutants and the time nodes. Take samples at regular intervals to measure the conductivity of the salt water and the pollutants, record and plot the conductivity change graph. End this group of experiments when the pollutants are pumped out or come into contact with the salt water wedge, and turn off the video recording.

[0051] The experimental device and method are designed to simulate the influence of different tidal conditions on pollutant migration, the influence of different pumping rates of production wells on pollutant migration, and study the area and shape change law of pollutants passing through different media under the condition of seawater intrusion in the coastal zone through different experimental conditions. To sum up, the migration law of pollutants in the heterogeneous coastal aquifer under the condition of coupling tidal action and groundwater extraction can be comprehensively studied.

Claims

1. A device for simulating the migration of pollutants in a coastal heterogeneous aquifer under the conditions of tidal action coupled with groundwater extraction, characterized in that: The invention comprises an aquifer loading tank (8) which is used as a seepage chamber, and the tank body is placed on a bracket (14); a pollution tank (2) simulating a pollution source and a plastic pipe (4) simulating a pumping well are arranged in the aquifer loading tank (8); a salt water chamber (6) and a fresh water chamber (10) are separated on the left and right sides of the aquifer loading tank (8) by a first acrylic plate (7) with seepage holes and a second acrylic plate (9) with seepage holes; The salt water chamber (6) and the fresh water chamber (10) are provided with the same water head constant device (17); the salt water chamber (6) and the fresh water chamber (10) are respectively connected to the salt water tank (12) and the fresh water tank (15) below them; a tidal device (1) is provided on the salt water chamber (6) to simulate the tidal effect of seawater; The salt water chamber (6), the salt water tank (12), and the first peristaltic pump (13) are connected by a rubber tube to form a seawater simulation device; the fresh water chamber (10), the fresh water tank (15), and the second peristaltic pump (16) are connected by a rubber tube to form a fresh water simulation device.

2. The device for simulating the migration of pollutants in a coastal heterogeneous aquifer under the conditions of tidal action coupled with groundwater exploitation according to claim 1, characterized in that: The first acrylic plate (7) with seepage holes and the second acrylic plate (9) with seepage holes are both covered with filter screens.

3. The device for simulating the migration of pollutants in a coastal heterogeneous aquifer under the conditions of tidal action coupled with groundwater exploitation according to claim 1, characterized in that: Circular water-permeable holes are evenly arranged at the bottom of the pollution tank (2), and a filter screen is covered at the bottom to prevent sand samples from entering the pollution tank (2).

4. The device for simulating the migration of pollutants in a coastal heterogeneous aquifer under the conditions of tidal action coupled with groundwater exploitation according to claim 1, characterized in that: A total of 72 sampling ports (18) are arranged in 6 rows and 12 columns at the rear side of the aquifer loading tank (8) as monitoring holes for real-time extraction of solution concentrations at different positions. The sampling ports are provided with faucets for directly taking stable water samples, and filter screens are pasted inside the sampling ports to isolate sand particles.

5. The device for simulating the migration of pollutants in a coastal heterogeneous aquifer under the conditions of tidal action coupled with groundwater exploitation according to claim 4, characterized in that: Transparent rubber tubes are installed on the taps of the 12 sampling ports (19) at the bottom layer and placed on the left side wall outside the salt water chamber (6) to monitor the changes in water head at different positions in real time.

6. A specific and operational method for simulating the migration of pollutants in a coastal heterogeneous aquifer under conditions of tidal action coupled with groundwater extraction using the device as described in any one of claims 1 to 5, characterized in that: The method comprises the following steps: Step S1, simulating a heterogeneous aquifer medium according to the experimental requirements, preparing sand samples of different particle sizes, injecting water to a height of 20 cm into the aquifer loading tank (8), and soaking the dry sand sample in the water to fully saturate the sand, repeating the operation, and compacting the sand sample each time the depth is increased until the sand sample height required for the experiment is reached; Step S2, affix filter screens to the lower ends of the prepared pumping well (4) and the customized pollution tank (2) to isolate sand particles, and place the pollution tank (2) for simulating pollutant placement at a distance d1 from the salt water chamber and a depth h from the bottom of the loading tank (8); insert the pumping well (4) for simulating groundwater extraction into the sand sample and place it at a distance d2 from the salt water chamber; Step S3, using a rubber tube to connect the third peristaltic pump (3) and the pollution tank (2), and to connect the fourth peristaltic pump (5) and the pumping well (4), and preset the pollutant injection rate v1 and the pumping rate v2 required for the experiment according to the experimental needs; Step S4, fix the tidal device (1) to the upper part of the salt water chamber (6), and preset the tidal amplitude and period conditions required for the experiment; connect the tidal device (1) and the salt water constant head device (17), insert the upper steel bar of the salt water constant head device (17) into the fixing ring of the tidal device (1), and use nuts on the upper and lower parts of the fixing ring to fix it; Step S5, closing the drain valve (11), and starting the first peristaltic pump (13) and the second peristaltic pump (16), so that a stable water circulation is formed in both the seawater simulation device and the freshwater simulation device, so that a stable flow is formed in the aquifer in the aquifer loading tank (8); Step S6, adjusting the salt water head height and the fresh water head height according to the experiment and fixing them, and adjusting the water volume in the salt water tank (12) to keep the salt water head stable; Step S7, preparing seawater and pollutant solution in two prepared containers respectively to simulate seawater intrusion and migration of pollutants, adding a certain amount of NaCl and corresponding tracers in each container respectively, so that when the fresh water in the salt water tank (12) is replaced by the prepared seawater solution at the beginning of the experiment, the seawater concentration in the salt water chamber (6) is 35g / L; connecting the pollution tank (2) and the container configured with pollutants through a rubber tube, so that the pollutant concentration entering the pollution tank (2) from the container through the third peristaltic pump (3) is also 35g / L; Step S8, check whether the salt and fresh water head is stable, and observe whether the water head state in the rubber tube on the left side wall outside the salt water chamber (6) is normal. If there are bubbles in the rubber tube, which makes it impossible to accurately display the water head height at the bottom sampling port (19) of the aquifer loading tank (8), adjust it so that the water head state in the rubber tube on the left side wall outside the salt water chamber (6) is normal; Step S9, placing the camera in front to record and start the experiment, putting seawater with tracers into the saltwater tank (12), so that the seawater enters the saltwater chamber (6) from the saltwater tank (12) to simulate seawater intrusion, observing the seawater intrusion until a stable saltwater wedge is formed, sampling through the rear sampling hole (18) at regular intervals, recording the seawater conductivity, and recording the length, height and water level data of the saltwater wedge; Step S10, after the saltwater wedge is stabilized, the third peristaltic pump (3) and the third peristaltic pump (5) are turned on to release the pollutants and start pumping water at the same time, and the tidal device (1) is turned on at the same time to simulate the migration of pollutants in the coastal heterogeneous aquifer under the conditions of tidal action coupled with groundwater exploitation; Step S11, during the experiment, record the size of the salt water wedge and the infiltration area of ​​the pollutants and record the time nodes, take samples at regular intervals to measure the conductivity of the salt water and the pollutants, record and draw a conductivity change graph, and end the experiment when the pollutants are extracted or contact the salt water wedge, and turn off the video.

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