A method for detecting microplastics in soil

Abstract

This application relates to the field of environmental pollution detection, and specifically discloses a method for detecting microplastics in soil, which includes the following steps: (1) Take the soil sample to be tested, dry it, screen and remove large particles above 5 mm, then add hydrogen peroxide solution, stir and mix evenly, and then add an organic remover, and vortex and shake under sealing to obtain a mixed suspension; (2) Add pure water and saturated salt solution to the mixed suspension, mix evenly, let it stand and layer, and remove the lower layer of sediment to obtain a preliminary extraction suspension; (3) Filter the preliminary extraction suspension to obtain a filter residue, dry it, and perform qualitative analysis using a microscopic Raman spectrometer; the organic remover in the above step (1) is composed of components including polyquaternary ammonium salt and chitosan-loaded mesoporous silica, and the weight ratio of polyquaternary ammonium salt to chitosan-loaded mesoporous silica is (2-5):1. The method for detecting microplastics in soil of this application is more efficient and accurate during application.

Description

Technical Field

[0001] This application relates to the field of environmental pollution detection, and more specifically, to a method for detecting microplastics in soil. Background Art

[0002] Microplastics generally refer to polymer particles with a size less than 5 mm, and their morphologies can be divided into spherical, film, fiber and fragment. Their chemical properties are relatively stable and can exist in the environment for a long time. Microplastics enter the soil environment through long-term residual agricultural films, application of sludge and organic fertilizers, surface water irrigation and atmospheric deposition, etc. It will change the physical and chemical properties of the soil and bring great adverse effects to the stability of the soil environment. Therefore, the detection method of microplastics in soil has also become a hot topic in the current environmental protection field.

[0003] In the application process of the detection method, the application of microscopic Raman spectroscopy is based on the fact that different sample molecular structures and atoms will cause the laser beam falling on the object to produce backscattered light with different frequencies, so as to obtain the unique spectral images of different polymers. However, microplastics have a relatively large specific surface area and good hydrophobic properties, so they have a relatively good adsorption effect on organic matter. During the microscopic Raman spectroscopy detection of organic matter, relatively strong fluorescence interference will be generated, resulting in a significant reduction in the recognition accuracy. To address the interference caused by organic matter in the above detection process, digestion treatment is usually carried out before detection. Currently, common digestions include strong acid digestion, strong base digestion, oxidation digestion, and enzyme digestion. The application of strong base digestion is not very extensive yet.

[0004] Regarding the above related technologies, the inventor believes that the organic matter in the soil is relatively complex. To ensure that the organic matter can be removed more completely, it is often necessary to carry out 3 - 6 times of digestion to effectively remove the interference of organic matter. This process will result in a longer processing time, and to ensure the digestion effect, the sampling is restricted, and it is difficult to analyze a large number of samples during the application process. Therefore, there is an urgent need to propose a solution to solve the above technical problems. Summary of the Invention

[0005] In order to improve the digestion effect of soil samples and make the detection of microplastics more efficient and accurate, this application provides a method for detecting microplastics in soil.

[0006] A method for detecting microplastics in soil provided by this application adopts the following technical solution:

[0007] A method for detecting microplastics in soil includes the following steps:

[0008] (1) Take the soil sample to be tested, dry it, screen out and remove large particulate matter above 5 mm, then add hydrogen peroxide solution, stir and mix evenly, and then add an organic removing agent. Vortex and shake under sealing to obtain a mixed suspension;

[0009] (2) Add pure water and saturated salt solution to the mixed suspension, mix evenly, let it stand and layer, and remove the lower-layer precipitate to obtain a preliminarily extracted suspension;

[0010] (3) Filter the preliminarily extracted suspension to obtain a filter residue, dry it, perform Raman characterization on the filter residue using a microscopic Raman spectrometer to obtain a sample Raman spectrum, and then perform online retrieval and comparison with the standard spectrum for qualitative analysis;

[0011] The organic removing agent in the above step (1) is composed of components including polyquaternary ammonium salt and chitosan-loaded mesoporous silica, and the weight ratio of polyquaternary ammonium salt to chitosan-loaded mesoporous silica is (2 - 5):1.

[0012] By adopting the above technical solution, first screening out and removing large particulate matter above 5 mm can accelerate the processing efficiency in the subsequent operation process, and enable the organic matter on the surface of microplastics below 5 mm to be fully affected. Then add hydrogen peroxide solution, which mainly acts on the organic matter in the soil. During the re-digestion process, add an organic removing agent composed of polyquaternary ammonium salt and chitosan-loaded mesoporous silica. Its high dispersibility and permeability can effectively strip the organic matter attached to the surface of microplastics during the vortex shaking process; at the same time, the stripped organic matter and the free organic matter coagulate together under the action of the organic removing agent to form an organic matter mixed flocculent body. Then, add pure water and saturated salt solution to the mixed suspension, let it stand and layer, so that the inorganic clay minerals and the organic matter mixed flocculent body in the water sample precipitate to the lower layer. Furthermore, after filtration and drying, a microplastic filter residue with a relatively clean surface can be obtained, and using a microscopic Raman spectrometer to perform Raman characterization on the filter residue can also obtain a relatively accurate sample Raman spectrum. In summary, in the application of the detection method of this application, due to the use of an organic removing agent composed of polyquaternary ammonium salt and chitosan-loaded mesoporous silica with a specific mass ratio, in the operation of digestion using hydrogen peroxide solution, only one digestion is required to effectively remove the organic matter adsorbed on the surface of microplastics, and it can accurately perform qualitative analysis on microplastics in soil using a microscopic Raman spectrometer.

[0013] Preferably, the weight ratio of the polyquaternary ammonium salt to the chitosan-loaded mesoporous silica is 3:1.

[0014] By adopting the above technical solution, the proportionally mixed polyquaternium and chitosan-loaded mesoporous silica can achieve excellent cooperative effects during application. It can not only completely strip the organic matter on the surface of microplastics, but also form a relatively stable organic matter mixed floc with the stripped and free organic matter, which is not easy to break. Therefore, it can ensure the effective removal of organic matter, which is beneficial to improving the accuracy of Raman characterization during detection.

[0015] Preferably, step (1) is specifically set as follows: Take the soil sample to be tested, dry it, screen and remove large particles above 5 mm, then add hydrogen peroxide solution, stir and mix evenly, then add the organic matter remover, and perform vortex oscillation under sealing. During the process, microwave irradiation treatment is carried out to obtain a mixed suspension.

[0016] By adopting the above technical solution, during the vortex oscillation process, microwave irradiation treatment is carried out. On the one hand, it can make the organic matter on the surface of microplastics be stripped more quickly and completely. On the other hand, due to the strong absorption of microwave energy by chitosan-loaded mesoporous silica, its own adsorption performance is greatly improved. As a result, the organic matter mixed floc is more compact, and the flocculated organic matter is not easy to disperse and separate. And during the subsequent process of adding pure water and saturated salt solution for flotation, the organic matter can be removed more fully and completely, making the detection of microplastics more efficient and accurate.

[0017] Preferably, in step (1), the microwave irradiation power is 400 - 600 W, and the irradiation time is 10 - 15 min.

[0018] By adopting the above technical solution, the selection of the above irradiation power and irradiation time can make the organic matter remover play a more efficient and excellent role, and the effect on the organic matter on the surface of microplastics is relatively excellent.

[0019] Preferably, step (1) is specifically set as follows: Take the soil sample to be tested, dry it, screen and remove large particles above 5 mm, then add hydrogen peroxide solution and adjust the pH to 7 - 8, stir and mix evenly, then add the organic matter remover, and perform vortex oscillation under sealing to obtain a mixed suspension.

[0020] By adopting the above technical solution, during the operation process of step (1), adjusting the pH to 7 - 8 helps the hydrogen peroxide solution to play a stable role, and the digestion effect is relatively excellent. Moreover, it can make the formation of the organic matter mixed floc more stable, making the role of each reagent and raw material in the whole treatment process more comprehensive and stable, and thus can achieve an excellent organic matter removal effect.

[0021] Preferably, step (1) is specifically set as follows: take the soil sample to be tested, dry it, screen and remove large particulate matter above 5 mm, then add hydrogen peroxide solution, stir and mix evenly, then add an organic removing agent and a synergistic auxiliary agent, and perform vortex oscillation under sealing to obtain a mixed suspension; the synergistic auxiliary agent is composed of polyacrylamide and poly(dimethyldiallylammonium chloride), and the weight ratio of polyacrylamide to poly(dimethyldiallylammonium chloride) is (3-5):1.

[0022] By adopting the above technical solution, polyacrylamide has good flocculability, and poly(dimethyldiallylammonium chloride) has strong cohesion. When the two are mixed in a specific mass ratio to form a synergistic auxiliary agent, they are compounded and synergized with each other. With the assistance of the organic removing agent, the organic matter adsorbed on the surface of the microplastics is stripped, and the forming rate and stability of the organic matter mixed floccules are greatly improved, so that it can be fully removed in the subsequent treatment process, greatly improving the removal effect of the organic matter, and being beneficial to making the Raman spectrum detected by the micro-Raman spectrometer more accurate.

[0023] Preferably, the weight ratio of the polyacrylamide to the poly(dimethyldiallylammonium chloride) is 4:1.

[0024] By adopting the above technical solution, the synergistic auxiliary agent composed of polyacrylamide and poly(dimethyldiallylammonium chloride) in the above mass ratio has an excellent cooperation effect between the two component raw materials during the application process, and has a significant synergistic effect on the organic removing agent, thereby being able to further ensure the accuracy during the detection process.

[0025] Preferably, in step (1), the concentration of the hydrogen peroxide solution is 30%-40%.

[0026] By adopting the above technical solution, the hydrogen peroxide solution with the above concentration is not likely to affect or even damage the microplastic structure, and can effectively cooperate with the organic removing agent to strip the organic matter on the surface of the microplastics relatively completely, and create a relatively stable environment for the formation of the organic matter mixed floccules to ensure that the organic matter is fully removed in the subsequent treatment process.

[0027] Preferably, in step (1), during the vortex oscillation process, the temperature is 40-60 °C and the time is 20-30 min.

[0028] By adopting the above technical solution, during the vortex oscillation process, the control of the above temperature and time not only fully acts on the organic matter adsorbed on the surface of the microplastics, but also makes the formed organic matter mixed floccules not easily break, achieving an efficient and stable effect, so that in the subsequent operation process, the organic matter is removed relatively completely and the detection is more accurate.

[0029] Preferably, in step (2), the saturated salt solution is one or a combination of saturated sodium chloride solution, saturated calcium chloride solution, saturated sodium iodide solution and saturated zinc chloride solution.

[0030] By adopting the above technical scheme, the above types of saturated salt solutions can exert a stable effect during the application process, and the mixed floccules of inorganic clay minerals and organic matter in the water sample are precipitated to the lower layer, and the separation effect is stable and excellent.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. Since the present application adds an organic remover composed of polyquaternary ammonium salt and chitosan-loaded mesoporous silica in a specific mass ratio, and cooperates with the digestion of hydrogen peroxide solution, the organic matter attached to the surface of microplastics can be effectively stripped off, and mixed organic floccules can be formed. When pure water and saturated salt solution are subsequently added for flotation, it is beneficial to fully remove the organic matter, and only one digestion is required during the process. A large number of samples can be analyzed, and a micro-Raman spectrometer can be used to accurately perform qualitative analysis of microplastics in the soil. The overall application is efficient and stable;

[0033] 2. During the action of the organic remover, microwave irradiation treatment can not only make the organic matter on the surface of microplastics more quickly and completely peeled off, but also improve the compactness and firmness of the organic mixed floccules, further ensuring that the formed organic mixed floccules are not easy to break, which is conducive to more complete removal of organic matter, thereby making the detection of microplastics in soil more efficient and accurate;

[0034] 3. During the action of the organic remover, the addition of a synergistic additive composed of polyacrylamide and polydimethyldiallyl ammonium chloride in a specific weight ratio can further improve the stripping efficiency and rate of organic matter on the surface of microplastics, and greatly improve the formation rate and stability of organic mixed flocs, thereby greatly improving the removal effect of organic matter, which is conducive to making the Raman spectrum produced by the micro-Raman spectrometer more accurate. DETAILED DESCRIPTION

[0035] The present application is further described in detail below with reference to the embodiments.

[0036] Unless otherwise specified, the raw materials used in the examples of this application are commercially available:

[0037] The polyquaternium salt was purchased from BLUWAT / Blue Wave PAC-SJ type;

[0038] Chitosan-loaded mesoporous silica was purchased from Xi’an Qiyue Biotechnology Co., Ltd., catalog number 0505;

[0039] The micro-Raman spectrometer is the Pushi Nano SR532 model.

[0040] Example

[0041] Example 1

[0042] A method for detecting microplastics in soil, including the following steps:

[0043] (1) Take the soil sample to be tested, dry it, screen and remove large particles above 5 mm, then add hydrogen peroxide solution. The volume ratio of the hydrogen peroxide solution to the weight of the screened soil sample is 30 mL / 1 g, and adjust the pH to 7.5. Stir and mix evenly, then add an organic remover accounting for 10% of the weight of the screened soil sample, and vortex shake under sealing to obtain a mixed suspension;

[0044] (2) Add 5 times the weight of pure water and 10 times the weight of saturated salt solution to the mixed suspension, mix evenly, let it stand and layer, and remove the lower-layer precipitate to obtain a preliminary extraction suspension;

[0045] (3) Filter the preliminary extraction suspension to obtain a filter residue, dry it, and use a micro-Raman spectrometer to perform Raman characterization on the filter residue. The spectral range is 600 - 4000 cm- 1 , obtain the Raman spectrum of the sample, and then perform online retrieval and comparison with the standard spectrum for qualitative analysis;

[0046] The organic remover in the above step (1) is composed of polyquaternary ammonium salt and chitosan-loaded mesoporous silica, and the weight ratio of polyquaternary ammonium salt to chitosan-loaded mesoporous silica is 3:1; the concentration of the hydrogen peroxide solution is 35%; during the vortex shaking process, the temperature is 50 °C and the time is 25 min. In step (2), the saturated salt solution is saturated sodium chloride solution.

[0047] Example 2

[0048] A method for detecting microplastics in soil, which is different from Example 1 in that the weight ratio of polyquaternary ammonium salt to chitosan-loaded mesoporous silica is 2:1.

[0049] Example 3

[0050] A method for detecting microplastics in soil, which is different from Example 1 in that the weight ratio of polyquaternary ammonium salt to chitosan-loaded mesoporous silica is 5:1.

[0051] Example 4

[0052] A method for detecting microplastics in soil, which is different from Example 1 in that the weight ratio of polyquaternary ammonium salt to chitosan-loaded mesoporous silica is 3.5:1.

[0053] Example 5

[0054] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), after adding hydrogen peroxide solution, the pH is adjusted to 7.

[0055] Example 6

[0056] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), after adding hydrogen peroxide solution, the pH is adjusted to 8.

[0057] Example 7

[0058] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), the concentration of the hydrogen peroxide solution is 30%.

[0059] Example 8

[0060] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), the concentration of the hydrogen peroxide solution is 40%.

[0061] Example 9

[0062] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), during the vortex oscillation process, the temperature is 40 °C and the time is 30 min.

[0063] Example 10

[0064] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), during the vortex oscillation process, the temperature is 60 °C and the time is 20 min.

[0065] Example 11

[0066] A method for detecting microplastics in soil, which is different from Example 1 in that in step (2), the saturated salt solution is a composition of saturated calcium chloride solution and saturated sodium iodide solution in a weight ratio of 1:1.

[0067] Example 12

[0068] A method for detecting microplastics in soil, which is different from Example 1 in that in step (2), the saturated salt solution is a composition of saturated sodium chloride solution, saturated calcium chloride solution, and saturated sodium iodide solution in a weight ratio of 1:1:1.

[0069] Example 13

[0070] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), during the vortex oscillation process, microwave irradiation treatment is carried out, the microwave irradiation power is 500 W, and the irradiation time is 12.5 min.

[0071] Example 14

[0072] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), microwave irradiation treatment is carried out during the vortex oscillation process, the microwave irradiation power is 400 W, and the irradiation time is 15 min.

[0073] Example 15

[0074] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), microwave irradiation treatment is carried out during the vortex oscillation process, the microwave irradiation power is 600 W, and the irradiation time is 10 min.

[0075] Example 16

[0076] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), while adding an organic remover, a synergistic auxiliary agent composed of polyacrylamide and polydimethyldiallylammonium chloride is added, the weight ratio of the synergistic auxiliary agent to the organic remover is 1:1, and the weight ratio of polyacrylamide to polydimethyldiallylammonium chloride is 4:1.

[0077] Example 17

[0078] A method for detecting microplastics in soil, which is different from Example 16 in that the weight ratio of polyacrylamide to polydimethyldiallylammonium chloride is 3:1.

[0079] Example 18

[0080] A method for detecting microplastics in soil, which is different from Example 16 in that the weight ratio of polyacrylamide to polydimethyldiallylammonium chloride is 5:1.

[0081] Example 19

[0082] A method for detecting microplastics in soil, which is different from Example 16 in that the synergistic auxiliary agent is polyacrylamide.

[0083] Example 20

[0084] A method for detecting microplastics in soil, which is different from Example 16 in that the synergistic auxiliary agent is polydimethyldiallylammonium chloride.

[0085] Example 21

[0086] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), after adding hydrogen peroxide solution, the pH is adjusted to 6.5.

[0087] Example 22

[0088] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), after adding the hydrogen peroxide solution, the pH is adjusted to 8.5.

[0089] Example 23

[0090] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), during the vortex oscillation process, the temperature is 35 °C and the time is 35 min.

[0091] Example 24

[0092] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), during the vortex oscillation process, the temperature is 65 °C and the time is 15 min.

[0093] Example 25

[0094] A method for detecting microplastics in soil, which is different from Example 16 in that the weight ratio of polyacrylamide to polydimethyldiallylammonium chloride is 2.5:1.

[0095] Example 26

[0096] A method for detecting microplastics in soil, which is different from Example 16 in that the weight ratio of polyacrylamide to polydimethyldiallylammonium chloride is 5.5:1.

[0097] Comparative example

[0098] Comparative example 1

[0099] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), the organic remover is polyquaternium.

[0100] Comparative example 2

[0101] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), the organic remover is chitosan-loaded mesoporous silica.

[0102] Comparative example 3

[0103] A method for detecting microplastics in soil, which is different from Example 1 in that in step (1), no organic remover is used.

[0104] Comparative example 4

[0105] A method for detecting microplastics in soil, which is different from Example 1 in that the weight ratio of polyquaternium to chitosan-loaded mesoporous silica is 1.5:1.

[0106] Comparative Example 5

[0107] A method for detecting microplastics in soil, which is different from Example 1 in that the weight ratio of polyquaternium salt to chitosan-loaded mesoporous silica is 5.5:1.

[0108] Performance detection test Test sample: Soil samples were collected at the estuary of the Huangpu River in October 2022. The sampling point was within the area about 5 kilometers from the estuary. 5 kg of soil samples were collected, dried and crushed, and used as the final soil samples to be tested.

[0109] Test method:

[0110] (1) Take 100 g of the test soil sample and detect it by the method for detecting microplastics in soil in Example 1 to finally obtain the types of microplastics in the soil sample; take another 100 g of the test soil sample and conduct conventional multiple digestion detections, that is, repeat the relevant operations in Example 1, with the difference that in step (1), no organic remover is used, and hydrogen peroxide solution is used to repeat digestion five times, and finally obtain the types of microplastics in the soil sample; record them in Table 1 below.

[0111] Table 1 Test results of Example 1 and conventional multiple digestion detections

[0112] Method Microplastic types Example 1 153 Conventional multi - digestion detection 153

[0113] It can be seen that compared with the detection scheme of conventional multiple digestion, the detection results of Example 1 of this application are basically the same. It shows that when using the organic remover composed of polyquaternium salt and chitosan-loaded mesoporous silica in the detection process, only one digestion is required to fully remove organic matter, the detection is more efficient, and excellent detection accuracy can be maintained.

[0114] (2) Use the methods for detecting microplastics in soil in Examples 1-26 and Comparative Examples 1-5 to detect the soil samples to be tested respectively. Each time, 100 g of soil samples are taken, and then the detection spectra of polystyrene, polyvinyl chloride, phenolic resin, polyvinyl alcohol and polyoxymethylene are compared with the standard spectral library, and the average value of the spectral matching degrees of the three microplastics is taken to evaluate the accuracy of the corresponding detection method.

[0115] Table 2 Test results of Examples 1-26 and Comparative Examples 1-5

[0116]

[0117]

[0118] Combined with Examples 1-4 and Comparative Examples 1-3 and in conjunction with Table 2, it can be seen that by adding an organic remover composed of polyquaternium salt and chitosan-loaded mesoporous silica in a specific mass ratio in this application, during the actual application process of the detection method for microplastics in soil, the matching degree between the obtained Raman spectra of the samples and the standard spectra can reach over 90%, all with high precision. It is speculated that the organic remover has an excellent stripping effect on the organic matter adsorbed on the surface of microplastics, so that the organic matter on the surface of microplastics can be fully digested by hydrogen peroxide solution, and the excess organic matter can also form an organic matter mixed floc under the action of the organic remover, which is convenient for removal during the subsequent flotation process, further improving the removal effect of organic matter. At the same time, when either polyquaternium salt or chitosan-loaded mesoporous silica is used alone as the organic remover, the improvement of the matching degree is limited, and the improvement effect is far less excellent than that brought by the compounding of the two, indicating that the cooperation between the two has brought outstanding and significant progress. Combined with Comparative Examples 4-5 and in conjunction with Table 2, it can be seen that polyquaternium salt and chitosan-loaded mesoporous silica can only achieve excellent cooperation effects within a specific proportion range, and being lower or higher than the cooperation range required by this application will have an adverse impact on the accuracy of detection.

[0119] Combined with Example 1 and Examples 13-15 and in conjunction with Table 2, it can be seen that by performing microwave irradiation treatment, the matching degree of the experimental detection results can be further improved. It may be that the microwave irradiation further enhances the effect of the organic remover.

[0120] Combined with Example 1 and Examples 16-18 and in conjunction with Table 2, it can be seen that during the action of the organic remover, by adding a synergistic aid composed of polyacrylamide and poly(dimethyldiallylammonium chloride) in a specific weight ratio, the removal effect of organic matter can be further improved, and then, in terms of experimental results, a higher improvement in the matching degree is shown. Combined with Examples 19-20 and in conjunction with Table 2, it can be seen that when either polyacrylamide or poly(dimethyldiallylammonium chloride) is used alone as the synergistic aid, the improvement effect is limited, far less excellent than that brought by the compounding of the two, indicating that the cooperation between the two has brought outstanding and significant progress. Combined with Examples 25-26 and in conjunction with Table 2, it can be seen that being lower or higher than the proportion range defined in this application will greatly reduce the improvement effect brought by the synergistic aid.

[0121] Combined with Example 1, Examples 5-6 and Examples 21-22 and in conjunction with Table 2, it can be seen that during the operation of step (1), adjusting the pH to 7-8 helps the hydrogen peroxide solution to play a stable role, and being lower or higher than the above range will lead to a decrease in the matching degree, indicating that it is due to the reduction of the removal effect of organic matter.

[0122] Combined with Example 1, Examples 9-10 and Examples 23-24 and combined with Table 2, it can be seen that in step (1), during the vortex oscillation process, when the temperature is 40-60 °C and the time is 20-30 min, it is more conducive to the action of the hydrogen peroxide solution and the organic remover. If it is lower or higher than the above range, it will lead to a decrease in the removal effect of organic matter, and the experimental results show a decrease in the matching degree.

[0123] This specific embodiment is only an interpretation of the present application, and it is not a limitation of the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A detection method for microplastics in soil, characterized in that, It includes the following steps: (1) Take the soil sample to be tested, dry it, screen and remove the large particulate matter over 5 mm, then add hydrogen peroxide solution, stir and mix evenly, then add the organic removing agent and the synergistic auxiliary agent, and perform vortex oscillation under sealing to obtain a mixed suspension; the synergistic auxiliary agent is composed of polyacrylamide and poly(dimethyldiallylammonium chloride), and the weight ratio of polyacrylamide to poly(dimethyldiallylammonium chloride) is (3-5):1; (2) Add pure water and saturated salt solution to the mixed suspension, mix evenly, let it stand and layer, and remove the lower-layer precipitate to obtain a primary extraction suspension; (3) Filter the primary extraction suspension to obtain a filter residue, dry it, perform Raman characterization on the filter residue using a microscopic Raman spectrometer to obtain a sample Raman spectrum, and then perform online retrieval and comparison with the standard spectrum for qualitative analysis; The organic removing agent in the above step (1) is composed of components including polyquaternary ammonium salt and chitosan-loaded mesoporous silica, and the weight ratio of polyquaternary ammonium salt to chitosan-loaded mesoporous silica is (2-5):

1.

2. The detection method of microplastics in soil according to claim 1, wherein: The weight ratio of the polyquaternary ammonium salt to the chitosan-loaded mesoporous silica is 3:

1.

3. The detection method of microplastics in soil according to claim 1, characterized in that: Step (1) is specifically set as follows: take the soil sample to be tested, dry it, screen and remove the large particulate matter over 5 mm, then add hydrogen peroxide solution, stir and mix evenly, then add the organic removing agent, and perform vortex oscillation under sealing, and perform microwave irradiation treatment during the process to obtain a mixed suspension.

4. The detection method of microplastics in soil according to claim 3, characterized in that: In step (1), the microwave irradiation power is 400-600 W, and the irradiation time is 10-15 min.

5. The detection method of microplastics in soil according to claim 1, characterized in that: Step (1) is specifically set as follows: take the soil sample to be tested, dry it, screen and remove the large particulate matter over 5 mm, then add hydrogen peroxide solution and adjust the pH to 7-8, stir and mix evenly, then add the organic removing agent, and perform vortex oscillation under sealing to obtain a mixed suspension.

6. The detection method of microplastics in soil according to claim 1, wherein: The weight ratio of the polyacrylamide to the poly(dimethyldiallylammonium chloride) is 4:

1.

7. The detection method of microplastics in soil according to claim 1, wherein: In step (1), the concentration of the hydrogen peroxide solution is 30%-40%.

8. The detection method of microplastics in soil according to claim 1, characterized in that: In step (1), during the vortex oscillation process, the temperature is 40-60 °C, and the time is 20-30 min.

9. The detection method of microplastics in soil according to claim 1, characterized in that: In step (2), the saturated salt solution is a composition of one or more of saturated sodium chloride solution, saturated calcium chloride solution, saturated sodium iodide solution and saturated zinc chloride solution.

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