A method and system for assessing the impact of volcanic ash on urban air quality

Abstract

The application provides a method and system for evaluating the influence of volcanic ash on urban air quality, relating to the technical field of environmental atmospheric pollutant evaluation and volcanic disaster monitoring, which comprises taking the concentration of sulfate in particulate matter as a key indicator, obtaining air quality monitoring data before, during and after volcanic eruption, automatically determining the influence period in combination with a dynamic threshold, simulating the diffusion path and concentration distribution of volcanic ash by using an atmospheric diffusion model, and predicting the influence range. A visual geographic information map is generated by Kriging spatial interpolation, and a characteristic index (sulfate / concentration ratio) is calculated to divide the influence level of the station, and a regional comprehensive influence index is calculated in combination with the weight of population density, so as to realize high, medium and low influence classification. The application can accurately quantify the contribution of volcanic eruption to urban air quality, and provide a scientific basis for air quality early warning and prevention and control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental atmospheric pollutant assessment and volcanic disaster monitoring, and in particular to a method and system for assessing the impact of volcanic ash on urban air quality. BACKGROUND

[0002] Volcanic eruption is an important natural geological phenomenon, which releases a large amount of volcanic ash, gas and other particulate matter during the eruption process, among which sulfate is one of the key components of particulate matter formed after volcanic eruption. These substances spread to the surrounding urban areas along the atmospheric circulation, especially coastal cities, and have a significant impact on urban air quality, which is manifested in a series of environmental and health problems such as reduced visibility and increased risk of respiratory diseases.

[0003] At present, the evaluation means for the impact of volcanic eruption on urban air quality is not perfect, and there is a lack of systematic and accurate evaluation method. The existing technology focuses more on the monitoring of conventional pollutants (such as PM2.5, PM10, etc.), and has not established an evaluation system with sulfate concentration in particulate matter as the core index, making it difficult to accurately identify and quantify the real impact of volcanic eruption on urban air quality. 、

[0004] In addition, the existing evaluation method also has shortcomings in the simulation of volcanic ash diffusion path and the prediction of influence range, and has not effectively combined atmospheric diffusion model and real-time monitoring data, resulting in limited spatio-temporal accuracy of the evaluation results. Therefore, it is urgent to develop an evaluation method with sulfate concentration as the main technical index, combined with multi-source monitoring and model simulation, to provide technical support for scientifically judging the impact of volcanic eruption on urban air quality and guiding the city to take targeted prevention and control measures. SUMMARY

[0005] To this end, the present application provides a method and system for evaluating the impact of volcanic ash on urban air quality, to solve the problem of lack of key indicators such as sulfate concentration in the prior art, and inability to accurately quantify and grade the impact of volcanic eruption on urban air quality.

[0006] To solve the above technical problems, the present application provides a method for evaluating the impact of volcanic ash on urban air quality, which comprises the following steps:

[0007] Step S1: obtaining air quality monitoring data of the area to be evaluated before, during and after the volcanic eruption, the data at least including the concentration of sulfate in particulate matter, the concentration of PM2.5 and the concentration of PM10;

[0008] ​​​Step S2: Based on the monitoring data, automatically determine the start time and stop time of the volcanic ash impact by dynamic threshold conditions to define the accurate period of influence;

[0009] Step S3: Use the atmospheric diffusion model to simulate the diffusion path and concentration distribution of sulfate particles in volcanic ash, combined with the meteorological conditions and volcanic ash release source strength at the time of volcanic eruption, to predict the impact range on different cities or sites;

[0010] Step S4: Statistically analyze the changes in sulfate concentration at each site during the accurate period, compare the data before and after the volcanic eruption and at different geographic locations, and determine the direct impact degree of the volcanic eruption;

[0011] Step S5: Based on the impact range predicted in step S3 and the accurate period determined in step S2, cut out the data set of the affected area, and use spatial interpolation method to generate a visual geographic information map of sulfate concentration;

[0012] Step S6: Calculate the characteristic index of each evaluation site , ; Based on the value of the characteristic index , divide the sites into different impact levels; combined with the weight of each site, calculate the comprehensive impact index of the region, and classify the region according to the comprehensive impact index .

[0013] Preferably, in step S1, the air quality monitoring data also includes heavy metal concentration and organic matter concentration in particulate matter; the sulfate concentration is monitored by ion chromatography, the concentration is monitored by ultraviolet fluorescence method, the concentration is monitored by ray method or oscillating balance method.

[0014] Preferably, in step S2, the dynamic threshold condition includes: the start time is after the volcanic eruption, the sulfate concentration in the evaluation area increases, the sulfate concentration in the air is 0.2 times higher than that in the previous hour, and the percentage in particulate matter is 2 percentage points higher than that in the previous hour; the stop time is when the sulfate concentration decreases compared to the previous hour, and the percentage in particulate matter is 2 percentage points lower than that in the previous hour.

[0015] Preferably, the atmospheric diffusion model is the HYSPLIT backward trajectory model, and the meteorological conditions include wind speed, wind direction and atmospheric stability; wherein the model simulates the diffusion path by solving the particle trajectory equation, and the particle trajectory equation is calculated based on the wind speed field, and the formula is:

[0016] ;

[0017] wherein, is the position of the particle at time , is the position and the wind velocity vector at time , is the time step, is a random displacement vector obeying a normal distribution with zero mean and variance related to the turbulent diffusion coefficient , i.e. wherein , is the turbulent diffusion coefficient; the model further incorporates the volcanic ash release source strength to calculate the spatial concentration distribution of sulfate particulate matter by a concentration distribution function based on the Gaussian diffusion principle, the formula of which is:

[0018] ;

[0019] wherein, is the concentration at point , is the source strength, is the wind velocity, and are the horizontal and vertical diffusion parameters, is the effective source height.

[0020] Preferably, in step S5, the spatial interpolation method is a Kriging interpolation method for interpolating the hourly or daily sulfate concentration data of the stations to form a continuous spatial distribution map; wherein the Kriging interpolation method is based on a variogram model, and the estimated value of an unknown point is calculated by the following formula:

[0021] ;

[0022] wherein, is the sulfate concentration value of a known point , is a weight coefficient determined by solving a Kriging equation set; the Kriging equation set is based on a variogram , the calculation formula of which is:

[0023] ;

[0024] wherein, is the distance between point pairs, is the number of point pairs with a distance of ; the weight coefficient is obtained by solving the following equation set:

[0025] ;

[0026] in, These are Lagrange multipliers, used for constrained unbiased estimation. To assess the total number of sites.

[0027] Preferably, in step S6, the specific division of the influence level is as follows:

[0028] Level 1 impact: ;

[0029] Secondary impact: ;

[0030] Level 3 impact: .

[0031] Preferably, the comprehensive influence index mentioned in step S6 The calculation formula is:

[0032] ;

[0033] in, For the first Characteristic indicators of each site For the first The weight of each site, To evaluate the total number of sites; the weights Determined based on the population density and / or intensity of economic activity in the area represented by the site.

[0034] Preferably, based on the comprehensive impact index The impact is classified into different levels for the region:

[0035] High-impact areas: ;

[0036] Moderate impact area: ;

[0037] Low impact area: .

[0038] This invention also provides an assessment system for the impact of volcanic ash on urban air quality. This system is used to implement the aforementioned assessment method for the impact of volcanic ash on urban air quality, and specifically includes the following modules:

[0039] The data acquisition module is used to acquire air quality monitoring data of the area to be evaluated before, during, and after the volcanic eruption. The data includes at least the sulfate concentration in particulate matter. Concentration and concentration;

[0040] an influence period determination module configured to automatically determine the start time and the stop time of the volcanic ash influence based on the monitoring data by a dynamic threshold condition, so as to define the accurate influence period;

[0041] an atmospheric diffusion simulation module configured to simulate the diffusion path and concentration distribution of the sulfate particles in the volcanic ash by using an atmospheric diffusion model in combination with the meteorological conditions and the volcanic ash release source intensity at the time of the volcanic eruption, so as to predict the influence range thereof on different cities or sites;

[0042] a data analysis module configured to statistically analyze the variation of the sulfate concentration at each site in the accurate influence period, compare the data before and after the volcanic eruption and at different geographical positions, and determine the direct influence degree of the volcanic eruption;

[0043] a spatial visualization module configured to cut out the data set of the affected area based on the influence range predicted by the atmospheric diffusion simulation module and the accurate influence period determined by the influence period determination module, and generate a visual geographic information map of the sulfate concentration by using a spatial interpolation method;

[0044] a comprehensive evaluation module configured to calculate the characteristic index of each evaluation site , based on the value of the characteristic index , divide the sites into different influence levels, calculate the comprehensive influence index of the region in combination with the weight of each site , and classify the region according to the comprehensive influence index .

[0045] The embodiment of the present application also provides an electronic device, which comprises a processor, a memory and a bus system, the processor and the memory are connected through the bus system, the memory is used for storing instructions, and the processor is used for executing the instructions stored in the memory to realize the evaluation method of the influence of volcanic ash on urban air quality.

[0046] The embodiment of the present application also provides a computer storage medium, which stores a computer software product, the computer software product comprises a plurality of instructions, and is used to make a computer device execute the evaluation method of the influence of volcanic ash on urban air quality.

[0047] From the above technical solutions, it can be seen that the present application has the following beneficial effects:

[0048] The present application provides an evaluation method and system of the influence of volcanic ash on urban air quality, which can evaluate the influence of the volcanic eruption period on each evaluation site of the city by using an atmospheric diffusion model, accurately obtain the influence level of the volcanic eruption on the sulfate concentration in the particulate matter of the city, and further determine the influence level of the volcanic eruption on the air quality of the city according to the sulfate concentration. The concentration ratio can quantitatively evaluate the contribution of the volcanic eruption to the sulfate concentration in the particulate matter of each urban evaluation site, so as to facilitate the relevant departments to monitor the urban areas affected by the volcanic eruption; in combination with the evaluation, the influence of the volcanic eruption on the sulfate concentration in the particulate matter of the city can be accurately obtained, the evaluation method is relatively strong in accuracy, and is relatively wide in applicability. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required to be used in the embodiments will be briefly described below. The features and advantages of the present application can be more clearly understood by referring to the drawings. The drawings are schematic and should not be understood as any limitation on the present application. For those skilled in the art, other drawings can be obtained without creative labor on the basis of these drawings. Among them:

[0050] Figure 1 is a flow chart of the evaluation method of the influence of volcanic ash on urban air quality provided by the present application;

[0051] Figure 2 is a block diagram of the evaluation system of the influence of volcanic ash on urban air quality provided by the present application. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0053] Embodiment one: in order to solve the problem that the prior art lacks the key index of sulfate concentration and cannot accurately quantify and grade the influence of the volcanic eruption on the urban air quality, as shown in Figure 1 , the present application proposes an evaluation method of the influence of volcanic ash on urban air quality. The method comprises:

[0054] Step S1: obtaining the air quality monitoring data of the region to be evaluated before, during and after the volcanic eruption, the data at least including the sulfate concentration in the particulate matter, the concentration and the concentration;

[0055] Step S2: based on the monitoring data, automatically determining the start time and stop time of the volcanic ash influence through the dynamic threshold condition, so as to define the accurate period affected;

[0056] Step S3: Using an atmospheric diffusion model, combining the meteorological conditions during the volcanic eruption and the volcanic ash release source strength, simulating the diffusion path and concentration distribution of the sulfate particles in the volcanic ash, and predicting the influence range on different cities or stations;

[0057] Step S4: Statistically analyzing the change of the sulfate concentration of each station in the accurate time period, comparing the data before and after the volcanic eruption and at different geographical positions, and determining the direct influence degree of the volcanic eruption;

[0058] Step S5: Based on the influence range predicted in step S3 and the accurate time period determined in step S2, cutting out the data set of the affected area, and using the spatial interpolation method to generate a visual geographic information map of the sulfate concentration;

[0059] Step S6: Calculating the characteristic index of each evaluation station , ; based on the value of the characteristic index , dividing the stations into different influence levels; combining the weight of each station, calculating the comprehensive influence index of the region, and classifying the region according to the comprehensive influence index .

[0060] From the above technical solution, the present application proposes an evaluation method for the influence of volcanic ash on urban air quality, which realizes accurate evaluation of the influence of volcanic eruption through six systematic steps: first, through step S1, the multi-parameter air quality monitoring data before, during and after the volcanic eruption is comprehensively obtained, providing a complete and reliable data basis for evaluation; step S2 automatically identifies the exact time period of the influence of volcanic ash based on the dynamic threshold condition, effectively excluding the interference of non-volcanic factors; step S3 uses an atmospheric diffusion model to simulate the diffusion path and concentration distribution of volcanic ash, scientifically predicting the influence range; step S4 quantifies the direct pollution degree of the volcanic eruption by statistically analyzing the temporal and spatial variation of the sulfate concentration; step S5 uses spatial interpolation technology to generate a visual geographic information map, which intuitively displays the spatial distribution characteristics of pollution; finally, through step S6, a grading evaluation system of the characteristic index and the comprehensive influence index is established, realizing the quantitative influence level division from the station to the region. The present application forms a complete technical chain from data collection, time period identification, range prediction, degree quantification to visual display and comprehensive evaluation, significantly improving the evaluation accuracy and practical value of the influence of volcanic eruption on urban air quality.

[0061] In step S1, the air quality monitoring data of the region to be evaluated before, during and after the volcanic eruption is obtained, including at least the concentration of sulfate in particulate matter, the concentration of PM10 and Concentration. In addition, the monitoring data can also include heavy metal (such as lead, mercury, cadmium, chromium) and organic matter concentration to comprehensively evaluate air quality.

[0062] Specifically, the sulfate concentration is monitored by ion chromatography;

[0063] The concentration is monitored by ultraviolet fluorescence method;

[0064] The concentration is monitored by ray method or oscillating balance method.

[0065] After data acquisition, data cleaning is required to remove errors, duplicates, missing and abnormal values to ensure data quality.

[0066] In step S2, based on the monitoring data, the start time and stop time of the volcanic ash influence are automatically determined by dynamic threshold conditions to define the accurate period affected.

[0067] Specifically, the dynamic threshold conditions include: the start time is after the volcanic eruption, the sulfate concentration in the area to be evaluated increases by 0.2 times compared with the previous hour, and the proportion in particulate matter is higher than the previous hour by 2 percentage points. The stop time: the sulfate concentration is lower than the previous hour, and the proportion in particulate matter is lower than the previous hour by 2 percentage points.

[0068] In step S3, an atmospheric diffusion model (such as HYSPLIT backward trajectory model) is used to simulate the diffusion path and concentration distribution of sulfate particles in volcanic ash, combined with the meteorological conditions (wind speed, wind direction, atmospheric stability) at the time of volcanic eruption and the source strength of volcanic ash release.

[0069] Specifically, the model simulates the diffusion path by solving the particle trajectory equation, which is calculated based on the wind speed field, and the formula is:

[0070]

[0071] where, is the position of the particle at time , is the wind speed vector of the position and time , is the time step, is a random displacement vector, which is subject to a normal distribution with a mean of zero and a variance related to the turbulent diffusion coefficient , that is, where , ​​​The model also incorporates the turbulent diffusion coefficient; it further calculates the spatial concentration distribution of sulfate particles using a concentration distribution function based on the Gaussian diffusion principle, as shown in the formula:

[0072] ;

[0073] in, For point concentration, For the source of strength, For wind speed, and For horizontal and vertical diffusion parameters, For effective source high.

[0074] In step S4, the changes in sulfate concentration at each site within a precise time period are statistically analyzed. The concentration differences at the same location before and after the volcanic eruption are compared with the concentration differences in urban areas at different distances from the eruption point to determine the degree of direct impact of the volcanic eruption.

[0075] In step S5, based on the impact range predicted in step S3 and the precise time period determined in step S2, the dataset of the affected area is cropped out, and a visual geographic information map of sulfate concentration is generated using spatial interpolation methods (such as Kriging interpolation).

[0076] Specifically, this invention utilizes Kriging interpolation to interpolate hourly or daily sulfate concentration data at stations to form a continuous spatial distribution map; wherein, Kriging interpolation is based on a variogram model, and for unknown points... The estimated value Calculated using the following formula:

[0077] ;

[0078] in, It is a known point The sulfate concentration value, These are weighting coefficients, determined by solving the Kriging equations; the Kriging equations are based on the variogram. The calculation formula is as follows:

[0079] ;

[0080] in, It is the distance between point pairs. The distance is Number of point pairs; weighting coefficients The following system of equations was solved to obtain the following:

[0081] ;

[0082] wherein, is the Lagrange multiplier used to constrain the unbiased estimate, is the total number of assessment sites.

[0083] In step S6, the characteristic index of each assessment site is calculated (sulfate concentration / SO2 concentration ratio):

[0084] .

[0085] Further, based on the value, the impact level is divided:

[0086] Primary impact (high impact): ;

[0087] Secondary impact (moderate impact): ;

[0088] Tertiary impact (low impact): .

[0089] Further, in combination with the weight of each site (based on factors such as population density, economic activity intensity, etc.), the regional comprehensive impact index is calculated:

[0090] ;

[0091] wherein, is the characteristic index of the th site, is the weight of the th site, is the total number of assessment sites; the weight is determined according to the population density and / or economic activity intensity of the region represented by the site.

[0092] Further, based on the value, the regional impact is classified:

[0093] High-impact region: ;

[0094] Moderate-impact region: ;

[0095] Low-impact region: .

[0096] Embodiment Two: As shown in the Figure 2 , the present application provides a system for assessing the impact of volcanic ash on urban air quality, which is used to implement the assessment method of the impact of volcanic ash on urban air quality in the above embodiment one, specifically comprising the following modules:

[0097] The data acquisition module 100 is configured to acquire air quality monitoring data of the to-be-evaluated region before, during and after the volcanic eruption, the data at least including the concentration of sulfate in particulate matter, the concentration of particulate matter and the concentration of sulfate.

[0098] The influence period determination module 200 is configured to automatically determine the start time and the stop time of the volcanic ash influence based on the monitoring data by means of a dynamic threshold condition, so as to define the accurate period of influence.

[0099] The atmospheric diffusion simulation module 300 is configured to simulate the diffusion path and the concentration distribution of the sulfate particulate matter in the volcanic ash by means of an atmospheric diffusion model, in combination with the meteorological conditions during the volcanic eruption and the source strength of the volcanic ash release, so as to predict the influence range thereof on different cities or sites.

[0100] The data analysis module 400 is configured to statistically analyze the variation of the sulfate concentration of each site within the accurate period, and compare the data before and after the volcanic eruption and at different geographical positions, so as to determine the direct influence degree of the volcanic eruption.

[0101] The spatial visualization module 500 is configured to cut out the data set of the influenced region based on the influence range predicted by the atmospheric diffusion simulation module 300 and the accurate period determined by the influence period determination module 200, and generate a visual geographic information map of the sulfate concentration by means of a spatial interpolation method.

[0102] The comprehensive evaluation module 600 is configured to calculate the characteristic index of each evaluation site ; divide the sites into different influence levels based on the value of the characteristic index ; calculate the comprehensive influence index of the region in combination with the weight of each site, and classify the region according to the comprehensive influence index .

[0103] The volcanic ash influence on urban air quality evaluation system of the embodiment is configured to implement the volcanic ash influence on urban air quality evaluation method described above, and thus the specific embodiments of the volcanic ash influence on urban air quality evaluation system can be seen from the foregoing embodiment part of the volcanic ash influence on urban air quality evaluation method, for example, the data acquisition module 100, the influence period determination module 200, the atmospheric diffusion simulation module 300, the data analysis module 400, the spatial visualization module 500 and the comprehensive evaluation module 600 are respectively configured to implement steps S1, S2, S3, S4, S5 and S6 of the volcanic ash influence on urban air quality evaluation method described above, and thus the specific embodiments thereof can be referred to the description of the corresponding embodiment part, and will not be described herein again in order to avoid redundancy.

[0104] Embodiment three: the embodiment of the present application provides an electronic device, the electronic device comprising a processor, a memory and a bus system, the processor and the memory being connected through the bus system, the memory being used for storing instructions, and the processor being used for executing the instructions stored in the memory to realize the method for evaluating the influence of volcanic ash on urban air quality.

[0105] Embodiment four: the embodiment of the present application provides a computer storage medium, the computer storage medium storing a computer software product, the computer software product comprising a plurality of instructions, and the instructions being used to enable a computer device to execute the method for evaluating the influence of volcanic ash on urban air quality.

[0106] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system or a computer program product. Therefore, the present application can adopt a completely hardware embodiment, a completely software embodiment or an embodiment combining software and hardware aspects. Moreover, the present application can adopt a computer program product in the form of being implemented on one or more computer usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program codes.

[0107] The present application is described with reference to flowcharts and / or block diagrams of the method, device (system) and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks. Figure 1 The means for implementing the functions specified in one or more flows and / or blocks.

[0108] These computer program instructions can also be stored in a computer readable storage medium capable of guiding the computer or other programmable data processing devices to work in a specific manner, so that the instructions stored in the computer readable storage medium produce a product including instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks. Figure 1 The means for implementing the functions specified in one or more flows and / or blocks. These computer program instructions can also be loaded to the computer or other programmable data processing devices, so that a series of operation steps are executed on the computer or other programmable devices to produce a computer implemented process, so that the instructions executed on the computer or other programmable devices provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 The functions specified in one or more flows and / or blocks.Figure 1 the steps of the functions specified in the one or more blocks.

[0109] Obviously, the above-described embodiments are only examples for the purpose of clarity and are not intended to limit the implementation. Based on the above description, other different forms of changes or variations can also be made by those of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all the implementations. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for assessing the impact of volcanic ash on urban air quality, characterized in that, The method comprises the following steps: Step S1: obtaining air quality monitoring data of the region to be evaluated before, during and after the volcanic eruption, the data at least including the concentration of sulfate in particulate matter, concentration and concentration; Step S2: determining the start time and stop time of the volcanic ash influence automatically based on the monitoring data through a dynamic threshold condition to define the accurate period affected; The dynamic threshold condition comprises: a start time is after a volcanic eruption, and a region to be evaluated The concentration of sulfate in the air is higher than that in the previous hour by 0.2 times, and the proportion in the particulate matter is higher than that in the previous hour by 2 percentage points The stop time is that the concentration of sulfate is lower than that in the previous hour, and the proportion in the particulate matter is lower than that in the previous hour by 2 percentage points The stop time is that the concentration of sulfate is lower than that in the previous hour, and the proportion in the particulate matter is lower than that in the previous hour by 2 percentage points Step S3: simulating the diffusion path and concentration distribution of the sulfate particles in the volcanic ash by using an atmospheric diffusion model, combining the meteorological conditions at the time of the volcanic eruption and the volcanic ash release source intensity, and predicting the influence range on different cities or sites; the atmospheric diffusion model is a HYSPLIT backward trajectory model, and the meteorological conditions include wind speed, wind direction and atmospheric stability; wherein the model simulates the diffusion path by solving a particle trajectory equation, and the particle trajectory equation is calculated based on the wind speed field, and the formula is: ； wherein is the position of the particle at time , is the position and time of the wind velocity vector, is the time step, is a random displacement vector, obeying a normal distribution with zero mean and variance related to the turbulent diffusion coefficient , i.e. wherein , is the turbulent diffusion coefficient; the model further incorporates a volcanic ash release source strength to calculate the spatial concentration distribution of sulfate particulate matter by a concentration distribution function based on the Gaussian diffusion principle, the formula being: ； wherein is the concentration of a point , is the source strength, is the wind speed, and are horizontal and vertical dispersion parameters, is the effective source height; Step S4: statistically analyzing the change of the sulfate concentration of each site in the accurate period, comparing the data before and after the volcanic eruption and at different geographical positions, and determining the direct influence degree of the volcanic eruption; Step S5: Based on the predicted impact range of step S3 and the accurate time period determined in step S2, the data set of the affected area is cut out, and a visual geographic information map of the sulfate concentration is generated by using a spatial interpolation method; the spatial interpolation method is a Kriging interpolation method, which is used to interpolate the hourly or daily sulfate concentration data of the site to form a continuous spatial distribution map; wherein the Kriging interpolation method is based on a variogram model, and the estimated value of the unknown point is calculated by the following formula: ​ ； wherein is the sulfate concentration value of the known point , is a weight coefficient determined by solving a Kriging equation set; the Kriging equation set is based on a variogram , the calculation formula of which is: ； wherein, is the distance between pairs of points, is the number of pairs of points at a distance of d; and the weight coefficient is obtained by solving the following system of equations: ； wherein, is a Lagrange multiplier used to constrain the unbiased estimate, is the total number of evaluation sites; Step S6: Calculate the characteristic index of each evaluation site , ; based on the value of the characteristic index , divide each site into different influence levels; combine the weight of each site to calculate the comprehensive influence index of the region , and classify the region according to the comprehensive influence index .

2. The method of assessing the impact of volcanic ash on urban air quality according to claim 1, wherein, In step S1, the air quality monitoring data further comprises heavy metal concentration and organic matter concentration in particulate matters; the sulfate concentration is monitored by ion chromatography, the concentration is monitored by ultraviolet fluorescence method, the concentration is monitored by ultraviolet fluorescence method, X-ray method or oscillating balance method.

3. The method of assessing the impact of volcanic ash on urban air quality according to claim 1, wherein, In step S6, the specific division of the influence level is: First order effects: ; Secondary effects: ; Third order effects: .

4. The method for assessing the impact of volcanic ash on urban air quality according to claim 1 or 3, characterized in that, The comprehensive influence index in step S6 The calculation formula is: ； wherein, is a characteristic index of the site, is a weight of the site, is a total number of sites evaluated; the weight is determined in accordance with the population density and / or the intensity of economic activity of the area represented by the site.

5. The method of assessing the impact of volcanic ash on urban air quality according to claim 4, wherein, based on the comprehensive influence index influence classification of the region: High impact areas: ; Moderate impact area: ; Low impact area: .

6. A system for assessing the impact of volcanic ash on urban air quality, characterized in that, The system is used to realize the method for evaluating the influence of volcanic ash on urban air quality according to any one of claims 1 to 5, and specifically comprises the following modules: A data acquisition module is configured to acquire air quality monitoring data of the to-be-evaluated area before, during and after a volcanic eruption, wherein the data at least includes concentrations of sulfate in particulate matters, and concentrations of sulfate. An influence period determination module for determining the start time and stop time of the volcanic ash influence automatically based on the monitoring data through a dynamic threshold condition to define the accurate period affected; An atmospheric diffusion simulation module for simulating the diffusion path and concentration distribution of the sulfate particles in the volcanic ash by using an atmospheric diffusion model, combining the meteorological conditions at the time of the volcanic eruption and the volcanic ash release source intensity, and predicting the influence range on different cities or sites; A data analysis module for statistically analyzing the change of the sulfate concentration of each site in the accurate period, comparing the data before and after the volcanic eruption and at different geographical positions, and determining the direct influence degree of the volcanic eruption; A spatial visualization module for cutting out the data set of the affected area based on the influence range predicted by the atmospheric diffusion simulation module and the accurate period determined by the influence period determination module, and generating a visual geographic information map of the sulfate concentration by using a spatial interpolation method; a comprehensive evaluation module for calculating characteristic indexes of each evaluation site , ; based on the values of the characteristic indexes , dividing each site into different influence levels; combining the weights of each site, calculating a comprehensive influence index of the region , and classifying the region according to the comprehensive influence index .

7. An electronic device, comprising: The electronic device comprises a processor, a memory and a bus system, the processor and the memory are connected through the bus system, the memory is used to store instructions, and the processor is used to execute the instructions stored in the memory to realize the method for evaluating the influence of volcanic ash on urban air quality according to any one of claims 1 to 5.

8. A computer storage medium, characterized in that The computer storage medium stores a computer software product, and the computer software product comprises a plurality of instructions for causing a computer device to execute the method for evaluating the influence of volcanic ash on urban air quality according to any one of claims 1 to 5.

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