A Generalized Simulation Method and System for Non-Point Source Nitrogen Pollution in River Basins

Abstract

The present invention discloses a general method and system for simulating non-point source nitrogen pollution in a river basin. The method includes: obtaining, through a general interface provided by the system, the type and model structure of a coupled hydrological model configured by a user, and obtaining the basic information of the river basin configured according to corresponding format requirements; obtaining, through the general interface, the agricultural nitrogen input of the river basin configured by the user, and extracting the spatio-temporal characteristics of its environmental surplus based on the agricultural nitrogen input of the river basin; reading the hydrological process simulation information obtained by calculating through the hydrological model; under the drive of the hydrological process, simulating the spatio-temporal dynamic changes of nitrogen in the river basin based on the nitrogen transport and transformation process description method and parameterization scheme; analyzing the simulation results to identify the high-risk periods and high-risk areas of non-point source nitrogen pollution. The present invention has good compatibility with different types of conceptual hydrological models of river basins, and can conveniently achieve accurate simulation of the spatio-temporal dynamic balance of nitrogen in the river basin and the nitrate nitrogen concentration at the river control section.

Description

Technical Field

[0001] The present invention belongs to the technical field of prevention, control and management of water environmental pollution in river basins, and particularly relates to a general simulation method and system for non-point source nitrogen pollution in river basins. Background Technique

[0002] The nitrogen cycle is an important material guarantee for the healthy operation of the ecosystem and the realization of ecological service functions. The development of industrialization has greatly exceeded the "safe operating range" of the Earth system in the cycle of nutrients such as nitrogen, resulting in a series of problems such as surface and groundwater pollution and the outbreak of cyanobacteria blooms in lakes and reservoirs. At present, globally, non-point source emissions in river basins have become the main source of pollution of nutrients such as nitrates in surface water bodies. However, the non-point source material cycle in river basins is affected by many factors such as the geographical characteristics of the river basin, hydro-meteorological conditions, and human activities, showing a high degree of mechanism complexity and spatio-temporal heterogeneity, making the prevention and control of non-point source pollution a bottleneck problem and a global challenge for further improving the water environment of river basins. The conceptual mechanism model of the river basin is a scientific summary and generalization of people's understanding of the laws of water-material cycles in river basins. Different types of river basin models have been successively proposed and continuously improved and expanded in terms of the spatio-temporal representativeness of river basin characteristics and the description of the water-energy-quality cycle mechanism in river basins, providing a powerful support tool for river basin water science research and water resources and water environment management.

[0003] The migration process of surface-source nitrogen and other pollutants at the watershed scale is mainly driven by the watershed hydrological process, and complex biogeochemical transformations occur simultaneously during the migration process. Therefore, the research and development of existing watershed hydrological and water quality coupling simulation models often rely on a specific hydrological simulation platform or hydrological model structure to expand the water quality simulation module. Although this technical route can fully utilize the technical advantages of a specific hydrological simulation platform, the implementation and application of water quality simulation are often restricted by this hydrological simulation platform (including its limitations in model generalization or data requirements), resulting in insufficient generality. On the one hand, this lack of generality leads to a relatively single variety of selectable water quality simulation models. For example, in the 257 watershed water quality simulation research cases counted by Wellen et al. (Wellen, et al., Evaluation of the Current State of Distributed Watershed Nutrient Water Quality Modeling, Environ. Sci. Technol., 2015, 49, 3278–3290), approximately 80% concentrated on using 5 models (namely the SWAT model, INCA model, AGNPS / AnnAGNPS model, HPSF model, and HBV-NP / HYPE model); on the other hand, the lack of generality of watershed water quality models prevents the full utilization of existing watershed hydrological simulation basic platforms, thus severely restricting the theoretical research and practical management of watershed non-point source pollution prevention and control.

[0004] To address the above problems, there is an urgent need to develop a general-purpose watershed water quality simulation method to be compatible with the model structures of different hydrological models and the generalized description methods of hydrological processes, so as to more conveniently achieve the accurate simulation of the migration and transformation of surface-source nitrogen and other pollutants in the watershed and guide the effective prevention and control of watershed non-point source pollution risks. Summary of the Invention

[0005] Object of the Invention: Aiming at the deficiencies of existing watershed water quality simulation technologies, the present invention proposes a general-purpose watershed non-point source nitrogen pollution simulation method, which has good compatibility with different types of watershed conceptual hydrological models and can conveniently achieve the accurate simulation of the temporal and spatial dynamic balance of nitrogen in the watershed and the nitrate nitrogen concentration at the river control section on the basis of existing hydrological simulations, thereby providing a scientific basis for watershed non-point source pollution prevention and control.

[0006] Another object of the present invention is to provide a general-purpose watershed surface-source nitrogen pollution simulation system, computer equipment, and computer storage medium.

[0007] Technical solution: To achieve the above-mentioned invention object, a general method for simulating non-point source nitrogen pollution in a watershed is proposed in the present invention, which is completed based on a general system for simulating non-point source nitrogen pollution in a watershed. The method includes the following steps:

[0008] Step 1: Through the general interface provided by the general system for simulating non-point source nitrogen pollution in a watershed, obtain the type and model structure of the coupled hydrological model configured by the user, and obtain the basic watershed information configured according to the corresponding format requirements, including: the designation for distributed or semi-distributed model types; the input data of the basic watershed information configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body configured based on the general water storage body storage-flux interaction structure.

[0009] Step 2: Through the general interface, obtain the input of watershed agricultural nitrogen sources configured by the user. Based on the spatial distribution map of crop rotation types in the watershed, determine the spatial distribution of crop types and rotation sequences, estimate the crop nitrogen uptake using the empirical growth curve method based on three parameters, and identify the environmental surplus and its spatio-temporal characteristics after nitrogen fertilizer is absorbed by crops.

[0010] Step 3: Read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological processes, and intermediate state variable information.

[0011] Step 4: Under the drive of the hydrological process, based on the nitrogen transport and transformation process description method and parameterization scheme, simulate the spatio-temporal dynamic changes of nitrogen in the watershed, including: matching the basic watershed information with the input characteristic information of agricultural nitrogen sources to determine the nitrogen model structure; based on the nitrogen model structure, the spatio-temporal characteristics of agricultural nitrogen input in the watershed, and the hydrological process simulation information, determine the biogeochemical transformation process between different nitrogen forms and its generalized description method, construct a hydrological and water quality coupling model, and conduct spatio-temporal dynamic simulation of nitrogen in the watershed.

[0012] Step 5: Analyze the simulation results and identify the high-risk periods and high-risk areas of non-point source nitrogen pollution, including: identifying the high-risk periods from the dynamic changes of nitrate ammonia concentration at key river cross-sections; identifying the high-risk areas from the spatial distribution of nitrogen balance in the watershed.

[0013] Furthermore, the types of hydrological models include fully distributed models and semi-distributed models. The general interface supports the configuration of the watershed discretization scheme. For fully distributed models, discretization is performed with regular grids as the basic calculation units, and for semi-distributed models, spatial discretization is carried out with sub-watersheds, and hydrological response units are defined within the sub-watersheds according to the geographical landscape types.

[0014] The general interface supports configuring the structures of different hydrological models and the corresponding variable names, and supports configuring all the conceptual water storage bodies included in different hydrological models and their input and output items;

[0015] The basic basin information includes one or more of elevation, flow direction, slope, land cover, and soil type.

[0016] Further, the method for estimating crop nitrogen uptake using the three-parameter empirical growth curve method includes:

[0017] Calculating the theoretical nitrogen uptake of crops using the three-parameter empirical growth curve:

[0018]

[0019] help=(up1-up2)·e -up3·(ΔDS)

[0020] In the formula, U P is the nitrogen uptake capacity of the crop since sowing, up1, up2, and up3 are the three empirical parameters of the growth curve respectively, and ΔDS is the number of days from the current calculation time to the sowing date;

[0021] Estimating the actual uptake of crops considering the limitations of soil moisture and nitrogen storage:

[0022] U A =min{U P ,f θ ·S N}

[0023]

[0024] In the formula, U A is the actual nitrogen uptake, f θ is the soil moisture limitation factor, which is related to the soil water content θ and the wilting coefficient θ w , and S N is the soil nitrogen storage.

[0025] Further, reading the hydrological process simulation information calculated by the hydrological model, including:

[0026] According to the consensus that the hydrological process simulation information is stored in the network common data format netCDF, reading the corresponding hydrological simulation information of the netCDF file through the specified variable names in the general interface file.

[0027] Furthermore, match the basic information of the basin with the characteristics of agricultural nitrogen source input to determine the nitrogen model structure; based on the nitrogen model structure, the spatio-temporal characteristics of agricultural nitrogen input in the basin, and the hydrological process simulation information, determine the biogeochemical transformation process between different nitrogen forms and its generalized description method, construct a coupled hydrological and water quality model, and conduct spatio-temporal dynamic simulation of basin nitrogen, including:

[0028] According to the basic information of the basin and the coupled hydrological model structure configured in Step 1, match the model structure for nitrogen simulation, including the landscape types and their area proportions within the basic calculation unit, and the soil stratification settings;

[0029] After determining the nitrogen model structure, according to the analysis results of agricultural nitrogen source input characteristics in Step 2, configure the agricultural nitrogen source input of each soil layer water body, and give the initial value of the dissolved nitrogen concentration of each water body;

[0030] According to the input-output items of each water body configured in Step 1, conduct the spatio-temporal dynamic simulation process of nitrogen. Among them, according to the mass balance principle, based on the hydrological process simulation information in Step 3, dissolved nitrogen undergoes storage-flux exchange in the vertical and horizontal directions with the water flow. The vertical direction refers to the hydraulic connection between different water bodies within the same basic calculation unit, and the horizontal direction refers to the hydraulic connection between the water bodies of different calculation units;

[0031] Considering that the main existing forms of soil nitrogen in each soil layer are dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), solid easily degradable organic nitrogen (SON) a and non-easily degradable organic nitrogen (SON) i There are four types in total. Establish the biogeochemical transformation process between them, including: the activation from non-easily degradable to easily degradable organic forms, the mineralization from organic to inorganic forms, the dissolution from easily degradable solid to dissolved state, and the denitrification of nitrate nitrogen under anaerobic conditions. Use the reaction kinetics method to quantitatively estimate the conversion amount;

[0032] Considering that the nitrogen forms in the river channel water body within each calculation reach are dissolved organic nitrogen (DON) w and dissolved inorganic nitrogen (DIN) w , at the same time, consider the photosynthetic assimilation absorption process and denitrification process in the river channel and conduct generalized calculations.

[0033] Furthermore, use the reaction kinetics method to quantitatively estimate the conversion amount, including:

[0034] Let R 活化 represent the activation from non-easily degradable to easily degradable organic forms, and R 矿化 represent the mineralization from organic to inorganic forms, and R 溶解 represent the dissolution from easily degradable solid to dissolved state, and R反硝化 Denotes the denitrification of nitrate nitrogen under anaerobic conditions, and the calculation method is as follows:

[0035] R 活化 = r degdt · f st · f sm · S SONi

[0036] R 矿化 = r minrl · f st · f sm ·(S DON + S SONa )

[0037] R 溶解 = r dissl · f st · f sm · S SONa

[0038] R 反硝化 = r denis · f st · f sm · f smc · S DIN

[0039] In the formula, r degdt , r minrl , r dissl , r denis represent the conversion rates of each process and are parameters introduced into the model; S SONi , S DON , S SONa , S DIN are the storage amounts of various soil nitrogen; f st , f sm , f smc are the soil temperature influence factor, soil moisture influence factor, and soil water-nitrogen concentration influence factor respectively;

[0040] Denote the photosynthetic assimilation absorption process by U gpp , and the river channel denitrification process by R 河道反硝化 . The generalized calculation method is as follows:

[0041] U gpp = U amax · f GR ·(1 - f LAI )

[0042] R 河道反硝化 = r deniw · f wt · f wnc

[0043] In the formula, U amax is the maximum photosynthetic absorption; f GR is the photosynthetic radiation factor; f LAI is the shielding factor of the river channel vegetation canopy, r deniw is the denitrification rate of the river channel, as a model parameter; f wt and f wnc are the influencing factors of river channel water temperature and river water nitrate nitrogen concentration respectively.

[0044] Furthermore, identify the high-risk periods from the dynamic changes of nitrate nitrogen concentration at the key cross-sections of the river; identify the high-risk areas from the spatial distribution of the nitrogen balance in the basin, including:

[0045] Based on the temporal and spatial dynamic simulation of basin nitrogen, perform continuous calculations on a daily scale, provide continuous simulation results of the discharge of land surface nitrogen in the basin to the receiving water body, and identify the high-risk periods of non-point source nitrogen pollution;

[0046] Based on the output function of the dynamic intermediate state of basin nitrogen, including one or more of crop nitrogen uptake, denitrification process uptake, soil nitrogen storage, and land surface output with runoff, simulate the spatial distribution and its dynamic changes of the nitrogen balance in the basin, and identify the high-risk sub-areas of non-point source nitrogen pollution.

[0047] The present invention also provides a generalized non-point source nitrogen pollution simulation system for a basin, including:

[0048] A hydrological model and a basin basic information configuration module, which are used to obtain the type and model structure of the coupled hydrological model configured by the user via a generalized interface, and obtain the basin basic information configured according to the corresponding format requirements, including: the designation for the distributed or semi-distributed model type; the input data of the basin basic information configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body configured based on the generalized water storage body storage-flux interaction structure;

[0049] A basin agricultural nitrogen characteristic extraction module, which is used to obtain the input of basin agricultural nitrogen sources configured by the user via a generalized interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the basin, estimate the crop nitrogen uptake using the empirical growth curve method based on three parameters, and identify the environmental surplus and its temporal and spatial characteristics after the nitrogen fertilizer is absorbed by the crops;

[0050] A hydrological simulation information reading module, which is used to read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological processes, and intermediate state variable information;

[0051] The basin nitrogen spatio-temporal simulation module is used to simulate the spatio-temporal dynamics of nitrogen in the basin under the drive of the hydrological process, based on the description method and parameterization scheme of the nitrogen transport and transformation process, including: matching the basic information of the basin with the input characteristics of agricultural nitrogen sources to determine the nitrogen model structure; based on the nitrogen model structure, the spatio-temporal characteristics of agricultural nitrogen input in the basin, and the hydrological process simulation information, determining the biogeochemical transformation process between different nitrogen forms and its generalized description method, constructing a coupled hydrological and water quality model, and conducting spatio-temporal dynamic simulation of basin nitrogen.

[0052] The risk identification module is used to analyze the simulation results and identify the high-risk periods and high-risk areas of non-point source nitrogen pollution, including: identifying the high-risk periods from the dynamic changes in the nitrate nitrogen concentration at key river cross-sections; identifying the high-risk areas from the spatial distribution of the nitrogen balance in the basin.

[0053] The present invention also provides a computer device, including: one or more processors; a memory; and one or more programs, where the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the generalized non-point source nitrogen pollution simulation method for basins described above are implemented.

[0054] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the generalized non-point source nitrogen pollution simulation method for basins described above are implemented.

[0055] Advantages: Compared with the prior art, the present invention has the following remarkable advantages:

[0056] (1) Utilize the generalized interface to configure the type and model structure of the coupled hydrological model, and configure the basic information such as basin hydrometeorology, geography, and human activities according to the corresponding format requirements, so as to be compatible with different types and different complexity levels of basin hydrological models, and can fully utilize the existing hydrological model platform to conveniently use its hydrological simulation information for spatio-temporal simulation of basin nitrogen dynamics, and support the detailed prevention and control of non-point source nitrogen pollution in the basin.

[0057] (2) Provide a description method and parameterization scheme for the nitrogen transport and transformation process, which can finely depict the spatio-temporal impact of agricultural activities on basin nitrogen pollution. In view of the difficulty in obtaining the spatial information of crop planting structures, it is proposed to use the spatial distribution of crop rotation types and the types of rotation crops of each type to fully characterize the spatial differences and inter-annual changes of crop planting structures.

[0058] (3) Provide a general water quality simulation environment, which can synchronously couple multiple hydrological models for cross-comparison to evaluate the impact of hydrological simulation on non-point source nitrogen pollution simulation in the basin. A flexible parameterization scheme is adopted to fully characterize the spatial heterogeneity of basin characteristics. Description of the Drawings

[0059] Figure 1 It is a schematic flow chart of a generalized simulation method for non-point source nitrogen pollution in a river basin;

[0060] Figure 2 It is the basic situation of the river basin applied in the embodiment;

[0061] Figure 3 It is the simulation result of coupling EcH2O-iso and mHM in the embodiment;

[0062] Figure 4 It is the simulation result of the nitrogen balance in the river basin simulated by coupling EcH2O-iso and mHM in the embodiment and its comparison. Detailed Implementation Modes

[0063] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0064] The present invention provides a generalized simulation method for non-point source nitrogen pollution in a river basin. This method is implemented based on a generalized simulation system for non-point source nitrogen pollution in a river basin. The generalized simulation system for non-point source nitrogen pollution in a river basin is a flexible and general simulation tool for non-point source nitrogen pollution in a river basin, which is also simply referred to as the system in the following text. It provides an interactive interface for hydrological models and data configuration, and provides a function for depicting and displaying the temporal and spatial dynamic changes of nitrogen in the river basin according to the input information. The method and system have good compatibility with different types of conceptual hydrological models in the river basin, and can conveniently realize the accurate simulation of the temporal and spatial dynamic balance of nitrogen in the river basin and the nitrate nitrogen concentration at the river control section on the basis of existing hydrological simulations, so as to provide a scientific basis for the prevention and control of non-point source pollution in the river basin.

[0065] Refer to Figure 1 , the method includes the following steps:

[0066] Step 1: Configure the structure of the coupled hydrological model and the basic information of the river basin in the corresponding format.

[0067] This method is applicable to coupling different types of hydrological models in the river basin, including fully distributed and semi-distributed models. And it can adapt to the differences in the requirements of different types of models for the river basin discretization scheme and the corresponding format of the basic information of the river basin. Use the generalized interface provided by the system to configure the river basin discretization scheme. The fully distributed model is discretized with regular grids as the basic calculation units, while the semi-distributed model is spatially discretized with sub-basins, and hydrological response units are defined according to the geographical landscape types within the sub-basins; at the same time, configure the input data of the basic information of the river basin according to the corresponding format requirements, including elevation, flow direction, slope, and land cover, soil type, etc.

[0068] This method is applicable to the different ways of generalizing the description of the watershed hydrological process by different models. This method takes into account the water storage bodies (i.e., conceptual water storage tanks) such as the vegetation canopy, the land surface, the soil (which can be divided into three layers), and the groundwater body within the basic calculation unit of the model, as well as the water flow exchange in the vertical direction between them; in the horizontal direction, it takes into account the water flow exchange between basic units through the land surface, subsurface flow, and groundwater. At the same time, it takes into account the overland runoff generation and concentration (three runoff components: surface runoff, subsurface flow, and groundwater runoff) and the river channel concentration process. In particular, for fully distributed simulations, this method can set up independent river channel concentration grids, so as to realize the river channel concentration calculation only between the grids containing real rivers. When coupling a specific hydrological model, configure the structure of the model and the corresponding variable names in the general interface.

[0069] This method proposes a general storage-flux interaction structure to adapt to the differences in the water flow exchange processes of different conceptual water storage bodies. This general structure can consider all hydrological flux input and output methods, including input from the upper tank, output to the upper tank, input from the lower tank, output to the lower tank, lateral input from the same-level tank of the upstream calculation unit, and lateral output to the same-level tank of the downstream unit; at the same time, this general structure can consider additional flux inputs (such as irrigation, inter-basin water transfer, etc.) and outputs (such as evapotranspiration, runoff generation, etc.). When coupling a specific hydrological model, specify all the conceptual water storage bodies included in the model in the general interface, and at the same time configure the input and output items of each water storage body (specify the variable names of each variable).

[0070] In the embodiments of the present invention, this method is used to couple two watershed hydrological models with very different characteristics. The two models are the EcH2O-iso model and the mHM model (the model structure comparison is shown in Table 1), and a watershed with an area of 99 km 2 is selected for case analysis. The terrain of the watershed is mainly forest and agricultural land. In this case, basic information such as the terrain, land use, and soil characteristics of the watershed is collected. At the same time, daily-scale meteorological data during the period from 2010 to 2018 is collected. Observation data of daily flow and nitrate nitrogen concentration are collected at the hydrological station at the outlet of the watershed during the period from 2010 to 2018.

[0071] Table 1 Structural comparison of watershed hydrological models EcH2O-iso and mHM

[0072]

[0073]

[0074] Both the EcH2O-iso and mHM models used in this case are grid-based distributed models, and the grid accuracy of land surface hydrological simulation is set to 1×1 km for both. The difference between them is that the former uses a confluence simulation grid that matches the actual river network, that is, the channel confluence and the process of nitrate nitrogen migration and transformation in the channel are only considered when there is a river; the latter uses a 2×2 km confluence spatial resolution to simulate the channel hydrological and water quality processes. Figure 2 This is the basic situation of the basin applied in the case study, where (a) is the digital elevation model - DEM (30-meter resolution), river network, and outlet hydrological station; (b) is the land cover type; (c) is the channel simulation grid of EcH2O-iso based on the actual river network location; (d) is the 2×2 km channel simulation grid of the entire basin of mHM.

[0075] According to the respective structures of the hydrological models, the basic situation of the basin topography and geography, etc., including spatial distribution information such as elevation (and slope and flow direction information generated therefrom), land use, and soil type, is configured in the general interface.

[0076] Step 2: Identify the temporal and spatial characteristics of agricultural nitrogen input and its environmental surplus in the basin.

[0077] The agricultural information that needs to be obtained by this method for the basin includes the types of crops in the basin and the sowing time, harvesting time, number of fertilizations, time of each fertilization, amount of each fertilization, etc. for each type of crop.

[0078] Aiming at the problem that it is difficult to obtain the spatial distribution of the crop planting structure in the basin and there are large inter-annual variations, based on the basin land use map, this method obtains the main crop types and rotation methods in different regions of the basin through means such as on-site investigations, and makes a "spatial distribution map of crop rotation types" and a "crop type lookup table" (defining the crop types and rotation order within each rotation type), so as to effectively consider the spatial differences and inter-annual variations of crop planting in the basin. Combining the above various crop fertilization management information, the temporal and spatial characteristics of agricultural nitrogen input in the basin can be obtained.

[0079] In this case, the crops planted in the agricultural land of the basin are winter wheat and rapeseed. Since the agricultural management methods in the basin are similar and the agricultural land is relatively small, all agricultural land is classified into the same rotation type, that is, two crops, winter wheat and winter rapeseed. In this case, the fertilization amounts (158 and 182 kg Nha -1 yr -1 )), fertilization dates, farming management information such as sowing and harvesting, etc. (see Table 2) are obtained. At the same time, this method uses a three-parameter empirical growth function to describe the nitrogen absorption capacity of crops, and the calculation method is as follows:

[0080]

[0081] help = (up1 - up2)·e -up3·(ΔDS)

[0082] In the formula, U P is the nitrogen absorption capacity (g N m -2 d -1 ), up1, up2, and up3 are the three empirical parameters of the growth curve, and ΔDS is the number of days from the current calculation time to the sowing date. The values of up1, up2, and up3 of this growth function for winter wheat and winter rape in the basin of this case are shown in Table 2.

[0083] Table 2 Parameters of crop fertilization, field management, and nitrogen absorption capacity in the case basin

[0084]

[0085] The actual crop absorption is further considered under the limitation of soil moisture and nitrogen storage:

[0086] U A = min{U P , f θ ·S N}

[0087]

[0088] In the formula, U A is the actual nitrogen absorption (g N m -2 d -1 ), f θ is the soil moisture limitation factor, which is related to the soil water content θ and the wilting coefficient θ w , and S N is the soil nitrogen storage (g N m -2 ). The part after deducting the crop absorption is the environmental surplus of nitrogen, which is also the direct cause of non-point source nitrogen pollution in the basin.

[0089] Step 3: Read the hydrological simulation information using the Network Common Data Form (netCDF).

[0090] All hydrological information calculated by the hydrological model is stored in the Network Common Data Form - netCDF. This method reads the corresponding hydrological simulation information of the netCDF file through the variable names specified in the general interface file. Therefore, the variable names in the netCDF file must correspond one by one to the variable names specified in the general interface file.

[0091] The time series data obtained from the EcH2O-iso and mHM models include: (1) the meteorological driving input data of the models, including precipitation, temperature, humidity, solar radiation, etc.; (2) the state variables and hydrological process fluxes calculated by the hydrological model, such as evapotranspiration in each calculation period, soil moisture dynamics in each layer, runoff components, and channel flow, etc.

[0092] Step 4: Simulate the temporal and spatial dynamic changes of nitrogen in the basin.

[0093] The transport process of nitrogen in the basin is mainly driven by the hydrological process. Therefore, according to the basic information of the basin configured in Step 1 and the coupled hydrological model structure, the model structure for nitrogen simulation needs to be matched, including the landscape types (land use, soil type, etc.) and their area proportions within the basic calculation unit, the soil layering settings (number of layers and depths of each layer), etc.

[0094] After determining the nitrogen model structure, according to the analysis results of agricultural nitrogen source input characteristics in Step 2, the agricultural nitrogen source input to the water storage bodies in each soil layer is configured (usually distributed to the first and second soil water storage bodies according to a given ratio). In addition, the initial values of the dissolved nitrogen concentration in each water storage body must be given, and a certain preheating period is generally set in the simulation calculation to obtain more reasonable initial values.

[0095] During the simulation of the temporal and spatial dynamics of nitrogen, according to the principle of mass balance, based on the hydrological information in Step 3, dissolved nitrogen undergoes storage-flux exchange in the vertical direction (hydraulic connection between different water storage bodies within the same basic calculation unit) and the horizontal direction (hydraulic connection between water storage bodies in different calculation units) along with the water flow. This method assumes that all nitrogen input items are completely mixed in the water storage body within the calculation period. Therefore, the dissolved nitrogen concentration of the water storage body output item is the nitrogen concentration of the water storage body at the end of the period.

[0096] While nitrogen is transported on the land surface of the basin, complex biogeochemical transformation processes also occur. In this method, the main forms of soil nitrogen in the basin considered in each soil layer are dissolved inorganic nitrogen (DIN), dissolved organic nitrogen (DON), solid easily degradable organic nitrogen (SON a ) and non-degradable organic nitrogen (SON i ). The biogeochemical transformation processes between them, including activation (R 活化 , gNm -2 d -1 ), mineralization (R 活化 , gNm -2 d -1 ), dissolution (R 溶解 , gNm -2 d -1 ), and denitrification of nitrate nitrogen under anaerobic conditions (R 反硝化 , gNm-2 d -1 ) is calculated as follows:

[0097] R 活化 = r degdt ·f st ·f sm ·S SONi

[0098] R 矿化 = r minrl ·f st ·f sm ·(S DON + S SONa )

[0099] R 溶解 = r dissl ·f st ·f sm ·S SONa

[0100] R 反硝化 = r denis ·f st ·f sm ·f smc ·S DIN

[0101] In the formula, r degdt , r minrl , r dissl , r denis represent the conversion rates (d -1 ) of each process and are parameters introduced as the model; S SONi , S DON , S SONa , S DIN are the storage amounts (g N m -2 ) of various soil nitrogen; f st , f sm , f smc are respectively the influencing factors of soil temperature (st), soil moisture (sm), and soil water N concentration (smc), and are calculated as follows:

[0102]

[0103] In the formula, sm_sat is the saturated soil water content.

[0104] The non-point source nitrogen enters the river along with the hydrological process of the basin and also undergoes conversion in the river. The forms of nitrogen in the river water considered in each calculation section of this method are dissolved organic nitrogen (DON w ) and dissolved inorganic nitrogen (DIN w) Considering both the river channel photosynthetic assimilation process and the denitrification process simultaneously. The photosynthetic assimilation process (U gpp , mg N / m -2 / d -1 ) mainly considers the photosynthesis of algae and is closely related to the primary productivity of the river. Its generalized calculation method is as follows:

[0105] U gpp = U amax ·f GR ·(1 - f LAI )

[0106] In the formula, U amax is the maximum photosynthetic absorption (which can be directly determined according to measured data or used as a model parameter); in this embodiment, it is determined as 283 mg N / m -2 / d -1 according to the measured data of the case basin; f GR is the photosynthetic radiation factor (the value range is [0, 1], obtained by normalizing the measured photosynthetically active radiation data); f LAI is the river channel vegetation canopy shading factor (the value range is [0, 1], obtained by normalizing the measured leaf area index - LAI of the river channel vegetation along the way). The river channel denitrification process (R 河道反硝化 , mg N / m -2 / d -1 ) is calculated as follows:

[0107] R 河道反硝化 = r deniw ·f wt ·f wnc

[0108] In the formula, r deniw is the river channel denitrification rate (mg N / m -2 / d -1 ), which participates in the calibration as a model parameter; f wt and f wnc are the influencing factors of river channel water temperature and river water nitrate nitrogen concentration respectively, and the estimation methods are the same as those of the above - mentioned soil temperature and concentration.

[0109] This method supports a flexible parameterization scheme to fully characterize the spatial heterogeneity of the basin characteristics. The introduced model parameters can be classified according to the basin landscape type (such as land use type or soil type); in addition, the basin landscape types can be merged to reduce the number of parameters that need to be calibrated in the model (for example, the land use types can be merged into two types: agricultural type and non - agricultural type). In the embodiment, the introduced parameters r degdt , r minrl , r dissl , r denis and r deniwAll are defined as land - use - type - dependent and are further integrated into two major categories: agricultural and non - agricultural. That is, the same process parameters are calibrated as two independent parameters under agricultural and non - agricultural land uses.

[0110] In this implementation case, the coupled simulation of basin hydrology and water quality was carried out by coupling two hydrological models, EcH2O - iso and mHM. Figure 3 For the dynamic changes of simulated nitrate - nitrogen concentration under the two coupled models at the outlet of the case basin during 2012 - 2018 and their comparison with the measured values. The upper small figure is the flow at the outlet of the basin, and the lower small figure is the simulation result of nitrate concentration. Figure 4 For the spatial distribution of land - surface nitrogen balance terms in the case basin under the two coupled models. The results show that the simulated river nitrate - nitrogen concentrations at the outlet of the basin by the two coupled models both have high accuracy (the Kling - Gupta Efficiency coefficient KGE reaches above 0.70, and the bias PBIAS is within ±11.5%); meanwhile, the spatio - temporal distributions of each nitrogen balance term in the simulated basin also have good consistency.

[0111] Step 5: Identify the high - risk periods and high - risk areas of non - point - source nitrogen pollution.

[0112] Based on the spatio - temporal dynamic simulation of basin nitrogen in Step 4, this method is applicable to continuous calculation on a daily scale. Therefore, it can provide continuous simulation results of the discharge of land - surface nitrogen in the basin into receiving waters such as rivers, so as to effectively identify the high - risk periods of non - point - source nitrogen pollution.

[0113] This method can conveniently simulate the spatial distribution and dynamic changes of basin nitrogen balance, and provides the output function of the dynamic intermediate state of basin nitrogen (such as nitrogen absorption by crops / vegetation, absorption amount in the denitrification process, soil nitrogen storage, land - surface output with runoff, etc.). These refined simulation information helps to identify the high - risk sub - areas of non - point - source nitrogen pollution.

[0114] For these high - risk periods and high - risk areas, this method can be used to evaluate the improvement effects of non - point - source nitrogen pollution in the basin under different treatment measures, providing a scientific basis for the refined prevention and control of the basin.

[0115] From Figure 3 the daily - scale dynamic change pattern of nitrate - nitrogen concentration at the basin outlet, it can be seen that the surface - water nitrate - nitrogen concentration in the case basin shows significant seasonal changes. High concentrations generally occur from December to May, and the concentration reaches about 4mgNl -1。Meanwhile, the seasonal pattern of concentration is highly consistent with the seasonal variation of flow. This is because the nitrogen enriched in the basin is mainly driven by the intense hydrological processes during the rainy season and is discharged from the land surface to the river water body. Thus, it can be seen that the high-risk period for the formation of non-point source nitrogen pollution in the case basin is the rainy season or flood period when the hydrological processes are relatively active. Further, from Figure 4 the results of the spatial distribution of basin nitrogen, it can be seen that there is also significant spatial heterogeneity in the enrichment of basin nitrogen and non-point source nitrogen pollution. Due to the influence of human agricultural activities, the level of nitrogen in agricultural land in the basin is much higher than that in forest areas. Therefore, these areas are also high-risk areas for non-point source nitrogen pollution in the basin.

[0116] This case shows that the basin nitrogen simulation method provided by the present invention can well adapt to different hydrological model structures and can accurately simulate the spatio-temporal dynamic changes of basin nitrogen. Therefore, this method provides a flexible and general non-point source nitrogen pollution simulation tool for the basin, which can provide a scientific basis for the comprehensive assessment of basin water quantity - water quality and strong technical support for the research and refined prevention and control of non-point source nitrogen pollution in the basin.

[0117] Based on the same technical concept as the method embodiment, the present invention also provides a general non-point source nitrogen pollution simulation system for the basin, including:

[0118] A hydrological model and basin basic information configuration module, which is used to obtain the type and model structure of the coupled hydrological model configured by the user through a general interface, and obtain the basin basic information configured according to the corresponding format requirements, including: the designation of the distributed or semi-distributed model type; the input data of the basin basic information configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body configured based on the general water storage body storage - flux interaction structure;

[0119] A basin agricultural nitrogen characteristic extraction module, which is used to obtain the input of basin agricultural nitrogen sources configured by the user through a general interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the basin, estimate the crop nitrogen uptake using the empirical growth curve method based on three parameters, and identify the environmental surplus and its spatio-temporal characteristics after nitrogen fertilizer is absorbed by the crops;

[0120] A hydrological simulation information reading module, which is used to read the hydrological process simulation information calculated according to the hydrological model through a general interface file, including meteorological driving data, hydrological processes, and intermediate state variable information;

[0121] The basin nitrogen spatio-temporal simulation module is used to simulate the spatio-temporal dynamic changes of basin nitrogen under the drive of hydrological processes, based on the description method and parameterization scheme of nitrogen transport and transformation processes, including: matching the basic information of the basin with the input characteristics of agricultural nitrogen sources to determine the nitrogen model structure; based on the nitrogen model structure, the spatio-temporal characteristics of agricultural nitrogen input in the basin, and the hydrological process simulation information, determining the biogeochemical transformation processes between different nitrogen forms and their generalized description methods, constructing a coupled hydrological and water quality model, and conducting spatio-temporal dynamic simulation of basin nitrogen.

[0122] The risk identification module is used to analyze the simulation results and identify the high-risk periods and high-risk areas of non-point source nitrogen pollution, including: identifying the high-risk periods from the dynamic changes in the nitrate-nitrogen concentration at the key cross-sections of the river; identifying the high-risk areas from the spatial distribution of the nitrogen balance in the basin.

[0123] It should be understood that the generalized basin non-point source nitrogen pollution simulation system in the embodiments of the present invention can implement all the technical solutions in the above method embodiments. The functions of its various functional modules can be specifically implemented according to the methods in the above method embodiments, and the specific implementation process can refer to the relevant descriptions in the above embodiments, which will not be elaborated here.

[0124] The present invention also provides a computer device, including: one or more processors; a memory; and one or more programs, where the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the generalized basin non-point source nitrogen pollution simulation method described above are implemented.

[0125] The present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the generalized basin non-point source nitrogen pollution simulation method described above are implemented.

[0126] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a device (system), a computer device, or a computer program product. Therefore, the present invention can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0127] The present invention is described with reference to the flowchart of a method according to an embodiment of the present invention. It should be understood that each process in the flowchart and the combination of processes in the flowchart can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in one process Figure 1 or a plurality of processes.

[0128] 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 an instruction device that implements the functions specified in one process Figure 1 or a plurality of processes.

[0129] 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, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one process Figure 1 or a plurality of processes.

Claims

1. A universal method for simulating non-point source nitrogen pollution in a watershed, characterized in that: The following steps are involved: Step 1: Through the universal interface provided by the universal watershed non-point source nitrogen pollution simulation system, obtain the type and model structure of the coupled hydrological model configured by the user, and obtain the basic information of the watershed configured according to the corresponding format requirements, including: the specification of the distributed or semi-distributed model type; the input data of the basic information of the watershed configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water body configured based on the universal water body storage-flux interaction structure; the universal interface supports the configuration of the structure of different hydrological models and the corresponding Variable names support the configuration of all conceptual water bodies and their input and output items included in different hydrological models; the generalized water body storage-flux interaction structure includes input from the upper water tank, output to the upper water tank, input from the lower water tank, output to the lower water tank, lateral input from the same-layer water tank of the upstream calculation unit and lateral output to the same-layer water tank of the downstream unit, and considers additional flux input and output; when coupling a specified hydrological model, all conceptual water bodies included in the model are specified in the generalized interface, and the input and output items of each water body are configured by specifying the variable name of each variable; Step 2: Obtain the user-configured watershed agricultural nitrogen source input through a universal interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the watershed, estimate crop nitrogen absorption using a three-parameter empirical growth curve method, and identify the environmental surplus after nitrogen fertilizer is absorbed by crops and its spatiotemporal characteristics; Step 3: Read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological process and intermediate state variable information; Step 4: Driven by the hydrological process, based on the description method and parameterization scheme of nitrogen transport and transformation process, simulate the spatiotemporal dynamic changes of nitrogen in the basin, including: matching the basic information of the basin with the characteristic information of agricultural nitrogen source input to determine the nitrogen model structure; based on the nitrogen model structure, the spatiotemporal characteristics of agricultural nitrogen input in the basin, and the hydrological process simulation information, determine the biogeochemical transformation process between different nitrogen forms and its generalized description method, build a hydrological and water quality coupling model, and simulate the spatiotemporal dynamics of nitrogen in the basin; Step five: Analyze the simulation results and identify high-risk periods and high-risk areas for non-point source nitrogen pollution, including: identifying high-risk periods from the dynamic changes in nitrate nitrogen concentrations in key sections of the river; identifying high-risk areas from the spatial distribution of nitrogen balance in the watershed.

2. The method according to claim 1, characterized in that The types of hydrological models include fully distributed models and semi-distributed models. The generalized interface supports the configuration of watershed discretization schemes. For fully distributed models, regular grids are used as basic calculation units for discretization processing. For semi-distributed models, sub-watersheds are used for spatial discretization, and hydrological response units are defined in sub-watersheds according to geographical landscape types. The basic information of the watershed includes one or more of elevation, flow direction, slope, land cover, and soil type.

3. The method according to claim 1, characterized in that The method of estimating crop nitrogen absorption by using an empirical growth curve method based on three parameters includes: The theoretical nitrogen absorption of crops is calculated using the three-parameter empirical growth curve: help=(up1-up2)·e -up3·(ΔDS) Where U P is the nitrogen absorption capacity of the crop after sowing, up1, up2, and up3 are three empirical parameters of the growth curve, and ΔDS is the number of days from the current calculation time to the sowing date; Estimate the actual crop uptake by considering the limitations of soil moisture and nitrogen storage: IN A =min{U P ,f θ ·WITH N } Where U A is the actual nitrogen absorption, f θ is the soil moisture limiting factor, which is related to soil moisture content θ and wilting coefficient θ w Related, S N is the soil nitrogen storage.

4. The method according to claim 1, characterized in that: Read the hydrological process simulation information calculated by the hydrological model, including: According to the consensus that the hydrological process simulation information is stored in the network universal data format netCDF, the hydrological simulation information corresponding to the netCDF file is read by specifying the variable name in the universal interface file.

5. The method according to claim 1, characterized in that: Match the basic information of the watershed with the characteristic information of agricultural nitrogen source input to determine the structure of the nitrogen model; based on the structure of the nitrogen model, the spatiotemporal characteristics of agricultural nitrogen input in the watershed, and the hydrological process simulation information, determine the biogeochemical transformation process between different nitrogen forms and its generalized description method, build a hydrological and water quality coupling model, and conduct spatiotemporal dynamic simulation of nitrogen in the watershed, including: According to the basic information of the watershed and the coupled hydrological model structure configured in step 1, match the model structure of nitrogen simulation, including the landscape type and its area proportion within the basic calculation unit, and the soil stratification setting; After the nitrogen model structure is determined, the agricultural nitrogen source input of each soil layer water storage body is configured according to the results of the agricultural nitrogen source input characteristic analysis in step 2, and the initial value of the dissolved nitrogen concentration of each water storage body is given; According to the input-output items of each water storage body configured in step 1, a nitrogen spatiotemporal dynamic simulation process is performed, wherein according to the mass balance principle, based on the hydrological process simulation information in step 3, the dissolved nitrogen undergoes storage-flux exchange with the water flow in the vertical direction and the horizontal direction, wherein the vertical direction refers to the hydraulic connection between different water storage bodies in the same basic calculation unit, and the horizontal direction refers to the hydraulic connection between water storage bodies in different calculation units; According to the soil layer, the main forms of soil nitrogen are dissolved inorganic nitrogen DIN, dissolved organic nitrogen DON, solid and easily degradable organic nitrogen SON. a and non-degradable organic nitrogen SON i Four, establish the biogeochemical transformation processes between them, including: activation from non-degradable to easily degradable organic forms, mineralization from organic to inorganic forms, dissolution from easily degradable solid to dissolved forms, and denitrification of nitrate nitrogen under anaerobic conditions, and use reaction kinetics methods to quantitatively estimate the transformation amount; The nitrogen form of the river water considered in each calculated river section is dissolved organic nitrogen (DON). w and dissolved inorganic nitrogen DIN w , while considering the photosynthetic absorption process and denitrification process in the river channel, and performing generalized calculations.

6. The method according to claim 5, characterized in that The reaction kinetics method is used to quantitatively estimate the conversion amount, including: R 活化 Indicates the activation from non-degradable to readily degradable organic forms, R 矿化 Represents the mineralization from organic to inorganic forms, R 溶解 represents the dissolution from a readily degradable solid to a soluble state, R 反硝化 It represents the denitrification of nitrate nitrogen under anaerobic conditions and is calculated as follows: R 活化 =r degdt ·f st ·f sm ·S SONi R 矿化 =r minrl ·f st ·f sm ·(S DON +S SONa ) R 溶解 =r dissl ·f st ·f sm ·S SONa R 反硝化 =r denis ·f st ·f sm ·f smc ·S DIN In the formula, r degdt 、r minrl 、r dissl 、r denis Represents the conversion rate of each process, as a parameter introduced into the model; S SONi , S DON , S SONa , S DIN is the storage amount of nitrogen in various soils; st 、f sm 、f smc They are soil temperature influencing factor, soil moisture influencing factor and soil water and nitrogen concentration influencing factor; Take U gpp represents the photosynthetic absorption process, R 河道反硝化 It represents the denitrification process in the river channel, and its generalized calculation method is as follows: U gpp =U amax ·f GR ·(1-f LAI ) R 河道反硝化 =r deniw ·f wt ·f wnc Where U amax is the maximum photosynthetic absorption; f GR is the photosynthetic radiation factor; f LAI is the canopy shading factor of river vegetation, r deniw is the river denitrification rate, used as a model parameter; f wt and f wnc are the influencing factors of river water temperature and river water nitrate nitrogen concentration respectively.

7. The method according to claim 1, characterized in that Identify high-risk periods from the dynamic changes in nitrate nitrogen concentrations in key river sections; Based on the spatial distribution of nitrogen balance in the watershed, high-risk areas were identified, including: Based on the spatiotemporal dynamic simulation of nitrogen in the basin, continuous calculations are performed on a daily scale to provide continuous simulation results of nitrogen discharge from the basin's land surface to receiving water bodies and identify high-risk periods for non-point source nitrogen pollution; Based on the output function of the dynamic intermediate state of nitrogen in the basin, including one or more of the crop nitrogen absorption, denitrification absorption, soil nitrogen storage, and land surface output with runoff, the spatial distribution and dynamic changes of the basin's nitrogen balance are simulated to identify high-risk sub-areas for non-point source nitrogen pollution.

8. A universal basin non-point source nitrogen pollution simulation system, characterized in that: include: The hydrological model and basin basic information configuration module is used to obtain the type and model structure of the coupled hydrological model configured by the user through a universal interface, and obtain the basin basic information configured according to the corresponding format requirements, including: the specification of the distributed or semi-distributed model type; the basin basic information input data configured according to the corresponding format requirements of the model; the configuration of the specific structure of the coupled hydrological model; the input-output items of each water storage body based on the universal water storage body storage-flux interaction structure configuration; the universal interface supports the configuration of the structure of different hydrological models and the corresponding variable names It supports the configuration of all conceptual water bodies and their input and output items contained in different hydrological models; the generalized water body storage-flux interaction structure includes input from the upper water tank, output to the upper water tank, input from the lower water tank, output to the lower water tank, lateral input from the same-layer water tank of the upstream calculation unit and lateral output to the same-layer water tank of the downstream unit, and considers additional flux input and output; when coupling a specified hydrological model, all conceptual water bodies contained in the model are specified in the generalized interface, and the input and output items of each water body are configured by specifying the variable name of each variable; The watershed agricultural nitrogen feature extraction module is used to obtain the user-configured watershed agricultural nitrogen source input through a universal interface, determine the spatial distribution of crop types and rotation sequences based on the spatial distribution map of crop rotation types in the watershed, estimate crop nitrogen absorption using the empirical growth curve method based on three parameters, and identify the environmental surplus and its spatiotemporal characteristics after nitrogen fertilizer is absorbed by crops; The hydrological simulation information reading module is used to read the hydrological process simulation information calculated by the hydrological model, including meteorological driving data, hydrological process and intermediate state variable information; The spatiotemporal simulation module of nitrogen in the watershed is used to simulate the spatiotemporal dynamic changes of nitrogen in the watershed driven by hydrological processes, based on the description method and parameterization scheme of nitrogen transport and transformation processes, including: matching basic information of the watershed with characteristic information of agricultural nitrogen source input to determine the structure of the nitrogen model; based on the structure of the nitrogen model, the spatiotemporal characteristics of agricultural nitrogen input in the watershed, and the simulation information of the hydrological process, determining the biogeochemical transformation process between different nitrogen forms and its generalized description method, constructing a hydrological and water quality coupling model, and conducting spatiotemporal dynamic simulation of nitrogen in the watershed; The risk identification module is used to analyze simulation results and identify high-risk periods and high-risk areas for non-point source nitrogen pollution, including: identifying high-risk periods from the dynamic changes in nitrate nitrogen concentrations in key sections of rivers; and identifying high-risk areas from the spatial distribution of nitrogen balance in the watershed.

9. A computer device, characterized in that: include: one or more processors; Memory; And one or more programs, wherein the one or more programs are stored in the memory and are configured to be executed by the one or more processors, and when the programs are executed by the processors, the steps of the generalized watershed non-point source nitrogen pollution simulation method as described in any one of claims 1-7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the generalized watershed non-point source nitrogen pollution simulation method as described in any one of claims 1 to 7 are implemented.

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