Numerical prediction method and system for heavy metal pollution load evolution in drainage basin

Abstract

The invention discloses a numerical prediction method and system for heavy metal pollution load evolution in a drainage basin, and belongs to the technical field of drainage basin heavy metal pollution prevention. According to an existing drainage basin pollution prediction scheme, the influence of heavy metal pollution leaching from soil due to rainfall and the influence of atmospheric heavy metal pollution sedimentation are not considered, so that the conversion and transportation processes of heavy metal pollution cannot be accurately simulated. According to the numerical prediction method for heavy metal pollution load evolution in the drainage basin, heavy metal multi-dimensional evolution data is obtained by constructing a heavy metal parameter analysis model, a heavy metal three-dimensional evolution model and a heavy metal coupling prediction model; then the heavy metal multi-dimensional evolution data, weather data and hydrological calculation data are subjected to coupling calculation to obtain an accurate heavy metal pollution prediction value, so that the evolution process of heavy metal pollution between water, land and air can be accurately simulated; and the development trend of the heavy metal pollution load in the drainage basin can be tracked and predicted more comprehensively.

Description

Technical Field

[0001] The present invention relates to a numerical prediction method and system for the evolution of heavy metal pollution load in a basin, belonging to the technical field of basin heavy metal pollution prevention. Background Art

[0002] Currently, the main means for preventing and controlling heavy metal pollution in basin water bodies is data monitoring, which has a certain lag and is difficult to provide an intuitive reference for the future development trend of heavy metal pollution load.

[0003] In a Chinese document (Liu Kejia. Application Research on the Improved SWAT Model in Simulating the Antimony Pollution Load in the Soil-Water Interface Flow of an Antimony Mining Area [D]. Hunan University of Science and Technology, 2015.), on-site investigations were carried out on the characteristics of the environment in the study area, and then a sampling plan for the study area was formulated, and an SWAT model was constructed to consider the vertical and horizontal diffusion of heavy metals in the soil-water interface flow, and a two-dimensional or three-dimensional migration and transformation model was constructed to improve the accuracy of the transformation mechanism. Finally, the model was adjusted and optimized to simulate the pollution load of heavy metal antimony in the soil-water interface of the antimony mining area, providing a theoretical basis for the assessment and prevention of antimony pollution in the study area.

[0004] Although the above solution considers the heavy metal pollution exchange at the soil-water interface, it does not consider the influence of heavy metals in terrestrial soil and atmospheric heavy metal pollution on the migration of the basin, and cannot comprehensively simulate the transformation and transport process of heavy metal pollution, resulting in difficulty in fully calculating the influence of heavy metal pollution load in actual calculations. Therefore, the existing solution cannot accurately simulate the transformation and transport process of heavy metal pollution, cannot accurately predict the change of heavy metal pollution load, and is not conducive to the prevention and management of heavy metal pollution in basin water bodies.

[0005] The information disclosed in this background art is only used to understand the background of the inventive concept of the present invention, and thus it may include information that does not constitute prior art. Summary of the Invention

[0006] In view of the above problems or one of the above problems, one object of the present invention is to provide a numerical prediction method and system for the evolution of heavy metal pollution load in a basin, which fully considers the migration and transformation laws of heavy metal pollution among water bodies, terrestrial soils, and the air. By constructing a heavy metal pollution collection model, a heavy metal parameter analysis model, a three-dimensional evolution model of heavy metals, and a heavy metal coupling prediction model, the heavy metal transformation property parameters and multi-dimensional evolution data of heavy metals among land, water, and air are obtained. Then, the multi-dimensional evolution data of heavy metals are coupled with weather data and hydrological calculation data to calculate the heavy metal leaching amount leached from the soil due to rainfall, the heavy metal load values deposited from the atmosphere to the soil and water bodies, etc. Then, combined with the emissions from heavy metal pollution point sources, the transformation and transport processes of heavy metal pollution are accurately simulated, so that accurate heavy metal pollution prediction values can be obtained, which is beneficial to the prevention and management of heavy metal pollution in the basin and is applicable to the tracking and simulation of heavy metal pollution load in the basin.

[0007] In view of the above problems or one of the above problems, another object of the present invention is to provide a numerical prediction method and system for the evolution of heavy metal pollution load in a basin, which fully considers the exchange characteristics of heavy metal pollution at the land-water-air interface and accurately simulates the evolution process of heavy metal pollution among land, water, and air based on weather changes and hydrological calculations. Thus, the numerical simulation of the spatio-temporal distribution of heavy metal pollution load in the basin can be comprehensively carried out, and therefore, the development trend of heavy metal pollution load in the basin can be more comprehensively tracked and predicted.

[0008] To achieve one of the above objects, the first technical solution of the present invention is as follows: A numerical prediction method for the evolution of heavy metal pollution load in a basin, comprising the following steps: Collect the heavy metal pollution data of land, water, and air in the basin to be predicted through a pre-constructed heavy metal pollution collection model; Use a pre-constructed heavy metal parameter analysis model to process the heavy metal pollution data of land, water, and air to obtain heavy metal transformation property parameters; Use a pre-constructed three-dimensional evolution model of heavy metals to simulate the process of heavy metals leaching from the soil due to rainfall, the process of heavy metal deposition in the atmosphere, and the process of changes in heavy metal load in water bodies respectively based on the heavy metal transformation property parameters, and obtain multi-dimensional evolution data of heavy metals, which are used to characterize the migration and changes of heavy metals among land, water, and air; Adopt a pre-constructed heavy metal coupling prediction model to perform coupling calculations on the multi-dimensional evolution data of heavy metals, weather data, and hydrological calculation data to calculate the evolution process of heavy metal pollution among land, water, and air, and obtain heavy metal pollution prediction values.

[0009] The present invention fully considers the migration and transformation laws of heavy metal pollution among water bodies, terrestrial soils, and the air. By constructing a heavy metal pollution collection model, a heavy metal parameter analysis model, a three-dimensional evolution model of heavy metals, and a coupled prediction model of heavy metals, the heavy metal transformation property parameters and multi-dimensional evolution data of heavy metals among water, land, and air are obtained. Then, the multi-dimensional evolution data of heavy metals are coupled with weather data and hydrological calculation data to obtain data such as the leaching amount of heavy metals leached from the soil due to rainfall and the heavy metal load values deposited from the atmosphere to the soil and water bodies. Then, combined with the emissions from heavy metal pollution point sources, the transformation and transport processes of heavy metal pollution are accurately simulated, so that accurate heavy metal pollution prediction values can be obtained, which is conducive to the prevention and management of heavy metal pollution in the basin water body.

[0010] Furthermore, the present invention fully considers the exchange characteristics of heavy metal pollution at the water-land-air interface, and accurately simulates the evolution process of heavy metal pollution among water, land, and air based on weather changes and hydrological calculations. Thus, the numerical simulation of the spatio-temporal distribution of heavy metal pollution load in the basin can be comprehensively carried out, and therefore the development trend of heavy metal pollution load in the basin can be more comprehensively tracked and predicted.

[0011] As a preferred technical measure: The method for collecting water-land-air heavy metal pollution data in the basin to be predicted through a pre-constructed heavy metal pollution collection model is as follows: Obtain the location information of the basin to be predicted; Based on the location information of the basin to be predicted, collect the point source emission data of heavy metal pollution in the basin to be predicted; The point source emission data includes at least the point source location, basin runoff, basin sediment load, and heavy metal load; According to the point source emission data, based on the daily load constant method, construct a point source emission database; Based on the location information of the basin to be predicted, collect the heavy metal pollution content data in the air and soil of the basin; The heavy metal pollution content data includes the monthly average soil heavy metal load and the monthly average atmospheric heavy metal load in the basin range; According to the heavy metal pollution content data, based on the monthly average load constant method, construct an air-land pollution database; Summarize the point source emission database and the air-land pollution database to form water-land-air heavy metal pollution data as the heavy metal load input for numerical calculation.

[0012] As a preferred technical measure: The method for processing water-land-air heavy metal pollution data by using a pre-constructed heavy metal parameter analysis model to obtain heavy metal transformation property parameters is as follows: According to the heavy metal pollution data on land, water, and air, obtain the types of heavy metals, soil types, longitudinal diffusion coefficients of heavy metals, measured adsorption coefficients, sediment-water distribution coefficients, and dry-wet conditions; Based on the types of heavy metals, longitudinal diffusion coefficients of heavy metals, measured adsorption coefficients, and sediment-water distribution coefficients, determine the desorption coefficients of heavy metals and the distribution coefficients of heavy metals in suspended solids and water bodies; Using the desorption coefficients of heavy metals and the distribution coefficients of heavy metals in suspended solids and water bodies, calculate the comprehensive sedimentation velocity of heavy metals, the comprehensive sedimentation influence constant, and the resuspension coefficient; Based on the types of heavy metals, soil types, and the usage rules of pesticides and fertilizers, determine the soil heavy metal content and the usage information of pesticides and fertilizers; Summarize the types of heavy metals, soil types, longitudinal diffusion coefficients of heavy metals, measured adsorption coefficients, sediment-water distribution coefficients, dry-wet conditions, desorption coefficients of heavy metals, distribution coefficients of heavy metals in suspended solids and water bodies, comprehensive sedimentation velocity of heavy metals, comprehensive sedimentation influence constant, resuspension coefficient, equation parameters, soil heavy metal content, and usage information of pesticides and fertilizers to obtain heavy metal transformation property parameters.

[0013] As an optimal technical measure: The method for simulating the leaching process of heavy metals from soil due to rainfall based on heavy metal transformation property parameters using a pre-constructed three-dimensional evolution model of heavy metals is as follows: Based on heavy metal transformation property parameters, obtain the soil heavy metal content and the usage information of pesticides and fertilizers; According to the soil heavy metal content, the usage information of pesticides and fertilizers, the equivalent rainfall duration, and multiple unknown variable parameters, construct a heavy metal rainfall leaching equation; Use the heavy metal rainfall leaching equation to fit the leaching amount data of soil heavy metals under different rainwater pH values and multiple groups of rainfall durations to obtain a fitting result; According to the fitting result, determine the values of variable parameters under different rainwater pH values; Summarize the values of variable parameters for different rainwater pH values, and then use an exponential function for fitting to obtain a fitting function of the variable with respect to pH; Substitute the fitting function of the variable with respect to pH into the heavy metal rainfall leaching equation to form a calculation formula for the leaching amount of heavy metals with respect to rainfall duration and rainwater pH, thereby realizing the simulation of the leaching process of heavy metals from soil due to rainfall.

[0014] As an optimal technical measure: The method for simulating the atmospheric heavy metal sedimentation process is as follows: Based on heavy metal transformation property parameters, determine the types of heavy metals, soil types, and dry-wet conditions; Determine the heavy metal deposition information according to the types of heavy metals, soil types, and wet and dry conditions; The heavy metal deposition information includes the heavy metal content of wet deposition, the heavy metal content of dry deposition, the wet deposition rate, and the dry deposition rate; Based on rainfall conditions and air pressure information, obtain the actual air pressure and the reference air pressure; Take the ratio of the actual air pressure to the reference air pressure as the air pressure factor; Based on rainfall conditions and average wind speed information, obtain the reference average wind speed and the actual average wind speed; Take the ratio of the reference average wind speed to the actual average wind speed as the wind speed factor; According to the heavy metal deposition information, the air pressure factor, and the wind speed factor, construct the calculation formulas for the wet deposition flux and the dry deposition flux of heavy metals; Jointly solve the calculation formulas for the wet deposition flux and the dry deposition flux of heavy metals to obtain the load of heavy metals deposited from the atmosphere to the soil and water bodies, and realize the simulation of the atmospheric heavy metal deposition process.

[0015] Furthermore, the method for simulating the change process of heavy metal load in water bodies using a pre-constructed three-dimensional evolution model of heavy metals based on heavy metal transformation property parameters is as follows: Collect the meteorological data of meteorological stations in the basin. The meteorological data includes the annual maximum wind speed, the daily maximum rainfall, and the monthly rainfall observation values; Calculate the soil moisture and precipitation of a certain water area according to the annual maximum wind speed, the daily maximum rainfall, and the monthly rainfall observation values; Based on the soil moisture and precipitation of a certain water area, use a pre-constructed hydrological calculation model to calculate the hydrological calculation data; the hydrological calculation data includes at least the soil water content, the basin flow velocity, the cross-sectional area of flow, and the basin water depth; Determine the mass concentration of dissolved heavy metals and the mass concentration of suspended heavy metals according to the heavy metal transformation property parameters, the hydrological calculation data, and the heavy metal pollution data in the water, land, and air; Based on the mass concentration of dissolved heavy metals, the mass concentration of suspended heavy metals, the basin water depth, the longitudinal component of the water body section flow velocity, and the cross-sectional average flow velocity, construct a heavy metal evolution equation; Set the initial heavy metal concentration at the initial time of the basin and the heavy metal concentration boundary conditions regarding the basin boundary; The heavy metal concentration boundary condition is the time series of the heavy metal concentration; According to the initial heavy metal concentration, the heavy metal concentration boundary conditions, the grid size, and the time step, discretize the heavy metal evolution equation using the implicit difference method to obtain the implicit difference expression of the heavy metal concentration, which is used to characterize the heavy metal mass concentration at a certain moment of the nodes in the basin to be predicted; Based on the convective-diffusion characteristics, the implicit difference expression of heavy metal concentration is deformed to obtain a transformed prediction calculation equation set for calculating the heavy metal mass concentration; By superimposing solutes, the mass concentration source term of dissolved heavy metals and the mass concentration source term of suspended heavy metals are combined into the transformed prediction calculation equation set, thereby constructing an overall prediction calculation equation set, enabling the simultaneous consideration of the mass concentrations of point-source and non-point-source heavy metals during the calculation process; The overall prediction calculation equation set is written in the form of a tridiagonal matrix and solved using the chasing method to obtain the heavy metal mass concentration values of each phase at each moment for each watershed node; The heavy metal mass concentration values of each phase at multiple moments for several watershed nodes are summarized to obtain the heavy metal load information of the water body, which is used to characterize the distribution evolution and component transformation process of heavy metal pollution loads in the watershed, so as to realize the simulation of the change process of water body heavy metal loads.

[0016] As a preferred technical measure: It also includes using a pre-constructed three-dimensional evolution model of heavy metals to simulate the process of biological deduction and reduction of heavy metals based on heavy metal transformation property parameters, and the method is as follows: According to the soil type and the geographical location of the watershed to be predicted, determine the vegetation cover type; According to the vegetation cover type and heavy metal transformation property parameters, obtain the absorption ratio of biological uptake of soil heavy metals and the filtration reduction ratio of biological filtration of atmospheric heavy metal deposition; According to the absorption ratio and the filtration reduction ratio, determine the biological deduction and reduction amount of heavy metals to realize the simulation of the process of biological deduction and reduction of heavy metals.

[0017] As a preferred technical measure: The method for obtaining the heavy metal pollution prediction value is as follows: Substitute the rainfall data of the watershed to be predicted into the calculation formula of heavy metal leaching amount with respect to rainfall duration and rainwater pH value to obtain the heavy metal leaching amount of the watershed to be predicted; According to the atmospheric heavy metal deposition process, determine the calculation formulas for wet deposition flux and dry deposition flux of heavy metals; Based on the meteorological information of the watershed to be predicted and the area of the watershed to be predicted, and combined with the calculation formulas for wet deposition flux and dry deposition flux of heavy metals, calculate the deposition load values of heavy metals deposited from the atmosphere to the soil and water body; Use the point-source emission data of heavy metals as new heavy metal pollution data for land, water and air; Substitute the new heavy metal pollution data of land, water and air and hydrological calculation data into the process of water body heavy metal load change, and by superimposing solutes, combine the mass concentration source term of dissolved heavy metals and the mass concentration source term of suspended heavy metals into the transformation prediction calculation equation system, so as to construct the overall prediction calculation equation system; Solve the overall prediction calculation equation system to obtain the heavy metal mass concentration at each moment in the basin, that is, the heavy metal pollution prediction value, which is used to characterize the distribution evolution and component transformation process of heavy metal pollution load in the water body.

[0018] Furthermore, the rainfall data includes rainfall duration and rainwater pH value. The meteorological information includes rainfall conditions, actual air pressure value, actual average wind speed value; the point source emission data of heavy metals includes point source emission data of heavy metal leaching, point source emission data of sedimentation load, and point source emission data of heavy metal pollution.

[0019] Furthermore, the method for determining the calculation formula of heavy metal leaching amount with respect to rainfall duration and rainwater pH value is as follows: Based on the multi-dimensional evolution data of heavy metals, determine the process of heavy metal leaching from the soil due to rainfall, the process of atmospheric heavy metal deposition, and the process of water body heavy metal load change; Collect the meteorological data of meteorological stations in the basin. The meteorological data includes the rainfall duration, rainwater pH value, actual air pressure value, actual average wind speed value, annual maximum wind speed, daily maximum rainfall, and monthly rainfall observation values of the basin to be predicted; According to the annual maximum wind speed, daily maximum rainfall, and monthly rainfall observation values, calculate the soil moisture and precipitation of the basin to be predicted; Based on the soil moisture and precipitation of the basin to be predicted, use the pre-constructed hydrological calculation model to calculate the hydrological calculation data; the hydrological calculation data includes at least soil water content, basin flow velocity, cross-sectional area of flow, and basin water depth; According to the process of heavy metal leaching from the soil due to rainfall, determine the calculation formula of heavy metal leaching amount with respect to rainfall duration and rainwater pH value.

[0020] As a preferred technical measure: The method for constructing the hydrological calculation model is as follows: Collect the land use classification data of the basin to be predicted; According to the land use classification data, obtain the soil type distribution information and soil property data; Obtain several sub-basins of the basin to be predicted, and according to the soil type distribution information and soil property data, subdivide the sub-basins, and superimpose the soil type distribution information and soil property data to obtain several hydrological calculation units; Each hydrological calculation unit has a single land use type and soil type, and a hydrological variable matrix is established on each hydrological calculation unit; According to the water area information, a number of river calculation units are constructed, and a river runoff variable matrix is set on each river calculation unit for river evolution calculation and heavy metal load transfer calculation; A number of hydrological calculation units and river calculation units are coupled to obtain a hydrological calculation model, which serves as a carrier for calculating water balance and material transport.

[0021] Furthermore, the land use classification data includes cultivated land information, forest land information, pasture information, industrial land information, residential land information, water area information, and pesticide and fertilizer usage information. The soil property data includes the structure of the soil layer, the available effective moisture in the soil layer, the saturated hydraulic conductivity, the wet density of the soil, the soil erosion factor, and the types and contents of heavy metals in the soil. The hydrological variable matrix is used to store hydrological calculation variables, which includes soil moisture content, rainfall, surface runoff, evaporation, infiltration, groundwater runoff, and heavy metal mass concentration. The river runoff variable matrix includes river runoff, river water volume, and heavy metal mass concentration.

[0022] Furthermore, based on the soil moisture and precipitation of a certain water area, the method for calculating hydrological calculation data using the pre-constructed hydrological calculation model is as follows: Obtain the soil moisture and precipitation of a certain water area, and set the hydrological initial conditions at the initial time of the basin; The hydrological initial conditions include runoff, evaporation, infiltration, and groundwater runoff; Input the soil moisture, precipitation, and hydrological initial conditions into the hydrological calculation model for hydrological simulation, and based on the principle of water balance, simulate the changes in runoff water volume on the surface, in the river, in the soil, and in the groundwater of the basin, so that the water balance between hydrological calculation units is achieved, and thus hydrological calculation data is obtained; the hydrological calculation data includes at least soil moisture content, basin flow velocity, cross-sectional area of flow, and basin water depth.

[0023] As a preferred technical measure: The method for obtaining a number of sub-basins of the basin to be predicted is as follows: Obtain the location information of the basin to be predicted; Based on the location information of the basin to be predicted, obtain the digital elevation data of the basin to be predicted; According to the digital elevation data of the basin to be predicted, obtain the boundary location information with a slope greater than 10%; Determine the boundaries of a number of sub-basins through the boundary location information; Based on the boundaries of the sub-basins and the basin area threshold, determine the sub-basin scope; According to the scope of each sub-basin, determine the outlet of each sub-basin, thereby dividing the entire basin into a number of sub-basins that conform to the basin geographical characteristics and natural runoff and confluence characteristics.

[0024] Furthermore, the method for inputting soil moisture, precipitation, and initial hydrological conditions into a hydrological calculation model for hydrological simulation is as follows: Based on the soil moisture, precipitation, and initial hydrological conditions, and using the surface runoff curve method, calculate the surface runoff volume and infiltration volume; Based on the surface runoff volume and infiltration volume, use the water transfer formula to calculate the soil water content at a certain moment; Through the Manning formula, and according to the cross-sectional hydraulic radius, river channel slope, and roughness coefficient, calculate the flow velocity of the river channel; According to the river water volume, surface runoff volume, and time step, calculate the cross-sectional area of flow; Then, based on the cross-sectional area of flow, river bottom width, and river channel slope, calculate the river depth; Summarize the soil water content, basin flow velocity, cross-sectional area of flow, and basin water depth to obtain hydrological calculation data.

[0025] To achieve one of the above purposes, the second technical solution of the present invention is: A numerical prediction method for the evolution of heavy metal pollution load in a basin, including the following: Through a pre-constructed heavy metal pollution collection model, collect the heavy metal pollution data on land, water, and air in the basin to be predicted; Use a pre-constructed heavy metal parameter analysis model to process the heavy metal pollution data on land, water, and air to obtain heavy metal transformation property parameters; Use a pre-constructed three-dimensional heavy metal evolution model. Based on the heavy metal transformation property parameters, simulate the processes of heavy metal leaching from the soil due to rainfall, atmospheric heavy metal deposition, the process of biological deduction and reduction of heavy metals, and the change process of heavy metal load in water respectively, to obtain three-dimensional heavy metal evolution data, which is used to characterize the migration and change of heavy metals among land, water, air, and organisms; Adopt a pre-constructed heavy metal coupling prediction model to perform coupling calculations on the three-dimensional heavy metal evolution data, weather data, and hydrological calculation data to obtain the heavy metal leaching amount of heavy metal pollution leached from the soil due to rainfall, the heavy metal load values of atmospheric deposition on the soil and water bodies, the deduction and reduction amounts of biological deduction of soil heavy metals and heavy metal deposition, and then combine the emissions of heavy metal pollution point sources to calculate the heavy metal pollution prediction value, so as to comprehensively calculate the evolution process of heavy metal pollution among land, water, air, and organisms.

[0026] The present invention fully considers the migration and transformation laws of heavy metal pollution among water bodies, terrestrial soils, air, and organisms. By constructing a heavy metal pollution collection model, a heavy metal parameter analysis model, a heavy metal three-dimensional evolution model, and a heavy metal coupling prediction model, the heavy metal transformation property parameters and the multi-dimensional evolution data of heavy metals among water, land, air, and organisms are obtained. Then, the multi-dimensional evolution data of heavy metals are coupled with weather data and hydrological calculation data to obtain data such as the leaching amount of heavy metals leached from the soil due to rainfall, the heavy metal load values deposited from the atmosphere to the soil and water bodies, and the deduction and reduction of soil heavy metals and heavy metal deposition by organisms. Then, combined with the emissions of heavy metal pollution point sources, the transformation and transport processes of heavy metal pollution are accurately simulated, so that accurate heavy metal pollution prediction values can be obtained, which is conducive to the prevention and management of heavy metal pollution in the basin water area. Therefore, the development trend of heavy metal pollution load in the basin can be tracked and predicted more comprehensively.

[0027] To achieve one of the above purposes, the third technical solution of the present invention is: A numerical prediction system for the evolution of heavy metal pollution load in a basin, which includes: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned numerical prediction method for the evolution of heavy metal pollution load in a basin.

[0028] To achieve one of the above purposes, the second technical solution of the present invention is: A numerical prediction system for the evolution of heavy metal pollution load in a basin, which includes: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the above-mentioned numerical prediction method for the evolution of heavy metal pollution load in a basin.

[0029] Compared with the prior art solutions, the present invention has the following beneficial effects: The present invention fully considers the migration and transformation laws of heavy metal pollution among water bodies, terrestrial soils, and the air. By constructing a heavy metal pollution collection model, a heavy metal parameter analysis model, a three-dimensional evolution model of heavy metals, and a heavy metal coupling prediction model, the conversion property parameters of heavy metals and the multi-dimensional evolution data of heavy metals among land, water, and air are obtained. Then, the multi-dimensional evolution data of heavy metals are coupled with weather data and hydrological calculation data to obtain data such as the leaching amount of heavy metals leached from the soil due to rainfall and the heavy metal load values deposited from the atmosphere to the soil and water bodies. Then, combined with the emissions of heavy metal pollution point sources, the conversion and transport processes of heavy metal pollution are accurately simulated, so that accurate heavy metal pollution prediction values can be obtained, which is conducive to the prevention and management of heavy metal pollution in river basin water bodies.

[0030] Furthermore, the present invention fully considers the exchange characteristics of heavy metal pollution at the water-land-air biotic interface, and accurately simulates the evolution process of heavy metal pollution among water, land, and air based on weather changes and hydrological calculations. Thus, the numerical simulation of the spatio-temporal distribution of heavy metal pollution load in the river basin can be comprehensively carried out, and therefore, the development trend of heavy metal pollution load in the river basin can be more comprehensively tracked and predicted. Brief Description of the Drawings

[0031] Figure 1 It is the first process schematic diagram of the numerical prediction method for the evolution of heavy metal pollution load in the river basin of the present invention; Figure 2 It is the second process schematic diagram of the numerical prediction method for the evolution of heavy metal pollution load in the river basin of the present invention; Figure 3 It is the schematic diagram of the change in heavy metal mass concentration in a certain river basin obtained by applying the present invention. Detailed Embodiments

[0032] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] On the contrary, the present invention covers any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present invention defined by the claims. Further, in order to enable the public to better understand the present invention, some specific details are described in detail in the following detailed description of the present invention. Those skilled in the art can fully understand the present invention without the description of these details.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention.

[0035] As Figure 1 shown, the first specific embodiment of the numerical prediction method for the evolution of heavy metal pollution load in the basin of the present invention: A numerical prediction method for the evolution of heavy metal pollution load in a basin, comprising the following: Collect heavy metal pollution data on land, water and air in the basin to be predicted through a pre-constructed heavy metal pollution collection model; Use a pre-constructed heavy metal parameter analysis model to process the heavy metal pollution data on land, water and air to obtain heavy metal transformation property parameters; Use a pre-constructed three-dimensional heavy metal evolution model. Based on the heavy metal transformation property parameters, simulate the processes of heavy metal leaching from soil due to rainfall, atmospheric heavy metal deposition, and changes in heavy metal load in water respectively to obtain multi-dimensional heavy metal evolution data, which is used to characterize the migration and change of heavy metals among land, water and air; Adopt a pre-constructed heavy metal coupling prediction model to perform coupling calculations on the multi-dimensional heavy metal evolution data, weather data, and hydrological calculation data, so as to calculate the evolution process of heavy metal pollution among land, water and air and obtain heavy metal pollution prediction values.

[0036] The second specific embodiment of the numerical prediction method for the evolution of heavy metal pollution load in the basin of the present invention: A numerical prediction method for the evolution of heavy metal pollution load in a basin, comprising the following: Collect heavy metal pollution data on land, water and air in the basin to be predicted through a pre-constructed heavy metal pollution collection model; Use a pre-constructed heavy metal parameter analysis model to process the heavy metal pollution data on land, water and air to obtain heavy metal transformation property parameters; Use a pre-constructed three-dimensional heavy metal evolution model. Based on the heavy metal transformation property parameters, simulate the processes of heavy metal leaching from soil due to rainfall, atmospheric heavy metal deposition, the process of biological deduction and reduction of heavy metals, and changes in heavy metal load in water respectively to obtain multi-dimensional heavy metal evolution data, which is used to characterize the migration and change of heavy metals among land, water, air and organisms; Using a pre - constructed heavy metal coupling prediction model, coupling and calculating multi - dimensional evolution data of heavy metals with weather data and hydrological calculation data to obtain the amount of heavy metals leached from the soil due to rainfall, the heavy metal load values deposited from the atmosphere to the soil and water bodies, and the deducted reduction amounts of heavy metals in the soil and heavy metal deposition by organisms. Then, combined with the emissions from heavy metal pollution point sources, calculate the heavy metal pollution prediction value to comprehensively calculate the evolution process of heavy metal pollution among land, water, air and organisms.

[0037] The present invention fully considers the exchange characteristics of heavy metal pollution at the interfaces of land, water, air and organisms. Based on weather changes and hydrological calculations, it accurately simulates the evolution process of heavy metal pollution among land, water, air and organisms, so as to numerically simulate the spatio - temporal distribution of heavy metal pollution load in the basin comprehensively. Therefore, it can more comprehensively track and predict the development trend of heavy metal pollution load in the basin.

[0038] The third specific embodiment of the numerical prediction method for the evolution of heavy metal pollution load in the basin of the present invention: A numerical prediction method for the evolution of heavy metal pollution load in a basin, comprising the following steps: Step 1, collect heavy metal pollution data of land, water and air in the basin to be predicted through a pre - constructed heavy metal pollution collection model; Step 2, use a pre - constructed heavy metal parameter analysis model to process the heavy metal pollution data of land, water and air to obtain heavy metal transformation property parameters; Step 3, use a pre - constructed three - dimensional heavy metal evolution model to simulate the transformation process of heavy metal pollution among land, water, air and organisms based on the heavy metal transformation property parameters to obtain multi - dimensional heavy metal evolution data; Step 4, adopt a pre - constructed heavy metal coupling prediction model to couple and calculate the multi - dimensional heavy metal evolution data with weather data and hydrological calculation data to obtain the migration data of heavy metals among land, water, air and organisms, so as to simulate the overall evolution process of heavy metal pollution and obtain the heavy metal pollution prediction value.

[0039] As Figure 2 shown, the fourth specific embodiment of the numerical prediction method for the evolution of heavy metal pollution load in the basin of the present invention: A numerical prediction method for the evolution of heavy metal pollution load in a basin, comprising the following steps: S1: Based on the digital elevation data of the basin to be predicted, discretize the basin space into several sub - basins, extract the water system, and construct a hydrological model.

[0040] S2: Incorporate the land use type, soil type, soil properties, and vegetation type of the basin into the hydrological model, and spatially discretize the above sub-basins again to obtain a hydrological calculation model. Then, use the hydrological calculation model to deduce the evolution of the point-source heavy metal pollution load in the basin.

[0041] S3: Use the heavy metal pollution collection model to collect the point-source emission data of heavy metal pollution in the rivers of the basin, as well as the heavy metal pollution content data in the air and soil.

[0042] S4: Through the heavy metal parameter analysis model, process the point-source emission data of heavy metal pollution to obtain the heavy metal transformation property parameters and the migration parameters of heavy metals among water, land, air, and organisms. Then, establish a three-dimensional heavy metal evolution model for simulating the migration and transformation process of non-point-source heavy metal pollution among the aqueous phase, suspended phase, and sediment phase. Process the heavy metal pollution content data in the air and soil to obtain the migration parameters of heavy metals among water, land, air, and organisms for calculating the migration process of heavy metals among water, land, air, and organisms.

[0043] S5: Considering the input of weather data, through the heavy metal coupling prediction model, couple the evolution of the point-source heavy metal pollution load and the heavy metal pollution load among water, land, air, and organisms to complete the numerical prediction of the heavy metal pollution load evolution in the basin.

[0044] In step S1 of this embodiment, based on the digital elevation data of the basin to be predicted, the basin space is discretized into several sub-basins, and the water system is extracted. The method for constructing the hydrological model is as follows: Using the basin terrain elevation in the digital elevation data (DEM), set a basin area threshold, which can take values from 0.1 to 100 square kilometers, to determine the sub-basin range. At the same time, define the positions with a slope greater than 10% in the digital elevation data as the sub-basin boundaries, and distinguish the river range to determine the water system. Then, select the basin outlet to divide the entire basin into several sub-basins that conform to the basin's geographical characteristics and natural runoff characteristics, denoted as such as n sub-basins, thus forming a hydrological model. The hydrological model is used for subsequent hydrological numerical calculations and can simulate the runoff in the basin surface, rivers, and soil.

[0045] In step S2 of this embodiment, incorporate the land use type, soil type, soil properties, and vegetation type of the basin into the hydrological model, and spatially discretize the above sub-basins again to obtain a hydrological calculation model, which is used as the carrier for calculating the water balance and material transport. It includes the following steps: S21: Collect the land use classification data in the basin to be predicted, and distinguish the land use types of cultivated land, forest land, pasture, industrial land, residential land, water area, pesticide and fertilizer usage information, and other land in the basin.

[0046] S22: Obtain the distribution of soil types and the physicochemical properties of the soil in the basin. The properties of different soils mainly include the structure of the soil layer, the available effective moisture in the soil layer, the saturated hydraulic conductivity, the wet density of the soil, the soil erosion force factor, the types and contents of heavy metals in the soil.

[0047] S23: Obtain the types and distributions of vegetation in the basin, and distinguish different plant communities covering the surface, such as forests, grasslands, shrubs, deserts, meadows, swamps, etc.

[0048] S24: According to the above land use classification, soil properties and vegetation type distributions, subdivide the sub-basins divided in S1, that is, for the sub-basins (1 ≤ ≤ n, where n is the total number of sub-basins), overlay the land use type distribution and soil type distribution contained within them to construct a hydrological calculation unit, and ensure that each hydrological calculation unit has a single land use type and soil type , that is . Finally, discretize the entire basin into a hydrological calculation model in space, establish a hydrological variable matrix on each unit, store the hydrological calculation variables, and use them to support the water volume between the hydrological calculation unit and the river, and between the hydrological calculation units. The hydrological variable matrix of each hydrological calculation unit at time is expressed as follows:

[0049] where is the soil water content; is the rainfall; is the surface runoff; is the evaporation; is the infiltration; is the baseflow.

[0050] S25: For each section of the river defined in S1, construct a river calculation unit, and set a river runoff variable matrix for the river calculation unit to store the river evolution calculation variables for river evolution calculation and heavy metal load transfer calculation. The river runoff variable matrix of each river calculation unit at time is expressed as follows:

[0051] where is the river runoff; is the river water volume; is the heavy metal mass concentration.

[0052] In this embodiment S3, using the heavy metal pollution collection model, the point source emission data of heavy metal pollution in the rivers of the basin and the heavy metal pollution content data in the air and soil are collected. The specific steps are as follows: S31: Using the heavy metal pollution collection model, collect the point source emission data of heavy metal pollution in the rivers of the basin, construct a point source emission database, and consider the heavy metal load input of this part of the point sources in subsequent numerical calculations. The point source emission database is constructed based on the daily load constant method, and the data includes the point source location, daily runoff, daily sediment load, and daily heavy metal load.

[0053] S32: Using the heavy metal pollution collection model, collect the heavy metal pollution content data in the air and soil of the basin, construct an air-land pollution database, and consider the heavy metal load input of this part of the area in subsequent numerical calculations. The air-land pollution database is constructed based on the monthly average load constant method, and the data includes the pollution area range, monthly average soil heavy metal load, and monthly average atmospheric heavy metal load.

[0054] In this embodiment S4, through the heavy metal parameter analysis model, the point source emission data of heavy metal pollution is processed to obtain the heavy metal transformation property parameters, and a three-dimensional heavy metal evolution model is established to simulate the migration and transformation process of non-point source heavy metal pollution between the aqueous phase, suspended phase, and sediment phase; the heavy metal pollution content data in the air and soil is processed to obtain the migration parameters of heavy metals between water, land, air, and organisms, which are used to calculate the migration process of heavy metals between water, land, air, and organisms. The specific steps are as follows: S41: Collect the heavy metal transformation property parameters obtained through experiments or investigations, which include the longitudinal diffusion coefficient , the measured adsorption coefficient , the sediment-water distribution coefficient , the desorption coefficient , the distribution coefficient of heavy metals between suspended matter and water body , the comprehensive sedimentation velocity , the comprehensive constant affecting sedimentation , the resuspension coefficient .

[0055] The longitudinal diffusion coefficient reflects the migration and diffusion of substances in the river and can be calculated using the empirical formula Fischer. The specific calculation formula is as follows:

[0056] In the formula, is the average water depth of the river, is the average width of the river, is the average flow velocity of the river, is the acceleration due to gravity, is the hydraulic gradient, which generally can take values from 1 to .

[0057] The distribution coefficient of heavy metals between suspended solids and water body is the ratio of the concentration of heavy metals in suspended state to the concentration of dissolved heavy metals at equilibrium, and its expression is as follows:

[0058] where, is the heavy metal content in particles, is the heavy metal content in the liquid phase. This coefficient is obtained by sampling and measuring the heavy metal content in water samples and soil samples, and generally the value range can be between 10 3 and 10 6 .

[0059] The distribution coefficient of sediment and water is the ratio of the concentration of heavy metals in sediment state to the concentration of dissolved heavy metals under the three-phase equilibrium state, and its expression is as follows:

[0060] where, is the heavy metal content in sediment, is the heavy metal content in the liquid phase. This coefficient is obtained by sampling and measuring the heavy metal content in sediment samples and soil samples, and generally the value range can be between 10 3 and 10 6 .

[0061] The influence comprehensive coefficient, resuspension coefficient and desorption coefficient, etc. can be determined by the inverse verification method, and generally the value range can be between and .

[0062] Considering that after heavy metal pollutants are discharged into the water body, they will undergo adsorption and desorption with suspended sediment particles in the water body. A part of the heavy metals will be adsorbed on the surface of suspended sediment particles and move with the suspended sediment, and will undergo convective diffusion migration with the heavy metals in the water body. At the same time, considering that another part of the heavy metals is caused by the sedimentation of suspended sediment and the resuspension of bed sediment, the heavy metal migration and transformation occur. Based on the heavy metal transformation property parameters and the convective diffusion characteristics, a heavy metal three-dimensional evolution model is established to characterize the mass concentration of dissolved and suspended heavy metals, and its calculation formula is as follows:

[0063]

[0064] where, is the source term of dissolved and suspended heavy metals, which can be regarded as the exchange rate of heavy metal antimony between sediment and water body per unit water depth, is the mass concentration of heavy metals; is the time step; is the longitudinal component of the water body section velocity; is the cross-section average velocity; is the longitudinal position component; is the mass concentration of dissolved heavy metals; is the mass concentration of suspended heavy metals; is the water depth.

[0065] S42: Set the initial heavy metal concentration at the initial time of the basin and the heavy metal concentration boundary condition at the basin model boundary, that is, the time series of heavy metal concentrations, and then discretize the above equation using the implicit difference method to obtain an implicit difference equation system, and its expression is as follows:

[0066]

[0067]

[0068]

[0069] Among them, is the basin node at time of the heavy metal mass concentration, is the basin node at time of the heavy metal mass concentration, is the basin node at time of the heavy metal mass concentration, is the basin node at time of the heavy metal mass concentration, is the basin node at time of the heavy metal mass concentration, is the grid size, is the time step, is the time step, is the longitudinal position component.

[0070] Furthermore, according to the implicit difference equation system, deform the heavy metal three-dimensional evolution model to obtain a new calculation equation system, specifically as follows:

[0071]

[0072]

[0073]

[0074] Among them, is the undetermined coefficient.

[0075] Write the system of equations in the form of a tridiagonal matrix and solve it using the chasing method to obtain the heavy metal mass concentration at each node at each moment. The specific expressions are as follows:

[0076]

[0077]

[0078]

[0079] Among them, is the undetermined coefficient, is the heavy metal mass concentration of the watershed node 0 at the moment ...

[0080] S43: Through soil sampling and experiments, based on the types of heavy metals, soil types, soil heavy metal contents, and the use of pesticides and fertilizers, process the heavy metal leaching data in the soil. For the leaching amounts of heavy metals in the soil under different rainwater pH values and rainfall durations, fit them using the heavy metal rainfall leaching law prediction equation to obtain the equation parameters for predicting the heavy metal rainfall leaching law in the soil, and obtain the heavy metal rainfall leaching law in the soil.

[0081] The heavy metal rainfall leaching equation can be fitted using forms such as the first-order kinetic equation, double-constant rate equation, parabolic equation, and modified kinetic equation Elovich.

[0082] The form of the first-order kinetic equation is as follows:

[0083] The form of the double-constant rate equation is as follows:

[0084] The form of the parabolic equation is as follows:

[0085] The form of the modified kinetic equation Elovich is as follows:

[0086] Among them, is the heavy metal leaching amount, is the equivalent rainfall duration, is a fitting constant, usually ranging from -100 to 100.

[0087] For the selected form of the prediction equation for the leaching law of heavy metals in rainfall, given a set of rainfall durations and corresponding soil heavy metal leaching amounts at different rainwater pH values, through equation fitting analysis, a set of equation parameters at different rainwater pH values is obtained , which is subsequently used to predict the soil heavy metal leaching amount under given rainfall pH and duration conditions.

[0088] S44: Through sampling experiments or investigations on the atmospheric environment, soil, and water bodies, based on the types and contents of heavy metals, soil types, and dry-wet conditions, calculate the atmospheric deposition flux of heavy metals, and its expression is as follows:

[0089]

[0090] Among them, is the wet deposition flux, is the dry deposition flux, is the heavy metal content of wet deposition, is the heavy metal content of dry deposition, is the wet deposition rate, is the dry deposition rate, is the air pressure factor, is the wind speed factor. After obtaining the above data through experiments and investigations, under given rainfall conditions, combined with air pressure, average wind speed, and basin area, the deposition load value of heavy metals from the atmosphere to the soil and water bodies is obtained.

[0091] S45: Through experiments or investigations, based on the types and contents of heavy metals in the basin and the vegetation cover type, obtain the absorption ratio of soil heavy metals by organisms and the filtration reduction ratio of atmospheric heavy metal deposition by organisms, with values ranging from 0 to 1. In subsequent calculation processes, deductions are made from the soil heavy metal load and atmospheric heavy metal deposition load in the corresponding regions.

[0092] In this embodiment S5, considering the input of weather data, through the heavy metal coupling prediction model, the evolution of the point source heavy metal pollution load and the heavy metal pollution load of water, land, air, and organisms is coupled, and the specific steps for completing the numerical prediction of the evolution of the heavy metal pollution load in the basin are as follows: S51: Collect the meteorological data of meteorological stations in the basin, including the annual maximum wind speed, daily maximum rainfall, monthly rainfall, air pressure, and observed values of rainwater pH, and calculate the soil moisture and precipitation for hydrological simulation.

[0093] S52: Set the initial hydrological conditions and meteorological data conditions of the basin based on meteorological data, including soil moisture content, rainfall, runoff, evaporation, infiltration, and baseflow; then conduct hydrological simulations on the discrete hydrological calculation model of the basin, and calculate the changes in runoff volume on the surface, in rivers, in soil, and in groundwater of the basin based on the principle of water balance, and simultaneously calculate the water balance between hydrological calculation units. The hydrological runoff and concentration calculation can be performed using the SCS curve number method or the Green & Ampt infiltration method. The calculation equation for water balance is:

[0094] Wherein, is the soil moisture content at time is the initial soil moisture content; is the rainfall; is the surface runoff; is the evaporation; is the infiltration; is the baseflow.

[0095] Further calculate the flow velocity of the river channel through the Manning formula , and calculate the cross-sectional area of flow based on the runoff volume belonging to the river channel, and simultaneously calculate the water depth of the river channel. The corresponding calculation formulas are as follows:

[0096]

[0097]

[0098]

[0099]

[0100] Wherein, is the flow velocity of the river channel; is the cross-sectional hydraulic radius; is the river channel slope; is the roughness coefficient; is the cross-sectional area of flow; is the river water volume; is the river runoff, obtained by the inflow of surface runoff; is the calculation time step; is the reach length; is the bottom width of the river channel; is the side slope of the river channel; is the water depth.

[0101] S53: Based on the consideration of point-source heavy metal pollution load in S3 and the heavy metal load leached from soil by rainfall, the heavy metal load deposited from the atmosphere to soil and water bodies, and the deduction and reduction of heavy metals in soil and heavy metal deposition by organisms in S4, and by superimposing solutes, the mass concentrations of dissolved heavy metals are combined and the mass concentrations of suspended heavy metals source terms, so as to obtain the predicted value of heavy metal pollution, enabling the simultaneous consideration of point-source and non-point-source heavy metals and the mass concentrations of heavy metal pollution loads from land, air, and organisms during the calculation process. And the flow velocity and water depth of the river channel are obtained through the basin water volume calculation described in S52, and then the flow velocity and water depth are transmitted to the three-dimensional heavy metal evolution model to calculate the distribution migration and component transformation process of heavy metal pollution loads in the basin, and finally the heavy metal mass concentration at each moment of the river channel in the basin is obtained.

[0102] A specific embodiment of applying the present invention to predict the evolution of heavy metal cadmium pollution load in a certain basin: The method for applying the present invention to predict the evolution of heavy metal cadmium pollution load in a certain basin is as follows: S1: Based on the digital elevation data of a certain basin, the basin space is discretized into several sub-basins, the water system is extracted, and a hydrological model is constructed, which specifically includes the following contents: Using Geographic Information System (GIS) technology to analyze the basin terrain elevation in the digital elevation data (DEM), setting the basin area threshold to 90 ha according to the scope of the basin to be predicted, traversing the pixels of the DEM, and obtaining the location information of the positions with a slope greater than 10% in the DEM. Then, according to the location information, the sub-basin boundaries are distinguished, the rivers are defined, the water system is determined, and the entire basin is divided into sub-basins that conform to the basin geographical characteristics and natural runoff and confluence characteristics, specifically denoted as and other 9 sub-basins, each sub-basin has a river, and there are 9 rivers in the whole basin. The sub-basin division will be used for subsequent hydrological numerical calculations.

[0103] S2: Collect the land use type, soil type, soil properties, and vegetation type of the basin to discretize the above sub-basins again to obtain a hydrological calculation model, which serves as the carrier for calculating the water balance and material transport in the model. The specific steps are as follows: S21: By collecting remote sensing data, obtain the land use classification data in the basin to be predicted, and subdivide the basin to be predicted into 3 land use types: cultivated land, forest land, and industrial land.

[0104] S22: By collecting remote sensing data and searching the literature, obtain the distribution of 2 soil types in the basin and the physical and chemical properties of the soil, which are highly active leached soil and saturated vertisol respectively. The properties of different soils mainly include the structure of the soil layer, the available effective moisture in the soil layer, the saturated hydraulic conductivity, the wet density of the soil, the soil erosion factor, and the cadmium content in the soil.

[0105] S23: By collecting remote sensing data and searching literature, we can obtain the vegetation types and distribution in the basin and distinguish the three plant communities covering the surface: forest, grassland, and shrub.

[0106] S24: Based on the above land use classification, soil properties and vegetation types The sub-basins divided in S1 are further split into several hydrological calculation units, and each hydrological calculation unit has a single land use type and soil type. Finally, the entire basin is discretized into 49 hydrological calculation units in space, and a hydrological variable matrix is ​​established in each unit to store hydrological calculation variables, which are used to support the water volume between hydrological calculation units and rivers, and between hydrological calculation units.

[0107] Furthermore, the i-th hydrological calculation unit is Hydrological variable matrix at time The expression is as follows:

[0108] in, is the soil moisture content; is the rainfall; is the surface runoff; is the evaporation amount; is the infiltration volume; is the underground runoff.

[0109] S24: For each river section defined in S1, a river calculation unit is established, and a river runoff variable matrix is ​​set to store river evolution calculation variables, which are used for river evolution calculation and heavy metal load transmission calculation.

[0110] The jth (j=1,2,…,9) river calculation unit is The river runoff variable matrix at time The expression is as follows:

[0111] in, is the river runoff; is the amount of water in the river; is the mass concentration of heavy metal cadmium.

[0112] S3: Through the heavy metal pollution collection model, collect the point source emission data of heavy metal pollution in the river basin, and the heavy metal pollution content data in the air and soil. The specific steps are as follows: S31: Using the heavy metal pollution collection model, collect the point source emission data of heavy metal pollution in the rivers of the basin, construct a point source emission database, and consider the heavy metal load input of this part of the point source in subsequent numerical calculations. The point source emission database is constructed based on the daily load constant method, and the heavy metal point sources are located at the confluence points of the rivers and , record the time series of the daily runoff volume, the time series of the daily sediment load, and the time series of the daily heavy metal cadmium load corresponding to the source items, and then superimpose them as the heavy metal cadmium mass concentration source items into the three-dimensional heavy metal evolution model.

[0113] S32: Using the heavy metal pollution collection model, collect the data on the heavy metal pollution content in the air and soil of the basin, construct an air-land pollution database, and consider the heavy metal load input of this part of the area in subsequent numerical calculations. The air-land pollution database is constructed based on the monthly average load constant method, and the data includes the monthly average soil heavy metal load and the monthly average atmospheric heavy metal load in the sub-basin range.

[0114] S4: Using the heavy metal parameter analysis model, collect the transformation property parameters of heavy metal cadmium, and establish a three-dimensional heavy metal evolution model; process the data on the heavy metal pollution content in the air and soil to obtain the migration parameters of heavy metals among water, land, air and organisms, which are used to calculate the migration process of heavy metals among water, land, air and organisms. The specific steps are as follows: S41: Collect the heavy metal transformation property parameters through experiments or investigations, including calculating the longitudinal diffusion coefficient of heavy metals using the empirical formula Fischer , measuring the adsorption coefficient , the sediment-water distribution coefficient , the desorption coefficient , the distribution coefficient of heavy metals between suspended solids and water , the comprehensive sedimentation velocity , the comprehensive constant affecting sedimentation , the resuspension coefficient .

[0115] Based on the heavy metal transformation property parameters, establish a three-dimensional heavy metal evolution model, and its expression is as follows:

[0116]

[0117] Among them, is the heavy metal mass concentration; is the time; is the longitudinal component of the water body section velocity; is the cross-sectional average velocity; is the longitudinal position component; is the mass concentration of dissolved heavy metals; is the mass concentration of suspended antimony; is the water depth.

[0118] S42: Set the initial concentration of heavy metals in the basin to 0 at the initial time, set the heavy metal concentration at the boundary of the basin model to be constantly 0, discretize the above equation using the implicit difference method, and then use the chasing method for triangular matrices to solve it.

[0119] S43: Through soil sampling, experiments or literature research, for the leaching amount data of soil heavy metals under different rainwater pH values and multiple rainfall durations, use the modified Elovich form of the kinetic equation for fitting. The modified Elovich form of the kinetic equation is as follows:

[0120] where, is the leaching amount of heavy metal cadmium, is the equivalent rainfall duration, and are fitting constants.

[0121] For a rainwater pH value of 5, the and values are 45 and 6; for a rainwater pH value of 6, the and values are 38 and 5.4; for a rainwater pH value of 7, the and values are 35 and 5.1; for a rainwater pH value of 5, the and values are 31 and 5.0. Summarize the and values for different pH values, and use the exponential function form for fitting respectively to obtain the fitting functions of the and values with respect to the pH value. Their calculation formulas are as follows:

[0122]

[0123] where, 、 、 and are the fitting constants of the above parameters, and pH is the pH value of the rainwater.

[0124] Substitute the fitting functions regarding and into the solution equation of thus forming Calculation formulas for rainfall duration and rainwater acidity, and the leaching amount of heavy metal cadmium in soil is obtained based on rainfall and rainwater acidity in subsequent simulations.

[0125] S44: Through sampling experiments or investigations on the atmospheric environment, soil, and water bodies, calculate the atmospheric deposition flux of heavy metals based on the types and contents of heavy metals, soil types, and wet and dry conditions:

[0126]

[0127] Among them, is the wet deposition flux, is the dry deposition flux, is the heavy metal content of wet deposition, is the heavy metal content of dry deposition, is the wet deposition rate, is the dry deposition rate, is the air pressure factor, obtained by the ratio of the actual air pressure to the reference air pressure, is the wind speed factor, obtained by the ratio of the reference average wind speed to the actual average wind speed.

[0128] Furthermore, the wet deposition flux and dry deposition flux of heavy metal cadmium can be obtained as 0.9 and 0.7 , respectively. Under the given rainfall conditions, combined with the actual air pressure, actual average wind speed, and watershed area, the deposition load value of heavy metals from atmospheric deposition to soil and water bodies can be obtained.

[0129] S45: Through experiments or investigations, obtain the absorption ratio of soil heavy metals by organisms and the filtration reduction ratio of atmospheric heavy metal deposition by organisms based on the types and contents of heavy metals in the watershed and the vegetation cover type, with values ranging from 0 to 1. In the subsequent calculation process, deductions are made from the soil heavy metal load and atmospheric heavy metal deposition load in the corresponding areas.

[0130] S5: Adopt a heavy metal coupling prediction model, collect weather data for the past 10 years, and couple the evolution of point source and land-air biogenic heavy metal pollution loads. The specific steps are as follows: S51: Collect meteorological data from meteorological stations in the watershed. There is 1 meteorological station in the watershed, and the data includes the annual maximum wind speed, daily maximum rainfall, monthly rainfall, and rainwater acidity observation values within the past 10 years; furthermore, based on the meteorological data, calculate soil humidity and precipitation, and statistically form the meteorological change law of the watershed and apply it to hydrological simulations.

[0131] S52: Set the initial hydrological conditions of the basin at the initial time. Based on the above meteorological data conditions, calculate the soil moisture and precipitation, conduct hydrological simulations on the discrete hydrological calculation model of the basin, and calculate the changes in runoff volume on the surface, in rivers, in the soil, and in groundwater of the basin based on the principle of water balance. At the same time, calculate the water transfer and sediment erosion between hydrological calculation units. The calculation formulas for hydrological runoff and concentration are as follows:

[0132]

[0133] Among them, is the surface runoff; is the rainfall; is the previous loss; S is the infiltration; the CN value is a constant, which is related to the previous soil moisture, soil type, vegetation cover type, hydrological conditions, and slope.

[0134] Use the calculation equation of water balance to calculate the water transfer of hydrological calculation units. The calculation formula is as follows:

[0135] Among them, is the soil water content at time is the initial soil water content; is the rainfall; is the surface runoff; is the evaporation; is the infiltration; is the baseflow.

[0136] Calculate the flow velocity of the river channel through the Manning formula , and calculate the cross-sectional area of flow and the water depth of the river channel based on the runoff volume. The corresponding calculation formulas are as follows:

[0137]

[0138]

[0139]

[0140]

[0141] Among them, is the flow velocity of the river channel; is the cross-sectional hydraulic radius; is the river channel slope, with a value of 0.001; is the roughness coefficient, with a value of 0.03; is the cross-sectional area of flow; is the river water volume; is the river runoff, obtained by the inflow of surface runoff; is the calculation time step, selected as 1 day; is the length of the river reach; is the bottom width of the river; is the side slope of the river channel; is the water depth.

[0142] S53: Consider the pollution load of heavy metal cadmium from point sources, and superimpose the amount of heavy metal cadmium leached from the soil due to rainfall, the heavy metal cadmium load deposited from the atmosphere to the soil and water bodies, the deduction and reduction amount of heavy metal cadmium in the soil and heavy metal cadmium deposition by organisms, the mass concentration of dissolved heavy metal cadmium, and the mass concentration of suspended heavy metal cadmium; then obtain the flow velocity and water depth of the river channel through the calculation of the basin water volume; furthermore, according to the flow velocity and water depth, solve the three-dimensional evolution model of heavy metals to simulate the distribution migration and component transformation process of heavy metal cadmium pollution load in the basin, and finally obtain the mass concentration of heavy metal cadmium at each moment in the river channel within the basin, which can be seen in Figure 3 . Figure 3 shows the predicted concentration values of heavy metal concentrations at key cross-sections downstream with the change of the calculation period after the upstream discharges heavy metal pollutants, as shown by the solid black dots in the figure, and the unit of the predicted concentration value is micrograms per liter , and the unit of the time calculation period is hours , it can be found that applying the present invention can accurately simulate the change trend of heavy metal pollution load in the basin, which is beneficial to the prevention and management of heavy metal pollution in the basin water body. Therefore, the present invention comprehensively considers the heavy metal pollution loads from point sources and non-point sources as well as those from land, air and organisms, can numerically simulate the spatio-temporal distribution of heavy metal pollution load in the basin more comprehensively, and can track and predict the change of heavy metal pollution load in the basin more comprehensively.

[0143] An equipment embodiment applying the method of the present invention: An electronic device, which includes: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the above-mentioned numerical prediction method for the evolution of heavy metal pollution load in a basin.

[0144] A computer medium embodiment applying the method of the present invention: A computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the above-mentioned numerical prediction method for the evolution of heavy metal pollution load in a basin.

[0145] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. 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, optical storage, etc.) containing computer-usable program code.

[0146] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (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 processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0147] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0148] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0149] The model in the present application is an object that constitutes an objective description of the morphological structure by means of physical or virtual representations. The object is not equal to an object and is not limited to physical and virtual. It can be a data processing function, a software program, a processing mode, a usage method, an operation mode, a workflow, an application process, electronic hardware, a circuit module, a processing system, a system imitation, or a simulation object.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify or equivalently replace the specific implementation manners of the present invention. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A numerical prediction method for the evolution of heavy metal pollution load in a basin, characterized by: including the following: Collecting heavy metal pollution data on land, water and air in the basin to be predicted through a pre-constructed heavy metal pollution collection model; Using a pre-constructed heavy metal parameter analysis model to process the heavy metal pollution data on land, water and air to obtain heavy metal transformation property parameters; Using a pre-constructed three-dimensional heavy metal evolution model, based on the heavy metal transformation property parameters, simulating the processes of heavy metal leaching from soil due to rainfall, atmospheric heavy metal deposition, and changes in water body heavy metal load respectively, to obtain multi-dimensional heavy metal evolution data for characterizing the migration and change of heavy metals among land, water and air; Adopting a pre-constructed heavy metal coupling prediction model to perform coupling calculation on the multi-dimensional heavy metal evolution data, weather data and hydrological calculation data to calculate the evolution process of heavy metal pollution among land, water and air and obtain heavy metal pollution prediction values.

2. A numerical prediction method for the evolution of heavy metal pollution load in a basin according to claim 1, characterized by: The method of collecting heavy metal pollution data on land, water and air in the basin to be predicted through a pre-constructed heavy metal pollution collection model is as follows: Obtaining the location information of the basin to be predicted; Based on the location information of the basin to be predicted, collecting point source emission data of heavy metal pollution in the basin to be predicted; The point source emission data includes at least point source location, basin runoff, basin sediment load and heavy metal load; Based on the point source emission data, constructing a point source emission database based on the daily load constant method; Based on the location information of the basin to be predicted, collecting heavy metal pollution content data in the air and soil of the basin; The heavy metal pollution content data includes the monthly average soil heavy metal load and the monthly average atmospheric heavy metal load in the basin range; Based on the heavy metal pollution content data, constructing an air-land pollution database based on the monthly average load constant method; Summarizing the point source emission database and the air-land pollution database to form heavy metal pollution data on land, water and air as the heavy metal load input for numerical calculation.

3. A numerical prediction method for the evolution of heavy metal pollution load in a basin according to claim 1, characterized by: The method of using a pre-constructed heavy metal parameter analysis model to process the heavy metal pollution data on land, water and air to obtain heavy metal transformation property parameters is as follows: According to the heavy metal pollution data on land, water and air, obtaining the types of heavy metals, soil types, longitudinal diffusion coefficients of heavy metals, measured adsorption coefficients, distribution coefficients between sediment and water, and dry and wet conditions; Based on the types of heavy metals, longitudinal diffusion coefficients of heavy metals, measured adsorption coefficients and distribution coefficients between sediment and water, determining the desorption coefficients of heavy metals and the distribution coefficients of heavy metals between suspended solids and water bodies; Using the desorption coefficients of heavy metals and the distribution coefficients of heavy metals between suspended solids and water bodies to calculate the comprehensive sedimentation velocity, comprehensive sedimentation influence constant and resuspension coefficient of heavy metals; Based on the types of heavy metals, soil types and usage rules of pesticides and fertilizers, determining the soil heavy metal content and the usage information of pesticides and fertilizers; Summarize the types of heavy metals, soil types, longitudinal diffusion coefficients of heavy metals, measured adsorption coefficients, distribution coefficients between sediment and water, dry and wet conditions, desorption coefficients of heavy metals, distribution coefficients of heavy metals between suspended solids and water bodies, comprehensive sedimentation rates of heavy metals, comprehensive sedimentation influence constants, resuspension coefficients, equation parameters, soil heavy metal contents, and the usage information of pesticides and fertilizers to obtain heavy metal transformation property parameters.

4. A numerical prediction method for the evolution of heavy metal pollution load in a basin as described in claim 1, characterized in that: The method for simulating the leaching process of heavy metals from soil due to rainfall using a pre-constructed three-dimensional heavy metal evolution model based on heavy metal transformation property parameters is as follows: Based on heavy metal transformation property parameters, obtain the soil heavy metal content and the usage information of pesticides and fertilizers. According to the soil heavy metal content, the usage information of pesticides and fertilizers, the equivalent rainfall duration, and multiple unknown variable parameters, construct a heavy metal rainfall leaching equation. Use the heavy metal rainfall leaching equation to fit the leaching amount data of soil heavy metals under different rainwater pH values and multiple groups of rainfall durations to obtain a fitting result. According to the fitting result, determine the values of variable parameters under different rainwater pH values. Summarize the values of variable parameters for different rainwater pH values, and then use an exponential function for fitting to obtain a fitting function of the variable with respect to the pH value. Substitute the fitting function of the variable with respect to the pH value into the heavy metal rainfall leaching equation to form a calculation formula for the leaching amount of heavy metals with respect to the rainfall duration and rainwater pH value, thereby realizing the simulation of the leaching process of heavy metals from soil due to rainfall.

5. A numerical prediction method for the evolution of heavy metal pollution load in a basin as described in claim 1, characterized in that: The method for simulating the atmospheric heavy metal sedimentation process is as follows: Based on heavy metal transformation property parameters, determine the types of heavy metals, soil types, and dry and wet conditions. According to the types of heavy metals, soil types, and dry and wet conditions, determine the heavy metal sedimentation information. The heavy metal sedimentation information includes the heavy metal content of wet deposition, the heavy metal content of dry deposition, the wet deposition rate, and the dry deposition rate. Based on rainfall conditions and air pressure information, obtain the actual air pressure and the reference air pressure. Take the ratio of the actual air pressure to the reference air pressure as the air pressure factor. Based on rainfall conditions and average wind speed information, obtain the reference average wind speed and the actual average wind speed. Take the ratio of the reference average wind speed to the actual average wind speed as the wind speed factor. According to the heavy metal sedimentation information, the air pressure factor, and the wind speed factor, construct a calculation formula for the wet deposition flux and a calculation formula for the dry deposition flux of heavy metals. Jointly solve the calculation formula for the wet deposition flux and the calculation formula for the dry deposition flux of heavy metals to obtain the load of heavy metals sedimenting from the atmosphere to the soil and water bodies, thereby realizing the simulation of the atmospheric heavy metal sedimentation process.

6. A numerical prediction method for the evolution of heavy metal pollution load in a basin as described in claim 1, characterized in that: It also includes using a pre-constructed three-dimensional heavy metal evolution model to simulate the process of biological deduction and reduction of heavy metals based on heavy metal transformation property parameters, and the method is as follows: Determine the vegetation cover type according to the soil type and the geographical location of the basin to be predicted; Obtain the absorption ratio of heavy metals in soil by organisms and the filtration reduction ratio of atmospheric heavy metal deposition by organisms according to the vegetation cover type and the heavy metal transformation property parameters; Determine the deduction reduction amount of heavy metals by organisms according to the absorption ratio and the filtration reduction ratio, and realize the simulation of the heavy metal deduction reduction process.

7. A numerical prediction method for the evolution of heavy metal pollution load in a basin as described in claim 1, characterized in that: The method for obtaining the heavy metal pollution prediction value is as follows: Substitute the rainfall data of the basin to be predicted into the calculation formula of heavy metal leaching amount with respect to rainfall duration and rainwater pH value to obtain the heavy metal leaching amount of the basin to be predicted; Determine the calculation formulas for wet deposition flux and dry deposition flux of heavy metals according to the atmospheric heavy metal deposition process; Based on the meteorological information and the area of the basin to be predicted, and in combination with the calculation formulas for wet deposition flux and dry deposition flux of heavy metals, calculate the deposition load value of heavy metals from the atmosphere to the soil and water bodies; Use the point source emission data of heavy metals as the new heavy metal pollution data for land, water and air; Substitute the new heavy metal pollution data for land, water and air and the hydrological calculation data into the change process of water body heavy metal load, and by superimposing solutes, combine the mass concentration source terms of dissolved heavy metals and suspended heavy metals into the transformation prediction calculation equation set to construct the overall prediction calculation equation set; Solve the overall prediction calculation equation set to obtain the heavy metal mass concentration at each moment in the basin, that is, the heavy metal pollution prediction value.

8. A numerical prediction method for the evolution of heavy metal pollution load in a basin as described in claim 7, characterized in that: The method for constructing a hydrological calculation model is as follows: Collect the land use classification data of the basin to be predicted; Obtain the soil type distribution information and soil property data according to the land use classification data; Obtain several sub-basins of the basin to be predicted, and according to the soil type distribution information and soil property data, subdivide the sub-basins, and superimpose the soil type distribution information and soil property data to obtain several hydrological calculation units; Each hydrological calculation unit has a single land use type and soil type, and a hydrological variable matrix is established on each hydrological calculation unit; According to the water area information, construct several river calculation units, and set a river runoff variable matrix on each river calculation unit for river evolution calculation and heavy metal load transmission calculation; Couple several hydrological calculation units and river calculation units to obtain a hydrological calculation model as the carrier for calculating water balance and material transport.

9. A numerical prediction method for the evolution of heavy metal pollution load in a basin as described in claim 8, characterized in that: The method for obtaining several sub-basins of the basin to be predicted is as follows: Obtain the location information of the basin to be predicted; Based on the location information of the basin to be predicted, obtain the digital elevation data of the basin to be predicted; According to the digital elevation data of the basin to be predicted, obtain the boundary location information with a slope greater than 10%; Determine the boundaries of several sub-basins through the boundary location information; Determine the sub - basin scope based on the boundaries of sub - basins and the basin area threshold; According to the scope of each sub - basin, determine the outlet of each sub - basin, thereby dividing the entire basin into several sub - basins that conform to the basin's geographical characteristics and natural runoff and confluence characteristics.

10. A numerical prediction system for the evolution of heavy metal pollution load in a basin, characterized in that: It includes: One or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors are caused to implement a numerical prediction method for the evolution of heavy metal pollution load in a basin as described in any one of claims 1 - 9.

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