Polluted site heavy metal vertical migration monitoring device and method

Abstract

The invention provides a polluted site heavy metal vertical migration monitoring device and method. The monitoring device is provided with a barrel-shaped frame and bottom supporting legs, an adsorption resin layer is arranged on the barrel-shaped frame, an isolation medium layer and a filtering medium layer are arranged on the upper portion and the lower portion of the adsorption resin layer respectively, and a sensor is arranged on the filtering medium layer. The monitoring structure is arranged in a soil layer needing to be monitored, soil particles are intercepted by the filter medium layer, vertically migrated heavy metal ions are adsorbed by the adsorption resin layer, the ion content difference change of the upper and lower layer sensors is monitored, and the saturation condition of the resin layer is judged. And when the monitoring time is up, controlling the bottom of the resin layer to be closed, pumping an eluent to elute heavy metal ions and regenerate the resin, collecting the eluent, and analyzing and calculating the vertical migration amount of the heavy metal in the soil layer in a certain period. Heavy metal ions passing through the section in the water infiltration process are collected by adopting a resin in-situ adsorption method, so that monitoring is realized, and the method has the advantages of simple layout, reutilization and the like.

Description

Technical Field

[0001] The invention relates to the technical field of heavy metal vertical migration monitoring, and in particular to a device and method for monitoring heavy metal vertical migration in a contaminated site. Background Art

[0002] There are many ways for heavy metals to migrate in soil, including water conditions, soil properties, plants, microbial action, etc. For contaminated sites, the migration of heavy metal ions mostly occurs during infiltration or precipitation. When water penetrates downward, it dissolves the heavy metal ions in the soil layer. Once the heavy metals are desorbed into the soil solution, they will migrate through the movement of water. This migration can be vertical or horizontal. Water causes dissolved metal ions to migrate in the soil through capillary action and gravity.

[0003] The migration of heavy metals in contaminated sites is affected by soil type, leachate properties, and the chemical properties of the ions themselves. It is hidden and specific, and it is difficult to find universal migration rules from existing cases. At present, the monitoring method for the vertical migration of heavy metals in soil is mainly the method of stratified sampling + post-collection analysis. According to the site investigation, researchers collect a soil sample at a certain depth from the surface to the deep layer, and obtain the content information of the target ions in the sample through laboratory analysis or on-site rapid detection methods, and analyze the migration and distribution of heavy metals through the difference in heavy metal content at different depths. This method can reveal the migration of heavy metal ions to the greatest extent, and has the advantages of strong representativeness, high integrity, and wide adaptability. However, this method cannot accurately measure the amount of heavy metal migration on a horizontal section of a certain soil layer. At the same time, this sampling method is not long-term, and it is impossible to determine the content changes and accumulation of heavy metal ions in the collected samples at different time scales. For the migration of heavy metal ions on soil sections and long-term sustainable in-situ monitoring, there is currently no technical solution specifically for soil environmental researchers to monitor such data.

[0004] Resin adsorption has important applications in heavy metal treatment, mainly focusing on the rapid collection of target analytes in large-volume water environment samples, sample pretreatment, separation and purification, etc. There are related cases in electroplating industrial wastewater treatment, surface water monitoring, and food processing wastewater treatment, and it has a good enrichment effect on heavy metals such as nickel, cadmium, chromium, copper, and zinc. In the field of soil heavy metal detection, the resin adsorption method is mostly used for the separation and purification of specific ions in soil leachate in the laboratory. There are no relevant technical solutions and application cases for field monitoring. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned prior art, the present invention provides a monitoring device and method for the vertical migration of heavy metals in contaminated sites; the monitoring device can be deployed in a soil layer to monitor the vertical migration of heavy metal ions in real time, utilize an isolation medium layer to support and intercept large particles, utilize a filter medium layer to intercept soil particles, utilize an adsorption resin layer to adsorb dissolved heavy metal ions, and after the adsorption resin layer is fully adsorbed, collect the heavy metal ions in the resin by elution, and calculate the vertical migration amount of the heavy metals; the entire device is simple to deploy, can realize in-situ adsorption and desorption, and can be reused.

[0006] In order to achieve the above technical objectives, the present invention provides a heavy metal vertical migration monitoring device for a contaminated site, the monitoring device comprising an ion monitoring sensor system and a heavy metal vertical migration collecting device buried in a soil layer to be monitored, the heavy metal vertical migration collecting device comprising a cylindrical frame, a bottom support leg and a heavy metal migration collecting structure layer arranged in the cylindrical frame, the top and bottom surfaces of the cylindrical frame are both mesh structures, the heavy metal migration collecting structure layer comprises, from top to bottom, an upper isolation medium layer, an upper filter medium layer, a chelating resin layer, a cation exchange resin layer, a lower isolation medium layer, and a lower filter medium layer; the chelating resin layer and the cation exchange resin layer are respectively placed in an upper heavy metal elution frame and a lower heavy metal elution frame, the upper heavy metal elution frame and the lower heavy metal elution frame are both upper open-end cylindrical frames matching the cylindrical frame, and filter holes are arranged on the bottom of the frame, the upper heavy metal elution frame is provided with a heavy metal eluent injection port, the bottom surface of the upper heavy metal elution frame is provided with an eluent through hole, and the lower heavy metal elution frame is provided with a heavy metal eluent recovery port;

[0007] A movable baffle is provided at the bottom of the upper and lower metal elution frames, respectively, and the movable baffle is provided with a hollow structure matching the filter holes on the bottom surface of the metal elution frame; during the heavy metal migration and collection process, the hollow structures of the movable baffles in the upper heavy metal elution frame and the lower heavy metal elution frame correspond to the filter holes, and at this time, the bottom surfaces of the upper heavy metal elution frame and the lower heavy metal elution frame are both open; during the heavy metal elution process, the movable baffles of the upper heavy metal elution frame and the lower heavy metal elution frame are moved to a state where the hollow structure and the filter holes are completely staggered, and at this time, the filter holes on the bottom surfaces of the upper heavy metal elution frame and the lower heavy metal elution frame are both closed, and the upper heavy metal elution frame is connected to the lower heavy metal elution frame through the eluent through hole;

[0008] The ion monitoring sensor system includes a heavy metal ion monitoring device arranged on the ground and heavy metal ion sensors arranged in the middle of the upper filter medium layer and the lower filter medium layer. The heavy metal ion sensors are communicatively connected with the heavy metal ion monitoring device.

[0009] The preferred technical solution of the present invention is as follows: the frames of the upper heavy metal elution frame and the lower heavy metal elution frame are divided into a plurality of elution chambers connected in sequence by a plurality of vertically arranged partitions; the filter holes are evenly distributed on the bottom surface of each elution chamber in the shape of strips; the heavy metal eluent injection port is connected to the first elution chamber on one side of the upper heavy metal elution frame; the eluent through hole is opened on the bottom surface of the last elution chamber on the other side of the upper heavy metal elution frame and is connected to the last elution chamber on the same side of the lower heavy metal elution frame; the heavy metal eluent recovery port is connected to the first elution chamber on the other side of the lower heavy metal elution frame.

[0010] A preferred technical solution of the present invention is that the ion sensor is an ion selective electrode probe that selectively responds to calcium or magnesium ions, converts ion concentration information into electrical signals, transmits them through lines to a data processor of an ion monitoring device, and displays them on a display instrument of the ion monitoring device.

[0011] A better technical solution of the present invention: the monitoring device also includes a heavy metal elution system, which includes an eluent container, a cleaning liquid container, an eluent collecting container and an elution control pipeline. One end of the elution control pipeline is connected to the eluent container and the cleaning liquid container respectively through branch pipes, and control valves are respectively provided on the two branch pipes. The other end of the elution control pipeline is connected to the heavy metal eluent injection port of the upper heavy metal elution frame, and the eluent collecting container is connected to the heavy metal eluent recovery port of the lower heavy metal elution frame through a recovery pipe.

[0012] The better technical solution of the present invention is as follows: four bottom legs are provided and evenly distributed at the bottom of the cylindrical frame, each bottom leg is 24 to 35 cm long, and a conical tip is provided at the bottom thereof, which is welded to the bottom of the cylindrical frame; the cylindrical frame is made of 2 to 3 mm thick carbon steel plate to form a cylindrical structure with upper and lower open openings, and its cylindrical wall is a double-layer hollow structure with a hollow layer width of 1.8 to 2.2 cm for laying pipelines and lines, and a groove for placing a heavy metal migration collection structural layer is provided on the inner wall of the cylindrical frame.

[0013] The preferred technical solution of the present invention is as follows: the upper isolation medium layer and the upper filter medium layer are placed in the upper filter mesh frame, the lower isolation medium layer and the lower filter medium layer are placed in the lower filter mesh frame, the upper filter mesh frame and the lower filter mesh frame both adopt an upper open cylindrical structure that matches the cylindrical frame, and their bottom surfaces adopt a grid-shaped filter plate; the upper filter mesh frame, the upper heavy metal elution frame, the lower heavy metal elution frame and the lower filter mesh frame are sequentially embedded in the cylindrical frame from top to bottom.

[0014] The preferred technical solution of the present invention is as follows: the upper isolation medium layer and the lower isolation medium layer are both filled with medium-coarse sand with a particle size of 0.5-2 mm, and the filling layer thickness is 8-12 cm; the upper filter medium layer and the lower filter medium layer are both filled with gravel with a particle size of 5-10 mm, and the filling layer thickness is 8-12 cm; the isolation medium layer and the filter medium layer are both wrapped with a non-woven geotextile with a porosity of 60%-80% and a thickness of 0.5-1 mm; the chelate resin layer uses a chelate resin containing iminodiacetic acid functional groups with a particle size of 0.5-2 mm, and the filling thickness is 3-5 cm; the cation exchange resin layer uses a cation exchange resin with a particle size of 0.5-2 mm, and the filling thickness is 3-5 cm; and a non-woven geotextile with a porosity of 60%-80% is laid at the bottom of the chelate resin layer and the cation exchange resin layer.

[0015] The preferred technical solution of the present invention is as follows: the movable baffle is located below the bottom plates of the upper heavy metal elution frame and the lower heavy metal elution frame, and a support frame for installing the movable baffle is provided at the bottom of the upper heavy metal elution frame and the lower heavy metal elution frame, and the movable baffle comprises a plurality of baffles whose width is greater than the diameter of the filter hole, the arrangement direction of the plurality of baffles is consistent with the arrangement direction of the filter holes, and the length of each baffle is greater than the arrangement length of a filter hole, and the plurality of baffles are connected as a whole by a connecting rod, and an electric push rod is provided at one end of the connecting rod, and the electric push rod is fixedly installed on the support frame, and the other end of the connecting rod is slidably connected to the other side of the support frame, and a slide groove is correspondingly provided on the support frame, and the other end of the connecting rod is embedded in the slide groove, and a limit block is provided at the end; under the action of the electric push rod, the plurality of baffles are driven to move horizontally at the same time to completely block or open the filter holes.

[0016] The present invention also provides a method for monitoring the vertical migration of heavy metals in a contaminated site. The method uses the above-mentioned device for monitoring the vertical migration of heavy metals in a contaminated site to monitor the vertical migration of heavy metals in contaminated soil and calculate the vertical migration amount of heavy metals in the monitoring area. The specific steps of the method are as follows:

[0017] S1. The heavy metal vertical migration collection device is buried in the soil layer at the target depth, the heavy metal ion monitoring device is placed on the ground, and the heavy metal ion sensor installed in the heavy metal vertical migration collection device is connected to the heavy metal ion monitoring device on the ground through a signal line, and the heavy metal collection amount of the heavy metal vertical migration collection device buried in the soil layer at the target depth is monitored by the heavy metal ion monitoring device;

[0018] S2. When the ion concentration ratio monitored by the heavy metal ion sensor is lower than the product of the recovery rate of the adsorption resin for the target metal ion and the saturation coefficient, the heavy metal vertical migration collection device is taken out to prepare for heavy metal elution;

[0019] S3. Control the movable plate at the bottom of the upper heavy metal elution frame and the lower heavy metal elution frame to move horizontally, and completely close the filter holes at the bottom of the upper heavy metal elution frame and the lower heavy metal elution frame; use hydrochloric acid solution as eluent, pump the eluent through the heavy metal eluent injection port, use ion exchange method to elute the heavy metal ions in the chelating resin layer and the cation exchange resin layer, and collect the eluent containing heavy metal ions through the heavy metal eluent recovery port; after the elution is completed, pump the cleaning agent through the heavy metal eluent injection port, and reuse after cleaning; the concentration of the hydrochloric acid solution is 1.5-2mol / L, the amount is 2-3BV, and the flow rate is 2-4BV / H; the cleaning agent is pure water, the amount of the pure water is 3-5BV, and the flow rate is 3-4BV / H;

[0020] S4. For the eluate containing heavy metal ions collected in step S3, the recovery rate of the chelating resin layer and the cation exchange resin layer for specific target heavy metal ions is determined by the spike recovery method; the eluate containing heavy metal ions is filtered and diluted to obtain a sample to be tested, and an atomic absorption spectrophotometer or a fluorescence photometer is used to test the sample to be tested to determine the mass concentration of the target heavy metal element in the eluate; and then the average vertical migration amount of heavy metal ions per unit area is calculated according to the following formula:

[0021]

[0022] In the above formula: R is the recovery rate of the adsorption resin for the target heavy metal element, %;

[0023] M is the vertical migration amount of heavy metal ions per unit area during the monitoring period, mg / m 2 ·d;

[0024] c is the mass concentration of the target heavy metal element in the sample to be tested, mg / L;

[0025] f is the dilution factor of the eluent containing heavy metal ions;

[0026] V is the total volume of the eluent containing heavy metal ions, L;

[0027] S is the horizontal area where the monitoring resin is laid, m 2 ;

[0028] D is the number of monitoring days, d.

[0029] 10. A method for monitoring the vertical migration of heavy metals in contaminated sites according to claim 9, characterized in that: the recovery rate and saturation coefficient of the adsorption resin for the target metal ion in step S2 range from 0.6 to 0.8, and the specific formula is as follows:

[0030]

[0031] Where: c1 is the monitoring concentration of the target element in the upper isolation medium layer, mg / L;

[0032] c2 is the monitoring concentration of the target element in the lower isolation medium layer, mg / L;

[0033] α is the saturation coefficient of the adsorption resin for the target element;

[0034] R is the recovery rate of the target element by the adsorption resin, %;

[0035] In the step S4, the recovery R of the chelating resin layer and the cation exchange resin layer for specific target heavy metal ions is calculated according to the following formula:

[0036]

[0037] Where:

[0038] c3 is the spike concentration of target heavy metal ions before adsorption, mg / L;

[0039] c4 is the residual concentration of the target heavy metal ion after adsorption, mg / L.

[0040] The present invention is mainly aimed at some landfill or backfill contaminated sites, where water penetrates downward due to factors such as precipitation, irrigation, and infiltration, carrying dissolved heavy metal ions into the soil layer. The monitoring device can be deployed in the soil layer to be monitored, with an isolation medium layer supporting the structure, a filter medium layer intercepting soil particles, and an adsorption resin layer adsorbing vertically migrating heavy metal ions. The saturation of the resin layer is judged by referring to the difference in ion content of the upper and lower monitoring sensors. When the monitoring time is reached, the resin layer is closed by the control system, a specific solution is pumped in for elution of heavy metal ions and regeneration of the resin, the eluent is collected, and the monitoring of the vertical migration of heavy metals in the soil layer within a certain period is completed through laboratory analysis; during laboratory analysis, an appropriate amount of eluent (3-5mL) is taken from the collection bottle and filtered with a 0.45μm water system microporous filter membrane; for the filtered eluent, according to the requirements of the detection equipment and the concentration range of the standard working solution, it is appropriately diluted, and the dilution multiple and the total volume of the eluent in the collection bottle are recorded; before the machine test, the masking reagent required by the test method should be added to the sample, preferably, the masking reagent is 1% to 1.5% lanthanum nitrate. After the elution is completed, the cleaning solution is pumped in, and after the cleaning is completed, the resin layer is opened for the next monitoring.

[0041] The chelating resin in the present invention mainly absorbs Cu through the iminodiacetic acid chelating group. 2+ 、Ni 2+ 、Zn 2+ The cation exchange resin mainly adsorbs Pb 2+ 、Cd 2+ , Hg2+ Metal ions and some metal ions omitted from the upper layer.

[0042] Beneficial effects of the present invention:

[0043] (1) The monitoring device of the present invention can be buried in the soil layer of a contaminated site, using an isolation medium layer to intercept large particles, a filter medium layer to intercept soil particles, and an adsorption resin layer to adsorb dissolved heavy metal ions, thereby achieving in-situ fixation of heavy metal ions on the monitoring section and being able to collect the total amount of vertical migration of heavy metal ions within a fixed area.

[0044] (2) The present invention monitors the difference in ion concentration before and after resin adsorption by means of an ion concentration monitoring sensor arranged in the filter medium layer, thereby determining the adsorption saturation time of the resin layer and providing an indication for the control intervention time of the elution system.

[0045] (3) The present invention provides an in-situ chromatography scheme on the horizontal structure of the adsorption resin layer, which uses partitions and closed structures to define the elution path of the desorption solution and limit the concentration, dosage, and flow rate, thereby ensuring that the eluent fully desorbs the heavy metal ions adsorbed by the filled resin layer and that both layers of adsorption resin filled in the frame can be fully eluted.

[0046] (4) The present invention provides a pure water elution resin solution, which can remove residual elution solvent and impurities after elution and collection. The resin layer can be reused after regeneration and cleaning for continued monitoring.

[0047] (5) The present invention uses resin to adsorb dissolved heavy metal ions in hydrodynamic migration, which has the effect of purifying and concentrating the target analyte in the monitoring section. The soil matrix component in the eluent is relatively low, which avoids the influence of interfering components such as soil organic matter and minerals on the detector during traditional digestion methods, reduces the matrix effect, and can improve the accuracy of detection.

[0048] The present invention uses resin to in-situ adsorb and collect heavy metal ions passing through the cross section during water infiltration to achieve monitoring, and has the advantages of simple deployment, repeated use, reduced matrix effect, and long-term monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the overall structure of the monitoring device of the present invention;

[0050] Figure 2 This is a schematic diagram of the heavy metal migration and collection structure layer in the present invention;

[0051] Figure 3 It is a schematic diagram of the assembly of four functional frameworks in the present invention;

[0052] Figure 4It is a schematic plan view of the partition layout of the upper heavy metal elution frame of the present invention;

[0053] Figure 5 It is a longitudinal cross-sectional view of the baffle of the upper heavy metal elution frame of the present invention before it moves;

[0054] Figure 6 It is a schematic plan view of the baffle of the upper heavy metal elution frame of the present invention before it moves;

[0055] Figure 7 It is a longitudinal cross-sectional view of the upper heavy metal elution frame after the baffle plate of the present invention is moved;

[0056] Figure 8 It is a schematic plan view of the upper heavy metal elution frame after the baffle plate is moved in the present invention;

[0057] Fig. 9 It is a schematic plan view of the partition layout of the middle and lower heavy metal elution frame of the present invention;

[0058] Fig.10 It is a longitudinal cross-sectional view of the baffle of the lower heavy metal elution frame of the present invention before it moves;

[0059] Fig.11 It is a schematic plan view of the lower heavy metal elution frame after the baffle plate of the present invention is moved.

[0060] In the figure: 1—upper isolation medium layer, 2—upper filter medium layer, 3—chelate resin layer, 4—cation exchange resin, 5—lower isolation medium layer, 6—lower filter medium layer, 7—cylindrical frame, 8—movable baffle, 800—support frame, 801—connecting rod, 802—electric push rod, 803—chute, 9—bottom leg, 10—filter hole, 11—upper heavy metal elution frame, 12—lower heavy metal elution frame, 13—heavy metal The components are as follows: 1—eluent injection port, 14—eluent through hole, 15—heavy metal eluent recovery port, 16—heavy metal ion monitoring device, 17—heavy metal ion sensor, 18—partition plate, 19—elution chamber, 20—eluent container, 21—cleaning liquid container, 22—eluent collection container, 23—elution control pipeline, 24—control valve, 25—recovery pipe, 26—signal line, 27—upper filter rack, 28—lower filter rack. DETAILED DESCRIPTION

[0061] The present invention is further described below in conjunction with specific embodiments, wherein the accompanying drawings are only used for illustrative descriptions and represent only schematic diagrams rather than actual drawings, and should not be understood as limiting the present invention. In order to better illustrate the specific embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the accompanying drawings may be omitted. Based on the specific embodiments of the present invention, all other specific embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0062] In the description of the present invention, it should be noted that the terms "front", "rear", "upper", "lower" and the like indicate directions or positional relationships based on directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0063] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0064] The embodiment provides a heavy metal vertical migration monitoring device for contaminated sites, such as Figure 1 As shown, the monitoring device includes a heavy metal elution system, an ion monitoring sensor system and a heavy metal vertical migration collection device buried in the soil layer to be monitored. Figure 1 and Figure 2As shown, the heavy metal vertical migration collection device includes a cylindrical frame 7, a bottom leg 9 and a heavy metal migration collection structure layer arranged in the cylindrical frame 7. The bottom leg 9 is used to insert into the soil layer to fix the entire frame support structure. The bottom leg 10 is provided with four legs, which are evenly distributed at the bottom of the cylindrical frame 7. Each bottom leg 10 is made of 2mm thick hollow carbon steel material, with a length of 20-30cm and a diameter of 2cm. A cone structure with a height of 4cm is connected at the bottom of the cylindrical structure. The connection method is metal welding; the bottom leg 10 is metal welded with the cylindrical frame 7, or directly adopts an integrated structure. The cylindrical frame 7 is made of 2mm thick carbon steel plate to form a cylindrical structure with upper and lower openings. Its cylinder wall is a double-layer hollow structure, and the width of the hollow layer is 2cm, which is used to lay pipelines and lines. The inner wall of the cylindrical frame 7 is equipped with a groove for placing the heavy metal migration collection structure layer.

[0065] The heavy metal vertical migration monitoring device for contaminated sites in the embodiment is as follows: Figures 1 to 3 As shown, the heavy metal migration and collection structure layer includes, from top to bottom, an upper isolation medium layer 1, an upper filter medium layer 2, a chelating resin layer 3, a cation exchange resin layer 4, a lower isolation medium layer 5, and a lower filter medium layer 6; the upper isolation medium layer 1 and the upper filter medium layer 2 are placed in an upper filter mesh frame 17, the lower isolation medium layer 5 and the lower filter medium layer 6 are placed in a lower filter mesh frame 18, the chelating resin layer 3 and the cation exchange resin layer 4 are placed in an upper heavy metal elution frame 11 and a lower heavy metal elution frame 12, respectively.

[0066] The upper filter mesh frame 17 and the lower filter mesh frame 18 both adopt an upper open cylindrical structure that matches the cylindrical frame 7, and their bottom surfaces adopt a grid-shaped filter plate; the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12 are both upper open cylindrical frames that match the cylindrical frame 7, and filter holes 10 are arranged on the bottom surfaces of the frames, the upper heavy metal elution frame 11 is provided with a heavy metal eluent injection port 13, the bottom surface of the upper heavy metal elution frame 11 is provided with an eluent through hole 14, and the lower heavy metal elution frame 12 is provided with a heavy metal eluent recovery port 15; the upper filter mesh frame 17, the upper heavy metal elution frame 11, the lower heavy metal elution frame 12 and the lower filter mesh frame 18 are sequentially embedded in the groove of the inner wall of the cylindrical frame 7 from top to bottom. The upper isolation medium layer 1 and the lower isolation medium layer 5 are both filled with medium-coarse sand with a particle size of 0.5-2mm, and the filling layer thickness is 10cm; the upper filter medium layer 2 and the lower filter medium layer 6 are both filled with gravel with a particle size of 5-10mm, and the filling layer thickness is 10cm; the isolation medium layer and the filter medium layer are both wrapped with a non-woven geotextile with a porosity of 60%-80% and a thickness of 0.5-1mm; the chelating resin layer 3 is a chelating resin containing iminodiacetic acid functional groups with a particle size of 0.5-2mm, and the filling thickness is 3-5cm; the cation exchange resin layer 4 is a cation exchange resin with a particle size of 0.5-2mm, and the filling thickness is 3-5cm; and a non-woven geotextile with a porosity of 60%-80% is laid at the bottom of the chelating resin layer 3 and the cation exchange resin layer 4. The filter medium layer and the isolation medium layer are wrapped with non-woven geotextiles to fix the layered filling structure and ensure the water permeability of the filling layer. Non-woven geotextiles are laid at the bottom of the resin material layer to prevent filling collapse. The chelating resin mainly absorbs Cu through the iminodiacetic acid chelating group 2+ 、Ni 2+ 、Zn 2+ The cation exchange resin mainly adsorbs Pb 2+ 、Cd 2+ , Hg 2+ Metal ions and some metal ions omitted from the upper layer.

[0067] The heavy metal vertical migration monitoring device for contaminated sites in the embodiment is as follows: Figure 4 , Figure 5 , Figure 7 , Fig. 9 and Fig.10As shown, the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12 are divided into a plurality of elution chambers 19 connected in sequence by a plurality of vertically arranged partitions 18 in the frame body, the filter holes are evenly distributed on the bottom surface of each elution chamber 19 in the shape of strips, the heavy metal eluent injection port 13 is connected to the first elution chamber on one side of the upper heavy metal elution frame 11, the eluent through hole 14 is opened on the bottom surface of the last elution chamber on the other side of the upper heavy metal elution frame 11, and is connected to the last elution chamber on the same side of the lower heavy metal elution frame 12, the heavy metal eluent recovery port 15 is connected to the first elution chamber on the other side of the lower heavy metal elution frame 12; the metal elution frame can be partitioned into a fixed elution route by the partition 18. As shown Figures 5 to 8 , Fig.10 and Fig.11 As shown, movable baffles 8 are respectively provided at the bottom of the upper and lower metal elution frames, and the movable baffles 8 are provided with a hollow structure matching the filter holes on the bottom surface of the metal elution frame; the movable baffles 8 are located below the bottom plates of the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12. A support frame 800 for installing a movable baffle 8 is provided at the bottom of the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12. The movable baffle 8 includes a plurality of baffles whose width is greater than the diameter of the filter hole 10. The arrangement direction of the plurality of baffles 8 is consistent with the arrangement direction of the filter hole 10, and the length of each baffle 8 is greater than the arrangement length of a filter hole 10. The plurality of baffles are connected as a whole by a connecting rod 801. In order to ensure the stability of the connection, multiple connecting rods can be used. In the embodiment, three connecting rods are used, and the ends of the three connecting rods are connected as a whole by a connecting plate; an electric push rod 802 is provided at one end of the connecting rod 801, and the electric push rod 802 is fixedly mounted on the support frame 800. The other end of the connecting rod 801 is slidably connected to the other side of the support frame 800. A slide groove 803 is correspondingly provided on the support frame 800, and the other end of the connecting rod 801 is embedded in the slide groove 803, and a limit block is provided at the end. Under the action of the electric push rod 802, multiple baffles are driven to move horizontally at the same time to completely block or open the filter hole 10. The partition 18 is made of acid-resistant polyethylene, with a height of 5 cm and a partition interval of 4 cm. Non-woven geotextiles are laid between the partitions and filled with resin materials; the movable baffle 8 is made of acid-resistant polyethylene and has a width of 2.5 cm.

[0068] During the heavy metal migration and collection process, the hollow structures of the movable baffles 8 in the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12 correspond to the filter holes 13, such as Figure 5 , Figure 6 and Fig.10 As shown, at this time, each baffle moves to the position below the partition 18, and the filter holes 10 on the bottom of the elution chamber 19 are all opened, and the ion penetration is carried out normally. Figure 7 , Figure 8 and Fig.11 As shown, the movable baffles 8 of the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12 are moved to a state where the hollow structure and the filter hole 10 are completely staggered. At this time, each baffle moves to the position where the filter hole 10 is opened in the elution chamber 19, and all the filter holes are blocked, so that the filter holes on the bottom surfaces of the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12 can be closed, and the upper heavy metal elution frame 11 is connected to the lower heavy metal elution frame 12 through the eluent through hole 14; the heavy metal ions can be eluted, and during the elution process, the eluent is washed. The eluent is injected into the first elution cavity 19 of the upper heavy metal elution frame 11 through the heavy metal eluent injection port 13, and then the eluent flows through each elution cavity 19 of the upper heavy metal elution frame 11 in sequence according to a specific elution route, and then enters the tail elution cavity on the same side of the lower heavy metal elution frame 12 through the eluent through hole 14, and then flows through each elution cavity 19 of the lower heavy metal elution frame 12 in sequence according to a specific elution route, and finally flows out through the heavy metal eluent recovery port 15 on the lower heavy metal elution frame 12 for collection.

[0069] The heavy metal vertical migration monitoring device in the contaminated site in the embodiment is as follows: Figure 1 to Figure 2 As shown, the ion monitoring sensor system includes a heavy metal ion monitoring device 16 arranged on the ground and a heavy metal ion sensor 17 arranged in the middle of the upper filter medium layer 2 and the lower filter medium layer 6. In order to facilitate the installation of the heavy metal ion sensor 17, a mounting hole is opened in the middle of the upper filter rack 17 and the lower filter rack 18 for the installation of the heavy metal ion sensor 17. The heavy metal ion sensor 17 is communicatively connected with the heavy metal ion monitoring device 16. The ion sensor 12 is an ion selective electrode probe that selectively responds to calcium or magnesium ions, which converts ion concentration information into an electrical signal and transmits it to the data processor of the ion monitoring device 11 through a line, and displays it through the display instrument of the ion monitoring device 11.

[0070] When the concentration ratio of the metal ion sensor 17 is lower than the product of the recovery rate of the adsorbent resin for the target metal ion and the saturation coefficient, elution is performed. The saturation coefficient ranges from 0.6 to 0.8, and the specific formula is as follows:

[0071]

[0072] Where: c1 is the monitoring concentration of the target element in the upper isolation medium layer, mg / L;

[0073] c2 is the monitoring concentration of the target element in the lower isolation medium layer, mg / L;

[0074] α is the saturation coefficient of the adsorption resin for the target element;

[0075] R is the recovery rate of the target element by the adsorption resin, %.

[0076] The heavy metal vertical migration monitoring device in the contaminated site in the embodiment is as follows: Figure 1 As shown, the monitoring device also includes a heavy metal elution system, which includes an eluent container 20, a cleaning liquid container 21, an eluent collection container 22 and an elution control pipeline 23. One end of the elution control pipeline 23 is connected to the eluent container 20 and the cleaning liquid container 21 through a branch pipe, and a control valve 24 is provided on the two branch pipes. The other end of the elution control pipeline 23 is connected to the heavy metal eluent injection port 13 of the upper heavy metal elution frame 11, and the eluent collection container 22 is connected to the heavy metal eluent recovery port 15 of the lower heavy metal elution frame 12 through a recovery pipe 25. The heavy metal elution system is arranged on the ground, and the monitoring device can be taken out for elution during the elution process, or it can be eluted directly in situ.

[0077] When the present invention is specifically applied, the main monitoring device is arranged in the soil layer of the target depth, and the display and output part of the ion concentration sensor system is arranged on the ground, and is connected to the sensitive electrode element of the filter medium layer through the line. During the normal monitoring process, the heavy metal elution system does not intervene, the filter holes 10 at the bottom of the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12 are normally opened, and the heavy metals in the soil layer migrate through the device with the hydrodynamic force to achieve in-situ adsorption. The concentration difference between the two heavy metal ion sensors 7 is used as an indication to judge the saturation of the resin layer and determine the heavy metal ion collection time. During the elution and collection process, the heavy metal elution system intervenes, and the baffle 8 is controlled to move by the electric push rod to close the filter holes at the bottom of the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12. The control valve on the pipeline of the eluent container 20 is first opened, and a 2mol / L hydrochloric acid solution is pumped from the eluent container 20 into the heavy metal eluent injection port 13, with a flow rate of 2-4BV / H and a dosage of 2-3BV. The solution elutes the heavy metal ions adsorbed in the filling material of the chelating resin layer along the elution path separated by the partition 18, and flows into the cation exchange resin layer from the eluent through hole 14, and elutes the heavy metal ions adsorbed in the cation exchange resin layer along the partition path. Finally, the eluent flows out through the heavy metal eluent recovery port 15 and is collected in the eluent collection container 22.

[0078] After finishing the heavy metal ion wash-out work, close the control valve on the eluent container 20 pipelines, open the control valve on the cleaning fluid container 21 connecting pipelines, pure water is pumped into the heavy metal eluent injection port 13 by the cleaning fluid container 21, and flow velocity is 3-4BV / H, and consumption is 3-5BV.Solution cleans the resin layer and the cation exchange resin layer packing material along the partition path, finally flows out through the heavy metal eluent recovery port 15, and now, solution can be discarded.After finishing the cleaning work, control baffle plate 8 moves the filter hole 10 of upper strata heavy metal wash-out frame 11 and lower floor's heavy metal wash-out frame 12 bottoms to be normally opened, and guarantee that two control valves are in closed state, can start the next stage monitoring work again.

[0079] After the eluent is diluted and filtered according to the injection concentration required by the specification, it is configured into a working solution using the corresponding method to analyze the target metal ions. During laboratory analysis, take an appropriate amount of eluent (3-5mL) from the collection bottle and filter it with a 0.45μm water-based microporous filter membrane; for the filtered eluent, dilute it appropriately according to the requirements of the detection equipment and the concentration range of the standard working solution, and record the dilution multiple and the total volume of the eluent in the collection bottle. Before the machine test, the masking reagent required by the test method should be added to the sample. Preferably, the masking reagent is 1% to 1.5% lanthanum nitrate; the analysis of heavy metal ions in the eluent adopts atomic absorption spectrophotometry or atomic fluorescence to obtain the mass concentration of the target heavy metal element; the spike recovery method is used to determine the recovery rate of the adsorption resin for specific target heavy metal ions:

[0080] A chromatographic column with a specification of 10 mm x 500 mm is filled with an adsorption resin, an appropriate amount of the adsorption resin is weighed, and the column is soaked in pure water overnight, and the column is filled in a wet column packing manner, the height of the resin layer is 300-350 mm, the upper layer of the resin layer is a chelating resin, the filling height is 150-175 mm, and the lower layer is a cation exchange resin, and the filling height is 150-175 mm.

[0081] Take the leachate (200-300mL) from the contaminated site to be monitored as a representative solution, add the target heavy metal ion standard solution with known concentration as the internal standard, the heavy metal ion concentration range of the leachate is 10-100mg / L, after loading, the solution flow rate is controlled at 5-10BV / H, collect the adsorbed solution. Atomic absorption spectrophotometry or atomic fluorescence spectrometry is used to analyze the heavy metal ion content in the solution before and after adsorption, and the recovery rate R of the adsorption resin layer for specific target heavy metal ions is:

[0082]

[0083] Where:

[0084] c3 is the spike concentration of target heavy metal ions before adsorption, mg / L;

[0085] c4 is the residual concentration of the target heavy metal ion after adsorption, mg / L.

[0086] Then the average vertical migration of heavy metal ions per unit area is calculated according to the following formula:

[0087]

[0088] In the above formula: R is the recovery rate of the adsorption resin for the target heavy metal element, %;

[0089] M is the vertical migration amount of heavy metal ions per unit area during the monitoring period, mg / m 2 ·d;

[0090] c is the mass concentration of the target heavy metal element in the sample to be tested, mg / L;

[0091] f is the dilution factor of the eluent containing heavy metal ions;

[0092] V is the total volume of the eluent containing heavy metal ions, L;

[0093] S is the horizontal area where the monitoring resin is laid, m 2 ;

[0094] D is the number of monitoring days, d.

[0095] Next, the heavy metal ion Cu in soil leachate 2+ The calculation of the vertical migration amount is taken as a specific example to further illustrate the implementation mode of the present invention.

[0096] Through on-site investigation, 300 mL of representative background soil leachate from the section to be monitored at the contaminated site was collected to determine the adsorption capacity of the adsorption resin layer on Cu 2+ Recovery rate R data:

[0097] A 10mm x 500mm chromatography column was filled with adsorption resin, the upper layer was chelating resin, the filling height was 150mm, and the lower layer was cation exchange resin, the filling height was 150mm. A known concentration of target Cu was added to the leachate. 2+ The standard solution is used as the internal standard, so that the Cu 2+ The concentration was about 20 mg / L. After loading the column, the solution flow rate was controlled at 10 BV / H, and the adsorbed solution was collected. Atomic absorption spectrophotometry was used to analyze Cu 2+ The content of Cu in the solution before and after adsorption was analyzed. 2+ The concentrations are 20.17 mg / L and 16.64 mg / L respectively. According to the formula Calculate the adsorption of the resin layer on Cu in the contaminated site 2+ The recovery rate R is: 82.5%;

[0098] The monitoring device is deployed in the soil layer of the target contaminated site, with a horizontal area of ​​1m 2 , the monitoring duration is 7 days. When the set time is reached, the control system intervenes, controls the baffle plate 8 to move, and the filter holes at the bottom of the upper heavy metal elution frame 11 and the lower heavy metal elution frame 12 are closed. The control valve on the eluent container 20 pipeline is opened first, and 2mol / L hydrochloric acid solution is pumped into the heavy metal eluent injection port 13 by the eluent container 20, and the flow rate is 3BV / H, and the consumption is 3BV. The solution elutes the heavy metal ions adsorbed in the chelating resin layer filling material along the elution path separated by the partition 18, and flows into the cation exchange resin layer from the eluent through hole 14, and elutes the heavy metal ions adsorbed in the cation exchange resin layer along the partition path. Finally, the eluent flows out through the heavy metal eluent recovery port 15 and is collected in the eluent collection container 22. The total volume of the eluent is about 200mL.

[0099] During laboratory analysis, 5 mL of eluate was collected from the collection bottle and filtered with a 0.45 μm water-based microporous filter membrane; the filtered eluate was diluted 10 times. Referring to the instrument conditions and analysis steps specified in the standard "Determination of Copper, Zinc, Lead, Nickel and Chromium in Soil and Sediment by Flame Atomic Absorption Spectrophotometry" HJ-2009, the concentration of the diluted eluate sample was analyzed using an atomic absorption spectrophotometer to measure the Cu content in the sample. 2+ The mass concentration is 14.31 mg / L.

[0100] According to the formula, Cu per unit area 2+ The calculation process of the average vertical migration amount M is:

[0101]

[0102] After calculation, the in-situ resin adsorption monitoring method was used to measure the Cu per unit area of ​​the monitoring site. 2+ The average vertical migration amount M is 4.96 mg / m 2 ·d.

[0103] The monitoring device and method provided by the present invention innovatively realize long-term in-situ dynamic monitoring, making up for the shortcomings of the existing technology of "stratified sampling + post-harvest analysis", and can obtain the migration and accumulation of heavy metal ions in the monitoring section at different time scales. Determining the average vertical migration amount M of heavy metal ions can provide a solution for soil environmental researchers to grasp the degree of pollution of the target site, which is conducive to the smooth implementation of work that urgently needs in-situ monitoring, such as the evaluation of soil remediation effects of contaminated sites, the verification of the isolation and closure effects of treatment projects, and the investigation of soil quality in agricultural production.

[0104] The above is only one embodiment of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the attached claims.

Claims

1. A heavy metal vertical migration monitoring device for contaminated sites, characterized by: The monitoring device comprises an ion monitoring sensor system and a heavy metal vertical migration collection device buried in the soil layer to be monitored, the heavy metal vertical migration collection device comprises a cylindrical frame (7), a bottom support leg (9) and a heavy metal migration collection structure layer arranged in the cylindrical frame (7), the top surface and the bottom surface of the cylindrical frame (7) are both mesh structures, and the heavy metal migration collection structure layer comprises, from top to bottom, an upper isolation medium layer (1), an upper filter medium layer (2), a chelating resin layer (3), a cation exchange resin layer (4), a lower isolation medium layer (5), and a lower filter medium layer (6); The chelate resin layer (3) and the cation exchange resin layer (4) are respectively placed in an upper heavy metal elution frame (11) and a lower heavy metal elution frame (12); the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12) are both upper open cylindrical frames matching the cylindrical frame (7), and filter holes (10) are arranged on the bottom surface of the frames; the upper heavy metal elution frame (11) is provided with a heavy metal eluent injection port (13), the bottom surface of the upper heavy metal elution frame (11) is provided with an eluent through hole (14), and the lower heavy metal elution frame (12) is provided with a heavy metal eluent recovery port (15); A movable baffle (8) is provided at the bottom of the upper and lower metal elution frames, respectively, and the movable baffle (8) is provided with a hollow structure matching the filter holes on the bottom surface of the metal elution frame; during the heavy metal migration and collection process, the hollow structures of the movable baffle (8) in the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12) correspond to the filter holes (13), and at this time, the bottom surfaces of the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12) are both open. Start; during the heavy metal elution process, the movable baffles (8) of the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12) are moved to a state where the hollow structure and the filter hole (10) are completely offset. At this time, the filter holes on the bottom surfaces of the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12) are closed, and the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12) are connected via the eluent through hole (14); The ion monitoring sensor system comprises a heavy metal ion monitoring device (16) arranged on the ground and a heavy metal ion sensor (17) arranged in the middle of an upper filter medium layer (2) and a lower filter medium layer (6), wherein the heavy metal ion sensor (17) is communicatively connected with the heavy metal ion monitoring device (16).

2. The device for monitoring vertical migration of heavy metals in contaminated sites according to claim 1, characterized in that: The upper heavy metal elution frame (11) and the lower heavy metal elution frame (12) are divided into a plurality of elution chambers (19) connected in sequence by a plurality of vertically arranged partitions (18) in the frame body, the filter holes are evenly distributed on the bottom surface of each elution chamber (19) in the shape of strips, the heavy metal eluent injection port (13) is connected to the first elution chamber on one side of the upper heavy metal elution frame (11), the eluent through hole (14) is opened on the bottom surface of the last elution chamber on the other side of the upper heavy metal elution frame (11), and is connected to the last elution chamber on the same side of the lower heavy metal elution frame (12), and the heavy metal eluent recovery port (15) is connected to the first elution chamber on the other side of the lower heavy metal elution frame (12).

3. A heavy metal vertical migration monitoring device for contaminated sites according to claim 1 or 2, characterized in that: The ion sensor (12) is an ion selective electrode probe that selectively responds to calcium or magnesium ions, and converts ion concentration information into an electrical signal, which is transmitted through a line to a data processor of the ion monitoring device (11), and displayed on a display instrument of the ion monitoring device (11).

4. A device for monitoring vertical migration of heavy metals in contaminated sites according to claim 1 or 2, characterized in that: The monitoring device also includes a heavy metal elution system, which includes an eluent container (20), a cleaning liquid container (21), an eluent collection container (22) and an elution control pipeline (23). One end of the elution control pipeline (23) is connected to the eluent container (20) and the cleaning liquid container (21) through branch pipes, and control valves (24) are provided on the two branch pipes respectively. The other end of the elution control pipeline (23) is connected to the heavy metal eluent injection port (13) of the upper heavy metal elution frame (11), and the eluent collection container (22) is connected to the heavy metal eluent recovery port (15) of the lower heavy metal elution frame (12) through a recovery pipe (25).

5. A heavy metal vertical migration monitoring device for contaminated sites according to claim 1 or 2, characterized in that: The bottom legs (10) are provided with four and are evenly distributed at the bottom of the cylindrical frame (7). Each bottom leg (10) is 24 to 35 cm long and has a conical tip at its bottom end, which is welded to the bottom of the cylindrical frame (7). The cylindrical frame (7) is made of a 2 to 3 mm thick carbon steel plate to form a cylindrical structure with upper and lower openings. The cylindrical wall is a double-layer hollow structure, and the width of the hollow layer is 1.8 to 2.2 cm, which is used for laying pipelines and lines. A groove for placing a heavy metal migration collection structure layer is provided on the inner wall of the cylindrical frame (7).

6. A heavy metal vertical migration monitoring device for contaminated sites according to claim 1 or 2, characterized in that: The upper isolation medium layer (1) and the upper filter medium layer (2) are placed in an upper filter mesh frame (17), and the lower isolation medium layer (5) and the lower filter medium layer (6) are placed in a lower filter mesh frame (18). Both the upper filter mesh frame (17) and the lower filter mesh frame (18) adopt an upper open cylindrical structure that matches the cylindrical frame (7), and the bottom surface thereof adopts a grid-shaped filter plate; the upper filter mesh frame (17), the upper heavy metal elution frame (11), the lower heavy metal elution frame (12) and the lower filter mesh frame (18) are sequentially embedded in the cylindrical frame (7) from top to bottom.

7. A heavy metal vertical migration monitoring device for contaminated sites according to claim 1 or 2, characterized in that: The upper isolation medium layer (1) and the lower isolation medium layer (5) are both filled with medium-coarse sand with a particle size of 0.5-2 mm, and the filling layer thickness is 8-12 cm; the upper filter medium layer (2) and the lower filter medium layer (6) are both filled with gravel with a particle size of 5-10 mm, and the filling layer thickness is 8-12 cm; the isolation medium layer and the filter medium layer are both wrapped with a non-woven geotextile with a porosity of 60%-80% and a thickness of 0.5-1 mm; the chelating resin layer (3) uses a chelating resin containing iminodiacetic acid functional groups with a particle size of 0.5-2 mm, and the filling thickness is 3-5 cm; the cation exchange resin layer (4) uses a cation exchange resin with a particle size of 0.5-2 mm, and the filling thickness is 3-5 cm; and a non-woven geotextile with a porosity of 60%-80% is laid at the bottom of the chelating resin layer (3) and the cation exchange resin layer (4).

8. The device for monitoring vertical migration of heavy metals in contaminated sites according to claim 2, characterized in that: The movable baffle (8) is located below the bottom plates of the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12); a support frame (800) for mounting the movable baffle (8) is provided at the bottom of the upper heavy metal elution frame (11) and the lower heavy metal elution frame (12); the movable baffle (8) comprises a plurality of baffles having a width greater than the diameter of the filter hole (10); the arrangement direction of the plurality of baffles (8) is consistent with the arrangement direction of the filter hole (10); the length of each baffle (8) is greater than the arrangement length of one filter hole (10); and the plurality of baffles are connected by The rods (801) are connected as one body, an electric push rod (802) is provided at one end of the connecting rod (801), the electric push rod (802) is fixedly mounted on the support frame (800), the other end of the connecting rod (801) is slidably connected to the other side of the support frame (800), a slide groove (803) is correspondingly provided on the support frame (800), the other end of the connecting rod (801) is embedded in the slide groove (803), and a limit block is provided at the end; under the action of the electric push rod (802), the plurality of baffles are driven to move horizontally at the same time, so that the filter hole (10) is completely blocked or opened.

9. A method for monitoring the vertical migration of heavy metals in a contaminated site, characterized in that: The monitoring method uses the contaminated site heavy metal vertical migration monitoring device according to any one of claims 1 to 8 to monitor the vertical migration of heavy metals in contaminated soil, and calculates the vertical migration amount of heavy metals in the monitoring area. The specific steps of the method are as follows: S1. The heavy metal vertical migration collection device is buried in the soil layer at the target depth, the heavy metal ion monitoring device is placed on the ground, and the heavy metal ion sensor installed in the heavy metal vertical migration collection device is connected to the heavy metal ion monitoring device on the ground through a signal line, and the heavy metal collection amount of the heavy metal vertical migration collection device buried in the soil layer at the target depth is monitored by the heavy metal ion monitoring device; S2. When the ion concentration ratio monitored by the heavy metal ion sensor is lower than the product of the recovery rate of the adsorption resin for the target metal ion and the saturation coefficient, the heavy metal vertical migration collection device is taken out to prepare for heavy metal elution; S3. Control the movable plate at the bottom of the upper heavy metal elution frame and the lower heavy metal elution frame to move horizontally, and completely close the filter holes at the bottom of the upper heavy metal elution frame and the lower heavy metal elution frame; use hydrochloric acid solution as eluent, pump the eluent through the heavy metal eluent injection port, use ion exchange method to elute the heavy metal ions in the chelating resin layer and the cation exchange resin layer, and collect the eluent containing heavy metal ions through the heavy metal eluent recovery port; after the elution is completed, pump the cleaning agent through the heavy metal eluent injection port, and reuse after cleaning; the concentration of the hydrochloric acid solution is 1.5-2mol / L, the amount is 2-3BV, and the flow rate is 2-4BV / H; the cleaning agent is pure water, the amount of the pure water is 3-5BV, and the flow rate is 3-4BV / H; S4. For the eluate containing heavy metal ions collected in step S3, the recovery rate of the chelating resin layer and the cation exchange resin layer for specific target heavy metal ions is determined by the spike recovery method; the eluate containing heavy metal ions is filtered and diluted to obtain a sample to be tested, and an atomic absorption spectrophotometer or a fluorescence photometer is used to test the sample to be tested to determine the mass concentration of the target heavy metal element in the eluate; and then the average vertical migration amount of heavy metal ions per unit area is calculated according to the following formula: In the above formula: R is the recovery rate of the adsorption resin for the target heavy metal element, %; M is the vertical migration amount of heavy metal ions per unit area during the monitoring period, mg / m 2 ·d; C is the mass concentration of the target heavy metal element in the sample to be tested, mg / L; f is the dilution factor of the eluent containing heavy metal ions; V is the total volume of the eluent containing heavy metal ions, L; S is the horizontal area where the monitoring resin is laid, m 2 ; D is the number of monitoring days, d.

10. A method for monitoring vertical migration of heavy metals in contaminated sites according to claim 9, characterized in that: The recovery rate and saturation coefficient of the target metal ion in the adsorption resin in step S2 are in the range of 0.6 to 0.8, and the specific formula is as follows: Where: c1 is the monitoring concentration of the target element in the upper isolation medium layer, mg / L; c2 is the monitoring concentration of the target element in the lower isolation medium layer, mg / L; α is the saturation coefficient of the adsorption resin for the target element; R is the recovery rate of the target element by the adsorption resin, %; In the step S4, the recovery R of the chelating resin layer and the cation exchange resin layer for specific target heavy metal ions is calculated according to the following formula: Where: c3 is the spike concentration of target heavy metal ions before adsorption, mg / L; c4 is the residual concentration of the target heavy metal ion after adsorption, mg / L.

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