Method and system for monitoring methane emission of refuse landfill based on air-ground combined monitoring

Abstract

The invention provides a refuse landfill methane emission monitoring method and system for air-ground combined monitoring, ground sampling points are selected by combining topographic features, possible emission hot spot areas and historical operation information of a refuse landfill, and areas which are difficult to reach by ground sampling can be realized through aerial survey air sampling; by integrating ground sampling and aerial survey, high-resolution methane concentration data can be obtained, and meanwhile interference of flowing wind on hot spot area recognition is reduced; by combining ground surface sampling data and aerial survey data, a Getis-Ord Gi * statistical method and a nuclear density estimation method are adopted to carry out bimodal hot spot area identification, a methane emission source area can be positioned more accurately, the precision and efficiency of methane emission monitoring of the refuse landfill are remarkably improved, and the method is suitable for popularization and application. The methane emission source of the refuse landfill is accurately and efficiently found, the emission amount of the methane emission source is evaluated, targeted suggestions are provided for operation of the landfill, and the method has important environmental protection and economic values.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental monitoring, and relates to a method and system for monitoring methane emissions. Background Art

[0002] Landfills play an important role in the process of urban solid waste treatment, but a large amount of methane is generated during the landfill and subsequent maintenance processes. Methane is a major greenhouse gas that has a significant impact on climate change. How to accurately and efficiently find the methane emission sources in landfills and evaluate their emission amounts is of great significance for methane recovery and greenhouse gas emission reduction management in landfills.

[0003] Existing ground sampling methods for methane emission monitoring generally include handheld device detection and fixed monitoring stations, etc. However, in large or complex terrain landfills, relying solely on ground monitoring means has problems such as insufficient sampling point density, limited coverage, and low operation efficiency. At the same time, due to the complex surface structure of landfills and uneven distribution of emission sources, it is difficult for traditional ground sampling monitoring to accurately locate and quantify methane emission sources. In recent years, with the development of unmanned aerial vehicle (UAV) remote sensing technology, using UAVs equipped with lidar, infrared cameras, or methane detection sensors to observe the methane concentration in the air has become an emerging monitoring method. This method can provide high-resolution sampling data, quickly obtain the global methane concentration, and measure areas that are difficult to reach on the ground. However, if only relying on UAVs for aerial surveys, due to the interference of air flow over landfills, it is difficult to distinguish whether high-concentration areas are real emission sources, which may lead to missed and misjudgments. All in all, with the current monitoring methods, it is difficult to accurately and efficiently find the methane emission sources in landfills and evaluate their emission amounts, and it is difficult to provide targeted suggestions for the operation of landfills. Summary of the Invention

[0004] To solve the problem that the current monitoring methods described in the background art are difficult to accurately and efficiently find the methane emission sources in landfills and evaluate their emission amounts, the present invention provides a method and system for monitoring methane emissions from landfills by combining aerial and ground monitoring.

[0005] The method of the present invention includes: Constructing a three-dimensional model of the landfill based on the aerial survey point cloud data and image data obtained for the landfill area; Based on the three-dimensional model of the landfill, combining the topographic features of the landfill, possible emission hotspot areas, and historical operation information, selecting a number of ground sampling points, and performing ground sampling of methane emissions according to the ground sampling points to obtain surface methane concentration sampling data of the landfill; Based on the three-dimensional model of the landfill and several selected ground sampling points, determine the aerial survey height and the aerial survey route area for methane emission aerial sampling, and obtain the aerial survey methane concentration distribution data above the landfill; Based on the three-dimensional model of the landfill, according to the longitude and latitude coordinates of the aerial survey sampling points, spatially register the surface methane concentration sampling data and the aerial survey methane concentration distribution data, obtain the ground elevation and the aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data; Use the Getis-Ord Gi* statistic method to analyze the surface methane concentration sampling data of the landfill to obtain the surface hot spot area, and use the kernel density estimation method to analyze the aerial survey average methane concentration data to obtain the aerial survey hot spot area; Map the results of the surface hot spot area and the aerial survey hot spot area to the three-dimensional model of the landfill, and through the calculation of the local Jaccard coefficient, screen to obtain the methane emission source area; Collect and obtain the environmental meteorological parameters of the landfill, combine the methane emission source area and its corresponding surface methane concentration sampling data and aerial survey average methane concentration data, and calculate the methane emission flux through the mass balance method.

[0006] Furthermore, for the surface methane concentration sampling data of the landfill and the aerial survey methane concentration distribution data above the landfill, perform data preprocessing: for the case of random data missing, use the interpolation method to supplement or directly delete; for the systematic data missing caused by including sampling detection equipment failures, mark it during statistics and re-sample and monitor if necessary; for data outliers, use statistical methods including 3 times the standard deviation, box plot method or setting thresholds according to physical background common sense to mark and remove the outliers.

[0007] Furthermore, the method for spatially registering the surface methane concentration sampling data and the aerial survey methane concentration distribution data includes: based on the three-dimensional model of the landfill, obtain the digital elevation model of the landfill through aerial survey software; the spatial coordinate systems used for methane emission ground sampling and aerial sampling are the same coordinate system, match the longitude and latitude coordinates of the aerial survey sampling points in the digital elevation model of the landfill, and obtain the ground elevation and the aerial survey elevation of the same sampling point; Calculate the integration path length of the aerial survey methane concentration detection equipment according to the ground elevation and the aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration. The formula is as follows: , , In the formula: is the aerial survey average methane concentration of the sampling point; is the path integral concentration of the aerial survey methane concentration detection equipment at the sampling point, is the integration path length of the aerial survey methane concentration detection equipment; is the elevation of the take-off point of the aerial survey; is the flight altitude of the aerial survey; is the ground elevation of the sampling point.

[0008] Furthermore, the method for obtaining the surface hot spot area includes: calculating the weighted neighborhood sum for each ground sampling point; calculating the global mean and standard deviation; iteratively calculating the Gi* value of each ground sampling point; converting the Gi* value of each ground sampling point into a Z-score; obtaining the surface hot spot area according to the actual evaluation requirements of the Z-score; When calculating the Getis-Ord Gi* statistic, a suitable neighborhood range needs to be set according to the distribution density of the ground data, and the formula is as follows: , In the formula, is the element i and j is the spatial weight between; is the element j 's attribute value; is the neighborhood weighted sum; is the global mean; is the global standard deviation; is the total sample, that is, the total number of methane concentration data points collected by the aerial survey.

[0009] The method for obtaining the aerial survey hot spot area includes: applying the kernel density estimation method to calculate the spatial density, using a Gaussian kernel, and its expression is: , , In the formula, is the kernel function, indicating the density contribution intensity of the data point to the surrounding positions; is the standardized distance; is the bandwidth; is the target position; is the data point position; Select the bandwidth according to Silverman's rule , and the expression is: , In the formula, is the bandwidth; IQR is the difference between the upper quartile (Q3) and the lower quartile (Q1) of the data; is the standard deviation; is the total number of methane concentration data points collected by the aerial survey; For each grid point , calculate the density contribution of its surrounding points: , wherein, is the estimated value of methane concentration density at the spatial position ; is the total number of methane concentration data points collected by aerial survey; For the calculated spatial density values, aerial survey hot spot areas are determined based on empirical quantiles.

[0010] Furthermore, the screening method for the methane emission source area includes: Generating binary grids for both the surface hot spot area results and the aerial survey hot spot area results to obtain a ground hot spot grid and an aerial survey hot spot grid; Using a vector polygon file to define the boundary of the landfill; Making the resolutions, coordinate systems, and spatial ranges of the ground hot spot grid and the aerial survey hot spot grid consistent; Using the boundary of the landfill as a mask to crop the ground hot spot grid and the aerial survey hot spot grid to exclude interference from external areas; Selecting the grid size according to the hot spot scale; Generating a regular grid covering the landfill; For each grid cell, counting the number of aerial survey hot spot pixels and the number of overlapping pixels , and calculating the local Jaccard coefficient to quantify the overlapping degree between the two. The calculation formula is as follows: , wherein, is the Jaccard coefficient, is the set of aerial survey hot spot pixels in grid ; is the set of ground hot spot pixels in grid ; Evaluating the spatial consistency of the ground hot spots within the aerial survey hot spot range based on the Jaccard coefficient, and screening to obtain the methane emission source area.

[0011] Furthermore, the calculation method for the methane emission flux is: Combining the measured methane concentration distribution and the simultaneously obtained environmental meteorological parameters of the landfill, and calculating the methane emission flux using the mass balance method. The calculation formula is as follows: , wherein, F is the emission rate of the emission source; H is the integral height of the plane perpendicular to the wind direction; W is the integral width of the plane perpendicular to the wind direction; u is the wind speed perpendicular to the aerial survey plane; is the methane concentration signal enhancement value, with the upwind test value as the background value , the downwind test value and the background value The difference is recorded as the methane concentration signal enhancement value.

[0012] Furthermore, a portable methane analyzer is used for ground sampling of methane emissions from landfills; a drone equipped with a laser methane concentration detector is used for aerial sampling of methane emissions from landfills; a drone equipped with an airborne weather instrument is used to collect environmental meteorological parameters of landfills.

[0013] Based on the above method, the present invention proposes a landfill methane emission monitoring system for combined ground and aerial monitoring, including a landfill three-dimensional model construction module, a surface methane concentration sampling data acquisition module, an aerial survey methane concentration distribution data acquisition module, an aerial survey average methane concentration data calculation module, a hot spot area acquisition module, a methane emission source area screening module, and a methane emission flux calculation module.

[0014] The landfill three-dimensional model construction module is used to construct a landfill three-dimensional model based on the aerial survey point cloud data and image data obtained by aerial surveying the landfill area.

[0015] The surface methane concentration sampling data acquisition module is used to select a number of ground sampling points based on the landfill three-dimensional model, combined with the topographic features of the landfill, possible emission hot spot areas, and historical operation information, and conduct ground sampling of methane emissions according to the ground sampling points to obtain the surface methane concentration sampling data of the landfill.

[0016] The aerial survey methane concentration distribution data acquisition module is used to determine the aerial survey height and aerial survey route area for aerial sampling of methane emissions based on the landfill three-dimensional model and the selected number of ground sampling points, and obtain the aerial survey methane concentration distribution data over the landfill.

[0017] The aerial survey average methane concentration data calculation module is used to spatially register the surface methane concentration sampling data and the aerial survey methane concentration distribution data based on the landfill three-dimensional model, according to the longitude and latitude coordinates of the aerial survey sampling points, obtain the ground elevation and aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data.

[0018] The hot spot area acquisition module is used to analyze the surface methane concentration sampling data of the landfill by using the Getis-Ord Gi* statistic method to obtain the surface hot spot area, and analyze the aerial survey average methane concentration data by using the kernel density estimation method to obtain the aerial survey hot spot area.

[0019] The methane emission source area screening module is used to map the results of the surface hot spot area and the aerial survey hot spot area to the three-dimensional model of the landfill, and screen the methane emission source area through the calculation of the local Jaccard coefficient.

[0020] The methane emission flux calculation module is used to collect the environmental meteorological parameters of the landfill, and calculate the methane emission flux by the mass balance method based on the methane emission source area and its corresponding surface methane concentration sampling data and aerial survey average methane concentration data.

[0021] The present invention also provides an electronic device, including: a memory and a processor, which are communicatively connected to each other. The memory stores computer instructions, and the processor realizes a method for monitoring methane emissions from a landfill by air-ground joint monitoring as described above by executing the computer instructions.

[0022] The present invention also provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it realizes a method for monitoring methane emissions from a landfill by air-ground joint monitoring as described above.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) Accurate data: By integrating ground sampling and aerial survey, high-resolution methane concentration data can be obtained, and at the same time, the interference of flowing wind on the identification of hot spot areas can be reduced, improving the accuracy of data. (2) Optimization of sampling cost and safety: Combining the topographic features of the landfill, possible emission hot spot areas, and historical operation information, the ground sampling points are selected. Areas that are difficult to reach by ground sampling can be achieved by aerial survey air sampling, reducing the sampling cost and improving the operation safety. (3) Dual-modal hot spot area identification: By combining surface sampling data and aerial survey data, the Getis-Ord Gi* statistic method and the kernel density estimation method are used for dual-modal hot spot area identification, which can more accurately locate the methane emission source area and improve the accuracy of emission source location. (4) Wide applicability: The present invention is applicable to landfills with flat terrain and complex terrain, and can improve the accuracy of emission source location and flux quantification at low cost and high efficiency, providing a scientific basis for methane recovery and greenhouse gas emission reduction management. (5) Targeted quantification of emission sources: The aerial survey sampling method of the present invention is different from the traditional full-field up-and-down profile flight aerial survey method, so that the methane emission flux can be quantified for a single emission source area, and the methane emission flux of the whole field can be obtained by addition, providing more accurate suggestions for the discrimination and treatment of potential high-emission areas in landfills. (6) Provide scientific basis: By using the sampling method combining aerial and ground sampling, quickly locate and accurately quantify the methane emission sources in landfills, provide scientific basis for subsequent methane recovery and emission reduction management, and provide targeted suggestions for the operation and management of landfills.

[0024] Generally speaking, through the combined air-ground monitoring, dual-modal hotspot area identification, and targeted emission source quantification, the present invention significantly improves the accuracy and efficiency of methane emission monitoring in landfills, accurately and efficiently finds the methane emission sources in landfills and evaluates their emission amounts, provides targeted suggestions for the operation of landfills, and has important environmental protection and economic values. Description of the Drawings

[0025] Figure 1 It is the overall flowchart of the method of the present invention.

[0026] Figure 2 It is the specific implementation flowchart of Embodiment 1.

[0027] Figure 3 It is the schematic diagram of ground sampling and UAV sampling in Embodiment 1.

[0028] Figure 4 It is the schematic diagram of aerial survey data spatial registration in Embodiment 1.

[0029] Figure 5 It is the schematic diagram of dual-modal hotspot identification and emission source location in Embodiment 1.

[0030] Figure 6 It is the schematic diagram of methane emission flux calculation in Embodiment 1.

[0031] Figure 7 It is the system architecture diagram of the present invention. Specific Embodiments

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer, the following further details the present application in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. Embodiment 1

[0033] A method for monitoring methane emissions from landfills by combined air-ground monitoring. The overall flowchart of the method is as Figure 1 shown, and the specific implementation flowchart of this embodiment is as Figure 2 shown, and is specifically described as follows.

[0034] First, based on the aerial survey point cloud data and image data obtained from the aerial survey of the landfill area, a three-dimensional model of the landfill is constructed.

[0035] Specifically, a lidar ranging camera can be carried by a drone to conduct aerial surveys of the landfill area, obtaining the shape and area of the landfill. Based on the digital surface model, through the post-processing and stitching of aerial point cloud data and image data, a high-precision three-dimensional model file of the landfill is constructed, providing a basis for the reasonable layout of subsequent monitoring routes and the registration of ground observation data.

[0036] In this embodiment, the process of constructing the three-dimensional model of the landfill is as follows: Aerial survey preparation: Select a drone platform and carry a lidar ranging camera. According to the terrain complexity, adjust the flight height and flight speed. For example, the flight height is 80 meters and the flight speed is 4 meters per second to ensure coverage of complex terrain areas such as hills and slopes.

[0037] Data collection: The drone covers the entire landfill area according to the pre-planned route and conducts multiple aerial surveys to obtain comprehensive point cloud data and image data. Each aerial survey should ensure that the overlap rate reaches more than 60% to ensure the accuracy of data stitching.

[0038] Data processing and three-dimensional model construction: Use professional aerial survey software to post-process the obtained point cloud data and image data, including point cloud filtering, registration, stitching, and three-dimensional reconstruction, to generate a high-precision three-dimensional model file of the landfill, such as LAS format or OBJ format. This model will be used for the layout of subsequent monitoring points and routes and the registration of ground observation data.

[0039] Then, based on the three-dimensional model of the landfill, combined with the terrain characteristics of the landfill, possible emission hot spots, and historical operation information, several ground sampling points are selected. Methane emissions are sampled on the ground according to the ground sampling points to obtain surface methane concentration sampling data of the landfill.

[0040] Specifically, in the selection of ground sampling points, attention should be paid to the sampling interval and coverage area. Compared with the aerial survey monitoring resolution, the ground sampling points should consider the reasonable interval and position distribution of low resolution. Portable methane analyzers and other equipment can be used for ground sampling to measure the surface methane concentration, and preprocessing work is carried out on the data obtained from ground sampling.

[0041] In this embodiment, the interval between several selected ground sampling points should ensure low-resolution coverage. One sampling point is set every 50 meters to balance the sampling density and monitoring cost; the sampling point interval can be appropriately adjusted according to terrain changes, such as setting one sampling point every 30 meters to ensure methane concentration measurement coverage in complex terrains. At the selected ground sampling points, a handheld laser methane detector is used to measure the ground methane concentration. Each ground sampling point records: methane concentration value, measurement time, GPS coordinates, and environmental meteorological parameters such as temperature, humidity, wind speed, and wind direction.

[0042] Based on the three-dimensional model of the landfill and several selected ground sampling points, the aerial survey altitude and route area for aerial sampling of methane emissions were determined to obtain aerial survey methane concentration distribution data over the landfill.

[0043] Specifically, based on the layout of ground sampling points and the three-dimensional model of the landfill, the aerial survey altitude and route area for aerial sampling of methane emissions are determined on the premise of meeting safety requirements. Aerial survey can use drones equipped with methane concentration detection equipment, meteorological instruments, laser radars, infrared imagers and other sensors to obtain aerial survey methane concentration distribution data and environmental meteorological parameters at a certain height above the landfill, and pre-process the data obtained by drone aerial survey sampling. When sampling with aerial survey drones, attention should be paid to the division of flight areas and flight altitudes.

[0044] In this embodiment, the flight altitude and flight route of the drone are determined according to the three-dimensional model of the landfill and the layout of the ground sampling points. The flight altitude is 80 meters, and the route design should cover the entire area of ​​the landfill to ensure the comprehensiveness and high resolution of the data. The drone is equipped with a laser methane concentration detector and an airborne meteorological instrument. The laser methane concentration detector is based on tunable semiconductor laser absorption spectroscopy technology and samples and records: methane concentration value, measurement time, GPS coordinates, and environmental meteorological parameters such as temperature, humidity, wind speed, and wind direction.

[0045] The schematic diagram of ground sampling and drone sampling in this embodiment is as follows Figure 3 shown.

[0046] More specifically, data preprocessing is performed on the surface methane concentration sampling data of the landfill and the aerial survey methane concentration distribution data over the landfill: for random missing data, interpolation is used to supplement or directly delete; for systematic missing data caused by sampling and detection equipment failure, it is marked during statistics, and re-sampling and monitoring are performed if necessary; for data outliers, statistical methods including 3 times the standard deviation, box plot method or threshold setting based on physical background common sense are used to mark and remove outliers. However, due to the high variability of methane concentration distribution in landfills, it is necessary to identify the screened outliers in combination with expert experience.

[0047] Based on the three-dimensional model of the landfill, the surface methane concentration sampling data and the aerial survey methane concentration distribution data were spatially aligned according to the latitude and longitude coordinates of the aerial survey sampling points, the ground elevation and aerial survey elevation of the same sampling point were obtained, and the aerial survey average methane concentration data was calculated.

[0048] Due to certain elevation changes on the surface of the landfill, it is difficult to plan terrain-following flights during the aerial survey by drones. Therefore, by spatially matching the aerial survey sampling data of the drone with the digital elevation model of the landfill, that is, matching the longitude and latitude coordinates of the aerial survey sampling points of the drone in the digital elevation model of the landfill, the ground elevation and the aerial survey elevation of the same sampling point are obtained.

[0049] In this embodiment, the schematic diagram of the spatial registration of aerial survey data is as Figure 4 shown.

[0050] Specifically, based on the three-dimensional model of the landfill, the digital elevation model of the landfill is obtained through aerial survey software; the spatial coordinate systems used for ground sampling and aerial sampling of methane emissions are the same coordinate system, such as the WGS84 coordinate system. The longitude and latitude coordinates of the aerial survey sampling points are matched in the digital elevation model of the landfill to obtain the ground elevation and the aerial survey elevation of the same sampling point.

[0051] According to the ground elevation and the aerial survey elevation of the same sampling point, the integral path length of the aerial survey methane concentration detection device is calculated, and the average aerial survey methane concentration is calculated. The formula is as follows: , , In the formula: is the average aerial survey methane concentration of the sampling point; is the path integral concentration of the aerial survey methane concentration detection device at the sampling point, is the integral path length of the aerial survey methane concentration detection device; is the elevation of the aerial survey takeoff point; is the aerial survey flight altitude; is the ground elevation of this sampling point.

[0052] Then, the Getis-Ord Gi* statistic method is used to analyze the surface methane concentration sampling data of the landfill to obtain the surface hot spot area, and the kernel density estimation method is used to analyze the average aerial survey methane concentration data to obtain the aerial survey hot spot area.

[0053] In this embodiment, the schematic diagram of dual-modal hot spot identification and emission source location is as Figure 5 shown.

[0054] The method for obtaining the surface hot spot area is as follows: calculate the weighted neighborhood sum for each ground sampling point; calculate the global mean and standard deviation; iteratively calculate the Gi* value of each ground sampling point; convert the Gi* value of each ground sampling point into a Z score; and obtain the surface hot spot area according to the actual evaluation requirements of the Z score.

[0055] In this embodiment, the grading of the Z-score is as follows: Z ≥ 2.58: 99% confidence hot spot; Z ≥ 1.96: 95% confidence hot spot; Z ≤ -1.96: significant cold area.

[0056] When calculating the Getis-Ord Gi* statistic, it is necessary to set an appropriate neighborhood range according to the distribution density of the ground data to improve the accuracy of the analysis. For example, adjust the neighborhood size according to the distribution density of the ground data. The formula is as follows: , In the formula, is the spatial weight between feature i and j ; is the attribute value of feature j ; is the neighborhood weighted sum; is the global mean; is the global standard deviation; is the total sample, that is, the total number of methane concentration data points collected by aerial survey.

[0057] The method for obtaining the aerial survey hot spot area is as follows: Since the drone data has high resolution and many sampling points, the kernel density estimation method can be used to calculate the spatial density. The kernel density estimation method itself is a smoothing density estimation method, which can help identify local concentration areas and is suitable for the high-resolution characteristics of drone data. In the kernel density estimation method, a Gaussian kernel is used, and its expression is: , , In the formula, is the kernel function, indicating the density contribution intensity of the data point to the surrounding positions; is the standardized distance; is the bandwidth; is the target position; is the data point position; Select the bandwidth according to Silverman's rule , and the expression is: , In the formula, is the bandwidth; IQR is the difference between the upper quartile (Q3) and the lower quartile (Q1) of the data; is the standard deviation; is the total number of methane concentration data points collected by aerial survey; For each grid point x , calculate the density contribution of its surrounding points: , In the formula, represents the estimated methane concentration density at the spatial position ; is the total number of methane concentration data points collected by aerial survey; For the calculated spatial density values, aerial survey hot spot areas are determined based on empirical quantiles. For example, the top 5% of the density values are used as the hot spot threshold.

[0058] Next, the results of the surface hot spot area and the aerial survey hot spot area are mapped into the three-dimensional model of the landfill. By calculating the local Jaccard coefficient, the methane emission source area is screened out.

[0059] The screening method for the methane emission source area includes: Generate binary rasters for both the results of the surface hot spot area and the aerial survey hot spot area to obtain the ground hot spot raster and the aerial survey hot spot raster; Use the vector polygon file to define the boundary of the landfill; Make the resolutions, coordinate systems, and spatial extents of the ground hot spot raster and the aerial survey hot spot raster consistent; Using the boundary of the landfill as a mask, crop the ground hot spot raster and the aerial survey hot spot raster to exclude interference from external areas; Select the grid size according to the hot spot scale; Generate a regular grid covering the landfill; For each grid cell, count the number of aerial survey hot spot pixels and the number of overlapping pixels , and calculate the local Jaccard coefficient to quantify the degree of overlap between the two. The calculation formula is as follows: , In the formula, is the Jaccard coefficient, is the set of aerial survey hot spot pixels within the grid ; is the set of ground hot spot pixels within the grid ; Evaluate the spatial consistency of the ground hot spots within the range of the aerial survey hot spots based on the Jaccard coefficient, and screen out the methane emission source area.

[0060] In this embodiment, the evaluation of the spatial consistency of the ground hot spots within the range of the aerial survey hot spots can be represented by a heat map, and the specific content is shown in Table 1.

[0061] Table 1 Heat Map Interpretation Rules Jaccard value Color Explanation Measures <![CDATA J i ≥0.7]]> Dark red Ground data highly supports UAV hotspots (strong consistency) Select all UAV hotspot areas as the areas for methane flux quantification <![CDATA 0.4≤ J i <0.7]]> Orange Ground data partially supports UAV hotspots (medium consistency) Select the overlapping area of ground hotspots and UAV hotspots as the methane flux quantification area <![CDATA J i <0.4]]> Blue Ground data insufficiently supports UAV hotspots (low consistency) Ignore and do not participate in the analysis

[0062] According to the actual situation of the landfill, the methane emission source areas can be supplemented. Due to complex terrain, it may be difficult for ground monitoring to cover these potential emission source areas, which is very likely to lead to missed judgment of ground hot spots. The geographical location information of potential emission sources in the landfill, including pumping wells, gas collection wells and drainage pipes, can be marked by combining on-site surveys and landfill operation information. When the potential emission source area coincides with the aerial survey hot spot area, this area is considered as a methane emission source. Since aerial survey monitoring is comprehensive, all aerial survey hot spot areas can be selected as the areas for the next step of methane flux quantification.

[0063] Finally, collect the environmental meteorological parameters of the landfill, and combine the methane emission source areas, the corresponding surface methane concentration sampling data and the aerial survey average methane concentration data to calculate the methane emission flux by the mass balance method.

[0064] The idea of the mass balance method is as follows: Based on the measured spatial methane concentration distribution and meteorological parameters such as wind speed, the methane emissions of each emission source area are obtained by integrating the methane flux on the control surface; finally, the emissions of different source areas are superimposed to accurately quantify the overall methane emissions of the landfill.

[0065] In this embodiment, the schematic diagram of methane emission flux calculation is as Figure 6 shown.

[0066] The calculation method of methane emission flux is as follows: Combine the measured methane concentration distribution and the simultaneously obtained environmental meteorological parameters of the landfill, and use the mass balance method to calculate the methane emission flux. The calculation formula is as follows: , In the formula, F is the emission rate of the emission source; H is the integration height of the plane perpendicular to the wind direction; W is the integration width of the plane perpendicular to the wind direction; u is the wind speed perpendicular to the aerial survey plane; is the methane concentration signal enhancement value, with the upwind test value as the background value , and the downwind test value minus the background value is recorded as the methane concentration signal enhancement value.

[0067] In this embodiment, the methane emission flux quantification area is based on the screened methane emission source areas. For the areas, all UAV hot spot areas are selected as the areas for methane flux quantification; for the areas, the overlapping area of the ground hot spot and the UAV hot spot is selected as the methane flux quantification area; for the supplemented methane emission sources, all UAV hot spot areas are selected as the areas for methane flux quantification.

[0068] In this embodiment, the UAV aerial survey uses a laser methane detector based on tunable diode laser absorption spectroscopy (TDLAS) technology. Since the vertical column concentration of CH4 is detected, it is not necessary to integrate the vertical range of the emission plume when calculating the emission amount. The flux calculation formula is as follows: , where: F is the emission rate of the emission source, g / s; W is the integration width of the plane perpendicular to the wind direction, m; u is the wind speed in the vertical aerial survey plane, m / s; is the enhanced value of the methane column concentration signal, ppm. Usually, the upwind test value is used as the background value , and the downwind test value and the background value The difference is recorded as the enhanced value of the methane column concentration signal.

[0069] Import the methane concentration distribution data sampled by the UAV aerial survey into geographic information processing software such as Arcgis pro. Through co-kriging interpolation by combining the terrain elevation data and the methane concentration distribution data, obtain the global methane concentration distribution map of the landfill. Map and screen the methane emission source area into the methane concentration distribution map of the landfill. Determine the upwind and downwind profiles and wind speeds of the methane emission source area during the aerial survey period through the meteorological data during the aerial survey period. Take 5 pairs of upwind and downwind profiles with the same length at a certain interval, such as 5m, and carry out calculations by the mass balance method. Take the average value as the methane emission flux of this area.

[0070] Superimpose the methane emission fluxes of all methane emission source areas, which is the total methane emission of the entire landfill. Embodiment 2

[0071] A landfill methane emission monitoring system for combined air and ground monitoring, the architecture diagram is as Figure 7 shown, and it is composed of a landfill three-dimensional model construction module, a surface methane concentration sampling data acquisition module, an aerial survey methane concentration distribution data acquisition module, an aerial survey average methane concentration data calculation module, a hot spot area acquisition module, a methane emission source area screening module, and a methane emission flux calculation module.

[0072] The landfill three-dimensional model construction module is used to construct a landfill three-dimensional model based on the aerial survey point cloud data and image data obtained from the aerial survey of the landfill area.

[0073] The surface methane concentration sampling data acquisition module is used to select a number of ground sampling points based on the landfill three-dimensional model, combined with the terrain characteristics of the landfill, possible emission hot spot areas, and historical operation information, and conduct ground sampling of methane emissions according to the ground sampling points to obtain the surface methane concentration sampling data of the landfill.

[0074] An aerial survey methane concentration distribution data acquisition module, which is used to determine the aerial survey height and the aerial survey route area of methane emissions based on the three-dimensional model of the landfill and several selected ground sampling points, and acquire the aerial survey methane concentration distribution data above the landfill.

[0075] An aerial survey average methane concentration data calculation module, which is used to spatially register the surface methane concentration sampling data and the aerial survey methane concentration distribution data based on the three-dimensional model of the landfill according to the longitude and latitude coordinates of the aerial survey sampling points, obtain the ground elevation and the aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data.

[0076] A hot spot area acquisition module, which is used to analyze the surface methane concentration sampling data of the landfill by using the Getis-Ord Gi* statistic method to obtain the surface hot spot area, and analyze the aerial survey average methane concentration data by using the kernel density estimation method to obtain the aerial survey hot spot area.

[0077] A methane emission source area screening module, which is used to map the results of the surface hot spot area and the aerial survey hot spot area into the three-dimensional model of the landfill, and screen the methane emission source area through the calculation of the local Jaccard coefficient.

[0078] A methane emission flux calculation module, which is used to collect and obtain the environmental meteorological parameters of the landfill, and calculate the methane emission flux by using the mass balance method based on the methane emission source area and its corresponding surface methane concentration sampling data and aerial survey average methane concentration data.

[0079] The specific implementation manners of each module in this system are the same as those described in Embodiment 1, and will not be elaborated here. Embodiment 3

[0080] An electronic device, including: a memory and a processor, which are communicatively connected to each other, the memory stores computer instructions, and the processor realizes a method for monitoring methane emissions from a landfill by joint air and ground monitoring as described in Embodiment 1 above, and a system for monitoring methane emissions from a landfill by joint air and ground monitoring as described in Embodiment 2 by executing the computer instructions. Embodiment 4

[0081] A computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, it realizes a method for monitoring methane emissions from a landfill by joint air and ground monitoring as described in Embodiment 1 above, and a system for monitoring methane emissions from a landfill by joint air and ground monitoring as described in Embodiment 2.

[0082] 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 take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code. The solutions in the embodiments of the present application can be implemented in various computer languages. For example, object-oriented programming languages such as Java, C++, Python, and the interpreted scripting language JavaScript, etc.

[0083] The present application is described with reference to the flowcharts and / or block diagrams of methods, electronic devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing electronic devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing electronic devices generate a device for implementing the functions specified in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0084] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing electronic devices to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0085] These computer program instructions can also be loaded onto a computer or other programmable data processing electronic devices, such that a series of operation steps are executed on the computer or other programmable electronic devices to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable electronic devices provide steps for implementing the functions specified in Figure 1 one or more flows and / or blocks Figure 1 one or more blocks.

[0086] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments as well as all changes and modifications that fall within the scope of the present application.

[0087] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. A landfill methane emission monitoring method with open-air and ground joint monitoring, characterized in that: include: Based on the aerial survey point cloud data and image data obtained from the aerial survey of the landfill area, a three-dimensional model of the landfill is constructed; Based on the three-dimensional model of the landfill, combined with the landfill's topographical features, possible emission hotspots, and historical operation information, several ground sampling points were selected, and ground sampling of methane emissions was carried out based on the ground sampling points to obtain the surface methane concentration sampling data of the landfill; Based on the three-dimensional model of the landfill and several selected ground sampling points, the aerial survey altitude and flight route area for aerial sampling of methane emissions were determined to obtain aerial survey methane concentration distribution data over the landfill; Based on the three-dimensional model of the landfill, the surface methane concentration sampling data and the aerial survey methane concentration distribution data are spatially registered according to the latitude and longitude coordinates of the aerial survey sampling points, the ground elevation and aerial survey elevation of the same sampling point are obtained, and the aerial survey average methane concentration data is calculated; The Getis-Ord Gi* statistic method was used to analyze the surface methane concentration sampling data of the landfill to obtain the surface hotspot areas, and the kernel density estimation method was used to analyze the aerial survey average methane concentration data to obtain the aerial survey hotspot areas; The results of the surface hot spots and aerial survey hot spots were mapped to the three-dimensional model of the landfill, and the methane emission source areas were screened out by calculating the local Jaccard coefficient. The environmental meteorological parameters of the landfill were collected and acquired, and the methane emission flux was calculated by the mass balance method based on the methane emission source area and its corresponding surface methane concentration sampling data and the average methane concentration data from aerial surveys.

2. The method for monitoring methane emissions from landfills by combined open-air and ground monitoring according to claim 1 is characterized by: Data preprocessing is performed on the surface methane concentration sampling data of the landfill and the aerial survey methane concentration distribution data over the landfill: in the case of random missing data, interpolation method is used to supplement or directly delete the data; systematic missing data caused by sampling and detection equipment failure are marked during statistics, and re-sampling and monitoring are carried out if necessary; outliers are marked and eliminated using statistical methods including 3 times the standard deviation, box plot method or threshold setting based on common sense of physical background.

3. The method for monitoring methane emissions from landfills by joint monitoring of open space and land according to claim 1 is characterized by: The method for spatially registering the surface methane concentration sampling data and the aerial survey methane concentration distribution data comprises: based on the three-dimensional model of the landfill, obtaining the digital elevation model of the landfill through aerial survey software; using the same spatial coordinate system for the ground sampling and aerial sampling of methane emissions, matching the longitude and latitude coordinates of the aerial survey sampling points in the digital elevation model of the landfill, and obtaining the ground elevation and aerial survey elevation of the same sampling point; According to the ground elevation and aerial survey elevation of the same sampling point, the integral path length of the aerial survey methane concentration detection equipment is calculated, and the average aerial survey methane concentration is calculated. The formula is as follows: ， ， Where: is the average methane concentration of the sampling points from aerial surveys; It is the path-integrated concentration of the aerial methane concentration detection equipment at the sampling point; It is the integral path length of the aerial methane concentration detection equipment; The altitude of the take-off point for aerial survey; To measure the flight altitude; is the ground elevation of the sampling point.

4. The method for monitoring methane emissions from landfills by combined open-air and ground monitoring according to claim 3 is characterized by: The method for obtaining the surface hotspot area includes: calculating the weighted neighborhood sum for each ground sampling point; calculating the global mean and standard deviation; iteratively calculating the Gi* value of each ground sampling point; converting the Gi* value of each ground sampling point into a Z score; and obtaining the surface hotspot area according to the actual evaluation requirements of the Z score; When calculating the Getis-Ord Gi* statistic, it is necessary to set an appropriate neighborhood range based on the distribution density of the ground data. The formula is as follows: ， In the formula, It is an element i and j The spatial weight between For elements j Attribute value of is the weighted sum of the neighborhood; is the global mean; is the global standard deviation; is the total sample, i.e. the total number of methane concentration data points collected by aerial survey; The method for obtaining the aerial survey hotspot area includes: applying a kernel density estimation method to calculate the spatial density, using a Gaussian kernel, and its expression is: ， ， In the formula, is the kernel function, which indicates the density contribution intensity of the data point to the surrounding positions; is the standardized distance; is bandwidth; is the target location; is the data point location; Selecting bandwidth based on Silverman's law , the expression is: ， In the formula, is the bandwidth; IQR is the difference between the upper quartile (Q3) and the lower quartile (Q1) of the data; is the standard deviation; The total number of methane concentration data points collected for the aerial survey; For each grid point , calculate the density contribution of its surrounding points: ， In the formula, It indicates the position in space Estimated methane concentration density at ; The total number of methane concentration data points collected for the aerial survey; For the calculated spatial density values, aerial survey hot spots are determined based on empirical quantiles.

5. The method for monitoring methane emissions from landfills by combined open-air and ground monitoring according to claim 4 is characterized by: The method for screening the methane emission source area includes: Generate binary rasters from the surface hotspot area results and the aerial survey hotspot area results to obtain ground hotspot rasters and aerial survey hotspot rasters; Define the boundaries of the landfill using vector polygon files; Make the resolution, coordinate system, and spatial range of the ground hotspot grid consistent with the aerial survey hotspot grid; Using the landfill boundary as a mask, the ground hotspot grid and the aerial survey hotspot grid were clipped to eliminate interference from external areas; Select the grid size based on the hotspot scale; Generate a regular grid covering the landfill; For each grid cell, count the number of aerial survey hotspot pixels and the number of overlapping pixels , the local Jaccard coefficient is calculated to quantify the degree of overlap between the two. The calculation formula is as follows: ， In the formula, is the Jaccard coefficient, For Grid Aerial survey hotspot pixel collection within; For Grid The ground hotspot pixel set within; The spatial consistency of ground hotspots within the aerial survey hotspots was evaluated based on the Jaccard coefficient, and the methane emission source areas were screened out.

6. The method for monitoring methane emissions from landfills by combined open-air and ground monitoring according to claim 5 is characterized by: The calculation method of the methane emission flux is: Combining the measured methane concentration distribution and the environmental meteorological parameters of the landfill obtained simultaneously, the mass balance method is used to calculate the methane emission flux. The calculation formula is as follows: ， Where, F is the emission rate of the emission source; H is the integrated height of the plane perpendicular to the wind direction; W is the integrated width of the plane perpendicular to the wind direction; u is the wind speed of the vertical aerial survey plane; is the CH4 concentration signal enhancement value, and the above wind direction test value is the background value , the following wind direction test values With background value The difference is recorded as the CH4 concentration signal enhancement value.

7. The method for monitoring methane emissions from landfills by combined open-air and ground monitoring according to claim 1 is characterized by: Use a portable methane analyzer to conduct ground sampling of methane emissions from landfills. Use a drone equipped with a laser methane concentration detector to conduct aerial sampling of methane emissions from landfills. Use a drone equipped with an airborne meteorological instrument to collect and obtain the environmental meteorological parameters of the landfill.

8. A landfill methane emission monitoring system for joint monitoring of open space and land, implementing the method of any one of claims 1 to 7, characterized in that: It includes a landfill three-dimensional model construction module, a surface methane concentration sampling data acquisition module, an aerial survey methane concentration distribution data acquisition module, an aerial survey average methane concentration data calculation module, a hot spot area acquisition module, a methane emission source area screening module, and a methane emission flux calculation module; The landfill three-dimensional model construction module is used to construct a three-dimensional model of the landfill based on the aerial survey point cloud data and image data obtained by aerial survey of the landfill area; The surface methane concentration sampling data acquisition module is used to select a number of ground sampling points based on the three-dimensional model of the landfill, combined with the landfill's terrain features, possible emission hot spots, and historical operation information, and perform ground sampling of methane emissions based on the ground sampling points to obtain the surface methane concentration sampling data of the landfill; The aerial survey methane concentration distribution data acquisition module is used to determine the aerial survey altitude and aerial survey route area for aerial sampling of methane emissions based on the three-dimensional model of the landfill and a number of selected ground sampling points, and to obtain aerial survey methane concentration distribution data over the landfill; The aerial survey average methane concentration data calculation module is used to spatially align the surface methane concentration sampling data and the aerial survey methane concentration distribution data based on the three-dimensional model of the landfill and the longitude and latitude coordinates of the aerial survey sampling points, obtain the ground elevation and aerial survey elevation of the same sampling point, and calculate the aerial survey average methane concentration data; The hotspot area acquisition module is used to analyze the surface methane concentration sampling data of the landfill using the Getis-Ord Gi* statistic method to obtain the surface hotspot area, and to analyze the aerial survey average methane concentration data using the kernel density estimation method to obtain the aerial survey hotspot area; The methane emission source area screening module is used to map the results of the surface hot spot area and the aerial survey hot spot area to the three-dimensional model of the landfill, and screen the methane emission source area by calculating the local Jaccard coefficient; The methane emission flux calculation module is used to collect and obtain the environmental meteorological parameters of the landfill, and calculate the methane emission flux through the mass balance method based on the methane emission source area and its corresponding surface methane concentration sampling data and the aerial survey average methane concentration data.

9. An electronic device, characterized in that: include: A memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor implements a landfill methane emission monitoring method with air-ground joint monitoring as described in any one of claims 1-7 by executing the computer instructions.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for monitoring methane emissions from a landfill by combined air-ground monitoring as described in any one of claims 1 to 7 is implemented.

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