Usnea spinosa-based plant carrier in-situ monitoring method for atmospheric polycyclic aromatic hydrocarbons and derivatives thereof

Abstract

The invention relates to a plant carrier in-situ monitoring method for atmospheric polycyclic aromatic hydrocarbons and derivatives thereof based on usnea spinifera, and belongs to the technical field of monitoring methods. The technical problems that an existing PAHs monitoring method needs to be supported by an environment monitoring station and an atmosphere monitoring sampler, a large amount of labor and cost are consumed, and large-scale pollution monitoring of PAHs and SPAHs in remote mountainous areas is not facilitated are solved. The method comprises the following steps: cleaning, freeze-drying, crushing and sieving usnea spinifera to obtain an usnea spinifera powder sample, extracting, drying and concentrating to obtain an extracting solution; then loading the extract to an activated silica gel column for elution, and carrying out gas pushing on the obtained eluent; and finally, concentrating the gas-pushed liquid, and carrying out gas chromatography-triple quadrupole mass spectrometer detection. According to the method, usnea spinosa is used as an air pollutant accumulation carrier, large-area high-resolution monitoring of PAHs and SPAHs pollution in remote mountainous areas can be completed, and effectiveness and accuracy are high.

Description

Technical Field

[0001] This invention belongs to the field of monitoring method technology, specifically relating to an in-situ monitoring method of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa using a plant carrier. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are semi-volatile, highly toxic, environmentally persistent, bioaccumulating, and capable of long-distance migration. They can migrate to remote areas and harm the local ecological environment and human health, thus attracting widespread attention.

[0003] Substituted polycyclic aromatic hydrocarbons (SPAHs), like PAHs, are often generated and released into the environment by human activities. However, they have stronger biotoxicity, environmental persistence, and bioaccumulation, posing a greater risk to the environment and human health. They are currently recognized as emerging organic pollutants, including oxidized polycyclic aromatic hydrocarbons (O-PAHs), nitro-PAHs, bromo-PAHs, and chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs).

[0004] Currently, the main methods for monitoring environmental PAHs are manual sampling of soil and water samples, and instrumental sampling of atmospheric samples. Among these, the monitoring of atmospheric PAHs is divided into two types: atmospheric sample monitoring and biological sample monitoring.

[0005] Atmospheric sample monitoring refers to the process of collecting atmospheric samples through various media, separating PAHs from the media using physicochemical methods, and then performing qualitative and quantitative analysis of the PAHs using organic chemical analysis techniques. Atmospheric sample monitoring is mainly divided into two categories: active sampling methods and passive sampling methods.

[0006] The selection of sampling media for active sampling is basically finalized, and the technology is relatively mature, capable of accurately obtaining atmospheric volume. However, it requires power facilities, on-site maintenance, and is complex to operate, making it less feasible in remote areas or high-altitude environments. This method uses a sampling pump to pass a certain volume of air sample through an adsorbent and an absorbent liquid, where organic matter is adsorbed onto the adsorbent or into the absorbent liquid. Based on the sampling flow rate, active sampling can be divided into low-flow, medium-flow, and high-flow sampling. Low-flow sampling is suitable for volatile organic compounds (VOCs) existing in a gaseous state, some semi-volatile organic compounds (SOCs), and samples collected using absorbent liquids. For SOCs, absorbent liquids, filter membranes, and polyurethane foam are generally used for adsorption sampling. Medium-flow and high-flow sampling are mainly suitable for collecting substances existing in aerosol form, or for sampling SOCs with very low concentrations in the environment that require large-volume concentration. Extraction was performed using methods such as microwave-assisted extraction, supercritical fluid extraction, accelerated solvent extraction, ultrasonic extraction, matrix dispersion solid-phase extraction, purge-and-trap, subcritical water extraction, and fluidized bed extraction. Analytical analysis was performed using gas chromatography-mass spectrometry (GC-MS), GC-MS / MS, liquid chromatography-mass spectrometry (LC-MS), and high-resolution chromatography / mass spectrometry (HRGC / HRMS).

[0007] Passive sampling, also known as diffusion sampling, is a more convenient and feasible method than active sampling. Passive sampling equipment is not powered, is simpler to operate, and is more feasible in remote areas. It utilizes the diffusion principle of air pollutants; by placing an adsorbent in the air for a period of time, organic matter gradually diffuses onto the adsorbent, thus achieving the sampling purpose. Currently, commonly used passive samplers include polyurethane foam samplers (PUF), resin passive samplers (XAD), semi-permeable membrane devices (SPMDs), and solid-phase microextraction (SPME). Passive sampling serves as an auxiliary method to active sampling, with sampling times ranging from several weeks to several months.

[0008] Instrumental sampling methods based on atmospheric samples can quickly and accurately reflect the concentration levels of atmospheric PAHs in densely populated towns and industrial areas, offering advantages in air pollution early warning and control. However, this method relies on sampling instruments, electricity, and manual intervention, making it difficult to implement in remote, sparsely populated areas. Furthermore, the process of eluting and separating PAHs from the sampling medium is cumbersome and prone to distorting the results.

[0009] Biological carrier monitoring is a passive sampling method that uses vegetation as a passive sampler for atmospheric pollutants, reflecting the long-term pollution levels of atmospheric organic pollutants. Currently, various organisms are used as accumulation carriers for atmospheric pollutants, including single plants such as bark, pine needles, and mosses, and biocomplexes such as lichens. Gaseous and particulate atmospheric organic pollutants enter and remain in lichens for extended periods through dry and wet deposition processes. Lichen carrier monitoring can be implemented at multiple spatial scales and resolutions, and the sampling method is simple and easy to implement. It is applicable to the spatial and temporal trends of organic pollutant variations and is a powerful monitoring tool for atmospheric pollution in remote and high-altitude areas. However, analytical techniques for PAHs and SPAHs in the atmosphere of remote areas of my country are currently lacking.

[0010] Furthermore, domestic and international air pollution regulatory systems primarily target parent PAHs, generally neglecting SPASHs. However, research indicates that SPASHs may possess stronger direct toxicity and carcinogenicity than parent PAHs. Moreover, under urban photochemical processes, some PAHs can transform into SPASH derivatives. In actual monitoring and analysis, there is often an overemphasis on PAHs while ignoring these derivatives, resulting in incomplete monitoring data and inaccurate analytical results. Therefore, expanding the monitoring scope from parent PAHs to include both the parent PAHs and their derivatives has become an inevitable trend in environmental regulation. Although the health and environmental risks of SPASHs are increasingly prominent, due to their relatively late discovery and systematic research, no effective regulatory framework has been established domestically or internationally, and standard analytical methods for SPASHs are also lacking. Against this backdrop, developing an analytical method capable of simultaneously and efficiently analyzing parent PAHs and various types of SPASHs is particularly urgent and important. Summary of the Invention

[0011] This invention addresses the challenges of existing PAHs monitoring methods, which rely on atmospheric samples collected from environmental monitoring stations and atmospheric samplers. These methods require manual deployment and maintenance of instruments and manual sample collection, which is difficult to implement in remote mountainous areas due to limited accessibility to monitoring stations, transportation difficulties, and power shortages. Furthermore, the elution and separation of PAHs from the collected medium is cumbersome and prone to distorting results. Existing technologies also neglect the technical challenges of SPOHs pollution monitoring. This invention provides an in-situ monitoring method for atmospheric polycyclic aromatic hydrocarbons and their derivatives using a plant carrier based on Usnea spinulosa. This method, tailored to the organic composition characteristics of Usnea spinulosa, establishes a gas chromatography-triple quadrupole mass spectrometry (GC-MS / MS) quantitative analysis technique for PAHs and SPOHs in Usnea spinulosa samples based on cross-validation and comprehensive comparative analysis of various analytical techniques.

[0012] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows.

[0013] The present invention provides an in-situ monitoring method for atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa as a plant carrier, using Usnea spinulosa as an accumulation carrier for air pollution, comprising the following steps: Step 1: Take Usnea spinulosa, wash it, freeze-dry it, pulverize it and sieve it to obtain Usnea spinulosa powder sample, extract it, dry it and concentrate it to obtain the extract; Step 2: Load the extract onto an activated silica gel column for elution to obtain the eluent, then perform air jetting to obtain the air-jet liquid; Step 3: Concentrate the gas-propelled liquid and perform gas chromatography-triple quadrupole mass spectrometry to obtain a total ion chromatogram of polycyclic aromatic hydrocarbons and their derivatives, thereby obtaining the composition and content of polycyclic aromatic hydrocarbons and their derivatives in Usnea sp. (to reflect the degree of pollution of polycyclic aromatic hydrocarbons and their derivatives in the atmosphere). The polycyclic aromatic hydrocarbon derivatives include one or more of oxidized polycyclic aromatic hydrocarbons (O-PAHs), nitro-PAHs, bromo-PAHs, and chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs).

[0014] Preferably, the polycyclic aromatic hydrocarbon includes one or more of naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, α, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indo[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, and benzo[g,h,i]perylene.

[0015] Preferably, the brominated polycyclic aromatic hydrocarbons (Br-PAHs) are one or more of 2-bromofluorene, 9-bromophenanthrene, 9-bromoanthracene, 2,7-dibromofluorene, and 7-bromobenzo[a]anthracene.

[0016] Preferably, the chlorinated polycyclic aromatic hydrocarbon is one or more of 2-chloroanthracene, 9-chloroanthracene, and 2,7-dichlorofluorene.

[0017] Preferably, the nitro-PAHs are one or more of 5-nitroacenaphthene, 2-nitrofluorene, 3-nitrofluoranthene, and 1-nitropyrene.

[0018] Preferably, the oxidized polycyclic aromatic hydrocarbons (O-PAHs) are one or more of benzo[a]anthracene-7,12-dione and 5,12-naphthoquinone.

[0019] Preferably, in step one, the visible attached debris on the surface of the thorny Usnea is first removed with tweezers under a stereomicroscope, and then washed with pure water.

[0020] Preferably, in step one, the sieving is done through a 60-mesh sieve.

[0021] Preferably, in step one, the extraction agent used is a mixture of acetone and n-hexane with a volume ratio of 1:1, the extraction temperature is 100°C, the extraction pressure is 100 bar, the extraction time is 5 min, the extraction is performed twice, and the nitrogen purging time is 2 min.

[0022] Preferably, in step one, the drying is performed using anhydrous sodium sulfate.

[0023] Preferably, in step one, the concentration is concentrated to 1-2 mL.

[0024] Preferably, in step two, the activation method of the silica column is as follows: first, wash the silica column with 10 mL of dichloromethane at a flow rate of 5 mL / min, then wash the silica column with 5 mL of n-hexane at a flow rate of 5 mL / min. After the 5 mL of n-hexane fills the gel column, let it soak for 5 min, and continue to activate the silica column with 5 mL of n-hexane at a flow rate of 10 mL / min until the silica column bed is completely wetted by n-hexane and equilibrated. The specification of the silica column is 1 g: 6 mL (the mass of the silica adsorbent packed in the silica column is 1 g, and the volume of the silica column is 6 mL).

[0025] Preferably, in step two, the flow rate of the sample loading is 1 mL / min.

[0026] Preferably, in step two, 2 mL of n-hexane is used to wash the container holding the extract twice at a flow rate of 10 mL / min, and the resulting washing solution is loaded onto the sample at a flow rate of 1 mL / min.

[0027] Preferably, in step two, the elution process is as follows: first, elute with 5 mL of n-hexane and dichloromethane in a volume ratio of 1:9 at a flow rate of 1 mL / min, pause for 1 min, and then continue eluting with 10 mL of n-hexane and dichloromethane in a volume ratio of 1:9 at a flow rate of 1 mL / min, and collect all the eluent.

[0028] Preferably, in step two, the flow rate of the air jet is 10 mL / min, and the volume is concentrated to 1 mL.

[0029] Preferably, in step three, the concentration is achieved by nitrogen purging.

[0030] Preferably, in step three, the operating conditions of the gas chromatograph are as follows: Inlet temperature: 280℃; Carrier gas: high-purity (purity not less than 99.999%) helium, splitless injection; Column: Select PAH quartz capillary column, 30m 0.25mm 0.15μm; Column flow rate: 1.0mL / min in constant flow mode; Temperature program: 80℃ for 2 min; increase to 250℃ at a rate of 10℃ / min and hold for 2 min; then increase to 315℃ at a rate of 8℃ / min and hold for 5 min; increase to 340℃ at a rate of 20℃ / min and hold for 10 min. Injection volume: 1 μL.

[0031] Preferably, the operating conditions for the triple quadrupole mass spectrometer are as follows: Electron impact ionization (EI) source, ionization energy 70 eV, collision gas is high-purity (purity not less than 99.999%) argon; Ion source temperature: 320℃; Transmission line temperature: 310℃; Select scan mode: SRM, solvent delay 5 min.

[0032] It should be noted that obtaining the composition and content of polycyclic aromatic hydrocarbons and their derivatives in Usnea sp. based on total ion chromatogram is an existing technology. Qualitative ion identification is performed, and quantitative ion identification is performed based on peak area. The internal standard method is preferred to improve the accuracy of quantification.

[0033] The principle of this invention is as follows: Usnea aciculifera is a symbiotic complex of algae and fungi. It has an extremely low ability to absorb substances from the soil, but a strong capacity to accumulate PAHs and SPAHs from atmospheric dry and wet deposition. The content of organic pollutants in its body is often higher than that of other plants. Usnea aciculifera is a perennial biocomplex widely distributed in the mountain forests from Inner Mongolia to Yunnan, and globally distributed in China, Japan, India, and Nepal in Asia. Usnea aciculifera attaches to the bark with rhizoids at its base, making it easy to collect from the bark. It forms a small shrub-like structure from the base to the top, typically about 4-6 cm tall when mature. The branches have dense, irregularly shaped, white, powdery, barkless patches called powdery buds. The presence of these powdery buds makes this plant more prone to accumulating atmospheric depositional substances than other plants.

[0034] Usnea spinulosa is a symbiotic complex of algae and fungi. Compared with other plants, this biological complex has the following advantages: 1) It has a wider geographical distribution, being widely distributed in forests (China, Japan, India, and Nepal), especially in the mountain forests from Inner Mongolia to Yunnan in my country. Therefore, it can be used for large-scale environmental monitoring and comparative analysis, particularly in remote areas. 2) The symbiotic cooperation between fungi and algae in the biological complex makes it more adaptable to environmental changes, surviving under various climatic conditions, and suitable for monitoring various ecological environments. 3) Its lifespan can be decades to hundreds of years, growing only a few millimeters per year, and the organism rarely withers, so its biological tissues can be used for long-term monitoring. 4) This symbiotic organism mainly relies on atmospheric deposition to obtain nutrients, with a very low ability to absorb substances from the soil. It has a strong ability to accumulate PAHs and SPAHs in atmospheric dry and wet deposition, and the content of organic pollutants in its body is often higher than that of other organisms. Therefore, Usnea spinulosa is suitable as a natural passive sampler for the analysis of atmospheric PAHs and SPAHs in remote areas. It plays an irreplaceable role compared to other single plants in terms of geographical distribution range, monitoring time length, and pollutant accumulation capacity.

[0035] The accuracy of *Usnea spinulosa*'s response to atmospheric PAHs and SPASH pollution depends on its ability to accumulate these pollutants. The stronger the accumulation capacity, the more sensitive the biocomplex's response to spatiotemporal variations in atmospheric PAHs and SPASH, and the more reliable the results. Currently, three types of factors influence this accumulation capacity: pollutant properties, environmental factors, and plant species. Specifically, pollutant compounds with lower water solubility, lower vapor pressure, and larger molecular weight are more easily bioaccumulated; lower environmental temperatures facilitate the condensation of volatile organic compounds and their entry into organisms; and different plant species exhibit varying abilities to accumulate atmospheric organic matter. Among these three factors, the selection of *Usnea spinulosa* biocomplex species is the most important factor affecting the sensitivity of *Usnea spinulosa*'s response to regional atmospheric PAH and SPASH deposition and the comparability of data from different regions.

[0036] Within the current context, only about a dozen Usnea biocomplexes are used for monitoring atmospheric PAHs and SPAHs. These studies are mostly concentrated in remote areas of other continents outside Asia, such as the Arctic, Antarctic, and the Andes Mountains of South America, with some applications in certain cities in Europe and America. Although different Usnea species have different geographical distributions and atmospheric organic deposition accumulation capacities, related studies have given little consideration to species identification and accumulation capacity of Usnea, making it difficult to reliably compare results from different studies and regions. This invention selects Usnea biocomplex species with wide geographical distribution and strong atmospheric PAH and SPAH accumulation capacity for large-scale field monitoring, thereby enhancing the reliability and comparability of monitoring results.

[0037] In my country, *Usnea aciculifera* is more suitable than other plants for monitoring PAHs and SPAHs in remote mountainous areas for the following reasons: 1) *Usnea aciculifera* primarily obtains nutrients and PAHs and SPAHs from atmospheric deposition. 2) This high dependence has led to the evolution of morphological characteristics that facilitate the absorption and retention of atmospheric deposition: *Usnea aciculifera* is attached to the bark by a cluster of rhizoids, forming small shrubs with numerous fine branches, growing upright or slightly drooping, which makes it easier to trap atmospheric deposition; the branches of *Usnea aciculifera* have numerous powdery buds formed by bark rupture, which have high permeability to atmospheric deposition. 3) The biochemical characteristics of *Usnea spinosa* also facilitate the absorption and accumulation of PAHs and SPASHs: *Usnea spinosa* produces a large amount of usnic acid, promoting the absorption and retention of PAHs and SPASHs. Acidic groups in *Usnea spinosa* can also promote the accumulation of PAHs and SPASHs through ion exchange, lipid components (such as terpenes) and flavonoids through hydrophobic interactions, and polar polysaccharide groups through hydrogen bonding or ion exchange. 4) *Usnea spinosa* has low metabolic activity, slow growth (<0.5 cm per year), and a long lifespan (>20 years), which can reflect the long-term accumulation of PAHs and SPASHs. 5) *Usnea spinosa* is easier to collect and is widely distributed in remote mountain forests in my country, making it suitable for large-scale monitoring of atmospheric organic matter deposition.

[0038] In summary, the plant-based in-situ monitoring method of this invention uses Usnea spinulosa as a passive sampler for atmospheric deposition. By analyzing the composition and content of PAHs and SPASHs in Usnea spinulosa, the level, source, and spatiotemporal pattern of atmospheric PAHs and SPASHs deposition can be studied.

[0039] However, the chemical composition of PAHs and SPASHs in my country's atmosphere is diverse, and their deposition is relatively large. The technical solution of this invention needs to address the following issues: 1) The PAH and SPASH content in *Usnea spinulosa* samples varies greatly, with a high proportion of particulate matter and a higher accumulation level than other plant samples. 2) *Usnea spinulosa* samples have high content and diverse composition of natural secondary metabolites, exhibiting species-specific differences. Inappropriate pretreatment and testing methods may lead to chemical reactions between natural plant organic matter and PAHs and SPASHs, resulting in distorted test results and excessive background noise. 3) Existing biomonitoring research projects for the simultaneous testing of PAHs and SPASHs in plant samples are limited, primarily focusing on PAHs.

[0040] Based on comprehensive research in analytical chemistry, biology, ecology, and environmental biogeochemistry, this invention establishes and optimizes for the first time an in-situ monitoring method using plant carriers for atmospheric PAHs and SPAHs deposition in remote mountainous areas. The method consists of two parts: plant species selection and optimization of analytical testing methods for PAHs and SPAHs in the plant Usnea spinulosa.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: The in-situ monitoring method using plant carriers of this invention screens out *Usnea spinulosa*, a plant species widely distributed in remote areas with a strong ability to accumulate atmospheric PAHs and SPASHs. Using *Usnea spinulosa* as a passive sampler for atmospheric deposition, the composition and content of PAHs and SPASHs in *Usnea spinulosa* are analyzed to study the level, source, and spatiotemporal pattern of atmospheric PAH and SPASH deposition (e.g., by analyzing the ratio of characteristic components of PAHs to SPASHs in *Usnea spinulosa*, such as fluoranthene / (fluoranthene + pyrene), indo[1,2,3-cd]pyrene / (… (e.g., indo[1,2,3-cd]pyrene + benzo[g,h,i]perylene), which can be compared with known pollution source fingerprint databases to determine possible pollution sources (e.g., fossil fuel combustion, traffic emissions, industrial processes, etc.); for example, by systematically distributing and repeatedly sampling in different functional areas (e.g., background areas, rural areas, downwind areas of cities) and different seasons (or consecutive months), the spatial gradient and temporal variation trend of pollutant concentration in Usnea sp. can be analyzed to reveal its spatial distribution characteristics and temporal dynamics, thereby clarifying its spatiotemporal pattern).

[0042] The plant-based in-situ monitoring method of this invention utilizes the geographically widespread distribution of *Usnea spinulosa*, particularly its high biomass in remote areas, overcoming the difficulty of site selection in instrumental methods. Furthermore, *Usnea spinulosa* has a strong ability to accumulate PAHs and SPASHs, and the sample collection and pretreatment procedures are simple and easy to implement, eliminating the need for PAH and SPASH elution processes and reducing the inaccuracy of the results. Therefore, the plant-based in-situ monitoring method using *Usnea spinulosa* allows for large-scale PAH and SPASH deposition monitoring studies in remote areas. It is simple, easy to implement, and inexpensive, making it an ideal alternative to atmospheric instrumental sampling methods.

[0043] The in-situ monitoring method using plant carriers of this invention enables the monitoring of atmospheric PAHs and SPAHs deposition over a larger spatial area and at a higher spatial resolution in remote regions. This provides the government with a basis for environmental governance decisions and technical support for appropriate remediation. Detection results showed that the method was used to assess the deposition of PAHs and SPAHs in the Taihang Mountains area of ​​Baoding-Shijiazhuang (8000 km²) at a spatial resolution of 15-20 km. 2 The study investigated the deposition levels of atmospheric PAHs and SPASHs. The results showed that the plant Usnea spinulosa has a strong ability to accumulate PAHs and SPASHs, verifying the strong impact of local human activities and atmospheric pollutant transport on air quality in remote mountainous areas. The study also verified the effectiveness and accuracy of the method and enhanced the comparability with the results of instrument sampling methods. Attached Figure Description

[0044] Figure 1 The image shows a photograph of the thorny Usnea used in Embodiment 1 of the present invention. The scale bar in the image is 0.3 mm.

[0045] Figure 2 The standard spectrum of polycyclic aromatic hydrocarbons and their derivatives in Example 1 of this invention is shown.

[0046] Figure 3 The results are from the actual sample measurements in Example 1 of this invention. Detailed Implementation

[0047] To further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0048] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0049] In the following examples and comparative examples, the various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following examples and comparative examples are commercially available.

[0050] Example 1 Step 1, Sample Extraction: The spiny Usnea (a complex of filamentous fibers with a fluffy physical structure and unique epidermal waxy components, such as...) Figure 1 As shown, the sample was collected from the mountain forest in Saihanba Mountain Area, Chengde City, Hebei Province (117°9'E, 42°26'N), at an altitude of 1500m. Under a stereomicroscope, visible adhering debris was removed with tweezers, and then gently washed with pure water to remove dust and other particulate matter. The sample was freeze-dried, pulverized, and passed through a 60-mesh sieve to obtain a sample of Usnea spicata powder.

[0051] Weigh 10g of Usnea sp. powder into a clean beaker, add 1 spoonful of diatomaceous earth and mix well to obtain the test sample. Take a clean 40mL extraction cell, unscrew the bottom cap, and place it vertically upside down on a horizontal platform. Place the glass fiber filter membrane at the bottom, screw on the bottom cap, invert the extraction cell, place a special funnel on top, and add two spoonfuls of diatomaceous earth. Carefully transfer the test sample to the extraction cell through the special funnel, remove the funnel, add 100μg / L of three SVOC substitutes (including nitrobenzene-d5, 2-fluorobiphenyl, and deuterated terphenyl, standard solution manufacturer: AccuStandard, see Table 1), and cover with the glass fiber filter membrane. Vertically and steadily lift the extraction cell and place it vertically and steadily into the sample tray of a pressurized fluid extraction device (BUCHI, Switzerland, model E916). Extract under the following conditions to obtain the extract: Extraction solvent: a 1:1 mixture of acetone and n-hexane (volume ratio); heating temperature: 100℃; extraction cell pressure: 100 bar; static extraction time: 5 min; nitrogen purging time: 2 min; number of static extractions: 2. Simultaneously, sample spiking was performed by adding 100 μg / L standard mixed solution (see Table 1; all standard solutions were purchased from Shanghai Anpu Experimental Technology Co., Ltd.).

[0052] After drying the extract, it was concentrated to 2 mL using a parallel concentrator to obtain the extracted sample.

[0053] Step 2, Sample purification: Purification was performed using a solid-phase extraction apparatus (Shanghai Anpu Scientific Instruments Co., Ltd.) and a silica gel column (1g, 6mL).

[0054] First, rinse the silica gel column with 10 mL of dichloromethane at a flow rate of 5 mL / min, then rinse the silica gel column with 5 mL of n-hexane at a flow rate of 5 mL / min. After the silica gel column is filled with 5 mL of n-hexane, let it soak for 5 min. Then continue to activate the silica gel column with 5 mL of n-hexane at a flow rate of 10 mL / min until the column bed is completely equilibrated by n-hexane and the liquid level drops to the top of the packing material.

[0055] Load the sample into the activated silica column at a flow rate of 1 mL / min. Use 2 mL of n-hexane to wash the container holding the extract twice at a flow rate of 10 mL / min. Load the sample again at a flow rate of 1 mL / min.

[0056] First, elute with 5 mL of a mixture of n-hexane and dichloromethane in a volume ratio of 1:9 at a flow rate of 1 mL / min. After pausing for 1 min, continue eluting with 10 mL of the same mixture at a flow rate of 1 mL / min. Collect all the eluent.

[0057] Perform air jetting at a flow rate of 10 mL / min and collect the jetting fluid.

[0058] Step 3, Sample Concentration: The gas-pumped liquid was manually concentrated to 1 mL by nitrogen blowing, and 100 μg / L of a mixed standard of 6 internal standards (see Table 1, standard solution manufacturer: Shanghai Anpu Experimental Technology Co., Ltd.) was added. After mixing, the mixture was transferred to a 2 mL sample bottle for testing.

[0059] Step four: Perform gas chromatography-triple quadrupole mass spectrometry (GC-MS) detection; Gas chromatography reference conditions: Inlet temperature: 280℃, carrier gas: high-purity helium, splitless injection; Column: Select PAH quartz capillary column, 30m 0.25mm 0.15µm; Column flow rate (constant flow mode): 1.0mL / min; Temperature program: 80℃ for 2 min; increase to 250℃ at a rate of 10℃ / min and hold for 2 min; then increase to 315℃ at a rate of 8℃ / min and hold for 5 min; increase to 340℃ at a rate of 20℃ / min and hold for 10 min. Injection volume: 1µL.

[0060] Mass spectrometry reference conditions: Electron impact ionization (EI) source, ionization energy 70 eV, collision gas is high-purity argon; Ion source temperature: 320℃; Transmission line temperature: 310℃; Select the scan mode SRM, with a solvent delay of 5 minutes.

[0061] In Example 1, the collision energies and detection ion pairs are shown in Table 1, and the standard spectra of polycyclic aromatic hydrocarbons and their derivatives are shown in Table 1. Figure 2 As shown in Table 2, the actual sample measurement results are shown in Table 3, and the actual sample measurement spectrum is shown in Table 4. Figure 3 As shown.

[0062] Table 1 Collision energy and monitoring ion pairs

[0063] Table 2. Measurement results of actual samples

[0064] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives using plant carriers based on Usnea spinosa, characterized in that, Using Usnea spinulosa as a carrier for air pollution accumulation includes the following steps: Step 1: Take Usnea spinulosa, wash it, freeze-dry it, pulverize it and sieve it to obtain Usnea spinulosa powder sample, extract it, dry it and concentrate it to obtain the extract; Step 2: Load the extract onto an activated silica gel column for elution to obtain the eluent, then use air jetting to collect the eluent. Step 3: Concentrate the gas-pumped liquid and perform gas chromatography-triple quadrupole mass spectrometry to obtain the total ion chromatogram of polycyclic aromatic hydrocarbons and their derivatives, thereby obtaining the composition and content of polycyclic aromatic hydrocarbons and their derivatives in Usnea spicata. The derivatives of the polycyclic aromatic hydrocarbons include one or more of oxidized polycyclic aromatic hydrocarbons, nitro polycyclic aromatic hydrocarbons, brominated polycyclic aromatic hydrocarbons, and chlorinated polycyclic aromatic hydrocarbons.

2. The method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, The polycyclic aromatic hydrocarbons include one or more of the following: naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, β, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indo[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, and benzo[g,h,i]perylene; The bromopolycyclic aromatic hydrocarbon is one or more selected from 2-bromofluorene, 9-bromophenanthrene, 9-bromoanthracene, 2,7-dibromofluorene, and 7-bromobenzo[a]anthracene; The chlorinated polycyclic aromatic hydrocarbon is one or more of 2-chloroanthracene, 9-chloroanthracene, and 2,7-dichlorofluorene; The nitropolycyclic aromatic hydrocarbon is one or more of 5-nitroacenaphthene, 2-nitrofluorene, 3-nitrofluoranthene, and 1-nitropyrene; The oxidized polycyclic aromatic hydrocarbon is one or more of benzo[a]anthracene-7,12-dione and 5,12-naphthoquinone.

3. The in-situ monitoring method for atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step one, one or more of the following characteristics are present: First, use tweezers to remove any visible debris from the surface of the thorny Usnea under a stereomicroscope, then wash it with pure water; The sieving process is a 60-mesh sieve. The extraction process used an extractant consisting of a 1:1 volume ratio of acetone and n-hexane. The extraction temperature was 100°C, the extraction pressure was 100 bar, the extraction time was 5 min, the extraction was repeated twice, and the nitrogen purging time was 2 min. The drying process is performed using anhydrous sodium sulfate. The concentration is to concentrate to 1-2 mL.

4. The method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step two, the activation method of the silica column is as follows: first, rinse the silica column with 10 mL of dichloromethane at a flow rate of 5 mL / min, then rinse the silica column with 5 mL of n-hexane at a flow rate of 5 mL / min. After the 5 mL of n-hexane fills the gel column, let it soak for 5 min, and continue to activate the silica column with 5 mL of n-hexane at a flow rate of 10 mL / min until the silica column bed is completely wetted by n-hexane and equilibrated. The specification of the silica column is 1 g: 6 mL.

5. The in-situ monitoring method for atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step two, the sample loading flow rate is 1 mL / min.

6. The method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step two, 2 mL of n-hexane was used to wash the container holding the extract twice at a flow rate of 10 mL / min, and the resulting washing solution was loaded onto the sample at a flow rate of 1 mL / min.

7. The method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step two, the elution process is as follows: first, elute with 5 mL of n-hexane and dichloromethane at a volume ratio of 1:9 at a flow rate of 1 mL / min, pause for 1 min, and then continue eluting with 10 mL of n-hexane and dichloromethane at a volume ratio of 1:9 at a flow rate of 1 mL / min, and collect all the eluent.

8. The method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step two, the flow rate of the air jet is 10 mL / min.

9. The method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step three, the concentration method is nitrogen purging, concentrating to 1 mL.

10. The method for in-situ monitoring of atmospheric polycyclic aromatic hydrocarbons and their derivatives based on Usnea spinulosa according to claim 1, characterized in that, In step three, the operating conditions for the gas chromatography are as follows: Inlet temperature: 280℃; Carrier gas: Helium with a purity of not less than 99.999%, splitless injection; Column: Select PAH quartz capillary column, 30m 0.25mm 0.15μm; Column flow rate: 1.0mL / min in constant flow mode; Temperature program: 80℃ for 2 min; increase to 250℃ at a rate of 10℃ / min and hold for 2 min; then increase to 315℃ at a rate of 8℃ / min and hold for 5 min; increase to 340℃ at a rate of 20℃ / min and hold for 10 min. Injection volume: 1 μL; The operating conditions of the triple quadrupole mass spectrometer are as follows: Electron bombardment ion source, ionization energy 70eV, collision gas is argon gas with a purity of not less than 99.999%; Ion source temperature: 320℃; Transmission line temperature: 310℃; Select scan mode: SRM, solvent delay 5 min.

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