A method, system, device and medium for evaluating dissolved organic nitrogen and phosphorus emissions

Abstract

The present invention provides an evaluation method, system, equipment and medium for the emission of dissolved organic nitrogen and phosphorus, which belongs to the field of analysis and simulation of organic nutrients entering the sea. The database of characteristic regions is constructed by acquiring characteristic region data, and the Global NEWS2 model is modified according to the soil transport attenuation coefficient, the river transport attenuation coefficient and the environmental factor to obtain an integrated sub-basin scale nutrient transport model ISNSM; sub-basins are divided and encoded in the ISNSM model to obtain the basin topology structure; the database data is extracted and input into the ISNSM model to simulate the transport process of DON and DOP in the basin, and the emission of organic nitrogen and phosphorus in each sub-basin is estimated. The model performs a full-factor dynamic simulation of the emission of organic nitrogen and phosphorus nutrients into the sea in the sub-basin by integrating multiple parameters of the sub-basin, and obtains the temporal and spatial distribution changes of organic nitrogen and phosphorus in the basin, which provides strong technical support and scientific basis for marine environmental protection and nutrient management.

Description

Technical Field

[0001] The invention belongs to the field of analysis and simulation of organic nutrients entering the sea, and specifically relates to an evaluation method, system, equipment and medium for the discharge of dissolved organic nitrogen and phosphorus. Background Art

[0002] In the context of global ecological and environmental protection, the impact of dissolved nitrogen, phosphorus and other nutrients transported by rivers on marine ecosystems has received increasing attention. Excessive input of terrestrial nitrogen and phosphorus nutrients can not only increase the primary productivity of the ocean, but also may lead to the formation of harmful algal blooms and hypoxic zones, seriously threatening marine biodiversity and water health. With the increase in agricultural activities, the discharge of nitrogen and phosphorus nutrients (including dissolved organic nitrogen DON and dissolved organic phosphorus DOP) has increased significantly. A large amount of nitrogen and phosphorus enters rivers through surface runoff and eventually flows into the ocean, causing serious impacts on coastal ecosystems. At present, the nutrients input into the ocean by rivers include inorganic nitrogen, phosphorus, and organic nitrogen and phosphorus, which have been proven to have a significant impact on the ecological health of coastal waters.

[0003] Therefore, accurately calculating and monitoring the discharge of terrestrial nitrogen and phosphorus nutrients into the sea is of vital importance for the formulation of environmental policies and the implementation of sustainable management measures. Although various models have been used to estimate the transport of nutrients and other pollutants, traditional nitrogen and phosphorus transport models are mainly used for annual statistical calculations of nitrogen and phosphorus fluxes in large-scale watersheds, ignoring local dynamic changes. Moreover, most of them focus on short-term events and small watersheds, making it difficult to accurately reflect the characteristics and spatiotemporal dynamics of organic nitrogen and phosphorus (DON, DOP) in complex hydrology and environment in long-term large-scale watersheds. Summary of the invention

[0004] In order to improve the accuracy of simulating the migration and transformation process of dissolved organic nitrogen and phosphorus and the problem of spatial variation, the present invention provides a method, system, equipment and medium for evaluating the emission of dissolved organic nitrogen and phosphorus.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for evaluating the emission of dissolved organic nitrogen and phosphorus comprises the following steps:

[0007] Acquire different types of data of characteristic regions to construct a database of characteristic regions; the different types of data specifically include socio-economic data, meteorological data, soil properties, DEM data, land use type, and parameters of dissolved organic nitrogen DON and dissolved organic phosphorus DOP;

[0008] The Global NEWS2 model is modified based on the influencing parameters to obtain the integrated sub-basin scale nutrient transport model ISNSM; the influencing parameters specifically include soil transport attenuation coefficient, river transport attenuation coefficient and environmental factors;

[0009] Extract river network and river flow direction data of characteristic areas based on the DEM data, perform sub-basin division on the ISNSM model, and obtain sub-basin division results of the characteristic areas; number the sub-basin division results to form a complete basin topology structure;

[0010] Socioeconomic data, meteorological data, soil properties, land use, and parameters of DON and DOP were input into the ISNSM model to simulate the transport process of DON and DOP in the basin and estimate the emissions of organic nitrogen and phosphorus in each sub-basin.

[0011] Preferably, the river transport attenuation coefficient is calculated by the following formula:

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] in, is the mineralization rate factor, is the mineralization rate constant, is the reservoir retention factor, is the reservoir capacity, is the inflow, is the dissolved oxygen concentration, is the hydraulic retention time of the reservoir, Human water extraction irrigation factor, is the initial river runoff, After taking water for human The runoff volume at is the flow rate attenuation factor, is the river width, is the river depth, is the river flow, is the distance from the source of the river to its mouth, is the distance attenuation coefficient, is the water temperature, is the optimum reaction temperature for mineralization, is the temperature sensitivity coefficient, is the attenuation factor of the distance from the estuary, is the temperature factor.

[0020] Preferably, the soil transport attenuation coefficient is calculated by the following formula:

[0021] ;

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] in, is the soil absorption factor; is the rainfall infiltration factor; is the biotransformation factor; is a chemical conversion factor; is the attenuation factor of the distance from the river; is the clay content of the soil; is the organic matter content; a and b are empirical calibration coefficients, which are set according to the soil characteristics and experimental data of the specific region; is the rainfall; is the permeability coefficient; is soil temperature; is the soil microbial activity index; is the soil pH; is the chemical reaction coefficient; is the distance attenuation coefficient; is the distance from the study unit to the nearest river; For the slope.

[0028] Preferably, the environmental factors include agricultural sources, urban sources, rural domestic wastewater sources and natural sources, and are calculated by the following formula:

[0029] The calculation formula of agricultural source DON and DOP is:

[0030]

[0031] in, Indicates the contribution of agricultural sources DON or DOP; It indicates the release coefficient of organic nitrogen and phosphorus in fertilizer application; Indicates the area where the fertilizer is used; It indicates the release coefficient of organic nitrogen and phosphorus in animal manure; Indicates the number of pigs, cattle, sheep, and chickens raised in livestock; It indicates the release coefficient of organic nitrogen and phosphorus in crop residues; Indicates the area covered by crop residues; It represents the organic nitrogen and phosphorus release coefficient in irrigation water; Indicates the amount of irrigation water return;

[0032] The calculation formulas for the urban source DON and DOP are:

[0033]

[0034] in, Represents the population of the city; is the GDP per capita; is the urbanization rate; It is an indicator of urban industrial activity; Represents the level of urban wastewater treatment; They represent the standardized output ratios of different industries;

[0035] The calculation formulas for DON and DOP of rural domestic wastewater sources are:

[0036]

[0037] in, It indicates the source of DON or DOP in rural residents’ domestic wastewater; It indicates the release coefficient of organic nitrogen and phosphorus in rural residents' domestic wastewater; It represents the total population of rural residents in the domestic wastewater treatment area; It represents the concentration of organic matter in wastewater from rural residents;

[0038] The calculation formula of the natural source DON and DOP is:

[0039]

[0040] in, Indicates the contribution of natural sources DON or DOP; It indicates the decomposition rate of litter of riparian vegetation; It represents the coverage area of ​​riparian vegetation; Represents the biomass of vegetation; Indicates the natural decomposition rate of organic nitrogen and phosphorus in the soil; represents the soil cover area;

[0041] The source acquisition equation of the environmental factors DON and DOP is:

[0042]

[0043] in, It indicates the total source of DON or DOP in the watershed; Indicates agricultural sources, including fertilizer application, animal manure; represents urban sources, including organic matter in urban runoff and discharge from sewage treatment plants; It represents organic nitrogen and phosphorus in rural domestic wastewater discharge; Indicates natural sources, including riverbank vegetation litter and natural decomposition of soil organic matter.

[0044] Preferably, the ISNSM model calculates the amount of dissolved organic nitrogen and phosphorus emissions in each sub-basin by the following formula:

[0045]

[0046] in, is Time The load of dissolved organic nitrogen and phosphorus exported to the estuary in each sub-basin; It represents the load of nutrient E from urban areas to surface water bodies; It represents the load of nutrient E from natural areas and rural areas to surface water bodies; It is the attenuation ratio of nutrient E affected by physical, chemical and biological processes during surface runoff transport; It is the attenuation ratio of nutrient E affected by various environmental factors during river runoff transportation.

[0047] Preferably, the sub-basin division results are numbered, specifically, the sub-basins are uniquely identified by the Pfastetter coding method, and each sub-basin is numbered according to the confluence order, and is numbered step by step from the source to the estuary; the topological relationship between the sub-basins is constructed, and the upstream and downstream relationship between each sub-basin and its adjacent basin is determined to form a complete basin topological structure; the sub-basin number reflects its relative position in the entire basin;

[0048] ;

[0049] in, Represents a sub-basin Serial number; A numbered sequence indicating the direction from source to mouth of a river.

[0050] Preferably, the method further comprises calculating the DON and DOP fluxes entering the ocean system after simulating the transport process of DON and DOP in the watershed, specifically by the following steps:

[0051] Input the model data of the target area into the ISNSM model to calculate the spatiotemporal distribution and migration paths of DON and DOP in different sub-basins; simulate the degradation, attenuation and ecological processes of DON and DOP in rivers, and calculate the removal rate of organic nutrients in rivers; simulate the retention and deposition process of DON and DOP in reservoirs, and calculate their deposition rates in reservoirs;

[0052] Based on the removal and deposition rates output by the model, combined with the structural characteristics of the watershed and river channel, the river discharge ratios of DON and DOP were calculated;

[0053] The final flux of DON and DOP into the ocean system was calculated using the removal rate of DON and DOP in rivers, the deposition rate in reservoirs and the proportion of their river discharge.

[0054] The present invention also provides a system for evaluating the emission of dissolved organic nitrogen and phosphorus, which specifically comprises:

[0055] A data module is used to obtain different types of data of characteristic areas to build a database of characteristic areas; the different types of data specifically include socio-economic data, meteorological data, soil properties, DEM data, land use types, and parameters of dissolved organic nitrogen DON and dissolved organic phosphorus DOP;

[0056] A model module is used to modify the Global NEWS2 model based on influencing parameters to obtain an integrated sub-basin scale nutrient transport model ISNSM; the influencing parameters specifically include soil transport attenuation coefficient, river transport attenuation coefficient and environmental factors;

[0057] A sub-basin division module is used to extract the river network and river flow direction data of the characteristic area based on the DEM data, perform sub-basin division on the ISNSM model, and obtain the sub-basin division result of the characteristic area; number the sub-basin division result to form a complete basin topology structure;

[0058] The evaluation module is used to input socio-economic data, meteorological data, soil properties, land use, and parameters of DON and DOP into the ISNSM model, simulate the transport process of DON and DOP in the basin, and estimate the emission of organic nitrogen and phosphorus in each sub-basin.

[0059] The present invention also provides a computer device, including a memory, a processor and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps described in the method for evaluating the emission of dissolved organic nitrogen and phosphorus.

[0060] The present invention also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is loaded by a processor, the steps described in the method for evaluating the emission of dissolved organic nitrogen and phosphorus can be executed.

[0061] The method for evaluating the emission of dissolved organic nitrogen and phosphorus provided by the present invention has the following beneficial effects:

[0062] The present invention constructs a database of characteristic regions by acquiring characteristic region data, and modifies the Global NEWS2 model according to the soil transport attenuation coefficient, the river transport attenuation coefficient and the environmental factor to obtain an integrated sub-basin scale nutrient transport model ISNSM, taking into account the influence of organic nitrogen and phosphorus transport under complex hydrological and environmental conditions, and more accurately simulates the migration and transformation process of organic nitrogen and phosphorus. Sub-basins are divided and encoded in the model to obtain a basin topology structure, which can reflect local dynamic changes and seasonal fluctuations in the region and improve the resolution in time and space. The database data is extracted and input into the ISNSM model to simulate the transport process of DON and DOP in the basin, and estimate the discharge of organic nitrogen and phosphorus in each sub-basin. The spatiotemporal dynamics of nitrogen and phosphorus in different basins are reflected, providing a decision-making basis for scientifically evaluating the impact of organic nitrogen and phosphorus on coastal ecosystems. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the embodiment of the present invention and its design scheme, the following briefly introduces the drawings required for this embodiment. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0064] Figure 1 The figure is a schematic diagram of the overall process of a method for evaluating the emission of dissolved organic nitrogen and phosphorus according to an embodiment of the present invention.

[0065] Figure 2 It is a schematic diagram of the sub-basin division process of a method for evaluating dissolved organic nitrogen and phosphorus emissions in an embodiment of the present invention.

[0066] Figure 3 This is a graph showing the risk index results of nitrogen and phosphorus nutrient transport in different regions in an embodiment of the present invention. DETAILED DESCRIPTION

[0067] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the scope of protection of the present invention.

[0068] Example

[0069] The present invention provides a method for evaluating the emission of dissolved organic nitrogen and phosphorus. Figure 1 As shown, the specific steps include the following steps.

[0070] Step 1: Collect economic and cultural data, land-related data, and river hydrological data of the study area - the Bohai Rim.

[0071] The digital elevation model (DEM) data uses 30-meter resolution elevation data released by Shuttle Radar Topography Mission (SRTM) to calculate the impact of terrain slope. Land use data comes from the GlobeLand30 surface cover dataset with a spatial resolution of 30 meters. Population spatial distribution data comes from the LandScan global population distribution database, with a time range of 2010 to 2022 and a spatial resolution of 1 km. Administrative division data comes from the National Basic Geographic Information Database. River spatial information data uses the HydroSHEDS hydrological dataset, which is approved based on the fourth- and fifth-level rivers in the National Basic Geographic Information Database; in addition, the determination of provincial, municipal, and county-level administrative boundaries also comes from the National Basic Geographic Information Database. Statistical yearbooks of socioeconomic data such as the gross output value of the primary, secondary, and tertiary industries, the application of nitrogen and phosphorus fertilizers, the number of livestock and poultry breeding, and the area and harvest of crops. Soil data uses the HWSD global soil database and national soil survey data. Rainfall data comes from the China Ground Climate Data Daily Dataset (V3.0). The river nitrogen and phosphorus load data comes from the river basin nitrogen and phosphorus pollutant monitoring data set of the Ecological Environment Research Center, covering the nitrogen and phosphorus pollution loads of the main river basins in the Bohai Rim region.

[0072] Step 2: Construct an Integrated Subbasin-scale Nutrient to Sea Management Model (ISNSM). Traditional nitrogen and phosphorus transport models mainly focus on the annual calculation of nitrogen and phosphorus fluxes in large-scale watersheds, ignoring the detailed dynamic changes at the local scale and the specific behaviors of organic nitrogen and phosphorus DON and organic phosphorus DOP under complex hydrological conditions. New parameters were introduced into the Global NEWS2 model to obtain the ISNSM model, including soil transport attenuation coefficients, river transport attenuation coefficients and a variety of environmental factors (including temperature, precipitation, soil properties, etc.), so that the model can more accurately simulate the migration and transformation process of DON and DOP in soil and water. Among them, the model's assessment of emissions is specifically reflected in the estimation of the flux of DON and DOP into the sea.

[0073] Among them, the soil transport attenuation coefficient is calculated by the following formula:

[0074] ;

[0075] ;

[0076] ;

[0077] ;

[0078] ;

[0079] ;

[0080] in, is the soil absorption factor; is the rainfall infiltration factor; is the biotransformation factor; is a chemical conversion factor; is the attenuation factor of the distance from the river; is the clay content of the soil; is the organic matter content; a and b are empirical calibration coefficients, which are set according to the soil characteristics and experimental data of the specific region; is the rainfall; is the permeability coefficient; is soil temperature; is the soil microbial activity index; is the soil pH; is the chemical reaction coefficient; is the distance attenuation coefficient; is the distance from the study unit to the nearest river; For the slope.

[0081] The river transport attenuation coefficient is calculated by the following formula:

[0082]

[0083]

[0084]

[0085]

[0086]

[0087]

[0088]

[0089] in, is the mineralization rate factor, is the mineralization rate constant, is the reservoir retention factor, is the reservoir capacity, is the inflow, is the dissolved oxygen concentration, is the hydraulic retention time of the reservoir, Human water extraction irrigation factor, is the initial river runoff, After taking water for human The runoff volume at is the flow rate attenuation factor, is the river width, is the river depth, is the river flow, is the distance from the source of the river to its mouth, is the distance attenuation coefficient, is the water temperature, is the optimum reaction temperature for mineralization, is the temperature sensitivity coefficient, is the attenuation factor of the distance from the estuary, is the temperature factor.

[0090] Environmental factors specifically include agricultural sources, urban sources, rural domestic wastewater sources and natural sources, and are calculated using the following formula:

[0091] The calculation formula for agricultural source DON and DOP is:

[0092]

[0093] in, Indicates the contribution of agricultural sources DON or DOP; It indicates the release coefficient of organic nitrogen and phosphorus in fertilizer application; Indicates the area where the fertilizer is used; It indicates the release coefficient of organic nitrogen and phosphorus in animal manure; Indicates the number of pigs, cattle, sheep, and chickens raised in livestock; It indicates the release coefficient of organic nitrogen and phosphorus in crop residues; Indicates the area covered by crop residues; It represents the organic nitrogen and phosphorus release coefficient in irrigation water; Indicates the amount of irrigation water return.

[0094] The calculation formula for urban source DON and DOP is:

[0095]

[0096] in, Represents the population of the city; is the GDP per capita; is the urbanization rate; It is an indicator of urban industrial activity; Represents the level of urban wastewater treatment; They represent the standardized output ratios of different industries.

[0097] The calculation formula for DON and DOP of rural domestic wastewater sources is:

[0098]

[0099] in, It indicates the source of DON or DOP in rural residents’ domestic wastewater; It indicates the release coefficient of organic nitrogen and phosphorus in rural residents' domestic wastewater; It represents the total population of rural residents in the domestic wastewater treatment area; Represents the concentration of organic matter in rural residential wastewater.

[0100] The calculation formula of natural source DON and DOP is:

[0101]

[0102] in, Indicates the contribution of natural sources DON or DOP; It indicates the decomposition rate of litter of riparian vegetation; It represents the coverage area of ​​riparian vegetation; Represents the biomass of vegetation; Indicates the natural decomposition rate of organic nitrogen and phosphorus in the soil; Represents the soil cover area.

[0103] The source acquisition equation of environmental factors DON and DOP is:

[0104]

[0105] in, It indicates the total source of DON or DOP in the watershed; Indicates agricultural sources, such as fertilizer application, animal manure; represents urban sources, such as organic matter in urban runoff and discharge from sewage treatment plants; It represents organic nitrogen and phosphorus in rural domestic wastewater discharge; Indicates natural sources, such as riverbank vegetation litter and natural decomposition of soil organic matter.

[0106] Compared with traditional models, the ISNSM model has been refined in terms of time dimension. It is no longer limited to the calculation of annual fluxes, but can simulate monthly changes in organic nitrogen and phosphorus transport, capturing seasonal fluctuations and short-term impacts of human activities. In terms of spatial dimension, the ISNSM model divides sub-basins more scientifically and accurately through the logical topological structure of upstream and downstream transport, and accurately calculates nitrogen and phosphorus losses and fluxes into the sea at the county (district) and township (street) levels. This refined spatial division enables the model to reflect the local pollution dynamics in the region, help identify specific pollution sources, and provide more accurate governance measures. At the same time, the model also integrates multiple spatial variables such as topography, land use, precipitation, and human activities, and fully considers the complex source-sink relationship. Not only does it improve the simulation accuracy of nitrogen and phosphorus migration and transformation processes, but it also achieves higher resolution in time and space, enabling the model to more comprehensively evaluate the impact of nitrogen and phosphorus on the ecosystem, providing important technical support for environmental governance and watershed management.

[0107] Step 3: Sub-basin division. Figure 2 As shown in the figure, the constructed ISNSM model is used to combine the topography, rainfall, water system distribution and other data of the study area to carry out fine sub-basin division of the basin.

[0108] First, the flow direction of each grid cell is calculated based on the digital elevation model DEM data. The flow direction determines the path of water flowing from high to low. Based on the flow direction data, the water volume of each grid cell is calculated, which represents the accumulation of water flowing from upstream to downstream. According to the cumulative water volume, the main river network is extracted, the river threshold value (that is, the density of the river network in the basin) is set, and the river channel is defined. Sub-basins are divided according to the river network extraction results and flow direction data. The boundary of each sub-basin is defined as the area in the catchment area that flows to the same outflow point. The Pfastetter method is used to number the sub-basins, which are numbered step by step from downstream to upstream according to the catchment path, and the distance from the confluence of the largest tributary to the estuary is considered. The numbering of the sub-basin reflects its relative position in the entire basin:

[0109] ;

[0110] in, Represents a sub-basin Serial number; A numbered sequence indicating the direction from source to mouth of a river.

[0111] After completing the sub-basin division, the topological structure is constructed based on the upstream and downstream relationships between the sub-basins. This process uses the logical relationship between the confluence point and the outflow point of each sub-basin.

[0112] By dividing the sub-basins according to the topological structure, the model can reflect the dynamics of nitrogen and phosphorus migration and loss in the local area, providing a high-resolution spatial basis for subsequent flux calculations.

[0113] Step 4: Calculation of nitrogen and phosphorus fluxes. The constructed ISNSM model is used in combination with the collected soil properties, land use, and meteorological data to simulate the transport process of DON and DOP from land to rivers and then to the ocean, accurately estimate the nutrient flux to the sea in each sub-basin, and capture seasonal changes and long-term trends.

[0114] The nitrogen and phosphorus transport process in the ISNSM model can be divided into three steps, as follows:

[0115] Step 1: Quantify the source generation, transport and transformation process of DON and DOP on land.

[0116] This step quantifies the source generation-migration-transformation process of DON and DOP under different land use types by simulating the loss, adsorption and transformation of organic nitrogen and phosphorus in the soil. Considering factors such as soil properties, vegetation cover, rainfall and temperature, the spatial distribution and migration dynamics of organic nitrogen and phosphorus on land are evaluated.

[0117] Step 2: Quantify organic nitrogen and phosphorus inputs from land to sub-basin rivers.

[0118] This phase mainly quantifies the process of organic nitrogen and phosphorus migration from soil to sub-basin rivers, taking into account the effects of temperature, soil permeability and surface runoff on the retention and loss of organic nitrogen and phosphorus. Runoff is considered an important transport pathway for organic nitrogen and phosphorus from land into the river system. The model simulates the nitrogen and phosphorus transport process in each sub-basin by inputting meteorological and land use data.

[0119] Step 3: Quantify the organic nitrogen and phosphorus at the outlet of each sub-basin.

[0120] In this step, the model quantifies the DON and DOP fluxes at the outlet according to the characteristics of each sub-basin and seasonal variation. Organic nitrogen and phosphorus retention and loss in the river are considered to be a function of multiple factors, including nitrification / mineralization, sediment adsorption / desorption, reservoir deposition / re-suspension, and anthropogenic water withdrawal activities. Finally, the model classifies nitrogen and phosphorus losses from different sources and provides high-precision calculations of nutrient outputs in combination with seasonal effects.

[0121] The ISNSM model mainly simulates and calculates the nitrogen and phosphorus fluxes into the sea in the basin through five logical processes. The first is to quantify the amount of nutrients generated from the source (in GIS, point sources are recorded as points and non-point sources are recorded as areas), the second is to quantify the load of nutrients lost from pollution sources to surface runoff, the third is to quantify the load of nutrients output from surface runoff to the nearest river channel, the fourth is to quantify the load of nutrients from entering the river channel to the outlet of the sub-basin, and the fifth is to quantify the load of nutrients output from the outlet of the sub-basin to the estuary. The output result is the calculation result of the above five steps. The general formula is:

[0122]

[0123] in, is Time The load of dissolved organic nitrogen and phosphorus exported to the estuary in each sub-basin; It represents the load of nutrient E from urban areas to surface water bodies; It represents the load of nutrient E from natural areas and rural areas to surface water bodies; It is the attenuation ratio of nutrient E affected by physical, chemical and biological processes during surface runoff transport; It is the attenuation ratio of nutrient E affected by various environmental factors during river runoff transportation.

[0124] ① In the first step of calculating the generation, migration and transformation of organic nitrogen and phosphorus sources, clarifying the source generation is of great significance to the subsequent processes.

[0125]

[0126] The calibration parameters , The value is determined according to the city's economic output, and the value of the calibration parameter is directly related to the city's economic output. The higher the economic output of a city, the greater its potential contribution to industrial and domestic emissions, so higher calibration parameters are needed to accurately reflect the emission intensity of pollutants such as nitrogen and phosphorus. By adjusting the calibration parameters, the accuracy of the ISNSM model's simulation of nitrogen and phosphorus nutrient emissions in different cities can be improved. The values ​​of cities of different levels are shown in Table 1.

[0127] Table 1 Calibration parameters of nitrogen and phosphorus production in cities with different economic levels

[0128]

[0129] ② The parameter values ​​of soil transport attenuation coefficient are set for different blocks in the Bohai Rim region. Combined with regional soil characteristics, rainfall, temperature, pH value and other environmental factors, the Bohai Rim region is divided into different blocks according to soil type, terrain slope, meteorological conditions and other factors. Block 1: coastal plain areas (such as Tianjin and Qinhuangdao); Block 2: hilly areas (such as Yantai and Dalian); Block 3: mountainous and heavy industrial areas (such as Tangshan and Beijing); The final values ​​in parameter calibration are shown in Table 2.

[0130] Table 2 Optimal values ​​of parameters for organic nitrogen and phosphorus transport attenuation in soil

[0131]

[0132] Among them, soil absorption factor: reflects the adsorption of organic nitrogen and phosphorus by clay content (clay%) and organic matter content (OM%) in the soil. In plain areas, the clay content is high, so the a value is larger, while in hills and mountains, the clay content is low and the proportion of organic matter is relatively high, so the b value increases. Rainfall infiltration factor: a factor determined by rainfall and soil permeability. The permeability in plain areas is relatively good, and the rainfall infiltration factor is small, while in hills and mountains, the permeability is poor, so the permeability factor increases. Biotransformation factor: a factor that takes into account soil temperature and microbial activity. The rate of biotransformation increases with increasing temperature. The temperature in plain areas is relatively high, so the conversion rate is faster, while in mountainous areas, the temperature is low and the biotransformation effect is weaker. Chemical transformation factor: determined by the pH value of the soil, which affects the chemical reaction rate of organic nitrogen and phosphorus. When the pH value deviates from 7, the chemical reaction rate increases. The pH value in mountainous areas may fluctuate due to industrial activities, so the chemical transformation factor is larger. Distance attenuation factor from the river: Based on the distance and slope from the study unit to the river, the greater the slope, the faster the runoff rate and the faster the loss of nutrients, so the attenuation coefficient is higher in mountainous areas and lower in plain areas.

[0133] By dividing the Bohai Rim region into different blocks, we can provide reference values ​​for each factor in the soil transport attenuation coefficient according to actual environmental conditions, so as to more accurately evaluate the migration, adsorption and transformation processes of organic nitrogen and phosphorus.

[0134] ③ The river transport attenuation coefficient measures the absorption, transformation and retention process of DON and DOP in the river from the source to the estuary. In addition to dividing the river system according to the terrain (such as plains, hills, mountains, etc.), it can also be divided based on other hydrological, geological or ecological characteristics. For the Bohai Rim region, the river system can be divided according to the distribution of pollution sources and hydrodynamic conditions. The division standard of pollution source distribution and hydrodynamic conditions can effectively combine the actual pollution situation in the Bohai Rim region, especially under the differences in industrial, agricultural and urban emission sources faced by different river sections, and reasonably set different parameter values. This division method is more suitable for evaluating the attenuation and transport process of nutrients (such as DON and DOP) in rivers.

[0135] Table 3 Optimal values ​​of parameters for organic nitrogen and phosphorus transport attenuation in rivers

[0136]

[0137] The removal rate of organic nutrients in rivers is calculated based on the simulated degradation, attenuation and ecological processes of DON and DOP in rivers. The mineralization rate factor reflects the mineralization removal capacity of nitrogen. In industrial and urban areas, due to severe water pollution, mineralization is more active, so the parameters are set higher; while in mountainous river sections with less pollution, mineralization is weaker. The reservoir interception factor represents the reservoir's ability to intercept nutrients.

[0138] Based on the simulated retention and deposition process of DON and DOP in the reservoir, the deposition rate of DON and DOP in the reservoir is calculated. In agricultural areas, reservoirs are usually used for irrigation, with long retention time and high interception factors; while in industrial areas, the reservoir capacity is relatively small and the interception factor is low. The artificial water withdrawal factor reflects the impact of changes in river water withdrawal on water volume. In agricultural areas and urban living areas, water withdrawal is more and the factor value is higher; while in mountainous river sections, water withdrawal is less. The flow rate attenuation factor represents the impact of flow rate on nutrient transport. Coastal cities and industrial areas have wider rivers and faster flow rates, so the factor value is higher; while in hilly and mountainous river sections, the flow rate is relatively slow. The distance attenuation factor from the estuary reflects the impact of the distance between the river and the estuary on nutrient transport. The farther the distance, the greater the reduction of nutrients and the lower the factor value; while the sections close to the estuary have less reduction and the higher the factor value. Temperature factor This factor takes into account the impact of water temperature on biological processes such as mineralization. The closer the temperature is to the optimum temperature, the stronger the mineralization, so the factor value is higher in areas with higher temperatures.

[0139] Based on the removal rate and deposition rate output by the model, combined with the structural characteristics of the watershed and river channel, the river discharge ratio of DON and DOP was calculated; the DON and DOP fluxes into the sea that ultimately entered the marine system were calculated using the removal rate of DON and DOP in rivers, the deposition rate in reservoirs, and their river discharge ratio.

[0140] ④ Use the Sobol sensitivity analysis method to evaluate the impact of each model parameter on the simulation results of nitrogen and phosphorus flux into the sea. Sobol analysis is a global sensitivity analysis method that determines high, medium and low sensitive parameters by calculating the Sobol index of each parameter.

[0141] The Monte Carlo simulation method was used to analyze the uncertainty of the model output. Through multiple random sampling, the mean and standard deviation of nitrogen and phosphorus fluxes into the sea were calculated to evaluate the uncertainty of the model prediction. The specific steps are as follows: 1) Input parameter distribution setting: According to the actual situation and reference data, the probability distribution of each input parameter is set. 2) Monte Carlo simulation: 1000 random samplings were performed to simulate the distribution of nitrogen and phosphorus fluxes into the sea. 3) Result analysis: The mean and standard deviation of the model output were calculated, and the frequency distribution histogram was drawn.

[0142] Analyze the correlation and consistency between simulated values ​​and monitored values. The residual is defined as the difference between the simulated value (Predicted Value) and the monitored value (Observed Value): Residual = Simulated Value − Observed Value. Plot the residuals into a scatter plot with the simulated value on the horizontal axis and the residual on the vertical axis. Calculate the mean and standard deviation of the residuals to evaluate the systematic bias and dispersion of the model. Analyze the distribution pattern of the residuals in the residual plot to evaluate the prediction accuracy of the model in different concentration ranges. Identify potential systematic biases, such as a significant deviation of the residual mean from zero, indicating that the model has systematic overestimation or underestimation under certain conditions.

[0143] Forward validation is to use the calibrated model parameters and input data to simulate the nitrogen and phosphorus concentrations at each hydrological station and compare the simulation results with the actual monitoring data. A 1:1 comparison chart is drawn, with the horizontal axis representing the actual monitoring value and the vertical axis representing the simulated value.

[0144] In the reverse validation, the nitrogen and phosphorus concentrations output by the model are reversely compared with the actual monitoring data to evaluate the performance of the model in the reverse simulation. A 1:1 comparison chart is also drawn, with the horizontal axis being the simulation value and the vertical axis being the monitoring value. The correlation and consistency in the reverse validation are analyzed. The root mean square error (RMSE) and coefficient of determination (R²) of the reverse validation are calculated and compared with the forward validation results to evaluate the stability of the model.

[0145] Calculate the root mean square error (RMSE) and coefficient of determination (R²):

[0146]

[0147]

[0148] ⑤ Refer to the nitrogen and phosphorus loss risk assessment system of Bechmann and Gburek, determine the spatial distribution characteristics of the entire study area based on statistical yearbooks and survey data, and determine the nitrogen and phosphorus index evaluation system in the Bohai Rim region. Affected by migration factors and source factors, the nitrogen and phosphorus nutrient transport risk installation status is divided into 5 levels, corresponding to excellent, good, medium, light pollution, and heavy pollution. In addition, each factor is given a corresponding weight value, and then the risk index of nitrogen and phosphorus loss in the five types of blocks in Table 3 is calculated according to the following formula, as follows: Figure 3 The specific formula is as follows:

[0149] ;

[0150] ;

[0151] ;

[0152] in, is the nitrogen transport risk factor; is the total nitrogen flux; W is the total available water resources in the study area; is the phosphorus transport risk factor; is the total phosphorus flux; is the weight coefficient of nitrogen transport risk; is the weight coefficient of phosphorus transport risk.

[0153] The risk index is divided into five levels: excellent (R<0.1), good (0.1≤R<0.2), moderate (0.2≤R<0.4), slightly polluted (0.4≤R<0.6) and severely polluted (R>0.6). All raw data have undergone strict quality control and preprocessing, including missing value filling, outlier detection and data standardization. Statistical software is used for regression analysis and risk index calculation, index change charts are drawn, and trend analysis and uncertainty assessment are performed.

[0154] The present invention also provides a system for evaluating the emission of dissolved organic nitrogen and phosphorus, which specifically comprises:

[0155] The data module is used to obtain different types of data of the characteristic area to build a database of the characteristic area; the different types of data specifically include socio-economic data, meteorological data, soil properties, DEM data, land use type, and parameters of dissolved organic nitrogen DON and dissolved organic phosphorus DOP;

[0156] The model module is used to modify the Global NEWS2 model based on the influencing parameters to obtain the integrated sub-basin scale nutrient transport model ISNSM; the influencing parameters specifically include soil transport attenuation coefficient, river transport attenuation coefficient and environmental factors;

[0157] The sub-basin division module is used to extract the river network and river flow direction data of the characteristic area based on the DEM data, perform sub-basin division on the ISNSM model, and obtain the sub-basin division results of the characteristic area; the sub-basin division results are numbered to form a complete basin topology structure;

[0158] The evaluation module is used to input socio-economic data, meteorological data, soil properties, land use, and parameters of DON and DOP into the ISNSM model, simulate the transport process of DON and DOP in the basin, and estimate the emission of organic nitrogen and phosphorus in each sub-basin.

[0159] Each module in the above-mentioned evaluation system for dissolved organic nitrogen and phosphorus emissions can be implemented in whole or in part by software, hardware, or a combination thereof. Each of the above-mentioned modules can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to each of the above modules.

[0160] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps in an embodiment of a method for evaluating the emission of dissolved organic nitrogen and phosphorus. The specific implementation method can be found in the method embodiment, which will not be described in detail here.

[0161] Furthermore, the present invention also provides a non-temporary computer-readable storage medium containing instructions, and a computer program is stored on the storage medium. For example, a memory containing instructions, the above instructions can be executed by a processor of a computer device to complete the above method. For example, a non-temporary computer-readable storage medium can be a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. When the computer program is executed by the processor, it can implement the steps in an embodiment of a method for evaluating the emission of dissolved organic nitrogen and phosphorus. The specific implementation method can be found in the method embodiment, which will not be repeated here.

[0162] It should be understood by those skilled in the art that embodiments of the present invention may provide methods, systems or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment or an embodiment combining software and hardware aspects. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0163] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as a combination of processes 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 a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0164] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0165] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0166] It should be pointed out that the specific implementation methods described above can enable those skilled in the art to understand the invention more comprehensively, but do not limit the invention in any way. Therefore, although the invention has been described in detail in this specification and embodiments, those skilled in the art should understand that the invention can still be modified or replaced by equivalents; and all technical solutions and improvements that do not deviate from the spirit and scope of the invention are included in the protection scope of the patent for the invention. Any figure mark in the claims should not be regarded as limiting the claims involved. Any simple change or equivalent replacement of the technical solution that can be obviously obtained by any technician familiar with the field within the technical scope disclosed in the present invention belongs to the protection scope of the present invention.

Claims

1. A method for evaluating the emission of dissolved organic nitrogen and phosphorus, characterized in that: The following steps are involved: Acquire different types of data of characteristic regions to construct a database of characteristic regions; the different types of data specifically include socio-economic data, meteorological data, soil properties, DEM data, land use type, and parameters of dissolved organic nitrogen DON and dissolved organic phosphorus DOP; The Global NEWS2 model is modified based on the influencing parameters to obtain the integrated sub-basin scale nutrient transport model ISNSM; the influencing parameters specifically include soil transport attenuation coefficient, river transport attenuation coefficient and environmental factors; Extract river network and river flow direction data of characteristic areas based on the DEM data, perform sub-basin division on the ISNSM model, and obtain sub-basin division results of the characteristic areas; number the sub-basin division results to form a complete basin topology structure; Socioeconomic data, meteorological data, soil properties, land use, and parameters of DON and DOP were input into the ISNSM model to simulate the transport of DON and DOP within the watershed and estimate the organic nitrogen and phosphorus emissions in each sub-watershed. The river transport attenuation coefficient is calculated by the following formula: Among them, F denit is the mineralization rate factor, F human Artificial water irrigation factor, F flow is the velocity attenuation factor, F temp is the temperature factor, F dist is the distance attenuation factor from the estuary; the soil transport attenuation coefficient is calculated by the following formula: Among them, f absor is the soil absorption factor; f rain is the rainfall penetration factor; f bio is the biotransformation factor; f chem is the chemical conversion factor; f dist is the attenuation factor of the distance from the river; the environmental factors, including agricultural sources, urban sources, rural domestic wastewater sources and natural sources, are calculated by the following formula: S DON / DOP =S agr +S urb +S vil +S nat , where S DON / DOP Indicates the total source of DON or DOP in the basin; S agr Indicates agricultural sources, including fertilizer application and animal manure; S urb Represents urban sources, including organic matter in urban runoff and discharge from sewage treatment plants; S vil Represents organic nitrogen and phosphorus in rural domestic wastewater discharge; S nat Indicates natural sources, including riverbank vegetation litter and natural decomposition of soil organic matter.

2. The method for evaluating the emission of dissolved organic nitrogen and phosphorus according to claim 1, characterized in that: The process parameter of the river transport attenuation coefficient is specifically calculated by the following formula: F dist =d·L; Among them, k denit is the mineralization rate constant, R cap is the reservoir retention factor, V water is the reservoir capacity, Q in is the inflow, DO is the dissolved oxygen concentration, τ is the hydraulic retention time of the reservoir, Q0 is the initial river runoff, Q t is the runoff at time t after artificial water withdrawal, F flow is the velocity attenuation factor, Width is the river width, Depth is the river depth, Q is the river flow, L is the distance from the river source to the river mouth, d is the distance attenuation coefficient, T is the water temperature, T opt is the optimum reaction temperature for mineralization, is the temperature sensitivity coefficient.

3. The method for evaluating the emission of dissolved organic nitrogen and phosphorus according to claim 1, characterized in that: The process parameter of the soil transport attenuation coefficient is specifically calculated by the following formula: f absor =a·clay%+b·OM%; f rain =1-e -r×Rainfall ; f chem =k chem ×(pH-7) 2 ; f dist =e -d·Distance·slope ; Wherein, clay is the clay content in the soil; OM is the organic matter content; a and b are empirical calibration coefficients, which are set according to the soil characteristics and experimental data of the specific area; Rainfall is the rainfall; r is the permeability coefficient; T is the soil temperature; Micro act is the soil microbial activity index; pH is the soil acidity and alkalinity; k chem is the chemical reaction coefficient; d is the distance attenuation coefficient; Distance is the distance between the research unit and the nearest river; slope is the slope.

4. The method for evaluating the emission of dissolved organic nitrogen and phosphorus according to claim 1, characterized in that: The agricultural sources, urban sources, rural domestic wastewater sources and natural sources are specifically calculated using the following formula: The calculation formula of agricultural source DON and DOP is: S agr =f fer ·A fer +f man ·N man +f res ·A res +f irr ·Q irr ; Among them, S agr Indicates the contribution of agricultural sources DON or DOP; f fer Indicates the organic nitrogen and phosphorus release coefficient in fertilizer application; A fer Indicates the area where fertilizer is used; f man Indicates the release coefficient of organic nitrogen and phosphorus in animal feces; N man Indicates the number of pigs, cattle, sheep and chickens raised in livestock; f res Indicates the release coefficient of organic nitrogen and phosphorus in crop residues; A res represents the area covered by crop residues; f irr represents the organic nitrogen and phosphorus release coefficient in irrigation water; Q irr Indicates the amount of irrigation water return; The calculation formulas for the urban source DON and DOP are: Among them, P represents the population of the city; GDP per is the GDP per capita; U is the urbanization rate; I is the urban industrial activity index; WWTD represents the level of urban wastewater treatment; S i They represent the standardized output ratios of different industries, and α and γ are calibration parameters; The calculation formulas for DON and DOP of rural domestic wastewater sources are: S vil =f vil ·P vil ·C vil ; Among them, S vil Indicates the source of DON or DOP in rural residents’ domestic wastewater; f vil P represents the organic nitrogen and phosphorus release coefficient in rural residents' domestic wastewater; vil represents the total population of rural residents in the domestic wastewater treatment area; C vil It represents the concentration of organic matter in wastewater from rural residents; The calculation formula of the natural source DON and DOP is: S nat =f dec ·A rip ·B bio +f soi ·A soi ; Among them, S nat represents the contribution of natural sources DON or DOP; f dec A represents the decomposition rate of litter on riparian vegetation; rep Indicates the coverage area of ​​riparian vegetation; B bio represents the biomass of vegetation; f soi Indicates the natural decomposition rate of organic nitrogen and phosphorus in the soil; A soi Represents the soil cover area.

5. The method for evaluating the emission of dissolved organic nitrogen and phosphorus according to claim 1, characterized in that: The ISNSM model calculates the amount of dissolved organic nitrogen and phosphorus emissions in each sub-basin through the following formula: in, is the load of dissolved organic nitrogen and phosphorus exported to the estuary from the ith sub-basin at time j; S urb It represents the load of nutrient E lost from urban areas to surface water bodies; (S agr +S vil +S nat ) represents the load of nutrient E from natural areas and rural areas to surface water bodies; TAC soil is the soil transport attenuation coefficient; TAC river is the river transport attenuation coefficient.

6. The method for evaluating the emission of dissolved organic nitrogen and phosphorus according to claim 1, characterized in that: The sub-basin division results are numbered, specifically, the sub-basins are uniquely identified by the Pfastetter coding method, and each sub-basin is numbered according to the confluence order, and is numbered step by step from the source to the estuary; the topological relationship between the sub-basins is constructed, and the upstream and downstream relationship between each sub-basin and its adjacent basin is determined to form a complete basin topological structure; the sub-basin number reflects its relative position in the entire basin; Among them, N k represents the number of sub-basin k; i represents the numbering sequence from the source to the estuary.

7. The method for evaluating the emission of dissolved organic nitrogen and phosphorus according to claim 1, characterized in that: It also includes calculating the final DON and DOP fluxes entering the ocean system after simulating the transport process of DON and DOP in the basin, specifically through the following steps: The model data of the target area was input into the ISNSM model to obtain the spatiotemporal distribution and migration paths of DON and DOP in different sub-basins; Simulate the degradation, attenuation and ecological processes of DON and DOP in rivers, and calculate the removal rate of organic nutrients in rivers; Simulate the retention and deposition process of DON and DOP in the reservoir and calculate their deposition rate in the reservoir; Based on the removal and deposition rates output by the model, combined with the structural characteristics of the watershed and river channel, the river discharge ratios of DON and DOP were calculated; The final flux of DON and DOP into the ocean system was calculated using the removal rate of DON and DOP in rivers, the deposition rate in reservoirs and the proportion of their river discharge.

8. A system for evaluating the emission of dissolved organic nitrogen and phosphorus, characterized in that: include: A data module is used to obtain different types of data of characteristic areas to build a database of characteristic areas; the different types of data specifically include socio-economic data, meteorological data, soil properties, DEM data, land use types, and parameters of dissolved organic nitrogen DON and dissolved organic phosphorus DOP; The model module is used to modify the Global NEWS2 model based on the influencing parameters to obtain the integrated sub-basin scale nutrient transport model ISNSM; the influencing parameters specifically include the soil transport attenuation coefficient, the river transport attenuation coefficient and the environmental factor; the river transport attenuation coefficient is calculated by the following formula: Medium, F denit is the mineralization rate factor, F human Artificial water irrigation factor, F low is the velocity attenuation factor, F temp is the temperature factor, F idst is the distance attenuation factor from the estuary; the soil transport attenuation coefficient is calculated by the following formula: f absor is the soil absorption factor; f rain is the rainfall penetration factor; f bio is the biotransformation factor; f chem is the chemical conversion factor; f dist is the attenuation factor of the distance from the river; the environmental factors, including agricultural sources, urban sources, rural domestic wastewater sources and natural sources, are calculated by the following formula: S DON / DOP =S agr +S urb +S vil +S nat , where S DON / DOP Indicates the total source of DON or DOP in the basin; S agr Indicates agricultural sources, including fertilizer application and animal manure; S urb Represents urban sources, including organic matter in urban runoff and discharge from sewage treatment plants; S vil Represents organic nitrogen and phosphorus in rural domestic wastewater discharge; S nat Indicates natural sources, including litter from riverbank vegetation and natural decomposition of soil organic matter; A sub-basin division module is used to extract the river network and river flow direction data of the characteristic area based on the DEM data, perform sub-basin division on the ISNSM model, and obtain the sub-basin division result of the characteristic area; number the sub-basin division result to form a complete basin topology structure; The evaluation module is used to input socio-economic data, meteorological data, soil properties, land use, and parameters of DON and DOP into the ISNSM model, simulate the transport process of DON and DOP in the basin, and estimate the emission of organic nitrogen and phosphorus in each sub-basin.

9. A computer device comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is loaded into a processor, the computer program can execute the steps of the method according to any one of claims 1 to 7.

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