CN108648127A - A kind of urban air pollution hot spot region locking means - Google Patents

Abstract

The present invention proposes a kind of urban air pollution hot spot region locking means, belongs to air pollution monitoring field.The method of the present invention includes：Step 1 is established grid to monitoring region and is numbered；Step 2 is diffused fitting, while each grid pollutant concentration value in zoning based on Gauss multiple sources air pollutants diffusion model to the air pollutants in region；Step 3 chooses the highest grid of air pollutant concentration as starting point, locks air pollution hot spot region at one；Step 4 has chosen the highest grid of grid set Air Contamination object concentration value around dot grid；Step 5, grid step 4 chosen plays dot grid as new；Step 6 has judged whether dot grid is boundary mesh, if terminating this method, if not continuing to execute step 4.The present invention can accurately lock air pollution hot spot region, can more efficiently grasp the dynamic process of the pollutant diffusion in region.

Description

A method for locking hotspots of urban air pollution

technical field

The invention belongs to the field of air pollution monitoring and relates to a method for locking hot spots of urban air pollution.

Background technique

With the continuous development of the economic level and the improvement of people's quality of life, the problem of air pollution has gradually become prominent. Air pollution seriously endangers people's health and affects the sustainable and sound development of society. In order to solve this problem, many studies have been carried out around air quality monitoring and air pollution prediction.

The traditional heavy pollution process analysis is a non-standardized method based on the experience of professionals. Different business units or scientific research units have different methods for heavy pollution process analysis. The existing technical means focus on the monitoring area Forecast of the time or intensity of heavy pollution.

Due to the lack of technical research on the use of air pollution monitoring data to lock the pollution hotspots in the region, in order to better control the air pollution problem, a method for locking the urban air pollution hotspots is needed.

Contents of the invention

The purpose of the present invention is to provide a method for locking hotspots of urban air pollution, so as to lock areas with high levels of air pollution in the city, and focus more on the spatial characteristics of heavy pollution in medium and large scale areas.

A kind of urban air pollution hotspot area locking method of the present invention, after determining the monitored area and air pollutants, then perform the following steps:

Step 1, carry out grid processing on the monitoring area, and number each grid;

In the above step 1, the monitoring area is divided into equal-area grids, and then the starting point of the lower left corner is the origin area, the right direction is the positive direction of the x-axis, the upward direction is the positive direction of the y-axis, and the x-axis and y-axis to determine the number of each grid.

Step 2, based on the Gaussian multi-point source air pollutant diffusion model, the air pollutants in the region are diffused and fitted, and the pollutant concentration values of each grid in the region are calculated;

For the grid numbered (a, b) in the monitoring area, set (x, y, z) as the center point of the pollution to be studied in the grid, and superimpose the pollution diffusion value of each pollution point source at this point, as the pollutant concentration value C _a,b of the grid.

The pollutant concentration value C _a,b is calculated according to the Gaussian multi-point source air pollutant dispersion model shown below:

Among them, N is the number of pollution sources; is the pollution value of the kth pollution point source diffused at (x, y, z); H is the sum of the height of the pollution source and the height of the plume emission upshoot; for the specific grid, the center point (x ,y,z), to study the pollution diffusion value of each pollution point source, z is set according to the actual situation;

Calculate and obtain the pollution values of all grids according to the Gaussian multi-point source air pollutant diffusion model;

Step 3. Select a grid with the highest concentration of air pollutants in the non-boundary area of the monitoring area as the starting point; and use the starting grid as an air pollution hotspot area;

Step 4, taking the air pollutant concentration values of the grids around the starting point grid as a set, comparing the air pollutant concentration values of each grid in the set, and selecting the grid with the highest air pollutant concentration in the set;

Step 5. Use the grid selected in step 4 as an air pollution hotspot area, and update the grid as the starting grid;

Step 6. Judging whether the newly determined starting grid is the grid of the regional boundary, if it is to output all air pollution hotspot areas, end this method; if not, continue to step 4 for execution. Compared with the prior art, the present invention has the following obvious advantages:

(1) The present invention fits the air pollution situation in various places in the area, and more effectively grasps the dynamic process of pollutant diffusion in the area;

(2) The present invention relies on the support of air pollution diffusion theory, which improves the accuracy of air pollution hotspot area locking;

(3) The present invention effectively locks the air pollution hot spots in the area.

Description of drawings

Fig. 1 is the overall flow diagram of the urban air pollution hotspot area locking method of the present invention;

FIG. 2 is an effect diagram of monitoring area network processing in an embodiment of the present invention;

Fig. 3 is an effect diagram of the grid where the starting point of the region is located in the embodiment of the present invention;

Fig. 4 is an effect diagram of comparing the concentration values around the grid where the starting point is located in the embodiment of the present invention;

Fig. 5 is an effect diagram of updating the starting point position in the embodiment of the present invention;

Fig. 6 is an effect diagram of updating an air pollution hotspot area in an embodiment of the present invention;

Fig. 7 is an effect diagram utilizing the method of the present invention to locate air pollution hotspots;

Fig. 8 is an effect diagram of the actual application of the present invention to lock air pollution hot spots.

Detailed ways

In order to facilitate those of ordinary skill in the art to understand and implement the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

Aiming at the field of air pollution monitoring, the present invention proposes a method for locking hot spots of urban air pollution. The overall process is shown in FIG. 1 , and each implementation process is described below.

The first step is to identify the area to be studied and the air pollutants to be studied. According to the layout area of urban air monitoring points, determine the area range that can be monitored in real time, and according to the Gaussian diffusion model that can fit the range reasonably and scientifically, determine the area to be studied. Common air pollutants in cities are nitrogen dioxide (NO ₂ ), sulfur dioxide (SO ₂ ), carbon monoxide (CO), ozone (O ₃ ), PM _2.5 , PM ₁₀ and so on.

Step 1, network the monitoring area and number each grid.

According to the size of the monitoring area, regional functions, natural conditions and other characteristics, it is divided into several equal-area grids for further analysis and research. As shown in Figure 2, the starting point of the lower left corner is taken as the origin area, the positive direction of the x-axis is taken to the right, and the positive direction of the y-axis is taken upwards, and the coordinate numbers of each grid are determined by the coordinate values of the x-axis and y-axis. As shown in Figure 2, after the area to be monitored is divided into grids, let (a, b) represent the coordinates of the grid, where a and b are integers, and 1≤a≤m, 1≤b≤n, so that The area to be monitored can be represented by a matrix, m×n is the total number of grids, and both m and n are positive integers. Let C _{a, b} denote the pollutant concentration value of the grid (a, b), as shown in Figure 2, the pollutant concentration value of each grid needs to be calculated according to step 2 below.

Step 2. Based on the Gaussian multi-point source air pollutant diffusion model, the air pollutants in the region are diffused and fitted, and the pollutant concentration values of each grid in the region are calculated.

Gaussian plume model, referred to as Gaussian model, is a common model for calculating the three-dimensional spatial distribution of pollutants after reaching a steady state for air pollution sources.

The Gaussian diffusion model of air pollution is a diffusion model under the assumption of normal distribution obtained by applying turbulence statistics theory. Take the projection of the pollutant point source on the ground as the coordinate origin, take the direction pointing downwind from the origin as the x-axis, and take the pollutant concentration ρ _C (x,y,z, H) is the solution object, then the Gaussian pollution diffusion equation is:

Wherein: _ρC is the pollutant concentration at any point (x, y, z), and the unit is mg/m ³ ;

H is the sum of the height of the pollution source and the height of the plume discharge;

α is the ground reflection coefficient of the particle;

q _m is the emission intensity of the pollution source, that is, the amount of pollutant emission per unit time;

v is the average wind speed in m/s;

σ _y and σ _z are the diffusion coefficients in the y direction and z direction, which are related to the atmospheric stability and the horizontal distance x, and increase with the increase of x;

v _t is the gravitational settling velocity of particles, the unit is m/s, and its calculation formula is:

Where: d _p is particle diameter; ρ _p is particle density; μ is air viscosity; g is gravitational acceleration.

When H = 0, the pollution source is called a ground point source. When H≠0, the pollution source is called an elevated point source. Typically, the value of H includes the height of the chimney plus the height of the exhaust overshoot.

In addition, when the particle size of the particle is less than 15 μm in the formula, the ground reflection and the gravity sedimentation velocity of the particle are not considered, and at this time α=0 and v _t =0. When the particle size of the particles is greater than 15 μm, the settling effect of gravity must be considered.

When there are multiple pollution sources in the area, the pollutant concentration values of each grid in the area are calculated based on the Gaussian model. The basic principle of multi-point source air pollution diffusion Gaussian model:

Based on the Gaussian model of air pollution diffusion, the pollution source and calculation area are mainly considered in the calculation. Under the action of the wind field, the pollution area usually considers a certain range of three-dimensional space in the downwind direction of the pollution source. In the actual calculation, multiple air pollution sources in the study area are used for diffusion fitting. Pollution calculation is to determine the pollutant concentration value of a grid center point based on the pollution effect of the pollution source on the grid center point. The result of combining the calculated pollutant concentration values in each grid is the final pollutant concentration value in the grid.

For a grid (a, b), let (x, y, z) be the center point of the pollution to be studied, and then calculate according to the Gaussian multi-point source air pollutant diffusion model shown below:

Among them, N is the number of pollution sources; C _{a, b} are the superimposed values of pollutant concentration values produced by multiple point sources in the grid, which are obtained by the independent diffusion of N pollution sources get superimposed. is the pollution value of the kth pollution point source diffusion at the grid center (x, y, z), calculated according to the Gaussian pollution diffusion equation above.

For a specific grid, the center point (x, y, z) can be determined according to the actual research situation, and the pollution diffusion value of each pollution point source at this place is studied, and z is set according to the actual situation. According to the Gaussian multi-point source air pollutant diffusion model above, the pollution values of all m×n grids are obtained.

Step 3, select the grid with the highest concentration of air pollutants in the non-boundary area of the monitoring area as the starting point, in Figure 2, the grid where C _a,b (1<a<m, 1<b<n) is located All belong to the non-boundary area.

Step 4, select the grid where the starting point is located as an air pollution hotspot area. For example, if the grid determined at (2,2) in the area shown in Figure 3 is the starting position, then the grid is an air pollution hotspot area.

Step 5, take the air pollutant concentration values of the grids around the starting point as a set, compare the air pollutant concentration values of each grid in the set, and select the grid with the highest air pollutant concentration in the set.

For example, as shown in Figure 4, the grid where the starting position C _2,2 is located is an air pollution hotspot area, and the concentration value set around it is [C _1,1 ,C _2,1 ,C _3,1 ,C _1,2 ,C _3,2 ,C _1,3 ,C _2,3 ,C _3,3 ]; select the highest value of air pollutant concentration in this set, namely max[C _1,1 ,C _2,1 ,C _3,1 ,C _1,2 ,C _3,2 ,C _1,3 ,C _2,3 ,C _3,3 ], determine the grid where the air pollutant concentration value is located.

Step 6, the grid with the highest concentration of air pollutants in the set determined in the above steps is used as an air pollution hotspot area, and the air pollution hotspot area is updated.

For example, as shown in Figure 5, the set of concentration values around [C _1,1 ,C _2,1 ,C _3,1 ,C _1,2 ,C _3,2 ,C _1,3 ,C _2,3 , In C _3,3 ], the highest air pollutant concentration value is C _3,3 , then the grid where the air pollution concentration value C _3,3 is located is an air pollution hotspot area, and the air pollution hotspot area is updated.

Step 7, update the starting position, and use the grid with the highest air pollutant concentration obtained in step 6 as the starting position.

For example, as shown in Figure 5, the grid where C _3,3 is located is taken as the starting position.

Step 8, judge whether the newly determined starting grid is the grid of the area boundary, if the grid is not the grid of the area boundary, then go to step 5, and use the concentration value of the grid around the starting grid position as a A new set, the new set does not include the concentration values of the grids that have been compared, and the grid with the highest concentration in this set is selected to update the air pollution hotspot area.

For example, as shown in Figure 6, the starting grid position is the grid where C _3,3 is located, and the concentration values of the surrounding grids are used as a new set [C _4,2 , C _4,3 , C _{2, 4} , C _3,4 , C _4,4 ], this set does not include the concentration values of the grids that have been compared, and the grid with the highest concentration in this set is selected to update the air pollution hotspot area.

If the updated starting grid in step 8 is the grid of the regional boundary, output the final air pollution hotspot area. For example, as shown in Figure 7, when the starting point grid is the grid where the area boundary grid C ₅ , 5 is located, the update of the air pollution hotspot area is stopped, and the air pollution hotspot area is output. The grid area where the labels ①②③④⑤ are located in the figure is the final output air pollution hotspot area.

The calculation effect presented by the method of the present invention in practical application is shown in FIG. 8 . Using the multi-point source air pollution Gaussian diffusion model to realize the fitting value of the pollutant concentration in the region when there are multiple pollution sources in the region, and can lock out "one" pollution by comparing the concentration values of each point Hotspot area "bands" thereby identifying pollution hotspots. The method of the invention can more accurately lock the air pollution hotspot area, and can more effectively grasp the dynamic process of pollutant diffusion in the area.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. It should be pointed out that for those skilled in the art, some improvements and deformations can be made without departing from the technical principle of the present invention. These improvements and deformations should also be regarded as the protection scope of the present invention.

Claims (3)

1. A method for locking hotspots of urban air pollution, after determining the monitoring area and air pollutants, it is characterized in that, then perform the following steps: Step 1, carry out grid processing on the monitoring area, and number each grid; Step 2, based on the Gaussian multi-point source air pollutant diffusion model, the air pollutants in the region are diffused and fitted, and the pollutant concentration values of each grid in the region are calculated; For the grid numbered (a, b) in the monitoring area, set (x, y, z) as the center point of the pollution to be studied in the grid, and superimpose the pollution diffusion value of each pollution point source at this point, As the pollutant concentration value C _a,b of the grid; The pollutant concentration value C _a,b is calculated according to the Gaussian multi-point source air pollutant dispersion model shown below: Among them, N is the number of pollution sources; is the pollution value of the k-th pollution point source diffused at (x, y, z); H is the sum of the height of the pollution source and the height of the plume emission; Calculate and obtain the pollution values of all grids according to the Gaussian multi-point source air pollutant diffusion model; Step 3, select a grid with the highest concentration of air pollutants in the non-boundary area of the monitoring area as the starting point, and use the starting grid as an air pollution hotspot area; Step 4, taking the air pollutant concentration values of the grids around the starting point grid as a set, comparing the air pollutant concentration values of each grid in the set, and selecting the grid with the highest air pollutant concentration in the set; Step 5, use the grid selected in step 4 as an air pollution hotspot area, and update the grid as the starting grid; Step 6, judge whether the newly determined starting grid is the grid of the regional boundary, if it is to output all air pollution hot spots, end this method; if not, go to step 4 for execution. 2. The urban air pollution hotspot area locking method according to claim 1, characterized in that, in the step 1, the monitoring area is divided into equal-area grids, and then the starting point in the lower left corner is the origin area, to The right is the positive direction of the x-axis, the upward is the positive direction of the y-axis, and the number of each grid is determined by the coordinate values of the x-axis and y-axis. 3. the urban air pollution hotspot area locking method according to claim 1, is characterized in that, in described step 2, the Gaussian pollution diffusion of a pollution point source is: the projection of the pollution point source on the ground is the coordinate origin, The direction pointing downwind from the origin is the x-axis, then the pollutant concentration ρ _C (x,y,z,H) at any point (x,y,z) downwind of the point source is: Among them: α is the ground reflection coefficient of particles; q _m is the emission intensity of pollution sources; v is the average wind speed; σ _y and σ _z are the diffusion coefficients in the y direction and z direction; v _t is the gravity sedimentation velocity of particles, and the calculation formula is : Where: d _p is particle diameter; ρ _p is particle density; μ is air viscosity; g is gravitational acceleration.