CN115561200A - Method for detecting micro-plastics in landfill body based on micro-infrared technology - Google Patents

Abstract

The invention relates to a method for detecting microplastics in mixed garbage landfills based on microscopic infrared technology, and belongs to the field of new pollutants. It includes the following steps: taking an appropriate amount of mixed landfill materials for pretreatment; using density separation to separate microplastics from most impurities, and obtaining a filter membrane enriched with microplastics by filtration; transferring the filter residue to In a conical centrifuge tube; use a glass glue tip dropper to absorb the particles settled at the bottom of the conical centrifuge tube, and drop it onto a gold-plated glass slide equipped with a square glass hole; wait until the absolute ethanol is completely volatilized, remove the glass hole , the particles on the gold-plated glass slide were detected and identified with a micro-infrared spectrometer, and the type, abundance and size distribution of microplastics were counted. In the present invention, the gold-plated glass slide has excellent infrared signal reflection ability, and has a better identification effect on microplastics; it has the characteristics of high identification rate of microplastics, simple and convenient operation, low cost and the like.

Description

A detection method for microplastics in landfill piles based on micro-infrared technology

technical field

The invention belongs to the field of new pollutants, and more specifically relates to a method for detecting microplastics in landfill piles based on microscopic infrared technology.

Background technique

Microplastics are becoming a major environmental issue. Plastics in the environment will be further broken into smaller plastic fragments, particles or microfibers after physical, chemical and biological degradation. When the particle size of these fine plastics is less than 5mm, it is defined as a new type of pollutant— — Microplastics. A large amount of microplastic pollution in the environment is becoming a major environmental problem that needs to be solved urgently, and the analysis of environmental samples containing microplastics is crucial to determine its prevalence and its impact. Landfills are an important source of microplastics in the environment. However, the composition of landfills is complex, and the detection of microplastics in landfills is a difficult problem.

A range of analytical techniques have been applied to the analysis of microplastics. Among the techniques employed, infrared (IR) spectroscopic analysis, more specifically microscopic IR spectroscopy, is currently one of the main analytical techniques for the detection and identification of microplastics. The routine detection of microplastics in environmental samples using infrared microscopy usually includes the following steps: sample collection, sample purification, infrared sample preparation, data collection and analysis.

Among them, the infrared sample preparation step is a key step in the identification of microplastics, which requires the use of membrane filtration to enrich microplastics on a suitable substrate for infrared detection and analysis. The type of filter used as the substrate needs to not exhibit any significant absorption of infrared light in either transmission or reflection mode, so the usable spectral range of the filter is extremely important. At the same time, the relative cost of each filter is also important, especially for laboratories with high sample throughput, this should be an important consideration.

However, the existing filter membranes cannot simultaneously solve the problems of not having any significant absorption of infrared light and being cost-effective. Glass fiber filter membrane, nitrocellulose filter membrane, polyvinylidene fluoride filter membrane and nylon filter membrane are relatively cheap (the price ranges from 2 to 15 yuan per piece), but they are sensitive to infrared light in transmission or reflection mode. The silicon film, silver film, gold-plated polycarbonate film, aluminum oxide film, etc. have excellent reflection energy or transmission energy, which basically meet the requirements of infrared detection, but they are expensive (the price is between 50-200 yuan) /piece), which makes the cost of the experiment higher.

Since micro-infrared technology was applied to the detection of micro-plastics, different researchers have chosen different carrier filters for enriching micro-plastics in order to meet the needs of the test. Finally, the micro-plastic carrier placed on the detection platform of the micro-infrared spectrometer Not unified. Invention patent "Method for rapid and full inspection of small particle size plastics based on focal plane array infrared technology" (publication number CN113959971A) In order to make infrared detection have a better reflection signal, alumina filter film is used as the carrier of microplastics. The infrared spectrum of the particles was obtained by surface scanning with PFA projection mode under the array infrared detector. Invention patent "A Method for Detecting and Evaluating the Distribution of Microplastics in Packaging Drinking Water Based on Infrared Imaging Technology" (publication number CN113670779A) uses reflection absorption mode for infrared detection, and uses high-reflective glass as the carrier of microplastics for scanning, so as to Obtain an infrared spectrum for each particle. Invention patent "A method for detecting the density distribution of microplastics in water environment sediments" (publication number CN109238948A) collects microplastics on nitrocellulose filter membranes, and uses the transmission mode or attenuation of Fourier transform micro-infrared spectrometer Reflectance pattern identification of microplastics. The patents mentioned above use different microplastic carriers for infrared detection. Different carriers will lead to inconsistencies in the strength of the infrared spectrum signals of the particles obtained. The matching threshold between the particle detection spectrum and the standard substance spectrum (generally ≥70%) There may also be differences due to the strength of the spectral signal, and the final results cannot be compared at the same level.

Therefore, when using a micro-infrared spectrometer to detect microplastics, it is necessary to unify the carrier of microplastics and establish a method that can realize the extraction and enrichment of microplastics, and has high identification accuracy, simple operation, and low cost.

Contents of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides a method for enriching microplastics on a gold-plated glass slide for microscopic infrared spectroscopy scanning, thereby solving the problem of enriching microplastics on a filter membrane for direct visualization. The micro-infrared spectrometer identifies the problem that the filter absorbs infrared light or the cost is high, and the gold-plated glass slide has excellent infrared signal reflection ability, which is better for the identification of microplastics. Finally, the type, abundance, and size of microplastics can be obtained. distributed.

In order to achieve the above object, the present invention provides a method for detecting microplastics in landfill piles based on microscopic infrared technology, comprising the following steps:

(1) Digest the landfill material, and then filter it with a filter membrane to obtain a filter residue; separate the sediment sediment in the filter residue with heavy liquid, and collect the particulate matter;

(2) The particles obtained in step (1) are enriched and transferred to the gold-plated substrate, and then detected by a micro-infrared spectrometer, and the detection spectrum of each particle is compared with the standard substance in the standard spectrum library. Determine whether it is microplastics.

Preferably, in step (2), the particles obtained in step (1) are enriched and transferred to the gold-plated substrate, specifically: the particles are transferred to a conical centrifuge tube with absolute ethanol, and then sucked with a rubber dropper For the particles settled at the bottom of the centrifuge tube, put the dropper cap of the glue tip up and let the particles settle down further; place the perforated sheet on the gold-plated substrate, and drop the settled particles at the bottom of the dropper of the rubber tip into the perforated sheet; After the absolute ethanol volatilized, the particles remained on the gold-plated substrate.

Preferably, in step (1), heavy liquid is used to separate the sediment sediment in the filter residue, and to collect particulate matter, specifically: the filter residue is transferred to a separation container, and the separation container is placed in a petri dish, and the separation The container is connected with a separatory funnel with heavy liquid; open the cock of the separatory funnel, let the heavy liquid enter the separation container, until the liquid level of the separation container reaches the top of the container, close the cock, let stand, and the sediment will settle down; The particulate matter on the liquid surface is transferred to the petri dish by means of overflow; the material obtained by overflowing in the petri dish is filtered with a filter membrane, and the filter residue is the separated particulate matter.

Preferably, the heavy liquid in step (1) is a compound solution of one or more of sodium bromide, sodium iodide and aluminum chloride, with a density of 1.20-1.70 g/cm ³ .

Preferably, the material matching degree threshold is set to 70%, that is, when the detection spectrum of the particle matches the infrared spectrum of the standard substance greater than 70%, it is determined that the particle is a microplastic, and the microplastic type of the particle is the same as the standard substance.

Preferably, the ratio of the total number of microplastic particles of the same type to the mass of the above-mentioned landfill material is the abundance of this type of microplastic.

Preferably, the micro-infrared spectrometer obtains the size of the particles according to the image of the particles; comparing the total number of microplastic particles within a certain size range to the mass of the above-mentioned landfill material, it is the microplastic within the size range. Abundance of plastic.

Generally speaking, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) A method for detecting microplastics in landfill piles based on microscopic infrared technology provided by the present invention, enriching the microplastics in the sample onto a gold-plated glass slide for qualitative and quantitative detection of microscopic infrared spectroscopy, This solves the problem that ordinary filters have significant absorption of infrared or the price of high-reflection filters is high when using the existing base filter membrane to directly detect with a micro-infrared spectrometer, and the gold-plated glass slide has excellent infrared signal reflection ability , the identification effect of microplastics is better, and finally the type, abundance and size distribution of microplastics are obtained.

(2) The separation step provided by the present invention can separate impurities such as silt and microplastics in the sample, and the operation is simple and efficient.

(3) The enrichment step provided by the present invention can transfer all the extracted particles containing microplastics to the gold-plated substrate, and can completely detect the microplastics contained in the sample.

(4) The steps of the method provided by the present invention are clear, simple and easy to implement, and can realize qualitative and quantitative detection of microplastics in landfill piles, and has the characteristics of high microplastic identification rate, easy operation and low cost.

Description of drawings

Figure 1 is a flowchart of the method.

Fig. 2 is the schematic diagram of the density separation device of this method.

Figure 3 is a schematic diagram of the operation of transferring the microplastics to the gold sheet in this method.

Figure 4 uses a gold-plated glass slide as the substrate, and uses a micro-infrared spectrometer to detect the identification results of PE standard particles.

Fig. 5 uses the nylon filter membrane as the substrate, and uses the microscopic infrared spectrometer to detect the identification result of PE standard particles.

Fig. 6 uses the cellulose acetate filter membrane as the base, and the identification result of detecting PE standard particles with a micro-infrared spectrometer.

Fig. 7 uses the glass fiber filter membrane as the substrate, and the identification result of detecting PE standard particles with a micro-infrared spectrometer.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

The present invention is a method for pretreatment and detection of microplastics in mixed landfills based on microscopic infrared technology. Figure 1 is a flow chart of the method, which includes the following steps:

(1) Sample pretreatment: digest the landfill material, filter the digested solution with the first filter membrane; transfer the obtained filter residue to a separation container, which is placed in a glass petri dish, and The separatory funnel filled with heavy liquid is connected with a rubber hose;

(2) Density separation: Open the cock of the separating funnel, let the heavy liquid enter the separation container, until the liquid level of the separation container is close to the top of the container, close the cock, let it stand still, let the sediment and microplastics be completely separated, and then continue to open the separation container. The liquid funnel allows the liquid to continue to enter the separation container, so that the liquid level rises to achieve the overflow effect; the substance floating on the liquid surface is transferred to the glass petri dish by means of overflow; the solution obtained by the overflow in the tray is used for the second Membrane filtration;

(3) Transfer of microplastics: transfer the filter residue on the second filter membrane obtained in step (2) to a glass conical centrifuge tube with absolute ethanol; Put the tube on the rubber dropper rack and let the particles settle down further; place a square glass perforated piece on a gold-plated glass slide and fix it with a dovetail clip; the particles settled at the bottom of the rubber dropper drop into the glass perforated piece; After the absolute ethanol is completely volatilized, the particles containing microplastics are left on the gold-plated glass slide;

(4) Identification of microplastics: The particles on the gold-plated glass slide obtained in step (3) are detected and identified with a microscopic infrared spectrometer (Nicolet iN10); the detection spectrum of each particle is compared with the standard substance in the OMINIC standard spectrum library Compare, determine whether it is microplastic according to the matching degree of substances, and count the types of microplastics.

In some embodiments, the heavy liquid in step (1) can use one or more compound solutions such as sodium bromide, sodium iodide, aluminum chloride, etc., with a density of 1.20-1.70 g/cm ³ .

Preferably, the digestion solution in step (1) uses a H ₂ O ₂ solution with a mass fraction of 30%, a volume of 20-60 mL, a digestion temperature of 40-60° C., and a time of 24-48 h. If the sample has not been completely digested, you can add 10-30mL H ₂ O ₂ solution to continue digestion until the organic matter in the sample is completely digested.

Preferably, the first filter membrane in step (1) is a nylon filter membrane with a pore size of 0.22-20 μm.

Preferably, sodium bromide solution is used as the heavy liquid in step (1), and the density is 1.40-1.60 g/cm ³ .

Preferably, the ultrasonic power in step (1) is 300-400W, the time is 10-20min, and the temperature is 20-30°C.

Preferably, the standing time described in step (2) is 6-12h, and the separation container and glass Petri dish need to be completely covered with aluminum foil during the density separation process to prevent the pollution of microplastics in the air.

Preferably, the density separation step described in step (2) is repeated 2-3 times, and the substance adhering to the outer wall of the separation container is washed to the glass petri dish with heavy liquid to ensure that all the substances floating on the liquid surface are all transferred to the in a glass petri dish.

Preferably, the second filter membrane in step (2) is a nylon filter membrane with a pore size of 0.22-20 μm.

Preferably, the capacity of the pointed-bottom glass centrifuge tube described in step (3) is 20-40mL.

Preferably, the standing time of the glue tip dropper in step (3) is 10-20min.

Preferably, the outer frame of the square glass perforated sheet in step (3) has a side length of 2 cm, the inner frame has a side length of 1-1.5 cm, and a thickness of 2-4 mm.

Preferably, the size of the gold-plated glass slide in step (3) is 75 mm in length and 25 mm in width.

Preferably, the specification of the dovetail clip in step (3) is 15-30mm.

Preferably, the oven drying temperature in step (3) is 50-60°C.

Preferably, the micro-infrared spectrometer described in step (4) adopts the reflective absorption mode to frame the area where the particles are scattered (1.2cm×1.2cm) for automatic scanning, and the spectral scanning range is 600-4000cm- ¹ . The test time is estimated according to the number of particles scanned, and the acquisition time of a single particle is 6-12s.

The present invention provides a method for pretreatment and detection of microplastics in landfill piles based on micro-infrared technology, which specifically includes the following steps:

(1) Sample pretreatment: put the dried landfill sample in a beaker, add 40mL H ₂ O ₂ solution with a mass fraction of 30% to digest the organic matter, the digestion temperature is 40°C, and the time is 24h . Filter the digested solution with a nylon filter membrane with a pore size of ²⁰ μm, and transfer the filter residue to a separation container (a glass cylindrical container with a branched opening, with a bottom surface of The diameter is 4cm, the height is 10cm, and the distance between the branch and the bottom is 4cm). The separation container was subjected to ultrasonic treatment, the ultrasonic power was 400W, the time was 20min, and the temperature was 25°C, and all the filter residue on the first filter membrane was transferred to the separation container. Connect the separatory funnel to the separation container with a rubber tube, put an appropriate amount of heavy liquid in the separatory funnel, and place the separation container in a glass petri dish (diameter of the bottom surface is 10 cm).

(2) Density separation: Open the cock of the separatory funnel, and the heavy liquid in the separatory funnel enters the separation container until the liquid level in the separation container is 5 mm from the top of the container, close the cock, and let stand for 6 hours. During the density separation process, it is necessary to completely cover the separation container and glass Petri dish with aluminum foil to prevent the pollution of microplastics in the air. Open the cock, let the heavy liquid in the separatory funnel enter the separation container, and transfer the material floating on the liquid surface to the glass Petri dish by means of overflow. Rinse the substances adhering to the outer wall of the separation vessel to the glass petri dish with heavy liquid, and ensure that all the substances floating on the liquid surface are transferred to the glass petri dish. Filter the solution obtained by overflowing the glass culture dish with a nylon filter membrane with a pore size of 0.45 μm to obtain a second filter membrane containing microplastics. Fig. 2 is the schematic diagram of the density separation device of this method.

(3) Transfer of microplastics: transfer the filter residue on the second filter membrane to a conical centrifuge tube with a capacity of 30 mL with absolute ethanol. Use a glass dropper to absorb the particles at the bottom of the conical centrifuge tube, and place the dropper on the stand for 20 minutes. Place a square glass perforated piece (the outer frame side length is 2cm, the inner frame side length is 1.2cm, and the thickness is 3mm) on the gold-plated glass slide, and fix it with a dovetail clip (15mm). Particles containing microplastics settled at the bottom of the plastic dropper after standing still, and dropped into the glass perforated piece fixed on the gold-plated glass slide. The pipette suction step can be repeated 2-3 times to ensure that all the particles at the bottom of the conical centrifuge tube are transferred to the gold-plated glass slide. Put the gold-plated glass slide in an oven at 60°C to dry, let the absolute ethanol evaporate completely, leaving only particles containing microplastics on the gold-plated glass slide. Figure 3 is a schematic diagram of the operation of transferring the microplastics to the gold sheet in this method.

(4) Micro-infrared identification: remove the dovetail clamp and the square glass opening, and detect and identify the particles on the gold-plated glass slide with a micro-infrared spectrometer. Using the reflective absorption mode, the area where the particles are scattered (1.2cm×1.2cm) is framed for automatic scanning. The spectral range is 600-4000cm- ¹ . The test time of a single detection sample is estimated according to the number of particles scanned. The collection time of a single particle 6s. Compare the detection spectrum of each particle with the standard substances in the OMINIC standard spectrum library, and determine whether it is a microplastic according to the degree of substance matching. When the matching degree between the detection spectrum of the particle T and the infrared spectrum of the standard substance t is greater than 70%, it is determined that the particle T is a microplastic, and the type is the same as that of the standard substance t, and the type of microplastic is counted. Preferably, the statistical method of the size distribution in step (4) is: respectively calculating the abundance of microplastics in the ranges of <100 μm, 100-500 μm, 500-1000 μm and >1000 μm.

The following are specific examples:

Example 1

A method for pretreatment and detection of microplastics in landfills based on micro-infrared technology, comprising the following steps:

Sample preparation: 50 pieces of blue polyvinyl chloride (hereinafter referred to as PVC) with a particle size of 1000 μm (hereinafter referred to as PVC) and 1 g of sand (repeated density separation 3 times to remove microplastics) were thoroughly mixed, and simulated landfill soil samples were set up for three repetitions.

Sample pretreatment: put the weighed mixed landfill mass into a beaker, and add 30mL of 30% H ₂ O ₂ solution for digestion. Use the first filter membrane made of nylon material with a pore size of 20 μm to filter the digested landfill, and the first filter membrane after filtration is ready for use;

Density separation: Place the first filter membrane in a separation container, add 45mL of saturated sodium bromide solution, cover the glass bottle with aluminum foil, and ultrasonicate at 25°C with 400W power for 20min. Take out the first filter membrane, connect the separation container with a separatory funnel filled with saturated sodium bromide solution, perform density separation, and obtain a solution containing microplastics through overflow. Use a second filter membrane made of nylon material with a pore size of 0.45 μm to filter the solution obtained from the overflow, and use the second filter membrane after filtration;

Microplastics recovery: Count the number of PVC particles on the second filter membrane, which are ①50, ②50, and ③50. The recovery rates are 100.00%, 100.00%, and 100.00%, respectively, and the average recovery rate is 100.00%.

Example 2

A method for pretreatment and detection of microplastics in landfills based on micro-infrared technology, comprising the following steps:

Microplastics transfer: Wash the microplastics on the second filter membrane obtained in Example 1 with absolute ethanol into a conical glass centrifuge tube, use a glass glue tip dropper to absorb the microplastics settled at the bottom of the conical glass centrifuge tube, After standing still, add it dropwise on a gold-plated glass slide with a glass opening. After the absolute ethanol volatilizes, put it into the landfill pile of a micro-infrared spectrometer for testing. During the test, the reflective absorption mode is used, and the area where the particles are scattered (1.2cm×1.2cm) is framed for automatic scanning. The spectral range is 600-4000cm- ¹ , and the acquisition time of a single particle is 6s, and the infrared scanning results are obtained.

Result analysis: A total of 50 PVC microplastics were detected, and the transfer rate was 100%; the matching degree between PVC microplastics and the standard material PVC was 80-95%.

Example 3

A method for detecting microplastics in landfills based on microscopic infrared technology, comprising the following steps:

Sample preparation: take the landfill soil (the depth of landfill is 30cm) in the landfill heap collected in the landfill site as the experimental material, take the landfill soil sample of 1g drying, and based on embodiment 1 and embodiment The device and method described in 2 were verified by actual operation, repeated 3 times, and the average value of the abundance of microplastics was taken.

Sample pretreatment: put the weighed landfill mass into a beaker, add 30mL of H ₂ O ₂ solution with a mass fraction of 30% for digestion. Use the first filter membrane made of nylon material with a pore size of 20 μm to filter the digested landfill, and the first filter membrane after filtration is ready for use;

Density separation: Place the first filter membrane in a separation container, add 45mL of saturated sodium bromide solution, cover the glass bottle with aluminum foil, and ultrasonicate at 25°C with 400W power for 20min. Take out the first filter membrane, connect the separation container with a separatory funnel filled with saturated sodium bromide solution, perform density separation, and obtain a solution containing microplastics through overflow. Use a second filter membrane made of nylon material with a pore size of 0.45 μm to filter the solution obtained from the overflow, and use the second filter membrane after filtration for standby;

Identification of microplastics: The second filter membrane is put into a micro-infrared spectrometer for testing. The reflective absorption mode is used in the test, and an area of 1.2cm*1.2cm is randomly selected for automatic scanning. The spectral range is 600-4000cm- ¹ , and the acquisition time of a single particle is 6s, and the infrared scanning results are obtained. Compare the infrared detection spectrum of each particle with the standard substance of the band library contained in the infrared spectroscopy system, determine whether it is a microplastic according to the judgment standard, and determine the type of microplastic. The judgment standard is: when the detection spectrum of the particle T When the matching degree of the infrared spectrum with the standard substance t is greater than 70%, it is determined that the particle T is a microplastic, and the type is the same as the standard substance t.

Result analysis: The results showed that a total of 868 particles were scanned, of which 119 were identified as microplastics. However, the matching degree of all the particles and the standard substance is lower than 70%, and the result is judged according to the threshold of 70%, so the test result is not credible.

Example 4

A method for detecting microplastics in landfills based on microscopic infrared technology, comprising the following steps:

Sample preparation: take the landfill soil (the depth of landfill is 30cm) in the landfill heap collected in the landfill site as the experimental material, take the landfill soil sample of 1g drying, and based on embodiment 1 and embodiment The device and method described in 2 were verified by actual operation, repeated 3 times, and the average value of the abundance of microplastics was taken.

Sample pretreatment: put the weighed landfill soil into a beaker, add 30mL of 30% H ₂ O ₂ solution for digestion. Use the first filter membrane made of nylon material with a pore size of 20 μm to filter the digested landfill, and the first filter membrane after filtration is ready for use;

Density separation: Place the first filter membrane in a separation container, add 45mL of saturated sodium bromide solution, cover the glass bottle with aluminum foil, and ultrasonicate at 25°C with 400W power for 20min. Take out the first filter membrane, connect the separation container with a separatory funnel filled with saturated sodium bromide solution, perform density separation, and obtain a solution containing microplastics through overflow. A second filter membrane made of nylon material with a pore size of 0.45 μm is used to filter the solution obtained from the overflow, and the second filter membrane after filtration is set aside for use.

Microplastics transfer: wash the microplastics on the second filter membrane with absolute ethanol into a conical bottom glass centrifuge tube, use a glass dropper to absorb the microplastics settled at the bottom of the conical bottom glass centrifuge tube, and add dropwise after standing Put it on a gold-plated glass slide with a glass hole, and put it into a micro-infrared spectrometer for testing after the absolute ethanol has evaporated. During the test, the reflective absorption mode is used, and the area where the particles are scattered (1.2cm×1.2cm) is framed for automatic scanning. The spectral range is 600-4000cm ^-1 , and the acquisition time of a single particle is 6s, and the infrared scanning results are obtained.

Identification of microplastics: compare the infrared detection spectrum of each particle with the standard substance of the band library contained in the infrared spectroscopy system, determine whether it is a microplastic according to the judgment standard, and determine the type of microplastic. The judgment standard is: when the particle When the matching degree between the detection spectrum of T and the infrared spectrum of the standard substance t is greater than 70%, it is determined that the particle T is a microplastic, and the type is the same as the standard substance t.

Result analysis: count the abundance, type and size distribution of microplastics. The results showed that the average abundance of the final microplastics was 193/g; the types of microplastics detected were polyvinyl alcohol, urea-formaldehyde resin, chlorinated polypropylene, epoxy resin, polyethylene, polyurethane, polyoxymethylene, phenolic Resin, polyvinyl chloride, polystyrene, polyethylene terephthalate, polymethyl methacrylate, polyterephthalamide, etc., accounting for 25.88%, 24.71%, 10.59%, 7.06%, respectively 7.06%, 5.88%, 4.71%, 4.71%, 2.35%, 2.35%, 2.35%, 1.18%, 1.18%; size distribution >1000μm accounted for 8.29%, 500-1000μm accounted for 11.40%, 100-500μm accounted for 24.87%, <100μm accounted for 55.44%.

Comparative example 1

A method for detecting microplastics in landfills based on microscopic infrared technology, comprising the following steps:

Sample preparation: Prepare purchased PE standard particles with a particle size of 200 μm.

Identification of microplastics: PE standard particles are based on gold-plated glass slides, placed under a micro-infrared spectrometer for scanning, the spectral range is 600-4000cm ^-1 , and the collection time of a single particle is 6s to obtain the infrared scanning results.

Result analysis: The test results are shown in Figure 4. The result of identifying the particles is PE, and the matching degree is 84.13%, reaching the 70% credible threshold.

Comparative example 2

A method for detecting microplastics in landfills based on microscopic infrared technology, comprising the following steps:

Sample preparation: Prepare purchased PE standard particles with a particle size of 200 μm.

Identification of microplastics: PE standard particles are based on nylon filter membrane, placed under a micro-infrared spectrometer for scanning, the spectral range is 600-4000cm ^-1 , the collection time of a single particle is 6s, and the infrared scanning results are obtained.

Result analysis: The test results are shown in Figure 5. The result of identifying the particles was PE, but the matching degree was only 57.06%, which did not reach the 70% credible threshold.

Comparative example 3

A method for detecting microplastics in landfills based on microscopic infrared technology, comprising the following steps:

Sample preparation: Prepare purchased PE standard particles with a particle size of 200 μm.

Identification of microplastics: PE standard particles are based on cellulose acetate filter membrane, and placed under a micro-infrared spectrometer for scanning. The spectral range is 600-4000cm ^-1 , and the collection time of a single particle is 6s to obtain the infrared scanning results.

Result analysis: The test results are shown in Figure 6. The result of identifying the particles was PE, but the matching degree was only 47.75%, which did not reach the 70% credible threshold.

Comparative example 4

A method for detecting microplastics in landfills based on microscopic infrared technology, comprising the following steps:

Sample preparation: Prepare purchased PE standard particles with a particle size of 200 μm.

Identification of microplastics: PE standard particles are based on glass fiber filter membranes and placed under a micro-infrared spectrometer for scanning. The spectral range is 600-4000cm ^-1 , and the collection time of a single particle is 6s to obtain the infrared scanning results.

Result analysis: The test results are shown in Figure 7. The result of identifying the particles was PE, but the matching degree was only 54.42%, which did not reach the 70% credible threshold.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (7)

1. A method for detecting micro-plastics in a refuse landfill body based on a micro-infrared technology is characterized by comprising the following steps:

(1) Digesting the landfill material, and then filtering by adopting a filter membrane to obtain filter residue; separating sediment in the filter residue by using heavy liquid, and collecting particles;

(2) Enriching the particulate matters obtained in the step (1), transferring the particulate matters onto a gold-plated substrate, detecting by using a microscopic infrared spectrometer, comparing the detection spectrum of each particle with standard substances in a standard spectrum library, and determining whether the particles are micro-plastics according to the substance matching degree.

2. The method for detecting the micro-plastics in the landfill body based on the micro-infrared technology as claimed in claim 1, wherein in the step (2), the particulate matters obtained in the step (1) are enriched and transferred to a gold-plated substrate, and specifically: transferring the particles into a pointed centrifugal tube by using absolute ethyl alcohol, then absorbing the particles settled at the bottom of the centrifugal tube by using a rubber-head dropper, and standing the rubber-head dropper with a rubber cap upwards to further settle the particles; placing an opening sheet on a gold-plated substrate, and dripping particles settled at the bottom of a rubber head dropper into the opening sheet; after the absolute ethyl alcohol is volatilized, the particles are remained on the gold-plated substrate.

3. The method for detecting the micro-plastics in the landfill body based on the micro-infrared technology as claimed in claim 1 or 2, wherein in the step (1), the sediment in the filter residue is separated by heavy liquid, and particulate matters are collected, specifically: transferring the filter residue into a separation container, placing the separation container in a culture dish, and connecting the separation container with a separating funnel filled with heavy liquid; opening a cock of the separating funnel, allowing heavy liquid to enter the separating container until the liquid level of the separating container reaches the top of the container, closing the cock, standing, and settling the silt; transferring the particles floating on the liquid surface into a culture dish in an overflow mode; and filtering the substance obtained by overflowing in the culture dish by using a filter membrane, wherein the filter residue is the particulate matter obtained by separation.

4. The method for detecting the micro-plastics in the landfill body based on the micro-infrared technology as claimed in claim 1, wherein the heavy liquid in the step (1) is one or more compound solutions of sodium bromide, sodium iodide and aluminum chloride, and the density is 1.20-1.70g/cm ³ 。

5. The method according to claim 1, wherein the threshold value of the degree of matching of the substance is set to 70%, that is, when the degree of matching between the detected spectrum of the particle and the infrared spectrum of the standard substance is greater than 70%, the particle is determined to be a micro plastic, and the type of the micro plastic of the particle is the same as that of the standard substance.

6. The method of claim 5, wherein the amount of the same type of microplastic is determined by the mass of the landfill material, i.e., the abundance of the same type of microplastic.

7. The method for detecting the micro-plastics in the landfill body based on the micro-infrared technology as claimed in claim 1, wherein the micro-infrared spectrometer obtains the size of the particulate matter according to the image of the particulate matter; and (3) comparing the total number of the micro plastic particles in a certain size range with the mass of the refuse landfill material, namely the abundance of the micro plastic in the size range.

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