Simulation monitoring device and method for frozen soil change process

Abstract

The invention relates to a simulation monitoring device and method for a frozen soil change process. The simulation monitoring device comprises a constant temperature box, an image shooting device, a light source, an objective table, a frozen soil structure simulation device and a temperature control device are arranged in the constant temperature box, the light source is arranged opposite to the image shooting device, the frozen soil structure simulation device and the temperature control device are arranged on the objective table, and an image processing device is arranged outside the constant temperature box. The frozen soil structure simulation device is used for simulating soil pore structure characteristics by arranging a plurality of convex parts and arranging coating layers on the convex parts, and constructing a high-simulation natural soil simulation environment, pore characteristics of natural soil in a high-reduction freeze-thaw environment and a migration environment of soil pollutants. The simulation monitoring method realizes simulation and monitoring of the migration behavior of the micro-plastic particles in the soil, has excellent simulation performance and extremely high experimental precision, and is of great significance to evaluation and treatment of pollution site environmental problems in widely distributed cold regions.

Description

Technical Field

[0001] The present invention relates to the field of microplastic migration, and in particular to a simulation monitoring device and method for frozen soil change processes. Background Art

[0002] Microplastics, as an emerging pollutant, have attracted widespread global attention in recent years. Agricultural activities, such as mulching, wastewater irrigation, and the application of organic fertilizers or sewage sludge, can lead to the unavoidable introduction of microplastic particles into farmland soils. Notably, freeze-thaw cycles induced by temperature fluctuations significantly influence the distribution and migration of microplastics. Therefore, studying the migration behavior of microplastics within soil pores during freeze-thaw processes is of great practical significance.

[0003] Currently, research on the effects of freeze-thaw on the migration of microplastics primarily focuses on exploring how freeze-thaw-induced changes in the physical and chemical properties of microplastic particles and soil alter the migration process. These experiments typically begin with freeze-thaw pretreatment of the microplastics or soil, followed by a microplastic migration column experiment at room temperature. The migration of microplastics in soil is investigated by comparing the concentrations of microplastics in the influent and effluent water. Related patent applications include CN109975511A, an experimental device and method for simulating the migration of microplastics in soil; CN116223307A, a microplastic migration simulation device; and CN117169060A, an experimental device and method for simulating the migration of microplastics in soil. These patent applications offer the advantage of simulating the migration of microplastics in soil under natural conditions, with relatively simple theoretical approaches and easy implementation. However, the migration of microplastics in these methods is conducted at room temperature, without considering the migration behavior of microplastics within soil pores during freeze-thaw. Therefore, a device and method for simulating the migration of microplastics in natural soil freeze-thaw conditions is needed. Summary of the Invention

[0004] The first technical problem to be solved by the present invention is to provide a simulation monitoring device for the migration of microplastic particles during soil freezing and thawing, which has a simple structure and can highly restore the soil freezing and thawing environment.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A simulation monitoring device for a frozen soil change process includes a constant temperature box 1, which has an image pickup device 2 and a light source 3 arranged opposite to each other. The image pickup device 2 is connected to an image processing device 4. A stage between the image pickup device 2 and the light source 3 is provided with a frozen soil structure simulation device 6 with a high degree of soil simulation. The frozen soil structure simulation device 6 is composed of two layers of light-transmitting structures, 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 is provided with an inlet and an outlet. The frozen soil structure simulation device 6 is provided with a temperature control device 7.

[0007] Furthermore, the frozen soil structure simulation device 6 includes an upper layer of glass 12, a lower layer of glass 13, and a plurality of irregular protrusions 14 distributed between the upper layer of glass 12 and the lower layer of glass 13 according to 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 surfaces of the upper and lower glasses.

[0008] Furthermore, the convex portion 14 is integrally formed with the lower layer of glass 13, or the convex portion 14 is integrally formed with the upper layer of glass 12, or is formed by point coating.

[0009] Furthermore, 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.

[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 coating layer 15 is composed of the following components by weight:

[0012] Cross-linking agent 0.5%-5%;

[0013] Photoinitiator 0.01%-0.1%;

[0014] Soluble minerals 2%-85%;

[0015] Thickener 0%-2%;

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

[0017] Furthermore, the coating layer 15 is composed of the following components by weight:

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

[0019] Benzophenone 0.01%-0.1%;

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

[0021] Carboxymethyl cellulose 0%-2%;

[0022] The rest is deionized water, and the sum 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 the freezing and thawing process, so as to realize accurate, efficient and real-time monitoring of the migration and distribution of microplastic particles in soil pores during the freezing and thawing process.

[0024] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0025] The method for simulating and monitoring frozen soil by the device for simulating and monitoring frozen soil change process comprises the following steps:

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

[0027] 2) Injecting an aqueous solution containing microplastic particles through the inlet of the frozen soil structure simulation device 6 so that the aqueous solution of microplastic particles fills the interior of the frozen soil structure simulation device 6, placing the frozen soil structure simulation device 6 in a constant temperature box 1, adjusting the temperature of the constant temperature box 1 and the temperature control device 7 to 1°C to 5°C, and letting it stand for 10 to 15 minutes to evenly distribute the aqueous solution of microplastic particles in the frozen soil structure simulation device 6, and to obtain the initial distribution state of the microplastic particles in the soil pores. During this period of time, the temperature of the constant temperature box 1 and the temperature control device 7 remain consistent;

[0028] 3) After the temperature inside the frozen soil structure simulation device 6 reaches stability, the temperature of the temperature control device 7 is lowered, and one end of the frozen soil structure simulation device 6 begins to be cooled to below 0°C, while the temperature of the other end is always kept consistent with the temperature of the constant temperature box 1, so that the aqueous solution containing microplastic particles is frozen unidirectionally from the cold end to the warm end until the frozen state of the aqueous solution is stable;

[0029] 4) The temperature of the temperature control device 7 is increased, starting from one end of the 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] Video record the process of steps 2)-4) above;

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

[0032] Furthermore, during the simulated monitoring process, before step 2, images of the upper and lower glasses in their original states and image information of the upper and lower glasses covered with mineral particles before the microplastic-containing aqueous solution was injected were collected.

[0033] Furthermore, 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 to 100 μm, adding the above microplastics to deionized water, and preparing an aqueous solution containing microplastic particles with a mass concentration of 0.05%-0.3%.

[0034] Through the technical solution of the present invention, a simulation monitoring device and method for the migration of microplastic particles in the pores of frozen soil with high simulation, high restoration of the natural soil environment and good controllability is constructed. At the same time, after there are no microplastic particles in the water, markers can be set to reflect the state changes of the water during the freezing, melting and flow of the water. In particular, by simulating the pore structure distribution of natural soil and simulating the mineral composition of the surface of natural soil particles, the natural soil environment is restored and replicated in the frozen soil structure simulation device 6, which greatly improves the degree of simulation of the natural soil environment, and achieves a high degree of restoration and accurate simulation of the distribution state and migration behavior of microplastic particles in the soil pores, so that the simulation experiment achieves high simulation and high simulation accuracy; by fitting the temperature control device 7 at both ends of the frozen soil structure simulation device 6, the ambient temperature can be finely controlled to ensure the stability of the temperature change and truly restore the freezing and thawing process of natural soil under natural conditions; by setting the image capture device 2 and the image The processing device 4 realizes real-time, in-situ, dynamic monitoring of the migration process of microplastic particles in the soil, and obtains the migration law and distribution characteristics of microplastic particles through image analysis, which provides important experimental basis and theoretical support for revealing the migration changes of microplastic particles in frozen soil environments. In addition, the simulation monitoring device of the present invention can set the pore structure and other parameters of the soil in the frozen soil structure simulation device 6 according to the pore characteristic structure of different soils in various regions, and adjust the temperature conditions according to the experimental requirements, thereby simulating the migration behavior of microplastics in different soil environments and freeze-thaw conditions, and can also synchronously reflect the migration behavior of water. In summary, the simulation monitoring device and method have excellent simulation and extremely high experimental accuracy. The research results are of great significance to the evaluation and treatment of environmental problems of contaminated sites in widely distributed cold regions, and have far-reaching influence and social value on the study of the migration of microplastic particles in soil freeze-thaw environments and the treatment and prevention and control of microplastic pollution problems in soil. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0036] Figure 2 Schematic diagram of the pore structure distribution of the frozen soil structure simulation device that simulates the monitoring device. DETAILED DESCRIPTION

[0037] In order to make the purpose and technical solution of the present application clearer, the embodiments of the present application will be further described and explained in detail with reference to the accompanying drawings.

[0038] When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. Instead, they are merely devices and methods consistent with certain aspects of the present application as detailed in the appended claims.

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

[0040] A simulation monitoring device for a frozen soil change process includes a constant temperature box 1, which has an image pickup device 2 and a light source 3 arranged opposite to each other. The image pickup device 2 is connected to an image processing device 4. A stage 5 between the image pickup device 2 and the light source 3 is provided with a frozen soil structure simulation device 6 with a high degree of soil simulation. The frozen soil structure simulation device 6 is composed of two layers of light-transmitting structures, with multiple protrusions 14 between the two layers. A coating layer 15 is provided on the surface of the protrusions 14. The frozen soil structure simulation device 6 is provided with an inlet and an outlet. The frozen soil structure simulation device 6 is provided with a temperature control device 7.

[0041] like Figure 1As shown, the simulated monitoring device for frozen soil changes consists of a constant temperature chamber 1, an image capture device 2, a light source 3, an image processing device 4, a stage 5, a frozen soil structure simulator 6, and a temperature control device 7. To prevent the influence of external ambient temperature on the experimental results, the image capture device 2, light source 3, stage 5, frozen soil structure simulator 6, and temperature control device 7 were placed in a sealed and dry constant temperature chamber 1. The temperature of the constant temperature chamber 1 was maintained between 1°C and 5°C throughout the experiment, specifically at 2°C. The image processing device 4 was placed outside the constant temperature chamber 1. The frozen soil structure simulator 6 was placed on the stage 5, while the image capture device 2 and light source 3 were located above and below the stage 5, respectively. To facilitate real-time observation and data acquisition, the image capture device 2 was placed above the stage 5, and the light source 3 was placed below the stage 5 and on the inner bottom surface of the constant temperature chamber 1. The light source 3 was an LED. The distance between the light source 3 and the loading platform 5 is adjusted by adjusting the height of the loading platform 5 according to the experimental needs to ensure that the light source 3 provides sufficient light for the frozen soil structure simulation device 6 placed on the loading platform 5 to meet the high-definition illumination of the microplastic particles 19 inside the frozen soil structure simulation device 6. In particular, the distance between the image capture device 2 and the loading platform 5 is set to 4-6cm, and the distance between the light source 3 and the loading platform 5 is 6-8cm. The frozen soil structure simulation device 6 has an upper and lower two-layer structure, and the two-layer structure is made of a material with good light transmittance to achieve visualization and real-time monitoring of the migration process of microplastic particles in the soil. A plurality of protrusions 14 are provided inside the frozen soil structure simulation device 6, and the protrusions 14 are used to simulate soil particles. The gaps between the protrusions 14 are interconnected to form microchannels, simulating the pore channels between the soil particles, that is, simulating the migration channels of microplastic particles in the soil. Specifically, 200 cylindrical protrusions 14 with a diameter of 200 μm and a height of 15 μm were arranged in a 40×50 horizontal and vertical pattern with 200 μm pore throats within the frozen soil structure simulator 6. This simulated soil particle structure distribution with a porosity close to 50% and intergranular pore channels was formed. The protrusions 14 were coated with a coating 15 containing soil mineral components to increase friction and adsorption capacity on the surface of the protrusions 14, simulating the interaction between microplastic particles and the soil particle surface. Factors such as the soil particle surface's ability to intercept, adsorb, and release microplastic particles and other substances in the soil were factored into the simulation experiment, enhancing the simulation of soil particles and more realistically simulating the migration process of microplastic particles in soil, allowing for the study of the influence of soil particles on their migration behavior. The frozen soil structure simulator 6 was equipped with an inlet and an outlet, located at either end of the upper surface of the superstructure, extending vertically through the superstructure and into the interior of the lower structure for the injection or discharge of solutions.The frozen soil structure simulator 6 is equipped with a temperature control device 7, which cools and heats the frozen soil structure simulator 6, simulating the freezing and thawing processes of the soil environment and the temperature environment of the microplastic particles 19 during the migration of frozen soil. The soil processing device 4 is connected to the image capture device 2 via a wireless or wired connection. The image capture device 2 monitors and captures the overall distribution of the multiple protrusions 14 in the frozen soil structure simulator 6 in real time, obtains an overall dynamic image of the microplastic particles 19 in the frozen soil structure simulator 6, and instantly transmits it to the image processing device 4. The image processing device 4 captures and collects the captured image by time period to obtain dynamic images and data of the migration of microplastic particles in the frozen soil structure simulator 6. The simulated monitoring device for the frozen soil change process achieves a highly realistic simulation of 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 the frozen soil environment, greatly improving the simulation, accuracy, and controllability of the migration of microplastic particles in frozen soil.

[0042] The frozen soil structure simulation device 6 includes an upper layer of glass 12, a lower layer of glass 13, and a plurality of irregular protrusions 14 distributed between the upper and lower layers of glass 12, 13 according to 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 surfaces of the upper and lower glasses.

[0043] like Figure 2As shown, the double-layer light-transmitting structure of the frozen soil structure simulation device 6 comprises an upper layer of glass 12 and a lower layer of glass 13. The protrusion 14 is provided on the lower surface of the upper layer of glass 12, or on the upper surface of the lower layer of glass 13, or in the space between the upper and lower layers of glass 12, 13. The upper and lower layers of glass 12, 13 are connected and fixed by bonding. In particular, the upper and lower layers of glass are made of quartz glass, which has high light transmittance, high refractive index, low absorption rate, and low dispersion. It can effectively transmit light and has good transmittance to ultraviolet rays. This facilitates the observation and collection of the distribution and migration of microplastic particles in the frozen soil structure simulation device 6, and facilitates the temperature changes and ultraviolet curing process during the experiment. The positional distribution of the multiple protrusions 14 is determined based on the pore distribution structure of natural soil. The total porosity in the frozen soil structure simulation device 6 is determined by the three-dimensional pore structure of the collected natural soil samples. The structure and positional distribution of the protrusions 14 are thus determined to simulate the distribution structural characteristics of natural soil particles. Micro-gaps are formed between the multiple protrusions 14, and the gaps are interconnected and connected to form microchannels that simulate the pore channels of natural soil. A coating 15 simulating the mineral characteristics of natural soil is applied to the surfaces of the protrusions 14 and the inner surfaces of the upper and lower glass layers 12 and 13. The mineral composition of the coating 15 is determined based on the mineral composition of natural soil. Natural soil samples are collected and analyzed for their mineral composition to obtain the main mineral components and proportions in the soil. The coating 15 is prepared based on the obtained components and proportions, achieving a simulation of 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. The black soil in this area has a bulk density of 0.8-1.5 g / cm3. 3The porosity gradually increases from the surface downward, reaching a total porosity of approximately 50%. Based on the pore characteristics of the black soil sample, multiple protrusions 14 are provided on the upper surface of the lower glass 13. These protrusions 14 are irregularly arranged, forming a pore distribution structure on the upper surface of the lower glass 13 with the same average porosity as the natural black soil sample. Based on the measured mineral composition of the black soil sample, which is primarily 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 surfaces of the protrusions 14 and the inner surfaces of the upper and lower glass layers through coating or other means to simulate the surface characteristics of soil particles and pore channels in a natural black soil environment. Using the coating layer 15 with simulated soil mineral composition to simulate the surface of natural soil particles, the friction and adsorption capacity of natural soil particles are further simulated, more realistically and accurately replicating the natural soil environment and restoring the effects and influences of natural soil particles on the migration behavior of microplastic particles in frozen soil environments, further improving the authenticity and reliability of the natural soil simulation. The frozen soil structure simulation device 6 provides a soil structure simulation platform that can study the environmental change process in the real soil environment at the microscopic scale. The coating layer 15 that simulates the mineral composition of natural soil is more helpful in simulating the migration behavior of substances such as microplastic particles in the macroscopic natural soil environment at a smaller microscopic scale, further improving the degree of simulation of the influence of natural soil particles on the migration behavior of microplastic particles, thereby more accurately restoring the migration process of microplastic particles in frozen soil and improving the accuracy and authenticity of the simulation experiment.

[0044] The convex portion 14 is formed integrally with the lower glass 13, or the convex portion 14 is formed integrally with the upper glass 12, or is formed by point coating.

[0045] In the frozen soil structure simulation device 6, the multiple protrusions 14 can be constructed in a variety of ways, including the following: the multiple protrusions 14 are arranged on the lower surface of the upper glass 12 and are integrally formed with the upper glass 12, or are arranged on the upper surface of the lower glass 13 and are integrally formed with the lower glass 13. The above two methods are implemented using 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 provided on the surface of the protrusions 14 and the inner surfaces of the upper and lower glass layers. In this embodiment, a coating layer 15 is formed by photocuring. A photocurable aqueous solution containing soluble minerals prepared based on 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 protrusions 14 and the inner surface of the upper and lower glass layers. Alternatively, multiple protrusions 14 are provided in a dot-coating manner on the lower surface of the upper glass layer 12 or the upper surface of the lower glass layer 13. Specifically, the protrusions 14 are made of a viscous material containing soluble minerals. The soluble minerals are determined based on the mineral composition of natural soil. The viscous material comprises a photoinitiator, a crosslinker, a soluble mineral, and a thickener. The viscous material has a viscosity of 500 mPa·s to 1000 mPa·s, exhibits excellent adsorption properties with the upper and lower glass layers, and can be quickly bonded under ultraviolet light. This viscous material is dot-coated on the upper surface of the lower glass 13 according to the pore structure data of natural soil. After UV curing, multiple protrusions 14 containing natural soil mineral components are formed on the upper surface of the lower glass 13 to simulate the structural characteristics and distribution of natural soil particles. After the protrusions 14 are dot-coated, 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 this dot-coating method, the position, distribution, 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, thereby improving the complexity, realism, and controllability of the soil simulation environment. The formation method of the protrusions 14 is simple, highly resilient, and accurately simulates the soil simulation environment, resulting in a soil simulation environment with natural soil structure and realistic mineral components. This allows for more accurate and realistic simulation of 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 emulation results. At the same time, through various settings of the convex portion 14, simulation and emulation of various types of soil pore structures 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 respectively located at two 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.

[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 arranged at both ends of the frozen soil structure simulation device 6 and are both arranged in contact with 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, achieving stable and precise control of the temperature gradient of the frozen soil structure simulation device 6, with an error range of ±0.02°C. One end of the frozen soil structure simulation device 6 is refrigerated by the first temperature control device, and the second temperature control device controls the temperature of the other end of the frozen soil structure simulation device 6 to be consistent with the ambient temperature of the constant temperature box 1 and remains unchanged, resulting in a unidirectional freezing process from one end to the other end of the frozen soil structure simulation device 6, and a controllable temperature gradient is formed between the first and second temperature control devices. In this embodiment, the first temperature control device is arranged at the left end of the frozen soil structure simulation device 6, so that the aqueous solution containing microplastic particles 19 in the frozen soil structure simulation device 6 is gradually frozen from the left end to the right end to freeze, simulating the freezing process of microplastic particles 19 in a natural soil environment; after the microplastic particles 19 are frozen, the temperature of the first temperature control device is adjusted to increase its temperature to heat the frozen soil structure simulation device 6, so that the aqueous solution containing microplastic particles 19 is melted to complete melting, simulating the melting process of microplastic particles 19 in a frozen soil environment. The above-mentioned one freezing process and one melting process are a complete freeze-thaw cycle process. During this process, the second temperature control device placed 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 in a real soil environment. Specifically, the temperature control device 7 is a semiconductor refrigeration chip. Using temperature sensors embedded within the chip and a PID control algorithm (Proportional-Integral-Derivative Control Algorithm), precise temperature control and real-time feedback are achieved at both ends of the frozen soil structure simulator 6. The first and second temperature control devices have a temperature control range of -15°C to 20°C, with an accuracy of ±0.1°C. By placing the first and second temperature control devices at both ends of the frozen soil structure simulator 6, simulation of soil freezing and thawing processes under natural conditions is achieved, thereby simulating and monitoring the migration behavior of microplastic particles 19 in a frozen soil environment in real time. The first and second temperature control devices of this technical solution adhere to the upper and lower surfaces of the frozen soil structure simulator 6, respectively, ensuring stable temperature conduction and quickly achieving the required freezing and thawing temperature for the soil environment. This avoids the situation where the temperature control device 7 only contacts the frozen soil structure simulator 6, which could lead to poor contact due to slight looseness between the devices, resulting in poor transmission of cooling or heating temperature to the frozen soil structure simulator 6, preventing the experimental temperature from meeting the experimental requirements, particularly the freezing temperature, and thus affecting the final simulation results.

[0048] 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.

[0049] The image capture 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 by 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. Together with the CCD camera 10, the migration process of the microplastic particles 19 within the frozen soil structure simulation device 6 is imaged and monitored in real time. The image processing device 4 includes an image acquisition card and a computer. The image acquisition card is used to capture the 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 denoising, enhancement, and segmentation on the captured images of the microplastic particles 19, extracting characteristics such as the morphology, size, and quantity of the microplastic particles 19 for analysis and research on microplastic migration.

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

[0051] The coating layer 15 is composed of a crosslinker, a photoinitiator, a soluble mineral, and a thickener. By weight, the crosslinker comprises 0.5%-5%, the photoinitiator comprises 0.01%-0.1%, the soluble mineral comprises 2%-85%, and the thickener comprises 0%-2%. Specifically, for a configuration in which the protrusion 14 is integrally formed with the upper glass 12 or lower glass 13, the coating layer 15 comprises 0.5%-5% crosslinker, 0.01%-0.1% photoinitiator, and 2%-20% soluble mineral, with the remainder being deionized water, with the total of these components totaling 100%. Regarding the method of forming the protrusions 14 by dot coating, the protrusions 14 are made of a viscous material containing soluble minerals. After formation, the surface of the protrusions 14 is a coating layer 15 containing mineral components that simulates soil characteristics. The components of the viscous material include 2.5%-5% cross-linking agent, 0.01%-0.1% photoinitiator, 15%-85% soluble minerals and 0.5%-2% thickener, and the remainder is deionized water, and the total of all components is 100%. After the protrusions 14 are formed by dot coating, a light-curing aqueous solution containing soluble minerals is prepared to form a coating layer 15 on the upper and lower layers of glass 13. The components are 0.5%-3% cross-linking agent, 0.01%-0.1% photoinitiator and 2%-10% soluble minerals, and the remainder is deionized water, and the total of all components is 100%.

[0052] Specifically, this embodiment simulates seasonally frozen black soil around Shenyang, Liaoning Province, using ethylene glycol dimethacrylate as a crosslinker, benzophenone as a photoinitiator, dolomite, calcite, or mica as a soluble mineral, and carboxymethyl cellulose as a thickener. In an arrangement where the protrusion 14 is integrally formed with the upper glass 12 or lower glass 13, the coating layer 15 comprises, by weight percentage, 0.5% crosslinker, 0.1% photoinitiator, and 15% soluble mineral, with the remainder being deionized water, for a total of 100%. In the method of forming the protrusions 14 by dot coating, the composition of the viscous material containing soluble minerals is composed of 5% cross-linking agent, 0.05% photoinitiator, 65% soluble minerals, and 2% thickener, with the remainder being deionized water, and the total of these components is 100%. After the protrusions 14 are formed by dot coating, a light-cured aqueous solution containing soluble minerals is prepared and applied to the upper and lower layers of glass 13 to form a coating layer 15 with a composition of 0.5% cross-linking agent, 0.05% photoinitiator, and 5% soluble minerals, with the remainder being deionized water, and the total of these components is 100%. The coating layer 15 containing soluble minerals is formed by various methods, and soluble mineral factors are introduced to simulate natural soil particles. A frozen soil structure simulation device 6 with the pore structure distribution and mineral composition of natural soil is obtained. The influence and effect of soil particles on the migration behavior of microplastic particles 19 are further studied to better simulate the migration process of microplastic particles 19 in soil pores under freeze-thaw conditions.

[0053] The method for simulating and monitoring frozen soil by the simulated monitoring device for frozen soil change process comprises the following steps:

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

[0055] 2) Injecting an aqueous solution containing microplastic particles through the inlet of the frozen soil structure simulation device 6 so that the aqueous solution of microplastic particles fills the interior of the frozen soil structure simulation device 6, placing the frozen soil structure simulation device 6 in a constant temperature box 1, adjusting the temperature of the constant temperature box 1 and the temperature control device 7 to 1°C to 5°C, and letting it stand for 10 to 15 minutes to evenly distribute the aqueous solution of microplastic particles in the frozen soil structure simulation device 6, and to obtain the initial distribution state of the microplastic particles in the soil pores. During this period of time, the temperature of the constant temperature box 1 and the temperature control device 7 remain consistent;

[0056] 3) After the temperature inside the frozen soil structure simulation device 6 reaches stability, the temperature of the temperature control device 7 is lowered, and one end of the frozen soil structure simulation device 6 begins to be cooled to below 0°C, while the temperature of the other end is always kept consistent with the temperature of the constant temperature box 1, so that the aqueous solution containing microplastic particles is frozen unidirectionally from the cold end to the warm end until the frozen state of the aqueous solution is stable;

[0057] 4) The temperature of the temperature control device 7 is increased, starting from one end of the 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) to 4) above is recorded, wherein one freezing process and one ablation process in 3) and 4) constitute one freeze-thaw cycle;

[0059] Image information is extracted and processed from the recorded videos of the above processes.

[0060] In the method of simulating and monitoring frozen soil using a simulation monitoring device for the frozen soil change process, first, microplastic particles 19 with a diameter range of 1 μm-5 mm 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%; second, the prepared aqueous solution containing microplastic particles 19 is slowly injected from the inlet of the frozen soil structure simulation device 6 until it fills the entire area where the convex parts 14 of the frozen soil structure simulation device 6 are distributed, and the frozen soil structure simulation device 6 containing the aqueous solution containing microplastic particles is transferred to the constant temperature box 1, and the temperature of the constant temperature box 1 and the second temperature control device are adjusted to 1°C~5°C. In particular, the constant temperature box 1 and the second temperature control device are The temperature of the control device is set to 2°C and allowed to stand for 15 minutes until the microplastic particle aqueous solution is evenly distributed inside the frozen soil structure simulation device 6. This state simulates the initial distribution state of the microplastic particles 19 in the soil pores. At this time, the image capture device 2 is used to collect the overall distribution image of the microplastic particles 19; then, the first temperature control device on the left end of the frozen soil structure simulation device 6 is turned on to start cooling, so that the frozen soil structure simulation device 6 is gradually cooled from one end 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, so that the aqueous solution containing microplastic particles 19 is unidirectionally frozen from the cold end to the warm end with the unidirectional cooling until the freezing state of the aqueous solution containing microplastic particles 19 is stable. In the initial stage of freezing, the image capture device 2 collects the overall distribution image of the microplastic particles 19 in the frozen soil structure simulation device 6 every 5-15 seconds. After the microplastic particles 19 are completely frozen until the freezing front is stable, the image capture device 2 collects the overall distribution image of the microplastic particles 19 every 2-5 minutes; the fourth step, after the soil freezing process is completed and stood still for 3-5 minutes, adjust the first temperature control device on the left end of the temperature control device 6 to increase its temperature, so as to cause the frozen aqueous solution in the device 6 to gradually melt until the aqueous solution is completely in a liquid state. During this process, the overall distribution image of the microplastic particles 19 is collected every 5-15 seconds. After the aqueous solution containing the microplastic particles 19 is completely melted until the melting front is stable, the image of the microplastic particles 19 is collected every 2-5 minutes. Overall distribution image; In the fifth step, the image captured 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 the captured image according to the initial distribution state of the microplastic particles 19, the freezing process and the change process of the ablation process, and performs pre-processing such as denoising, enhancement, and segmentation on the captured image. The microplastic particles 19 in the image are then identified and located, and the position coordinate information of the microplastic particles 19 is obtained. According to 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, and the characteristic parameters such as the size, shape, migration speed, and migration distance of the microplastic particles 19 are extracted, and statistical analysis is performed. The analysis results are used to produce intuitive diagrams such as the trajectory of the microplastic particles 19 and the migration heat map.At the same time, the physical and chemical properties of the microplastic particles 19 after freezing and thawing can be studied. After the freeze-thaw process, the microplastic particles 19 in the frozen soil structure simulation device 6 are rinsed out with deionized water, and the physical and chemical properties of the microplastic particles 19 are characterized using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and other technical means. Through the image data analysis of this experiment, it can be seen that as the soil environment temperature decreases, the aqueous solution of microplastic particles 19 in the frozen soil structure simulation device 6 gradually freezes and freezes. As the water solidifies into ice, its volume increases, causing the microplastic particles 19 to migrate and redistribute under the squeezing action of ice crystals, showing a trend of gathering toward the center and lower part of the microchannel in the frozen soil structure simulation device 6. Then, during the heating process of the second temperature control device, the ice crystals gradually melt. As the temperature continues to rise, the microplastic particles 19 further migrate with the flow of the solution, showing a trend of spreading toward the upper part and both sides of the microchannel in the frozen soil structure simulation device 6. Through the simulation monitoring method of the technical solution of the present invention, the migration environment of microplastic particles in natural soil can be restored more accurately and realistically, and the complex migration behavior of microplastic particles in the soil environment under freeze-thaw conditions can be comprehensively observed and analyzed, thereby improving the simulation and dynamic monitoring capabilities, and providing better experimental means for related research.

[0061] During the simulated monitoring process, before step 2), images of the upper and lower glasses in their original states and image information of the upper and lower glasses covered with soluble minerals before the microplastic-containing aqueous solution was injected were collected.

[0062] In order to further improve the experimental precision and accuracy, real-time status data of microplastic particles 19 are collected at different stages of the simulation process to achieve more accurate and comprehensive simulation experimental results. At the beginning of the simulation experiment, images of the original state of the upper and lower layers of glass 12 and 13 before the soluble mineral coating layer 15 was set, and image information of the upper and lower layers of glass 12 and 13 covered with soluble minerals before the aqueous solution containing microplastic particles 19 was injected were collected. After the aqueous solution of microplastic particles 19 was injected, image information of the stable distribution of the aqueous solution containing microplastic particles 19 in the permafrost structure simulation device 6 was collected. In the freezing and ablation stages, image information in the early stage of freezing or melting and image information after the freezing or melting was stabilized were collected. In the initial stage of freezing, the image capture device 2 captured the overall distribution image of the microplastic particles 19 in the permafrost structure simulation device 6 every 10 seconds. After the microplastic particles 19 were completely frozen until the freezing front was stable, the image capture device 2 captured the overall distribution image of the microplastic particles 19 every 3 minutes. After the freezing process was completed, in the initial stage of melting of the microplastic particles 19, the overall distribution state of the microplastic particles 19 was collected every 10 seconds. After the aqueous solution containing microplastic particles 19 was completely ablated until the melting front was stable, the overall distribution state of the microplastic particles 19 was collected every 3 minutes. In this technical solution, the upper and lower layers of glass 12 and 13 are made of quartz glass material. Quartz glass material has excellent properties in terms of light transmittance, refractive index and absorptivity, but there is still a certain error effect on the observation and data collection of the migration simulation process of microplastic particles 19. Therefore, the original state images of the upper and lower layers of glass 12 and 13 when they are not covered with soluble minerals are collected, which is mainly used to study and analyze the influence of the glass structure itself on light penetration, absorption, refraction and other aspects, and the influence of the glass's reflectivity to light on visual clarity. The above-mentioned influencing factors can be eliminated when post-processing the experimental images to correct the errors caused by the glass itself to the experimental data; image information of the upper and lower layers of glass 12 and 13 covered with soluble minerals before the injection of aqueous solution containing microplastic particles 19 is collected, which 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 experimental simulation are further improved. Image information of the stable liquid distribution of an aqueous solution containing microplastic particles 19 in a frozen soil structure simulation device 6, as well as image information before freezing or melting and after stabilization of freezing or melting, is collected for real-time monitoring of the distribution state and migration behavior of microplastic particles in soil at normal temperature and under temperature change conditions, and then to simulate and analyze the migration trajectory and migration behavior characteristics of microplastic particles in a natural freeze-thaw soil environment.

[0063] In particular, in the simulation monitoring method of the present technical solution, the farmland soil environment around Shenyang City, Liaoning Province is simulated, and polyethylene microplastic particles 19 with a diameter range 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, according to the total concentration of microplastics in the black soil of farmland in the surrounding areas of Shenyang, which ranges from 217.30~2512.18μg / g and the average total concentration is 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 the frozen-thaw soil in the black soil environment of the actual sampling area, so as to further study the migration path of microplastic particles.

Claims

1. A simulation monitoring device for frozen soil change process, comprising a constant temperature box (1), the constant temperature box (1) having an image acquisition device (2) and a light source (3) arranged opposite to each other, the image acquisition device (2) being connected to an image processing device (4), characterized in that: A stage between the image capture device (2) and the light source (3) is provided with a frozen soil structure simulation device (6) having a high degree of soil simulation. The frozen soil structure simulation device (6) is composed of two layers of light-transmitting structures, a plurality of convex portions (14) are provided between the two layers of structures, and a coating layer (15) is provided on the surface of the convex portions (14). The frozen soil structure simulation device (6) is provided with an inlet and an outlet, and the frozen soil structure simulation device (6) is provided with a temperature control device (7).

2. The simulation monitoring device for frozen soil change process according to claim 1, characterized in that: The frozen soil structure simulation device (6) comprises an upper layer of glass (12), a lower layer of glass (13), and a plurality of irregular protrusions (14) arranged between the upper layer of glass (12) and the lower layer of glass (13) and distributed according to soil pore distribution information, with tiny gaps between the protrusions (14), and a coating layer (15) simulating soil characteristics on the surface of the protrusions (14) and the inner surfaces of the upper and lower glasses.

3. The simulation monitoring device for frozen soil change process according to claim 1 or 2, characterized in that: The convex portion (14) is formed integrally with the lower layer of glass (13), or the convex portion (14) is formed integrally with the upper layer of glass (12), or is formed by point coating.

4. The simulation monitoring device for frozen soil change process according to claim 3 is characterized in that: The temperature control device (7) comprises a first temperature control device and a second temperature control device, which are located at two 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).

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

6. The device for simulating and monitoring the frozen soil change process according to claim 5, characterized in that The coating layer (15) comprises the following components by weight percentage: Crosslinking agent 0.5%-5%; Photoinitiator 0.01%-0.1%; Soluble minerals 2%-85%; Thickener 0%-2%; The rest is deionized water, and the sum of all components is 100%.

7. The simulation monitoring device for frozen soil change process according to claim 6 is characterized in that The coating layer (15) comprises the following components in terms of weight percentage: Ethylene glycol dimethacrylate 0.5%-5%; Benzophenone 0.01%-0.1%; Dolomite or calcite or mica 2%-85%; Carboxymethyl cellulose 0%-2%; The rest is deionized water, and the sum of all components is 100%.

8. A method for simulating monitoring frozen soil according to the device for simulating monitoring the frozen soil change process according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) Preparing an aqueous solution containing microplastic particles; 2) injecting an aqueous solution containing microplastic particles through the inlet of the frozen soil structure simulation device (6) so that the aqueous solution of microplastic particles fills the frozen soil structure simulation device (6), placing the frozen soil structure simulation device (6) in a constant temperature box (1), adjusting the temperature of the constant temperature box (1) and the temperature control device (7) to 1°C to 5°C, and leaving it to stand for 10 to 15 minutes so that the aqueous solution of microplastic particles is evenly distributed in the frozen soil structure simulation device (6), and capturing the initial distribution state of the microplastic particles in the soil pores. During this period of time, the temperature of the constant temperature box (1) and the temperature control device (7) remain consistent; 3) After the temperature inside the frozen soil structure simulation device (6) reaches stability, the temperature of the temperature control device (7) is lowered, and one end of the frozen soil structure simulation device (6) begins to be cooled to below 0° C., while the temperature of the other end is always kept consistent with that of the constant temperature box (1), so that the aqueous solution containing microplastic particles is frozen unidirectionally from the cold end to the warm end until the frozen state of the aqueous solution is stable; 4) The temperature of the temperature control device (7) is increased, starting from one end of the frozen soil structure simulation device (6), so that the frozen aqueous solution containing microplastic particles gradually melts until the aqueous solution is completely in a liquid state; Video recording the process of steps 2) to 4) above; 5) Extract and process image information from the recorded videos of the above processes.

9. The simulation monitoring method according to claim 8, characterized in that: During the simulated monitoring process, before step 2, images of the upper and lower glasses in their original states and image information of the upper and lower glasses covered with mineral particles before the microplastic-containing aqueous solution was injected were collected.

10. The simulation monitoring method according to claim 9, characterized in that: The method for preparing the aqueous solution containing microplastic particles in step 1) includes: selecting polyethylene microplastic particles with a diameter ranging from 5 to 100 μm, adding the above microplastics into deionized water, and preparing an aqueous solution containing microplastic particles with a mass concentration of 0.05%-0.3%.

Images