Experimental device for simulating migration of micro-plastic in undisturbed soil column under rainfall condition and application

Abstract

The invention provides an experimental device for simulating migration of micro-plastic in an undisturbed soil column under a rainfall condition and application, and belongs to the technical field of soil micro-plastic migration. Comprising a Markov bottle and a simulated soil column, the right side of the upper end of the Markov bottle is provided with a water inlet with a stainless steel cover, and the left side of the upper end of the Markov bottle is provided with an exhaust pipe with scale marks on the surface; the bottom of the Markov bottle is higher than the top of the simulated soil column rainfall tray; the simulated soil column comprises a rainfall disc and a column body arranged below the rainfall disc, the rainfall disc is of a dial type, exhaust holes are formed in the surface of the rainfall disc, a needle head is arranged in the rainfall disc, and the rainfall disc is connected with the upper end of the column body through a flange plate; the column body is divided into an air layer, an undisturbed soil column filling layer and a quartz sand layer which are sequentially connected through flange plates, a water outlet is formed in the bottom of the flange plate at the lower end, and the column body is a hollow cylinder with an upper opening and a lower opening.

Description

Technical Field

[0001] The invention relates to an experimental device for migrating microplastics in an original soil column under simulated rainfall conditions and application thereof, belonging to the technical field of soil microplastic migration. Background Art

[0002] With the continuous development of modern agriculture, plastic products are widely used in agricultural practices such as farming, fertilization, and mulching. These plastic products transported to farmland may be decomposed into microplastic particles (<5mm) with small particle size and strong migration ability under the influence of ultraviolet light, weathering, and human activities.

[0003] Under the influence of natural factors and human activities, microplastics may absorb pollutants in the environment and migrate underground with them, posing a potential risk to groundwater pollution. However, the fate of microplastics in the soil environment is still unclear. Therefore, exploring the vertical migration characteristics of microplastics in soil is the key content of studying the final fate of microplastics. Soil properties are one of the important factors affecting the vertical migration of microplastics. Soil column experiments are often used to simulate the migration of microplastics in soil, but the columns of most existing soil column devices are complete and non-detachable columns. Most of the media filled in the column are quartz sand or reshaped soil. This ideal laboratory condition is very different from the actual soil environment. For real soil, an environmental medium with more complex components, there is a lack of research equipment, especially for its vertical migration characteristics. Rainfall is also an important factor affecting the vertical migration of microplastics in soil. Artificial simulated rainfall can make up for the irregularity of actual rainfall weather and facilitate scientific research. At present, most simulated rainfall devices use nozzles. Nozzle devices are more suitable for large-diameter columns, which have the problems of high experimental cost, complex experiments and high power consumption. In addition, many existing soil column devices used to study the migration of microplastics do not distribute water evenly and cannot effectively simulate actual rainfall conditions.

[0004] Therefore, there is an urgent need in the art for an experimental device and application that can improve the migration of microplastics in soil columns under simulated rainfall conditions and the migration of microplastics in original soil columns under simulated rainfall conditions that are not consistent with actual conditions. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the microplastic migration experiment in the laboratory in the prior art is too far away from the actual environment and the predictive effect is poor.

[0006] In order to achieve the purpose of solving the above-mentioned problems, the technical solution adopted by the present invention is to provide an experimental device and application for the migration of microplastics in an original soil column under simulated rainfall conditions.

[0007] The first aspect of the present invention provides an experimental device for the migration of microplastics in an original soil column under simulated rainfall conditions, comprising a Martens flask and a simulated soil column; a water inlet is provided on the right side of the upper end of the Martens flask, with a stainless steel cover, and an exhaust pipe is provided on the left side of the upper end of the Martens flask, and scale lines are provided on the surface; the bottom of the Martens flask is higher than the top of the rainfall tray of the simulated soil column; the simulated soil column comprises a rainfall tray and a column arranged below the rainfall tray, the rainfall tray is a needle tray type, with exhaust holes on its surface and a needle inside, and the rainfall tray is connected to the upper end of the column through a flange; the column is divided into three parts: an air layer, an original soil column filling layer and a quartz sand layer, which are connected in sequence through a flange, a water outlet is provided at the bottom of the flange at the lower end, and the column is a hollow cylinder with upper and lower openings.

[0008] Preferably, the Martens flask is connected to the simulated soil column via a valve and a plastic hose.

[0009] Preferably, a rubber sheet is provided in the middle of the flange of the rain tray to facilitate the replacement and cleaning of the needle.

[0010] A second aspect of the present invention provides an application of an experimental device for simulating the migration of microplastics in an undisturbed soil column under rainfall conditions, comprising the following steps:

[0011] Step 1, pouring simulated rainwater into the Martens flask and recording the scale;

[0012] Step 2, open the exhaust hole above the rain tray, open the valve, and after the Martens flask is filled with water into the rain tray, close the valve and block the exhaust hole;

[0013] Step 3, filling the original soil column filling layer of the column;

[0014] Step 4: Evenly spread the microplastics on the surface of the original soil column;

[0015] Step 5, connecting the Martens flask and the simulated soil column through a plastic hose;

[0016] Step 6, open the valve and start timing, and read the amount of water level drop in a group of Martens flasks per unit time;

[0017] Step 7: The water from the simulated soil column is collected in a beaker.

[0018] Preferably, in step 3, vaseline is used for lubrication before filling the original soil column to improve the smoothness of the inner wall, reduce the friction between the inner wall and the soil sample and prevent the generation of side wall flow;

[0019] Preferably, in step 3, before filling the original soil column, a 2 cm thick quartz sand layer is filled at the lower end of the column;

[0020] Preferably, in step 5, the Martens flask is placed at a position where the bottom of the ventilation pipe is higher than the upper end of the rainfall tray.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The rainfall pan of the simulated soil column makes rainfall more uniform, and the column of the simulated soil column leaves a blank rainfall part on the top, which can better simulate the natural rainfall climate and more realistically simulate the migration of microplastics under natural climate conditions.

[0023] 2. The column of the simulated soil column is divided into three sections and connected by flanges, which facilitates the transfer of the original soil column into the column, avoids compression when filling the original soil column, retains the real soil pore structure as much as possible, and better simulates the migration of microplastics in the actual soil environment.

[0024] 3. The quartz sand layer at the bottom of the simulated soil column can avoid clogging the drain outlet and prevent water from flowing poorly in the column. The flange at the connection has a built-in silicone pad with good sealing to prevent water leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a Malvern flask for simulating the migration of microplastics in soil under rainfall provided by an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of the structure of a simulated soil column for simulating the migration of microplastics in soil under rainfall provided by an embodiment of the present invention;

[0027] Figure 3 A diagram showing a filling method of a simulated soil column in an embodiment of the present invention;

[0028] Figure 4 The migration distribution diagram of 80μm polystyrene microplastics in the original soil column under different rainfall conditions;

[0029] Figure 5 This is the migration distribution diagram of polystyrene microplastics with mixed particle sizes of 20 / 80μm ​​in the original soil column when the rainfall was 2160mm. Figure 5 (a) is the distribution diagram of polystyrene microplastics in the original soil column (every 2 cm). Figure 5 (b) The proportion of polystyrene microplastics of different sizes (20 / 80 μm) in each soil column.

[0030] Figure numerals: 1—Marsh flask; 2—simulated soil column; 3—rain tray; 4—column; 101—stainless steel cover; 102—exhaust pipe; 103—valve; 301—valve; 302—rain needle; 303—exhaust hole; 401—flange; 402—drain outlet; 403—silicone pad. DETAILED DESCRIPTION

[0031] In order to make the present invention more clearly understood, a preferred embodiment is described in detail with reference to the accompanying drawings as follows:

[0032] Figure 1 A schematic diagram of the structure of a Malchnitz flask for simulating the migration of microplastics in soil under rainfall provided in an embodiment of the present invention, wherein the experimental device for simulating the migration of microplastics in soil under rainfall comprises a Malchnitz flask 1, which is made of plexiglass and has a volume of 5L; a water inlet is provided at the upper end of the Malchnitz flask 1, and a stainless steel cover 101 is provided on it. When the water supply of the Malchnitz flask 1 is insufficient, water can be manually added to the Malchnitz flask through the rubber stopper 101; an exhaust pipe 102 is provided on the left side of the upper end of the Malchnitz flask 1; and scale lines are provided on its surface.

[0033] Figure 2 A schematic structural diagram of a simulated soil column for simulating the migration of microplastics in soil under rainfall provided in an embodiment of the present invention, wherein the simulated soil column comprises a rainfall plate 3 and a column 4. The column 4 is a hollow cylinder with openings at the top and bottom, an inner diameter of the column of 50 mm, and a total height of 50 cm. The column is divided into three parts for easy installation of the original soil column. The rainfall plate 3 and the column 4 are connected by a flange 401.

[0034] The rain disk 3 is a needle disk type, with a valve 301 and an exhaust hole 303 at the upper end, and a rain needle 302 inside. The rain needle 302 is vertically installed in the medical rubber plug, and a silicone sheet is padded in the flange of the rain disk 3 to facilitate replacement and cleaning of the needle.

[0035] The experimental method of the above-mentioned experimental device for simulating the migration of microplastics under rainfall, the specific implementation method includes the steps of:

[0036] A. Pour simulated rainwater into the Malchow flask 1 and record the scale;

[0037] B. Open the exhaust hole 303 above the rain tray 3 and open the valve 301. After the Malchow flask is filled with water into the rain tray, close the valve 301 and block the exhaust hole 303.

[0038] C. Filling the original soil column filling layer of the column into the original soil column;

[0039] D. Spread the microplastics evenly on the surface of the original soil column;

[0040] E. Connecting the Malchnitz flask 1 and the simulated soil column 2 via a plastic hose;

[0041] F. Open the valve and start timing, reading the amount of water level drop in one group of Malvern flasks per unit time;

[0042] G. The water from the simulated soil column 2 is collected in a beaker.

[0043] In the step C, vaseline is used for lubrication before filling the original soil column to improve the smoothness of the inner wall, reduce the friction between the inner wall and the soil sample and prevent the generation of side wall flow;

[0044] In step C, before filling the original soil column, a 2 cm thick quartz sand layer is filled at the lower end of the column;

[0045] In step E, the Martens flask is placed at a position where its bottom is higher than the top of the rainfall tray 3 .

[0046] The experimental method and effects of the present invention are described in detail below through two specific embodiments.

[0047] Example 1

[0048] This example uses 80μm polystyrene microplastic powder to conduct column migration experiments under different rainfall conditions (540mm, 1080mm, 2160mm). Figure 3 As shown, the simulated soil column is a plexiglass column with a height of 50 cm and an inner diameter of 5 cm. The simulated soil column 1 is divided into an air layer A, an original soil column filling layer B and a quartz sand layer C from bottom to top. After the bottom flange and silicone pad are installed, a layer of stainless steel filter is laid and a 2 cm quartz sand layer (C) is loaded. After applying a layer of vaseline on the inner wall of the column, the original soil column is filled into the column. The original soil column is 30 cm long. A layer of 30 mg of polystyrene microplastic powder with a diameter of 80 μm is evenly laid on the surface of the original soil layer, and then the flange, silicone pad, and flange are placed in turn to connect with the rain plate. The air layer (A) is 18 cm long.

[0049] Pour simulated rainwater into the Martens flask to 45cm from the scale line and record it. Place the Martens flask flush with the top of the rainfall tray, and use a plastic hose to connect the Martens flask and the rainfall tray. There is a valve in the middle to control the amount of rainfall, forming a sealed connection between the Martens flask-pipeline-rainfall tray, thereby ensuring stable and uniform rainfall. Open the exhaust hole above the rainfall tray and open the valve. After the rainfall tray is filled with water, close the valve and block the exhaust hole. Adjust the rainfall intensity to 80mm / h through the valve, start timing and record the drop in the water level of the Martens flask, and collect the outlet water through a beaker at the outlet. Close the valve when the rainfall reaches the target amount (540mm, 1080mm, 2160mm). Microplastics penetrate downward under the action of rainwater, realizing the simulation of the migration of microplastics in the soil. After the simulated rainfall is over, the simulated soil column is disassembled to extract the microplastics and observe the vertical migration of microplastics in the original soil column. The results are as follows Figure 4 As shown in the figure, the recovery rate of microplastics can reach more than 70%, and the recovery rate is stable. Figure 4 It can be seen that as rainfall increases, the amount of microplastics retained in the surface layer decreases and they gradually migrate to deeper layers.

[0050] Example 2

[0051] In this case, polystyrene microplastic powder with mixed particle size (1:1) was used to conduct column migration experiments under different rainfall conditions (rainfall was 540mm, 1080mm, and 2160mm, respectively). A simulated soil column of the same scale as in Example 1 was used. After the original soil layer (30cm) was filled, a layer of polystyrene microplastic powder with mixed particle size (30mg 20μm+30mg 80μm) was evenly laid on the surface, and then the experimental devices were connected in sequence. The migration of microplastics with mixed particle size in the soil column is closer to the migration of microplastics in the natural environment. Pour simulated rainwater into the Malchnitz flask to 45cm on the scale line and record it. Open the vent above the rain tray and open the valve. After the rain tray is filled with water, close the valve and block the vent. Adjust the rainfall intensity to 80mm / h through the valve, start timing and record the drop in the water level of the Malchnitz flask, and collect the outlet water through the beaker at the outlet. Close the valve when the rainfall reaches 2160mm. After the simulated rainfall ended, the simulated soil column was disassembled to extract microplastics and observe the vertical migration of microplastics of mixed particle sizes in the original soil column. Figure 5 As shown. Figure 5 (a) It can be seen that microplastics of different particle sizes will migrate downward under the influence of rainwater. Compared with 80μm microplastics, 20μm microplastics migrate to deeper positions. Figure 5 As can be seen in (b), compared with the surface soil (0-8cm), the proportion of microplastics of 20μm in the deep soil is higher.

[0052] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An experimental device for simulating the migration of microplastics in an undisturbed soil column under rainfall conditions, characterized in that: It comprises a Martens flask and a simulated soil column; a water inlet is arranged on the right side of the upper end of the Martens flask, and a stainless steel cover is provided; an exhaust pipe is arranged on the left side of the upper end of the Martens flask, and scale lines are provided on the surface; the bottom of the Martens flask is higher than the top of the simulated soil column rainfall dish; the simulated soil column comprises a rainfall dish and a column arranged below the rainfall dish, the rainfall dish is a needle-disc type, and has an exhaust hole on its surface and a needle head inside, and the rainfall dish is connected to the upper end of the column through a flange; the column is divided into three parts, namely, an air layer, an original soil column filling layer and a quartz sand layer, which are connected in turn through a flange, a water outlet is arranged at the bottom of the flange at the lower end, and the column is a hollow cylinder with upper and lower openings.

2. The experimental device for the migration of microplastics in an undisturbed soil column under simulated rainfall conditions as claimed in claim 1, characterized in that: The Martens flask is connected to the simulated soil column through a valve and a plastic hose.

3. The experimental device for the migration of microplastics in an undisturbed soil column under simulated rainfall conditions as claimed in claim 1, characterized in that: A rubber sheet is padded in the middle of the flange of the rain-falling plate.

4. Application of an experimental device for simulating the migration of microplastics in an undisturbed soil column under rainfall conditions, characterized in that: The following steps are involved: Step 1, pouring simulated rainwater into the Martens flask and recording the scale; Step 2, open the exhaust hole above the rain tray, open the valve, and after the Martens flask is filled with water into the rain tray, close the valve and block the exhaust hole; Step 3, filling the original soil column filling layer of the column; Step 4: evenly spread the microplastics on the surface of the original soil column; Step 5, connecting the Martens flask and the simulated soil column through a plastic hose; Step 6, open the valve and start timing, and read the amount of water level drop in a group of Malvern flasks per unit time; Step 7: The water from the simulated soil column is collected in a beaker.

5. The use of the experimental device for the migration of microplastics in an undisturbed soil column under simulated rainfall conditions as claimed in claim 4, characterized in that: In the step 3, vaseline is used for lubrication before filling the original soil column to improve the smoothness of the inner wall, reduce the friction between the inner wall and the soil sample and prevent the generation of side wall flow.

6. The use of the experimental device for the migration of microplastics in an undisturbed soil column under simulated rainfall conditions as claimed in claim 4, characterized in that: In step 3, before filling the original soil column, a 2 cm thick quartz sand layer is filled at the lower end of the column.

7. Use of the experimental device for the migration of microplastics in an undisturbed soil column under simulated rainfall conditions as claimed in claim 4, characterized in that: In step 5, the bottom of the Martens flask is higher than the top of the rainfall dish.

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