CN115034035A - Multi-pollutant cross-boundary transmission flux quantification integration technology and transmission channel identification method - Google Patents

Abstract

The invention discloses a multi-pollutant transboundary transmission flux quantification integration technology and a transmission channel identification method; the invention adopts the method of mutual verification of stereoscopic observation and model simulation, aiming at different situations (fixed point, navigation, cross-border, etc.) Quantitatively reveal the transboundary transmission law of various air pollutants, and realize the direct comparison and verification of quantitative transmission simulation and observation results; further, based on the quantitative results of transboundary transmission flux of air pollutants, identify the main transmission channels of air pollution in the target area. The beneficial effect of the present invention lies in that it can quantitatively reveal the law of cross-border transmission of pollution between cities, districts and counties, and solve the problem of air pollution responsibility division.

Description

Multi-pollutant transboundary transmission flux quantification integration technology and transmission channel identification method

technical field

The invention relates to the technical fields of stereoscopic observation, model simulation, quantitative calculation of the transboundary transmission flux of various pollutants, identification of air pollution transmission channels, etc., and more specifically, relates to the multi-pollutant transboundary transmission flux quantification integration technology and transmission Channel identification method.

Background technique

In recent years, atmospheric environmental pollution as a whole has shown a composite characteristic of "multiple pollution problems coexisting, multiple pollution sources superimposed, multi-scale correlation, multi-process coupling, and multi-media influence". The regional complex air pollution problem characterized by PM _2.5 and O ₃ pollution has become increasingly prominent, which has attracted extensive attention of domestic and foreign researchers. Under the influence of atmospheric circulation, PM _2.5 has a long transmission distance, a wide range of influence, and significant cross-border transport characteristics, which will lead to heavy pollution phenomena such as increased PM _2.5 concentration in contiguous areas, frequent occurrence of haze and photochemical pollution, and adversely affect the quality of the atmospheric environment. and visibility, climate change, human health and national economic development pose a great threat. A number of studies have shown that the current urban air pollution has the characteristics of multi-scale complex pollution, that is, small-scale and local pollution is first caused by the emission of a single pollution source, and then it evolves through the city’s point, line, and surface mixing, pollution diffusion and chemical transformation processes. Urban-scale pollution; under a specific geographical environment and a certain atmospheric circulation background, it will affect other regions through medium- and long-distance transportation such as across cities, provinces, and regions, and eventually evolve into regional composite pollution. Therefore, how to solve the problem of cross-border transportation of air pollutants between cities, provinces and regions, and quantitatively identify the law of cross-border transmission of pollutants, is an effective way to improve regional air quality and achieve joint prevention and control of regional air pollution. top priority.

At present, the technical methods widely used in the research of spatial source analysis of pollutants are mainly divided into the following categories: backward trajectory model, atmospheric pollution observation and mathematical statistics method, air quality model method, etc. The backward trajectory model (HYSPLIT-4) can more completely simulate the transport, diffusion and deposition processes of various pollutants, and is widely used in the research of air pollution transport. However, the backward trajectory model does not consider the chemical reaction process of pollutants during the transport process, and the estimation of the transport distance has obvious deviations when the simulated trajectory runs, and cannot quantitatively identify the transport contribution of different regions to the target region. Potential Source Contribution Factor (PSCF) and Concentration Trajectory Weighting (CWT) require long-term continuous observations, observation sites cannot represent the entire city or region, and the set thresholds are obviously subjective. Using various pollutant monitoring equipment to carry out spatial three-dimensional real-time online observation of regional multi-scale atmospheric pollutants, and use the observation data to obtain the spatial distribution and transmission paths of pollutants, which can effectively identify the law and the mutual transmission of pollutants between different regions. feature. Commonly used observation equipment includes lidar stereo observation, lidar navigation observation, multi-axis differential absorption spectroscopy online monitoring system (MAX-DOAS) and so on. The air quality model method comprehensively uses the air pollution source emission inventory data and the simulated meteorological background field data, and uses the three-dimensional numerical method to simulate the transportation, chemical transformation, diffusion and deposition of air pollutants such as gases and aerosols in the atmosphere. Estimating the contribution of different regional pollution sources and multiple emission sources to the concentration of various pollutants at the receptor site is one of the most widely used and important methods for domestic and foreign scholars to study multi-scale pollution transmission problems. At present, the mainstream air quality models include CMAQ, CAMx, WRF-Chem, NAQPMS, etc. Based on the above models, the pollution contributions of different source regions to receptor sites and recipient cities can be simulated and obtained, and the cross-regional, Transmission contribution matrix across cities. However, for the transportation of various pollutants between adjacent areas with different heights in the vertical direction, between adjacent cities and cities, between adjacent districts and counties, and between adjacent roads and roads, how to Quantitative calculation of the transboundary transport volume of adjacent boundaries still needs to be further studied. At the same time, the current transmission contribution matrix of various pollutants (such as atmospheric particulate matter with aerodynamic equivalent diameter less than or equal to 2.5μm PM _2.5 , O ₃ , etc.) obtained by the model can quantitatively simulate and analyze a certain city or a certain area. Contribution to pollution transmission at a receptor site, a city, or a region. However, the model simulation has certain uncertainty, and there will be a certain deviation from the actual observation value. Most of the current transmission quantification methods are to verify the simulated pollutant concentration, which indirectly proves the accuracy of the pollution transmission quantification results obtained by the simulation; However, it is not possible to directly verify the transmission simulation data by transmitting the monitoring data. Moreover, the technical method for identifying pollution transmission channels based on the transboundary transmission flux of pollutants is not yet mature.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the purpose of the present invention is to provide a multi-pollutant transboundary transmission flux quantification integration technology and a transmission channel identification method, which are useful for solving adjacent areas, adjacent cities, adjacent districts and counties, adjacent For the problem of cross-border transportation between roads, it is of great significance to accurately reveal the quantitative law of cross-border transportation of air pollutants. At the same time, it can also provide scientific and technological support for solving the problems of mutual transmission and responsibility division of air pollution between adjacent cities.

The technical solutions of the present invention are specifically introduced as follows.

The invention provides a multi-pollutant transboundary transmission flux quantification integration technology method based on the mutual verification of observation and simulation, which obtains the fixed-point transmission flux observation value and Then, by analyzing the accuracy of the verification of the simulation results, adjust the model parameters to optimize the WRF-CAMx three-dimensional numerical model to improve the accuracy of the model simulation; among which:

When laser radar fixed-point observation obtains fixed-point transmission flux observations of pollutants, it is based on laser radar and wind profiler for online observation, and combines the three-dimensional distribution structure of atmospheric pollutant mass concentration obtained by the two devices with the three-dimensional wind field data. , the vertical distribution of the air pollutant transmission flux at different heights of the observation site is obtained; the observed value of the fixed point transmission flux is the product of the monitoring mass concentration of air pollutants and the wind vector;

When the WRF-CAMx three-dimensional numerical model is used to obtain the simulated value of fixed-point transmission flux, since the mode belongs to the Euler three-dimensional grid mode, the target area is regarded as a three-dimensional box composed of multiple grids, and each grid has a fixed The three-dimensional spatial coordinates of the grid provide the meteorological elements and atmospheric pollutant concentrations of each grid in the study area. The WRF and CAMx are set to the same vertical layer number and delta coordinate parameter, where the delta coordinate parameter is a coordinate parameter defined in the WRF meteorological model to set the height of each vertical layer in the vertical direction. , its value range is [0-1]. According to the set δ coordinate parameters, the WRF meteorological model automatically sets the height of each vertical layer; the fixed-point transmission flux simulation value is the product of the simulated mass concentration of pollutants and the simulated wind vector. , where the simulated mass concentration of pollutants is obtained by simulating the CAMx air quality model, and the simulated wind vector, including wind direction and wind speed, is obtained by simulating the WRF meteorological model.

In the present invention, the observation value and simulation value of the pollutant's navigation transmission flux are obtained based on the laser radar navigation observation and the WRF-CAMx three-dimensional numerical model simulation, and then the model parameters are adjusted by analyzing the accuracy of the simulation result verification. To optimize the WRF-CAMx 3D numerical model to improve model simulation accuracy; where:

When lidar travel observation is used to obtain the observation value of the travel transmission flux of pollutants, it is based on the three-dimensional distribution results of the air pollutant mass concentration obtained by the closed-loop travel observation obtained by the lidar, combined with the three-dimensional wind field information and the azimuth angle of the vehicle. The included angle of the wind direction, that is, the vertical distribution of the air pollutant transmission flux at different heights above the ground on the closed-loop monitoring path; the calculation formula of the observation value of the navigation transmission flux is as follows:

Flux(z) ₌ CP(z)×V(z)×sinθ

where:

Flux(z)——transmission flux of atmospheric pollutants at height z above ground, unit: μg·m ^-2 ·s ^-1 ;

C _P (z)——mass concentration of air pollutants at height z above ground, unit: μg·m ^-2 ·s ^-1 ;

V(z)——The observed wind speed at the height z above the ground, unit: m/s;

sinθ——the angle between the vehicle's azimuth and the wind direction recorded by GPS;

When calculating the simulated value of the navigation transmission flux, the specific points concerned in the navigation observation and the simulated value of the specific grid point flux simulated by the WRF-CAMx model are used for comparison and verification, that is, the simulated value of the navigation transmission flux here. is the product of the simulated concentration of the pollutant and the simulated wind vector.

In the present invention, the observation value and the simulated value of the transboundary transmission flux of the pollutant are obtained respectively based on the observation of high-altitude meteorology-near-ground pollutants and the simulation of the WRF-CAMx three-dimensional numerical model, and then the accuracy of the verification of the simulation results is analyzed, Adjust model parameters to optimize WRF-CAMx 3D numerical model to improve model simulation accuracy;

When calculating the air pollutants in the target area and the transboundary transmission flux observations in the surrounding areas, the air pollutant monitoring concentrations and wind vector observations in the target area and surrounding areas are considered; for air pollutant monitoring concentrations, Through the hypothetical method, the point is used to represent the surface. It is assumed that the concentration of air pollutants near the ground obtained through the monitoring of the conventional air pollutant monitoring equipment in the target area at the target area represents the concentration of air pollutants in the entire target area, and the pollution in the vertical direction The concentration distribution is uniform, and the concentration of air pollutants near the ground in adjacent areas is downloaded from the air quality website, which is also used as the overall concentration of each adjacent area, and the concentration distribution in the vertical direction is uniform; for wind vector observations, it is assumed that the target The wind vector at the border between the area and each adjacent area is consistent, that is to say, the wind speed and wind direction of the target area and each adjacent area are based on the wind speed and wind direction values obtained by the wind profiler set up in the target area; On this basis, the observed value of transboundary transmission flux between the target area and each adjacent area is calculated; the calculation formula of the observed value of transboundary transmission flux is as follows:

Flux _u = Σ _h L · H _k · c _up · u · 8.64×10 ^-8

Flux _v = Σ _h L · H _k · c _up · v · 8.64×10 ^-8

In the formula: Flux _u - the transmission flux of pollutants in the east-west direction, unit: t/d;

Flux _v ——the transmission flux of pollutants in the north-south direction, unit: t/d;

h——the vertical highest level observed by the wind profiler, unit: m;

L——the length of the boundary line of the contact between two adjacent areas, unit: m;

H _k ——height resolution of the wind profiler in the vertical direction, unit: m;

C _{up ——mass} concentration of air pollutants in the upwind city, unit: μg/m ³ ;

u——wind speed in the east-west direction, unit: m/s;

v——wind speed in north-south direction, unit: m/s.

The method of simulating the transboundary transmission flux of various air pollutants based on the WRF-CAMx three-dimensional numerical model is as follows: First, select the target area, divide the boundary of air pollution transboundary transmission according to the method of administrative boundary line, and determine each phase bordering the target area. In neighboring areas, the simulation range is divided into different grids through grid division in the model, which is used to simulate and calculate the transboundary transmission flux of air pollutant pollution;

The target area is regarded as a three-dimensional box composed of multiple grids, a vertical section in the box is selected, the flow velocity of each micro-element on the section, the concentration of air pollutants and the quantitative product of the area are calculated, and then the entire section is calculated. Integrate to obtain the mass of air pollutants passing through the entire section per unit time;

The WRF-CAMx mode belongs to the Euler three-dimensional grid mode, each grid has fixed three-dimensional spatial coordinates, and provides the meteorological elements and atmospheric pollutant concentrations of each grid in the study area; in addition, the WRF and CAMx are set to the same vertical The number of layers and δ coordinate parameters are used to obtain the wind direction, wind speed and atmospheric pollutant concentration information corresponding to the same height above the ground for each grid. In summary, the calculation section will be calculated according to the grid division methods in the WRF and CAMx modes. For discretization, the output data of the two models are used to calculate the transboundary transport flux of air pollutants on a specific section. The specific calculation formula is as follows:

Where: Flux——transboundary flux of atmospheric pollutants, unit: t/d;

h——the vertical highest level set by the model, unit: m;

l——Boundary line of two adjacent areas, unit: m;

L——simulation grid resolution, unit: km;

H _{k ——the} height difference between the simulated vertical layer k and k+1;

c——mass concentration of air pollutants, unit: μg/m ³ ;

v——wind direction and wind speed, unit: ° and m/s;

n——the normal vector passing through the vertical section, dimensionless;

Based on the calculation formula of cross-boundary transmission flux, the inflow of air pollutants into the target area is positive, and the outflow of the target area is negative. From a single box, multiple boxes at the same ground height at the boundary line to all boxes in the vertical direction, Calculate the inflow and outflow fluxes of air pollutants at different heights above the ground; the net flux refers to the vector sum of the inflow and outflow fluxes of air pollutants, where positive values represent net inflow fluxes, and negative values represent net outflow fluxes quantity.

In the present invention, in the WRF-CAMx three-dimensional numerical model, the vertical layers of WRF and CAMx are both set to 28 layers.

In the present invention, by introducing the correlation coefficient COR, the standardized average deviation NMB and the standardized average error NME statistical index, the observation value of the pollutant transmission flux and the simulated value are compared and verified, and the accuracy of the verification of the simulation result is analyzed.

The present invention also provides a method for identifying a pollution transmission channel based on the transboundary transmission flux of pollutants, comprising the following steps:

Based on the optimized WRF-CAMx three-dimensional numerical model, the inflow, outflow and net fluxes of air pollutants between each city in the study area and its surrounding areas are simulated. According to the inflow and outflow of air pollutants in each target city The inflow and outflow directions of all cities in the target area are sorted out and integrated, so as to obtain the overall inflow and outflow directions of air pollutants in the area, and then identify the transmission channels in the target area.

Compared with the prior art, the beneficial effects of the present invention are:

(1) Through the two technical methods of stereoscopic observation and model simulation, facing the quantitative problem of cross-border transmission of various pollutants in different situations (fixed-point, navigation, and cross-border), it can accurately reveal the fixed-point transmission flux, the navigation transmission flux Quantitative law of flux and transboundary transmission flux, identify the evolution characteristics of inflow flux, outflow flux and net flux among regions, cities, districts and counties, townships/streets, and solve multi-scale (regional, urban, township/street) ) the problem of division of responsibility for air pollution.

(2) Using the method of mutual verification between stereo observation and model simulation, the fixed-point transmission flux, navigation transmission flux and cross-boundary transmission flux obtained by observation were compared and verified with the simulated values of the corresponding transmission flux. To verify the accuracy of the simulation, it only depends on the limitations of the verification of meteorological parameters and pollutant concentration parameters, which realizes the direct comparison and analysis of the simulation results of the transmission quantification and the observation results, and determines the simulation error range; on the other hand, the comparison and verification results can also be used. The model is optimized and verified, and the purpose of improving the accuracy of the model simulation is achieved by adjusting the model simulation parameters, optimizing the simulation scheme, and improving the emission inventory of air pollution sources.

(3) Based on the quantitative simulation of the transboundary transmission flux of various air pollutants, identify the inflow, outflow and net fluxes of various air pollutants in the target area for each transboundary, and then determine the various air pollutants in the target area. It is the main transmission channel of air pollutants, and provides effective scientific and technological support for regional joint prevention and control and emergency treatment of heavy pollution.

Description of drawings

Figure 1 is an example of a three-dimensional box.

Figure 2 shows the comparison between the simulated and observed values of PM _2.5 transmission flux.

Figure 3 shows the vertical distribution of the selection of key points of voyage observation flux and PM _2.5 observation flux.

Fig. 4 shows the vertical distribution of the simulated flux of PM _2.5 traveling in Beijing Sixth Ring Road.

FIG. 5 is a schematic diagram of boundary line identification between adjacent regions.

Figure 6 is a schematic diagram of a unit area micro-element vector.

Figure 7 is a schematic diagram of the inflow and outflow fluxes of atmospheric pollutants in the vertical section of a single box.

FIG. 8 is a schematic diagram of a vertical cross-section at the boundary line of the adjacent regions after discretization.

Figure 9 shows the geographical distribution of Shunyi District and its surrounding adjacent districts/cities.

Figure 10 shows the vertical distribution of simulated and observed PM _2.5 net fluxes in Shunyi and surrounding counties in different seasons.

Figure 11 shows the main transmission channels of PM _2.5 pollution in the Beijing-Tianjin-Hebei region.

Detailed ways

The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

The present invention establishes a multi-pollutant transboundary transmission flux quantification integration technology and a transmission channel identification method based on the WRF- _CAMx model. In addition to the Beijing-Tianjin-Hebei region and PM _2.5 pollutants, this method is also applicable to any other region and other atmospheric pollutants (such as O ₃ , atmospheric particulate matter with aerodynamic equivalent diameter less than or equal to 10 μm PM ₁₀ , CO, SO _{2 )} , nitrogen oxides NOx and volatile organic compounds VOCs, etc.).

The present invention is based on meteorological radar observation, lidar stereoscopic observation, meteorological and air quality model (WRF-CAMx) and other technical means, aiming at the cross-border transmission of multiple pollutants in different situations, and introduces correlation coefficient (COR), standardized average deviation Three statistical indicators, such as (NMB) and normalized mean error (NME), were used to compare and verify the simulated value and the observed value, aiming to provide a quantitative integration technology of multi-pollutant transboundary transmission flux and a transmission channel identification method. Among them, many cases include three cases, the details are as follows: Case 1: The fixed-point transmission flux calculation method based on the mutual verification of lidar fixed-point observation and model simulation. Scenario 2: The calculation method of the navigation transmission flux based on the mutual verification of the Lidar navigation observation and the model simulation. Scenario 3: Based on the cross-boundary transport flux calculation method based on the mutual confirmation of upper-air meteorological-pollutant observations and model simulations.

The WRF-CAMx model refers to the coupled three-dimensional numerical model constructed by the meteorological model WRF and the air quality model CAMx. The meteorological model WRF can provide the simulated values of wind vectors (wind direction and wind speed), and the air quality model CAMx can provide the simulation values of various air pollutants. concentration. Since the above two models are both three-dimensional numerical models, the wind vectors and atmospheric pollutant concentration values at different heights in the vertical direction of the gridded target area can be simulated. In order to obtain the wind direction, wind speed and concentration information of atmospheric pollutants corresponding to the same height above the ground of each grid, and to facilitate the comparison and verification with the stereoscopic observation data of transmission flux, the WRF and CAMx are set to the same vertical layer number (28 layers). ) and δ coordinate parameters, where the number of vertical layers refers to dividing the vertical direction into different layers, and each vertical layer corresponds to a different height. And a defined coordinate parameter, its value range is [0-1], according to the set delta coordinate parameter, the WRF meteorological model can automatically set the height of each vertical layer.

In order to evaluate the accuracy of the simulation results of PM _2.5 transboundary transmission flux obtained based on the model, this patent introduces 3 statistical indicators such as correlation coefficient (COR), normalized mean deviation (NMB) and normalized mean error (NME). as follows:

where Sim _(i) and Obs _(i) represent the simulated and observed values of transboundary transmission fluxes (including inflow, outflow, and net flux), respectively, and n represents the number of samples.

Case 1: The fixed-point transmission flux calculation method based on the mutual verification of lidar fixed-point observation and model simulation.

The fixed-point transmission flux refers to the mass of air pollutants passing through a unit area per unit time.

in,

(1) The principle of laser radar fixed-point observation to obtain pollutant transmission flux is based on the online observation of laser radar and wind profiler. The vertical distribution of the transport flux of atmospheric pollutants at different heights of the observation site can be obtained. The calculation formula is the product of pollutant concentration and wind speed, namely:

FLUX _NSh =C _ph ×V _NSh

FLUX _EWh =C _ph ×V _EWh

where:

FLUX _{NSh ——The} observed value of the fixed-point transmission flux of air pollutants at a height of h meters above the ground in the north-south direction, the unit is μg·m ^-2 ·s ^-1 ; when FLUX _NSh is a positive value, it is defined as the air pollutants from the south Input to the north, when FLUX _NSh is negative, it is defined as the output of air pollutants from north to south;

FLUX _{EWh ——the} observed value of the fixed-point transmission flux of air pollutants at a height of h meters above the ground in the east-west direction, the unit is μg·m ^-2 ·s ^-1 ; when FLUX _EWh is a positive value, it is defined as the air pollutants from the west East input, when FLUX _EWh is negative, it is defined as the output of air pollutants from east to west;

C _Ph - the monitored mass concentration of air pollutants (such as O ₃ , PM _2.5 , etc.) at a height of h meters above the ground, in μg/m ³ ;

V _{NSh ——The} observed value of the wind vector in the north-south direction at the height of h meters above the ground, the unit is m/s. When V _NSh is a positive value, it means that the wind direction is south wind, and when V _NSh is a negative value, it means that the wind direction is north wind.

V _{EWh ——The} observed value of the wind vector in the east-west direction at a height of h meters above the ground, the unit is m/s. When V _EWh is a positive value, it means that the wind direction is west wind, and when V _EWh is a negative value, it means that the wind direction is east wind .

(2) The principle of WRF-CAMx 3D numerical model simulation to obtain fixed-point transmission flux is that the model belongs to the Euler 3D grid mode, and the target area can be regarded as a 3D box composed of multiple grids (Figure 1). Each grid has fixed three-dimensional spatial coordinates, which can provide the meteorological elements and atmospheric pollutant concentrations of each grid in the study area. In order to obtain the wind direction, wind speed and concentration information of atmospheric pollutants corresponding to the same height above the ground of each grid, and to facilitate the comparison and verification with the stereoscopic observation data of transmission flux, the WRF and CAMx are set to the same vertical layer number (28 layers). ) and delta parameters, the delta coordinates corresponding to each layer are 1.000, 0.994, 0.988, 0.981, 0.969, 0.956, 0.944, 0.926, 0.902, 0.881, 0.852, 0.828, 0.796, 0.754, 0.704, 0.648, 0.589, 0.546, 0.495, 0.445, 0.387, 0.287, 0.187, 0.136, 0.091, 0.061, 0.020, 0.000. Table 1 gives the height corresponding to each delta coordinate in the vertical direction.

Table 1 Each δ coordinate and corresponding height in the vertical direction

The calculation formula is the product of the simulated concentration of pollutants and the simulated wind speed, namely:

FLUX' _NSh =C' _ph ×v _h

FLUX' _EWh = C' _ph ×u _h

where:

FLUX' _{NSh ——The} simulated value of the fixed-point transmission flux of air pollutants at a height of h meters above the ground in the north-south direction, the unit is μg·m ^-2 ·s ^-1 ; when FLUX' _NSh is a positive value, it is defined as air pollutants Input from south to north, when FLUX' _NSh is negative, it is defined as the output of air pollutants from north to south;

FLUX' _{EWh ——The} fixed-point transmission flux simulation value of air pollutants at a height of h meters above the ground in the east-west direction, the unit is μg·m ^-2 ·s ^-1 ; when FLUX' _EWh is a positive value, it is defined as air pollutants Input from west to east, when FLUX' _EWh is negative, it is defined as the output of air pollutants from east to west;

C' _Ph — the simulated mass concentration of air pollutants (such as O ₃ , PM _2.5 , etc.) at a height of h meters above the ground, in μg/m ³ ;

V _h ——The simulated value of wind vector in the north-south direction at the height of h meters above the ground, the unit is m/s. When V _h is a positive value, it means that the wind direction is south wind, and when V _h is a negative value, it means that the wind direction is north wind.

u _h ——The simulated value of the wind vector in the east-west direction at a height of h meters above the ground, the unit is m/s. When u _h is a positive value, it means that the wind direction is west wind, and when u _h is a negative value, it means that the wind direction is east wind .

(3) The following example 1 is the transmission flux results obtained based on the fixed-point observation of lidar from January 12 to 15, 2019, and is compared and verified with the simulation results of the WRF-CAMx model (Figure 2). On the 12th, the PM _2.5 concentration near the ground reached the maximum value of this heavy pollution. The simulated value of the fixed-point transmission flux was consistent with the observed value, and the correlation coefficients were all above 0.92. The NMB value was -87.3% to 24.1%, and the NME The value ranges from 28.8% to 87.3%. On the 13th, the concentration of PM _2.5 near the ground decreased, but the pollution level remained high. Compared with the simulated value of fixed-point transmission flux, the correlation coefficient between the two is between 0.88 and 0.97, and the two relative deviation index values are reduced. 17.6%～32.2%. On the 14th, the evolution trend of the simulated value and the observed value in the vertical direction was relatively consistent, the NMB was -20.4% and 84.2%, and the NME was 44.8% and 84.2%, respectively. On the 15th, the concentration of PM _2.5 dropped to a lower level. The simulated value of fixed-point transmission flux was consistent with the observed value. The correlation coefficients were all higher than 0.96. The ranges of NMB and NME values were -41.7% to -18.4% and 19.5%, respectively. %～41.7%. In conclusion, the WRF-CAMx simulation system can well reproduce the evolution characteristics of PM _2.5 transmission flux during heavy pollution.

Scenario 2: The calculation method of the navigation transmission flux based on the mutual verification of the Lidar navigation observation and the model simulation.

Navigational transmission flux refers to the mass of air pollutants passing through a specific vertical section per unit area per unit time.

Among them, (1) the principle of obtaining pollutant transmission flux by lidar navigation observation is based on the three-dimensional distribution results of air pollutant mass concentration obtained by closed-loop navigation observation obtained by lidar, combined with three-dimensional wind field information and vehicle driving azimuth and The included angle of the wind direction can be used to obtain the vertical distribution of the transmission flux of atmospheric pollutants at different heights above the ground on the closed-loop monitoring path. Calculated as follows:

Flux(z) ₌ CP(z)×V(z)×sinθ

where:

Flux(z)——the travel transmission flux of atmospheric pollutants (such as O ₃ , PM _2.5 , etc.) at the height z above the ground, unit: μg·m ^-2 ·s ^-1 ;

C _P (z)——mass concentration of air pollutants (such as O ₃ , PM _2.5 , etc.) at height z above the ground, unit: μg·m ^-2 ·s ^-1 ;

V(z)——The observed wind speed at the height z above the ground, unit: m/s;

sinθ——The angle between the vehicle's azimuth and the wind direction recorded by GPS.

(2) Here, since the lidar navigation observation flux is a closed-loop stereo observation value, therefore, for the verification of this situation of the navigation flux, the specific points concerned in the navigation observation and the WRF-CAMx model are used to simulate The simulation value of the flux at specific grid points is compared and verified, that is, the calculation method of the simulated value of the transmission flux here is the same as that of Case 1, and will not be repeated here.

(3) The following example 2 is the transmission flux results obtained on the Beijing Sixth Ring Road on October 14, 2016 based on the laser radar voyage observation, and it is compared and verified with the simulation results of the WRF-CAMx model (Figure 3-4). Compared with the observed values, the simulated flux intensity of the North Sixth Ring Road is larger, but the two show good consistency, and the correlation coefficient is 0.91. The average intensity range of the simulated flux at each height in the vertical direction is -10.0～-319.0μg·m ^-2 ·s ^-1 , and the overall average intensity is -118.3μg·m ^-2 ·s ^-1 ; the simulated flux intensity The highest value is also located at 359m above the ground, which is -319.0μg·m ^-2 ·s ^-1 ; while the average intensity values in the range below and above 611m above the ground are -162.1μg·m ^-2 ·s ^-1 and -59.8μg respectively. ·m ^-2 ·s ^-1 . Based on the comparison between the observed flux and the simulated flux in the East Sixth Ring Road, it is found that the correlation coefficient of the evolution trend of the two in the vertical direction is 0.82, the simulated flux intensity is higher than the observed value, and the average intensity range is -6.0～-77.2μg m ^-2 ·s ^-1 , the mean value is -39.0μg·m ^-2 ·s ^-1 , the highest intensity occurs at a height of 359m above the ground, and the average flux below and above 459m above the ground is -51.0μg· m ^-2 ·s ^-1 and -26.9 μg·m ^-2 ·s ^-1 , which are higher than the observed fluxes.

Scenario 3: Based on upper-air meteorology-near-surface pollutant observations and model simulations, cross-boundary transmission flux calculation methods are mutually confirmed.

Transboundary flux refers to the mass of air pollutants passing through a vertical section in a specific time.

(1) Based on the wind profiler at a certain point and the monitoring equipment for conventional air pollutants near the ground, the vertical distribution of the wind vector at the point and the mass concentration of conventional air pollutants near the ground can be obtained, and the concentration of pollutants in the vertical direction is lacking. distributed. In view of this situation, if the air pollutants in the target area and the transboundary transmission fluxes of the surrounding areas are calculated, the analysis can be carried out by means of a hypothetical method, that is, it is assumed that the near-surface air pollutants obtained by monitoring at this point can be analyzed. The concentration can represent the concentration of air pollutants in the entire target area, and the pollution concentration is evenly distributed in the vertical direction; and the air pollutant concentration near the ground in adjacent areas can be downloaded from the air quality website, which is also used as the overall concentration of each adjacent area. , and the vertical concentration distribution is uniform. In addition, based on the vertical data of the wind vector obtained by the wind profiler, it can be assumed that the wind vector at the border between the target area and the surrounding adjacent areas is evenly distributed in space, that is, the wind vector values of the target area and adjacent areas are all based on the wind at this point. Vector values to calculate the cross-border transmission flux between the target area and each adjacent area. The formula for calculating the cross-border transmission flux is as follows:

Flux _u =∑ _h L·H _k ·c _up ·u·8.64×10 ^-8

Flux _v =∑ _h L·H _k ·c _up ·v·8.64×10 ^-8

In the formula: Flux _u — the transboundary transmission flux of pollutants in the east-west direction, unit: t/d;

Flux _v ——the transboundary transmission flux of pollutants in the north-south direction, unit: t/d;

h——the vertical highest level observed by the wind profiler, unit: m;

L——the length of the boundary line of the contact between two adjacent areas, unit: m;

H _k ——height resolution of the wind profiler in the vertical direction, unit: m;

C _{up ——mass} concentration of air pollutants in the upwind city, unit: μg/m ³ ;

u——wind speed in the east-west direction, unit: m/s;

v——wind speed in north-south direction, unit: m/s.

(2) The method of simulating the transboundary transmission flux of air pollutants based on the WRF-CAMx three-dimensional numerical model, firstly select the target area, divide the boundary of transboundary transmission of air pollutants according to the method of my country's administrative boundary, and determine the boundary of the air pollutants bordering the target area. Each adjacent area, the setting and principle of regional boundary line (Figure 5). The purple curve represents the administrative boundary line between area A and area B, and the simulation range is divided into different grids by dividing the grid area in the model. The red line represents the boundary line between area A and area B in the model, which is used for simulation Calculation of transboundary fluxes of air pollutant pollution.

The target area is regarded as a three-dimensional three-dimensional box composed of multiple grids. Figure 6 shows the unit area micro-element vector of a vertical section in the box, where V represents the fluid flow rate passing through the area micro-element, and n represents the The normal vector of the area element, c represents the mass concentration of air pollutants at the area element. Calculate the flow velocity of each micro-element on the cross-section, the quantity product of the concentration of air pollutants and the area, and then integrate the entire cross-section to obtain the mass of air pollutants passing through the entire cross-section per unit time.

The WRF-CAMx model belongs to the Euler three-dimensional grid mode, and each grid has fixed three-dimensional spatial coordinates, which can provide the meteorological elements and atmospheric pollutant concentrations of each grid in the study area. In addition, the WRF and CAMx are set to the same vertical layer number (28 layers) and delta parameters, in order to obtain the corresponding wind direction, wind speed and atmospheric pollutant concentration information at the same height above the ground for each grid. To sum up, this study will need to discretize the calculated section according to the grid division method in the WRF and CAMx modes, and use the output data of the two modes to calculate the transboundary transport flux of air pollutants on a specific section. The specific calculation formula is as follows:

Where: Flux——transboundary flux of air pollutants, unit: t/d;

h——the vertical highest level set by the model, unit: m;

l——Boundary line of two adjacent areas, unit: m;

L——simulation grid resolution, unit: km;

H _{k ——the} height difference between the simulated vertical layer k and k+1;

c——mass concentration of air pollutants (such as O ₃ , PM _2.5 ), unit: μg/m ³ ;

v——wind direction and wind speed, unit: ° and m/s;

n - the normal vector through the vertical section, dimensionless.

Based on the above cross-boundary transmission flux calculation formula, the inflow of air pollutants into the target area is positive, and the outflow of the target area is negative, from a single box, multiple boxes at the same ground height at the boundary line to all boxes in the vertical direction, The inflow and outflow fluxes of atmospheric pollutants at different heights above the ground were calculated respectively. Net flux refers to the vector sum of the inflow and outflow fluxes of atmospheric pollutants, where positive values represent net inflow fluxes and negative values represent net outflow fluxes.

Figure 7 is a schematic diagram of the PM _2.5 inflow and outflow flux at the vertical section of a single box.

FIG. 8 is a schematic diagram of a vertical section at the boundary line of adjacent regions after discretization.

(3) The following example 3 is to take Shunyi District of Beijing as the target area, and divide the municipal districts/cities bordering it into 7 parts according to the administrative boundaries, which are Huairou District, Miyun District, Pinggu District, Changping District, Tongzhou District, Chaoyang District and the northern part of Langfang City (Fig. 9), based on the wind profiler, routinely observed the wind field of Beijing Capital Airport, and obtained the vertical wind field (wind speed and direction) of the Capital Airport station. Changes with different altitudes , and the wind profile data observed at the Capital Airport represent the wind field changes in Shunyi District. At the same time, based on the statistical data of pollutant concentration in the environmental monitoring stations of Beijing and Langfang City, this study obtained the PM _2.5 hourly concentration values of 7 bordering districts/cities around Shunyi, and assumed that the PM _2.5 concentration and the near-ground concentration within a height of 1300m above the ground Similarly, the observed values of PM _2.5 trans-regional/city transport fluxes were calculated. In addition, based on the WRF-CAMx model, the wind field and PM _2.5 concentration information at the boundary line of Shunyi District and the surrounding 7 districts/cities below the 10th floor in the vertical direction (about 1300m from the ground) are extracted, and the PM _2.5 cross-district/city information is calculated. Simulated value of city transmission flux. Finally, the observed and simulated values of PM _2.5 transmission flux were compared and analyzed to verify the accuracy of the WRF-CAMx model simulation.

Figure 10 shows the vertical distribution of simulated and observed PM _2.5 net fluxes in Shunyi and surrounding areas in representative months of different seasons (January, April, July, October). The inflow flux is a positive value, which means that the surrounding area/city inputs PM _2.5 to Shunyi District, and the outflow flux is a negative value, which means that the Shunyi District outputs PM _2.5 to the surrounding area/city; the net flux is the vector of inflow and outflow fluxes and, positive values represent net inflow, indicating that the amount of PM _2.5 input from the surrounding area/city to Shunyi District is higher than the output from Shunyi District, and negative values represent net outflow, indicating that the amount of PM _2.5 output from Shunyi District to the surrounding area/city is higher than Input from the surrounding. The results show that the correlation coefficients between the simulated and observed values of PM _2.5 inflow, outflow and net flux range from 0.48 to 0.92, 0.71 to 0.96 and 0.49 to 0.98, respectively, and the range of NMB values is 6.0% to 69.1% and -71.7%. ~54.5% and -50.0% to 76.2%, the NME ranges were 10.6% to 85.5%, 18.7% to 71.7% and 21.3% to 79.2%. The reason for the relatively high errors of NMB and NME is that the concentration of PM _2.5 at each grid observation point in the vertical direction within 1300m assumed in this study is the same, which will be different from the actual distribution of PM _2.5 concentration, but in general, the PM _2.5 flux The simulated and observed values are relatively consistent, indicating that the WRF-CAMx model simulation can be used to study the PM _2.5 transboundary fluxes in Shunyi and surrounding counties. Especially in January, April, July and October, the simulated values of the total net flux of PM _2.5 below 400m were -28.99t/d, 27.04t/d, 13.50t/d, and -37.76t/d, respectively. are -24.32t/d, 16.41t/d, 7.89t/d, -29.20t/d respectively; the simulated values of the total net flux of PM _2.5 above 400m are -125.13t/d, 87.71t/d, 14.71t, respectively /d, -236.22t/d, and the observed values are -87.46t/d, 64.49t/d, 23.20t/d, and -166.09t/d, respectively. The simulated and observed values of the net flux change in the vertical direction. Consistent. Overall, the simulated value of the total net flux is generally higher than the observed value (except in July), which may be related to the high simulated value of wind speed; the relative error ranges of below 400m and above 400m are 19.2%～71.1 % and -36.6% to 43.1%, which are within the acceptable range, indicating that the WRF-CAMx model can be used to further simulate the transmission flux across cities and provinces/regions.

The present invention also provides a method for identifying a pollution transmission channel based on the transboundary transmission flux of pollutants, comprising the following steps:

Based on the WRF-CAMx three-dimensional numerical model, the inflow, outflow and net fluxes of air pollutants between each city in the study area and its surrounding areas can be simulated. According to the inflow and outflow of air pollutants in each target city The inflow and outflow directions of all cities in the target area are sorted out and integrated, so as to obtain the overall inflow and outflow directions of air pollutants in the area, and then identify the transmission channels in the target area.

Taking the Beijing-Tianjin-Hebei region as an example, based on the WRF-CAMx three-dimensional numerical model simulation, the PM _2.5 cross-border of typical cities in the Beijing-Tianjin-Hebei region (Beijing, Tianjin, Shijiazhuang, Tangshan) and the overall region of Beijing-Tianjin-Hebei and surrounding provinces and cities was analyzed. The transmission flux is simulated and calculated to identify the transmission direction between cities and between the Beijing-Tianjin-Hebei region and surrounding provinces and cities, where "↘, ↗, →, and ↖" represent northwest to southeast, southwest to northeast, west respectively to east, southeast to northwest (Table 2). The main transmission channels of PM _2.5 pollution in January, April, July and October in the Beijing-Tianjin-Hebei region were identified (Fig. 11).

Table 2 Transmission paths and main directions of cities and regions in January, April, July, and October 2016

Above, based on meteorological observation, lidar stereo observation and three-dimensional numerical simulation technology, the present invention has established calculation methods for fixed-point transmission flux, navigational transmission flux and cross-border transmission flux for various pollutants and different situations, and Comparing and verifying the flux quantification results obtained by stereo observation and model simulation; the present invention establishes a method for identifying the main transmission channels of air pollutants based on the flux quantification results of cross-regional, cross-city and cross-regional transmission of air pollutants .

Claims (5)

1. A multi-pollutant cross-boundary transmission flux quantification integration technical method is characterized in that a fixed point transmission flux observed value and a simulation value of a pollutant are respectively obtained based on laser radar fixed point observation and a WRF-CAMx three-dimensional numerical model, and then model parameters are adjusted by analyzing the accuracy of simulation result verification so as to optimize the WRF-CAMx three-dimensional numerical model and improve the model simulation accuracy; wherein:

when the laser radar performs fixed-point observation to obtain a fixed-point transmission flux observed value of a pollutant, the laser radar performs online observation based on the laser radar and a wind profiler, and combines a three-dimensional distribution structure of the mass concentration of the atmospheric pollutant obtained by two devices with three-dimensional wind field data to obtain the vertical distribution of the transmission flux of the atmospheric pollutant at different heights of an observation station; the fixed-point transmission flux observed value is the product of the monitored mass concentration and the wind vector of the atmospheric pollutants, and the calculation formula is as follows:

FLUX _NSh ＝C _ph ×V _NSh

FLUX _EWh ＝C _ph ×V _EWh

in the formula:

FLUX _NSh -the observed value of the fixed point transmission flux of the atmospheric pollutants with the height h meters above the ground in the south and north directions and the unit of the observed value is mu g.m ^-2 ·s ^-1 (ii) a When FLUX _NSh When the value is positive, it is defined as the input of atmospheric pollutants from south to north, when FLUX _NSh When the value is negative, the atmospheric pollutants are output from north to south;

FLUX _EWh -the observed value of the fixed-point transmission flux of the atmospheric pollutants with the height h meters above the ground in the east-west direction is in units of mu g.m ^-2 ·s ^-1 (ii) a When FLUX _EWh When the value is positive, it is defined that the atmospheric pollutant is input from west to east, when FLUX _EWh When the value is negative, the atmospheric pollutants are defined to be output from east to west;

C _Ph atmospheric pollutants (e.g. O) at a height h meters above the ground ₃ 、PM _2.5 Etc.) in units of μ g/m ³ ；

V _NSh -the observed value of the wind vector in the south-north direction at the height h m from the ground is m/s when V _NSh When the value is positive, the wind direction is south wind, when V _NSh When the value is negative, the wind direction is north wind;

V _EWh -the observed value of the wind vector in the east-west direction at the height h m from the ground in m/s when V _EWh When the value is positive, the wind direction is West wind, and when V is positive _EWh When the value is negative, the wind direction is east wind;

when a WRF-CAMx three-dimensional numerical model is used for simulating and obtaining a fixed-point transmission flux simulation value, a target area is regarded as a three-dimensional box body formed by a plurality of grids, each grid has a fixed three-dimensional space coordinate, and meteorological elements and atmospheric pollutant concentrations of each grid in a research area are respectively provided; in order to obtain wind direction, wind speed and concentration information of atmospheric pollutants corresponding to the same height above the ground of each grid, and to facilitate comparison and verification with transmission flux stereo observation data, WRF and CAMx are set to be the same vertical layer number and delta coordinate parameters, wherein the delta coordinate parameter is a coordinate parameter defined for setting the height of each vertical layer in the vertical direction in a WRF meteorological model, the value range of the delta coordinate parameter is [0-1], and the WRF meteorological model automatically sets the height of each vertical layer according to the set delta coordinate parameter; the fixed point transmission flux analog value is the product of pollutant analog mass concentration and analog wind vector, wherein the pollutant analog mass concentration is obtained through CAMx air quality model simulation, the analog wind vector comprises wind direction and wind speed, and is obtained through WRF meteorological model simulation, and the calculation formula is as follows:

FLUX' _NSh ＝C' _ph ×v _h

FLUX' _EWh ＝C' _ph ×u _h

in the formula:

FLUX’ _NSh -the fixed point transmission flux analog value of h meters atmospheric pollutants from the ground in the north-south direction with the unit of mu g.m ^-2 ·s ^-1 (ii) a When FLUX' _NSh When positive, it is defined as the air pollutant entering from south to north when FLUX' _NSh When the value is negative, the atmospheric pollutants are output from north to south;

FLUX’ _EWh -the fixed point transmission flux analog value of the atmospheric pollutants with the height h meters above the ground in the east-west direction, and the unit is mu g.m ^-2 ·s ^-1 (ii) a When FLUX' _EWh When positive, it is defined as atmospheric pollutants entering from west to east, when FLUX' _EWh When the value is negative, the atmospheric pollutants are defined to be output from east to west;

C’ _Ph atmospheric pollutants (e.g. O) at a height h meters above the ground ₃ 、PM _2.5 Etc.) in μ g/m ³ ；

V _h -the wind vector simulation value in the south-north direction at the height h meter from the ground is m/s when V _h When the value is positive, the wind direction is south wind, and when V is positive _h When the value is negative, the wind direction is north wind.

u _h -wind vector analog value in the east-west direction at a height h m from the ground in m/s when u _h When the value is positive, the wind direction is West wind, and when u is positive _h When the value is negative, the wind direction is east wind.

2. The multi-pollutant cross-boundary transmission flux quantitative integration technical method is characterized in that an observed value and a simulated value of the cross-boundary transmission flux of a pollutant are respectively obtained based on laser radar navigation observation and WRF-CAMx three-dimensional numerical model simulation, and then model parameters are adjusted by analyzing the accuracy of simulation result verification so as to optimize the WRF-CAMx three-dimensional numerical model and improve the model simulation accuracy; wherein:

when the laser radar sailing observation obtains a sailing transmission flux observation value of pollutants, the vertical distribution of the transmission flux of the atmospheric pollutants at different ground heights on a closed-loop monitoring path is obtained by combining three-dimensional wind field information and an included angle between a vehicle driving azimuth and a wind direction based on a three-dimensional distribution result of the mass concentration of the atmospheric pollutants obtained by the laser radar through closed-loop sailing observation; the calculation formula of the observation value of the navigation transmission flux is as follows:

Flux(z)＝C _P (z)×V(z)×sinθ

in the formula:

flux (z) -airborne transport flux of atmospheric pollutants at height z from the ground in units: μ g.m ^-2 ·s ^-1 ；

C _P (z) -mass concentration of atmospheric pollutants at height z from the ground in units: μ g.m ^-2 ·s ^-1 ；

V (z) -observed wind speed at height z from the ground in units: m/s;

sin theta is the included angle between the vehicle running azimuth and the wind direction recorded by the GPS;

and when the sailing transmission flux analog value is calculated, comparing and verifying the specific point position concerned in sailing observation and the specific grid point position flux analog value simulated by the WRF-CAMx model, namely, the sailing transmission flux analog value is the product of the pollutant analog concentration and the analog wind vector.

3. The multi-pollutant cross-boundary transmission flux quantitative integration technical method is characterized in that an observed value and a simulated value of cross-boundary transmission flux of pollutants are respectively obtained based on high-altitude weather-near-ground pollutant observation and WRF-CAMx three-dimensional numerical model simulation, and then model parameters are adjusted by analyzing the accuracy of simulation result verification so as to optimize the WRF-CAMx three-dimensional numerical model and improve the model simulation accuracy;

when calculating the cross-boundary transmission flux observed value of the atmospheric pollutants in the target area and the adjacent areas, considering the atmospheric pollutant monitoring concentration and wind vector observed value of the target area and the adjacent areas; for the atmospheric pollutant monitoring concentration, the concentration of the near-surface atmospheric pollutants obtained by monitoring the point position of the target area through a near-surface conventional atmospheric pollutant monitoring device is assumed to represent the concentration of the atmospheric pollutants in the whole target area, the pollution concentration is uniformly distributed in the vertical direction, the concentration of the near-surface atmospheric pollutants in the adjacent areas is obtained by downloading through an air quality website and is also used as the whole concentration of each adjacent area, and the concentration is uniformly distributed in the vertical direction; for the observed value of the wind vector, the wind vector at the border between the target area and each adjacent area is assumed to be consistent, that is, the wind speed and the wind direction of the target area and each adjacent area are obtained by adopting a wind profiler erected based on the target area; on the basis, calculating a cross-boundary transmission flux observed value between the target region and each adjacent region; the formula for calculating the cross-boundary transmission flux observed value is as follows:

Flux _u ＝∑ _h L·H _k ·c _up ·u·8.64×10 ^-8

Flux _v ＝∑ _h L·H _k ·c _up ·v·8.64×10 ^-8

in the formula: flux _u Trans-boundary transport flux of contaminants in the east-west direction, in units: t/d;

Flux _v -trans-boundary transport flux of contaminants in north-south direction, unit: t/d;

h-the vertical highest layer observed by the wind profiler, unit: m;

l-the length of the boundary line where two adjacent regions contact, unit: m;

H _k -height resolution in the vertical direction of the wind profiler, units：m；

C _up -mass concentration of atmospheric pollutants in upwind cities in units: mu g/m ³ ；

u-wind speed in the east-west direction, unit: m/s;

v-wind speed in the north-south direction, in units: m/s.

A method for simulating the cross-boundary transmission flux of atmospheric pollutants based on a WRF-CAMx three-dimensional numerical model is as follows: firstly, selecting a target area, dividing the boundary of the cross-boundary transmission of the atmospheric pollutants according to an administrative boundary line method, determining each adjacent area bordering the target area, and dividing a simulation range into different grids for simulating and calculating the cross-boundary transmission flux of the atmospheric pollutants through gridding division in a model;

the target area is regarded as a three-dimensional box body formed by a plurality of grids, a certain vertical section in the box body is selected, the product of the flow velocity of each infinitesimal element on the section, the concentration of the atmospheric pollutants and the area is calculated, and then the integral is carried out on the whole section, so that the mass of the atmospheric pollutants passing through the whole section in unit time is obtained;

the WRF-CAMx mode belongs to an Euler three-dimensional grid mode, each grid has a fixed three-dimensional space coordinate, a section needing to be calculated is discretized according to a grid division mode in the WRF and CAMx modes, the cross-boundary transmission flux of the atmospheric pollutants on the specific section is calculated by using output data of the two modes, and a specific calculation formula is as follows:

in the formula: flux — the trans-boundary transport Flux of atmospheric pollutants, unit: t/d;

h-vertical highest layer of model setup, unit: m;

l-boundary line of two adjacent areas, unit: m;

l-simulation grid resolution, unit: km;

H _k between the simulated vertical layers k and k +1The height difference of (a);

c-mass concentration of atmospheric pollutants, unit: mu g/m ³ ；

v-wind direction and speed, unit: DEG and m/s;

n-normal vector through vertical section, dimensionless;

based on a cross-boundary transmission flux calculation formula, respectively calculating inflow fluxes and outflow fluxes of atmospheric pollutants at different ground heights from a single box body, a plurality of box bodies at the same ground height on a boundary line to all box bodies in the vertical direction by taking the inflow target area of the atmospheric pollutants as positive and the outflow target area as negative; the net flux refers to the vector sum of the inflow and outflow fluxes of atmospheric pollutants, where positive values represent the net inflow flux and negative values represent the net outflow flux.

4. The multi-pollutant cross-boundary transmission flux quantitative integration technical method as claimed in one of claims 1 to 3, characterized in that observed values and simulated values of the transmission flux of pollutants are compared and verified by introducing correlation coefficients COR, normalized mean deviation NMB and normalized mean error NME statistical indexes, and the accuracy of verification of the simulated results is analyzed.

5. A method for identifying a contaminated transport channel based on the multi-contaminant cross transport flux quantification and integration technique of claim 3, comprising the steps of:

based on an optimized WRF-CAMx three-dimensional numerical model, inflow flux, outflow flux and net flux in the cross-boundary transmission flux of the atmospheric pollutants between each city and the adjacent periphery in the research area are obtained through simulation, all city inflow and outflow directions in the target area are combed and integrated according to the inflow and outflow directions of each target city atmospheric pollutant, and therefore the overall inflow and outflow directions of the atmospheric pollutants in the area are obtained, and further the transmission channel in the target area is identified.

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