A water-sediment interface research device based on thin film diffusion gradient

Abstract

The application discloses a water-sediment interface research device based on a thin film diffusion gradient, and has the characteristics that the device comprises a simulation tank and a passive sampler; the simulation tank is provided with an opening at one end, and a sediment layer and a liquid layer are sequentially arranged in the tank body from bottom to top; the passive sampler comprises a sampler back plate, a sampling recess is arranged on the surface of the sampler back plate, a hand-held device is arranged at one end of the sampler back plate, and a stabilizer is arranged at the other end of the sampler back plate; the stabilizer is used for vertically placing the sampler in the simulation tank, so that the sampling recess can be in contact with the sediment layer and the liquid layer at the same time; a DGT film layer assembly is detachably attached in the sampling recess; the DGT film layer assembly comprises a binding gel layer, a diffusion gel layer and a filter layer from bottom to top in sequence; the passive sampler further comprises a sampler front plate, a sampling port is arranged on the sampler front plate, and the sampling port is used for accommodating the sampling recess; and the sampler front plate can be closed with the sampler back plate, so as to fix the DGT film layer assembly.

Description

Technical Field

[0001] This application belongs to the field of water pollution monitoring technology, specifically relating to a water-sediment interface research device based on thin film diffusion gradient. Background Technology

[0002] In aquatic environments, pollutants first enter the water body after discharge, readily adsorbing onto the surface of suspended particulate matter and accumulating in sediment through particulate settling, forming a pollution system where water and sediment interact. When external disturbances occur, pollutants in the sediment may be released back into the water, especially water-soluble pollutants, which readily undergo a "sedimentation-resuspension" equilibrium at the water-sediment interface, leading to secondary pollution and posing a threat to the ecological environment and human health. Therefore, quantitative research on the diffusion and migration behavior of pollutants at the water-sediment interface is of great significance.

[0003] Existing studies mainly use methods such as grab sampling to collect water and sediment samples for analysis. This method has several drawbacks: First, grab sampling is complex and costly, and it is difficult to deploy multiple sites simultaneously to obtain high spatial resolution data; second, traditional sampling methods obtain pollutant content at a specific point in time, which cannot reflect the continuous influx, dynamic migration, and multi-media distribution of pollutants at the water-sediment interface; in addition, due to the complex environment of the water-sediment interface, the sampling process is easily affected by disturbances, leading to inaccurate measurement results and making it difficult to quantify the diffusion coefficient and migration capacity of pollutants.

[0004] Diffusive Gradients in Thin Films (DGT), as a passive sampling method, enables in-situ enrichment and effective separation of pollutants, reduces matrix interference, and the measurement results are only related to the mobility of pollutants in the sampling medium and the characteristics of the diffusion film. It requires no complex on-site calibration, is low-cost, simple to operate, and suitable for large-scale simultaneous deployment at multiple sites. However, existing DGT technologies are mostly focused on in-situ measurement devices for single water bodies or soil environments. Published technical solutions mainly include double-sided measurement of probe structures, reusable or variable-morphology structures, or passive sampler structures to achieve sample collection at different depths. None of these solutions address a water-sediment interface pollution diffusion research system that can simulate natural water flow disturbance and integrate sediment and water body simulation.

[0005] Therefore, there is still a lack of a research device that can simulate the water-sediment interface environment, achieve in-situ continuous measurement of pollutants through DGT technology, and combine hydrodynamic disturbance simulation to realize quantitative analysis of the dynamic migration process of pollutants at the water-sediment interface, which involves "sedimentation followed by suspension". It is necessary to develop a water-sediment interface pollution diffusion research device with a reasonable structure, complete functions, and the ability to accurately reflect the migration and diffusion behavior of pollutants. Utility Model Content

[0006] In view of the technological gaps and needs in the aforementioned fields, this utility model provides a water-sediment interface pollution diffusion research device with a reasonable structure, complete functions, and the ability to accurately reflect the migration and diffusion behavior of pollutants. The specific solution is as follows:

[0007] A device for studying water-sediment interfaces based on thin film diffusion gradients, characterized in that it includes: a simulation tank 1 and a passive sampler 5;

[0008] The simulation tank 1 has an opening at one end, and the tank is filled with a sediment layer 3 and a liquid layer 2 from bottom to top.

[0009] The passive sampler 5 is used to insert into the simulation tank 1 for sampling, and is composed of a sampler back plate 6 and a sampler front plate 10 fastened together; a handheld device 61 is provided at one end of the sampler back plate 6, and a sampling groove 63 is provided on the side of the sampler back plate 6 that contacts the sampler front plate 10; the sampler front plate 10 has a frame structure, and a sampling port 11 is provided at the position directly opposite the sampling groove 63, so that the sampling material in the sampling groove 63 can be exposed to the environment.

[0010] A thin-film diffusion gradient membrane assembly is detachably disposed in the sampling groove 63; the thin-film diffusion gradient membrane assembly comprises, from bottom to top: a binding gel layer 7, a diffusion gel layer 8, and a filter layer 9;

[0011] In some preferred embodiments, the passive sampler 5 has a wedge-shaped structure 62 at the other end, which facilitates the insertion of the passive sampler 5 into the sediment in the simulation tank 1.

[0012] In some preferred embodiments, the simulation tank 1 is a rectangular box; the passive sampler 5 is elongated.

[0013] In some preferred embodiments, the diffusion gel layer 8 is an agarose diffusion gel layer with a thickness of 0.8 mm, a length of 15 cm, and a width of 1.8 cm; the agarose mass-volume fraction of the agarose diffusion gel layer is 0.375%.

[0014] In some preferred embodiments, the binding gel layer 7 is an HLB-AG probe binding gel layer with a thickness of 0.8 mm, a length of 15 cm, and a width of 1.8 cm; the HLB-AG probe binding gel layer is composed of 4 g of wet HLB resin particles uniformly dispersed in agarose with a mass-volume fraction of 1.5%.

[0015] In some preferred embodiments, the filter layer 9 is a hydrophilic polytetrafluoroethylene filter membrane with a thickness of 0.11 mm, a length of 16.1 cm, a width of 2.7 cm, and a pore size of 0.45 μm.

[0016] In some preferred embodiments, the passive sampler 5 is made of ABS.

[0017] In some preferred embodiments, the passive sampler 5 has a scale on its side.

[0018] In some preferred embodiments, the simulation tank 1 is also equipped with a stirrer 4 for stirring the liquid layer 2 to simulate natural water flow.

[0019] In some preferred embodiments, the exterior of the simulation tank 1 is provided with a scale for marking and adjusting the volume ratio of the sediment layer 3 and the liquid layer 2.

[0020] In some preferred embodiments, the bonding gel layer 7, the diffusion gel layer 8, and the filter layer 9 are all detachable structures.

[0021] This utility model has at least the following beneficial technical effects:

[0022] This invention, based on thin-film diffusion gradient (DGT) technology, addresses the problems of high cost, inability to deploy multiple points simultaneously, and difficulty in reflecting the dynamic migration and multi-media distribution of pollutants in traditional grab sampling methods. It provides a specialized research device that facilitates the construction of a water-sediment microenvironment, enables the deployment of multiple DGT probes in the same system, and allows for the acquisition of accurate concentration distribution of pollutants at the water-sediment interface without the need for on-site calibration, thereby improving measurement efficiency and data reliability.

[0023] This invention uses a stirrer to simulate river flow conditions and combines this with segmented adsorption measurements by a DGT probe at different time points. It can quantitatively simulate the vertical concentration distribution and temporal migration characteristics of pollutants at the water-sediment interface, clearly explaining the diffusion, deposition, and resuspension processes of pollutants. This overcomes the limitations of traditional methods in quantifying dynamic migration patterns. The device is structurally stable, easy to operate, and can be manufactured using common materials and conventional preparation techniques. Its low cost makes it suitable for large-scale application and provides strong technical support for research on the migration mechanisms and risk assessment of aquatic pollutants. Attached Figure Description

[0024] Figure 1 This is a front view of the apparatus used for studying the water-sediment interface based on the thin film diffusion gradient in this application.

[0025] Figure 2 This is a left view of the apparatus used in this application for studying the water-sediment interface based on the thin film diffusion gradient;

[0026] Figure 3 This is a perspective view of the apparatus used in this application for studying the water-sediment interface based on the thin film diffusion gradient;

[0027] Figure 4 This is a perspective view of the passive sampler of the water-sediment interface research device based on the thin film diffusion gradient in this application;

[0028] Figure 5 This is a structural diagram of the passive sampler of the water-sediment interface research device based on thin film diffusion gradient in this application;

[0029] Figure 6 This is a spatiotemporal distribution characteristic diagram of neonicotinoids in the water-sediment interface research device based on thin film diffusion gradient in this application;

[0030] Wherein: 1-simulation tank, 2-liquid layer, 3-sediment layer, 4-stirrer, 5-passive sampler, 6-sampler back plate, 61-handheld device, 62-wedge structure, 63-sampling groove, 7-binding gel layer, 8-diffusion gel layer, 9-filter layer, 10-sampler front plate, 11-sampling port. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0032] The following is in conjunction with the appendix Figure 1-5 The present application provides a more detailed description of the water-sediment interface research apparatus based on thin film diffusion gradient.

[0033] like Figure 1-3 As shown, this application discloses a water-sediment interface research device based on thin film diffusion gradient, including a simulation tank 1 and a passive sampler 5.

[0034] The simulation tank 1 is a rectangular box structure with an opening at one end. Inside the tank, there is a sediment layer 3 and a liquid layer 2. The sediment layer 3 is located at the bottom of the tank and serves to hold deposited pollutants; the liquid layer 2 is located above the sediment layer and serves to simulate the overlying water environment. During the experiment, the pollutants to be tested can be added to the liquid layer, allowing them to diffuse in the water and migrate downwards to the sediment layer, thus simulating the interfacial processes.

[0035] The simulation tank is made of high-strength transparent material, facilitating observation of the distribution and migration of pollutants inside. Graduation marks can be installed on the outer wall of the tank to indicate the height of the sediment and liquid layers, aiding in adjusting the volume ratio. An agitator 4 can also be installed inside the tank to stir the liquid layer, simulating a natural water flow environment.

[0036] like Figure 4 and Figure 5 As shown, the passive sampler 5 is a long strip structure made of ABS (acrylonitrile-butadiene-styrene) and can be inserted into the simulation tank 1 for sampling. It is composed of a sampler back plate 6 and a sampler front plate 10 that are fastened together. The sampler back plate 6 is provided with a sampling groove 63 for installing a thin film diffusion gradient (DGT) membrane module; one end is provided with a handheld device 61, and the other end has a wedge structure 62, which facilitates insertion into the sediment layer, so that the membrane module can contact the liquid layer and the sediment layer simultaneously to achieve synchronous sampling.

[0037] The sampler front panel 10 has a frame structure with a sampling port 11 at the position corresponding to the sampling groove 63, exposing part of the membrane module to the environment. After the sampler front panel and the sampler back panel are mechanically fastened together, they serve to press and fix the membrane module, preventing displacement and damage.

[0038] The DGT membrane assembly is detachably installed in the sampling recess 63 and includes, from bottom to top, a binding gel layer 7, a diffusion gel layer 8, and a filter layer 9.

[0039] Specifically, the binding gel layer 7 is an HLB-AG probe binding gel layer, and the preparation method is as follows:

[0040] S11. Place the HLB powder in an empty SPE tube, fully activate the HLB adsorbent particles with methanol for 30 minutes, then rinse with ultrapure water, and after letting it dry naturally, weigh 4g of wet HLB resin for later use.

[0041] S12. Weigh 0.6g of agarose powder and add it to 40mL of ultrapure water. Pour the mixture into a wide-mouth bottle and heat it in a microwave oven. During the heating process, check the contents of the bottle frequently and shake it to mix it from time to time until the agarose is completely dissolved and the solution is clear and transparent.

[0042] S13. Add 4g of wet HLB resin to the dissolved agarose sol, shake to mix, and form a homogeneous mixed sol.

[0043] S14. Inject the mixed sol between two glass plates preheated to 60°C. Three sides of the glass plates are padded with 0.8mm thick plastic gaskets, and the outer sides are clamped and fixed with dovetail clips.

[0044] S15. Place the clamped glass plate at room temperature to cool. After the solution solidifies into a gel, open the glass plate and use a stainless steel cutter to cut the gel into rectangular sheets 15cm long and 1.8cm wide.

[0045] S16. Immerse the cut gel sheets in 0.01 mol / L NaCl solution and store at 4°C for later use.

[0046] Diffusion gel layer 8 is an agarose diffusion gel layer, and its preparation method is as follows:

[0047] S21. Weigh 0.15g of agarose powder, add it to 40mL of ultrapure water, shake well, and pour it into a wide-mouthed glass bottle.

[0048] S22. Place the wide-mouthed glass bottle in a microwave oven and heat it, taking it out and shaking it occasionally during the heating process, until the agarose is completely dissolved and the solution is clear and transparent.

[0049] S23. Inject the dissolved agarose sol between two glass plates preheated to 60°C. Place 0.8mm thick plastic gaskets on three sides of the glass plates to ensure uniform gel thickness.

[0050] S24. Use dovetail clips to clamp the glass plate and let it cool at room temperature until the solution solidifies to form a gel.

[0051] S25. Open the glass plate and use a stainless steel cutter to cut the gel into rectangular sheets 15cm long and 1.8cm wide.

[0052] S26. Immerse the cut gel sheets in 0.01 mol / L NaCl solution and store at 4°C for later use.

[0053] The filter layer 9 is a hydrophilic polytetrafluoroethylene (wwPTFE) filter membrane with a thickness of 0.11 mm, a length of 16.1 cm, a width of 2.7 cm, and a pore size of 0.45 μm. This filter membrane has good hydrophilicity and chemical stability, while protecting the underlying binding gel layer 7 and diffusion gel layer 8.

[0054] It is important to note that the sampler backplate 6 and sampler frontplate 10 should be rinsed three times with methanol and ultrapure water respectively to ensure that the surfaces are clean and free of contaminants, thus avoiding interference with the experimental results. During assembly, first use tweezers to carefully clamp the pre-prepared HLB-AG binding gel layer 7 onto the sampling groove 63 of the sampler backplate 6, ensuring that the binding gel layer adheres smoothly without air bubbles or wrinkles. Then, place the AG diffusion gel layer 8 and the wwPTFE filter membrane 9 on the binding gel layer 7 in sequence, paying attention to aligning the edges of the three membrane materials to maintain the integrity and stability of the membrane structure. After completing the membrane assembly, cover the sampler frontplate 10 onto the sampler backplate 6, and firmly clamp the front plate and backplate together using a mechanical clamping structure to fix the DGT membrane assembly, forming a stable HLB-DGT, i.e., the passive sampler 5. The assembled HLB-DGT passive sampler 5 needs to be immersed in 0.01 mol / L NaCl solution and stored at 4°C for later use to maintain the hydration of the membrane layer and ensure good adsorption performance and structural stability in subsequent experiments.

[0055] In some embodiments, the passive sampler 5 has a scale on its side to indicate the sampler insertion depth, which facilitates precise control of the position of the DGT membrane assembly in the liquid layer 2 and the sediment layer 3 during the experiment, enabling stratified collection and analysis of pollutant concentration distribution at different depths.

[0056] In some embodiments, sediment layer 3 can also be filled with different types of sediment samples, such as naturally collected bottom sediment or standard-prepared simulated bottom sediment, and the thickness can be adjusted according to research needs. Liquid layer 2 is experimental water, which can be configured as river water, lake water or other experimental water according to the water quality requirements of the simulated object, and can also be added to conduct migration and diffusion experiments of target pollutants.

[0057] Application Examples

[0058] In this embodiment, a water-soil ratio of 1:1 was first prepared. 8 kg of wet sediment collected from a river section in Guangzhou University Town was added to a simulated tank measuring 25 cm * 15 cm * 30 cm with 4.125 L of tap water to form a water-sediment system, which was then aged in a shaded and dark place for 30 days. After aging, 8.25 mL of a 100 mg / L neonicotinoid stock solution was added to the aqueous phase of the system. The target compounds included five neonicotinoid pesticides: imidacloprid (IMI), thiamethoxam (THM), thiamethoxam (THA), acetamiprid (ACE), and thiamethoxam (CLO).

[0059] During the experiment, a stirrer was used to uniformly stir the sample at 150 rpm without contacting the sediment surface. The fabricated passive sampler was then vertically inserted into the water-sediment system. The anchor points and depths of the DGT membrane module insertion into each layer were set as follows: aqueous layer 2.0-2.0-2.0-2.0 cm, totaling 8 cm; sediment layer 2.0-2.0-2.0 cm, totaling 6 cm, to achieve stratified determination of target pollutants in different water and sediment layers. Subsequently, the probe (in triplicate) was retrieved on days 1, 3, 5, 7, 10, and 14 after insertion. The bound gel within the probe was completely extracted, cut into segments according to the set anchor points, and the concentration of neonicotinoid compounds was determined using standard methods (organic solvent or ultrasound-assisted extraction).

[0060] Figure 6 Figures a–e show the spatiotemporal distribution characteristics of five neonicotinoids in a water-sediment system under simulated river conditions. DGT probe results indicate significant differences in the concentration distribution of the five compounds between the aqueous phase and sediments. In the aqueous phase, the concentration generally decreases with increasing depth, with the highest concentration appearing in the 0–2 cm layer. In the sediment layer, the five neonicotinoids rapidly migrate and accumulate at the surface in the first 24 hours, and their concentration decreases sharply with increasing depth, indicating that they mainly migrate and accumulate from the aqueous phase to the surface sediments, while the adsorption and diffusion capacity of deep sediments is limited.

[0061] Further comparison Figure 6 As can be seen from a–e, the five neonicotinoids showed certain differences in absolute concentration and trend. IMI and ACE showed the most significant decrease in water concentration and the largest accumulation of sediment throughout the monitoring period; the water concentrations of THM, THA, and CLO decreased more gradually. THM and CLO decreased rapidly in the early stage and then tended to stabilize, while THA decreased steadily and at a relatively slow rate, which is related to the water solubility and adsorption of each substance.

[0062] To analyze the adsorption equilibrium time, Figure 6 In f, the concentration distribution curves over time were plotted based on an aqueous phase depth of 2 cm. The figure shows that the IMI concentration decreased the most, continuing to decrease over 168 hours; THM decreased rapidly in the first 24 hours and then tended to stabilize; THA decreased more slowly but steadily. Both THA and THM reached equilibrium earlier and were the two compounds with the highest remaining amount in the aqueous phase after equilibrium; ACE and CLO showed similar decreasing trends and concentrations after equilibrium.

[0063] Furthermore, sediments exhibited a significant "filtration" or "retention" effect on all five neonicotinoids, with the highest concentrations observed in the 0–2 cm surface layer, decreasing rapidly with depth. This suggests that they primarily accumulate in surface sediments, with limited migration to deeper layers, potentially posing a risk of long-term surface pollution accumulation. From an environmental risk perspective, IMI tends to rapidly accumulate in surface sediments; THM and THA have the highest concentrations in water but exhibit slow deposition and degradation rates, easily leading to long-term exposure of water bodies. While ACE and CLO concentrations are low after equilibrium, their migration behavior is consistent, indicating a need to monitor their combined pollution effects.

[0064] Overall, the concentrations of all target compounds decreased rapidly within the first 72 hours, then stabilized after 168 hours, indicating that the system had reached a relative equilibrium between water and sediment. The concentrations of various compounds in the sediment remained low for the first 24 hours, then gradually increased in the shallow layers, reaching a plateau or peak between 168 and 240 hours. IMI, THA, and ACE showed a slight decrease at 336 hours, suggesting a certain degree of natural decay or degradation. These test results are consistent with natural phenomena, demonstrating the effectiveness of this research device in practice.

[0065] Furthermore, the results also reveal that the five neonicotinoids exhibit a typical distribution and migration pattern in this simulation system: initial input, rapid accumulation, stable concentration, and slow degradation. They mainly accumulate in surface sediments and may pose a potential risk to aquatic ecological safety. These findings provide important evidence for subsequent research on the migration and transformation behavior of neonicotinoid pesticides in the aquatic environment and for ecological risk assessment.

[0066] It should be understood that the orientations or positional relationships such as "center," "longitudinal," "lateral," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" used in the description of this application are described only based on the orientations or positional relationships shown in the accompanying drawings, for the purpose of facilitating the explanation and simplification of this application, and are not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation, and should not be construed as limiting the scope of protection of this application. The above descriptions are merely specific embodiments of this application, and the scope of protection of this application is not limited thereto. Any variations, equivalent substitutions, or improvements that are readily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application, and the scope of protection of this application should be determined by the scope defined in the appended claims.

Claims

1. A device for studying water-sediment interfaces based on thin-film diffusion gradients, characterized in that, include: Simulation tank (1) and passive sampler (5); The simulation tank (1) has an opening at one end, and a sediment layer (3) and a liquid layer (2) are arranged sequentially from bottom to top inside the tank. The passive sampler (5) is used to insert into the simulation tank (1) for sampling. It is composed of a sampler back plate (6) and a sampler front plate (10) fastened together. A handheld device (61) is provided at one end of the sampler back plate (6). A sampling groove (63) is provided on the side of the sampler back plate (6) that contacts the sampler front plate (10). A sampling port (11) is provided on the sampler front plate (10) directly opposite the sampling groove (63) so that the sampling material in the sampling groove (63) can be exposed to the environment. A thin film diffusion gradient membrane assembly is detachably disposed in the sampling groove (63); the thin film diffusion gradient membrane assembly has, from bottom to top, a binding gel layer (7), a diffusion gel layer (8) and a filter layer (9).

2. The apparatus according to claim 1, characterized in that, The simulation tank (1) is a rectangular box; The passive sampler (5) is long and narrow, with a wedge-shaped structure (62) at the other end, which facilitates the insertion of the passive sampler (5) into the sediment in the simulation tank (1).

3. The apparatus according to claim 1, characterized in that, The binding gel layer (7) is an HLB-AG probe binding gel layer with a thickness of 0.8 mm, a length of 15 cm, and a width of 1.8 cm. The HLB-AG probe binding gel layer is composed of 4 g of wet HLB resin particles uniformly dispersed in agarose with a mass-volume fraction of 1.5%.

4. The apparatus according to claim 1, characterized in that, The diffusion gel layer (8) is an agarose diffusion gel layer with a thickness of 0.8 mm, a length of 15 cm, and a width of 1.8 cm; the agarose mass-volume fraction of the agarose diffusion gel layer is 0.375%.

5. The apparatus according to claim 1, characterized in that, The filter layer (9) is a hydrophilic polytetrafluoroethylene filter membrane with a thickness of 0.11 mm, a length of 16.1 cm, a width of 2.7 cm, and a pore size of 0.45 μm.

6. The apparatus according to claim 1, characterized in that, The passive sampler (5) is made of ABS.

7. The apparatus according to claim 1, characterized in that, The passive sampler (5) has a scale on its side.

8. The apparatus according to claim 1, characterized in that, The simulation tank (1) is also equipped with a stirrer (4) for stirring the liquid layer (2) to simulate natural water flow.

9. The apparatus according to claim 1, characterized in that, The simulation tank (1) is equipped with scales on the outside for marking and adjusting the volume ratio of the sediment layer (3) and the liquid layer (2).

10. The apparatus according to claim 1, characterized in that, The binding gel layer (7), the diffusion gel layer (8), and the filter layer (9) are all detachable structures.

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