A method for source apportionment of atmospheric VOCs multi-path reaction consumption

Abstract

This invention relates to a method for source apportionment of atmospheric VOCs multi-pathway reaction consumption, comprising the following steps: Step S1, data acquisition and diurnal time division; Step S2, determining the initial species ratio based on the stable nighttime period; Step S3, quantitatively estimating the initial concentration of VOCs species in the daytime and nighttime environment, as well as the chemical consumption concentration of VOCs species under three reaction pathways; Step S4, running three models—OC-PMF, IC-PMF, and ICO3-PMF—for source apportionment; Step S5, identifying the PMF model resolving factors; Step S6, source apportionment of atmospheric VOCs multi-pathway reaction consumption, obtaining the source apportionment results of VOCs reaction consumption for different pathways through the difference method based on the source contributions of OC-PMF, IC-PMF, and ICO3-PMF resolving factors. This invention achieves quantitative and accurate source apportionment of atmospheric VOCs multi-pathway reaction consumption, solving the problem of existing methods neglecting the source tracing of VOCs multi-pathway consumption at night, and providing scientific support for the precise control of atmospheric ozone and secondary organic aerosols.

Description

Technical Field

[0001] This invention relates to the field of air pollution control, and in particular to a source apportionment method for the multi-pathway reaction consumption of atmospheric VOCs, especially a source apportionment method for the multi-pathway reaction consumption of volatile organic compounds (VOCs) in the atmosphere with daytime ·OH, nighttime O3 and nighttime NO3·. Background Technology

[0002] Volatile organic compounds (VOCs) are key precursors to the formation of ozone (O3) and secondary organic aerosols (SOA) in the atmosphere. With the participation of nitrogen oxides (NOx), VOCs mainly undergo multi-pathway oxidation reactions with oxidants such as hydroxyl (·OH) radicals, ozone (O3), and nitrate (NO3·) radicals to generate secondary pollutants such as O3 and SOA, thereby exacerbating the situation of secondary atmospheric pollution. Therefore, accurately identifying the sources of VOCs consumed in the reaction that generate these secondary pollutants and quantifying their contribution is of great importance and significance for formulating effective strategies for the prevention and control of atmospheric pollution.

[0003] The chemical consumption of atmospheric VOCs mainly occurs during the daytime reaction with ·OH radicals and at night with O3 and NO3· radicals. In addition, the photolysis of oxygen-containing VOCs also causes some loss, but this is relatively small. Current research mainly focuses on the quantitative analysis and source apportionment of VOCs consumed during the daytime reaction with ·OH radicals, neglecting the oxidation process at night. Most studies use photochemical age parameters or sequential reaction models to estimate the photochemical reaction age or photochemical exposure of VOC species during the day, and calculate their initial concentrations by combining the reaction rate constant with ·OH radicals. Based on the initial concentration data and observational data, source apportionment studies of VOCs photochemical reaction consumption are conducted using positive definite matrix factorization (PMF) models. Nevertheless, at night, unsaturated VOC species such as olefins and styrene in the atmosphere can undergo rapid addition reactions with oxidants such as O3 and NO3·, and the reaction rate can even exceed the photochemical oxidation reaction with ·OH radicals during the day in some situations. Therefore, the contribution of VOCs reaction consumption at night to secondary pollutants in the atmosphere cannot be ignored. However, at present, there is still a lack of methods to analyze the sources of atmospheric VOCs consumption through multiple pathways (i.e., reactions with ·OH during the day and reactions with O3 and NO3· at night).

[0004] Therefore, it is necessary to couple multiple technical methods, such as multi-oxidant reaction kinetics, multi-pathway reaction consumption estimation, and receptor model, to propose a new method for source apportionment of atmospheric VOCs multi-pathway reaction consumption. This method can accurately quantify and apportion the sources of environmental VOCs multi-pathway reaction consumption, thereby solving the problem of tracing the source of VOCs multi-pathway consumption that is ignored by existing methods. This will provide certain technical support for the precise prevention and control of atmospheric O3 and SOA. Summary of the Invention

[0005] The purpose of this invention is to propose a source apportionment method for the multi-pathway reaction consumption of atmospheric VOCs. Its aim is to identify and quantify the sources of VOCs consumption during the day with ·OH radicals, and at night with O3 and NO3· radicals. This method overcomes the shortcomings of traditional methods that only focus on the source apportionment of VOCs consumption during the day with ·OH radicals, neglecting the source tracing of consumption during the night with O3 and NO3· radicals. This significantly improves the precision and accuracy of tracing the source of environmental VOCs consumption, providing precise and reliable technical support for the effective control of atmospheric ozone and secondary organic aerosol precursors.

[0006] To achieve the above objectives, this invention provides a source apportionment method for multi-pathway reaction consumption of atmospheric VOCs, comprising the following steps: Step S1: Data collection and diurnal time division. Conduct online monitoring of hourly concentration data of environmental VOCs species and meteorological data (including wind speed, wind direction, etc.) in the target area. Diurnal time is divided according to local sunrise and sunset times. The daytime period is mainly dominated by photochemical oxidation consumption of ·OH free radicals, while the nighttime period is mainly dominated by oxidation consumption of O3 and NO3·.

[0007] Step S2: Determine the initial species ratio based on the stable period at night. Utilize the diurnal variation of the selected species comparison values ​​to determine the stable period for estimating the initial ratio at night. Calculate three sets of initial species ratios to provide basic parameter values ​​for subsequent initial concentration estimation. Specifically, this includes: Ethylbenzene (E) and m / p-xylene (X) were selected as the first reference species pair to determine the stable time period during which the minimum E / X ratio occurred at night. The E / X ratio at different percentiles (i.e., 10) within this time period was then analyzed. th 20 th 30 th 40 th 50 th 60 th 70 th 80 th 90 th The minimum value of the mean ratio of E and X concentrations or the minimum value of the linear slope of the scatter plot of E and X concentrations (ensuring that the corresponding E and X concentrations have a high correlation, R) 2 ≥0.80) was used as the initial species ratio (E / X) t=0 Estimate the daytime exposure age or exposure to the reaction with ·OH; Benzene and cis-2-butene were selected as the second reference species pair, and their initial concentration ratio during the nighttime stable period was calculated similarly. This serves as the initial species ratio for estimating the age of nighttime O3 response exposure or the response exposure. Benzene and isoprene were selected as the third reference species pair, and their initial concentration ratios during the nighttime stable period were calculated similarly. This serves as the initial species ratio for estimating the age of exposure to NO3· at night or the initial species exposure to NO3·.

[0008] Step S3: Quantitatively estimate the initial concentrations of VOCs species in the daytime and nighttime environment, as well as the chemical consumption concentrations of VOCs species under the three reaction pathways. Based on the initial species ratios in Step S2, calculate the chemical exposure age or chemical exposure for daytime ·OH, nighttime O3, and nighttime NO3·, respectively. Combined with the reaction rate constants of VOCs species with ·OH, O3, and NO3·, estimate the initial concentrations of VOCs species during the study period, i.e., the environmental concentrations freshly emitted from the pollution source that have not undergone chemical consumption. Based on the initial concentration estimation, calculate the consumption concentrations of VOCs species under the daytime oxidation pathway with ·OH and the three oxidation reaction pathways with O3 and NO3· at night, respectively, based on the observed concentrations.

[0009] Step S31, estimation of daytime photochemical exposure to ·OH, initial concentration, and reaction consumption: For species in Photochemical Assessment Monitoring Stations (PAMS) other than isoprene (including alkanes, alkenes, aromatics, and acetylenes), halogenated hydrocarbons, and methyl tert-butyl ethers, the initial E / X ratio obtained in step S2 is used in conjunction with the photochemical reaction rate constant (K0) for different VOC species. ·OH The daytime photochemical exposure to ·OH (i.e., [·OH]Δt) is estimated to quantify the initial daytime concentration of different VOC species. The difference between the initial daytime concentration and the observed concentration is the concentration consumed by the photochemical reaction. The specific calculation formula is as follows: (1); (2); (3); In the formula: [·OH] is the concentration of ·OH, ppbv; K ·OH,E Let be the rate constant for the reaction of ethylbenzene with ·OH, in cm. 3 molecule -1 s -1 ;K ·OH,X is the rate constant for the reaction of m / p-xylene with ·OH, cm 3 molecule -1 s -1(E / X) t=0 This represents the initial ratio of ethylbenzene to m / p-xylene; (E / X) t=t The concentration ratio of ethylbenzene to m / p-xylene observed at time t; Let be the observed concentration of VOCs species i at time t, in ppbv; Let K be the initial concentration of VOCs species i at time t, in ppbv; ·OH,i Let be the reaction rate constant of VOC species i with ·OH, cm 3 molecule -1 s -1 ; Let be the VOCs species i consumed at time t, in ppbv.

[0010] For isoprene, its daytime photochemical exposure to ·OH (i.e., [·OH]Δt) isoprene The mean of the values ​​of methyl vinyl ketone (MVK) and its photochemical product, methacrolein (MACR), can be estimated using either formula (4) or formula (5) as follows: (4); (5); In the formula: The rate constant for the reaction of isoprene with ·OH is cm. 3 molecule -1 s -1 ; is the rate constant for the reaction of methacrolein with ·OH, cm 3 molecule -1 s -1 ; Let be the rate constant for the reaction of methyl vinyl ketone with ·OH, in cm. 3 molecule -1 s -1 ; Let be the observed concentration of isoprene at time t, in ppbv; Let be the observed concentration of methacrolein at time t, in ppbv; Let be the observed concentration of methyl vinyl ketone at time t, ppbv. After the photochemical exposure calculation of isoprene and ·OH, the initial concentration of isoprene and the photochemical consumption were estimated by formulas (2) and (3).

[0011] For oxygen-containing VOCs (OVOCs) species other than methyl tert-butyl ether, their daytime photochemical consumption concentration is mainly estimated based on the consumption concentration of isoprene, as shown in the following formula (6): (6); In the formula: , , respectively, are the observed concentration and consumed concentration of OVOCs species i at time t, in ppbv; Let be the concentration of isoprene consumed at time t, in ppbv; Let be the rate constant of the reaction between OVOC species i and ·OH, cm 3 molecule -1 s -1 ; Let be the observed concentration of isoprene at time t, in ppbv. The initial daytime concentration of isoprene is the sum of the observed daytime concentration and the photochemically consumed concentration.

[0012] Step S32, estimation of chemical exposure, initial concentration, and reaction consumption of NO3· and O3 at night: Based on the chemical reaction rate constants of environmental VOCs with NO3· and O3, isoprene, styrene, and 1,3-butadiene were used to calculate the chemical depletion and initial concentration of NO3· during the night; 1-hexene, ethylene, propylene, trans-2-butene, 1-butene, cis-2-butene, trans-2-pentene, 1-pentene, and cis-2-pentene were used to calculate the chemical consumption and initial concentration of O3 during the night; while the observed concentrations of other VOCs with low reaction rates were assumed to be their initial concentrations during the night, i.e., the chemical consumption concentrations were zero.

[0013] For isoprene, styrene and 1,3-butadiene, the initial ratio of benzene to isoprene in step S2 and its reaction rate constant with NO3· are used to calculate the nighttime NO3· chemical exposure (i.e. [NO3·]Δt), and then estimate the initial nighttime concentration, as shown in formulas (7) and (8); then the nighttime chemical consumption concentration is calculated using formula (3).

[0014] (7); (8); In the formula: Let be the rate constant for the reaction of benzene with NO3·, cm 3 molecule -1 s -1 ; The rate constant for the reaction of isoprene with NO3· is cm. 3 molecule -1 s -1 ; This represents the initial ratio of benzene to isoprene; The observed concentration ratio of benzene to isoprene at time t; Let be the reaction rate constant of VOC species i with NO3·, cm 3 molecule -1 s -1 .

[0015] For 1-hexene, ethylene, propylene, trans-2-butene, 1-butene, cis-2-butene, trans-2-pentene, 1-pentene and cis-2-pentene, their nighttime chemical exposure to O3 (i.e. [O3]Δt) is calculated using the initial ratio of benzene to cis-2-butene and its reaction rate constant with O3, and then their nighttime initial concentration is estimated, as shown in formulas (9) and (10); then their nighttime chemical consumption concentration is calculated using formula (3).

[0016] (9); (10); In the formula: Let be the rate constant for the reaction of benzene with O3, cm. 3 molecule -1 s -1 ; Let be the rate constant for the reaction of cis-2-butene with O3, cm 3 molecule -1 s -1 ; This represents the initial ratio of benzene to cis-2-butene; The observed concentration ratio of benzene to cis-2-butene at time t; Let be the reaction rate constant between VOC species i and O3, cm 3 molecule -1 s -1 .

[0017] Step S4: Run the OC-PMF, IC-PMF, and ICO3-PMF models to perform source analysis.

[0018] In step S41, the input species for PMF need to be screened. The screening principles mainly include dominant species, source marker species, and species with relatively low activity, while excluding species with large amounts of missing data. The uncertainty of the species concentration data is calculated according to the method in the US EPA PMF method guide. In order to quantify the contribution of each factor analysis, the total volatile organic compound (TVOC) concentration data needs to be input into PMF simultaneously with other screened species for calculation. TVOCs are set as the total variable, and their uncertainty is 4 times that of the concentration.

[0019] Step S42: The daytime and nighttime observation data are incorporated into the Positive Matrix Factorization (PMF) model for source analysis. The analysis results (factor spectrum and factor contribution) are defined as OC-PMF results.

[0020] Step S43: The initial daytime data (i.e., the concentration data consumed by the reaction with ·OH radicals) and the initial nighttime data (i.e., the concentration data consumed by the reaction with O3 and NO3· radicals) are included in the PMF for source analysis. The analysis results (factor spectrum and factor contribution) are defined as IC-PMF results.

[0021] Step S44: The initial daytime data (i.e., the concentration data corrected for the reaction with ·OH radicals) and the initial nighttime data corrected only for the reaction with O3 are included in the PMF for source analysis. The analysis results (factor spectrum and factor contribution) are defined as IC. O3 -Source analysis results of PMF.

[0022] Step S45, Reasonableness assessment of the three types of PMF analysis results: Q 计算 / Q 理论 It is close to 1.0 (0.9-1.1), the sum of squared residuals is basically between ±3.0, and DISP % dQ and DISP swaps are both 0, etc.

[0023] Step S5, Model Resolution Factor Identification: Source feature tracers, or marker species, are used to identify the three PMF model resolution factors. Simultaneously, the matching between the Conditional Bivariate Probability Function (CBPF) plot of factor contributions and the actual distribution of pollution sources around the study site is used to assist in source identification. The principle of CBPF is to introduce wind speed as a third variable, based on the traditional conditional probability function (CPF) which only considers wind direction. Data is divided into two-dimensional grid cells according to wind direction intervals (Δθ) and wind speed intervals (Δu), and the pollution source contribution value exceeding a preset threshold (e.g., the 75th) is calculated in each cell. th The ratio of the number of data points (m) at the percentile to the total number of data points (n) in that cell is given by the following formula: (11); Where: m Δθ,Δu This refers to the number of data points in a grid cell for a specific wind direction (Δθ) and wind speed (Δu) whose source contribution value exceeds a threshold; n Δθ,Δu The total number of all data points in the grid cell for a specific wind direction (Δθ) and wind speed (Δu).

[0024] Step S6: Source apportionment of VOCs consumption via multiple pathways in the atmosphere, based on OC-PMF, IC-PMF, and IC O3 - The source contribution of PMF analysis is used to obtain the source analysis results of VOCs reaction consumption through different pathways by the difference method.

[0025] Step S61, the difference in contributions of different factors analyzed by IC-PMF and OC-PMF during the day is the source analysis result of VOCs consumption by reaction with ·OH during the day (i.e., C). OH -PMF results), while the difference in contribution at night is the source apportionment result of VOCs consumed by the reaction with O3 and NO3· at night (i.e., C O3+NO3 -PMF results).

[0026] Step S62, IC-PMF and IC O3 The difference in contributions of different factors in the PMF analysis at night represents the source of VOCs consumption due to the reaction with NO3· at night (i.e., C). NO3 -PMF results).

[0027] Step S63, C O3+NO3 -PMF and C NO3 The difference in contribution from PMF analysis represents the source of VOCs consumption due to the reaction with O3 in the evening (i.e., C). O3 -PMF results).

[0028] Preferably, in step S1, the online VOCs monitoring can analyze at least 100 VOCs species, covering alkanes, alkenes, aromatic hydrocarbons, alkynes, OVOCs species, and halogenated hydrocarbons.

[0029] Preferably, in step S2, when calculating the initial species ratio, a stable time period in which the minimum E / X ratio occurs at night is selected. The minimum value of the mean E / X ratio at different percentiles within this time period, or the minimum linear slope of the scatter plot of E and X concentrations, is used (ensuring a high correlation between the corresponding E and X concentrations, R...). 2 ≥0.80) was used as the initial species ratio (E / X) t=0 Meanwhile, the initial ratio of benzene / cis-2-butene to benzene / isoprene is determined using a method similar to that described above.

[0030] Preferably, in step S4, the input species of the PMF model need to be screened. The screening principles mainly include dominant species, source marker species, and species with relatively low activity, excluding species with large amounts of missing data; the uncertainty of the species concentration data is calculated according to the method in the US EPA PMF method guide; in order to quantify the contribution of each factor analysis, the total volatile organic compounds (TVOCs) concentration data and other screened species need to be input into the PMF for calculation simultaneously. TVOCs is set as the total variable, and its uncertainty is 4 times that of the concentration.

[0031] Based on the above technical solution, the advantages of the present invention are: The source apportionment method of this invention establishes a multi-pathway, multi-oxidant coupled consumption tracing system: it breaks through the limitation of traditional methods that only focus on daytime ·OH free radical reaction consumption, and incorporates VOCs reaction consumption under three typical oxidation pathways of daytime ·OH, nighttime O3 and nighttime NO3· into a unified source apportionment framework, thus fully revealing the chemical loss process of atmospheric VOCs.

[0032] The source apportionment method of this invention develops an integrated self-consistent solution model of "initial concentration quantification - consumption concentration estimation - source contribution identification": it estimates the initial concentration of VOCs through reaction kinetics, simultaneously calculates the consumption concentration of VOCs under three reaction pathways, and combines three types of PMF models (i.e., OC-PMF, IC-PMF, IC...). O3 Using the PMF (-PMF) and difference method, we were able to quantitatively attribute the sources of VOCs consumption in each pathway.

[0033] The source apportionment method of this invention also realizes the source apportionment of VOCs consumption through multiple pathways at night: For complex systems where O3 and NO3· coexist at night, the chemical exposure to O3 and NO3· is estimated by using the initial ratios of dual reference species (benzene / cis-2-butene, benzene / isoprene), and the chemical loss and initial concentration at night are estimated by combining their reaction rate constants; combined with the nighttime contribution difference method of three types of PMF models, the source and contribution of VOCs consumption under the two reaction pathways at night are accurately quantified, solving the problem that the existing technology is difficult to distinguish the contribution of different oxidation pathways at night.

[0034] The source apportionment method of this invention is based on conventional VOCs online monitoring data (such as GC-FID / MS), meteorological data, and a reaction rate constant library. It does not rely on additional special experimental conditions and can be widely applied to source tracing studies of atmospheric VOCs multi-path reaction consumption in different regions and seasons, providing general technical support for the control of ozone and secondary organic aerosol precursors. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a flowchart of the method of the present invention; Figure 2 This describes the day-night division during the study period in this embodiment of the invention; Figure 3 This is a schematic diagram illustrating the determination of the initial E / X emission ratio based on a stable nighttime period in an embodiment of the present invention; Figure 4 The analytical factor spectra of the three types of PMF models in the embodiments of the present invention; Figure 5 This is a plot of the conditional bivariate probability function (CBPF) for different pollution sources in the OC-PMF and IC-PMF analysis results of this invention. Figure 6 To illustrate the distribution of pollution sources around the study site in this embodiment of the invention, the CBPF diagram represents the results of IC-PMF. Figure 7 In the embodiments of the present invention, OC-PMF, IC-PMF, C-PMF, and C OH -PMF, C O3 -PMF, C NO3 - The contributions and proportions of different factors in PMF source analysis. Detailed Implementation

[0036] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] This invention provides a method for source apportionment of atmospheric VOCs multi-pathway reaction consumption, such as... Figure 1 As shown, it includes the following steps: Step S1, Data Acquisition and Day / Night Period Division: Conduct online monitoring of hourly concentration data of environmental VOCs species and meteorological data in the target area, and divide the day / night period according to the local sunrise and sunset times.

[0038] Step S2: Determine the initial species ratios based on the stable period at night: Select ethylbenzene (E) and m / p-xylene (X) as the first reference species pair, select benzene and cis-2-butene as the second reference species pair, and select benzene and isoprene as the third reference species pair. Use the diurnal variation of the selected species comparison values ​​to determine the stable period for estimating the initial ratios at night, and calculate the three sets of initial species ratios.

[0039] Step S3: Quantitatively estimate the initial concentrations of VOC species in the daytime and nighttime environment, as well as the chemical consumption concentrations of VOC species under the three reaction pathways: Based on the initial species ratio, calculate the chemical exposure age or chemical exposure for daytime ·OH, nighttime O3, and nighttime NO3·, respectively. Combined with the reaction rate constants of VOC species with ·OH, O3, and NO3·, estimate the initial concentrations of VOC species during the study period, i.e., the environmental concentrations freshly emitted from the pollution source that have not undergone chemical consumption. Based on the initial concentration estimate, and combined with the observed concentrations, calculate the consumption concentrations of VOC species under the three oxidation reaction pathways of daytime with ·OH and nighttime with O3 and NO3·, respectively.

[0040] Step S4: Run source apportionment analysis for three models: OC-PMF, IC-PMF, and ICO3-PMF. Select the input species for PMF. The source apportionment results based on the positive definite matrix factorization model using daytime and nighttime observation data are defined as the OC-PMF results. The PMF source apportionment results based on initial daytime concentration data and initial nighttime data are defined as the IC-PMF results. The PMF source apportionment results based on initial daytime data and initial nighttime data only corrected for O3 reaction consumption are defined as the IC-PMF results. O3 - Source analysis results of PMF; among which, the reasonableness judgment indicators of PMF analysis results include: Q 计算 / Q 理论 The value is close to 1.0 (0.9-1.1), the sum of squared residuals is basically between ±3.0, and DISP % dQ and DISP swaps are both 0.

[0041] Step S5, Identification of PMF Model Resolution Factors: Source feature tracers are used to identify the resolution factors of the three PMF models. At the same time, the matching between the conditional bivariate probability function (CBPF) plot of factor contributions and the actual distribution of pollution sources around the study site is used to assist in source identification.

[0042] Step S6, Source analysis of VOCs consumption via multiple pathways in the atmosphere: based on OC-PMF, IC-PMF, and IC O3 The source contribution of IC-PMF analysis was used to obtain the source apportionment results of VOCs consumption through different pathways via the difference method; among them, the difference in daytime contributions of different factors between IC-PMF and OC-PMF analysis is the source apportionment result of VOCs consumption by reaction with ·OH during the daytime (C OH -PMF results), while the difference in contribution at night is the source apportionment result of VOCs consumed by the reaction with O3 and NO3· at night (C O3+NO3 -PMF results); IC-PMF and IC O3The difference in contributions of different factors in the PMF analysis at night represents the source of VOCs consumption due to the reaction with NO3· at night (C). NO3 -PMF results), C O3+NO3 -PMF results and C NO3 The difference between the -PMF results represents the source analysis results of VOCs consumption due to reaction with O3 in the evening (C O3 -PMF results).

[0043] This invention identifies and quantifies the sources of VOCs consumption through three typical oxidation pathways: daytime reaction with ·OH, and nighttime reaction with O3 and NO3·. It overcomes the shortcomings of existing methods that only focus on the source analysis of VOCs consumption through daytime reaction with ·OH free radicals, neglecting the source tracing of VOCs consumption through nighttime reaction with O3 and NO3·. This invention significantly improves the precision and accuracy of tracing the source of VOCs consumption in the environment, providing precise and reliable technical support for the effective control of atmospheric ozone and secondary organic aerosol precursors.

[0044] To further illustrate the technical solution of the present invention and its detailed implementation process, this embodiment takes the application in Linfen, Shanxi, a typical industrial city in northern China, as an example, selecting online monitoring data from April 1 to October 31, 2023. The specific implementation process is as follows: (1) Data collection and day / night time division; Environmental VOCs online monitoring was conducted in Linfen City from April 1 to October 31, 2023. Hourly concentration data (in ppbv) of 115 VOCs were acquired using an online gas chromatography-flame ionization detector / mass spectrometer (GC-FID / MS) (EXPEC2000-MS, Hangzhou Puyu Technology Development Co., Ltd., China). Meteorological data (wind speed and direction, etc.) were monitored simultaneously using a miniature weather station (WS-6P, Shenzhen Zhixiangyu Instrument Co., Ltd., China).

[0045] Based on the sunrise and sunset times in Linfen during the study period, the daytime and nighttime periods of different months were divided, as follows: Figure 2 As shown.

[0046] (2) Estimate the initial species ratio based on the stable nighttime period; Based on the diurnal variations of three reference ratios—ethylbenzene / m,p-xylene (E / X), benzene / cis-2-butene, and benzene / isoprene—during the study period, and combined with the sunrise and sunset times for different months in Linfen City during the study period, relevant data from the evening period of 22:00 to 05:00 were selected to calculate the initial species ratios.

[0047] First reference species ratio (E / X): Calculate all E / X ratios during the period from 22:00 to 05:00 during the Linfen study period, arrange the ratios from smallest to largest, and calculate the different percentiles (i.e., 10) of the ratios. th 20 th 30 th 40 th 50 th 60 th 70 th 80 th 90 th The linear slope of the scatter plots for E and X concentrations corresponding to all ratios below the 10th percentile is 0.23, and the correlation between E and X concentration is high (R0). 2 =0.95, see Figure 3 The initial E / X ratio (E / X) has the lowest linear slope compared to other percentiles. t=0 It is 0.23.

[0048] Second reference species ratio (benzene / cis-2-butene): Calculate all ratios within the period from 22:00 to 05:00 during the Linfen study period, arrange the ratios from smallest to largest, and calculate the different percentiles (i.e., 10) of the ratios. th 20 th 30 th 40 th 50 th 60 th 70 th 80 th 90 th The linear slope of the scatter plots for benzene and cis-2-butene concentrations for all ratios below the 10th percentile was 5.45, and the concentrations of the two showed a high correlation (R0). 2 =0.85), which is the lowest linear slope value compared to other percentiles for benzene and cis-2-butene concentrations, therefore the initial benzene / cis-2-butene ratio is 0.85. It is 5.45.

[0049] The third reference species ratio (benzene / isoprene): Calculate all ratios during the period from 22:00 to 05:00 during the Linfen study period, arrange the ratios from smallest to largest, and calculate the different percentiles (i.e., 10) of the ratios. th 20 th 30 th 40 th 50 th 60 th 70 th 80th 90 th The mean of all ratios below the 30th percentile was relatively low at 5.32, and the concentration correlation between the two was high (R0). 2 =0.85), therefore the initial ratio of benzene / isoprene is It is 5.32.

[0050] (3) Quantitatively estimate the initial concentration of VOC species in the daytime and nighttime environment and the consumption concentration of VOC species under the three reaction pathways; 1) Daytime photochemical exposure to ·OH, initial concentration, and reaction consumption estimation; For species in Photochemical Assessment Monitoring Stations (PAMS) other than isoprene (including alkanes, alkenes, aromatics, and acetylenes), halogenated hydrocarbons, and methyl tert-butyl ethers, the initial E / X ratio obtained in step S2 is used in conjunction with the photochemical reaction rate constant (k) for different VOC species. ·OH The daytime photochemical exposure to ·OH (i.e., [·OH]Δt) is estimated to quantify the initial daytime concentration of different VOC species. The difference between the initial daytime concentration and the observed concentration is the concentration consumed by the photochemical reaction. The specific calculation formula is as follows: (1); (2); (3); In the formula: [·OH] is the concentration of ·OH, ppbv; K ·OH,E Let be the rate constant for the reaction of ethylbenzene with ·OH, in cm. 3 molecule -1 s -1 ;K ·OH,X is the rate constant for the reaction of m / p-xylene with ·OH, cm 3 molecule -1 s -1 (E / X) t=0 The initial ratio of ethylbenzene to m / p-xylene is 0.23; (E / X) t=t The concentration ratio of ethylbenzene to m / p-xylene observed at time t; Let be the observed concentration of VOCs species i at time t, in ppbv; Let K be the initial concentration of VOCs species i at time t, in ppbv; ·OH,i Let be the reaction rate constant of VOC species i with ·OH, cm 3 molecule -1s -1 ; Let be the VOCs species i consumed at time t, in ppbv.

[0051] For isoprene, its daytime photochemical exposure to ·OH (i.e., [·OH]Δt) isoprene The mean of the values ​​of methyl vinyl ketone (MVK) and its photochemical product, methacrolein (MACR), can be estimated using either formula (4) or formula (5) as follows: (4); (5); In the formula: The rate constant for the reaction of isoprene with ·OH is cm. 3 molecule -1 s -1 ; is the rate constant for the reaction of methacrolein with ·OH, cm 3 molecule -1 s -1 ; Let be the rate constant for the reaction of methyl vinyl ketone with ·OH, in cm. 3 molecule -1 s -1 ; Let be the observed concentration of isoprene at time t, in ppbv; Let be the observed concentration of methacrolein at time t, in ppbv; Let be the observed concentration of methyl vinyl ketone at time t, ppbv. After the photochemical exposure calculation of isoprene and ·OH, the initial concentration of isoprene and the photochemical consumption were estimated by formulas (2) and (3).

[0052] For oxygen-containing VOCs (OVOCs) species other than methyl tert-butyl ether, their daytime photochemical consumption concentration is mainly estimated based on the consumption concentration of isoprene, as shown in the following formula (6): (6); In the formula: , , respectively, are the observed concentration and consumed concentration of OVOCs species i at time t, in ppbv; Let be the concentration of isoprene consumed at time t, in ppbv; Let be the rate constant of the reaction between OVOC species i and ·OH, cm 3 molecule -1 s -1 ; Let be the observed concentration of isoprene at time t, in ppbv. The initial daytime concentration of isoprene is the sum of the observed daytime concentration and the photochemically consumed concentration.

[0053] 2) Estimation of chemical exposure, initial concentration, and reaction consumption of NO3· and O3 at night; Based on the chemical reaction rate constants of environmental VOCs with NO3· and O3, isoprene, styrene, and 1,3-butadiene were used to calculate the chemical depletion and initial concentration of NO3· during the night; 1-hexene, ethylene, propylene, trans-2-butene, 1-butene, cis-2-butene, trans-2-pentene, 1-pentene, and cis-2-pentene were used to calculate the chemical consumption and initial concentration of O3 during the night; while the observed concentrations of other VOCs with low reaction rates were assumed to be their initial concentrations during the night, i.e., the chemical consumption concentrations were zero.

[0054] For isoprene, styrene and 1,3-butadiene, the initial ratio of benzene to isoprene in step S2 and its reaction rate constant with NO3· are used to calculate the nighttime NO3· chemical exposure (i.e. [NO3·]Δt), and then estimate the initial nighttime concentration, as shown in formulas (7) and (8); then the nighttime chemical consumption concentration is calculated using formula (3).

[0055] (7); (8); In the formula: Let be the rate constant for the reaction of benzene with NO3·, cm 3 molecule -1 s -1 ; The rate constant for the reaction of isoprene with NO3· is cm. 3 molecule -1 s -1 ; The initial ratio of benzene to isoprene is 5.32; The observed concentration ratio of benzene to isoprene at time t; Let be the reaction rate constant of VOC species i with NO3·, cm 3 molecule -1 s -1 .

[0056] For 1-hexene, ethylene, propylene, trans-2-butene, 1-butene, cis-2-butene, trans-2-pentene, 1-pentene and cis-2-pentene, their nighttime chemical exposure to O3 (i.e. [O3]Δt) is calculated using the initial ratio of benzene to cis-2-butene and its reaction rate constant with O3, and then their nighttime initial concentration is estimated, as shown in formulas (9) and (10); then their nighttime chemical consumption concentration is calculated using formula (3).

[0057] (9); (10); In the formula: Let be the rate constant for the reaction of benzene with O3, cm. 3 molecule -1 s -1 ; Let be the rate constant for the reaction of cis-2-butene with O3, cm 3 molecule -1 s -1 ; The initial ratio of benzene to cis-2-butene is 5.45; The observed concentration ratio of benzene to cis-2-butene at time t; Let be the reaction rate constant between VOC species i and O3, cm 3 molecule -1 s -1 .

[0058] The reaction rate constants of VOCs species with ·OH radicals, O3 and NO3· radicals in this embodiment are shown in the table below:

[0059]

[0060]

[0061] The calculation results show that the average initial concentration of total VOCs during the study period was 35.6 ppbv, the average consumption concentration was 10.7 ppbv, and the loss accounted for approximately 30.1%. Among them, daytime ·OH consumption was dominant (16.6 ppbv), while nighttime O3 consumption (1.20 ppbv) and NO3· consumption (0.77 ppbv), although the absolute values ​​were relatively low, had extremely high (>90%) loss ratios for specific olefins (such as trans-2-butene and styrene), which could not be ignored.

[0062] (4) Run the OC-PMF, IC-PMF, and ICO3-PMF models to perform source analysis; The input species for the PMF model need to be screened. The screening criteria mainly include dominant species, source marker species, and species with relatively low activity, while excluding species with large amounts of missing data. A total of 33 VOC species were selected. The uncertainty of the species concentration data was calculated according to the method in the US EPA PMF method guide. In order to quantify the contribution of each factor, the total volatile organic compounds (TVOCs) concentration data and the other 33 screened species need to be input into the PMF for calculation simultaneously. TVOCs are set as the total variable, and its uncertainty is 4 times that of the concentration.

[0063] Daytime and nighttime observation data were incorporated into a Positive Matrix Factorization (PMF) model for source analysis, and the analysis results (factor spectrum and factor contribution) were defined as OC-PMF results. The initial daytime data (i.e., the concentration data corrected for the reaction with ·OH radicals) and the initial nighttime data (i.e., the concentration data corrected for the reaction with O3 and NO3· radicals) were included in the PMF for source analysis, and the analysis results (factor spectrum and factor contribution) were defined as IC-PMF results. The initial daytime data (i.e., concentration data corrected for consumption in the reaction with ·OH radicals) and the initial nighttime data corrected only for consumption in the reaction with O3 were included in the PMF for source apportionment. The apportionment results (factor spectra and factor contributions) were defined as IC. O3 -Source analysis results of PMF.

[0064] The results showed that all three types of PMF models resolved eight factors during the study period, among which... Q 计算 / Q 理论 All are close to 1.0, and the sum of squared residuals is generally between ±3.0. (DISP % d) Q Both DISP swaps and 0 indicate that the parsing result is reasonable.

[0065] (5) Identification of analytical factors in the PMF model; Source-identifying species were used to identify the resolving factors of three PMF models. Simultaneously, the matching between the Conditional Bivariate Probability Function (CBPF) plot of factor contributions and the actual distribution of pollution sources around the study site was used to assist in source identification. The principle of CBPF is to introduce wind speed as a third variable, based on the traditional conditional probability function (CPF) which only considers wind direction. This is achieved by dividing the data into two-dimensional grid cells according to wind direction intervals (Δθ) and wind speed intervals (Δu), and calculating the pollution source contribution value exceeding a preset threshold (e.g., the 75th) in each cell. th The ratio of the number of data points (m) at the percentile to the total number of data points (n) in that cell is given by the following formula: (11); Where: m Δθ,Δu This refers to the number of data points in a grid cell for a specific wind direction (Δθ) and wind speed (Δu) whose source contribution value exceeds a threshold; n Δθ,Δu The total number of all data points in the grid cell for a specific wind direction (Δθ) and wind speed (Δu).

[0066] Factor spectra of three types of PMF analysis during the study period in Linfen City are as follows: Figure 4 As shown, the first factor has high levels of octane, nonane, and decane, as well as high explanatory variables and a narrow DISP, indicating they are tracer species for diesel vehicle emissions. Furthermore, toluene and m / p-xylene are also present in high levels within this factor's spectrum; these species can also be emitted by motor vehicles. Therefore, this factor is identified as a diesel vehicle emission source (DVE). The CBPF plot based on IC-PMF estimates of this factor's contribution shows, as... Figure 5 and Figure 6 As shown, the probability value of CBPF is higher in the southwest direction of the study site, and there are many roads and traffic arteries in this direction.

[0067] In the second factor, ethane, propane, isobutane, and n-butane have high content and explanatory variables, and relatively narrow DISPs. Ethane and propane are mainly derived from natural gas, while n-butane and isobutane are tracer species for liquefied petroleum gas. Meanwhile, the CBPF plot showing the contribution of this factor is shown (see...). Figure 5 The probability value for the study site being due north is relatively high, which is related to the cooking practices of local residents and restaurants (see [reference]). Figure 6 Residential buildings in the area use natural gas for cooking, while small restaurants mostly use liquefied petroleum gas (LPG). Therefore, this factor was identified as a mixed source of natural gas and LPG (NG / LPG).

[0068] Among the third factor, 1,3-butadiene and 1-butene had the highest explanatory variables and contents, and relatively narrow DISPs, primarily originating from industrial production processes. Furthermore, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene, and 1,2,3-trimethylbenzene also had high contents and explanatory values ​​in this factor; these aromatic hydrocarbon species mainly originate from coking processes. Therefore, this factor was identified as an industrial emission source (IE). The CBPF plot of this factor's contribution shows a higher probability value in the southwest direction of the studied sites (see [link to CBPF plot]). Figure 5 This is related to the presence of numerous coking plants and industrial parks in this direction (see [link]). Figure 6 ).

[0069] Among the fourth factors, ethylene and propylene have the highest explanatory variables and contents, and a relatively narrow DISP (Distribution-Induced Spindle Size). They are the main raw materials for the petrochemical industry and two major products of refineries. The CBPF (Contribution-to-Contribution-Performance) plot for this factor shows that the probability values ​​are higher for the study sites located due south and southwest (see [link to CBPF plot]). Figure 5 These directions are home to many companies related to petrochemical and polymer production (see...). Figure 6 Therefore, this factor was identified as the petrochemical industry (PI).

[0070] In the fifth factor, n-pentane and isopentane have high explanatory variables and contents, and relatively narrow DISPs; they are marker species for gasoline volatiles. Furthermore, methyl tert-butyl ether (MTBE) also has high contents and explanatory variables in this factor; it is a known gasoline additive used to improve octane number and combustion efficiency. Therefore, this factor is identified as a gasoline vehicle emission source (GVE). The CBPF plot of this factor's contribution shows a higher probability value in the due north direction at the study site (see [link to CBPF plot]). Figure 5 Several roads are located in this direction (see...) Figure 6 ).

[0071] Acetylene has a high explanatory variable and content in the sixth factor, and a narrow DISP. Acetylene mainly originates from combustion emissions. Furthermore, chloromethane has a high explanatory variable in this factor's spectrum and is a typical tracer of biomass combustion. The CBPF plot of this factor's contribution shows a higher probability value in the northwest direction of the study site (see...). Figure 5 This direction is home to coal-fired power plants and rural cooking methods that use straw for fuel (see...). Figure 6 Therefore, this factor was identified as a combustion emission source (CE).

[0072] Of the seventh factors, isoprene had the highest explanatory variable and content, and a relatively narrow DISP. Isoprene is primarily emitted from plant sources; therefore, this factor was identified as a biogenic emission source (BE). The CBPF plot of this factor's contribution shows a higher probability value in the southeast direction of the study sites (see [link to CBPF plot]). Figure 5This is closely related to the presence of large ecological scenic areas and vegetation in this direction (see...). Figure 6 ).

[0073] Benzene had the highest explanatory variable and content among the eighth factors, and a relatively narrow DISP. Toluene, ethylbenzene, o-xylene, and m / p-xylene also had high contents in this factor. These aromatic hydrocarbon species mainly originate from the use of paints, varnishes, synthetic fragrances, adhesives, and cleaning agents. The CBPF plot of this factor's contribution shows a higher probability value in the southwest direction of the study sites (see [link]). Figure 5 This direction is home to some machinery manufacturing plants, food processing enterprises, printing plants, pharmaceutical plants, and painting processes related to automobile manufacturing (see...). Figure 6 Therefore, this factor was identified as a solvent usage source (SU).

[0074] (6) Analysis of the sources of VOCs consumption through multiple pathways in the atmosphere; Based on OC-PMF, IC-PMF, IC O3 - The source contribution of PMF analysis, obtained by interpolation method, yields the source apportionment results of VOCs reaction consumption along different pathways, see [link to PMF analysis]. Figure 7 As shown, DVE represents diesel vehicle emission sources, NG / LPG represents mixed sources of natural gas and liquefied petroleum gas, IE represents industrial emission sources, PI represents the petrochemical industry, GVE represents gasoline vehicle emission sources, CE represents combustion emission sources, BE represents biological emission sources, and SU represents solvent use sources.

[0075] The difference in contributions of different factors analyzed by IC-PMF and OC-PMF during the day represents the source of VOCs consumption during the daytime reaction with ·OH (i.e., C). OH -PMF results), while the difference in contribution at night is the source apportionment result of VOCs consumed by the reaction with O3 and NO3· at night (i.e., C O3+NO3 -PMF results).

[0076] IC-PMF and IC O3 The difference in contributions of different factors in the PMF analysis at night represents the source of VOCs consumption due to the reaction with NO3· at night (i.e., C). NO3 -PMF results).

[0077] C O3+NO3 -PMF and C NO3 The difference in contribution from PMF analysis represents the source of VOCs consumption due to the reaction with O3 in the evening (i.e., C). O3 -PMF results).

[0078] According to the source analysis results of this study on the consumption of atmospheric VOCs in Linfen City (see...), Figure 7Industrial emissions are the largest contributor, accounting for 31.4% of total VOCs consumption. This consumption is almost entirely due to daytime ·OH reactions (5.28 ppbv), with the main consumed species being trans-2-butene, propylene, 1-butene, and 1,3,5-trimethylbenzene. Its daytime ·OH consumption is higher than other sources. The mixed source of natural gas and liquefied petroleum gas contributes 15.6%, with daytime ·OH consumption at 1.05 ppbv and nighttime consumption (O3 and NO3·) reaching 1.76 ppbv, exhibiting a higher nighttime consumption characteristic. Biological emissions contribute 10.8%, with daytime ·OH consumption at 1.04 ppbv and nighttime NO3· consumption reaching 0.79 ppbv, significantly higher than nighttime O3· consumption (0.08 ppbv), indicating that isoprene is mainly oxidized by NO3· at night. The contributions of diesel vehicle emissions, petrochemical industry emissions, solvent use emissions, combustion emissions, and gasoline vehicle emissions were 12.3%, 8.89%, 8.44%, 6.64%, and 5.96%, respectively. Among these, daytime ·OH reactions dominated the consumption of diesel vehicle emissions, petrochemical industry emissions, and solvent use emissions. Gasoline vehicle emissions showed comparable daytime consumption (0.56 ppbv) to nighttime consumption (0.51 ppbv), while combustion emissions showed higher nighttime consumption (0.85 ppbv) than their daytime ·OH consumption (0.36 ppbv). Overall, the VOCs consumption contributions from different emission sources varied significantly under different reaction pathways, reflecting the combined effects of source chemical composition, emission time, and atmospheric oxidant effectiveness.

[0079] This embodiment fully verifies the effectiveness and advancement of the method of the present invention in quantifying the contribution of different emission sources to the multi-path reaction consumption of atmospheric VOCs, and can provide refined scientific support for the prevention and control of atmospheric ozone pollution.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for source apportionment of atmospheric VOCs multi-pathway reaction consumption, characterized in that: Includes the following steps: Step S1, Data Collection and Day / Night Period Division: Conduct online monitoring of hourly concentration data of environmental VOCs species and meteorological data in the target area, and divide the day / night period according to the local sunrise and sunset times; Step S2, determine the initial species ratio based on the stable period at night: select ethylbenzene (E) and m / p-xylene (X) as the first reference species pair, select benzene and cis-2-butene as the second reference species pair, select benzene and isoprene as the third reference species pair, use the diurnal variation of the selected species comparison values ​​to determine the stable period for estimating the initial ratio at night, and calculate the three sets of initial species ratios; Step S3: Quantitatively estimate the initial concentration of VOC species in the daytime and nighttime environment and the chemical consumption concentration of VOC species under the three reaction pathways: Based on the initial species ratio, calculate the chemical exposure age or chemical exposure of daytime ·OH, nighttime O3 and nighttime NO3· respectively, and estimate the initial concentration of VOC species during the daytime and nighttime during the study period by combining the reaction rate constants of VOC species with ·OH, O3 and NO3·. Step S4: Run three models—OC-PMF, IC-PMF, and ICO3-PMF—for source apportionment. Select the input species for PMF. The source apportionment results based on the positive definite matrix factorization model using daytime and nighttime observation data are defined as the OC-PMF results. The PMF source apportionment results based on initial daytime concentration data and initial nighttime data are defined as the IC-PMF results. The PMF source apportionment results based on initial daytime data and initial nighttime data only corrected for O3 reaction consumption are defined as the IC-PMF results. O3 - Source analysis results of PMF; among which, the reasonableness judgment indicators of PMF analysis results include: Q 计算 / Q 理论 Between 0.9 and 1.1, the sum of squared residuals is between ±3.0, and both DISP % dQ and DISP swaps are 0; Step S5, Identification of PMF Model Resolution Factors: Source feature tracers are used to identify the resolution factors of the three PMF models. At the same time, the matching between the conditional bivariate probability function (CBPF) plot of factor contribution and the actual distribution of pollution sources around the study site is used to assist in source identification. Step S6, source apportionment of VOCs multi-path reaction consumption in the atmosphere: based on OC-PMF, IC-PMF, IC O3 -PMF source contribution, the source apportionment results of VOCs reaction consumption in different paths are obtained by difference method; wherein, the contribution difference of different factors in the daytime apportioned by IC-PMF and OC-PMF is the source apportionment result of VOCs consumption with ·OH reaction in the daytime (C OH -PMF result), and the contribution difference in the evening is the source apportionment result of VOCs consumption with O3 and NO3· reaction in the evening (C O3+NO3 -PMF result); the contribution difference of different factors in the evening apportioned by IC-PMF and IC O3 -PMF is the source apportionment result of VOCs consumption with NO3· reaction in the evening (C NO3 -PMF result), and the difference between C O3+NO3 -PMF result and C NO3 -PMF result is the source apportionment result of VOCs consumption with O3 reaction in the evening (C O3 -PMF result).

2. The source analysis method according to claim 1, characterized in that: Step S2, which involves calculating the ratios of the three initial species, includes: Ethylbenzene (E) and m / p-xylene (X) are selected as the first reference species pair to determine the stable time period in which the minimum value of E / X ratio appears. The minimum value of the average ratio of E / X ratio at different percentiles in this time period or the minimum value of the linear slope of the E and X concentration scatter plot (ensuring that the corresponding E and X concentrations have a high correlation, R 2 ≥ 0.80) is used as the initial species ratio (E / X) t=0 , to estimate the daytime exposure age or exposure to ·OH reaction; Benzene and cis-2-butene were selected as the second reference species pair, and their initial concentration ratio during the nighttime stable period was calculated similarly. This serves as the initial species ratio for estimating the age of nighttime O3 response exposure or the response exposure. Benzene and isoprene were selected as the third reference species pair, and their initial concentration ratios during the nighttime stable period were calculated similarly. This serves as the initial species ratio for estimating the age of exposure to NO3· at night or the initial species exposure to NO3·.

3. The source analysis method according to claim 2, characterized in that: The different percentiles include 10 th , 20 th , 30 th , 40 th , 50 th , 60 th , 70 th , 80 th , and 90 th ; the R 2 2 of the E and X concentration scatter plot is > 0.80 when calculating the linear slope value of the E and X concentration scatter plot.

4. The source analysis method according to claim 1, characterized in that: In step S3, the steps for calculating the chemical exposure, initial concentration, and chemical consumption concentration during the daytime reaction pathway with ·OH include: For photochemical assessment and monitoring station species other than isoprene, halogenated hydrocarbons, and methyl tert-butyl ether, the initial E / X ratio obtained in step S2 and the photochemical reaction rate constant K for different VOC species were used. ·OH The daytime photochemical exposure [·OH]Δt was estimated to quantify the initial daytime concentration of different VOC species. The difference between the initial daytime concentration and the observed concentration is the concentration consumed by the photochemical reaction. Specifically, the following formulas (1), (2), and (3) are used for calculation: （1）； （2）； （3）； In the formula: [·OH] is the concentration of ·OH, ppbv; K ·OH,E Let be the rate constant for the reaction of ethylbenzene with ·OH, in cm. 3 molecule - 1 s -1 ;K ·OH,X is the rate constant for the reaction of m / p-xylene with ·OH, cm 3 molecule -1 s -1 (E / X) t=0 This represents the initial ratio of ethylbenzene to m / p-xylene; (E / X) t=t The concentration ratio of ethylbenzene to m / p-xylene observed at time t; Let be the observed concentration of VOCs species i at time t, in ppbv; Let K be the initial concentration of VOCs species i at time t, in ppbv; ·OH,i Let be the reaction rate constant of VOC species i with ·OH, cm 3 molecule -1 s -1 ; Let be the VOCs species i consumed at time t, in ppbv; For isoprene, its daytime photochemical exposure to ·OH [·OH]Δt isoprene The mean of the values ​​calculated using either the photochemical product methacrolein (MACR) or methyl vinyl ketone (MVK) can be estimated using either formula (4) or formula (5) as follows: （4）； （5）； In the formula: The rate constant for the reaction of isoprene with ·OH is cm. 3 molecule -1 s -1 ; is the rate constant for the reaction of methacrolein with ·OH, cm 3 molecule -1 s -1 ; Let be the rate constant for the reaction of methyl vinyl ketone with ·OH, in cm. 3 molecule -1 s -1 ; Let be the observed concentration of isoprene at time t, in ppbv; Let be the observed concentration of methacrolein at time t, in ppbv; Let be the observed concentration of methyl vinyl ketone at time t, in ppbv; After the photochemical exposure calculation of isoprene and ·OH, the initial concentration of isoprene and the photochemical consumption were estimated by formulas (2) and (3); For oxygen-containing VOCs (OVOCs) species other than methyl tert-butyl ether, their daytime photochemical depletion concentration is estimated based on the isoprene depletion concentration, specifically calculated using the following formula (6): （6）； In the formula: , , respectively, are the observed concentration and consumed concentration of OVOCs species i at time t, in ppbv; Let be the concentration of isoprene consumed at time t, in ppbv; Let be the rate constant of the reaction between OVOC species i and ·OH, cm 3 molecule -1 s -1 ; Let be the observed concentration of isoprene at time t, in ppbv; The initial daytime concentration of isoprene is the sum of the daytime observed concentration and the photochemically consumed concentration.

5. The source analysis method according to claim 4, characterized in that: In step S3, the steps of calculating the chemical exposure, initial concentration, and chemical consumption concentration under the reaction pathways of O3 and NO3· at night include: Based on the chemical reaction rate constants of environmental VOCs with NO3· and O3, isoprene, styrene, and 1,3-butadiene were used to calculate the chemical depletion and initial concentration of NO3· during the night; 1-hexene, ethylene, propylene, trans-2-butene, 1-butene, cis-2-butene, trans-2-pentene, 1-pentene, and cis-2-pentene were used to calculate the chemical consumption and initial concentration of O3 during the night; while the observed concentrations of other VOCs with low reaction rates were assumed to be their initial concentrations during the night, i.e., the chemical consumption concentration was zero. For isoprene, styrene and 1,3-butadiene, the initial ratio of benzene to isoprene in step S2 and its reaction rate constant with NO3· are used to calculate the nighttime NO3· chemical exposure [NO3·]Δt, and then the initial nighttime concentration is estimated using formulas (7) and (8), and then the nighttime chemical consumption concentration is calculated using formula (3). （7）； （8）； In the formula: Let be the rate constant for the reaction of benzene with NO3·, cm 3 molecule -1 s -1 ; The rate constant for the reaction of isoprene with NO3· is cm. 3 molecule -1 s -1 ; This represents the initial ratio of benzene to isoprene; The observed concentration ratio of benzene to isoprene at time t; Let be the reaction rate constant of VOC species i with NO3·, cm 3 molecule -1 s -1 ; For 1-hexene, ethylene, propylene, trans-2-butene, 1-butene, cis-2-butene, trans-2-pentene, 1-pentene and cis-2-pentene, the chemical exposure [O3]Δt of 1-hexene and cis-2-butene with O3 at night is calculated using the initial ratio of benzene to cis-2-butene and its reaction rate constant with O3. Then, the initial concentration at night is estimated using formulas (9) and (10), and the chemical consumption concentration at night is calculated using formula (3). （9）； （10）； In the formula: Let be the rate constant for the reaction of benzene with O3, cm. 3 molecule -1 s -1 ; Let be the rate constant for the reaction of cis-2-butene with O3, cm 3 molecule -1 s -1 ; This represents the initial ratio of benzene to cis-2-butene; The observed concentration ratio of benzene to cis-2-butene at time t; Let be the reaction rate constant between VOC species i and O3, cm 3 molecule -1 s -1 .

6. The source analysis method according to claim 1, characterized in that: In step S4, the input species of PMF are screened to exclude species with large amounts of missing data; the uncertainty of the species concentration data is calculated; the contribution of each factor is analyzed quantitatively, and the total volatile organic compound (TVOC) concentration data and other screened species are simultaneously input into PMF for calculation. The screening criteria include dominant species, source marker species, and species with relatively low activity. When quantifying the contribution of each factor, TVOCs were set as the total variable, with an uncertainty of 4 times that of concentration.

7. The source analysis method according to claim 1, characterized in that: In step S5, the steps of CBPF include: Based on the conditional probability function considering only wind direction, wind speed is introduced as a third variable. The data is divided into two-dimensional grid cells according to the wind direction interval (Δθ) and the wind speed interval (Δu). In each cell, the ratio of the number of data points m whose pollution source contribution value exceeds the preset threshold to the total number of data points n in that cell is calculated using formula (11): （11）； Where: m Δθ,Δu This refers to the number of data points in a grid cell for a specific wind direction (Δθ) and wind speed (Δu) whose source contribution value exceeds a threshold; n Δθ,Δu The total number of all data points in the grid cell for a specific wind direction (Δθ) and wind speed (Δu).

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