Multifunctional experimental system for simulating migration and transformation of micro-plastics in landfill environment

Abstract

The invention provides a multifunctional experimental system for simulating migration and transformation of micro-plastics in a landfill environment, comprising: a columnar migration device filled with a landfill soil medium, the bottom of which is provided with a liquid inlet interface and a gas-liquid interface, and the top of which is provided with a liquid outlet; the liquid inlet system is connected to the liquid inlet connector through a first peristaltic pump; the temperature control module comprises a flexible heating film arranged around the outer wall of the columnar migration device and a temperature controller, and the flexible heating film is connected with the temperature controller through a temperature control connector, an integrated heating element and a wire; the micro-nano bubble generating device comprises a CH4 gas cylinder, a pressure reducing valve and a micro-nano bubble generator which are connected in sequence, a micro-bubble aeration head is arranged on the micro-nano bubble generator, the micro-bubble aeration head is partially and directly immersed in a preset water body, a high-dispersity bubble water solution is generated under a gas-liquid interface, and the CH4 gas cylinder is used for generating CH4 gas. The gas is quantitatively conveyed to the bottom of the columnar migration device through a second peristaltic pump connected to the downstream, and the dissolution of the landfill gas in the pore water and the gas-liquid interface action are simulated.

Description

Technical Field

[0001] The present invention relates to the technical field of microplastic migration and transformation, and in particular to a multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment. Background Art

[0002] With the massive influx of plastic waste into solid waste landfill systems, landfills have become a significant source and destination of microplastics in the surface environment, posing a potential threat to surrounding ecosystems and groundwater resources. During long-term landfilling, plastic products fragment and decompose due to temperature fluctuations, oxidative aging, and microbial action, releasing vast quantities of microplastic particles. Furthermore, rainfall infiltration, anaerobic degradation of organic matter, and heat accumulation within the landfill trigger significant temperature and humidity fluctuations and the generation of landfill gases (such as methane and carbon dioxide), creating a dynamic, evolving heat-gas-water complex. Within this environment, microplastics may not only migrate with leachate into the surrounding soil and groundwater but also undergo complex adsorption-desorption, transformation, or co-migration behaviors at multiphase interfaces, such as solid-liquid and liquid-gas interfaces. Furthermore, landfill environments are generally characterized by unsaturation, heterogeneity, and slow-varying properties. These multi-scale, multi-process coupling effects profoundly influence the spatiotemporal behavior of microplastics and the contaminants they carry. Existing research still finds it difficult to systematically characterize the migration and transformation mechanism of microplastics under such complex landfill conditions. There is an urgent need to build a controllable, observable and repeatable experimental platform to reveal its environmental fate and risk characteristics.

[0003] Patent application document CN105300843A discloses a column device that can simulate the migration of pollutants under different hydrogeological conditions, including a pollutant delivery device, a temperature control device, a pressure measuring device, a medium filling device and a sample collection device. The pollutant delivery device includes a syringe, a syringe pump, and a silicone tube; the temperature control device includes a water bath thermostat, a peristaltic pump, a temperature sensor probe, a thermometer, a spiral tube and a plexiglass tube; the pressure measuring device includes a pressure sensor probe, a pressure gauge and a wire; the medium filling device includes a stainless steel tube, a 200-mesh stainless steel mesh, an internal thread two-way pagoda and a constant temperature box; the sample collection device includes a collection probe, a sample rack and a console.

[0004] At present, some research has designed simulation experimental devices for pollutant migration and transformation behavior. Common systems are mostly based on columnar reactors, with liquid inflow and sampling units, used to study the vertical migration characteristics of pollutants in soil. This type of device mainly includes: a packing column, a sampling system, a liquid outlet system, a sampling port, an embedded sensor, and an automatic sample collector. The sampling system inputs pollutants into the packing column. During the vertical migration of pollutants along the column, the embedded sensor can monitor the changes in environmental parameters, and the sampling port can be used to obtain offline samples at different depths. After the pollutants penetrate to the bottom of the column, they are discharged through the liquid outlet system and dynamically and automatically sampled and collected in segments by the automatic sample collector, providing a data basis for subsequent pollutant analysis.

[0005] However, there are the following defects: (1) Although a variety of pollutant migration experimental devices have been used to study soil and groundwater pollution behavior, most of these devices use the vadose zone as the simulation object and focus on the geochemical processes and pollutant migration behavior in the saturated aquifer. The interior of the landfill is often accompanied by physical squeezing, seepage sedimentation, dissolution and release of pollutants, and metabolic transformation of microorganisms, showing multi-field coupling and nonlinear dynamic change characteristics; at the same time, under the effects of long-term rainfall infiltration, anaerobic decomposition of microorganisms, and accumulation of pollutants, a microenvironment with high organic load, high temperature, high salt, and strong reducing properties is formed. (2) Existing pollutant migration experimental devices are generally based on idealized saturated porous media and lack systematic simulation of key elements in the real landfill environment. In particular, they lack consideration of the dynamic generation process of landfill gases such as methane, the complex multiphase migration behavior of pollutants in the unsaturated zone, and the significant impact of the gas-liquid interface on the transformation and distribution of pollutants. As a result, the experimental results cannot truly reflect the migration and transformation mechanism of pollutants such as microplastics in the landfill environment under multi-field coupling conditions, which seriously limits its effectiveness and representativeness in landfill pollution control and risk assessment. Summary of the Invention

[0006] In view of the defects in the prior art, the purpose of the present invention is to provide a multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment.

[0007] The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment provided by the present invention comprises: The columnar migration device is a vertically placed transparent cylindrical structure filled with landfill soil medium, with a liquid inlet interface and a gas-liquid interface at the bottom, a liquid outlet at the top, and a layer of glass beads and nylon gauze at the bottom; A liquid inlet system, connected to the liquid inlet interface via a first peristaltic pump, for injecting a microplastic suspension or deionized water into the columnar migration device; A temperature control module, comprising a flexible heating film arranged around the outer wall of the columnar migration device and a temperature controller, wherein the flexible heating film is connected to the temperature controller via a temperature control connector, an integrated heating element and a wire to adjust the internal temperature of the columnar migration device; The micro-nano bubble generating device comprises a A gas cylinder, a pressure reducing valve, and a micro-nano bubble generator are provided. The gas-liquid interface is connected to the micro-nano bubble generator via a gas guide hose and is used to inject methane micro-nano bubbles into the bottom of the columnar migration device. The micro-nano bubble generator is provided with a micro-bubble aeration head, which is directly immersed in a preset water body to generate a highly dispersed bubble aqueous solution at the gas-liquid interface. The generated micro-nano bubble aqueous solution is then quantitatively transported to the bottom of the columnar migration device via a second peristaltic pump connected downstream, simulating the dissolution of landfill gas in pore water and the gas-liquid interface effect.

[0008] Preferably, it also includes four sampling ports and an embedded sensor interface distributed at different heights of the columnar migration device, and the sampling ports are inserted into the landfill soil medium for stratified sampling.

[0009] Preferably, the columnar migration device is made of organic glass, and the top liquid outlet is connected to an automatic collector through a sealed joint for dynamically collecting the outflow liquid and analyzing the changes in microplastic concentration.

[0010] Preferably, a sensor interface is used as the sampling port, and the sensor interface is connected to a data acquisition system or a cloud platform through a sealed threaded interface, supporting continuous monitoring and remote data transmission.

[0011] Preferably, the glass bead layer has a thickness of 1 cm and is located above the liquid inlet interface and the gas-liquid interface at the bottom of the columnar migration device, and is used to fix the filling soil and evenly disperse the liquid and gas.

[0012] Preferably, the system also includes a visual monitoring module, including a visual window or a high-resolution CCD image acquisition system arranged on the side wall of the columnar migration device, which is used to observe the migration path of microplastics and the gas-liquid-solid interface effect, and enhance the image contrast through fluorescent tracing or color development reaction.

[0013] Preferably, the first peristaltic pump is connected to the liquid inlet interface at the bottom of the columnar migration device through a hose, which supports two-way flow control and supports switching to inject microplastic suspension or deionized water to simulate microplastic migration and hydraulic disturbance conditions at different stages.

[0014] Preferably, the sampling port is a pluggable sealing structure, and solid samples are collected through a sampler during sampling. After sampling, the spatial distribution characteristics of microplastics are determined by freeze drying and ultrasonic separation technology.

[0015] Preferably, the four sampling ports are spaced about 3 cm apart and are located 3 cm, 6 cm, 9 cm and 12 cm from the bottom of the columnar migration device, respectively.

[0016] Preferably, the process of a microplastic migration and transformation experiment simulating a landfill environment is as follows: Step 1: Prepare the soil sample for the experiment and fill it into the column by compacting it layer by layer. Four sampling ports are evenly spaced on the column. Each sampling port is a sealed structure and is usually closed and opened when sampling. The sampling port is connected to an external sampler, which is a pluggable device for collecting solid samples. Step 2: The first peristaltic pump is set to a constant flow rate to inject deionized water from the bottom inlet interface of the columnar migration device through the hose to perform saturation treatment from bottom to top, excluding air, and continuing saturation for 2 hours; Step 3: Start the temperature control device. The outer wall of the column is covered and fixed with a flexible heating film to ensure that the heating film is tightly attached to the surface of the column. The flexible heating film is connected to the temperature controller through the temperature control module to set and maintain the temperature range required for the experimental environment inside the column. The flexible heating film is connected to the wire through the temperature control connector. The integrated heating element is attached to the surface of the column to provide a uniform and controllable heating environment. Step 4: Connect The gas cylinder starts the micro-nano bubble generator and slowly injects micro-nano methane bubbles from the bottom to form a gas-liquid coexistence environment, simulating the landfill gas production conditions; Step 5: Mix the prepared microplastic suspension with the generated Micro-nano bubbles are pumped in from the bottom, starting at 0 PV. After flowing out from the top, the outflow liquid is collected by an automatic collector, and the change of pollutant concentration in the outflow liquid over time is measured. Step 6: After continuously injecting 10 PV of microplastic suspension, continue to pump deionized water through the first peristaltic pump, maintaining the same flow rate and environmental conditions to promote further migration and diffusion of microplastics in the porous medium, and continue for 5 PV; Step 7: Stop water injection, turn off the temperature control device, wait for the temperature to drop to room temperature, connect the sampling valve and the columnar migration device through a sealed threaded interface; open the sampling valve, collect soil samples after the experiment through the sampler, freeze-dry the soil samples collected at different depths, mix them with the background solution, and then ultrasonically separate them, measure the concentration of microplastics in the suspension, and obtain the spatial distribution characteristics of microplastics in the column.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention aims to construct an experimental system suitable for the study of microplastic migration and transformation in landfill environments, which can effectively simulate key environmental characteristics such as microbial anaerobic action, gas generation and dynamic changes in leachate in landfills. The device integrates a controllable sampling and filtration device, a gas regulation module, a temperature control unit and a multi-point embedded monitoring system, which can synchronously collect multidimensional data and dynamically capture the migration behavior and morphological evolution process of microplastics in the gas-liquid-solid multiphase interface. Through this platform, the migration path and interface transformation law of microplastics under the coupling of physical, chemical and biological effects under complex landfill conditions can be more realistically reproduced, thereby providing a more representative and applicable experimental basis for landfill environmental risk assessment and pollution control technology research and development. (2) The present invention intends to construct an experimental system with controllable multi-dimensional parameters, clear structural hierarchy, and embeddable high-precision sensing and sampling devices, so as to achieve accurate characterization of the spatiotemporal behavior of microplastics under multi-source disturbances, multi-phase migration and complex environmental conditions in the landfill environment, fundamentally improve the authenticity, continuity and data analysis capabilities of experimental simulations, and provide key technical support for the mechanism analysis and pollution prevention and control of landfill environmental pollution processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings: Figure 1 Schematic diagram of the experimental setup; Figure 2 Three-view drawing of the column and supporting devices; Figure 3 Schematic diagram of the flexible heating film temperature control system structure. DETAILED DESCRIPTION

[0019] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0020] Example like Figures 1 to 3The present invention provides a multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment, the structure of which includes: a columnar migration device 1, a liquid inlet system 2, a temperature control module 3, a micro-nano bubble generating device 4 and an embedded sampling and monitoring system 5. Among them, the columnar migration device 1 is the main part of the experimental system. The bottom of the columnar migration device 1 is provided with a liquid inlet interface 12 and a gas-liquid interface 13, which are respectively connected to the liquid inlet system 2 and the micro-nano bubble generating device 4. The temperature control module 3 is arranged on the outside of the columnar migration device 1, in the form of a flexible heating film, and is arranged around the outer wall of the columnar migration device 1. The embedded sampling and monitoring system 5 includes four sampling ports and embedded sensors distributed at different heights of the columnar migration device 1.

[0021] The columnar migration device 1 is made of plexiglass and is a vertically positioned cylindrical structure with an inner diameter of 5 cm and a height of 16 cm. Its transparent structure facilitates observation of internal changes. The columnar migration device 1 is pre-filled with a predetermined height of landfill soil medium. It features a sealed liquid outlet 101 at the top, a liquid inlet 12, and a gas-liquid inlet 13 at the bottom. Nylon gauze 102 and a 1-cm-thick layer of glass beads 11 are located at the top and bottom, respectively, to secure the fill soil and ensure uniform liquid and gas flow. The columnar migration device 1 is equipped with four vertically spaced sampling ports 103, approximately 3 cm apart, located approximately 3 cm, 6 cm, 9 cm, and 12 cm from the bottom of the device. These sampling ports can be inserted into the fill soil, enabling vertical cross-sectional sampling without disturbing the overall soil structure. The outer wall of the columnar migration device 1 is coated with a flexible heating film 302, forming a temperature control system. Connected to a temperature controller 301, the internal temperature of the column can be adjusted according to experimental needs, simulating the high-temperature environment within a landfill. The micro-nano bubble generating device 4 is arranged on one side of the lower part of the columnar migration device 1, and the gas source is Gas cylinder 401 regulates its output pressure via a connected pressure reducing valve. The decompressed gas enters micro-nano bubble generator 402 through a gas hose. Micro-nano bubble generator 402 is equipped with a micro-bubble aeration head 403, which is partially immersed in a pre-set body of water. This head generates a highly dispersed bubble-water solution at the gas-liquid interface. This solution is quantitatively extracted and transported by a second peristaltic pump 404 connected downstream, simulating the generation, migration, and gas-liquid interface of landfill gas.

[0022] The existing sampling port was replaced with a standardized embedded sensor interface for integrating multiple types of in-situ online monitoring sensors. This sensor interface is compatible with sensors for water quality, gas, temperature, conductivity, oxidation-reduction potential (ORP), dissolved oxygen (DO), and other parameters, enabling continuous monitoring and real-time data acquisition at various depths. Furthermore, the sensor interface facilitates integration with data acquisition systems and cloud-based data platforms, providing continuous and reliable data support for subsequent data analysis, modeling, and forecasting.

[0023] Integrated visualization or image monitoring technology can be implemented, with a viewing window or image acquisition system (such as a high-resolution CCD) installed in the column to assist in observing microscopic processes such as microplastic migration patterns and gas-liquid-solid interface interactions. In complex microplastic systems, image contrast can be enhanced through fluorescent tracing or color development, further improving the clarity of observation of interfacial processes.

[0024] The steps for a complete microplastic migration and transformation experiment simulating a landfill environment are as follows: 1. Prepare the soil sample for the experiment and compact it layer by layer into the cylinder to a height of approximately 13 cm. Four sampling ports 501 are evenly spaced, approximately 3 cm apart. Each sampling port 501 is sealed and normally remains closed, opening for sampling. Each sampling port 501 is connected to an external sampler 502, a pluggable device used to collect solid samples.

[0025] 2. Pre-saturation: The first peristaltic pump 202 slowly injects deionized water from the bottom liquid inlet interface 12 of the columnar migration device 1 through the hose at a constant flow rate of 1 mL / min to perform saturation treatment from bottom to top, remove air, and continue saturation for 2 hours.

[0026] 3. Start the temperature control device 3. The outer wall of the column is covered and fixed with a flexible heating film 302 to ensure that the heating film is tightly fitted to the surface of the column. The flexible heating film 302 is connected to the temperature controller 301 through the temperature control module, which can set and maintain the required temperature range (25-75°C) for the experimental environment inside the column. The flexible heating film 302 is connected to the wire 33 through the temperature control connector 31. The integrated heating element 32 is attached to the surface of the column to provide a uniform and controllable heating environment.

[0027] 4. Connect The gas cylinder 401 starts the micro-nano bubble generator 402 and slowly injects micro-nano methane bubbles from the bottom to form a gas-liquid coexistence environment and simulate the landfill gas production conditions.

[0028] 5. Combine the prepared microplastic suspension 201 and the generated Micro-nano bubbles are pumped in from the bottom, starting at 0 PV. After flowing out from the top, the outflow liquid is collected by an automatic collector, and the change of pollutant concentration in the outflow liquid over time is measured.

[0029] 6. After continuously injecting 10 PV of the microplastic suspension, continue to pump deionized water through the first peristaltic pump 202, maintaining the same flow rate and environmental conditions to promote further migration and diffusion of microplastics in the porous medium, and continue for 5 PV.

[0030] 7. Stop water injection and close temperature control device 3. Wait until the temperature drops to room temperature. Connect sampling valve 503 to columnar migration device 1 via a removable sealed threaded interface 504. Open sampling valve 503 and collect soil samples after the experiment using sampler 502. Soil samples collected at different depths are freeze-dried, mixed with a background solution, and ultrasonically separated. The concentration of microplastics in the suspension is measured to determine the spatial distribution characteristics of the microplastics within the column.

[0031] The present invention has the following beneficial effects: (1) Realistic simulation capability of multi-field coupled environment: This device can comprehensively simulate typical unsaturated state, high temperature, high salinity and other complex conditions in landfill environment, and has strong experimental environment reduction capability, which is significantly better than traditional saturated column migration experiment.

[0032] (2) Integration and application of micro-nano bubble injection system: The bottom of the device is equipped with an injection port for the micro-nano bubble generator, which can continuously inject Nanobubbles are used to simulate the effects of landfill gas dissolution in pore water and the gas-liquid interface process on the migration and transformation of microplastics. This is an innovative configuration among such experimental devices at home and abroad.

[0033] (3) Design of external soft film heating and temperature control system: The temperature of the column is controlled by using a flexible heating film combined with a soft film coating. This not only improves the heat conduction efficiency, but also takes into account the observation function of the transparent column, thus realizing the simulation of high temperature disturbance conditions in the landfill environment.

[0034] (4) Ability to couple microplastic migration with hydraulic changes: Peristaltic pumps are installed on the upper and lower parts to accurately control the infiltration and drainage rates, and to simulate the dynamic migration of microplastics in unsaturated porous media under hydraulic disturbance conditions. At the same time, long-term, multi-stage microplastic migration experiments can be carried out.

[0035] In the description of this application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0036] Those skilled in the art will appreciate that, in addition to implementing the system, device, and various modules provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, embedded microcontrollers, and the like by logically programming the method steps. Therefore, the system, device, and various modules provided by the present invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; the modules for implementing various functions can also be considered both software programs for implementing the method and structures within the hardware component.

[0037] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment, characterized by: include: The columnar migration device (1) is a vertically placed transparent cylindrical structure filled with a landfill soil medium, with a liquid inlet interface (12) and a gas-liquid interface (13) provided at the bottom, a liquid outlet (101) provided at the top, and a glass bead layer (11) and nylon gauze (102) distributed at the bottom; a liquid inlet system (2), connected to the liquid inlet interface (12) via a first peristaltic pump (202), for injecting a microplastic suspension or deionized water into the columnar migration device (1); A temperature control module (3) includes a flexible heating film (302) arranged around the outer wall of the columnar migration device (1) and a temperature controller (301), wherein the flexible heating film (302) is connected to the temperature controller (301) via a temperature control connector (31), an integrated heating element (32) and a wire (33) to adjust the internal temperature of the columnar migration device (1); The micro-nano bubble generating device (4) comprises a CH4 gas cylinder (401), a pressure reducing valve, and a micro-nano bubble generator (402) connected in sequence. The gas-liquid interface (13) is connected to the micro-nano bubble generator (402) via a gas guide hose and is used to inject methane micro-nano bubbles into the bottom of the columnar migration device (1). The micro-nano bubble generator (402) is provided with a micro-bubble aeration head (403). The micro-bubble aeration head (403) is partially directly immersed in a preset water body to generate a highly dispersed bubble aqueous solution at the gas-liquid interface. The generated micro-nano bubble aqueous solution is then quantitatively transported to the bottom of the columnar migration device (1) via a second peristaltic pump (404) connected downstream, simulating the dissolution of landfill gas in pore water and the gas-liquid interface effect.

2. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 1, characterized in that: It also comprises four sampling ports (103) distributed at different heights of the columnar migration device (1) and an embedded sensor interface, wherein the sampling ports (103) are inserted into the landfill soil medium for layered sampling.

3. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 1, characterized in that: The columnar migration device (1) is made of organic glass, and the top liquid outlet (101) is connected to an automatic collector via a sealed joint, which is used to dynamically collect the outflow liquid and analyze the changes in microplastic concentration.

4. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 2, characterized in that: A sensor interface is used as a sampling port, and the sensor interface is connected to a data acquisition system or a cloud platform through a sealed threaded interface, supporting continuous monitoring and remote data transmission.

5. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 1, characterized in that: The glass bead layer (11) has a thickness of 1 cm and is located above the liquid inlet interface (12) and the gas-liquid interface (13) at the bottom of the columnar migration device (1), and is used to fix the filling soil and evenly disperse the liquid and gas.

6. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 1, characterized in that: The system also includes a visual monitoring module, including a visual window or a high-resolution CCD image acquisition system arranged on the side wall of the columnar migration device (1), for observing the migration path of microplastics and the gas-liquid-solid interface effect, and enhancing the image contrast through fluorescent tracing or color development reaction.

7. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 1, characterized in that: The first peristaltic pump (202) is connected to the liquid inlet interface (12) at the bottom of the columnar migration device (1) via a hose, supporting bidirectional flow control and switching between injecting microplastic suspension or deionized water to simulate microplastic migration and hydraulic disturbance conditions at different stages.

8. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 2, characterized in that: The sampling port (103) is a pluggable sealing structure. During sampling, a solid sample is collected through a sampler, and after sampling, the spatial distribution characteristics of microplastics are determined by freeze drying and ultrasonic separation technology.

9. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 2, characterized in that: The four sampling ports (103) are spaced approximately 3 cm apart and are located at 3 cm, 6 cm, 9 cm and 12 cm from the bottom of the columnar migration device (1).

10. The multifunctional experimental system for simulating the migration and transformation of microplastics in a landfill environment according to claim 1, characterized in that: The process of a microplastic migration and transformation experiment simulating a landfill environment is as follows: Step 1: Prepare the soil sample for the experiment and fill it into the column by compacting it layer by layer. Four sampling ports are evenly spaced on the column. Each sampling port is a sealed structure and is usually closed and opened when sampling. The sampling port is connected to an external sampler, which is a pluggable device for collecting solid samples. Step 2: The first peristaltic pump is set to a constant flow rate to inject deionized water from the bottom inlet interface of the columnar migration device through the hose to perform saturation treatment from bottom to top, excluding air, and continuing saturation for 2 hours; Step 3: Start the temperature control device. The outer wall of the column is covered and fixed with a flexible heating film to ensure that the heating film is tightly attached to the surface of the column. The flexible heating film is connected to the temperature controller through the temperature control module to set and maintain the temperature range required for the experimental environment inside the column. The flexible heating film is connected to the wire through the temperature control connector. The integrated heating element is attached to the surface of the column to provide a uniform and controllable heating environment. Step 4: Connect the CH4 gas cylinder, start the micro-nano bubble generator, and slowly inject micro-nano methane bubbles from the bottom to form a gas-liquid coexistence environment to simulate landfill gas production conditions; Step 5: The pre-prepared microplastic suspension and the generated CH4 micro-nano bubbles are pumped in from the bottom, with the start of this time as 0PV. After flowing out from the top, the outflow is collected using an automatic collector, and the change in the microplastic concentration in the outflow over time is measured; Step 6: After continuously injecting 10 PV of microplastic suspension, continue to pump deionized water through the first peristaltic pump, maintaining the same flow rate and environmental conditions to promote further migration and diffusion of microplastics in the porous medium, and continue for 5 PV; Step 7: Stop water injection, turn off the temperature control device, wait until the temperature drops to room temperature, and connect the sampling valve and the columnar migration device through a sealed threaded interface; Open the sampling valve and collect soil samples after the experiment through the sampler. The soil samples collected at different depths are freeze-dried, mixed with the background solution and ultrasonically separated. The concentration of microplastics in the suspension is measured to obtain the spatial distribution characteristics of microplastics in the column.

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