Soil trace metal element biological effective state extraction device and determination method

Abstract

The invention relates to the technical field of soil detection, in particular to a soil trace metal element biological effective state extraction device and a determination method.The soil trace metal element biological effective state extraction device comprises a support, a horizontally-arranged bearing plate is fixedly connected to the center of the support, and cylindrical diffusion pools in a linear array are arranged on the bearing plate; the cylindrical diffusion pool is internally and fixedly connected with a root system simulation pipe, the root system simulation pipe is located in the center of the diffusion pool and is cylindrical, the pipe wall of the root system simulation pipe is provided with holes, the hole diameter is 0.5 mm, and the pipe wall of the root system simulation pipe is wrapped with a layer of filter membrane with the hole diameter of 0.45 mu m. The diffusion and migration process of effective metal elements in the soil and the influence of root exudates on the process can be well simulated, the method is more suitable for extracting the biological effective state of the soil trace heavy metal elements, and accurate measurement of the effective state content of the soil trace heavy metal elements and accurate prediction of absorption of the plant trace heavy metal elements are more facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of soil detection, and in particular to a device for extracting biologically effective trace metal elements in soil and a method for determining the same. Background Art

[0002] The low effectiveness of trace metal elements in soil (such as copper, zinc, iron, manganese, etc.) is the main reason that limits the absorption of trace metal elements by crop roots and leads to low content of edible tissue of crops, which in turn threatens human health.

[0003] Accurately assessing the bioavailability of trace metal elements in the soil is crucial for improving their bioavailability through scientific and rational field management to increase crop seed content and thereby alleviate the human body's "hidden hunger."

[0004] In the prior art, the determination of the biologically effective state of trace metal elements in soil mainly adopts DGT technology. However, in soils with low trace metal elements, there is still a large deviation between the crop absorption predicted by DGT technology and the measured value. On the one hand, it is because the strong adsorption and fixation effect of the soil makes it difficult for trace metal elements to diffuse and migrate from the soil body to the DGT adsorption layer, resulting in a large deviation between the predicted value and the measured value. On the other hand, DGT technology ignores the role of root secretions and rhizosphere microbial metabolites such as amino acids and citric acid on the migration and transformation of soil zinc, resulting in a low predicted value.

[0005] In summary, the existing technology cannot guarantee the extraction efficiency and measurement accuracy when determining the biologically effective state of trace metal elements in soil. Summary of the invention

[0006] The purpose of the present invention is to provide a device for extracting biologically effective trace metal elements in soil and a method for determining the same, so as to solve the problems raised in the above-mentioned background technology.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A biologically effective extraction device for trace metal elements in soil, comprising a support, a horizontally arranged carrying plate is fixedly connected at the center of the support, a cylindrical diffusion pool in a linear array is arranged on the carrying plate, a root system simulation tube is fixedly connected in the cylindrical diffusion pool, the root system simulation tube is located in the center of the diffusion pool, is cylindrical, has a tube wall with holes, and the hole diameter is 0.5mm, and a layer of 0.45μm pore size filter membrane is wrapped outside the tube wall of the root system simulation tube, and the tube wall hole diameter and the outer filter membrane are used to ensure that soil particles will not pass through the root system simulation tube, while small molecules, ions, etc. can diffuse through and enter the root system simulation tube;

[0009] A chelating agent supply bottle is arranged in the bracket and above the cylindrical diffusion pool, a first delivery hose is fixedly installed at the bottom of the chelating agent supply bottle, a clamping top cover is arranged at the top of the cylindrical diffusion pool, a top cover connector is arranged at the top of the clamping top cover, and the bottom of the first delivery hose and the top cover connector are fixedly installed.

[0010] Preferably, the inner diameter of the root simulation tube is 1 cm, the inner diameter of the cylindrical diffusion pool is 2.5 cm, and the cavity between the inner surface of the cylindrical diffusion pool and the outer surface of the root simulation tube is used to load the soil to be tested.

[0011] Preferably, the cylindrical diffusion cell is made of transparent organic glass, and has a thickness of 3 mm and a height of 2.5 cm.

[0012] Preferably, a hanging rack in a linear array is fixedly connected to the top of the inner wall of the bracket, and the chelating agent supply bottle is hung on the hanging rack.

[0013] Preferably, a receiving bottle is provided at the bottom of the inner wall of the bracket, a bottom joint is provided at the bottom of the cylindrical diffusion tank, a second delivery hose is installed on the bottom joint, and the bottom of the second delivery hose extends to the interior of the receiving bottle, which is used to transport the solution passing through the root simulation tube to the interior of the receiving bottle.

[0014] Preferably, a first speed regulating valve is provided on the first delivery hose, and a second speed regulating valve is provided on the second delivery hose.

[0015] A method for determining the biologically effective state of trace metal elements in soil comprises the following steps:

[0016] S1. Collect the soil sample to be tested, add water to the sample that has passed the 1 mm sieve to the maximum field water holding capacity, soak it and set it aside;

[0017] S2, placing the wetted sample in step S1 into a cylindrical diffusion cell, ensuring that the soil is in full contact with the filter membrane on the outer layer of the root simulation tube, opening the first speed regulating valve at the upper end of the cylindrical diffusion cell, allowing the chelating agent in the chelating agent supply bottle to enter the root simulation tube and be flush with the soil surface, and then closing the first speed regulating valve;

[0018] S3, then open the first speed regulating valve and the second speed regulating valve to ensure that the liquid level in the root system simulation tube is always level with the soil surface, and the liquid flowing out of the root system simulation tube can enter the receiving bottle;

[0019] S4. After diffusion extraction, close the first speed regulating valve at the upper end of the cylindrical diffusion pool, and adjust the second speed regulating valve at the lower end of the cylindrical diffusion pool to allow all the solution in the root simulation tube to quickly flow into the receiving bottle;

[0020] S5. Transfer the solution in the receiving bottle directly or after concentration into a volumetric flask, make up the volume with a chelating agent or ultrapure water, and record the fixed volume; pass the solution in the volumetric flask through a 0.45 μm pore size filter membrane, and determine the trace metal content by graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry;

[0021] The trace metal element content is calculated using the following formula:

[0022]

[0023] Among them, Y is the content of trace metal elements in the soil, C is the trace metal content, V is the volume of the volumetric flask, and m is the mass of the soil loaded.

[0024] Preferably, in the step S1, adding water to the soil sample to be tested to the maximum field water holding capacity can make the soil reach a water pre-saturated state, which is used to provide optimal moisture conditions for the diffusion and migration of trace metal elements in the soil to ensure the diffusion extraction efficiency, and the immersion time is 24 hours.

[0025] Preferably, in step S2, the chelating agent is an artificially prepared root exudate analogue, including acetic acid, lactic acid, citric acid, malic acid and formic acid, which are mixed in a ratio of 4:2:1:1:1, with a total concentration of 0.01 mol / L

[0026] Preferably, in step S4, the diffusion extraction process is carried out at room temperature, the temperature is maintained at 20-25° C., and the diffusion extraction time is 24-48 hours.

[0027] Beneficial effects of the present invention:

[0028] 1. The extraction device and determination method of the biologically effective state of trace metal elements in soil disclosed in the present invention not only do not require wind intervention treatment of the soil, but can also well simulate the diffusion and migration process of effective metal elements in the soil and the influence of root secretions on this process. It is more suitable for the extraction of the biologically effective state of trace heavy metals in soil, and is more conducive to the accurate measurement of the effective state content of trace heavy metal elements in soil and the accurate prediction of the absorption of trace heavy metal elements by plants.

[0029] 2. The device for extracting biologically effective trace metal elements in soil disclosed by the present invention has a simple structure, is easy to operate, and is highly practical. It does not require any supporting power equipment. For example, the horizontal movement of substances in a cylindrical diffusion pool is driven by concentration gradient, and the vertical movement of substances is driven by gravity, thereby greatly reducing labor and economic costs.

[0030] 3. The diffusion extraction of biologically effective components of trace metal elements in soil disclosed by the present invention fully simulates the process of plant nutrient absorption in principle, that is, the absorption of trace metal elements by plant roots leads to a decrease in their concentration in the rhizosphere, and the trace metals in the non-rhizosphere diffuse to the rhizosphere. At the same time, the small molecule chelating agents secreted by the roots in the process will also activate the trace metal elements in the non-rhizosphere. The cylindrical diffusion pool in the device represents the microsystem of the plant rhizosphere, the chelating agent supply bottle provides root secretions, and the trace metals in the receiving bottle represent the trace metals absorbed by the plant roots. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0033] Figure 2 The present invention Figure 1 Schematic diagram of the structure of the cylindrical diffusion cell;

[0034] Figure 3 It is a schematic diagram of the principle of diffusion extraction of trace metal elements in the prior art;

[0035] Figure 4 This is a schematic diagram of the principle of diffusion extraction of trace metal elements in the present invention;

[0036] Figure 5 It is a characteristic diagram of the diffusion extraction time kinetics of calcareous soil in the present invention;

[0037] Figure 6 It is a characteristic diagram of the diffusion extraction time kinetics of acidic soil in the present invention;

[0038] Figure 7 It is a graph showing the relationship between the content of soil trace elements and the content of crops measured using the root exudate supply solution;

[0039] Figure 8 It is a graph showing the relationship between the content of soil trace elements and the content of crops measured using DTPA supply solution;

[0040] Fig. 9 This is a comparison chart of the effective trace metal zinc content in soil measured by DGT technology;

[0041] Fig.10 This is a comparison chart of the effective trace metal zinc content in soil measured by DTPA technology;

[0042] Fig.11It is a comparison chart of the effective trace metal zinc content in the soil measured in the present invention;

[0043] Fig.12 This is the relationship between the content of trace elements in soil and the content of crops measured by DGT technology;

[0044] Fig.13 This is the relationship between the content of trace elements in soil and the content of crops measured by DTPA technology;

[0045] Fig.14 It is a relationship diagram between the content of trace elements in soil and the content of crops measured in the present invention.

[0046] The reference numerals in the figures are as follows:

[0047] 1. Bracket; 101. Loading plate; 2. Cylindrical diffusion tank; 201. Bottom joint; 3. Root simulation tube; 4. Chelating agent supply bottle; 5. First delivery hose; 501. First speed regulating valve; 6. Snap-on top cover; 601. Top cover connector; 7. Lifting bracket; 8. Receiver bottle; 9. Second delivery hose; 901. Second speed regulating valve. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] like Figure 1 and Figure 2 A biologically effective extraction device for trace metal elements in soil comprises a support 1, a horizontally arranged carrying plate 101 is fixedly connected to the center of the support 1, a cylindrical diffusion pool 2 in a linear array is arranged on the carrying plate 101, a root system simulation tube 3 is fixedly connected inside the cylindrical diffusion pool 2, and multiple root system simulation tubes 3 can be integrated on the same support 1, installed and used, which saves space and is convenient for operation;

[0050] Bioavailability refers to the ability of trace metal elements in the environment to migrate to the crop roots and be absorbed. In the soil system, when the crop roots absorb trace metal elements in the soil, the reduction of trace metal content in the rhizosphere not only provides the original driving force for the diffusion of trace metal elements in the soil to the root surface, but also promotes the transformation of soil zinc from an ineffective state to an effective state.

[0051] The root system simulation tube 3 is located in the center of the diffusion tank and is cylindrical. The tube wall of the root system simulation tube 3 has holes with a pore size of 0.5 mm. The tube wall of the root system simulation tube 3 is wrapped with a layer of 0.45 μm pore size filter membrane. The tube wall pore size and the outer filter membrane are used to ensure that soil particles will not pass through the root system simulation tube 3, while small molecules, ions, etc. can diffuse through and enter the root system simulation tube 3;

[0052] like Figure 1 and Figure 2 A chelating agent supply bottle 4 is arranged in the bracket 1 and above the cylindrical diffusion pool 2. The chelating agent supply bottle 4 contains root secretion analogs. A first delivery hose 5 is fixedly installed at the bottom of the chelating agent supply bottle 4. A snap-on top cover 6 is arranged on the top of the cylindrical diffusion pool 2. The snap-on top cover 6 is snapped on the top of the cylindrical diffusion pool 2. A top cover connector 601 is arranged on the top of the snap-on top cover 6. The bottom of the first delivery hose 5 and the top cover connector 601 are fixedly installed, and the first delivery hose 5 and the top cover connector 601 are connected.

[0053] like Figure 1 and Figure 2 The inner diameter of the root simulation tube 3 is 1 cm, the inner diameter of the cylindrical diffusion pool 2 is 2.5 cm, and the cavity between the inner surface of the cylindrical diffusion pool 2 and the outer surface of the root simulation tube 3 is used to load the soil to be tested.

[0054] like Figure 1 and Figure 2 The cylindrical diffusion pool 2 is made of transparent organic glass, and has a thickness of 3 mm and a height of 2.5 cm.

[0055] like Figure 1 and Figure 2 The top of the inner wall of the bracket 1 is fixedly connected with a hanging rack 7 in a linear array, and the top of the chelating agent supply bottle 4 is provided with a hanging rope, so that the chelating agent supply bottle 4 is hung on the hanging rack 7.

[0056] like Figure 1 and Figure 2 A receiving bottle 8 is provided at the bottom of the inner wall of the bracket 1, a bottom joint 201 is provided at the bottom of the cylindrical diffusion pool 2, a second delivery hose 9 is installed on the bottom joint 201, the first delivery pipe 5 and the second delivery pipe 9 are both connected to the root simulation tube 3 inside the cylindrical diffusion pool 2, and the bottom of the second delivery hose 9 extends to the inside of the receiving bottle 8, which is used to transport the solution passing through the root simulation tube 3 to the inside of the receiving bottle 8.

[0057] like Figure 1 and Figure 2The first delivery hose 5 is provided with a first speed regulating valve 501, and the second delivery hose 9 is provided with a second speed regulating valve 901, wherein the first delivery hose 5 and the first speed regulating valve 501, the second delivery hose 9 and the second speed regulating valve 901 are all the same as the infusion tube and the speed regulating valve on the infusion tube.

[0058] A method for determining the biologically effective state of trace metal elements in soil comprises the following steps:

[0059] S1. Collect the soil sample to be tested, add water to the sample that has passed the 1 mm sieve to the maximum field water holding capacity, soak it and set it aside;

[0060] S2, placing the wetted sample in step S1 into the cylindrical diffusion cell 2, ensuring that the soil is in full contact with the filter membrane of the outer layer of the root simulation tube 3, opening the first speed regulating valve 501 at the upper end of the cylindrical diffusion cell 2, allowing the chelating agent in the chelating agent supply bottle 4 to enter the root simulation tube 3 and be flush with the soil surface, and then closing the first speed regulating valve 501;

[0061] S3, open the first speed regulating valve 501 and the second speed regulating valve 901 again to ensure that the liquid level in the root system simulation tube 3 is always level with the soil surface, and the liquid flowing out of the root system simulation tube 3 can enter the receiving bottle 8;

[0062] S4, after diffusion extraction, close the first speed regulating valve 501 at the upper end of the cylindrical diffusion pool 2, and adjust the second speed regulating valve 901 at the lower end of the cylindrical diffusion pool 2 to allow all the solution in the root simulation tube 3 to quickly flow into the receiving bottle 8;

[0063] S5. Transfer the solution in the receiving bottle 8 directly or after concentration into a volumetric flask, make up the volume with a chelating agent or ultrapure water, and record the fixed volume; pass the solution in the volumetric flask through a 0.45 μm pore size filter membrane, and determine the trace metal content by graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry;

[0064] The trace metal element content is calculated using the following formula:

[0065]

[0066] Wherein, Y is the content of trace metal elements in the soil in an effective state, C is the content of trace metals, V is the volume of the volumetric flask, and m is the mass of the soil loaded (measured by oven-dried weight).

[0067] In the above method, adding water to the soil sample to be tested to the maximum field water holding capacity can make the soil reach a water pre-saturated state, providing the best water conditions for the diffusion and migration of trace metal elements in the soil to ensure the diffusion extraction efficiency. The immersion time is preferably 24 hours to ensure a uniform soil wetting state;

[0068] In the above method, the chelating agent is preferably an artificially prepared root exudate analog, including acetic acid, lactic acid, citric acid, malic acid and formic acid, which are mixed in a ratio of 4:2:1:1:1, with a total concentration of 0.01 mol / L; it can also be replaced by 0.01 mol / L DTPA, EDTA, HEDTA, CaCl2, NaNO3, HCl and other solutions respectively;

[0069] In the above method, the loaded soil should be in full contact with the outer filter membrane of the root system simulation tube 3 to minimize the spatial isolation of the water-soil interface and ensure that the molecules and ions in the soil and the root system simulation tube 3 can be effectively exchanged;

[0070] In the above method, the first speed regulating valve 501 and the second speed regulating valve 901 are opened at the same time to ensure that the liquid level in the root system simulation tube 3 is always level with the soil surface, and the flow rate is maintained at 50 to 100 mL per day. The flow rate can ensure that the chelating agent is fully retained in the cylindrical diffusion pool 2, and the chelating agent in the root system simulation tube 3 can diffuse into the soil to activate the metal elements. At the same time, the trace metal elements in the soil can migrate into the root system simulation tube 3 and flow into the receiving bottle;

[0071] In the above method, the diffusion extraction process is carried out at room temperature, the temperature is maintained at 20-25°C, and the diffusion extraction time is 24-48 hours, which can ensure that the diffusion process reaches equilibrium and improve the diffusion extraction efficiency;

[0072] In the above method, since trace metal elements diffuse very slowly in the soil, the concentration of trace metal elements in the receiving bottle 8 on non-contaminated soil may be lower than the detection limit of the equipment, so it needs to be concentrated, and the concentration multiple depends on the specific concentration;

[0073] In the above method, the solution or concentrate in the receiving bottle 8 must be transferred to the volumetric flask to avoid the loss of the extracted trace metal elements and cause the test data to be too small;

[0074] The steps and processes involved in the above method can also be used to determine the bioavailability or toxicity of heavy metals in contaminated soil, but the specific operating parameters need to be adjusted accordingly to ensure the diffusion extraction efficiency and the accuracy of the test results;

[0075] In the above method, all the important implementation parameters mentioned are strictly matched with the specification parameters of the invention device. If the size and model of the components of the device are adjusted, the operating parameters of the implementation process should also be adjusted accordingly to ensure the diffusion extraction efficiency and the accuracy of the detection;

[0076] Taking the greenhouse soil-cultured wheat seedlings test, the trace metal element zinc is used as an example:

[0077] Six levels of zinc application were set, namely 0, 4, 8, 16, 32 and 64 mg Zn kg -1Dry soil was used and repeated 3 times. ZnSO4·7H2O was selected as the Zn source. The test soil was zinc-deficient calcareous and acidic soil. The test period was 60 days. Wheat was cultured for about 50 days after emergence. The aboveground part and root system of wheat were collected to determine the zinc content. Soil samples were collected and the effective zinc content in the soil was determined by extraction DTPA method, DGT method and root simulation device.

[0078] The specific implementation methods for extraction and determination of biologically effective trace metal elements in soil are as follows:

[0079] Take a soil sample and pass it through a 1 mm sieve, add water to the maximum field water holding capacity, mix well with a glass rod, soak for 24 hours, and set aside;

[0080] Weigh 15 g of the above soil sample (by dry weight) and put it into the cylindrical diffusion cell 2, and compact it appropriately to ensure that the soil is in full contact with the filter screen of the root simulation tube 3;

[0081] The cylindrical diffusion cell 2 filled with soil samples, the chelating agent supply bottle 4 and the receiving bottle 8 are fixed on the bracket and connected by the first delivery hose 5. The first speed regulating valve 501 is opened, and the second speed regulating valve 901 is closed to allow the chelating agent to flow into the root system simulation tube 3. When the chelating agent liquid level in the root system simulation tube 3 is equal to the soil liquid level, the first speed regulating valve 501 is closed;

[0082] At the same time, the first speed regulating valve 501 and the second speed regulating valve 901 are opened to ensure that the liquid level in the root system simulation tube 3 is always level with the soil surface. The flow rate is 100 ml per day, which can ensure that the chelating agent is fully retained in the cylindrical diffusion tank 2. This process can diffuse the chelating agent in the root system simulation tube 3 into the soil to activate the metal elements. At the same time, the trace metal elements in the soil migrate into the root system simulation tube 3 and flow into the receiving bottle 8.

[0083] Under the above flow rate conditions, after diffusion extraction for several hours until the system is in equilibrium, the first speed regulating valve 501 is closed and the second speed regulating valve 901 is opened to allow all the chelating agents in the root simulation tube 3 to flow into the receiving bottle 8 .

[0084] The experimental samples were 0, 16 and 64 mg Zn kg -1 The time kinetics of the three soil samples treated with dry soil were studied. The results showed that the diffusion extraction could reach equilibrium within 48 hours regardless of the soil zinc application level (e.g. Figure 5 and Figure 6 );

[0085] During the diffusion extraction process, the temperature should be kept relatively constant at 20-25°C as much as possible, because temperature changes have a greater impact on the migration and extraction rate of substances in the soil;

[0086] The solution in the receiving bottle 8 (about 60 mL) was directly transferred to a volumetric flask, fixed to volume with a chelating agent, and the fixed volume V (100 mL) was recorded. Then, the solution in the volumetric flask was taken to measure the zinc content with an atomic absorption spectrometer to calculate the effective zinc content in the soil;

[0087] In the above operation, the chelating agent type was selected from artificially prepared root exudate analogs and DTPA solution for comparison. The results showed that the soil bioavailable zinc content measured by root exudate analogs had a higher fit with the zinc content in wheat roots and aboveground parts, so it was more accurate (Appendix Figure 7 and Figure 8 ).

[0088] like Figure 3 and Figure 4 In order to verify the superiority of this technology, the experiment compared it with traditional DTPA extraction and DGT determination. The strong adsorption and fixation effect of the soil made it difficult for trace metal elements to diffuse and migrate from the soil to the DGT adsorption layer, resulting in a large deviation between the predicted value and the measured value; the DGT technology ignored the role of root secretions and rhizosphere microbial metabolites such as amino acids and citric acid on the migration and transformation of soil zinc, resulting in a low predicted value. The root absorption simulation technology was used and it was found that the chelating agent simulated the root secretions very well, while the diffusion pool part simulated the element diffusion migration and root absorption process very well.

[0089] The results showed that the soil bioavailable zinc content measured by the root simulation device had the highest fit with the zinc content in plant roots and aboveground parts, followed by DGT-Zn and DTPA-Zn ( Figure 9-Figure 14 ).

[0090] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A biologically effective extraction device for trace metal elements in soil, comprising a support (1), characterized in that: A horizontally arranged carrying plate (101) is fixedly connected at the center of the support (1), a cylindrical diffusion pool (2) in a linear array is arranged on the carrying plate (101), a root system simulation tube (3) is fixedly connected inside the cylindrical diffusion pool (2), the root system simulation tube (3) is located in the center of the diffusion pool, is cylindrical, has a tube wall with holes, and the hole diameter is 0.5 mm, and a layer of 0.45 μm pore size filter membrane is wrapped outside the tube wall of the root system simulation tube (3), the tube wall hole diameter and the outer filter membrane are used to ensure that soil particles will not pass through the root system simulation tube (3), while small molecules, ions, etc. can diffuse through and enter the root system simulation tube (3); A chelating agent supply bottle (4) is arranged inside the support (1) and above the cylindrical diffusion pool (2); a first delivery hose (5) is fixedly installed at the bottom of the chelating agent supply bottle (4); a snap-on top cover (6) is arranged at the top of the cylindrical diffusion pool (2); a top cover connector (601) is arranged at the top of the snap-on top cover (6); and the bottom of the first delivery hose (5) and the top cover connector (601) are fixedly installed.

2. The device for extracting biologically effective trace metal elements from soil according to claim 1, characterized in that: The inner diameter of the root system simulation tube (3) is 1 cm, the inner diameter of the cylindrical diffusion pool (2) is 2.5 cm, and the cavity between the inner surface of the cylindrical diffusion pool (2) and the outer surface of the root system simulation tube (3) is used to load the soil to be tested.

3. A device for extracting biologically effective trace metal elements from soil according to claim 2, characterized in that: The cylindrical diffusion pool (2) is made of transparent organic glass, and has a thickness of 3 mm and a height of 2.5 cm.

4. The device for extracting biologically effective trace metal elements from soil according to claim 1, characterized in that: A hanging rack (7) in a linear array is fixedly connected to the top of the inner wall of the support (1), and the chelating agent supply bottle (4) is hung on the hanging rack (7).

5. The device for extracting biologically effective trace metal elements from soil according to claim 4, characterized in that: A receiving bottle (8) is arranged at the bottom of the inner wall of the support (1), a bottom joint (201) is arranged at the bottom of the cylindrical diffusion pool (2), a second delivery hose (9) is installed on the bottom joint (201), and the bottom of the second delivery hose (9) extends to the inside of the receiving bottle (8) and is used to deliver the solution passing through the root system simulation tube (3) to the inside of the receiving bottle (8).

6. The device for extracting biologically effective trace metal elements from soil according to claim 5, characterized in that: The first delivery hose (5) is provided with a first speed regulating valve (501), and the second delivery hose (9) is provided with a second speed regulating valve (901).

7. A method for determining the biologically effective state of trace metal elements in soil, using the biologically effective state extraction device for trace metal elements in soil as claimed in any one of claims 1 to 6, characterized in that: The determination method comprises the following steps: S1. Collect soil samples to be tested, add water to the samples that have passed the 1 mm sieve to the maximum field water holding capacity, soak them and set them aside; S2, placing the sample moistened in step S1 into the cylindrical diffusion cell (2), ensuring that the soil is in full contact with the filter membrane on the outer layer of the root system simulation tube (3), opening the first speed regulating valve (501) at the upper end of the cylindrical diffusion cell (2), allowing the chelating agent in the chelating agent supply bottle (4) to enter the root system simulation tube (3) and be flush with the soil surface, and then closing the first speed regulating valve (501); S3, opening the first speed regulating valve (501) and the second speed regulating valve (901) again, ensuring that the liquid level in the root system simulation tube (3) is always level with the soil surface, and that the liquid flowing out of the root system simulation tube (3) can enter the receiving bottle (8); S4. Under constant temperature conditions, after diffusion extraction, close the first speed regulating valve (501) at the upper end of the cylindrical diffusion pool (2), and adjust the second speed regulating valve (901) at the lower end of the cylindrical diffusion pool (2) to allow all the solution in the root simulation tube (3) to quickly flow into the receiving bottle (8); S5. Transfer the solution in the receiving bottle (8) directly or after concentration into a volumetric flask, make up the volume with a chelating agent or ultrapure water, and record the fixed volume; filter the solution in the volumetric flask through a 0.45 μm pore size filter membrane, and determine the trace metal content using graphite furnace atomic absorption spectrometry or inductively coupled plasma atomic emission spectrometry; The trace metal element content is calculated using the following formula: Among them, Y is the content of trace metal elements in the soil, C is the trace metal content, V is the volume of the volumetric flask, and m is the mass of the soil loaded.

8. The method for determining the biologically effective state of trace metal elements in soil according to claim 7, characterized in that: In the step S1, water is added to the soil sample to be tested to the maximum field water holding capacity so that the soil can reach a water pre-saturated state, which is used to provide the best moisture conditions for the diffusion and migration of trace metal elements in the soil to ensure the diffusion extraction efficiency. The immersion time is 24 hours.

9. The method for determining the biologically effective state of trace metal elements in soil according to claim 7, characterized in that: In step S2, the chelating agent is an artificially prepared root exudate analogue, including five components of acetic acid, lactic acid, citric acid, malic acid and formic acid, which are mixed in a ratio of 4:2:1:1:1, with a total concentration of 0.01 mol / L.

10. The method for determining the biologically effective state of trace metal elements in soil according to claim 7, characterized in that: In step S4, the diffusion extraction process is carried out at room temperature, the temperature is maintained at 20-25° C., and the diffusion extraction time is 24-48 hours.

Images