A simulation monitoring device and method for frozen soil change process

Abstract

The present application relates to a kind of simulation monitoring devices and methods of frozen soil change process.The simulation monitoring device includes thermostat, thermostat is built in image acquisition device and oppositely arranged light source, object table and the frozen soil structure simulation device and temperature control device of setting on object table are set in thermostat, and image processing device is set outside thermostat.The frozen soil structure simulation device is simulated by setting multiple convex parts and setting coating layer on convex part, for simulating soil pore structure characteristics, constructs high simulation nature soil simulation environment, highly restores the pore characteristics of natural soil under freeze-thaw environment and the migration environment of soil pollutant.The simulation monitoring method realizes the simulation and monitoring of the migration behavior of microplastic particles in soil, has excellent simulation and very high experimental precision, and has important significance to the evaluation and management of the environmental problems of widely distributed cold region pollution site.

Description

Technical Field

[0001] This invention relates to the field of microplastic migration, and in particular to a device and method for simulating and monitoring permafrost change processes. Background Technology

[0002] Microplastics, as a novel pollutant, have attracted widespread global attention in recent years. Agricultural activities, such as mulching, wastewater irrigation, and the application of organic fertilizers or sludge, inevitably lead to the entry of microplastic particles into farmland soil. Notably, freeze-thaw cycles caused by temperature changes have a significant impact on the distribution and migration behavior of microplastics. Therefore, studying the migration behavior of microplastics in soil pores during freeze-thaw processes has important practical significance.

[0003] Currently, research on the impact of freeze-thaw cycles on microplastic migration mainly focuses on the changes in microplastic particle and soil physicochemical properties caused by freeze-thaw cycles, and how these changes alter the migration process. Related experiments typically involve pre-treating microplastics or soil with freeze-thaw cycles, followed by microplastic migration column experiments at room temperature. The migration process in soil is studied by comparing the differences in microplastic concentrations in the influent and effluent water. Relevant patent applications include CN109975511A, "Experimental Apparatus and Method for Simulating Microplastic Migration in Soil," CN116223307A, "Microplastic Migration Simulation Device," and CN117169060A, "An Experimental Apparatus and Method for Microplastic Particle Migration in Soil." These patent applications have the advantage of simulating the migration process of microplastics in soil under natural conditions, and their theoretical methods are relatively simple and easy to implement. However, the migration process of microplastics in the above methods is conducted at room temperature and does not consider the migration behavior of microplastics within soil pores during freeze-thaw cycles. Therefore, this application requests an apparatus and method to simulate the migration behavior of microplastic particles under natural soil freeze-thaw conditions. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a simple structure and a simulation monitoring device for the migration of microplastic particles during the soil freeze-thaw process that can highly replicate the soil freeze-thaw environment.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A simulation monitoring device for permafrost change processes includes a constant temperature chamber 1. The constant temperature chamber 1 contains an image acquisition device 2 and a light source 3 arranged opposite to it. The image acquisition device 2 is connected to an image processing device 4. A platform between the image acquisition device 2 and the light source 3 is equipped with a permafrost structure simulation device 6 with high soil simulation accuracy. The permafrost structure simulation device 6 consists of two layers of light-transmitting structure with multiple protrusions 14 between the two layers. The surface of the protrusions 14 is coated with a layer 15. The permafrost structure simulation device 6 has an inlet and an outlet. The permafrost structure simulation device 6 is equipped with a temperature control device 7.

[0007] Furthermore, the frozen soil structure simulation device 6 includes an upper glass layer 12, a lower glass layer 13, and a plurality of irregular protrusions 14 distributed between the upper glass layer 12 and the lower glass layer 13 according to the soil pore distribution information. There are tiny gaps between the protrusions 14, and a coating layer 15 simulating soil characteristics is provided on the surface of the protrusions 14 and the inner surface of the upper and lower glass layers.

[0008] Furthermore, the protrusion 14 is integrally formed with the lower glass layer 13, or the protrusion 14 is integrally formed with the upper glass layer 12, or it is formed by dot-coating.

[0009] Furthermore, the temperature control device 7 includes a first temperature control device and a second temperature control device, located at both ends of the frozen soil structure simulation device 6 and in contact with the upper and lower surfaces of the frozen soil structure simulation device 6.

[0010] Furthermore, the image capturing device 2 includes a camera 10 and an objective lens 11, and the image processing device 4 includes an image acquisition card and a computer.

[0011] Furthermore, the composition of the coating layer 15 by weight percentage is as follows:

[0012] Crosslinking agent 0.5%-5%;

[0013] Photoinitiator 0.01%-0.1%;

[0014] Soluble minerals: 2%-85%;

[0015] Thickener 0%-2%;

[0016] The remainder is deionized water, and the total of all components is 100%.

[0017] Furthermore, the composition of the coating layer 15 by weight percentage is as follows:

[0018] Ethylene glycol dimethacrylate 0.5%-5%;

[0019] Benzyl ketone 0.01%-0.1%;

[0020] Dolomite, calcite, or mica 2%-85%;

[0021] Carboxymethyl cellulose 0%-2%;

[0022] The remainder is deionized water, and the total of all components is 100%.

[0023] The second technical problem to be solved by the present invention is to provide a simulation monitoring method for the migration of microplastic particles in soil pores during freeze-thaw processes, so as to achieve accurate, efficient and real-time monitoring of the migration and distribution of microplastic particles in soil pores during freeze-thaw processes.

[0024] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0025] The method for simulating and monitoring frozen soil using the simulated monitoring device for the frozen soil change process includes the following steps:

[0026] 1) Prepare an aqueous solution containing microplastic particles;

[0027] 2) Inject the aqueous solution containing microplastic particles into the inlet of the frozen soil structure simulation device 6 to fill the interior of the frozen soil structure simulation device 6. Place the frozen soil structure simulation device 6 in the constant temperature chamber 1 and adjust the temperature of the constant temperature chamber 1 and the temperature control device 7 to 1℃~5℃. Let it stand for 10~15 minutes to make the aqueous solution of microplastic particles evenly distributed in the frozen soil structure simulation device 6, and capture the initial distribution state of microplastic particles in the soil pores. During this period, the temperature of the constant temperature chamber 1 and the temperature control device 7 remains consistent.

[0028] 3) After the temperature inside the frozen soil structure simulation device 6 reaches a stable state, the temperature control device 7 lowers the temperature, and one end of the frozen soil structure simulation device 6 is cooled down to below 0°C, while the other end remains at the same temperature as the constant temperature chamber 1, so that the aqueous solution containing microplastic particles freezes unidirectionally from the cold end to the warm end until the aqueous solution freezes and the state is stable.

[0029] 4) Temperature control device 7 raises the temperature, starting from one end of frozen soil structure simulation device 6, so that the frozen aqueous solution containing microplastic particles gradually melts until the aqueous solution is completely liquid.

[0030] The process of steps 2) to 4) above shall be recorded;

[0031] 5) Extract and process image information from the video recordings of the above processes.

[0032] Furthermore, during the simulation monitoring process, before step 2, images of the original state of the upper and lower glass and images of the upper and lower glass covered with mineral particles before the injection of the microplastic aqueous solution are collected.

[0033] Further, the method for preparing the aqueous solution containing microplastic particles in step 1) includes: selecting polyethylene microplastic particles with a diameter in the range of 5~100μm, adding the microplastics to deionized water, and preparing an aqueous solution containing microplastic particles with a mass concentration of 0.05%-0.3%.

[0034] This invention provides a highly realistic and controllable simulation monitoring device and method for the migration of microplastic particles in the pores of frozen soil, capable of accurately replicating the natural soil environment. Furthermore, even without microplastic particles in the water, markers can be placed to reflect changes in water state during freezing, thawing, and flow. Specifically, by simulating the pore structure distribution and surface mineral composition of natural soil particles, the natural soil environment is replicated in the frozen soil structure simulation device 6, greatly improving the simulation accuracy and achieving a high degree of fidelity in the distribution and migration behavior of microplastic particles in soil pores. Temperature control devices 7 are attached to both ends of the frozen soil structure simulation device 6 to precisely regulate the ambient temperature, ensuring the stability of temperature changes and realistically replicating the freeze-thaw process of natural soil under natural conditions. An image acquisition device 2 and an image sensor are also included. Processing device 4 enables real-time, in-situ, and dynamic monitoring of the migration process of microplastic particles in soil. Through image analysis, it obtains the migration patterns and distribution characteristics of microplastic particles, providing important experimental evidence and theoretical support for revealing the migration changes of microplastic particles in permafrost environments. Furthermore, the simulation monitoring device of this invention can be configured according to the pore structure characteristics of different soils in various regions. In the permafrost structure simulation device 6, parameters such as soil pore structure are set accordingly, and temperature conditions are adjusted according to experimental requirements. This allows for the simulation of microplastic migration behavior under different soil environments and freeze-thaw conditions, and can also simultaneously reflect water migration behavior. In summary, this simulation monitoring device and method possess excellent simulation capabilities and extremely high experimental accuracy. The research results are of great significance for the evaluation and remediation of environmental problems in widely distributed cold regions with contaminated sites. The study of microplastic particle migration in soil freeze-thaw environments, as well as the remediation and control of microplastic pollution in soil, have profound impact and social value. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of a simulation monitoring device for permafrost change processes;

[0036] Figure 2 This is a schematic diagram of the pore structure distribution of the permafrost structure simulation device for the monitoring device. Detailed Implementation

[0037] To make the objectives and technical solutions of this application clearer, the embodiments of this application will be further described and explained in detail below with reference to the accompanying drawings.

[0038] In the following description, when referring to the accompanying drawings, the same numbers in different drawings denote the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0039] The technical solution of a specific embodiment of the present invention is as follows:

[0040] A simulation monitoring device for permafrost change processes includes a constant temperature chamber 1. The constant temperature chamber 1 contains an image acquisition device 2 and a light source 3 arranged opposite to it. The image acquisition device 2 is connected to an image processing device 4. A platform 5 between the image acquisition device 2 and the light source 3 is equipped with a permafrost structure simulation device 6 with high soil simulation accuracy. The permafrost structure simulation device 6 is composed of two layers of light-transmitting structure with multiple protrusions 14 between the two layers. The surface of the protrusions 14 is coated with a coating layer 15. The permafrost structure simulation device 6 has an inlet and an outlet. The permafrost structure simulation device 6 is equipped with a temperature control device 7.

[0041] like Figure 1As shown, the simulation monitoring device for the permafrost change process consists of a constant temperature chamber 1, an image acquisition device 2, a light source 3, an image processing device 4, a stage 5, a permafrost structure simulation device 6, and a temperature control device 7. To avoid the influence of external ambient temperature on the experimental results, the image acquisition device 2, the light source 3, the stage 5, the permafrost structure simulation device 6, and the temperature control device 7 are housed in a sealed and dry constant temperature chamber 1. Throughout the experiment, the temperature of the constant temperature chamber 1 is maintained between 1℃ and 5℃, specifically at 2℃. The image processing device 4 is located outside the constant temperature chamber 1. The permafrost structure simulation device 6 is mounted on the stage 5. The image acquisition device 2 and the light source 3 are positioned above and below the stage 5, respectively. For convenient real-time observation and data acquisition, the image acquisition device 2 is positioned above the stage 5, and the light source 3 is positioned below the stage 5 and located on the bottom surface inside the constant temperature chamber 1. The light source 3 is an LED light source 3. The distance between the light source 3 and the stage 5 is adjusted by changing the height of the stage 5 according to experimental needs. This ensures that the light source 3 provides sufficient illumination for the frozen soil structure simulation device 6 placed on the stage 5, achieving high-definition illumination of the microplastic particles 19 inside the device. Specifically, the distance between the image acquisition device 2 and the stage 5 is set to 4-6 cm, and the distance between the light source 3 and the stage 5 is set to 6-8 cm. The frozen soil structure simulation device 6 has a two-layer structure made of a light-transmitting material, enabling visualization and real-time monitoring of the migration process of microplastic particles in the soil. The frozen soil structure simulation device 6 has multiple protrusions 14 inside, which simulate soil particles. The gaps between the protrusions 14 are interconnected to form microchannels, simulating the pore channels between soil particles, i.e., simulating the migration channels of microplastic particles in the soil. Specifically, 200 cylindrical protrusions 14, each 200 μm in diameter and 15 μm in height, are arranged in a 40*50 horizontal and vertical pattern with 200 μm pore throats within the frozen soil structure simulation device 6. This forms a simulated soil particle structure distribution and interparticle pore channels with a porosity approaching 50%. The surface of each protrusion 14 has a coating layer 15 containing soil mineral components to increase its friction and adsorption capacity, simulating the interaction between microplastic particles and soil particle surfaces. This incorporates the effects of soil particle surfaces on the blocking, adsorption, and release of microplastic particles and other substances in the soil into the simulation experiment, enhancing the simulation accuracy of soil particles and more realistically simulating the migration process of microplastic particles in the soil. The frozen soil structure simulation device 6 has an inlet and an outlet, located at opposite ends of the upper surface of the upper structure, penetrating vertically through the upper structure and extending into the lower structure, for injecting or discharging solutions.The frozen soil structure simulation device 6 is equipped with a temperature control device 7, which controls the cooling and heating of the device to simulate the freezing and thawing process of the soil environment, thus simulating the temperature environment for the migration of microplastic particles 19 in frozen soil. The soil processing device 4 is connected to the image acquisition device 2 wirelessly or via wired connection. The image acquisition device 2 monitors and acquires the overall distribution of multiple protrusions 14 in the frozen soil structure simulation device 6 in real time, obtaining dynamic images of the microplastic particles 19 and transmitting them instantly to the image processing device 4. The image processing device 4 captures and collects images in time segments to obtain dynamic images and data of the migration of microplastic particles in the frozen soil structure simulation device 6. This frozen soil change process simulation monitoring device achieves a high degree of realism in simulating the migration process of microplastic particles in the freeze-thaw soil environment, simulating the influence of soil minerals on the migration behavior of microplastic particles in frozen soil, and greatly improving the simulation, accuracy, and controllability of the microplastic particle migration simulation in frozen soil.

[0042] The frozen soil structure simulation device 6 includes an upper glass layer 12, a lower glass layer 13, and multiple irregular protrusions 14 distributed between the upper glass layer 12 and the lower glass layer 13 according to the soil pore distribution information. There are tiny gaps between the protrusions 14, and a coating layer 15 simulating soil characteristics is provided on the surface of the protrusions 14 and the inner surface of the upper and lower glass layers.

[0043] like Figure 2As shown, the double-layered light-transmitting structure of the permafrost structure simulation device 6 consists of an upper glass layer 12 and a lower glass layer 13. The protrusion 14 is located on the lower surface of the upper glass layer 12, or on the upper surface of the lower glass layer 13, or in the space between the upper glass layer 12 and the lower glass layer 13. The upper glass layer 12 and the lower glass layer 13 are connected and fixed by bonding. In particular, the upper and lower glass layers are made of quartz glass. Quartz glass has high light transmittance, high refractive index, low absorption rate, and low dispersion, which can effectively transmit light and has good transmittance for ultraviolet rays. This is beneficial for observing and collecting the distribution and migration of microplastic particles in the permafrost structure simulation device 6, and facilitates temperature changes and ultraviolet curing processes during experiments. The positional distribution of the multiple protrusions 14 is determined based on the pore distribution structure of natural soil. By analyzing the three-dimensional pore structure of collected natural soil samples, the total porosity in the frozen soil structure simulation device 6 is determined, thereby determining the structure and positional distribution of the protrusions 14 to simulate the distribution structure characteristics of natural soil particles. Furthermore, the multiple protrusions 14 form micro-gaps, which are interconnected to form microchannels simulating the pore channels of natural soil. A coating layer 15 simulating the mineral characteristics of natural soil is applied to the surface of the protrusions 14 and the inner surfaces of the upper and lower glass layers 12 and 13. The mineral composition of this coating layer 15 is determined based on the mineral composition of natural soil. By collecting natural soil samples and performing mineral composition analysis, the main mineral components and proportions in the soil are obtained. The coating layer 15 is prepared based on the obtained components and proportions to simulate the mineral composition of the surface of natural soil particles. Specifically, this embodiment simulates seasonally frozen black soil in the cultivated land area surrounding Shenyang City, Liaoning Province, where the bulk density of the black soil is 0.8~1.5 g / cm³. 3The porosity gradually increases from the surface downwards, with a total porosity of approximately 50%. Based on the porosity characteristics of this black soil sample, multiple protrusions 14 are irregularly arranged on the upper surface of the lower glass layer 13, forming a pore distribution structure on the upper surface of the lower glass layer 13 that matches the average porosity of the natural black soil sample. Since the measured mineral composition of the black soil sample is mainly composed of dolomite, calcite, and mica, dolomite or calcite is selected as the mineral component of the coating layer 15. These minerals are applied to the surface of the protrusions 14 and the inner surfaces of the upper and lower glass layers through coating or other methods to simulate the surface characteristics of soil particles and pore channels in the natural black soil environment. By using the coating layer 15, which simulates the mineral composition of the soil, to simulate the surface of natural soil particles, the simulation depth of factors such as friction and adsorption capacity of natural soil particles is increased. This more realistically and accurately replicates the natural soil environment, restores the role and influence of natural soil particles on the migration behavior of microplastic particles in the permafrost environment, and further improves the realism and reliability of the natural soil simulation. The frozen soil structure simulation device 6 provides a soil structure simulation platform that can study environmental change processes in real soil environments at a microscale. The coating layer 15, which simulates the mineral composition of natural soil, helps to simulate the migration behavior of microplastic particles and other substances in the macroscopic natural soil environment at a smaller microscale. This further improves the simulation of the influence of natural soil particles on the migration behavior of microplastic particles, thereby more accurately reproducing the migration process of microplastic particles in frozen soil and improving the accuracy and realism of the simulation experiment.

[0044] The protrusion 14 is integrally formed with the lower glass layer 13, or the protrusion 14 is integrally formed with the upper glass layer 12, or it is formed by dot-coating.

[0045] In the frozen soil structure simulation device 6, the multiple protrusions 14 can be constructed in various ways, including the following: multiple protrusions 14 are disposed on the lower surface of the upper glass 12 and integrally formed with the upper glass 12, or disposed on the upper surface of the lower glass 13 and integrally formed with the lower glass 13. The above two methods are implemented by photolithography and etching micromachining technology. According to the pore structure data such as the total porosity of the natural soil collected, microchannels with the same pore structure are etched on the lower surface of the upper glass 12 or the upper surface of the lower glass 13, that is, multiple protrusions 14 are formed on the lower surface of the upper glass 12 or the upper surface of the lower glass 13. After the protrusions 14 are formed, a coating layer 15 is disposed on the surface of the protrusions 14 and the inner surface of the upper and lower glass layers. In this embodiment, a photocuring method is used to set the coating layer 15. A photocurable aqueous solution containing soluble minerals, prepared according to the mineral composition of natural soil, is injected into the frozen soil structure simulation device 6 and evenly distributed. After curing with ultraviolet light, deionized water is injected to rinse the uncured aqueous solution, forming a coating layer 15 simulating the mineral composition of natural soil on the surface of the protrusion 14 and the inner surface of the upper and lower glass layers. Alternatively, multiple protrusions 14 are set on the lower surface of the upper glass layer 12 or the upper surface of the lower glass layer 13 in a dot-matrix coating manner. Specifically, the protrusions 14 are made of a viscous material containing soluble minerals, the soluble minerals being determined according to the mineral composition of natural soil. The viscous material composition includes a photoinitiator, a crosslinking agent, soluble minerals, and a thickener. The viscosity of the viscous material is between 500 mPa·s and 1000 mPa·s, exhibiting excellent adsorption capacity with the upper and lower glass layers and being able to bond rapidly under ultraviolet light irradiation. The viscous material, based on the pore structure data of natural soil, is dot-coated onto the upper surface of the lower glass layer 13. After UV curing, multiple protrusions 14 containing natural soil mineral components are formed on the upper surface of the lower glass layer 13 to simulate the particle structure characteristics and distribution of natural soil. After forming the protrusions 14, an aqueous solution containing soluble minerals is photocured to form a coating layer 15 simulating the mineral components of natural soil on the side surfaces of the protrusions 14 and the inner surfaces of the upper and lower glass layers. Through the above dot-coating method, the position and structure of the protrusions 14 can be determined or adjusted according to the pore structure characteristics of natural soil and the actual needs of the experiment, improving the complexity, realism, and controllability of the soil simulation environment. The above-mentioned protrusion 14 formation method is simple, highly reproducible, and provides accurate simulation, obtaining a soil simulation environment with natural soil structure and real mineral components. It can more accurately and realistically simulate the migration behavior of microplastic particles in the soil environment and the influence of soil particles on the migration behavior of microplastic particles, achieving better simulation and modeling effects. Meanwhile, by using various configurations of the protrusion 14, simulations of pore structures in various types of soil can be achieved, thereby improving the practicality and versatility of the simulation experimental device.

[0046] The temperature control device 7 includes a first temperature control device and a second temperature control device, which are located at both ends of the frozen soil structure simulation device 6 and are in contact with the upper and lower surfaces of the frozen soil structure simulation device 6.

[0047] The temperature control device 7 includes a first temperature control device and a second temperature control device. The first and second temperature control devices are respectively disposed at both ends of the frozen soil structure simulation device 6, and are both fitted to the upper and lower surfaces of the frozen soil structure simulation device 6. The first and second temperature control devices are used to control the temperature of the frozen soil structure simulation device 6, so as to achieve stable and precise regulation of the temperature gradient of the frozen soil structure simulation device 6, with an error range within ±0.02℃. The first temperature control device cools one end of the frozen soil structure simulation device 6, while the second temperature control device keeps the temperature of the other end of the frozen soil structure simulation device 6 consistent with and constant the ambient temperature of the constant temperature chamber 1, thus creating a unidirectional freezing process from one end to the other. A controllable temperature gradient is formed between the first and second temperature control devices. In this embodiment, the first temperature control device is located at the left end of the frozen soil structure simulation device 6, causing the aqueous solution containing microplastic particles 19 in the frozen soil structure simulation device 6 to gradually freeze from the left end to the right end, simulating the freezing process of microplastic particles 19 in a natural soil environment. After the microplastic particles 19 have frozen, the temperature of the first temperature control device is adjusted to heat the frozen soil structure simulation device 6, causing the aqueous solution containing microplastic particles 19 to melt completely, simulating the melting process of microplastic particles 19 in a frozen soil environment. The above-mentioned freezing process and melting process constitute a complete freeze-thaw cycle. During this process, the second temperature control device located at the right end of the frozen soil structure simulation device 6 is maintained at 2°C to simulate the ambient temperature of the deep surface of the real soil environment. Specifically, the temperature control device 7 is a semiconductor refrigeration chip. A temperature sensor located inside the semiconductor refrigeration chip, combined with a PID (Proportional-Integral-Derivative Control Algorithm), enables precise temperature control and real-time feedback at both ends of the frozen soil structure simulation device 6. The temperature control range of the first and second temperature control devices is -15℃ to 20℃, with an accuracy of ±0.1℃. By setting the first and second temperature control devices at both ends of the frozen soil structure simulation device 6, the freezing and thawing process of soil under natural conditions is simulated, thereby simulating and real-time monitoring the migration behavior of microplastic particles 19 in the frozen soil environment. The first and second temperature control devices of this technical solution are respectively attached to the upper and lower surfaces of the frozen soil structure simulation device 6, achieving stable temperature conduction and quickly reaching the required freezing and thawing temperatures for the soil environment. This avoids the situation where the temperature control device 7 only contacts a single surface of the frozen soil structure simulation device 6, where slight looseness between the devices can lead to poor contact, preventing the cooling or heating temperature from being smoothly conducted to the frozen soil structure simulation device 6, thus failing to meet experimental requirements, especially the freezing temperature, affecting the final simulation experiment results.

[0048] The image acquisition device 2 includes a camera 10 and an objective lens 11, and the image processing device 4 includes an image acquisition card and a computer.

[0049] The image acquisition device 2 includes a CCD camera 10 and an objective lens 11 located at the bottom of the camera 10. The objective lens 11 is used to collect light emitted from the light source 3 and focus the light onto the stage 5, thereby achieving magnified imaging of the microplastic particles 19 inside the frozen soil structure simulation device 6 on the stage 5. This, together with the CCD camera 10, enables real-time imaging and monitoring of the migration process of the microplastic particles 19 inside the frozen soil structure simulation device 6. The image processing device 4 includes an image acquisition card and a computer. The image acquisition card is used to acquire images of the microplastic particles 19 output by the CCD camera 10 in real time and transmit them to the computer for storage and analysis. The computer performs noise reduction, enhancement, and segmentation processing on the acquired images of the microplastic particles 19, and extracts features such as the morphology, size, and quantity of the microplastic particles 19 for microplastic migration analysis and research.

[0050] The coating layer 15 is composed of the following components by weight percentage: crosslinking agent: 0.5%-5%; photoinitiator: 0.01%-0.1%; soluble minerals: 2%-10%; thickener: 0%-2%; the remainder is deionized water, and the total of all components is 100%.

[0051] The coating layer 15 is composed of a crosslinking agent, a photoinitiator, soluble minerals, and a thickener. By weight percentage, the crosslinking agent is 0.5%-5%, the photoinitiator is 0.01%-0.1%, the soluble minerals are 2%-85%, and the thickener is 0%-2%. Specifically, for the configuration where the protrusion 14 is integrally formed with the upper glass layer 12 or the lower glass layer 13, the coating layer 15 comprises 0.5%-5% crosslinking agent, 0.01%-0.1% photoinitiator, and 2%-20% soluble minerals, with the remainder being deionized water, and the total composition is 100%. For the method of forming the protrusion 14 by dot coating, the protrusion 14 is made of a viscous material containing soluble minerals. The surface of the formed protrusion 14 is a coating layer 15 containing mineral components that simulates the characteristics of soil. The composition of the viscous material includes 2.5%-5% crosslinking agent, 0.01%-0.1% photoinitiator, 15%-85% soluble minerals and 0.5%-2% thickener, with the remainder being deionized water. The total of all components is 100%. After the protrusion 14 is formed by dot coating, a photocurable aqueous solution containing soluble minerals is prepared to form the coating layer 15 on the upper and lower glass layers 13. The composition of this coating layer 15 is 0.5%-3% crosslinking agent, 0.01%-0.1% photoinitiator and 2%-10% soluble minerals, with the remainder being deionized water. The total of all components is 100%.

[0052] Specifically, this embodiment simulates the seasonally frozen black soil around Shenyang City, Liaoning Province. Ethylene glycol dimethacrylate is selected as the crosslinking agent, benzophenone as the photoinitiator, dolomite, calcite, or mica as the soluble minerals, and carboxymethyl cellulose as the thickener. By weight percentage, in the configuration where the protrusion 14 is integrally formed with the upper glass 12 or the lower glass 13, the coating layer 15 comprises 0.5% crosslinking agent, 0.1% photoinitiator, and 15% soluble minerals, with the remainder being deionized water, totaling 100%. In the method of forming the protrusion 14 by dot-coating, the viscous material containing soluble minerals is composed of 5% crosslinking agent, 0.05% photoinitiator, 65% soluble minerals, and 2% thickener, with the remainder being deionized water, and the total of all components being 100%. After forming the protrusion 14 by dot-coating, the coating layer 15 formed by preparing a photocurable aqueous solution containing soluble minerals on the upper and lower glass layers 13 is composed of 0.5% crosslinking agent, 0.05% photoinitiator, and 5% soluble minerals, with the remainder being deionized water, and the total of all components being 100%. By forming the coating layer 15 containing soluble minerals through various methods, the soluble mineral factor is introduced to simulate natural soil particles, resulting in a frozen soil structure simulation device 6 with the distribution of natural soil pore structure and mineral composition. This allows for in-depth research into the influence and role of soil particles on the migration behavior of microplastic particles 19, and better simulation of the migration process of microplastic particles 19 in soil pores under freeze-thaw conditions.

[0053] The method for simulating and monitoring frozen soil using the aforementioned permafrost change process simulation monitoring device includes the following steps:

[0054] 1) Prepare an aqueous solution containing microplastic particles 19;

[0055] 2) Inject the aqueous solution containing microplastic particles into the inlet of the frozen soil structure simulation device 6 to fill the interior of the frozen soil structure simulation device 6. Place the frozen soil structure simulation device 6 in the constant temperature chamber 1 and adjust the temperature of the constant temperature chamber 1 and the temperature control device 7 to 1℃~5℃. Let it stand for 10~15 minutes to make the aqueous solution of microplastic particles evenly distributed in the frozen soil structure simulation device 6, and capture the initial distribution state of microplastic particles in the soil pores. During this period, the temperature of the constant temperature chamber 1 and the temperature control device 7 remains consistent.

[0056] 3) After the temperature inside the frozen soil structure simulation device 6 reaches a stable state, the temperature control device 7 lowers the temperature, and one end of the frozen soil structure simulation device 6 is cooled down to below 0°C, while the other end remains at the same temperature as the constant temperature chamber 1, so that the aqueous solution containing microplastic particles freezes unidirectionally from the cold end to the warm end until the aqueous solution freezes and the state is stable.

[0057] 4) Temperature control device 7 raises the temperature, starting from one end of frozen soil structure simulation device 6, so that the frozen aqueous solution containing microplastic particles gradually melts until the aqueous solution is completely liquid.

[0058] The process of steps 2)-4) above is recorded. Among them, one freezing process and one thawing process in 3) and 4) constitute one freeze-thaw cycle.

[0059] Extract and process image information from the video recordings of the above processes.

[0060] In the method of simulating and monitoring frozen soil using a frozen soil change simulation monitoring device, firstly, microplastic particles 19 with a diameter in the range of 1μm-5mm are selected and dispersed in deionized water and mixed evenly to prepare an aqueous solution containing microplastic particles 19 with a mass concentration of 0.05%-0.3%. Secondly, the prepared aqueous solution containing microplastic particles 19 is slowly injected into the frozen soil structure simulation device 6 through the inlet until it fills the entire area where the protrusions 14 are distributed in the frozen soil structure simulation device 6. The frozen soil structure simulation device 6 containing the aqueous solution containing microplastic particles is then transferred to a constant temperature chamber 1. The temperature of the constant temperature chamber 1 and the second temperature control device are adjusted to 1℃~5℃. In particular, the temperature of the constant temperature chamber 1 and the second temperature control device are adjusted. The temperature of the control devices is set to 2℃. After standing for 15 minutes, the aqueous solution of microplastic particles is evenly distributed inside the frozen soil structure simulation device 6. This state is the initial distribution state of the simulated microplastic particles 19 in the soil pores. At this time, the image acquisition device 2 is used to collect the overall distribution image of the microplastic particles 19. Then, the first temperature control device at the left end of the frozen soil structure simulation device 6 is turned on to start cooling, so that one end of the frozen soil structure simulation device 6 gradually cools down to the other end, simulating the unidirectional freezing process of the soil in the seasonal frozen soil area from the shallow surface to the deep surface. The aqueous solution containing microplastic particles 19 freezes unidirectionally from the cold end to the warm end as the temperature drops unidirectionally, until the frozen state of the aqueous solution containing microplastic particles 19 is stable. In the initial freezing stage, image acquisition device 2 captures an image of the overall distribution of microplastic particles 19 within the frozen soil structure simulation device 6 every 5-15 seconds. After the microplastic particles 19 are completely frozen until the freezing front stabilizes, image acquisition device 2 captures an image of the overall distribution of microplastic particles 19 every 2-5 minutes. In the fourth step, after the soil freezing process is completed and the soil has been left to stand for 3-5 minutes, the first temperature control device on the left end of the temperature control device 6 is adjusted to raise its temperature, causing the frozen aqueous solution in device 6 to gradually melt until the aqueous solution is completely liquid. During this process, an image of the overall distribution of microplastic particles 19 is captured every 5-15 seconds. After the aqueous solution containing microplastic particles 19 has completely melted until the melting front stabilizes, an image of the overall distribution of microplastic particles 19 is captured every 2-5 minutes. The overall distribution image; the fifth step is that the image acquired by the image acquisition device 2 is transmitted to the image processing device 4 in real time. The computer of the image processing device 4 extracts images from the acquired images based on the initial distribution state, freezing process and melting process of the microplastic particles 19. The acquired images are preprocessed by denoising, enhancement and segmentation. Then, the microplastic particles 19 in the image are identified and located to obtain the position coordinate information of the microplastic particles 19. Based on the position changes of the microplastic particles 19 in the time series image, the migration trajectory of the microplastic particles 19 in the soil pores is reconstructed. The size, shape, migration speed and migration distance of the microplastic particles 19 are extracted and statistically analyzed. The analysis results are used to create intuitive illustrations such as the trajectory of the microplastic particles 19 and migration heat map.Simultaneously, the physicochemical properties of the microplastic particles 19 after freeze-thaw cycles can be studied. After the freeze-thaw process, the microplastic particles 19 in the frozen soil structure simulation device 6 are washed out with deionized water, and their physicochemical properties are characterized using techniques such as scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Analysis of the image data from this experiment shows that as the soil temperature decreases, the aqueous solution of microplastic particles 19 in the frozen soil structure simulation device 6 gradually freezes and solidifies. Due to the solidification of water into ice, the volume increases, causing the microplastic particles 19 to migrate and redistribute under the pressure of the ice crystals, exhibiting a tendency to aggregate towards the center and lower part of the microchannels in the frozen soil structure simulation device 6. Subsequently, during the heating process controlled by the second temperature control device, the ice crystals gradually melt. As the temperature continues to rise, the microplastic particles 19 migrate further with the flow of the solution, exhibiting a tendency to diffuse towards the upper part and sides of the microchannels in the frozen soil structure simulation device 6. The simulation monitoring method of this invention can more accurately and realistically reproduce the migration environment of microplastic particles in natural soil. It can comprehensively observe and analyze the complex migration behavior of microplastic particles in the soil environment under freeze-thaw conditions, improve the simulation and dynamic monitoring capabilities, and provide better experimental means for related research.

[0061] During the simulation monitoring process, before step 2), images of the original state of the upper and lower glass and images of the upper and lower glass covered with soluble minerals before the injection of the microplastic aqueous solution are collected.

[0062] To further improve the precision and accuracy of the experiment, real-time status data of microplastic particles 19 were collected at different stages of the simulation process to achieve a more accurate and comprehensive simulation experiment effect. At the beginning of the simulation experiment, images of the original state of the upper and lower glass layers 12 and 13 before the soluble mineral coating layer 15 was applied, and images of the upper and lower glass layers 12 and 13 before the injection of the aqueous solution containing microplastic particles 19 with the soluble mineral coating were collected. After the injection of the aqueous solution containing microplastic particles 19, images of the stable distribution of the aqueous solution containing microplastic particles 19 in the frozen soil structure simulation device 6 were collected. During the freezing and thawing stages, images of the early stage of freezing or thawing and images of the stable stage of freezing or thawing were collected. In the early stage of freezing, the image acquisition device 2 collected an image of the overall distribution of microplastic particles 19 in the frozen soil structure simulation device 6 every 10 seconds. After the microplastic particles 19 were completely frozen until the freezing front stabilized, the image acquisition device 2 collected an image of the overall distribution of microplastic particles 19 every 3 minutes. After the freezing process was completed, in the early stage of thawing of microplastic particles 19, the overall distribution of microplastic particles 19 was collected every 10 seconds. After the aqueous solution containing microplastic particles 19 was completely thawed until the thawing front stabilized, the overall distribution of microplastic particles 19 was collected every 3 minutes. In this technical solution, the upper and lower glass layers 12 and 13 are made of quartz glass. Quartz glass has excellent properties in terms of light transmittance, refractive index, and absorptivity. However, it still has certain error effects on the observation and data acquisition of the migration simulation process of microplastic particles 19. Therefore, images of the upper and lower glass layers 12 and 13 in their original state before being coated with soluble minerals are collected. This is mainly used to study and analyze the influence of the glass structure itself on light transmission, absorption, and refraction, as well as the influence of the glass's reflectivity on visual clarity. In the later processing of experimental images, the above-mentioned influencing factors can be eliminated to correct the errors caused by the glass itself in the experimental data. Image information of the upper and lower glass layers 12 and 13 coated with soluble minerals before the injection of aqueous solution containing microplastic particles 19 is collected. This is used to analyze the error caused by the uneven thickness of the soluble mineral coating layer 15 on the simulation of the migration behavior of microplastic particles 19. By analyzing and correcting the error caused by the uneven thickness of the coating layer 15, the accuracy and simulation of the experiment can be further improved. Image information of the stable liquid distribution of aqueous solution containing microplastic particles 19 in frozen soil structure simulation device 6, as well as image information before freezing or thawing and image information after freezing or thawing stabilization, are collected in real time to monitor the distribution and migration behavior of microplastic particles under normal soil temperature and temperature change conditions, and then simulate and analyze the migration trajectory and migration behavior characteristics of microplastic particles in natural freeze-thaw soil environment.

[0063] Specifically, in the simulation monitoring method of this technical solution, the soil environment of farmland around Shenyang City, Liaoning Province is simulated. Polyethylene microplastic particles 19 with a diameter of 5~100μm are selected and mixed with deionized water to prepare an aqueous solution containing microplastic particles 19. The mass concentration of the prepared aqueous solution containing microplastic particles 19 is 0.05%-0.3%. In particular, based on the total concentration range of microplastics in black soil of farmland around Shenyang being 217.30~2512.18μg / g, with an average total concentration of 1327.69μg / g, an aqueous solution containing microplastic particles with a mass concentration of 0.15% is prepared to simulate the migration process and migration trajectory of microplastic particles in freeze-thawed soil in the actual sampling area's black soil environment, so as to further study the migration path of microplastic particles, etc.

Claims

1. A simulation monitoring device for permafrost change processes, comprising a constant temperature chamber (1), wherein the constant temperature chamber (1) has an image acquisition device (2) and a light source (3) arranged opposite to it, the image acquisition device (2) being connected to an image processing device (4), characterized in that, The platform between the image capturing device (2) and the light source (3) is equipped with a frozen soil structure simulation device (6) with high soil simulation accuracy. The frozen soil structure simulation device (6) consists of two layers of light-transmitting structure with multiple protrusions (14) between the two layers. The surface of the protrusions (14) has a coating layer (15). The frozen soil structure simulation device (6) has an inlet and an outlet. The frozen soil structure simulation device (6) is equipped with a temperature control device (7). The coating layer (15) has the following composition by weight percentage: Crosslinking agent 0.5%-5%; Photoinitiator 0.01%-0.1%; Soluble minerals: 2%-85%; Thickener 0%-2%; The remainder is deionized water, and the total of all components is 100%. The frozen soil structure simulation device (6) includes an upper glass (12), a lower glass (13), and multiple irregular protrusions (14) distributed between the upper glass (12) and the lower glass (13) according to the soil pore distribution information. There are tiny gaps between the protrusions (14), and a coating layer (15) simulating soil characteristics is provided on the surface of the protrusions (14) and the inner surface of the upper and lower glass. The protrusion (14) is formed by dot-matrix coating; The protrusion (14) is made of a viscous material containing soluble minerals, the soluble minerals being determined based on the composition of natural soil minerals. The viscous material components include a photoinitiator, a crosslinking agent, soluble minerals, and a thickener. The viscosity of the viscous material is between 500 mPa·s and 1000 mPa·s.

2. The simulation monitoring device for permafrost change process according to claim 1, characterized in that, The temperature control device (7) includes a first temperature control device and a second temperature control device, located at both ends of the frozen soil structure simulation device (6) and in contact with the upper and lower surfaces of the frozen soil structure simulation device (6).

3. The simulation monitoring device for permafrost change process according to claim 2, characterized in that, The image capturing device (2) includes a camera (10) and an objective lens (11), and the image processing device (4) includes an image acquisition card and a computer.

4. The simulation monitoring device for permafrost change process according to claim 3, characterized in that... The coating layer (15) has the following composition by weight percentage: Ethylene glycol dimethacrylate 0.5%-5%; Benzyl ketone 0.01%-0.1%; Dolomite, calcite, or mica 2%-85%; Carboxymethyl cellulose 0%-2%; The remainder is deionized water, and the total of all components is 100%.

5. A method for simulating and monitoring frozen soil using the simulation monitoring device for frozen soil change processes according to any one of claims 1 to 4, characterized in that, Includes the following steps: 1) Prepare an aqueous solution containing microplastic particles; 2) Inject the aqueous solution containing microplastic particles into the inlet of the frozen soil structure simulation device (6) to fill the interior of the frozen soil structure simulation device (6). Place the frozen soil structure simulation device (6) in the constant temperature chamber (1), adjust the temperature of the constant temperature chamber (1) and the temperature control device (7) to 1℃~5℃, and let it stand for 10~15 minutes to make the aqueous solution of microplastic particles evenly distributed in the frozen soil structure simulation device (6) to capture the initial distribution state of microplastic particles in the soil pores. During this period, the temperature of the constant temperature chamber (1) and the temperature control device (7) remains consistent. 3) After the temperature inside the frozen soil structure simulation device (6) reaches stability, the temperature control device (7) lowers the temperature, and one end of the frozen soil structure simulation device (6) is cooled down to below 0℃, while the other end remains at the same temperature as the constant temperature box (1), so that the aqueous solution containing microplastic particles freezes unidirectionally from the cold end to the warm end until the aqueous solution freezes and the state is stable. 4) Temperature control device (7) The temperature rises from one end of the frozen soil structure simulation device (6) to gradually melt the frozen aqueous solution containing microplastic particles until the aqueous solution is completely liquid. The process of steps 2) to 4) above shall be recorded; 5) Extract and process image information from the video recordings of the above processes.

6. The simulation monitoring method according to claim 5, characterized in that, During the simulation monitoring process, before step 2, images of the original state of the upper and lower glass and images of the upper and lower glass covered with mineral particles before the injection of the microplastic aqueous solution were collected.

7. The simulation monitoring method according to claim 6, characterized in that, The method for preparing the aqueous solution containing microplastic particles in step 1) includes: selecting polyethylene microplastic particles with a diameter in the range of 5~100μm, adding the microplastics to deionized water, and preparing an aqueous solution containing microplastic particles with a mass concentration of 0.05%-0.3%.

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