Quantitative detection method for micro-plastics in landfill

Abstract

The invention discloses a quantitative detection method for micro-plastics in landfill, and belongs to the field of environmental pollutant detection. The method comprises the following steps: (1) completely mixing garbage samples of different landfill ages and a leaching solution in a colorimetric tube by adopting a saturated NaCl and NaI mixed solution as the leaching solution, and inverting for gt; adding a saturated salt solution into the garbage sample for 12 hours, releasing the micro-plastics in the garbage sample into the saturated salt solution, and standing to obtain a suspension containing the micro-plastics and the garbage sinking to the bottom, so as to obtain an extracting solution; (2) during separation, adding a saturated salt solution with the same density into another container such as a beaker and the like, soaking the opening of the colorimetric tube in the saturated salt solution, slowly opening a plug to enable a garbage sample sinking to flow out, and taking out the sample after the sample is completely removed from the colorimetric tube and the plug is plugged; and (3) carrying out vacuum suction filtration on the leaching solution in the colorimetric tube by using a 0.45 mu m water-based filter membrane, and retaining the micro-plastic on the filter membrane. In the separation process, macroscopic micro-plastics are picked out for statistics; (4) during digestion, putting the obtained filter membrane into a beaker, adding 20ml of 30% H2O2 and 10% KOH, sealing with tinfoil, digesting at 60 DEG C for 24 hours, and performing vacuum suction filtration by using a 0.45 mu m water-based filter membrane after digestion is completed; and (5) dyeing the filter membrane, observing by using a fluorescence microscope, and analyzing data. According to the invention, the problem that the micro-plastic in the landfill garbage is difficult to detect is solved, and the accuracy of micro-plastic detection is improved.

Description

Technical Field

[0001] The present application relates to the field of environmental pollutant detection, and specifically to a quantitative detection method for microplastics in landfill waste. Background Art

[0002] Landfills are the ultimate sink for plastic waste in terrestrial ecosystems. About 300 million tons of plastic waste are generated worldwide each year, accounting for more than 10% of annual municipal solid waste, and more than half of them are buried in landfills. Due to economic growth and urbanization, the number of landfills and the accumulation of plastics are increasing. Plastic waste often undergoes a long and complex stabilization process in landfills, gradually breaking from large pieces of plastic into fine plastic fragments to form microplastics (diameter <5 mm). The microplastics gradually formed in the landfill can be released back into the environment through surface runoff, leachate, aerosol or land reuse. In addition, microplastics are also carriers of pollutants such as heavy metals, antibiotics, and resistance genes in landfills. Due to the matrix characteristics of landfill waste such as heterogeneity and complex components, in addition, the waste components also degrade and change with the landfill process; and the source components of microplastics in landfills are complex. Therefore, it is still very challenging to separate and identify microplastics in landfill waste.

[0003] Microplastic separation technology in environmental media such as soil / sediment mainly includes extraction and impurity removal purification process. Due to the complexity of the sample matrix, it is difficult to identify microplastics in the sample without purification and separation. Therefore, extracting and separating microplastics from the sample matrix is ​​one of the important steps in quantitative detection. At present, the methods for extracting and separating microplastics from soil and other media mainly include density separation, digestion, screening, filtration, etc. Commonly used digestion methods include acid digestion (nitric acid, hydrochloric acid or mixed acid), alkaline digestion, oxidative digestion and enzyme digestion. Acid digestion can remove macromolecular organic matter in a short time, with good digestion effect and high efficiency, but acid digestion is a relatively drastic method for removing organic matter, which will cause varying degrees of damage to microplastics. For example, when HNO3 is used as a digester, it will cause the loss of certain types of polymers, such as polyethylene terephthalate plastics (PET) or even disappearance, such as polyamide (PA). Compared with acid digestion, alkaline digestion is milder and has a relatively weak effect on the structure of microplastics. Commonly used alkaline digesters include NaOH and KOH. In the oxidative digestion method, H2O2 is widely used to remove organic matter, and it has almost no degradation effect on most microplastic particles. Enzymatic digestion is harmless to the environment and is not easy to affect the subsequent detection of microplastics. However, the disadvantage of enzymatic digestion is that it is relatively expensive, and the digestion efficiency varies greatly for different samples. At present, there are only a few enzyme digestion reagents for samples, and its application is still limited. The sieving method is to pass the naturally air-dried or dried soil samples through a stainless steel or copper sieve to initially separate microplastics from larger particles and impurities. This method can be used as a pretreatment for density separation. Filtration is often used to separate microplastics from liquids, such as separating microplastics in water environments. Filtration is also often used to further filter microplastics out of the liquid phase after density separation or chemical digestion. However, the filter membrane material used for filtration has different degrees of influence on the subsequent detection of microplastics such as infrared spectroscopy and Raman spectroscopy, and filter membranes with different pore sizes have different filtering capabilities for microplastics.

[0004] At present, the main methods for identifying and identifying separated microplastics are: manual selection visual inspection, stereo microscope observation, electron scanning microscopy, Fourier infrared spectroscopy, Raman spectroscopy, etc. Visual inspection is difficult to identify tiny particles, prone to misjudgment, and underestimates the abundance of microplastics in environmental media. Stereo / electron scanning microscopes have difficulty distinguishing non-plastic particles with similar structures to microplastics, resulting in identification errors and biased results. Fourier infrared usually has point scanning and surface scanning. Point scanning requires researchers to distinguish suspected microplastic particles and then further collect spectra. It takes a short time, has a small amount of data, but has a high false positive rate; surface scanning is for the instrument to automatically scan all areas of the stage. The false positive rate is low but it takes a long time and has a large amount of useless data. Raman spectroscopy is not suitable for detecting samples containing fluorescent substances. Samples containing fluorescent substances will cause spectral instability, resulting in inaccurate measurement results.

[0005] Publication No. CN115307987A discloses a method for batch separation and extraction of microplastics from film-covered farmland soil. The method extracts microplastics from soil by ultrasound, centrifugation, stirring and filtration in sequence, takes pictures by stereo microscope, and counts with Nano software to obtain the abundance of microplastics extracted from soil samples. This method uses olive oil in the extraction process. Although plastic is lipophilic and can absorb most microplastics well, oil separation is not suitable for separating small-size microplastics, and stereo microscopes are difficult to distinguish non-plastic particles with similar structures to microplastics, which can easily cause recognition errors and produce result deviations.

[0006] Publication No. CN113720844A discloses a quantitative analysis method for soil microplastics in a biological soil crust layer. The method uses corn germ oil to extract and separate microplastics in the sample. During the filtration process, 2-3 ml of anhydrous ethanol is used to rinse the filtration funnel, microporous filter membrane and glass rod, and the rinse liquid is poured into a conical flask for standing and stratification; the obtained oil layer solution is diluted with corn germ oil and fixed to 25 ml. 12.5 ml is taken out from the fixed solution and added to a 25 ml volumetric flask, and the volume is fixed to 25 ml. Repeat this step 3 times, set 3 levels of concentration, then 1, 2, and 3 levels of concentration, each level of concentration is half of the previous level of concentration, and finally obtain a sample of 3 levels of concentration. Extract 50 μl of samples of different dilution levels and drop them on a slide for observation under a microscope. First, observe with a 10x eyepiece and a 4x objective lens, select five areas of the four vertices and intersection of the two diagonals of the oil droplet for observation, and record the number of microplastics respectively; switch the objective lens to a 40x oil lens, and subdivide each observation area into five sub-areas according to the above division method, observe and record the number and area of ​​microplastics respectively, and after recording, use a 140°C high-temperature probe for heating, use a microscope to observe and record the number of objects with changed morphological structures, record the number of microplastics, and complete the quantitative analysis of soil microplastics in the biological soil crust layer by conversion. During the high-temperature probe heating process, an experimental group was set up every 20°C starting from 100°C, and the number of microplastics deformed was recorded. The individual size and number of microplastics at different temperatures were analyzed and compared, and the quantitative relationship between temperature and microplastic extraction rate was established to obtain the most suitable temperature for observing the morphological changes of microplastics. The pretreatment process of this method is cumbersome, and corn germ oil is also not suitable for separating microplastics in soil with small particle size (<0.1mm) and complex composition. Heating and conversion are also required during the observation process, which is time-consuming.

[0007] Authorization No. CN107632077B authorizes a method for quantifying microplastics in landfill leachate. The principle of this invention is to centrifuge the sediment in the landfill leachate and use advanced oxidation technology to oxidize and remove the surface organic matter. The sediment obtained by centrifugation is dissolved with an organic solvent and adsorbed with a magnetic selective adsorbent and purified by elution with an organic solvent. The total abundance of seven phthalates (PAEs) is determined by gas chromatography-mass spectrometry, and the total abundance of PAEs is used to characterize the abundance of microplastics. However, gas chromatography-mass spectrometry can only obtain abundance values, and cannot obtain multiple information such as the particle size, area, and shape of each microplastic.

[0008] Publication No. CN117554152A discloses a method for extracting and detecting microplastics in laver. The laver is placed in a digestion solution, stirred and then allowed to stand for digestion; a salt solution is added to the digested system, stirred thoroughly and allowed to stand until the supernatant is clear, and then filtered; the steps of adding salt solution-standing-filtering are repeated multiple times, and the final filter residue is dried to obtain microplastics; a sample preparation microscope is used to quantitatively analyze the microplastics, and an infrared spectrometer is used to qualitatively analyze the microplastics; the infrared spectrum identification used in this method can only detect microplastic particles >200μm.

[0009] Publication No. CN108181154A discloses a method for detecting microplastics in biological samples, wherein the biological samples are obtained by enzyme digestion and acid digestion, stained and fluorescently counted using silanization technology, and finally the types of plastics are characterized and analyzed using Fourier infrared spectroscopy and electron microscopy. The enzyme digestion method is harmless to the environment and is not likely to affect the subsequent detection of microplastics, but the disadvantage of the enzyme digestion method is that it is relatively expensive, and the digestion efficiency varies greatly for different samples. At present, there are only a few enzyme digestion reagents for samples, and its application is still limited.

[0010] Publication No. CN117990672A discloses a method for detecting microplastics from earthworm tissue. It includes S1: obtaining an earthworm sample without excrement in the intestine; S2: taking the earthworm sample, cutting it into pieces, soaking it in KOH, and digesting it in a shaker for half an hour; S3: vacuum filtering the digestion solution onto a polycarbonate nuclear track etched filter membrane; S4: placing the filter membrane in a centrifuge tube, adding a saturated ZnCl2 solution and then ultrasonicating; taking out the filter membrane, washing the filter membrane with a saturated salt solution, and centrifuging the washing liquid; S5: vacuum filtering the upper layer of liquid onto a new polycarbonate nuclear track etched filter membrane; S6: placing the new filter membrane in an oven to dry overnight; S7: fluorescent staining with Nile red reagent and counting. The microplastic content in a single earthworm is calculated based on the number of observed microplastics. The calculation formula is as follows: microplastic content = n / m (pieces / piece), where n is the number of microplastics (pieces) and m is the number of earthworms. The staining process of this method is simple, but uneven staining may occur, resulting in the possibility of missed detection, and the observation time is relatively long.

[0011] Authorization number CN113640084B authorizes a method for detecting microplastics in farmland soil, including: primary digestion, primary flotation and particle-grade filtration of soil samples, wherein the primary digestion uses Fenton reagent as the digestion solution, and after particle-grade treatment, ATR-FTIR and 8700LDIR are used for detection. This method sequentially digests, dries, flots, filters, dissolves in ethanol, and concentrates with nitrogen before testing on the machine. Nitrogen concentration is not suitable for processing a large number of samples. When using a nitrogen blower, it is necessary to control the nitrogen flow rate and temperature to prevent the sample from evaporating too quickly or decomposing. Compared with other concentration methods, such as rotary evaporation, nitrogen concentration usually takes longer to complete the sample concentration process.

[0012] Publication No. CN112284867A discloses a method for separating and extracting residual microplastics in soil. This method uses sulfuric acid in the purification process, but sulfuric acid is corrosive to microplastics themselves and may cause changes in the morphology of microplastics, thereby interfering with subsequent identification.

[0013] Publication No. CN114964988A discloses a method for detecting microplastics, wherein a hydrophobic organic solvent is mixed with a sample to be detected, and a mixed stratified solution is obtained by extraction, wherein the mixed stratified solution includes a solvent layer, a two-phase interface layer and a sample layer; and the two-phase interface layer is detected by confocal Raman spectroscopy and qualitative and quantitative analysis is performed. Confocal Raman spectrometers are expensive, and the operation of confocal Raman spectroscopy is relatively complicated, and the detection time may be long. Confocal Raman spectroscopy has certain requirements for samples, such as the sample needs to have a certain thickness and uniformity, otherwise it may affect the quality of the spectrum, especially when processing a large number of samples, it is easy to be interfered by pigments or other impurities on the surface of the sample, which may affect the accuracy of the test results.

[0014] At present, there are still few methods for quantitative detection of microplastics in landfill waste, and the data on the abundance, particle size, morphology, etc. of waste of different landfill ages are still incomplete. Microplastics seriously threaten the ecological environment and human health. Therefore, exploring a detection method for microplastics in landfill waste is of great significance for monitoring landfill waste pollution. Summary of the invention

[0015] The present invention provides a method for quantitatively detecting microplastics in landfill waste, aiming to improve at least one of the problems mentioned in the technical background.

[0016] A quantitative detection method for microplastics in landfill waste, comprising:

[0017] (1): Extract and separate microplastics from garbage of different landfill ages;

[0018] (2): Vacuum filter the suspension to retain the microplastics on the filter membrane;

[0019] (3): Digestion of organic matter in the extract;

[0020] (4): Microplastic staining;

[0021] (5): Detection and data analysis.

[0022] In a first aspect, the present invention provides a method for extracting and separating microplastics from landfill waste, comprising two steps of extraction and separation.

[0023] The extraction uses a saturated NaCl and NaI mixed solution as the leaching solution. After the test samples such as garbage are completely mixed with the leaching solution in a colorimetric tube, the tube is inverted for >12 hours to release the microplastics in the test samples into the saturated salt solution. After standing, a suspension containing microplastics and garbage that has settled to the bottom are obtained to obtain an extract.

[0024] Specifically, during separation, take another beaker or other container and add a saturated salt solution of the same density, immerse the mouth of the colorimetric tube in the saturated salt solution, slowly open the stopper to allow the garbage sample that has settled to the bottom to flow out, and after all the samples are removed from the colorimetric tube, plug it tightly and take it out; the extract in the colorimetric tube is vacuum filtered using a 0.45μm water filter membrane, and the microplastics are retained on the filter membrane. During the separation process, pick out the microplastics visible to the naked eye for statistics.

[0025] In a second aspect, the present invention provides a method for digesting organic matter in an extract to reduce the effect of organic matter on the identification of microplastics. The digestion process includes two steps: H2O2 digestion and KOH digestion.

[0026] During digestion, the filter membrane obtained above was placed in a beaker, 20 ml of 30% H2O2 and 10% KOH were added, and then sealed with tin foil. Digestion was performed for 24 hours. After digestion, vacuum filtration was performed using a 0.45 μm water filter membrane.

[0027] In a third aspect, the present invention provides a Nile red staining method, wherein the reagents required for staining include: Nile red, methanol solution and dimethyl sulfoxide solution.

[0028] Place the filter membrane after suction filtration in a 250 ml beaker and add 15 ml of dimethyl sulfoxide solution;

[0029] Add 2 ml of Nile red solution to the beaker and heat at 25°C for 10 min, then add 2 ml of Nile red solution and heat at 50°C for 20 min, then add 2 ml of Nile red solution and heat at 75°C for 30 min;

[0030] After the heating is completed, the beaker is cooled in a water bath, and the cooled solution is placed on a polytetrafluoroethylene filter membrane for vacuum filtration.

[0031] Before using the polytetrafluoroethylene filter membrane for vacuum filtration, five lines are drawn in equal proportions on the rough surface of the filter membrane to facilitate subsequent observation.

[0032] In a fourth aspect, the present invention provides a method for characterizing and counting microplastics using a fluorescence microscope.

[0033] Place the filter membrane obtained from the above experiment on a glass slide, select blue excitation light using a fluorescence microscope, and characterize the microplastics on the filter membrane under a 10x objective lens.

[0034] Visual image acquisition was performed by taking pictures along 5 horizontal lines of the filter without overlapping.

[0035] After obtaining the microplastic images, the identified microplastics were quantitatively analyzed using ImageJ software, and statistical information such as the size and shape of each microplastic will also be displayed in the final report.

[0036] The total abundance of microplastics per gram of litter was calculated based on the number of observed microplastics.

[0037] The present invention explores and optimizes the extraction process of microplastics, then stains them with Nile red, uses a fluorescent microscope to observe the morphological characteristics of microplastics, and counts them by estimating the whole from the local part. Studies have shown that the present invention is suitable for detecting the abundance and particle size of microplastics in landfill waste.

[0038] The beneficial effects of the present invention are:

[0039] 1) The detection method of the present invention is applicable to landfill waste with complex components.

[0040] 2) During the microscopic observation process, the method of the present invention adopts a method of estimating the whole by the local part, which greatly saves the detection time.

[0041] 3) The method of the present invention is simple to operate, has low detection cost, and mild processing conditions, and provides a new idea for the detection of microplastic environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 is a flow chart of the steps of the present invention;

[0044] Figure 2 It is an example of the counting method of the present invention;

[0045] Figure 3 This is an example of the present invention under a fluorescence microscope;

[0046] Figure 4 This is a map of the abundance of microplastics in a landfill;

[0047] Figure 5 The distribution diagram of microplastic particle size (a) and shape (b) in a landfill. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0049] This embodiment uses garbage samples that have been landfilled for less than 10 years, landfilled for 10 to 25 years, and landfilled for ≥ 30 years as examples to apply the method of the present invention, and the specific process is as follows:

[0050] like Figure 1 As shown, the basic process for detecting microplastics in landfill waste is as follows:

[0051] Step 1: Pre-process the garbage sample

[0052] Step 1.1 Allow the garbage samples of different landfill ages to air dry naturally. Be careful to avoid microplastic contamination in the air during air drying. Pass the samples through a 10-mesh metal sieve.

[0053] Step 2: Microplastic Extraction

[0054] Step 2.1: Preparation of saturated NaCl-NaI solution: Accurately weigh 340 g of NaCl and dissolve it in water and dilute to 1 L. Then weigh 170 g of NaI and dissolve it in 100 ml of water. Ultrasonicate at 50 kHz for 30 min to make the solution saturated.

[0055] Step 2.2: Weigh 0.25 g of garbage sample and place it in a 50 ml colorimetric tube. Add saturated NaCl solution (1.2 g / cm 3 ) and NaI (1.5 g / cm 3 ) and dilute to 50 ml, vortex for 5 minutes and then invert for 12 hours to release the microplastics in the garbage into the saturated salt solution. After standing, a suspension containing microplastics and solid garbage that has settled to the bottom are obtained.

[0056] Step 3: Microplastic Separation

[0057] Step 3.1: Take another 500ml beaker, add a saturated salt mixed solution of the same density, immerse the mouth of the colorimetric tube in the saturated solution, slowly open the stopper to allow the solid sample to flow out, and wait until all the samples are removed from the colorimetric tube, plug it tightly and take it out.

[0058] Step 3.2: The extract in the colorimetric tube is vacuum filtered using a 0.45 μm water filter membrane to retain the microplastics on the filter membrane.

[0059] Step 4: Digestion of organic matter

[0060] Step 4.1: Place the filter membrane obtained in the previous step in a 150 mL beaker, add 20 ml of 30% H2O2 and 10% KOH digestion solution, seal with tin foil, and digest at 60°C for 24 hours.

[0061] Step 4.2: The digested filter membrane is vacuum filtered (0.45 μm water filter membrane), and rinsed with deionized water at least 3 times, and the obtained filter membrane is transferred to another beaker.

[0062] Step 5: Dyeing

[0063] Step 5.1: Prepare reagents (1) Dimethyl sulfoxide solution: dimethyl sulfoxide solution and deionized water are mixed in a volume ratio of (1:1). (2) 10 mg / L Nile red solution: Weigh 0.01 g of Nile red and add methanol solution to make up to 100 ml. Take 10 ml of the 100 ml solution and add methanol solution to make up to 100 ml. The resulting solution is 10 mg / L. Store in a brown bottle in a 4°C refrigerator.

[0064] Step 5.2: Place the filter membrane after the above digestion and filtration in a 150 ml beaker and add 15 ml of dimethyl sulfoxide solution.

[0065] Step 5.3: Add 2 ml of Nile red solution to the beaker and heat at 25°C for 10 min. Then add 2 ml of Nile red solution and heat at 50°C for 20 min. Then add 2 ml of Nile red solution and heat at 75°C for 30 min.

[0066] Step 5.4: After heating is completed, the beaker is cooled in a water bath. The cooled solution is placed on a polytetrafluoroethylene filter membrane for vacuum filtration and rinsed with deionized water at least three times to reduce the microplastics remaining in the beaker and obtain the microplastics attached to the filter membrane.

[0067] Step 5.5: Before using the polytetrafluoroethylene filter membrane for vacuum filtration, five lines of equal proportions are drawn on the rough surface of the filter membrane for subsequent observation.

[0068] Step 6: Microscope observation

[0069] Step 6.1: Place the filter membrane obtained in the above experiment on a glass slide with the hairy side facing down and the shiny side facing up. Use a fluorescence microscope (DM2500, Leica, Germany) to select 2 levels of blue excitation light and observe the MP on the filter membrane under a 10x objective lens. S Specific parameters: exposure intensity (102.1ms), gain (5), saturation (1.5) and gamma (1.00), shading (50%). Take photos along 5 horizontal lines of the filter without overlapping to collect visual images, such as Figure 3 shown.

[0070] Step 6.2: Take photos along the five horizontal lines of the filter membrane without overlapping, and measure the area of ​​one photo under a microscope to be 0.8114 cm 2 The whole membrane area is 1256cm 2 .

[0071] Step 6.3: After obtaining the microplastic image, save the image in JPG format and use ImageJ software to quantitatively analyze the identified microplastics.

[0072] Step 7: ImageJ operation process

[0073] Step 7.1: Drag the captured image into the software box, click on the straight line, draw a straight line from the leftmost to the rightmost side of the image, click on Analyze, select the Set Scale option, fill in the known length 1040 in Know distance, and change Unit oflength to μm, click on Global to get the standard size.

[0074] Step 7.2: Click Analyze, select the Set Measurement option, and select the required data options on the given page, including: Shape descriptors, Feret's diameter, etc.

[0075] Step 7.3: Click Image, select the Adjust option, select Color Threshold, adjust the fluorescence intensity, and select the corresponding particle range based on the fluorescence intensity.

[0076] Step 7.4: Click Analyze, select Analyze Particles, and change Size (μm 2 ) to 20-Infinity and click OK.

[0077] The software will automatically identify the selected particles, and the final results will be displayed in the report. If you are in doubt about the results, you can reselect the fluorescence intensity identification and repeat the above process to reduce errors. All data can be exported and saved in CSV format.

[0078] The total abundance of microplastics per gram of litter was calculated based on the number of observed microplastics.

[0079] In this example, 9 microplastics were observed in the sample, and 83 photos were taken. The following were calculated based on the microscopic examination area:

[0080]

[0081] It can be calculated that x≈168, that is, there are 238 microplastics in 0.25g of garbage, and it can be inferred that there are 671 microplastics in every gram of garbage.

[0082] The detection method of the present invention is used to detect garbage samples of different landfill ages, and the abundance statistical data results are shown in Figure 4 .

[0083] The detection method of the present invention is used to detect garbage samples of different landfill ages, and the statistical data of particle size and shape are shown in Figure 5 .

[0084] Based on the detection results of the above embodiments, it can be seen that the method provided in the embodiments of the present application has good feasibility, reduces the detection cost, is easy to operate, and improves the detection efficiency.

[0085] The above are preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field shall, within the technical scope disclosed by the present invention, make any changes or substitutions according to the technical solution of the present invention, which shall be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A quantitative detection method for microplastics in landfill waste, characterized in that: The following steps are involved: (1) Extract and separate microplastics from garbage of different landfill ages; (2) vacuum filtering the suspension to trap the microplastics on the filter membrane; (3) digesting organic matter in the extract; (4) Microplastic staining; (5) Detection and data analysis.

2. The quantitative detection method of microplastics in landfill waste according to claim 1, characterized in that: The saturated salt solution in step (1) has a density of 1.2 g / cm 3 NaCl solution and 1.5 g / cm 3 of NaI solution.

3. The method for quantitative detection of microplastics in landfill waste according to claim 1, characterized in that: The conditions for the ultrasonic treatment in step (1) are 50 kHz for 30 min and standing for 24 h.

4. The method for quantitative detection of microplastics in landfill waste according to claim 1, characterized in that: The separation and extraction process of step (1) is to pour a saturated salt solution of the same density into a 500 ml beaker, immerse the mouth of the colorimetric tube in the saturated salt solution, slowly open the stopper to allow the sample to flow out, and after all the sample is removed from the colorimetric tube, tighten the stopper and take it out.

5. The method for quantitative detection of microplastics in landfill waste according to claim 1, characterized in that: In the step (2), a 0.45 μm water filter membrane is used for vacuum filtration.

6. The method for quantitative detection of microplastics in landfill waste according to claim 1, characterized in that: In the step (3), the digestion reagent is a solution of 30% H2O2 and 10% KOH, and the reaction condition is 60°C for 24 hours.

7. The method for quantitatively detecting microplastics in landfill waste according to claim 1, characterized in that: In the step (4), the filtered filter membrane is placed in a beaker, 20 ml of dimethyl sulfoxide solution (dimethyl sulfoxide: water = 1:1) is added thereto, and the mixture is allowed to stand at 25°C for 10 min, 50°C for 20 min, and 75°C for 30 min, and 2 mL (10 mg / L) of Nile red solution is added at the beginning of each temperature condition.

8. The method for quantitative detection of microplastics in landfill waste according to claim 1, characterized in that: In the step (4), the cooled solution is placed on a polytetrafluoroethylene (PTFE) filter membrane for vacuum filtration.

9. The method for quantitative detection of microplastics in landfill waste according to claim 1, characterized in that: In the step (5), photos are taken along the five horizontal lines of the filter membrane without overlapping. After the microplastic image is obtained, the image is saved in JPG format, and the microplastics are quantitatively analyzed using ImageJ software.

Images