An analysis method of micro-nano plastics and their mixed states in the atmosphere based on a biological aerosol single-particle mass spectrometer

Abstract

The application belongs to the technical field of environmental monitoring, and particularly relates to a method for analyzing micro-nano plastics and mixed states thereof in the atmosphere based on a biological aerosol single-particle mass spectrometer. The application discloses a method for analyzing micro-nano plastics and mixed states thereof in the atmosphere based on a biological aerosol single-particle mass spectrometer, which can accurately monitor micro-nano plastics and mixed states thereof with other components in the atmosphere in a single-particle manner online. 91 [C7H7 + ], 104 [C8H8 + ] and 115 [C9H7 + ] can be used as characteristic ions (tracer ions) of PS MNPs, and the relative peak area of 104 [C8H8 + ] is greater than or equal to 0.005, so that particles with PS MNP characteristics can be successfully distinguished from environmental aerosols.

Description

Technical Field

[0001] This invention belongs to the field of environmental monitoring technology, and in particular relates to an analytical method for micro- and nano-plastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer. Background Technology

[0002] Micro- and nanoplastics (MNPs) represent a significant emerging pollution problem globally, while atmospheric micro- and nanoplastics (AMNPs) can serve as carriers for other atmospheric pollutants, acting as reaction interfaces for aerosols, altering their physicochemical properties, and thus influencing the environmental behavior of atmospheric pollutants. However, existing detection methods struggle to characterize MNPs and their mixed states (pollutant interactions) in real time.

[0003] Current research on atmospheric micro / nanoplastics (MNPs) primarily focuses on offline sampling and analysis methods, with almost no research utilizing online sampling and analysis. The main analytical methods for identifying and quantifying MNPs include visual methods, spectroscopic methods, and mass spectrometry (O'brien et al., 2023; Wang et al., 2021). Visual methods involve using stereomicroscopes, fluorescence microscopes, etc. (Li et al., 2023) to obtain the morphology, size, color, and quantity of microplastics, and are widely used for large microplastics (1-5 mm) (Lin et al., 2020). This method is simple but rudimentary (Lin et al., 2020), highly subjective, and cannot provide any chemical information about MNPs. Furthermore, the abundance of microplastics can be overestimated or underestimated due to the quality of the microscope, the shape, color, and size of the microplastic particles. Among spectroscopic methods, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy are currently the mainstream identification techniques for detecting MNP number concentrations, and can simultaneously obtain the morphology, size, and chemical information (microplastic species) of microplastics. FTIR can detect particles as small as 20 μm, while Raman spectroscopy can detect particles as small as 10 μm (Lin et al., 2020). However, these techniques are both time-consuming and labor-intensive when identifying micro- and nano-plastics (Mai et al., 2018; Primpke et al., 2020; Xuet et al., 2020; Fan et al., 2022). Furthermore, the experimental results are susceptible to interference from complex media. Lin et al., 2020 ).

[0004] Among mass spectrometry (MS) methods, pyrolysis gas chromatography-mass spectrometry (Pyr-GC-MS) and TDS-GC-MS are two mainstream analytical methods for detecting the mass concentration of MNPs (Chen et al., 2024). Some studies have also utilized matrix-assisted laser desorption / ionization time-of-flight mass spectrometry (MALDI-TOF MS) based on pyrolysis (Lin et al., 2020). These mass spectrometry methods can obtain the types and mass concentrations of MNPs of any size (Lykkemark et al., 2024). However, since they are all offline analyses, various preprocessing and experimental calibrations are required, which can introduce errors into the detection results. Furthermore, the entire detection process is relatively complex and time-consuming. A literature search revealed only one study reporting online identification and quantification of micro / nanoplastics (MNPs) (Niu et al., 2024), which uses an online high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) to identify and quantify nano-PSMNPs in the atmospheric environment. This is already a major advancement in the field of identifying and quantifying atmospheric micro and nano plastics. However, given that the current method is a whole-sample analysis method, micro and nano plastics account for a very small proportion in the atmosphere, while aerosols are quite complex. When the whole sample is analyzed, it may overestimate the amount of tracer ions of the target analyte and cannot observe the mixing state and particle size of individual particles. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides an analytical method for the analysis of micro- and nano-plastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer, which can accurately monitor micro- and nano-plastics and their mixed states with other components in the atmosphere online.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows: This application provides an analytical method for micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer, including: Obtain standard mass spectra of micro / nanoplastics; A bioaerosol single-particle mass spectrometer was used to sample and analyze the atmosphere at the test site to obtain the particle size and mass spectrometry information of micro- and nano-plastics in the atmosphere at the test site. Based on the characteristic ion extraction method, the number concentration, relative number concentration information and characteristic ion mass spectrum of micro-nanoplastics in the atmosphere at the test site are obtained from the particle size and mass spectrometry information of micro-nanoplastics in the atmosphere at the test site. By comparing standard mass spectra with characteristic ion mass spectra of micro- and nano-plastics, the mixed state of micro- and nano-plastics in the atmosphere was obtained.

[0007] Optionally, obtaining the mixed state of micro-nanoplastics in the atmosphere by comparing standard mass spectra with characteristic ion mass spectra of micro-nanoplastics includes: Observe whether there are any new peaks in the characteristic ion mass spectrum of micro-nanoplastics compared with the standard mass spectrum; When a new peak appears, the type of ion can be determined by the location of the new peak, thus indicating that there is an interaction between that type of ion and the micro / nanoplastics.

[0008] Optionally, the micro / nanoplastics are polystyrene micro / nanoplastics.

[0009] Optionally, the characteristic ions of the polystyrene micro / nanoplastics include: 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + One or more of the following.

[0010] Optionally, the step of obtaining the number concentration, relative number concentration information, and characteristic ion mass spectrum of the micro-nanoplastics in the atmosphere at the test site from the particle size and mass spectrometry information of the micro-nanoplastics at the test site using the characteristic ion extraction method includes: by 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + As a characteristic ion, and 104 [C8H8 + The relative peak area is greater than or equal to 0.005. Based on the particle size and mass spectrometry information of the micro-nanoplastics in the atmosphere at the test site, the number concentration, relative number concentration information and characteristic ion mass spectra of the micro-nanoplastics in the atmosphere at the test site are obtained.

[0011] Optionally, obtaining the standard mass spectrum of micro / nanoplastics includes: aerosolizing an aqueous solution of standard polystyrene, sampling and analyzing it using a bioaerosol single-particle mass spectrometer to obtain the standard mass spectrum of the micro / nanoplastics.

[0012] Optionally, the standard polystyrene aqueous solution can be aerosolized to a particle size of 500 nm.

[0013] Optionally, the laser energy E used for ionization in the bioaerosol single-particle mass spectrometer satisfies: 301.87 ± 6.12 μJ ≤ E ≤ 635.61 ± 33.11 μJ.

[0014] Optionally, the method further includes optimizing the particle size of the aqueous solution of standard polystyrene aerosolized and the laser energy used for ionization by the bioaerosol single-particle mass spectrometer, and then obtaining the standard mass spectrum of the micro / nanoplastics at the optimal particle size and optimal laser energy; the optimization method includes: Aerosolized polystyrene was sampled and analyzed under different ionizing laser energies of bioaerosol single-particle mass spectrometer. By screening, the ionizing laser energy with high integrity and hit rate in the mass spectrum was selected as the optimal laser energy. Under the optimal laser energy for ionization in a bioaerosol single-particle mass spectrometer, aqueous aerosols of standard polystyrene with different particle sizes were sampled and analyzed. By screening, the ratio of the total relative peak area of ​​characteristic ions to the total relative peak area of ​​all fragment ions and the hit rate were selected, and the aerosol particle size corresponding to this condition was taken as the optimal particle size.

[0015] Compared with the prior art, this application has at least the following beneficial effects:

[0016] This invention develops an analytical method for micro- and nano-plastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer, which can accurately monitor micro- and nano-plastics and their mixed states with other components in the atmosphere online from the perspective of a single particle.

[0017] Confirmed 91 [C7H7 + ], 104 [C8H8 + ]and 115 [C9H7 + [Can be used as a characteristic ion (tracer ion) of PS MNPs, while limiting] 104 [C8H8 + The relative peak area of ​​the particles is greater than or equal to 0.005, which can successfully distinguish particles with PS MNP characteristics from environmental aerosols. Attached Figure Description

[0018] Figure 1 A schematic diagram of the experimental procedure in this application; wherein (a) is a schematic diagram of the aerosol generation and collection process in the laboratory; and (b) is a schematic diagram of the aerosol collection and spraying of standard samples outdoors.

[0019] Figure 2 Mass spectra of PS MNPs micro / nanoplastics at different laser energies;

[0020] Figure 3 Mass spectra of PS MNPs micro / nanoplastics at different particle sizes;

[0021] Figure 4The effects of different conditions on the detection of PS MNPs by Bio-SPAMS were investigated; (a) the effect of different laser energies on the detection of PS MNPs; and (b) the effect of different particle sizes on the detection of PS MNPs.

[0022] Figure 5 Mass spectrometry of standard PS MNPs;

[0023] Figure 6 Mass spectrometry analysis of nitropolycyclic aromatic hydrocarbons at 0.5 mJ laser energy;

[0024] Figure 7 Mass spectrometry analysis of polycyclic aromatic hydrocarbons at 0.5 mJ laser energy;

[0025] Figure 8 Mass spectra of standard PS MNPs and incense particles;

[0026] Figure 9 Mass spectra and particle size distributions of standard PS MNPs and their mixture with inorganic salts;

[0027] Figure 10 This is a diagram showing the field detection results of PS MNPs in environmental aerosols in Guangzhou urban area based on Bio-SPAMS; where (ac) represents the concentration of PS MNPs in environmental aerosols. 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + (d) Mass spectrum of PS MNPs characteristic particles detected in the yellow shaded area; (e) Particle size distribution of PS MNPs characteristic particles detected in the yellow shaded area. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings:

[0029] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0030] All reagents and materials used in this example can be purchased routinely. The quantitative experiments involved in the examples were all repeated at least three times, and the results were averaged.

[0031] This application provides an analytical method for micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer, including: Obtain standard mass spectra of micro / nanoplastics; A bioaerosol single-particle mass spectrometer was used to sample and analyze the atmosphere at the test site to obtain the particle size and mass spectrometry information of micro- and nano-plastics in the atmosphere at the test site. Based on the characteristic ion extraction method, the number concentration, relative number concentration information and characteristic ion mass spectrum of micro-nanoplastics in the atmosphere at the test site are obtained from the particle size and mass spectrometry information of micro-nanoplastics in the atmosphere at the test site. By comparing standard mass spectra with characteristic ion mass spectra of micro- and nano-plastics, the mixed state of micro- and nano-plastics in the atmosphere was obtained.

[0032] In some embodiments of the present invention, obtaining the mixed state of micro-nanoplastics in the atmosphere by comparing a standard mass spectrum with the characteristic ion mass spectrum of micro-nanoplastics includes: Observe whether there are any new peaks in the characteristic ion mass spectrum of micro-nanoplastics compared with the standard mass spectrum; When a new peak appears, the type of ion can be determined by the location of the new peak, thus indicating that there is an interaction between that type of ion and the micro / nanoplastics.

[0033] In some embodiments of the present invention, the micro-nanoplastics are polystyrene micro-nanoplastics.

[0034] In some embodiments of the present invention, the characteristic ions of the polystyrene micro / nanoplastics include: 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + One or more of the following.

[0035] In some embodiments of the present invention, the step of obtaining the number concentration, relative number concentration information, and characteristic ion mass spectrum of micro-nanoplastics in the atmosphere at the test site from the particle size and mass spectrometry information of micro-nanoplastics at the test site using the characteristic ion extraction method includes:

[0036] by 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + As a characteristic ion, and 104 [C8H8 + The relative peak area is greater than or equal to 0.005. Based on the particle size and mass spectrometry information of the micro-nanoplastics in the atmosphere at the test site, the number concentration, relative number concentration information and characteristic ion mass spectra of the micro-nanoplastics in the atmosphere at the test site are obtained.

[0037] In some embodiments of the present invention, obtaining the standard mass spectrum of micro / nanoplastics includes: aerosolizing an aqueous solution of standard polystyrene, sampling and analyzing it using a bioaerosol single-particle mass spectrometer, and obtaining the standard mass spectrum of the micro / nanoplastics.

[0038] In some embodiments of the present invention, the standard polystyrene aqueous solution is aerosolized to a particle size of 500 nm.

[0039] In some embodiments of the present invention, the laser energy E used for ionization by the bioaerosol single-particle mass spectrometer satisfies: 301.87 ± 6.12 μJ ≤ E ≤ 635.61 ± 33.11 μJ.

[0040] In some embodiments of the present invention, the method further includes optimizing the particle size of the aqueous solution of standard polystyrene aerosolization and the laser energy used for ionization by a bioaerosol single-particle mass spectrometer, and then obtaining a standard mass spectrum of the micro / nanoplastics at the optimal particle size and optimal laser energy; the optimization method includes:

[0041] Aerosolized polystyrene was sampled and analyzed under different ionizing laser energies of bioaerosol single-particle mass spectrometer. By screening, the ionizing laser energy with high integrity and hit rate in the mass spectrum was selected as the optimal laser energy. Under the optimal laser energy for ionization in a bioaerosol single-particle mass spectrometer, aqueous aerosols of standard polystyrene with different particle sizes were sampled and analyzed. By screening, the ratio of the total relative peak area of ​​characteristic ions to the total relative peak area of ​​all fragment ions and the hit rate were selected, and the aerosol particle size corresponding to this condition was taken as the optimal particle size.

[0042] Since mass spectrometry using lasers as ionization sources currently cannot obtain standard databases, complete standard PS MNPs mass spectra can be obtained by optimizing the detection conditions of the bioaerosol single particle mass spectrometer.

[0043] Example

[0044] This application primarily utilizes a Bio-SPAMS (Nanjing Fengshun Intelligent Technology Co., Ltd.) for laboratory experiments and environmental aerosol sampling. Bio-SPAMS is developed based on the single-particle aerosol mass spectrometry (SPAMS) technology platform and mainly consists of control and acquisition software, a sample introduction system, a particle size measurement system, an ionization system, and a mass spectrometry system. It can realize real-time detection of the particle size and chemical composition information of aerosol single particles and is widely used in the study of aerosol aging and mixing states.

[0045] The instrument's analytical system primarily employs an aerodynamic lens to focus aerosol particles into a particle beam, which is then introduced into a vacuum chamber. The focused particle beam is first subjected to real-time aerodynamic particle size determination (based on the principle of light scattering) using two 532 nm (Nd:YAG) laser beams. Subsequently, the particle's trajectory is precisely calculated by a timing control module. When the target particle reaches the center of the ionization region, a 266 nm ultraviolet pulsed Nd:YAG laser is emitted, simultaneously generating positive and negative ion fragments through laser ablation ionization. The ionization products (ionized products) are then detected by a dual-polarity time-of-flight mass spectrometer (dual TOF-MS), achieving high-resolution mass-to-charge ratio (m / z) characterization with a time resolution down to the microsecond level, enabling the measurement of different chemical components within a single particle.

[0046] To ensure data quality, the Bio-SPAMS was calibrated for particle size and mass spectrometry before the experiment and sampling. The sampling flow rate was set to 0.35 L / min, and the ionization laser energy was adjusted under exploratory conditions. The chemical composition and particle size of the single particles collected by SPAMS were analyzed using MATLAB and COCO V1.3 (the Computational Continuation Core 1.3).

[0047] HR-TOF-AMS (Aerodyne Research Inc., USA) was used to simultaneously acquire standard samples with Bio-SPAMS for comparison. The HR-TOF-AMS sampling flow rate was 1.43 cm³·s⁻¹, the vaporization temperature was set to approximately 600°C, and it was operated in V mode. The acquired HR-TOF-AMS data were analyzed using the Igor-based software toolkits ToolkitSOUIRREL v1.59D and PIKAv1.19D (https: / / cires1.colorado.edu / jimenez-group / wiki / index.php?title=ToF-AMS_Main).

[0048] This application uses a constant-output nebulizer (TSI, model 9302) to aerosolize an aqueous solution of 500 nm monodisperse PS MNPs particles (Thermo Scientific, 8% by mass), and simultaneously acquires and analyzes the data using Bio-SPAMS and HR-ToF-AMS. Sampling was stopped after Bio-SPAMS acquired 5000 mass spectra. The experimental setup is as follows... Figure 1 As shown in a.

[0049] I. Optimization of laser energy and particle size to obtain standard mass spectra

[0050] Six different energy levels (300 μJ – 1550 μJ) were tested under the condition that the standard PS MNPs (polystyrene micro / nanoplastics, purchased from Thermo Scientific) had a particle size of 500 nm. Effect of particle size: Based on optimized laser energy (approximately 380 μJ), the particle sizes of the six standard PS MNPs tested ranged from 0.3 μm to 2 μm (Thermo Scientific, 8 wt%). Specific experiments included: aerosolizing an aqueous solution containing monodisperse standard PS MNP particles using a constant-output nebulizer, followed by acquisition and analysis using Bio-SPAMS. Figure 1 a). To determine the potential for detecting PSMNPs using Bio-SPAMS, mass spectrometry was performed simultaneously using Bio-SPAMS and HR-ToF-AMS, and the results are shown in the figure. Figure 5 (using C8H8) + (Relative intensity calculated from relative peak area or mass concentration).

[0051] Laser energy optimization:

[0052] Detection experiments were conducted on 500 nm PS MNPs at six laser energy levels (300 μJ – 1550 μJ, see Table 1), with 5000 mass spectra acquired at each energy level. The average mass spectra corresponding to different laser energies are detailed in [Table 1]. Figure 2 The effect of different laser energies on the detection of PS MNPs is shown in [reference needed]. Figure 4 a.

[0053] Table 1 Six types of laser energy

[0054]

[0055] The results show that as the laser energy increases, the signal intensity of macromolecular fragment ions decreases in the positive ion mode, for example... 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + In negative ion mode, the types of fragment ions increase, but the main ions (such as m / z) remain the same. 25 [C2H - ], 49 [C4H5 - The signal strength of [] was also significantly weakened. Figure 4 a and Figure 2This phenomenon is consistent with the findings reported by Silva and Prather (2000), which have shown that higher laser energies promote the further fragmentation of large ions into smaller ion species. Therefore, lower laser energies are more conducive to observing large fragment ions, which is crucial for the identification of target compounds and also indicates that complete mass spectra are more easily obtained at lower laser energies.

[0056] Furthermore, laser energy not only affects the mass spectrometry characteristics of particles but also the hit rate of the collected particles. The hit rate reaches its peak, approximately 96.89% to 98.72%, when the laser energy is between 635.61 ± 33.11 μJ and 1166.92 ± 15.74 μJ. Figure 4 a). However, when the laser energy exceeds 635.61 ± 33.11 μJ, the signals of major fragment ions such as C7H7⁺, C8H8⁺, and C9H7⁺ almost disappear, such as Figure 4 a and Figure 2 As shown. Therefore, in order to ensure the presence of major large fragment ions (relatively large mass) while maintaining a high hit rate, the detection laser energy (E) is set between greater than 301.87 ± 6.12 μJ and less than 635.61 ± 33.11 μJ. This range of laser energy ensures a high hit rate during the acquisition process while minimizing excessive fragmentation of particulate matter, thereby preserving the characteristic fingerprint of PS MNPs.

[0057] Particle size optimization:

[0058] Within the optimized laser energy range (301.87 ± 6.12 μJ to 635.61 ± 33.11 μJ), six different PS MNPs (300 nm, 500 nm, 700 nm, 1 μm, 1.4 μm, and 2 μm) were detected using Bio-SPAMS. The results confirm that Bio-SPAMS can effectively detect PS MNPs with particle sizes ranging from 0.3 μm to 2 μm, and can detect major fragment ions (such as C2H⁻, C4H5⁻, C3H3⁺, C4H3⁺, C5H5⁺, C6H5⁺, C7H7⁺, C8H8⁺, and C9H7⁺). Figure 5 and Figure 4 As shown in a.

[0059] However, the relative peak areas of the major fragment ions differ at different particle sizes (see...). Figure 3 and Figure 4 b, Figure 4In b, MIA represents the total relative peak area of ​​the main ion, and TIA represents the total relative peak area of ​​the total ion. MIA / TIA is the ratio of main ion abundance to total ion abundance; MIA / TIA quantitatively assesses the proportion of the main ion in the total ionized products. The C2H⁻ relative peak area of ​​500 nm PS MNPs and 700 nm PS MNPs is significantly larger, while the C8H8⁺ relative peak area of ​​300 nm PS MNPs and 500 nm PS MNPs is larger. Furthermore, we calculated the ratio of the total relative peak area of ​​the main fragment ions to the total relative peak area of ​​all fragment ions (MIA / TIA) to comprehensively evaluate the target analyte detection efficiency. The results showed that 500 nm PS MNPs had the highest MIA / TIA ratio (51.54%), indicating the best detection efficiency for the main fragment ions. Simultaneously, 500 nm PS MNPs also exhibited the highest hit rate of 80.88%. Figure 4 b). These results indicate that PS MNPs with a particle size of 500 nm achieve a good balance between the detection efficiency and hit rate of the main fragment ions, making them the optimal particle size for experimental detection.

[0060] Therefore, the optimized conditions for detecting PS MNPs using Bio-SPAMS are as follows: the laser energy is set between greater than 301.87 ± 6.12 μJ and less than 635.61 ± 33.11 μJ to ensure the presence of major fragment ions while maintaining a high hit rate; when the particle size range is 500 nm to 700 nm, the particles have a high hit rate while ensuring high detection efficiency of major fragment ions in the mass spectrometer.

[0061] When Bio-SPAMS was performed with a laser energy of 384.24 ± 5.68 μJ and a particle size of 500 nm, the obtained PS MNPs mass spectra ( Figure 5 ) exhibits hydrocarbon ions (n[C x H y ± The fragmentation characteristic spectrum is mainly composed of: m / z 25 [C2H] - ]、49[C4H5 - ]、39[C3H3 + ]、51[C4H3 + ]、63[C5H5 + ]、77[C6H5 + ]、91[C7H7 + ]、104[C8H8 + ] and 115[C9H7 +This is highly consistent with the aromatic-aliphatic main chain structure of polystyrene.

[0062] Comparison with HR-ToF-AMS detection results ( Figure 5 Compared to the positive ions of PS MNPs detected by Bio-SPAMS, the positive ions detected by Bio-SPAMS are not only similar to those detected by HR-ToF-AMS (m / z 39[C3H3]), but also... + ]、51[C4H3 + ]、63[C5H5 + ]、77[C6H5 + ]、91[C7H7 + ]、104[C8H8 + ]、115[C9H7 + ] and 193[C 15 H 13 + This aligns with previous research findings by Niu et al. (2024). The mass spectrometry characteristics are consistent with those of styrene in the NIST database, confirming that both platforms can identify the characteristic spectral fingerprints of PS-MNPs.

[0063] However, Bio-SPAMS captured aliphatic fragments (m / z 25[C2H) missing in the HR-ToF-AMS spectrum) in negative ion mode. - ]、49[C4H5 - This difference highlights the advantage of Bio-SPAMS bipolar detection in capturing complex components. Both methods stably detected the m / z 10⁴ (10⁴[C₈H₈]₈) of the corresponding styrene monomer release. + However, the relative intensity of this peak is higher in Bio-SPAMS. These results indicate that Bio-SPAMS can retrieve PS-MNPs by characteristic ions. Figure 5 The mass spectra obtained by Bio-SPAMS were obtained under optimized conditions and can be used as standard mass spectra (fingerprints) for PS MNPs.

[0064] II. Identification of Characteristic Ions

[0065] Due to the complexity of environmental samples, it is impossible to detect all substances that interfere with PS MNPs using standard samples. Therefore, it is necessary to conduct a literature review to statistically analyze the main fragments of various substances in aerosols using single-particle mass spectrometry with laboratory standard samples, and compare the results with those of standard PS MNPs to determine more optimized tracer ions for PS MNPs. The statistical results are shown in Table 2.

[0066] Table 2. Major ions of various substances based on single-particle mass spectrometry (laboratory and environmental samples)

[0067]

[0068] The references are as follows: (3)Li, J. et al. Atmospheric deposition of microplastics in a ruralregion of North China Plain. Science of The Total Environment 2023, 877 , 162947. (4)Lin, Y. et al. Thermal fragmentation enhanced identification and quantification of polystyrene micro / nanoplastics in complex media. Talanta2020, 208, 120478. (5)Mai, L. et al. A review of methods for measuring microplastics inaquatic environments. (1614-7499 (Electronic)). (6)Mai, L. et al. A review of methods for measuring microplastics inaquatic environments. 2018, (1614-7499 (Electronic)). (7)Primpke, S. et al. Critical Assessment of Analytical Methods for the Harmonized and Cost-Efficient Analysis of Microplastics. 2020, 74 , 1012 -1047.

[0069] Table 2 shows that, compared with the main ion fragments of the standard PS MNPs, the ions that may interfere with the detection of PS MNPs mainly appear in OC, BB, and PAH. 25 [C2H - ], 49 [C4H5 - ], 39 [K + ],51 [C4H3 + ], 63 [C5H5 + ]and 77 [C6H5 + Existing research indicates that due to organic carbon (OC) Biomass combustion (BB) and polycyclic aromatic hydrocarbons (PAHs) The organic components are structurally similar to PS MNPs, both containing benzene rings, and thus produce similar ions. This proves that the substances interfering with the detection of PS MNPs mainly come from substances with similar chemical structures.

[0070] Therefore, excluding the above interfering ions and fragment ions 91 [C7H7 + ], 104 [C8H8 + ]and 115 [C9H7 + It may possess the characteristics of labeled ions of PSMNPs. Under optimized conditions, laboratory experiments were conducted to detect eight PAHs in the standard sample (see Table 3), and incense burning experiments were performed to verify this. 91 [C7H7 + ], 104 [C8H8 + ]and 115 [C9H7 + Whether it can be used as a marker ion for PS MNPs, the results show (e.g.) Figure 6 , Figure 7 and Figure 8 (as shown) 91 [C7H7 + ], 104 [C8H8 + ]and 115 [C9H7 + This will not appear simultaneously in the mass spectra of standard PAHs and incense. Figure 6 , Figure 7 and Figure 8 ).therefore 91 [C7H7 + ], 104 [C8H8 + ]and 115 [C9H7 + It can be used as a tracer ion for identifying PS MNPs.

[0071] Table 3 Polycyclic aromatic hydrocarbons (PAHs) and nitro PAHs

[0072] 1 2-nitrofluorene 5 anthracene 2 9-nitroanthracene 6 pyrene 3 3-nitrofluoranthene 7 benz[a]anthracene 4 2,7-dinitrofluorene 8 benzo[a]pyrene

[0073] III. Determination of the Mixing State of Micro- and Nano-Plastics

[0074] The mixed solution was atomized using an atomizer and collected using Bio-SPA-MS under optimized laser energy conditions to obtain particle size and mass spectrometry information. The mixed solution was prepared by mixing 500 nm PS MNPs with equal volumes of ammonium sulfate (AS, 8% by mass, 4 µl) and sodium nitrate (SN, 8% by mass, 4 µl) in ultrapure water.

[0075] The results are as follows Figure 9 (According to C8H8) + The relative intensity obtained from the relative peak area is shown in the mass spectrum of pure PS MNPs. Figure 9 Compared to a), the mass spectra of the mixture showed significantly enhanced signals for nitrate and sulfate ions. Figure 9 (b) indicates that these inorganic substances may be adsorbed on the surface of PS MNPs particles. Furthermore, the particle size distribution of the mixture ( Figure 9 b) The display range is wider, with most particles having a diameter greater than 500 nm. The increased particle size suggests that PS MNPs may be in a state of surface adsorption or mutual encapsulation with sulfates and nitrates. These phenomena demonstrate that Bio-SPAMS can detect the mixed state of PS MNPs.

[0076] IV. Atmospheric Detection Test

[0077] Atmospheric aerosol samples were collected over a three-day period in Huangpu District, Guangzhou, a megacity with a large permanent population and high plastic consumption. During the sampling period, 500 nm PS MNPs particles were sprayed into the air three times, each lasting five minutes. The spray nozzle was 10 cm away from the sampling point (see...). Figure 1 (b) The sampling port is about 9 meters above the ground.

[0078] In this study, within an optimized laser energy range, Bio-SPAMS was used to acquire sample data from April 15th to 18th, 2024. During the sampling period, 500 nm PS MNPs (standard samples) were intermittently sprayed into the atmosphere, resulting in the acquisition of 122,348 mass spectrometry images. We will... 91 [C7H7 + ], 104 [C8H8 + ]and 115 [C9H7 + As a qualitative fragment ion, it is limited to 104 [C8H8 + The relative peak area is greater than or equal to 0.005. 3198 particles with PS MNPs characteristics were successfully identified, accounting for 2.614% of the total number of particles. Figure 10 As shown in a-10c (the purple shaded area represents the 5-minute period when standard PS MNPs were sprayed into the atmosphere, and the yellow shaded area represents the period when environmental aerosols were collected), the peak of the number of particles with PS MNP characteristics occurred during the period when the standard sample was sprayed into the air, showing a significant correlation. Figure 10 a-10c), while all of the atmosphere 91 [C7H7 + ], 104 [C8H8 + ]and 115 [C9H7 + The peak area variation is consistent with the variation in the number of particles with PS MNP characteristics, where 104 [C8H8 + The peak area variation of the tracer ions was most consistent with the spraying time of the standard sample and the variation in the number of particles with PS MNP characteristics, which verified that these tracer ions can extract particles with PS MNP characteristics in complex environmental matrices.

[0079] like Figure 10 As shown in the yellow shaded area (a-10c), a total of 51,045 unlabeled PS MNPs environmental aerosol samples were collected (after 27.5 hours). Figure 10 (a-10c yellow area), the results show that PS MNPs account for approximately 1.04% of the total detected particles ( Figure 10 d-10e), with particle sizes mainly concentrated in the range of 0.3-0.8 μm ( Figure 10 e). Of all PS MNPs, 76.42% showed significant nitrate and sulfate signals ( 97 HSO4 1- ], 96 SO4 2- ], 81 [HSO3 1- ], 80 SO3 2- ] and m / z 62 [NO3 - ], 46 NO2 - ], 30 [NO - The relative peak areas of nitrate and sulfate were 14.30% and 4.06%, respectively. Figure 10 (d) This indicates that PS MNPs interact with atmospheric pollutants to some extent.

Claims

1. A method for analyzing micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer, characterized in that, include: Obtain standard mass spectra of micro / nanoplastics; A bioaerosol single-particle mass spectrometer was used to sample and analyze the atmosphere at the test site to obtain the particle size and mass spectrometry information of micro- and nano-plastics in the atmosphere at the test site. Based on the characteristic ion extraction method, the number concentration, relative number concentration information and characteristic ion mass spectrum of micro-nanoplastics in the atmosphere at the test site are obtained from the particle size and mass spectrometry information of micro-nanoplastics in the atmosphere at the test site. By comparing standard mass spectra with characteristic ion mass spectra of micro- and nano-plastics, the mixed state of micro- and nano-plastics in the atmosphere can be obtained. The micro-nanoplastics are polystyrene micro-nanoplastics; The characteristic ions of the polystyrene micro / nanoplastics are 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + ]; The method of characteristic ion extraction involves obtaining the number concentration, relative number concentration, and characteristic ion mass spectrum of micro-nanoplastics in the atmosphere at the target analyte from the particle size and mass spectrometry information of the micro-nanoplastics at the target analyte. This includes: The characteristic ion extraction method uses the mass spectrum of a single particle as the determination unit; it only considers the simultaneous detection of positive ions in the mass spectrum of the same particle. 91 [C7H7 + ]、 104 [C8H8 + ]and 115 [C9H7 + ],and 104 [C8H8 + When the relative peak area of ​​the particle is greater than or equal to 0.005, the particle is identified as a particle with polystyrene micro / nanoplastics characteristics; based on the identified polystyrene micro / nanoplastics characteristic particles, their number concentration, relative number concentration information and characteristic ion mass spectrum are obtained.

2. The analytical method for micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer according to claim 1, characterized in that, The process of obtaining the mixed state of micro-nanoplastics in the atmosphere by comparing standard mass spectra with characteristic ion mass spectra of micro-nanoplastics includes: Observe whether there are any new peaks in the characteristic ion mass spectrum of micro-nanoplastics compared with the standard mass spectrum; When a new peak appears, the type of ion can be determined by the location of the new peak, thus indicating that there is an interaction between that type of ion and the micro / nanoplastics.

3. The analytical method for micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer according to claim 1, characterized in that, The process of obtaining the standard mass spectrum of micro / nanoplastics includes: aerosolizing an aqueous solution of standard polystyrene, sampling and analyzing it using a bioaerosol single-particle mass spectrometer, and obtaining the standard mass spectrum of the micro / nanoplastics.

4. The analytical method for micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer according to claim 3, characterized in that, The standard polystyrene aqueous solution was aerosolized to a particle size of 500 nm.

5. The analytical method for micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer according to claim 3, characterized in that, The laser energy E used for ionization in the bioaerosol single-particle mass spectrometer satisfies: 301.87 ± 6.12 μJ ≤ E ≤ 635.61 ± 33.11 μJ.

6. The analytical method for micro / nanoplastics and their mixed states in the atmosphere based on a bioaerosol single-particle mass spectrometer according to claim 3, characterized in that, It also includes optimizing the particle size of the aqueous solution of standard polystyrene aerosol and the laser energy used for ionization by the bioaerosol single-particle mass spectrometer, and then obtaining the standard mass spectrum of the micro / nanoplastics at the optimal particle size and optimal laser energy; the optimization method includes: Aerosolized polystyrene was sampled and analyzed under different ionizing laser energies of bioaerosol single-particle mass spectrometer. By screening, the ionizing laser energy with high integrity and hit rate in the mass spectrum was selected as the optimal laser energy. Under the optimal laser energy for ionization in a bioaerosol single-particle mass spectrometer, aqueous aerosols of standard polystyrene with different particle sizes were sampled and analyzed. By screening, the ratio of the total relative peak area of ​​characteristic ions to the total relative peak area of ​​all fragment ions and the hit rate were selected, and the aerosol particle size corresponding to this condition was taken as the optimal particle size.

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