Method for detecting micron and nano plastics in soil or sediment and related application

Abstract

The invention provides a method for detecting micron and nano plastics in soil or sediments and related application. The detection method comprises the following steps: providing a soil or sediment sample to be detected; the method comprises the following steps: pretreating a to-be-detected soil or sediment sample to obtain a to-be-detected solution; performing multi-stage filtration treatment on the solution to be detected to obtain micro-plastic particles in a plurality of particle size intervals; wherein the plurality of particle size intervals comprise a first particle size interval, a second particle size interval and a third particle size interval; the particle size of the first particle size interval is 1-5000 [mu] m; the particle size of the second particle size interval is 220-1000 nm; the particle size of the third particle size interval is 10-220nm; and performing quantitative analysis on the micro-plastic particles in the plurality of particle size intervals through pyrolysis-gas chromatography / mass spectrometry to obtain the mass concentration of the micro-plastic particles in the plurality of particle size intervals. The problem that the risk assessment of micron and nano plastics is not accurate enough at present can be solved to a certain extent.

Description

Technical Field

[0001] This application relates to the field of microplastic remediation technology, and in particular to a method for detecting micron and nanoplastics in soil or sediments and related applications. Background Technology

[0002] The large-scale production and consumption of plastics has generated a massive amount of plastic waste. It is projected that global plastic waste emissions will reach 44 million tons annually by 2060. Due to the lack of effective recycling methods, approximately 90% of plastic waste will be released into or accumulate in soil or sediment. This plastic waste, undergoing long-term weathering (such as photoaging, physical abrasion, and biodegradation), can lead to the formation of microplastics (5 mm–1 μm) and even nanoplastics (<1000 nm). Microplastics and nanoplastics affect ecosystems and biological health through their own physicochemical properties and interactions with surrounding materials. Therefore, assessing the ecological risks of microplastics is of great significance.

[0003] Currently, the risk assessment of micron and nanoplastics is not accurate enough. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a method for detecting micron and nanoplastics in soil or sediments and related applications.

[0005] To achieve the above objectives, this application provides a method for detecting micron and nanoplastics in soil or sediments, comprising:

[0006] Provide soil or sediment samples to be tested;

[0007] The soil or sediment sample to be tested is pretreated to obtain the test solution;

[0008] The solution to be tested is subjected to multi-stage filtration to obtain microplastic particles in multiple particle size ranges; wherein, the multiple particle size ranges include a first particle size range, a second particle size range, and a third particle size range; the particle size of the first particle size range is 1-5000 μm; the particle size of the second particle size range is 220-1000 nm; and the particle size of the third particle size range is 10-220 nm.

[0009] The microplastic particles in the multiple particle size ranges were quantitatively analyzed by pyrolysis-gas chromatography / mass spectrometry to obtain the mass concentration of microplastic particles in the multiple particle size ranges.

[0010] In some embodiments, the types of microplastic particles in the plurality of particle size ranges include at least one of PMMA, PP, PS, PET, PE, and PA.

[0011] In some embodiments, the multi-stage filtering of the solution to be detected comprises:

[0012] The solution to be detected is subjected to a first filtering process to obtain microplastic particles having the first particle size range; the filter membrane of the first filtering process has a pore size of 1 μm;

[0013] The filtrate obtained by the first filtering process is subjected to a second filtering process to obtain microplastic particles having the second particle size range; the filter membrane of the second filtering process has a pore size of 0.22 μm;

[0014] The filtrate obtained by the second filtering process is subjected to a third filtering process to obtain microplastic particles having the third particle size range; the filter membrane of the third filtering process has a molecular weight cut-off of 100 KDa.

[0015] In some embodiments, the filter membrane material of the first filtering process is stainless steel or alumina; the filter membrane material of the second filtering process is polytetrafluoroethylene or alumina; and the filter membrane material of the third filtering process is regenerated cellulose.

[0016] In some embodiments, the detection method further comprises, after at least one of the first filtering process, the second filtering process, and the third filtering process, performing multiple alcohol washes to obtain microplastic particles of the corresponding particle size range.

[0017] In some embodiments, the pretreatment of the soil or sediment sample to be detected to obtain a solution to be detected comprises:

[0018] A sodium bromide solution is added to the soil or sediment sample to be detected, ultrasonic dispersion and centrifugation are performed to obtain a supernatant; the mass concentration of sodium bromide in the sodium bromide solution is 39-41%;

[0019] A hydrogen peroxide solution is added to the supernatant, and the reaction is carried out for 23.5-24.5 h; the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 29-31%.

[0020] In some embodiments, the volume-to-mass ratio of the sodium bromide solution to the soil or sediment sample is (9.5-10.5) ml: 1 g; and the volume ratio of the hydrogen peroxide to the supernatant is (0.9-1.1): 1.

[0021] In some embodiments, the microplastic particles of the plurality of particle size ranges are microplastic particles loaded on a plurality of filter membranes; wherein the particle sizes of the plurality of filter membranes correspond one-to-one to the plurality of particle size ranges; and the quantitative analysis of the microplastic particles of the plurality of particle size ranges by pyrolysis-gas chromatography / mass spectrometry comprises:

[0022] Microplastic particles in the multiple particle size ranges were transferred to a pyrolysis cup for quantitative analysis.

[0023] This application also provides a method for assessing the risk of micron and nanoplastics in soil or sediments, the assessment method being based on the mass concentration of microplastic particles in multiple particle size ranges obtained by the detection method for micron and nanoplastics in soil or sediments as described in any of the preceding embodiments.

[0024] This application also provides a method for remediating micron and nanoplastics in soil or sediment, the method being based on the mass concentration of microplastic particles in multiple particle size ranges obtained by the detection method for micron and nanoplastics in soil or sediment as described in any of the preceding embodiments.

[0025] As can be seen from the above, the method for detecting micron and nanoplastics in soil or sediment provided in this application involves providing a soil or sediment sample to be tested; pretreating the soil or sediment sample to obtain a test solution; subjecting the test solution to multi-stage filtration to obtain microplastic particles in multiple particle size ranges; wherein the multiple particle size ranges include a first particle size range, a second particle size range, and a third particle size range; the particle size of the first particle size range is 1-5000 μm; the particle size of the second particle size range is 220-1000 nm; and the particle size of the third particle size range is 10-220 nm; and the microplastic particles in the multiple particle size ranges are quantitatively analyzed by pyrolysis-gas chromatography / mass spectrometry to obtain the mass concentration of microplastic particles in multiple particle size ranges, which can overcome the bottleneck of traditional methods that cannot obtain the mass concentration corresponding to each particle size in particle size classification. It can also improve the accuracy of risk assessment methods and remediation methods for micron and nanoplastics in soil or sediment to a certain extent. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic flowchart of a method for detecting micron and nanoplastics in soil or sediment according to an embodiment of this application.

[0028] Figure 2a The total ion chromatograms of different series of PE microplastics according to embodiments of this application are shown.

[0029] Figure 2b forFigure 2a The corresponding standard curve;

[0030] Figure 3 This is a schematic diagram of the total ion chromatograms of microplastics in three particle size ranges according to embodiments of this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0032] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by those skilled in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0033] Microplastics are plastic particles with a diameter of less than 5 millimeters, requiring a microscope for optimal observation. They are typically formed from the decomposition of larger plastic waste through physical, chemical, and biological processes, and can also originate from microplastics released during cosmetics, detergents, and industrial production. Microplastics are primarily found in soil and sediment environments and can enter organisms through the food chain, posing a potential threat to the ecological environment and human health. Microplastics can include micron-sized plastics (5 mm–1 μm) and nanoplastics (<1000 nm). Therefore, assessing the ecological risks of microplastics is of great significance.

[0034] While both microplastics and nanoplastics can influence ecosystems and biological health through their physicochemical properties and interactions with surrounding matter, nanoplastics, with their smaller particle size and larger specific surface area, can be absorbed by cellular tissues (such as plant leaves and earthworm intestines) and more readily adsorb toxic substances (such as heavy metals and antibiotics), thus posing a greater environmental threat. Furthermore, nanoplastics smaller than 220 nm are more easily transported between cells via vesicles, thereby disrupting the microenvironment. Therefore, conducting ecological risk assessments of microplastics based on accurate mass concentrations across different particle size ranges is of great significance.

[0035] Assessing the ecological risks of microplastics typically requires analysis based on microplastic detection results. Historically, microplastic detection has relied on spectroscopic methods, such as infrared microscopy or Raman microscopy, with open-source spectral libraries and software developed for data processing. In recent years, advanced methods such as high-resolution laser confocal Raman spectroscopy and thermal infrared spectroscopy have also been developed for nanoplastics, as shown in Table 1. However, these spectroscopic techniques only provide information on the abundance (quantity concentration) and size of microplastics in a sample, not their mass concentration, making direct comparison with other pollutants or environmental media difficult. Pyrolysis-gas chromatography / mass spectrometry (Py-GC / MS) technology, by quantifying characteristic markers of microplastic pyrolysis, can determine the mass concentration of microplastics in a sample, significantly improving identification capabilities. Currently, Py-GC / MS has been validated to effectively identify 11 common environmental polymers, including polyethylene (PE), polypropylene (PP), polyester fibers, and tire wear particles. However, this technology still cannot resolve the mass concentration of particles in different size ranges. Therefore, current assessments of the ecological risks of microplastics cannot be based on the precise mass concentration of particles in different size ranges.

[0036] Table 1. Detection methods for microplastics and nanoplastics

[0037]

[0038] Based on this, this application provides a method for detecting micron and nanoplastics in soil or sediment. Based on the particle size characteristics of microplastics and the needs of environmental risk assessment, a series of filter membranes (1μm, 220nm, 10nm) are used to achieve particle size classification and separation of microplastics: for micron-sized microplastics (1-5000μm), a 1μm filter membrane is used for retention and measurement; for nano-sized microplastics (<1μm), further based on 220nm as a key size node for transmembrane transport and cytotoxic effects of nanoplastics, 220nm and 10nm filter membranes are used to further subdivide nano-sized microplastics into two ranges: 1000-220nm (larger nanoscale) and 220-10nm (high toxicity potential nanoscale). The mass concentration of these three particle size ranges is accurately determined using Py-GC / MS, providing more precise classification data support for soil microplastic environmental risk assessment and subsequent toxicity mechanism research. This method can, to some extent, solve the problem of insufficient accuracy in current risk assessments of micron and nanoplastics.

[0039] refer to Figure 1 As shown in the embodiments of this application, a method for detecting micron and nanoplastics in soil or sediments is provided. The detection method may include:

[0040] S100 provides a soil or sediment sample to be tested;

[0041] S200, the soil or sediment sample to be tested is pretreated to obtain the solution to be tested;

[0042] S300, the solution to be tested is subjected to multi-stage filtration to obtain microplastic particles in multiple particle size ranges; wherein, the multiple particle size ranges include a first particle size range, a second particle size range, and a third particle size range; the particle size of the first particle size range is 1-5000 μm; the particle size of the second particle size range is 220-1000 nm; and the particle size of the third particle size range is 10-220 nm.

[0043] S400 uses pyrolysis-gas chromatography / mass spectrometry to quantitatively analyze microplastic particles in multiple particle size ranges, obtaining the mass concentration of microplastic particles in multiple particle size ranges.

[0044] In some embodiments, in step S100, the soil or sediment sample to be tested can be obtained by naturally air-drying the collected soil, removing impurities such as gravel, sand, and plant and animal remains, grinding, and sieving. Sieving can remove large mineral particles, plastics, and plant residues with a particle size exceeding 5 mm. This removes naturally occurring minerals (such as kaolinite and illite) and organic matter (such as plant and animal remains) from the soil or sediment sample.

[0045] In some embodiments, step S200, the pretreatment of the soil or sediment sample to be tested to obtain the test solution, may include:

[0046] Sodium bromide solution is added to the soil or sediment sample to be tested, ultrasonically dispersed, and centrifuged to obtain the supernatant. The sodium bromide concentration in the sodium bromide solution is 39-41%, and the volume-to-mass ratio of the sodium bromide solution to the soil or sediment sample can be (9.5-10.5) ml:1 g. The density of the NaBr solution is ρ = 1.39 g / mL. Using sodium bromide solution with these parameters, the density difference between microplastics and soil particles can be utilized to keep the microplastics in a suspended state, thereby separating the microplastics from the soil particles.

[0047] Hydrogen peroxide solution was added to the supernatant, and the reaction was allowed to proceed for 23.5-24.5 hours. The hydrogen peroxide solution contained 29-31% hydrogen peroxide by mass, and the volume ratio of hydrogen peroxide to the supernatant was (0.9-1.1):1. Using this concentration of hydrogen peroxide effectively removed organic matter from the soil and prevented changes in the form of polyethylene.

[0048] In some embodiments, the supernatant can be obtained by mixing supernatants obtained from multiple centrifugations. That is, after obtaining supernatant through suspension, ultrasonic dispersion, and centrifugation, the precipitate is taken again for suspension, ultrasonic dispersion, and centrifugation to obtain supernatant again. This process can be repeated multiple times, and the supernatants obtained each time are mixed. By repeating the process multiple times, the recovery efficiency of polyethylene in the final supernatant can be improved.

[0049] In some embodiments, step S300, the multi-stage filtration of the solution to be tested, may include:

[0050] The solution to be tested is subjected to a first filtration process to obtain microplastic particles with the first particle size range; the pore size of the filter membrane used in the first filtration process is 1 μm. After the first filtration process, microplastic particles with a particle size of 1-5000 μm can be retained on the filter membrane.

[0051] The filtrate obtained from the first filtration process is subjected to a second filtration process to obtain microplastic particles with the second particle size range; the pore size of the filter membrane used in the second filtration process is 0.22 μm. After the second filtration process, nanoplastic particles with a particle size of 220-1000 nm can be retained on the filter membrane.

[0052] The filtrate obtained from the second filtration process is subjected to a third filtration process to obtain microplastic particles with the third particle size range; the molecular weight cutoff of the filter membrane in the third filtration process is 100 kDa. After the third filtration process, nanoplastic particles with a particle size of 10-220 nm can be retained on the filter membrane. That is, the microplastic particles with multiple particle size ranges obtained are microplastic particles loaded on multiple filter membranes, which are the retained products of the filter membranes. The particle sizes of the multiple filter membranes can correspond one-to-one with the multiple particle size ranges.

[0053] In some embodiments, the third filtration process may include transferring the filtrate obtained from the second filtration process into a 100 kDa MWCO (pore size <10 nm) ultrafiltration tube (Millipore), centrifuging it, and obtaining filter residue, which yields nanoplastic particles with a particle size of 10-220 nm.

[0054] In some embodiments, the detection method further includes performing multiple alcohol washes after at least one of the first filtration treatment, the second filtration treatment, and the third filtration treatment to obtain microplastic particles within the corresponding particle size range. This can be understood as performing multiple alcohol washes on the filter residue on the filter membrane obtained from at least one of the first, second, and third filtration treatments to remove soluble organic matter adsorbed on the surface of the microplastic particles, thus avoiding interference with subsequent pyrolysis-gas chromatography / mass spectrometry.

[0055] In some embodiments, the filter membrane material for the first filtration treatment can be stainless steel or alumina; the filter membrane material for the second filtration treatment can be polytetrafluoroethylene or alumina; and the filter membrane material for the third filtration treatment can be regenerated cellulose. Thus, the first, second, and third filtration treatments all use filter membranes with weak adsorption for microplastics, which can reduce microplastic loss to a certain extent and improve the accuracy of microplastic detection.

[0056] In some embodiments, the filter membrane material for the first filtration process can be stainless steel, the filter membrane material for the second filtration process can be polytetrafluoroethylene, and the filter membrane material for the third filtration process can be regenerated cellulose. This method has advantages such as lower cost.

[0057] In some embodiments, step S400, the quantitative analysis of microplastic particles in the multiple particle size ranges using pyrolysis-gas chromatography / mass spectrometry, may include: transferring the microplastic particles in the multiple particle size ranges to a pyrolysis vessel for quantitative analysis. Specifically, microplastic particles loaded with corresponding particle size ranges can be placed in a test tube, methanol solution can be added, and ultrasonic treatment can be performed to resuspend the microplastic particles in the corresponding particle size ranges. Nitrogen blowing concentration is then performed, and the particles are transferred to the pyrolysis vessel in several stages. The principle of pyrolysis-gas chromatography / mass spectrometry (Py-GC / MS) is to depolymerize the polymer of microplastic particles into characteristic small molecule fragments through oxygen-free high-temperature pyrolysis. After chromatographic separation, mass spectrometry accurately captures the polymer-specific ion fragments, and the mass concentration of the original microplastic particles is back-calculated using external standard method, achieving high-precision component identification and absolute quantification of trace microplastics (detection limit down to 0.1 ng) in complex environmental matrices.

[0058] In some embodiments, the types of microplastic particles in the plurality of particle size ranges may include at least one of poly(methyl methacrylate) (PMMA), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), polyethylene (PE), and polyamide (PA). It is understood that each particle size range may independently contain at least one type of microplastic particle.

[0059] In some embodiments, different methanol / dichloromethane mixtures of varying densities can be used to prepare corresponding microplastic standard solutions for different types of microplastic particles. The densities of the methanol / dichloromethane mixtures corresponding to different types of microplastic standard solutions are shown in Table 2.

[0060] Table 2 lists methanol / dichloromethane mixtures suitable for preparing microplastic standard solutions.

[0061] Polymer type Density (g / cm 3 )]]> Methanol / dichloromethane PMMA 1.19 0.34 PP 0.89 4.41 PS 1.03 1.23 PET 1.08 0.85 PE 0.914 3.35 PA 1.25 0.16

[0062] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0063] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0064] Unless otherwise specified, all experimental materials used in the following examples were purchased from conventional biochemical reagent stores.

[0065] Example: Detection of polyethylene microplastic content of different particle sizes in soil

[0066] Experimental design: Given that polyethylene is the dominant polymer in soil microplastic pollution (accounting for 15-20%), it was selected as the experimental polymer.

[0067] Experimental methods:

[0068] Step 1: Preparation of experimental materials

[0069] 1.1 Microplastics and Nanoplastics

[0070] The experiment used polyethylene particles of three sizes: large (80-180 μm), medium (500 nm), and small (100 nm), all purchased from Dongguan Zhangmutou Plastic Exhibition Co., Ltd. The three particle sizes fall within the ranges of 1-5000 μm, 220-1000 nm, and 10-220 nm, respectively. The particle size of the nanoplastics was specifically represented by the median value to avoid boundary effects and potential issues of partial passage or retention.

[0071] 1.2 Preparation of test soil and spiked soil

[0072] The test soil was collected from paddy soil (0-20cm layer) in Beilun District, Ningbo City, Zhejiang Province. After natural air drying, impurities such as gravel, sand, and plant and animal remains were removed, and the soil was ground through a 10-mesh nylon sieve (2mm aperture). Three groups of polyethylene spiked treatments were set up, labeled as: L-PE (large particle size group), M-PE (medium particle size group), and S-PE (small particle size group). Each group had three replicates, and the polyethylene addition amount was 0.015% (w / w). To ensure uniform dispersion of microplastics in the soil, the mixture was stirred for 5 minutes with a stainless steel spatula, and then placed in a shaker and shaken at 200 rpm for 24 hours.

[0073] 1.3 Chemical Reagents

[0074] Sodium bromide (AR, ≥99%) was purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd., and anhydrous ethanol (AR) and hydrogen peroxide (AR, 30%) were purchased from Sinopharm Chemical Reagent Co., Ltd. Methanol (99.9%) and dichloromethane (99.9%) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Ultrapure water for the experiment was prepared using a Milli-Q ultrapure water system (MERCK MILLIPORE).

[0075] Step 2. Pretreatment steps for microplastic treatment in soil

[0076] The separation of PE from soil follows a standardized procedure. To separate PE from soil, the sample undergoes density separation and digestion processes to remove non-digestible substances (such as sand) and organic matter (such as plant residue). Specifically, 1 g of vacuum-dried soil sample is weighed into a glass centrifuge tube, and 10 ml of a 40% sodium bromide solution (NaBr; ρ = 1.39 g / mL) is added to reduce the density of polyethylene (ρ = 1.19 g / cm³). 3 The centrifuge tubes were then suspended. Next, the tubes were ultrasonically treated in a 100W ultrasonic cleaner for 30 minutes, followed by centrifugation at 4000 rpm for 5 minutes. The supernatant (containing polyethylene and some organic matter) was transferred to a glass test tube. This separation process was repeated three times. Subsequently, an equal volume of 30% hydrogen peroxide (H2O2) solution was added to the supernatant, and the mixture was reacted at 60°C for 24 hours.

[0077] Step 3. Quantitative detection of microplastics of different particle sizes in soil samples based on gradient membrane filtration method.

[0078] To obtain a retentate containing L-PE, the digested solution (i.e., the solution obtained in Step 2) was vacuum filtered through a 1 μm pore size stainless steel membrane, and the filter residue was washed three times with anhydrous ethanol. The filtrate was then filtered a second time through a 0.22 μm polytetrafluoroethylene membrane (hydrophilic type), and the filter residue was washed with ethanol in the same manner to obtain a retentate containing M-PE (500 nm). The filtrate was further transferred to a 100 kDa MWCO (pore size <10 nm) regenerated cellulose ultrafiltration tube (Millipore) and centrifuged at 1000 rpm for 10 minutes to obtain a filter residue containing S-PE (100 nm). Filter membranes loaded with PE of different particle sizes can be stored in glass test tubes at room temperature for long-term storage.

[0079] Before pyrolysis-gas chromatography / mass spectrometry analysis, methanol solution was added to a glass tube containing a filter membrane, and the microplastics on the filter membrane were resuspended under sonication. The solution was concentrated with nitrogen blowing (45°C) to approximately 1 mL, and 50 μL of the suspension was injected in fractions into an 80 μL pyrolysis beaker (PY1-EC80F). After each transfer, the methanol was evaporated to dryness in a 90°C oven. Finally, the pyrolysis beaker containing the PE sample was placed in the sample pan of the pyrolysis apparatus for analysis. The analytical instrument for quantifying PE pyrolysis consisted of a pyrolysis apparatus (Japan, EGA / PY-3030D) and a gas chromatography-mass spectrometry (Japan, GCMS-TQ8050). The gas chromatography-mass spectrometry was also equipped with an HP-5MS column connected to the mass spectrometer detector for the separation of PE pyrolysis markers. The specific sample introduction procedure is as follows: The PE pyrolysis marker used is dodecene (CAS No.: 1599-68-4), with characteristic ion fragments of 55, 97, and 69 m / z. The detailed parameters of the pyrolysis mass spectrometer are as follows: carrier gas type is helium, pyrolysis time is 0.2 min, pyrolysis temperature is 600℃, ion source temperature is 250℃, ionization energy is 70 eV, and the temperature program is to hold at 40℃ for 2 min, and then increase to 320℃ at a rate of 20℃ / min.

[0080] Step 4. Quality Control

[0081] The experiment was conducted in a cleanroom (controlled personnel access). All glassware was made of glass / polypropylene and was rinsed three times with ultrapure water and covered with aluminum foil for dust protection before use, minimizing the risk of PE contamination in the environment. The standard curve was prepared using the density solution method: methanol / dichloromethane (3:1, v / v, ρ = 0.914 g / cm³). 3 500nm PE particles were suspended in a mixed solvent to ensure uniform dispersion within the volumetric flask. 50μL of each concentration gradient standard (0.2-100μg) was added to the pyrolysis flask to construct a linear standard curve (R0). 2 =0.998), such as Figure 2b As shown. Total ion chromatograms of PE microplastics of different series and qualities are as follows. Figure 2a As shown. The background value of soil PE (0.0021‰) was also measured, which was only 1 / 714 of the experimental additive concentration (0.015%), and its interference with the recovery rate verification can be ignored.

[0082] Test results: such as Figure 3 As shown in Table 3.

[0083] Table 3. Recovery rates of microplastics in three particle size ranges

[0084] Treatment L-PE M-PE N-PE Recovery 126-90％ 88.8-76.6％ 75.5-65％

[0085] Results analysis: From Figure 3As shown in Table 3, the recovery rate of micron-sized plastic L-PE (particle size > 1 μm) exceeded 90%. However, with the continuous reduction of particle size, the recovery rate of nanoplastics (especially N-PE treatment with particle size of 220 nm-10 nm) decreased significantly. This may be due to the loss of some PE samples caused by physical adhesion during the separation process (such as membrane treatment, rinsing, transfer, etc.). The recovery rates of microplastics of all three particle sizes were greater than 60%. Therefore, the method of this application embodiment can effectively characterize the difference in mass concentration between micron-sized and nanoplastics in soil.

[0086] The method for detecting micron and nanoplastics in soil or sediments provided in this application employs a gradient membrane separation method to achieve precise microplastic particle size classification. By combining weakly adsorbent filter membranes (stainless steel → polytetrafluoroethylene → ultrafiltration membrane), it can sequentially retain microplastics with particle sizes of 1-5000 μm (micron scale), 220-1000 nm (submicron scale), and 10-220 nm (nanoscale). Combined with Py-GC / MS detection, the mass of the retained particles of different sizes is quantified, overcoming the bottleneck of traditional methods that cannot obtain the mass concentration corresponding to each particle size classification. This method solves the problems of spectroscopic detection methods failing to provide the mass concentration of microplastics in the sample, hindering direct comparison with other pollutants or environmental media. It also addresses the issue that traditional microplastic extraction methods, such as Py-GC / MS only providing the total microplastic concentration and failing to distinguish the mass ratio of micron and nanoplastics, lead to a severe underestimation of the true risk of nanoplastics.

[0087] This invention uses gradient membrane separation technology to quantify nanoplastics (10-1000nm), enabling precise assessment and control of microplastics down to the particle size dimension, thereby providing a basis for formulating nanoplastic limit standards and developing targeted remediation solutions.

[0088] Based on the same inventive concept, this application also provides the application of the detection method for micron and nanoplastics in soil or sediment described in any of the above technical solutions in the evaluation or remediation methods for micron and nanoplastics in soil or sediment.

[0089] Based on the same inventive concept, embodiments of this application also provide a method for assessing the risk of micron and nanoplastics in soil or sediments. The assessment method is based on the mass concentration of microplastic particles in multiple particle size ranges obtained by the detection method for micron and nanoplastics in soil or sediments as described in any of the preceding embodiments.

[0090] This application provides a method for assessing the risk of micron and nanoplastics in soil or sediment. Based on the detection method for micron and nanoplastics in soil or sediment as described in any of the previous embodiments, it has the corresponding effects of the detection method for micron and nanoplastics in soil or sediment as described in any of the previous embodiments, which will not be repeated here.

[0091] Based on the same inventive concept, embodiments of this application also provide a method for remediating micron and nanoplastics in soil or sediments, the method being based on the mass concentration of microplastic particles in multiple particle size ranges obtained by the detection method for micron and nanoplastics in soil or sediments as described above.

[0092] This application provides a method for treating micron and nanoplastics in soil or sediment, which is based on the detection method for micron and nanoplastics in soil or sediment as described in any of the previous embodiments. Therefore, it has the same effects as the detection method for micron and nanoplastics in soil or sediment as described in any of the previous embodiments, and will not be repeated here.

[0093] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this disclosure as described above, which are not provided in detail for the sake of brevity.

[0094] Although this disclosure has been described in conjunction with specific embodiments thereof, many substitutions, modifications and variations of these embodiments will be apparent to those skilled in the art from the foregoing description.

[0095] This disclosure is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A method for detecting micron and nanoplastics in soil or sediment, characterized in that, include: Provide soil or sediment samples to be tested; The soil or sediment sample to be tested is pretreated to obtain the test solution; The solution to be tested is subjected to multi-stage filtration to obtain microplastic particles in multiple particle size ranges; wherein, the multiple particle size ranges include a first particle size range, a second particle size range, and a third particle size range; the particle size of the first particle size range is 1-5000 μm; the particle size of the second particle size range is 220-1000 nm; and the particle size of the third particle size range is 10-220 nm. The microplastic particles in the multiple particle size ranges were quantitatively analyzed by pyrolysis-gas chromatography / mass spectrometry to obtain the mass concentration of microplastic particles in the multiple particle size ranges.

2. The detection method according to claim 1, characterized in that, The types of microplastic particles in the multiple particle size ranges include at least one of PMMA, PP, PS, PET, PE, and PA.

3. The detection method according to claim 1, characterized in that, The multi-stage filtration process for the solution to be tested includes: The solution to be tested is subjected to a first filtration process to obtain microplastic particles with the first particle size range; the pore size of the filter membrane used in the first filtration process is 1 μm. The filtrate obtained from the first filtration process is subjected to a second filtration process to obtain microplastic particles with the second particle size range; the pore size of the filter membrane in the second filtration process is 0.22 μm; The filtrate obtained from the second filtration process is subjected to a third filtration process to obtain microplastic particles with the third particle size range; the molecular weight cutoff of the filter membrane in the third filtration process is 100 kDa.

4. The detection method according to claim 3, characterized in that, The filter membrane material for the first filtration treatment is stainless steel or alumina; the filter membrane material for the second filtration treatment is polytetrafluoroethylene or alumina; and the filter membrane material for the third filtration treatment is regenerated cellulose.

5. The detection method according to claim 3, characterized in that, The detection method further includes performing multiple alcohol washes after at least one of the first filtration treatment, the second filtration treatment, and the third filtration treatment to obtain microplastic particles in the corresponding particle size range.

6. The detection method according to claim 1, characterized in that, The pretreatment of the soil or sediment sample to be tested to obtain the test solution includes: Add sodium bromide solution to the soil or sediment sample to be tested, disperse ultrasonically and centrifuge to obtain a supernatant; the mass concentration of sodium bromide in the sodium bromide solution is 39-41%; Add hydrogen peroxide solution to the supernatant and react for 23.5-24.5 h; the mass fraction of hydrogen peroxide in the hydrogen peroxide solution is 29-31%.

7. The detection method according to claim 6, characterized in that, The volume-to-mass ratio of the sodium bromide solution to the soil or sediment sample is (9.5-10.5) ml: 1 g; the volume-to-volume ratio of the hydrogen peroxide to the supernatant is (0.9-1.1):

1.

8. The detection method according to claim 1, characterized in that, The microplastic particles with multiple size ranges are microplastic particles loaded on multiple filter membranes; wherein the particle size of each filter membrane corresponds one-to-one with the multiple particle size ranges; the quantitative analysis of the microplastic particles with multiple size ranges by pyrolysis-gas chromatography / mass spectrometry includes: Microplastic particles in the multiple particle size ranges were transferred to a pyrolysis cup for quantitative analysis.

9. A method for assessing the risk of micron- and nano-plastics in soil or sediment, characterized in that, The evaluation method is based on the mass concentration of microplastic particles in multiple particle size ranges obtained by the detection method for micron and nanoplastics in soil or sediments according to any one of claims 1-8.

10. A method for remediating micron- and nano-plastics in soil or sediment, characterized in that, The remediation method is based on the mass concentration of microplastic particles in multiple particle size ranges obtained by the detection method for micron and nanoplastics in soil or sediment as described in any one of claims 1-8.

Images