A method for identifying groundwater preferential flow paths of microplastics
By embedding organotantalum compounds within the bulk phase of microplastics, a stable tracer system is constructed, solving the problem of difficulty in identifying and quantitatively characterizing the migration pathways of microplastics in existing technologies, and realizing accurate identification and quantitative characterization of microplastics in groundwater systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHWEST JIAOTONG UNIV
- Filing Date
- 2026-06-10
- Publication Date
- 2026-07-10
AI Technical Summary
Existing technologies struggle to accurately identify and quantify the migration pathways of microplastics in groundwater systems, especially their preferred flow paths. Furthermore, traditional solute tracers are prone to desorption, altering the surface properties of microplastics and leading to biases.
By embedding organic tantalum compounds into microplastics to form microplastic particles, a stable tracer system is constructed. Particle size classification and tracer suspension preparation are carried out. Combined with a groundwater simulation system, preferential flow tracer experiments are conducted to collect and analyze the content of organic tantalum compounds in water samples and identify preferential flow paths.
This method achieves a true reflection and quantitative characterization of microplastic migration behavior, reduces the systematic bias of traditional methods, and improves the accuracy of experimental results and their engineering applicability.
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Figure CN122361209A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of groundwater pollution monitoring, and more specifically, to a method for identifying the preferential flow path of groundwater containing microplastics. Background Technology
[0002] Currently, studies on pollutant migration pathways in groundwater systems primarily employ solute tracers such as chloride ions and fluorescent dyes. However, solute tracers migrate in a completely dissolved state, and their migration process mainly reflects the water flow path, making it difficult to accurately characterize the particle migration behavior of microplastics in porous media. Furthermore, the low concentration of microplastics and strong background interference in groundwater environments hinder continuous monitoring and precise quantification of microplastic migration processes. Although some studies have attempted to enhance the signal by staining or labeling microplastics, the labels are prone to desorption during migration and can alter the surface properties of microplastics, affecting their actual migration behavior. In addition, existing research largely remains at the level of qualitative description of microplastic migration phenomena, lacking systematic identification and quantitative characterization of preferential flow paths for microplastics in groundwater systems based on particle tracer signals. Summary of the Invention
[0003] The purpose of this invention is to provide a method for identifying preferential flow paths of microplastics in groundwater. By constructing a stable and highly sensitive labeled microplastic tracer system, the method achieves accurate identification and quantitative characterization of the migration paths and preferential flow channels of microplastics in the soil-groundwater system, thereby reducing the biases introduced by traditional tracer methods. To achieve the above objective, the technical solution adopted by this invention is as follows: A method for identifying groundwater preferential flow paths using microplastics, the method comprising: Organotantalum compounds are labeled into microplastics via bulk embedding to form microplastic particles; The microplastic particles were added to a groundwater simulation solution to prepare a tracer suspension. The tracer suspension was introduced into a groundwater simulation system and a preferential flow tracer experiment was conducted. Sampling points were set up at different spatial locations in the groundwater simulation system, and water samples were collected from each sampling point. The tracer signals of water samples from each sampling point were quantitatively analyzed to obtain the content of organic tantalum compounds at each sampling point; Based on the content of organic tantalum compounds at each sampling point, the preferred flow path of microplastics in the groundwater simulation system was determined.
[0004] Furthermore, organotantalum compounds are labeled within microplastics via bulk embedding to form microplastic particles, including: Microplastics and an organotantalum compound are co-dispersed in an organic solvent to form a mixture, wherein the microplastics are polyethylene; The mixture is heated at 50°C to remove the organic solvent, thereby embedding the organotantalum compound inside the microplastic to form a sheet. After the thin sheet is subjected to low-temperature embrittlement, it is pulverized under freezing conditions to obtain microplastic particles.
[0005] Furthermore, the microplastics and organotantalum compounds are dispersed in an organic solvent to form a mixture, comprising: Weigh 5g of polyethylene powder and add it to 100-150ml of anhydrous toluene. Reflux and stir at 100-105℃ to obtain a homogeneous sol system. Add 0.05-0.1g of organotantalum compound to the sol system and continue stirring for 30 minutes to ensure complete dispersion of the organotantalum compound in the sol system, forming a mixture.
[0006] Furthermore, after the sheet is subjected to low-temperature embrittlement, it is pulverized under freezing conditions to obtain microplastic particles, including: The thin sheet is cut into small pieces with a size of 0.5-1cm, and the small pieces are pre-cooled at -80℃ for 55-65min to enter the initial brittle state; After the small pieces have entered the initial brittle state, they are immersed in liquid nitrogen for about 15 minutes to enter the highly brittle state. After the small pieces have entered a highly brittle state, they are transferred to a cryogenic grinder and ground into microplastic particles under liquid nitrogen cooling conditions.
[0007] Furthermore, the microplastic particles are added to a groundwater simulation solution to prepare a tracer suspension, comprising: The microplastic particles are subjected to particle size classification to screen out tracer particles, wherein the tracer particles have a particle size in the range of 10–500 μm. The tracer particles were added to a groundwater simulation solution, mixed using magnetic stirring, and then ultrasonically dispersed for 5–10 minutes to prepare a solution with a concentration of 0.1–5 mg / L. -1 The tracer suspension.
[0008] The microplastic particles are subjected to particle size classification to screen out tracer particles, including: Microplastic particles were sieved using a 500μm screen to remove large particles larger than 500μm. The remaining particles after sieving are added to ultrapure water, and the microplastic particles are dispersed in the liquid phase by magnetic stirring for 10 minutes and ultrasonic dispersion for 15 minutes to form a dispersion. The dispersion was filtered using a 10 μm pore size filter membrane to retain tracer particles labeled with organotantalum compounds with particle sizes in the range of 10–500 μm.
[0009] Furthermore, the tracer suspension is introduced into a groundwater simulation system and preferential flow tracer experiments are conducted, including: A groundwater simulation system was constructed as a tracer test platform. The water simulation system was filled with a porous media system, in which different heterogeneous structures were set to simulate the zonal region and the background medium region. A groundwater simulation solution was injected into the groundwater simulation system to saturate the porous media system, and seepage conditions were established through flow control methods. The tracer suspension is introduced into the inlet of the groundwater simulation system via pulse injection or constant flow rate, and enters the porous media system along with the groundwater simulation solution.
[0010] Furthermore, sampling points are set up at different spatial locations in the groundwater simulation system, and water samples are collected from each sampling point, including: Multiple sampling points are set in the strip region and the background medium region respectively, and the multiple sampling points in the strip region are symmetrical with the multiple sampling points in the background medium region; A sampling point was set at the outlet of the strip area and the outlet of the background medium area, respectively; Water samples were collected synchronously from each sampling point according to the preset time interval.
[0011] Furthermore, the tracer signals of water samples from each sampling point were quantitatively analyzed to obtain the content of organotantalum compounds at each sampling point, including: Each water sample was digested sequentially to prepare a digestion solution; The digestion solution was brought to a final volume to obtain the solution to be tested. The content of organotantalum compounds in the test solution was determined by inductively coupled plasma mass spectrometry.
[0012] Furthermore, based on the content of organotantalum compounds at each sampling point, the preferred flow paths of microplastics in the groundwater simulation system were determined, including: Based on the change in the content of organotantalum compounds at each sampling point over time, a breakthrough curve for labeled microplastics was constructed. By comparing the characteristic parameters of the penetration curves at different sampling points, the preferred flow path is identified; wherein, the characteristic parameters include at least one of the initial arrival time, peak occurrence time, and peak concentration.
[0013] The beneficial effects of this invention are: By constructing a stable, highly sensitive particle tracer system that does not alter the surface properties of microplastics, we can accurately reflect the migration behavior of microplastics in the soil-groundwater system. Based on the particle tracer signal, we can accurately identify and quantitatively characterize the preferential flow path of microplastics in the groundwater system, thereby reducing the systematic bias caused by traditional tracer methods and improving the ability of experimental results to accurately reflect the actual groundwater system and their engineering applicability.
[0014] Other features and advantages of the invention will be set forth in the following description, and in part will be obvious from the description or may be learned by practicing the embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings. Attached Figure Description
[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 A schematic diagram of a method for identifying the preferential flow path of groundwater in microplastics; Figure 2 A schematic diagram of labeled polyethylene particles with a particle size of 10-500 μm; Figure 3 This is a schematic diagram of the groundwater simulation system.
[0017] Marked in the image: 1. Background medium area; 2. Strip area; 3. Valve; 4. Second inlet; 5. First inlet; 6. First outlet; 7. Second outlet. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0019] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0020] Example 1: like Figure 1 As shown, this embodiment provides a method for identifying the preferred flow paths of microplastics in groundwater, used to identify and characterize the preferred flow paths of microplastics in groundwater systems. This is of great significance for accurately assessing the environmental behavior of microplastics and their potential risks. The method includes: S1. Organotantalum compounds are labeled into microplastics via bulk embedding to form microplastic particles; In this embodiment, since microplastics in the environment are mainly polyethylene materials, and their chemical properties are stable and their distribution is widespread, high-density polyethylene (HDPE) is selected as the labeled material. In this embodiment, an organotantalum compound is stably introduced into the HDPE polymer matrix through bulk embedding, thereby obtaining a labeled material with a stable tracer signal without changing the surface properties of HDPE.
[0021] Specifically, step S1 includes: S11. Microplastics and an organotantalum compound are co-dispersed in an organic solvent to form a mixture, wherein the microplastics are polyethylene; Specifically, weigh 5g of polyethylene powder and add it to 100-150ml of anhydrous toluene, reflux and stir at 100-105℃ to obtain a homogeneous sol system. Add 0.05-0.1g of organotantalum compound to the sol system and continue stirring for 30min to completely disperse the organotantalum compound in the sol system to form a mixture; wherein the mass of the organotantalum compound is 1-2% of the mass of HDPE, preferably, the organotantalum compound is pentaethoxytantalum or pentabutoxytantalum.
[0022] Through the above mixing method, the organic tantalum compound is embedded in the HDPE bulk phase at the molecular level, rather than simply attached to the material surface, thereby forming an embedded structure with a stable tracer signal and without changing the surface properties of HDPE.
[0023] S12. The mixture is heated at 50°C to remove the organic solvent, so that the organic tantalum compound is embedded in the microplastic to form a sheet; Specifically, the above mixture is poured into a glass dish and spread into a thin layer. The dish is then dried in an oven at 50°C for 24 hours to completely remove toluene. After complete solvent evaporation, HDPE thin films or blocks labeled with organotantalum compounds are obtained.
[0024] Through the above preparation process, the organotantalum compound is stably fixed inside the HDPE polymer matrix, and it is not easy to desorb or dissolve during the subsequent microplastic preparation, migration and tracing process. At the same time, it maintains the original surface chemical properties and physical characteristics of HDPE, providing a reliable material basis for constructing tracer particles that truly reflect the migration behavior of microplastics.
[0025] S13. After the sheet is subjected to low-temperature embrittlement, it is pulverized under freezing conditions to obtain microplastic particles; Specifically, step S13 includes: S131. Cut the thin sheet into small pieces with a size of 0.5-1cm, and pre-cool the small pieces at -80℃ for 1 hour to lower the overall temperature of the material and allow it to enter the initial brittle state; S132. After the small pieces have entered the initial brittle state, immerse them in liquid nitrogen for about 15 minutes to enter the highly brittle state; S133. After the small pieces have entered a highly brittle state, they are transferred to a cryogenic grinder and ground into microplastic particles under liquid nitrogen cooling conditions; Preferably, the grinding frequency is set to 10–15 Hz, the grinding time for a single cycle is 3–5 min, and a cooling interval of 1–2 min is set between adjacent grinding cycles to maintain a low-temperature environment during the grinding process. By repeating the grinding process 5–8 times, the small pieces are gradually broken into microplastic particles with a wide particle size distribution and irregular morphology under impact and shearing action.
[0026] In this embodiment, the small pieces are subjected to low-temperature treatment, which effectively avoids the softening, stretching, or melting and adhesion of HDPE due to local heating during the crushing process. This ensures that the resulting microplastic particles have irregular shapes and rough edges, which are closer to the actual morphological characteristics of microplastics in the natural environment. In addition, no additional chemical reagents or high-temperature conditions are introduced during the entire crushing process. The organic tantalum compound remains stably retained inside the HDPE polymer matrix, avoiding the migration or loss of the marker and ensuring the stability and repeatability of the subsequent tracer detection signal.
[0027] Based on the above embodiments, this method further includes: S2. The microplastic particles are added to a groundwater simulation solution to prepare a tracer suspension; Preferably, to ensure the comparability of microplastic migration behavior and the interpretability of results in the tracer experiment, this embodiment further performs particle size classification on the microplastic particles and selects target particle size ranges that are environmentally representative and experimentally feasible as tracer particles.
[0028] Existing environmental surveys and research results indicate that microplastic particles with a diameter greater than 500 μm are more easily restricted by pore size and structural characteristics when migrating in porous media, and are prone to physical sieving and retention, which is not conducive to reflecting the dynamic process of microplastic migration with groundwater. While microplastics with a diameter less than 10 μm have a stronger migration ability, they are significantly more difficult to detect in complex groundwater environments and are easily interfered with by background particles, which is not conducive to achieving stable and accurate quantitative analysis.
[0029] Meanwhile, microplastics with particle sizes ranging from 10 to 500 μm are widely distributed and constitute a large proportion of the natural environment, and can well represent the dominant particle size characteristics of microplastics in the environment. Therefore, labeling microplastics with organotantalum compounds in the 10–500 μm particle size range by particle size classification and screening can achieve a balance between detection sensitivity, quantitative accuracy, and result repeatability in groundwater system tracer experiments while ensuring the authenticity of microplastic migration behavior.
[0030] Specifically, the microplastic particles are subjected to particle size classification, including the following steps: Microplastic particles were sieved using a 500μm screen to remove large particles larger than 500μm. The remaining particles after sieving are added to ultrapure water, and the microplastic particles are dispersed in the liquid phase by magnetic stirring for 10 minutes and ultrasonic dispersion for 15 minutes to form a dispersion. The dispersion was filtered using a 10 μm pore size filter membrane to retain tracer particles labeled with organotantalum compounds with particle sizes in the range of 10–500 μm.
[0031] By combining sieving and filtration, the particle size classification method described above can obtain target microplastic particles with a clear size range and relatively concentrated distribution, while ensuring the integrity of particle morphology and labeling stability. This provides a standardized tracer medium for the subsequent preparation of labeled HDPE tracer suspensions and groundwater preferential flow tracer experiments.
[0032] Specifically, the method for preparing the tracer suspension includes: The tracer particles were added to a groundwater simulation solution, mixed using magnetic stirring, and then ultrasonically dispersed for 5–10 minutes to prepare a solution with a concentration of 0.1–5 mg / L. -1 The tracer suspension is prepared by ultrasonic dispersion to fully disperse the microplastic particles in the liquid phase, thus avoiding particle aggregation or rapid sedimentation.
[0033] Specifically, the groundwater simulation solution can be configured according to research needs, and its ionic composition and ionic strength are used to simulate the actual groundwater environment to ensure the environmental relevance of the tracer conditions.
[0034] Based on the above embodiments, after the tracer suspension is prepared, it is used in a preferential flow tracer experiment in a groundwater system to identify and quantitatively characterize the migration path and preferential flow channel of microplastics in porous media. Therefore, this method further includes: S3. Introduce the tracer suspension into the groundwater simulation system and conduct a preferential flow tracer experiment; Specifically, step S3 includes: S31. Construct a groundwater simulation system as a tracer test platform. The groundwater simulation device can be a one-dimensional soil column system or a two-dimensional sand box system. The water simulation system is filled with a porous medium system. Different heterogeneous structures are set in the porous medium system to simulate the zonal region 2 and the background medium region 1. Specifically, heterogeneous structures can be set up according to research needs, such as using different particle size fillers to partition areas, high permeability zones, or local disturbance areas, to simulate preferential flow channels that may exist in actual groundwater systems.
[0035] S32. Before the experiment begins, inject groundwater simulation solution into the groundwater simulation system to saturate the porous media system, and establish stable seepage conditions by adjusting the water head to control the flow rate. S33. The tracer suspension is introduced into the inlet of the groundwater simulation system by pulse injection or constant flow rate, so that the microplastics enter the porous media system along with the groundwater simulation solution. During the injection process, the injection flow rate and duration of the tracer suspension are controlled to avoid significant disturbance to the original hydraulic conditions, thereby ensuring that the tracer test reflects the real migration behavior of microplastics.
[0036] Based on the above embodiments, this method further includes: S4. Set up sampling points at different spatial locations in the groundwater simulation system and collect water samples from each sampling point; Specifically, step S4 includes: S41. Multiple sampling points are set in the strip region 2 and the background medium region 1 respectively, wherein the multiple sampling points in the strip region 2 are symmetrical to the multiple sampling points in the background medium region 1. S42. Set up a sampling point at the outlet of strip area 2 and the outlet of background medium area 1 respectively; S43. Collect water samples from each sampling point synchronously according to the preset time interval.
[0037] Based on the above embodiments, this method further includes: S5. Quantitatively analyze the tracer signals of water samples from each sampling point to obtain the content of organic tantalum compounds at each sampling point; Specifically, step S5 includes: S51. Digest each water sample sequentially to prepare a digestion solution; S52. Adjust the volume of the digestion solution to the predicted volume to obtain the solution to be tested; S53. As an optional implementation, the content of organotantalum compounds in the test solution is determined by inductively coupled plasma mass spectrometry (ICP-MS); In this embodiment, since the organotantalum compound is stably labeled within the microplastic particles in a bulk manner, the tantalum element signal detected in the water sample can be used as a characteristic tracer signal for the labeled HDPE microplastics. By measuring the tantalum element content in the solution after the particles trapped on the filter medium are completely digested, quantitative analysis of the mass concentration and migration flux of the labeled HDPE microplastics can be achieved.
[0038] Based on the above embodiments, this method further includes: S6. Based on the content of organic tantalum compounds at each sampling point, determine the preferred flow path of microplastics in the groundwater simulation system; Specifically, step S6 includes: S61. Based on the change of the content of organotantalum compound at each sampling point over time, construct the breakthrough curve of the labeled microplastics over time; S62. Compare the characteristic parameters of the penetration curves at different sampling points to identify the preferred flow path; wherein, the characteristic parameters include at least one of initial arrival time, peak occurrence time, and peak concentration; Specifically, when the penetration curve corresponding to a sampling point satisfies one or a combination of the following conditions, the flow channel where the sampling point is located is determined to be the preferred flow path of the microplastics: 1) The initial arrival time was relatively early; 2) It exhibits a high peak concentration under the same tracer conditions; 3) The peak concentration is relatively large.
[0039] Preferably, to further quantitatively characterize the contribution of the preferred flow path, this embodiment calculates the cumulative migration flux of each channel based on the polyethylene mass concentration at the sampling points on each channel, thus obtaining the contribution ratio of the flow channel in the overall microplastic transport process. Based on this contribution ratio, the main preferred flow channels of microplastics can be further verified.
[0040] The above methods can not only identify the main preferential flow channels of microplastics, but also compare and analyze the differences in transport capacity between different channels.
[0041] In summary, the priority flow path identification method provided in this embodiment overcomes the shortcomings of existing technologies that rely heavily on qualitative judgments and are difficult to quantitatively compare, and provides a reliable technical means for characterizing the migration path of microplastics in groundwater systems.
[0042] Example 2: This embodiment will describe the method of Embodiment 1 in detail with specific implementation parameters. In this embodiment, high-density polyethylene (HDPE) is used as the tracer carrier, and an organotantalum compound bulk phase embedding labeling method is adopted. A polyethylene preferential flow tracer experiment is carried out in conjunction with a groundwater simulation system, and the polyethylene preferential flow path in the groundwater system is identified and quantitatively characterized based on the tracer signal.
[0043] S1. An organotantalum compound is embedded in polyethylene to form polyethylene particles; the reactor is a 250ml three-necked flask with a reflux condenser, a thermometer, and a magnetic stir bar; and a 15cm diameter glass petri dish is used.
[0044] Specifically, step S1 includes: S11. Add 120 mL of anhydrous toluene to a three-necked flask, turn on the magnetic stirrer, weigh 5 g of polyethylene powder and add it to the anhydrous toluene, connect the reflux condenser, heat the system in an oil bath to 105 °C and maintain the temperature until there are no visible polyethylene solid particles in the system and a homogeneous sol system is formed.
[0045] Add 0.05 g of tantalum pentaethoxyate to the sol system all at once and continue stirring for 30 min. Then stop heating, remove the flask from the oil bath, cool to 80 °C, and continue stirring for 5 min to form a mixture.
[0046] The mixed sol was then poured into a glass petri dish and spread into a uniform thin layer. The petri dish was then placed in a 50°C oven and dried for 24 hours to allow the anhydrous toluene to completely evaporate, resulting in a thin layer of organotantalum compound-embedded polyethylene.
[0047] S12. Cut the thin layer into 8mm × 8mm pieces. Place the pieces in a freezer at -80℃ for 1 hour, then immediately immerse them in liquid nitrogen for 15 minutes.
[0048] After the small pieces entered the initial brittle state, they were transferred to a cryogenic mill. The milling frequency was set to 12 Hz, and each milling session lasted 4 minutes with a 2-minute cooling interval. This process was repeated 6 times to obtain irregularly shaped marked polyethylene particles.
[0049] S2. The labeled polyethylene particles are added to a groundwater simulation solution to prepare a tracer suspension; Specifically, step S2 includes: S21. The labeled polyethylene particles were sieved through a 500μm stainless steel standard sieve under dry conditions, and the sieved material was collected. Then, the sieved material was added to 500ml of ultrapure water and magnetically stirred for 10min at 800rpm, followed by ultrasonic dispersion for 15min.
[0050] Subsequently, filtration is performed using a 10μm pore size filter membrane, preferably made of glass fiber. After filtration, the filter membrane residue is rinsed three times with ultrapure water to remove dissolved background substances, and finally, the filter membrane is dried in a 50℃ oven for 2 hours. Marked polyethylene particles of 10-500μm can be obtained by gently scraping the surface of the filter membrane with a scraper. Figure 2 As shown.
[0051] In this embodiment, the water contact angle of polyethylene before and after marking was measured using a standard optical contact angle meter. The water contact angle of polyethylene before marking was 102.6°, while the water contact angle of polyethylene marked with organotantalum compound was 102.3°, indicating that the surface hydrophilic and hydrophobic properties of polyethylene do not change after organotantalum compound is introduced into polyethylene in an embedded manner.
[0052] Meanwhile, the surface ZETA potential of polyethylene before and after labeling was measured. The surface ZETA potential of polyethylene before labeling was -24.7 mV, while the surface ZETA potential of polyethylene labeled with organotantalum compound was -23.5 mV, indicating that the surface ZETA potential of polyethylene does not change significantly after organotantalum compound is introduced into polyethylene in an intercalation manner.
[0053] Subsequently, 0.2g of labeled polyethylene particles were weighed and added to 200L of groundwater simulation solution. The mixture was first magnetically stirred for 10 minutes at a speed of 800 rpm, and then ultrasonically dispersed for 10 minutes to ensure complete dispersion of the labeled polyethylene particles, thus preparing a tracer suspension of 1 mg / L.
[0054] Preferably, in this embodiment, a groundwater simulation solution is composed of 0.01 mol / L NaCl, 0.001 mol / L CaCl2, and 0.002 mol / L NaHCO3, and the groundwater simulation solution is adjusted to pH 7 using HCl / NaOH.
[0055] S22. A two-dimensional sandbox is selected as the groundwater simulation system. The dimensions of the two-dimensional sandbox are: length 80cm, width 30cm, and height 40cm. The material is acrylic with a thickness of 1cm.
[0056] The two-dimensional sand box includes a strip zone 2 and a background medium zone 1. The strip zone 2 traverses the background medium zone 1, has a width of 5 cm, and is centrally buried. The background medium zone 1 uses a porous medium system filled with quartz sand with a particle size of 0.3-0.6 mm, and the strip zone 2 uses a porous medium system filled with quartz sand with a particle size of 1-1.5 mm. The specific structure is as follows: Figure 3 As shown: Specifically, a first water inlet pipe and a first water outlet pipe are respectively provided on both sides of the strip area 2. The first water inlet pipe is connected to the first water inlet 5, and the first water outlet pipe is connected to the first water outlet 6. A second water inlet pipe and a second water outlet pipe are respectively provided on both sides of the background medium area 1. The second water inlet pipe is connected to the second water inlet 4, and the second water outlet pipe is connected to the second water outlet 7. Among them, the first water inlet pipe, the first water outlet pipe, the second water inlet pipe and the second water outlet pipe are all equipped with valves 3.
[0057] The groundwater simulation solution was slowly injected into the two-dimensional sand box through the first inlet 5 and the second inlet 4 until it was completely saturated. Then, a constant flow pump was used to maintain a flow rate of 10 mL / min for 60 minutes in a steady state.
[0058] Subsequently, a 1 mg / L labeled suspension was injected in a pulse manner from the first inlet 5 and the second inlet 4, respectively, at a flow rate of 10 mL / min. After the injection was completed, the mixture was flushed with groundwater simulation solution.
[0059] Based on the above embodiments, this method further includes: S4. Set up sampling points at different spatial locations in the groundwater simulation system and collect water samples from each sampling point; Specifically, four sampling points are set in the strip region 2, namely a, b, c, and d, and four sampling points are set in the background medium region 1, namely f, g, h, and i. The four sampling points in the strip region 2 are symmetrical to the four sampling points in the background medium region 1. A sampling point, e and j, is set at the outlet of strip region 2 and the outlet of background medium region 1, respectively; At 5-minute intervals, 5 ml water samples were collected simultaneously at sampling point aj, and sampling was continued for 120 minutes.
[0060] Based on the above embodiments, this method further includes: S5. Quantitatively analyze the tracer signals of water samples from each sampling point to obtain the content of organic tantalum compounds at each sampling point; Specifically, each water sample was digested to completely decompose the polyethylene matrix and the organotantalum compounds embedded within it, converting them into a detectable form of tantalum. After digestion, the digestion solution was brought to a final volume of 100 ml to obtain the test solution.
[0061] Furthermore, in this embodiment, the total amount of tantalum in the test solution was determined by ICP-MS to obtain the mass concentration of tantalum in the water sample at each time point: The mass concentration of polyethylene in the water sample is calculated based on the mass concentration of tantalum in the water sample. The specific calculation formula is as follows: ; In the formula, This indicates the concentration of tantalum pentaethoxy in the water sample. This indicates the relative molecular mass of tantalum pentaethoxy. This represents the mass concentration of tantalum in the water sample. This indicates the mass concentration of polyethylene in the water sample.
[0062] Based on the above embodiments, this method further includes: S6. Based on the content of organic tantalum compounds at each sampling point, determine the preferred flow path of polyethylene in the groundwater simulation system; Specifically, a breakthrough curve (BTC) for labeled polyethylene is constructed with time as the horizontal axis and the mass concentration of polyethylene as the vertical axis.
[0063] Analyze the BTC at each sampling point and extract the arrival-through time for each sampling point. Peak time and peak concentration ; The cumulative migration flux of each channel is calculated based on the polyethylene mass concentration at the sampling points on each channel: ; In the formula, This represents the cumulative migration flux within the zonal region. This indicates the number of sampling points in the current channel. In the strip region, the sampling points refer to a, b, c, d, and e. Sampling points Constant flow rate for Time sampling point The mass concentration of polyethylene.
[0064] Similarly, the cumulative migration flux in the background medium region The calculation method is the same as above, and will not be repeated here.
[0065] Furthermore, the contribution ratio of polyethylene transported out of the sampling point during the entire tracer experiment was calculated based on the cumulative migration flux. The specific calculation method is as follows: ; In the formula, This indicates the contribution ratio of zone 2. This represents the cumulative migration flux in zone 2. The cumulative migration flux of background medium region 1, This indicates the contribution ratio of background medium region 1.
[0066] Compare two symmetrical sampling points in two channels. , , The pathways that meet one or a combination of the following conditions are identified as the preferred flow paths for polyethylene in the groundwater system: 1) Satisfy Smaller; 2) High; 3) Peak concentration Relatively large.
[0067] In this embodiment, by comparing a with f, b with g, c with h, d with i, and e with j, it can be concluded that a, b, c, d, and e are the preferred flow paths.
[0068] Furthermore, compare the two channels. and ,available Therefore, this further proves that zone 2 is the preferred flow path for polyethylene.
[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for identifying preferential groundwater flow paths using microplastics, characterized in that, include: Organotantalum compounds are labeled into microplastics via bulk embedding to form microplastic particles; The microplastic particles were added to a groundwater simulation solution to prepare a tracer suspension. The tracer suspension was introduced into a groundwater simulation system and a preferential flow tracer experiment was conducted. Sampling points were set up at different spatial locations in the groundwater simulation system, and water samples were collected from each sampling point. The tracer signals of water samples from each sampling point were quantitatively analyzed to obtain the content of organic tantalum compounds at each sampling point; Based on the content of organic tantalum compounds at each sampling point, the preferred flow path of microplastics in the groundwater simulation system was determined.
2. The method for identifying groundwater preferential flow paths using microplastics according to claim 1, characterized in that, Organotantalum compounds are labeled into microplastics via bulk embedding to form microplastic particles, including: Microplastics and an organotantalum compound are co-dispersed in an organic solvent to form a mixture, wherein the microplastics are polyethylene; The mixture is heated at 50°C to remove the organic solvent, thereby embedding the organotantalum compound inside the microplastic to form a sheet. After the thin sheet is subjected to low-temperature embrittlement, it is pulverized under freezing conditions to obtain microplastic particles.
3. The method for identifying groundwater preferential flow paths using microplastics according to claim 2, characterized in that, Microplastics and organotantalum compounds are dispersed in an organic solvent to form a mixture, comprising: Weigh 5g of polyethylene powder and add it to 100-150ml of anhydrous toluene. Reflux and stir at 100-105℃ to obtain a homogeneous sol system. Add 0.05-0.1g of organotantalum compound to the sol system and continue stirring for 30 minutes to ensure complete dispersion of the organotantalum compound in the sol system, forming a mixture.
4. The method for identifying preferential groundwater flow paths using microplastics according to claim 2, characterized in that, After the thin sheet is subjected to low-temperature embrittlement, it is pulverized under freezing conditions to obtain microplastic particles, comprising: The thin sheet is cut into small pieces with a size of 0.5-1cm, and the small pieces are pre-cooled at -80℃ for 55-65min to enter the initial brittle state; After the small pieces have entered the initial brittle state, they are immersed in liquid nitrogen for 15 minutes to enter the highly brittle state. After the small pieces have entered a highly brittle state, they are transferred to a cryogenic grinder and ground into microplastic particles under liquid nitrogen cooling conditions.
5. The method for identifying groundwater preferential flow paths using microplastics according to claim 1, characterized in that, The microplastic particles are added to a groundwater simulation solution to prepare a tracer suspension, comprising: The microplastic particles are subjected to particle size classification to screen out tracer particles, wherein the tracer particles have a particle size in the range of 10–500 μm. The tracer particles were added to a groundwater simulation solution, mixed using magnetic stirring, and then ultrasonically dispersed for 5–10 minutes to prepare a solution with a concentration of 0.1–5 mg / L. -1 The tracer suspension.
6. The method for identifying groundwater preferential flow paths using microplastics according to claim 5, characterized in that, The microplastic particles are subjected to particle size classification to screen out tracer particles, including: Microplastic particles were sieved using a 500μm screen to remove large particles larger than 500μm. The remaining particles after sieving are added to ultrapure water, and the microplastic particles are dispersed in the liquid phase by magnetic stirring for 10 minutes and ultrasonic dispersion for 15 minutes to form a dispersion. The dispersion was filtered using a 10 μm pore size filter membrane to retain tracer particles labeled with organotantalum compounds with particle sizes in the range of 10–500 μm.
7. The method for identifying groundwater preferential flow paths using microplastics according to claim 1, characterized in that, The tracer suspension was introduced into a groundwater simulation system and preferential flow tracer experiments were conducted, including: A groundwater simulation system was constructed as a tracer test platform. The water simulation system was filled with a porous media system, in which different heterogeneous structures were set to simulate the zonal region and the background medium region. A groundwater simulation solution was injected into the groundwater simulation system to saturate the porous media system, and seepage conditions were established through flow control methods. The tracer suspension is introduced into the inlet of the groundwater simulation system via pulse injection or constant flow rate, and enters the porous media system along with the groundwater simulation solution.
8. The method for identifying groundwater preferential flow paths using microplastics according to claim 1, characterized in that, Sampling points were set up at different spatial locations in the groundwater simulation system, and water samples were collected from each sampling point, including: Multiple sampling points are set in the strip region and the background medium region respectively, and the multiple sampling points in the strip region are symmetrical with the multiple sampling points in the background medium region; A sampling point was set at the outlet of the strip area and the outlet of the background medium area, respectively; Water samples were collected synchronously from each sampling point according to the preset time interval.
9. The method for identifying groundwater preferential flow paths using microplastics according to claim 1, characterized in that, Quantitative analysis of the tracer signals from water samples at each sampling point yielded the content of organic tantalum compounds at each sampling point, including: Each water sample was digested sequentially to prepare a digestion solution; The digestion solution was brought to a final volume to obtain the solution to be tested. The content of organotantalum compounds in the test solution was determined by inductively coupled plasma mass spectrometry.
10. The method for identifying groundwater preferential flow paths using microplastics according to claim 1, characterized in that, Based on the content of organic tantalum compounds at each sampling point, the preferred flow path of microplastics in the groundwater simulation system was determined, including: Based on the change in the content of organotantalum compounds at each sampling point over time, a breakthrough curve for labeled microplastics was constructed. By comparing the characteristic parameters of the penetration curves at different sampling points, the preferred flow path is identified; wherein, the characteristic parameters include at least one of the initial arrival time, peak occurrence time, and peak concentration.