VOCs source traceability evaluation method in the ambient air around enterprises

Abstract

The present invention discloses a method for tracing the source of VOCs in the ambient air surrounding an enterprise, comprising: setting monitoring points according to a distribution principle, including at least enterprise emission monitoring points and enterprise environmental monitoring points, obtaining VOC concentration data at multiple monitoring points in a target area; determining characteristic VOC components through a quantity evaluation method, an occurrence number evaluation method, a multiple evaluation method, and a maximum concentration evaluation method; calculating a traceability correlation coefficient R value based on the degree of overlap between the target enterprise's emission characteristic VOC component set and the enterprise's ambient air characteristic VOC component set; and obtaining a traceability evaluation result based on the R value. The present invention provides a simple and efficient comprehensive technical solution, achieving a breakthrough improvement in VOC pollution source tracing technology around enterprises, and solving the problem of accurately tracing the source of VOCs pollution in the ambient air around enterprises.

Description

Technical Field

[0001] The present invention relates to the field of environmental monitoring technology, and in particular to a method for tracing and evaluating VOCs in the ambient air around an enterprise. Background Art

[0002] Volatile organic compounds (VOCs) are a general term for a class of compounds with complex compositions, including alkanes, unsaturated hydrocarbons, benzene series, alcohols, aldehydes, ketones, esters, halogenated hydrocarbons, etc. Among the 187 pollutants prioritized by the U.S. EPA, 33 are volatile organic compounds. Many VOCs have significant impacts on the environment or human health. At the same time, VOCs are also important precursors to the formation of atmospheric ozone and fine particles. Most VOCs are highly photochemically reactive. Under sunlight and ultraviolet radiation, these VOCs react with other chemical components in the atmosphere, such as NO, to form high concentrations of ozone and other peroxides such as PANs.

[0003] The "Ambient Air Quality Standard" (GB3095-2012) primarily controls sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, and particulate matter (PM10 and PM2.5), but lacks any control or evaluation indicators for volatile organic compounds (VOCs). The "Standard for the Control of Unorganized Emissions of Volatile Organic Compounds" (GB 37822-2019) primarily controls total volatile organic compounds (TVOCs) and non-methane hydrocarbons (NMHCs). TVOCs and NMHCs are comprehensive evaluation indicators of VOCs, reflecting only the overall level of VOC pollution in the air. They do not identify the specific VOC components, making it impossible to accurately trace the source of the pollutants. VOCs emitted during the production processes of some enterprises pose a potential threat to the surrounding air quality.

[0004] Currently, the benzene to toluene (B / T) ratio is commonly used in academia to estimate VOC emission sources. A B / T value of 0.5 indicates that VOCs are primarily emitted from traffic sources. If B / T is less than 0.5, it indicates that in addition to traffic sources, organic solvents such as paints are also volatilized. If B / T is greater than 0.5, it indicates that emissions are primarily from the petrochemical industry and fossil fuel combustion. The ratios of m-xylene / benzene (X / B), p-xylene / benzene (T / B), and ethylbenzene / benzene (E / B) are also used to estimate the aging characteristics of air masses in different regions. When the 12-hour average volume fraction of OH radicals is 0.06×10 -12 In the atmospheric environment, their existence periods in the atmosphere are 12.5 days (benzene), 2 days (toluene), 23 hours (ethylbenzene) and 7.8 hours (m- and p-xylene), respectively. The larger the X / B, T / B and E / B ratios are, the lower the degree of aging of the air mass.

[0005] The method of using the ratio between benzene series to judge the aging characteristics of air masses and the source of VOCs may be valid in a standardized, interference-free, single-factor experimental model. The actual changes in the VOCs composition in the ambient air are very complex. The source and existence of VOCs in the ambient air of a region are affected by many factors such as industrial emissions, motor vehicle emissions, natural source emissions, external pollution input, and meteorological conditions. The method of reversely judging the aging characteristics and sources of VOCs based solely on the ratio between benzene series remains to be discussed. Summary of the Invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a VOCs traceability evaluation method in the ambient air around an enterprise, which can achieve accurate traceability, rapid response, and multi-scenario compatibility.

[0007] The solution adopted by the present invention is: a method for tracing the source of VOCs in the ambient air around an enterprise, including:

[0008] S1. Set up monitoring points according to the distribution principle, including at least enterprise emission monitoring points and enterprise environmental monitoring points, and obtain VOCs concentration data at multiple monitoring points in the target area;

[0009] S2. Determine characteristic VOCs components based on the VOCs concentration data by any of the following methods:

[0010] The quantitative evaluation method screened out VOCs with an average daily concentration greater than 2×10 -9 components;

[0011] The occurrence number evaluation method screened out the instantaneous concentration greater than 10×10 -9 VOCs components that appear at least 5 times;

[0012] The times evaluation method screens out VOCs components with concentrations more than 3 times that of the reference point, where the reference point concentration represents the background concentration of pollutants at the monitoring point;

[0013] The maximum concentration evaluation method selects the two VOCs components with the highest concentrations at each monitoring point based on the portable GC-MS monitoring data;

[0014] S3. Calculate the traceability correlation coefficient R value based on the overlap between the target enterprise's emission characteristic VOCs component set and the enterprise's ambient air characteristic VOCs component set;

[0015] S4. Obtain traceability evaluation results based on the R value.

[0016] Furthermore, in S1, the distribution points are set up with the target enterprise as the center, and enterprise emission monitoring points, enterprise environmental monitoring points and reference points are distributed; the location and number of the distribution points are dynamically adjusted based on the monitoring technical specifications, meteorological conditions, environmental sensitive points, and historical complaint data around the enterprise.

[0017] Furthermore, the enterprise emission monitoring points include dynamic monitoring points or unorganized points in the factory area.

[0018] Furthermore, the enterprise environment monitoring point is selected from at least one of a city point, a background point, and a diffusion zone depth monitoring point.

[0019] Furthermore, the VOCs concentration data acquisition method in S1 was one of the Suma tank sampling-GC / MS method, portable GC-MS method, atmospheric VOC automatic monitoring system, and proton transfer time-of-flight mass spectrometry (PTR-ToF-MS).

[0020] Furthermore, in S3, the traceability correlation coefficient R value is calculated according to the formula R=(C / A+C / B) / 2, where A is the number of characteristic VOCs emitted by the target enterprise; B is the number of characteristic VOCs in the enterprise's ambient air; and C is the number of overlapping types of the two.

[0021] Furthermore, in S3, the traceability correlation coefficient R value is calculated according to the formula R=[C / (A-X1)+C / (B-X2)] / 2; wherein A is the number of characteristic VOCs types emitted by the target enterprise; B is the number of characteristic VOCs types in the enterprise's ambient air; X1 is the number of VOCs component types in the characteristic VOCs components of the reference point that overlap with source A; X2 is the number of VOCs component types in the characteristic VOCs components of the reference point that overlap with source B; and C is the number of VOCs types that overlap with (A-X1) and (B-X2).

[0022] The beneficial effects of the present invention are:

[0023] This invention provides a simple, efficient, and comprehensive technical solution, achieving a breakthrough in VOC pollution source tracing technology around enterprises and resolving the challenge of accurately tracing VOC pollution sources in the ambient air around enterprises. This solution achieves objective evaluation of emission sources through a scientific location strategy, dynamic multi-dimensional feature screening, quantitative overlap calculation, and an adaptive mechanism.

[0024] This invention establishes a comprehensive pollution source identification and verification system. Based on four adaptive evaluation methods (quantity evaluation, occurrence evaluation, multiple evaluation, and maximum concentration evaluation), a characteristic component screening model is established to accurately identify the emission characteristics of target enterprises. This method effectively handles conflicting data, such as emissions detected in the diffusion zone but not in the factory area. It can quickly compare with existing enterprise emissions databases and, when databases are missing, conduct source tracing analysis through on-site sampling and testing.

[0025] To address conflicting data, including detections in diffusion zones but not in factory areas, this solution compares and analyzes enterprise emission signature data, employing a bidirectional R-value verification method to accurately identify pollution sources across enterprises. All evaluation results provide standardized data support for the development of a VOCs characteristic component database, forming a three-tiered data system encompassing enterprise emission characteristics, regional background characteristics, and cross-enterprise correlation characteristics. This system not only supports rapid matching of pollution sources but also optimizes regulatory strategies through historical data analysis, such as implementing a tiered response based on R-value thresholds.

[0026] The present invention is particularly suitable for pollution monitoring and tracing during the period of suspension and resumption of production in enterprises. It can effectively identify the characteristics of unorganized emissions caused by equipment maintenance and other operations during the suspension period, accurately evaluate the effects of environmental protection facility renovation and production process improvement during the resumption period, and establish a dynamic enterprise emission library by comparing the changes in characteristic components during the suspension and resumption period, providing data support for the precise control of pollution sources. Through comparative analysis of continuous monitoring data during the suspension and resumption period, this technical solution can not only capture abnormal emission characteristics during the equipment start-up and shutdown phases, but also verify the actual emission reduction effects of technical reform measures, thus realizing dynamic environmental supervision of the entire production cycle of the enterprise.

[0027] The present invention relies on point pollution characteristics to dynamically activate four types of evaluation units, realizes adaptive feature screening, and innovatively establishes a quantitative evaluation system. The contribution of enterprises is objectively quantified through the component overlap formula, which significantly improves the accuracy of traceability conclusions and the effectiveness of environmental supervision. This method is particularly suitable for identifying pollution sources in industrial parks where multiple enterprises coexist. It effectively solves the problem of co-compatible pollution sources that are difficult to distinguish with traditional methods. In particular, its ability to parse contradictory data is significantly better than conventional traceability methods. This solution increases the efficiency of VOCs traceability in multi-enterprise industrial parks by dozens of times, providing a scientific basis for collaborative regional pollution control. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the exemplary implementation methods of the embodiments of the present disclosure, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 This is a flow chart of the VOCs source traceability evaluation method in the ambient air around the enterprise.

[0030] Figure 2 It is a traceability analysis diagram in an embodiment.

[0031] Figure 3 The figure is a schematic diagram of an industrial park and surrounding residential areas in an embodiment.

[0032] Figure 4 This is a summary table of characteristic VOCs components of enterprises in a certain industrial park and surrounding residential areas in an embodiment.

[0033] Figure 5 This is a summary table of parameters of the traceability calculation process of different enterprises in a certain industrial park to residential areas in an embodiment.

[0034] Figure 6 This is a schematic diagram of monitoring points in the example of Ding Enterprise.

[0035] Figure 7 The 3-day average concentration of VOCs components at the reference point in the example of Company D (×10 -9 ).

[0036] Figure 8 This is a summary table of characteristic VOCs components at each monitoring point in the Ding enterprise implementation example.

[0037] Figure 9 The instantaneous concentration at the monitoring point of the Ding enterprise embodiment is greater than 10×10 -9 Statistics of VOCs components (times).

[0038] Figure 10 It is the average value (times) of the VOCs components in the ambient air of the diffusion area of ​​Enterprise Ding's embodiment relative to the reference point.

[0039] Figure 11 This is the number of times the characteristic VOCs component with the maximum concentration appears at the factory site of Enterprise D (times).

[0040] Figure 12 This is a summary table of calculation results of the traceability correlation coefficient R of the surrounding ambient air affected by the enterprise. DETAILED DESCRIPTION

[0041] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0042] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. The present invention is not limited to the above embodiments. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the scope of protection of the present invention.

[0043] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present application. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0044] Reference Attachment Figure 1 , describing the steps of the method for tracing the source of VOCs in the ambient air surrounding an enterprise of the present invention. The method includes steps S1-S4.

[0045] In S1, monitoring points are set up according to the layout principles, including enterprise emission monitoring points and enterprise environmental monitoring points. Specifically, enterprise emission monitoring points include dynamic monitoring points or unorganized points within the factory area. Enterprise environmental monitoring points are selected from urban points, background points, or in-depth monitoring points within the diffusion zone. VOC concentration data are obtained from multiple monitoring points in the target area. The layout principles for monitoring points are based on the "Technical Specifications for the Layout of Ambient Air Quality Monitoring Points (Trial)" (HJ 664-2013), and also refer to the layout principles of the "Technical Guidelines for Monitoring Unorganized Emissions of Atmospheric Pollutants" (HJ / T 55-2000). Factors such as the enterprise's geographic location, seasonal wind direction changes, and the company's historical complaint coverage are comprehensively considered to ensure the representativeness, comparability, integrity, stability, and operability of the layout points to the greatest extent possible. For example, the distribution of monitoring points is centered on the target enterprise, and enterprise emission monitoring points and enterprise environmental monitoring points are set up. The enterprise emission monitoring points include 1 monitoring point (for complaint hotspots, 8 unorganized points in the factory area (to capture unorganized emissions); enterprise environmental monitoring points include 1 background point (for background concentration), 1 city point (representing urban pollution), 1 reference point (as a comparison benchmark), and 50 diffusion zone depth monitoring points (distributed along the wind direction). These points can be accurately deployed through GPS positioning and map marking. The data acquisition method includes one of the Suma tank sampling GC / MS method, the portable GC-MS concentrated thermal desorption method, the atmospheric VOC automatic monitoring system method or the PTR-ToF-MS method. Specifically, the Suma tank sampling is used for long-term stable data collection, while the portable GC-MS is suitable for rapid on-site analysis. The Suma tank sampling laboratory GC-FID / MS method is currently the most commonly used environmental air VOCs test method. This method has a low detection limit, high laboratory analysis accuracy, and reliable data. In one embodiment, for For a coking plant, Suma tank sampling was used, with one reference point upwind and three fixed points in each of the three depth directions downwind. Three points close to the enterprise perimeter were selected, for a total of 10 points. The sampling frequency was 3 times / day for 3 days, at 7:00, 14:00, and 18:00 respectively. In one embodiment, for the periphery of a chemical plant, technicians used a portable GC-MS method to monitor 30 diffusion points on-site to collect data. The three dominant wind directions were east (E), northeast east (ENE), and southeast east (ESE). Three reference points corresponding to wind direction, 10 unorganized VOC emission points within the plant, and 30 monitoring points in three depth directions downwind, for a total of 43 points, ensured that the spacing between points conformed to the wind direction model to obtain the VOC concentration matrix. The sampling frequency was once per day for a total of 5 days. The atmospheric VOC rapid automatic monitoring system method can continuously monitor VOCs in ambient air for 24 hours. It is commonly used for VOC monitoring at automatic monitoring stations. It has good stability, low detection limit, and high accuracy. This project uses it for fixed-point continuous monitoring of monitoring points.In one example, to monitor a petrochemical enterprise, the instrument was placed at a monitoring point downwind from the east, continuously monitoring VOCs for at least five days. The advantage of proton transfer time-of-flight mass spectrometry (PTR-ToF-MS) lies in the relatively gentle chemical ionization reaction. Compared to electron impact ionization, proton transfer reactions produce fewer ion fragments, resulting in low analytical detection limits and high accuracy. This project uses it for continuous monitoring at a reference point. In one example, to track the emissions impact of a chemical enterprise, the instrument was placed at an upwind reference point, continuously monitoring VOCs for at least five days.

[0046] S2 is based on VOCs concentration data. Characteristic pollutants generally refer to unique pollutants other than conventional pollutants in pollutants emitted by pollution sources. The concept of characteristic pollutants is used to propose "characteristic VOCs components" in ambient air. This is mainly to evaluate the VOCs pollution characteristics in ambient air. Its screening method is mainly determined based on the comprehensive determination of point characteristics and VOCs testing methods. Characteristic VOCs components are determined by one of the following four methods. The coordinated application of the four types of screening methods can more objectively reflect the characteristics of VOCs pollution:

[0047] Quantitative evaluation method

[0048] The daily average concentration was greater than 2×10 -9 The principle of quantity evaluation is: the VOCs component with high concentration in ambient air is regarded as the characteristic VOCs component. The average value of monitoring for multiple days is greater than 2×10 -9 The VOCs components are taken as characteristic VOCs components. Take 2×10 -9 As the threshold value of characteristic VOCs components in ambient air, it is mainly based on the background experience value of VOCs components in ambient air over many years and the detection limit of VOCs test method. The multi-day average value in ambient air is greater than 2×10 -9 For a specific VOC component, it can be virtually confirmed that it is clearly detected. This method is suitable for ambient air at monitoring points where pollution sources are less likely to affect the air quality and where air quality fluctuations are relatively stable. It is also used to screen for characteristic VOC components in ambient air at background points, urban areas, reference points, and diffusion zones. It is not suitable for evaluating areas where VOC levels fluctuate significantly. This method can stably identify high-concentration background pollutants that persist over long periods of time in the environment, avoiding misjudgments due to transient fluctuations, making it suitable for background concentration analysis.

[0049] Occurrence evaluation method

[0050] The instantaneous concentration of the extraction by the occurrence number evaluation method is greater than 10×10 -9For components that appear at least 5 times, the principle of occurrence evaluation is: VOCs components that appear repeatedly in high concentrations in ambient air are considered characteristic VOCs components. Monitoring points are affected by factors such as the emission cycle of pollution sources, types of pollutants, unorganized emission patterns in the factory area, and wind direction. The instantaneous concentration of a certain VOCs component may reach a very high level. Therefore, using only the mean value of the VOCs component to evaluate cannot objectively reflect the impact of the pollution source on the monitoring point. In this case, the VOCs component with an instantaneous value greater than 10×10 -9 The characteristic VOCs components of the monitoring point were determined by the method of times. During the monitoring period, the instantaneous value of each VOCs component was greater than 10×10 -9 VOCs detected more than five times are characteristic of the monitoring point. This method is suitable for areas with large fluctuations in VOC levels in ambient air and is not suitable for screening characteristic VOCs in stable ambient air. This method can effectively capture intermittent high-concentration emission events and is particularly suitable for monitoring areas affected by fugitive or accidental emissions from enterprises. It can be specifically used for dynamic monitoring points with significant VOC fluctuations.

[0051] Multiple evaluation method

[0052] The times evaluation method screens out VOCs components with concentrations more than 3 times that of the reference point, where the reference point concentration represents the background concentration of pollutants at the monitoring point, highlighting the contribution of the target enterprise. At present, the national and local governments have not yet issued VOCs control standards in ambient air, and there is no national standard for VOCs in the ambient air around enterprises to refer to and evaluate. Therefore, the clean air of the reference point, which is less affected by pollution, is used as a benchmark to evaluate the ambient air around the enterprise. The layout of the reference points should be based on the principle of being able to represent the background concentration of pollutants at the monitoring point. The reference point should not be affected by or as little as possible by the measured unorganized emission source. The reference point should strive to avoid the influence of other unorganized emission sources and organized emission sources in its vicinity, and avoid those emission sources that may have a significant impact on the reference point but have no significant impact on the monitoring point. The general selection conditions for the reference point are that it is located in the upwind direction of the dominant wind direction of the monitoring point, and the distance from the pollution source is greater than the preset threshold. In one embodiment, three reference points are set, and the reference point is shifted 8km eastward with the target enterprise as the center to set the east reference point to avoid chemical park enterprises. To ensure the integrity and reliability of the reference point monitoring data and to consider sampling feasibility, two additional reference points, designated the Northeast East and Southeast East reference points, were established 7 km north and 5 km south of the Due East reference point, respectively, based on actual road conditions. Monitoring results showed that the VOC composition and concentration levels at each reference point were largely consistent. Based on this, one of the reference points (the Due East reference point) was ultimately selected as the official backup reference point. If the VOC composition and concentration levels of multiple candidate reference points differed significantly, the monitoring point with the lowest pollutant concentration was selected as the final reference point. The VOC component concentration data in the ambient air of the enterprise's surrounding diffusion zone were divided by the reference point data for the same period to determine the multiples by which the VOC component in the diffusion zone exceeded the reference point data. These multiples were then evaluated accordingly, with VOC components with an average multiple greater than three times the value being considered as characteristic VOC components for the multiple evaluation. This method for screening characteristic VOC components has high uncertainty, and its evaluation performance may be poor if the selected reference clean air is contaminated. Despite the uncertainties, this approach can highlight the relative impact of corporate emissions on the surrounding environment, providing a relative assessment tool, especially in the absence of national standards.

[0053] Maximum concentration evaluation method

[0054] The maximum concentration evaluation method extracts the top two high-concentration components at each monitoring point based on the portable GC-MS data to simplify the analysis. For portable GC-MS, due to the limitations of test conditions, the types of monitored VOCs components are relatively small and the detection limit is relatively high. In this case, the two VOCs components with the maximum concentrations under the test conditions are selected as characteristic VOCs components, and the number of occurrences of characteristic VOCs components at different points in the same area are evaluated. This method is suitable for screening characteristic VOCs components in regional environments tested by portable GC-MS, such as enterprise factories and diffusion areas. This method can screen out the main VOCs components in regional ambient air, but the screening effect on characteristic VOCs with slightly lower concentrations is poor. This method is fast and simple, and is particularly suitable for portable equipment to quickly screen major pollutants and improve on-site monitoring efficiency.

[0055] In practice, a corresponding evaluation method can be applied based on the type of monitoring point. For diffuse zone monitoring points, a multiple evaluation algorithm compares component concentrations with reference point data in real time to screen for components exceeding standards. For fugitive emission points within the plant area, a maximum concentration evaluation algorithm automatically extracts the top two high-concentration components from the portable GC-MS data. This dynamic adaptation mechanism ensures that characteristic component identification closely matches the pollution characteristics of the point.

[0056] In one embodiment, characteristic VOCs components of a chemical company are monitored during shutdown and resumption of production:

[0057] (1) Monitoring points: During the shutdown period, the GC-FID / MS test method quantitatively screened out 13 characteristic VOCs components at the monitoring point and 6 characteristic VOCs components in the diffusion zone; after the resumption of production, the quantitative evaluation screened out 9 characteristic VOCs components at the monitoring point and 4 characteristic VOCs components in the diffusion zone, respectively. The monitoring point had the most characteristic VOCs components in both monitoring periods, indicating that the monitoring point was most seriously polluted by characteristic VOCs. Comparing the characteristic VOCs components that appeared at the shutdown and resumption monitoring points, the 9 characteristic VOCs components that appeared after the resumption of production were all included in the 13 characteristic VOCs components during the shutdown period.

[0058] (2) Diffusion zone: The characteristic VOCs components of suspension / resumption were evaluated by comparative quantity. The four characteristic VOCs components that appeared after resumption were all included in the six characteristic VOCs components during the suspension period. The types of characteristic VOCs components screened out by multiple evaluation were 14 and 14 respectively, of which 5 were overlapped. The types of characteristic VOCs components screened out by portable GC-MS analysis in the diffusion zone and the evaluation of the number of occurrences of the maximum concentration were 9 and 10 respectively, of which 7 were overlapped.

[0059] (3) Factory: The portable GC-MS analysis of the maximum concentration occurrence frequency evaluated and screened out 11 and 9 characteristic VOCs components for suspension and resumption of production, respectively. The 9 characteristic VOCs components that appeared after resumption of production were all included in the 11 characteristic VOCs components during the suspension period.

[0060] Comparing the characteristic VOCs components of the enterprises during the shutdown and resumption of production, the results show that the VOCs pollution in the ambient air of the enterprise factory area, monitoring points, and diffusion areas was more serious during the shutdown period. The investigation found that during the shutdown period, the enterprise carried out renovations and maintenance on production equipment and purification facilities, which involved opening equipment, reaction tanks, reactors, cleaning pipelines, etc., and the VOCs remaining in the original equipment, reaction tanks, reactors, and pipelines were discharged in large quantities in an unorganized form. For example, during the shutdown period, our center received complaints about odor from residents living near the enterprise. The instantaneous concentration of VOCs in the ambient air of the monitoring point using a portable GC-MS on-site monitoring reached ×10 -6 After resuming production, the company's transformation of the VOCs purification device has achieved initial results, with the production equipment and purification equipment operating continuously and stably, and the VOCs content in the ambient air around the company has dropped significantly.

[0061] During the period of suspension and resumption of production, key technological breakthroughs were achieved through multi-dimensional monitoring and verification: high-precision identification of dynamic pollution sources was achieved, and the instantaneous unorganized emission peak of one part per million during equipment maintenance was successfully captured. The effect of reducing characteristic pollutants by more than 10% during the resumption of production after the purification device modification was quantitatively verified.

[0062] The application of four evaluation methods during shutdown and resumption of production provides a key basis for operational and maintenance decision-making. This not only provides early warning of high emission risks during equipment maintenance periods to optimize shutdown processes, but also verifies the effectiveness of environmental technology improvements. This technology significantly improves the accuracy of traceability conclusions and the reliability of environmental monitoring in complex scenarios with multiple interference sources and fluctuating operating conditions.

[0063] S3 calculates the traceability correlation coefficient R value based on the overlap between the target enterprise's emission characteristic VOCs component set (such as benzene series in the enterprise's emission inventory) and the monitoring point characteristic VOCs component set. The formula is R=(C / A+C / B) / 2, where A is the number of enterprise emission characteristic types, B is the number of ambient air characteristic types, and C is the number of overlapping types. During operation, the component lists of A and B are compared through the database, and C is calculated and inserted into the formula to obtain the R value (range 0-1, the higher the value, the greater the contribution of the enterprise). According to the formula Figure 2 As shown in the figure, when A and B have no overlapping components, that is, C = 0, the formula gives R = 0%, and the traceability of A and B is completely unrelated. When A = B = C, that is, the characteristic pollutants of A and B completely overlap, the formula gives R = 100%, and the traceability of A and B is completely correlated. In the other three cases, R is between 0% and 100%, and the larger the R value, the stronger the traceability correlation.

[0064] In one embodiment, the emission characteristics of a plastics factory include 5 components (A=5), the characteristic components of the monitoring point include 8 components (B=8), and there are 3 overlapping components such as toluene, styrene, and chlorobenzene (C=3). Then R=(3 / 5+3 / 8) / 2=0.475, indicating a moderate correlation.

[0065] S3 calculates the traceability correlation coefficient R value. The R value can also be calculated using the formula R = [C / (A-X1) + C / (B-X2)] / 2; where A is the number of characteristic VOCs emitted by the target enterprise; B is the number of characteristic VOCs in the enterprise's ambient air; X1 is the number of VOC components in the reference point characteristic VOCs that overlap with source A; X2 is the number of VOC components in the reference point characteristic VOCs that overlap with source B; and C is the number of VOCs that overlap between (A-X1) and (B-X2). (A-X1) and (B-X2) represent the number of characteristic VOC components in the corresponding area after deducting the background characteristic VOCs, and C is the number of VOCs that overlap between (A-X1) and (B-X2), making the evaluation results more objective.

[0066] In one example, there are three companies in an industrial park: A, B, and C. Company A is a chemical coatings manufacturer, and there are certain benzene-related VOCs pollutant emissions during the production process. Company B is an animal feed additive manufacturer, and there are sulfur-containing volatile organic compounds emitted during the production process. Company C is a petroleum refining company, and there are alkane VOCs pollution emissions during the production process. The dominant wind direction in the area is easterly all year round. There is a residential area 1 km to the west of the industrial park. The VOCs pollution of the three companies has an impact on the residential area. See the details. Figure 3 .

[0067] Points were set up in three enterprises and residential areas to monitor the actual VOCs conditions in the three enterprises and residential areas, and characteristic VOCs components of enterprises A, B, and C and residential areas were screened out. The screening results are shown in Figure 4 Calculate the correlation coefficient R value of the enterprise to the residential area according to the formula R=[C / (A-X1)+C / (B-X2)] / 2. The calculation of the correlation coefficient R is shown in Figure 5 , it can be seen from the figure that R 甲 =22.5%, R 乙 =40%, R 丙 =60%.

[0068] Finally, S4 generates a source-tracing assessment based on the R value. This process uses thresholds to determine the impact and compile a report or alert. For example, when R = 50%, an assessment of the suspected impact of the enterprise is generated, guiding investigations. In an example involving three companies, A, B, and C, an R-value source-tracing analysis (with a threshold set, such as R ≥ 60% for strong correlation) revealed signals indicating that the company's activities were suspected of impacting the residential environment, recommending an investigation. The analysis generally determined that, of the three companies, Company C had the most significant impact on the residential area (its R value exceeded the threshold for strong correlation). Based on this, a report was compiled, recommending a focus on verifying Company C's production activities, the operation of its pollution control facilities, and its pollutant emissions. Furthermore, to ensure comprehensive accountability, the report also requires a review and confirmation of the actual environmental impact of Companies A and B to ultimately identify the primary responsible party. This analytical conclusion, along with the corresponding operational recommendations (R-value threshold determination, source-tracing assessment, and report compilation), forms a complete technical support chain.

[0069] In one embodiment, for target enterprise D, technicians based their work on the "Technical Specifications for the Layout of Ambient Air Quality Monitoring Points (Trial)" (HJ 664-2013), and also referred to the "Technical Guidelines for Monitoring Unorganized Emissions of Air Pollutants" (HJ / T 55-2000) for the layout principles. They also comprehensively considered factors such as the enterprise's geographical location, seasonal wind direction changes, and the scope of historical complaints received by the enterprise, to ensure the representativeness, comparability, integrity, stability, and operability of the layout points to the greatest extent possible. See the layout diagram for details. Figure 6 , the specific situation is as follows:

[0070] (1) Reference point: To investigate the impact of Ding Enterprise on the downwind ambient VOCs, the monitoring point was located at the east-upwind reference point of Ding Enterprise, with reference to the Technical Guidelines for Monitoring Unorganized Emissions of Air Pollutants (HJ / T 55-2000). During the monitoring period, the prevailing wind direction was east. Suma tank sampling GC-FID / MS and portable GC / MS were used for monitoring at the reference point. The monitoring frequency was three times per day, with sampling at 7:00, 14:00, and 18:00, for three consecutive days.

[0071] (2) Unorganized emission points in the factory: Due to the volatile nature of VOCs, VOCs pollutants are emitted into the atmosphere in an unorganized form from pipeline component leaks, organic liquid storage tanks, organic liquid loading operations, wastewater volatilization, and process processes. In some industries such as petrochemicals, more than 70% of VOCs emissions come from unorganized emissions. Therefore, for VOCs monitoring in enterprises, unorganized emission monitoring in the factory area is the focus of VOCs monitoring. Ding Enterprise is a comprehensive petrochemical and petroleum refining enterprise. The company has branches and facilities such as aromatics plant, refinery, olefin plant, chemical plant, and storage tank area within the factory area. The factory area is large, so 10 unorganized monitoring points in the factory area of ​​Ding Enterprise were set up to comprehensively monitor the unorganized VOCs emissions of Ding Enterprise. The unorganized points in the factory area were monitored using the Suma tank sampling GC-FID / MS method and the portable GC / MS method. The monitoring frequency was 3 times / day, with sampling at 7:00, 14:00, and 18:00 respectively, and monitoring was carried out continuously for 3 days.

[0072] (3) Monitoring points: The Technical Specifications for the Layout of Ambient Air Quality Monitoring Points (Trial) (HJ 664-2013) stipulate that pollution monitoring points are monitoring points set up to monitor the impact of major pollution sources and pollution collection areas such as industrial areas on local ambient air quality. The representative range is generally 100-500m in radius. In principle, pollution monitoring points should be set up in areas with high concentrations of pollutants that may affect human health and in areas where major pollution sources have a significant impact on ambient air quality. Pollution monitoring points should be arranged based on the intensity of emission sources and major pollution projects. They should be set up in the maximum ground concentration area downwind of the dominant wind direction and the second dominant wind direction (generally the dominant wind direction in the heaviest pollution season) of the source, and should be arranged based on the principle of capturing the maximum pollution characteristics. For industrial parks with a large number of concentrated fixed pollution sources, pollution monitoring points should, in principle, be set up at the boundary of the industrial source area downwind of the dominant wind direction and the second dominant wind direction (generally the dominant wind direction in the heaviest pollution season), taking into account the maximum ground concentration of the pollution sources with the highest emission intensity and the pollution projects. This monitoring site was located 500 meters west of Gate 3 of Ding Enterprise, downwind due east of the enterprise, taking into account factors such as the seasonal dominant and secondary dominant wind directions and the maximum drop-off range of VOC emissions from Enterprise D. This location meets the monitoring site requirements. Furthermore, public complaints about chemical odors have been frequent in the area surrounding this site. To comprehensively monitor VOC pollution in the area, an automated atmospheric VOC monitoring system was implemented at the site, providing 24-hour continuous monitoring for at least five consecutive days. This automated atmospheric VOC monitoring system utilizes ultra-low temperature preconcentration coupled with gas chromatography-mass spectrometry / flame ion detector (GC-FID / MS), following the same principles as GC-FID / MS.

[0073] (4) Deep monitoring points in the diffusion zone: With reference to the HJ / T55-2000 point distribution principle, deep monitoring points were distributed in the diffusion zone downwind of Ding Enterprise. With Ding Enterprise as the center, points were distributed in depth along the downwind extension lines of the east, northeast, and southeast winds. The minimum distance between points was 1 km. If characteristic pollutants were clearly found during monitoring, the distribution of points could be increased, with 3 points in each of the three depth directions, for a total of 9 monitoring points. The selected points were preferably located in open areas with good ventilation, without surrounding buildings or trees, and the sampling height was at least 1.5 m above the ground to avoid the impact of vehicle exhaust on the monitoring. The 9 downwind diffusion zone deep monitoring points were monitored using the Suma tank sampling GC-FID / MS method and the portable GC / MS method. The monitoring frequency was 3 times / day, with sampling at 7:00, 14:00, and 18:00, for 3 consecutive days.

[0074] S2 screens characteristic VOCs components based on VOCs concentration data. The screening method is mainly determined based on the site characteristics and VOCs testing methods. Characteristic VOCs components are determined by one of four methods:

[0075] (1) Quantitative evaluation method

[0076] In the example of the target enterprise D, the VOCs monitoring data of the reference point, the unorganized point in the factory area, the monitoring point and the deep monitoring point in the diffusion area were used to screen out the corresponding characteristic VOCs components using the quantitative evaluation method, and the points with the multi-day average value greater than 2×10 -9 The VOCs components are used as characteristic VOCs components. Among them, the 3-day average values ​​of 106 VOCs tested at the reference point are shown in Figure 7 ,Depend on Figure 7 It can be seen that the characteristic VOCs components of the reference point are propane and acetone, a total of 2 types. The same method is used to screen the characteristic VOCs components of the unorganized points, monitoring points and deep monitoring points in the diffusion area of ​​the factory area. The screening results are shown in Figure 8 .

[0077] (2) Occurrence evaluation method

[0078] In the embodiment of Enterprise D, the instantaneous value of the VOCs component tested at the monitoring point is greater than 10×10 -9 See the statistics for frequency Figure 9 .Depend on Figure 9 It can be seen that the instantaneous concentration of VOCs at the monitoring point is greater than 10×10 -9 The VOCs components that occurred more than 5 times were: isopentane, n-butane, etc., a total of 14 types, with instantaneous concentrations greater than 10×10 -9 The most frequent occurrence was isopentane, which appeared 96 times. The final results of the characteristic VOCs components screened by the occurrence evaluation method at the monitoring point are shown in Figure 8 .

[0079] (3) Multiple evaluation method

[0080] In the example of Enterprise D, the VOCs component concentration data of the Suma tank sampling GC-FID / MS method monitoring data at the diffusion zone depth monitoring point is divided by the reference point data of the same period to obtain the multiple of each VOCs component relative to the reference point, see Figure 10 .Depend on Figure 10 It can be seen that the multiples of 102 VOCs components in the downwind diffusion area of ​​the enterprise are basically greater than 1 compared with the reference point, indicating that the overall level of VOCs in the ambient air of the enterprise diffusion area is higher than the reference point. Among them, there are 14 VOCs components with a level greater than 3 times, including chlorobenzene and styrene. The characteristic VOCs components screened by the multiple evaluation method in the diffusion area are shown in Figure 2. Figure 8 .

[0081] (4) Maximum concentration evaluation method

[0082] In the example of Enterprise D, the number of occurrences of characteristic VOCs components screened out by the maximum concentration evaluation method in the plant area of ​​Enterprise D is shown in Figure 11 ,from Figure 11 It can be seen that benzene and toluene are the most common characteristic pollutants in the enterprise plant area. The characteristic VOCs components screened by the maximum concentration evaluation method in the enterprise plant area and diffusion area are shown in Figure 8 .

[0083] S3 In the embodiment of Enterprise D, according to Figure 8 , get the values ​​of A, B, X1, X2, and C, substitute the values ​​of A, B, X1, X2, and C into the formula R=[C / (A-X1)+C / (B-X2)] / 2, and the calculation results are shown in Figure 12 . Suma tank sampling GC-FID / MS analysis was used in both the plant area and the diffusion area, and the quantity evaluation method was used to screen the characteristic VOCs components. The traceability correlation coefficient R value was calculated to be 64.2%; portable GC / MS monitoring was used in both the plant area and the diffusion area, and the maximum concentration evaluation method was used to screen the characteristic VOCs components. The traceability correlation coefficient R value was calculated to be 70.7%; GC-FID / MS monitoring was used in both the monitoring points and the diffusion area, and the quantity evaluation method was used to screen the characteristic VOCs components. The traceability correlation coefficient R value was calculated to be 66.8%; GC-FID / MS monitoring was used in both the monitoring points and the diffusion area, and the characteristic VOCs components were screened by the diffusion area quantity evaluation method and the monitoring point occurrence number evaluation method. The traceability correlation coefficient R value was calculated to be 82.5%.

[0084] S4 In the embodiment of Enterprise D, the traceability correlation coefficient R ranges from 64.2% to 82.5%.

[0085] Specifically, the VOCs traceability correlation coefficient R value between the factory area / monitoring point and the diffusion area calculated through a combination of multiple monitoring and evaluation methods (including the Suma tank sampling GC-FID / MS analysis combined quantity evaluation method for the factory area / diffusion area, the portable GC / MS combined with the maximum concentration evaluation method; the GC-FID / MS monitoring combined quantity evaluation method for the monitoring point / diffusion area, and the occurrence number evaluation method for the monitoring point combined with the diffusion area quantity evaluation method) ranged from 64.2% to 82.5% (with the highest value reaching 82.5%). All R values ​​were significantly higher than the conventional judgment threshold (such as R≥60%), proving that the VOCs emitted by Enterprise Ding made a significant contribution to the VOCs in the ambient air in its downwind diffusion area. High R values ​​(64.2% and 70.7%) obtained for the plant and diffusion zones using different methods directly confirm that enterprise emissions are the dominant factor in the highly similar VOC pollution characteristics within the diffusion zone. High R values ​​(66.8% and 82.5%) for monitoring points and the diffusion zone, particularly the 82.5% strong correlation obtained using the combined monitoring point occurrence and diffusion zone volume evaluation methods, further strengthen the evidence linking the enterprise's emissions to the diffusion zone. Combined with these multiple sets of high correlation results, particularly the 82.5% strong correlation, this provides key quantitative evidence confirming that Enterprise D bears significant responsibility for VOC pollution within the diffusion zone.

[0086] Furthermore, in the example of Company D, chlorobenzene was found in the characteristic VOCs screening of the diffusion zone using the quantitative evaluation method, the multiple evaluation method, and the maximum concentration evaluation method. Chlorobenzene was detected multiple times as a characteristic VOC component in the diffusion zone, indicating the presence of a chlorobenzene pollution source that was continuously impacting the diffusion zone. However, when monitoring unorganized VOCs in the plant area using a portable GC-MS, chlorobenzene was not detected as a characteristic VOC component within the company's plant. An investigation revealed that another chemical company adjacent to the company had a 120,000 t / yr chlorobenzene production facility, and that the chlorobenzene pollution detected in the diffusion zone originated from emissions from the adjacent company. Combined with R-value analysis, Company D was ruled out as responsible and the adjacent chemical company was accurately identified as the source of the chlorobenzene pollution. This multi-dimensional screening mechanism can effectively address the source tracing challenge in complex pollution scenarios, providing a precise technical solution for environmental regulation.

[0087] By innovatively analyzing the contradictions in the monitoring data of the diffusion zone and the factory area (such as the continuous detection of chlorobenzene, a characteristic component of the diffusion zone, and its complete absence in the responsible enterprise's factory area), combined with cross-enterprise investigations (discovery of a large-scale chlorobenzene unit nearby) and multi-method collaborative verification (concentration ratio, peak location, and R-value responsibility exclusion), we can effectively distinguish co-located pollution sources, accurately locate the real emission sources (such as adjacent chemical enterprises), and completely eliminate interference from non-responsible parties, thus solving the core problem of source analysis in complex pollution scenarios.

[0088] Based on the comparison of monitoring data from multiple points (factory area, monitoring points, diffusion area), the regional background characteristic components (such as ethane) can be accurately identified, effectively avoiding misjudgment of them as corporate emissions, and significantly improving the reliability and anti-interference ability of the traceability results.

[0089] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the embodiments of the present disclosure. It should be understood that the above description is only a specific implementation method of the embodiments of the present disclosure and is not intended to limit the scope of protection of the embodiments of the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the embodiments of the present disclosure should be included in the scope of protection of the embodiments of the present disclosure.

Claims

1. The VOCs source evaluation method in the ambient air around the enterprise is characterized by: include: S1. Set up monitoring points according to the distribution principle, including at least enterprise emission monitoring points and enterprise environmental monitoring points, and obtain VOCs concentration data at multiple monitoring points in the target area; S2. Determine characteristic VOCs components based on the VOCs concentration data by any of the following methods: The quantitative evaluation method screened out VOCs with an average daily concentration greater than 2×10 -9 components; The occurrence number evaluation method screened out the instantaneous concentration greater than 10×10 -9 VOCs components that appear at least 5 times; The times evaluation method screens out VOCs components with concentrations more than 3 times that of the reference point, where the reference point concentration represents the background concentration of pollutants at the monitoring point; The maximum concentration evaluation method selects the two VOCs components with the highest concentrations at each monitoring point based on the portable GC-MS monitoring data; S3. Calculate the traceability correlation coefficient R value based on the overlap between the target enterprise's emission characteristic VOCs component set and the enterprise's ambient air characteristic VOCs component set; S4, according to the R value to obtain the traceability evaluation results; Among them, in S3, the traceability correlation coefficient R value is calculated according to the formula R=(C / A+C / B) / 2, where A is the number of characteristic VOCs emitted by the target enterprise; B is the number of characteristic VOCs in the enterprise's ambient air; and C is the number of overlapping types of the two.

2. The method for tracing the source of VOCs in the ambient air surrounding an enterprise according to claim 1, characterized in that: In S1, the distribution of points is to set up monitoring points with the target enterprise as the center, and to set up enterprise emission monitoring points, enterprise environmental monitoring points and reference points; the location and number of the distribution points are dynamically adjusted based on monitoring technical specifications, meteorological conditions, environmental sensitive points, and historical complaint data around the enterprise.

3. The method for tracing the source of VOCs in the ambient air surrounding an enterprise according to claim 2, characterized in that: The enterprise emission monitoring points include dynamic monitoring points or unorganized points in the factory area.

4. The method for tracing the source of VOCs in the ambient air surrounding an enterprise according to claim 2, characterized in that: The enterprise environment monitoring point is selected from one of a city point, a background point, and a diffusion zone depth monitoring point.

5. The method for tracing the source of VOCs in the ambient air surrounding an enterprise according to claim 1, characterized in that: The VOCs concentration data in S1 were obtained using one of the following methods: Suma tank sampling-GC / MS method, portable GC-MS method, atmospheric VOC automatic monitoring system, and proton transfer time-of-flight mass spectrometry.

6. The method for tracing the source of VOCs in the ambient air surrounding an enterprise according to claim 2, characterized in that: In S3, the traceability correlation coefficient R value is calculated according to the formula R=[C / (A-X1)+C / (B-X2)] / 2; where A is the number of characteristic VOCs types emitted by the target enterprise; B is the number of characteristic VOCs types in the enterprise's ambient air; X1 is the number of VOCs component types in the characteristic VOCs components of the reference point that overlap with source A; X2 is the number of VOCs component types in the characteristic VOCs components of the reference point that overlap with source B; and C is the number of VOCs types that overlap between (A-X1) and (B-X2).

Images