High-latitude estuary and bay water quality evaluation and pollutant reduction method

Abstract

The invention relates to the technical field of marine environmental protection, and particularly discloses a high-latitude estuary and bay water quality evaluation and pollutant reduction method, which comprises the following steps: acquiring actual measurement data of a research area; constructing a three-dimensional ecological hydrodynamic numerical model covering the research area, and calibrating and verifying the model; obtaining spatial and temporal distribution characteristics of hydrodynamic force and pollutants of the research area in the past one year under the current condition; evaluating the water quality condition of the research area after emission reduction through a WQI method, and analyzing the influence of the reduction of pollutants on the change of ecological parameters of the research area under different reduction schemes; evaluating the ecological condition in the research area after different reduction schemes are implemented by referring to the actual condition of the research area; and selecting an optimal pollutant reduction scheme according to simulation results under different reduction schemes. The method overcomes the defect that the traditional method neglects the influence of the freezing period, and can more accurately reflect the influence of the freezing period on water quality, ecological conditions and pollutant diffusion.

Description

Technical Field

[0001] The present invention relates to the technical field of marine environmental protection, and particularly to a method for water quality assessment and pollutant reduction in high-latitude estuaries and bays. Background Art

[0002] With the intensification of global climate change, especially the warming of the climate in high-latitude regions, the estuarine and bay ecosystems are facing unprecedented pressures. The high-latitude estuary and bay areas are not only important providers of rich biological habitats and ecosystem services, but also play a crucial role in global climate regulation, material cycling and biodiversity conservation. However, due to factors such as pollution discharge and overdevelopment, the ecological environment in these areas is facing severe challenges, especially the ecological environment during the freezing period is more fragile and complex. Therefore, it is of great significance to propose an efficient and scientific method for offshore ecological environment assessment and pollutant reduction for ecological protection and environmental restoration in these areas.

[0003] The research on the ecological environment of high-latitude estuaries and bays mainly focuses on water quality monitoring and ecological status assessment, but most of the methods have not considered the special environmental factors during the freezing period. The freezing period has a significant impact on the physical and chemical properties of water bodies such as temperature, salinity, and oxygen concentration, thus directly affecting the survival of aquatic organisms and the self-purification ability of water bodies. In addition, the water body mobility during the freezing period weakens, and the exchange between the water body and the atmosphere is restricted, which poses great challenges to the diffusion and degradation processes of pollutants. Therefore, traditional assessment methods often ignore the special impact of the freezing period on the ecological environment, resulting in a deviation between the assessment results and the actual situation in practical applications.

[0004] With the advancement of industrialization, pollutant emissions have become one of the main causes of the deterioration of the ecological environment in estuaries and bays. Especially in high-latitude regions, the complexity of pollutant emissions and water quality pollution is more prominent. After a large amount of nitrogen and phosphorus pollutants, heavy metals, chemical pollutants, etc. enter the water body, through the physical and chemical changes of water flow, tides and freezing periods, it may form pollutant accumulations with long-term residues and potential hazards, and there are also transformations between pollutant variables. Therefore, based on the assessment of the ecological environment status of estuaries and bays, how to use a water environment model that comprehensively considers the migration and transformation of pollutants in the water body, propose reasonable reduction plans, and determine appropriate emission reduction measures has become a technical problem to be solved urgently. Most of the existing water pollution treatment methods focus on the identification and control of pollution sources, but there is still a lack of a comprehensive evaluation method with strong pertinence and high operability for effectively reducing the accumulation and diffusion of pollutants during the freezing period to ensure the continuous improvement of the ecological environment. The existing pollutant reduction plans are often relatively single, lacking a comprehensive evaluation mechanism, and failing to effectively combine multi-dimensional factors such as water quality improvement, ecological restoration, and emission reduction optimization. Therefore, there is an urgent need for a technical method that can scientifically evaluate the ecological environment quality of high-latitude estuaries and bays and can propose targeted pollutant reduction and ecological restoration plans. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for water quality evaluation and pollutant reduction in high-latitude estuaries and bays, which can accurately evaluate the health status of the ecological systems in estuaries and bays, identify the sources and fate trends of pollutants, and provide a scientific basis for formulating practical emission reduction measures and environmental protection strategies.

[0006] The purpose of the present invention can be achieved through the following technical solutions: A method for water quality evaluation and pollutant reduction in high-latitude estuaries and bays, comprising the following steps: S1. Model establishment and verification: Obtain the measured data of the study area, the measured data includes topographic data, hydrological data and pollutant variables, and the study area includes high-latitude estuaries and bays; construct a three-dimensional ecological hydrodynamic numerical model covering the study area according to the measured data, and calibrate and verify the model through the measured hydrodynamic and water quality variable concentration data; Obtain the spatio-temporal distribution characteristics of the hydrodynamic and pollutants in the study area under the current conditions in the past year; evaluate the water quality status in the study area through the WQI method, and evaluate the ecological status of the study area under the current conditions; The three-dimensional ecological hydrodynamic numerical model includes a three-dimensional continuity equation, a momentum equation, a turbulence equation, and equations for pollutant advection-diffusion, migration and transformation; S2. Simulated pollutant reduction: Evaluate the water quality status after emission reduction in the study area through the WQI method, and analyze the impact of pollutant reduction under different reduction scenarios on the changes in ecological parameters in the study area; and evaluate the ecological status in the study area after implementing different reduction scenarios with reference to the actual situation in the study area. S3. Determine the optimal pollutant reduction scenario: Based on the simulation results under different reduction scenarios, evaluate the water quality and ecological status of the study area through the WQI method, and select the most suitable pollutant reduction scenario.

[0007] As a further solution of the present invention: It also includes source data collection: Obtain relevant information of the study area, where the relevant information includes hydrological information, topographic data, data related to the freezing period, the flow of the rivers flowing into the sea, temperature, salinity and water quality variable data, the emissions of nearby sewage outfalls, water quality variable discharge concentration data, the water temperature and salinity of the sea area in different seasons, and the concentration data of water ecological variables, and the water ecological variables include phosphate, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, dissolved oxygen, BOD and chlorophyll.

[0008] As a further solution of the present invention: Obtain underwater topographic elevation information, and construct triangular grids for the study area and adjacent sea areas. Use irregular triangular grids in the horizontal direction and locally encrypt the sewage outfalls and the river estuary sections, and perform conventional topographic interpolation on the grids of the study area to obtain the topographic information of the study area.

[0009] As a further solution of the present invention: Stratify the water body in the vertical direction using sigma coordinates, with 5 - 10 vertical layers to facilitate capturing the velocity and water quality change characteristics in the estuary vertical direction.

[0010] As a further solution of the present invention: Given the tidal level process, time - history curves of temperature, salinity and water quality variables at the open boundary of the open sea, and given the flow process, time - history curves of temperature, salinity and water quality variables at the river boundary.

[0011] As a further solution of the present invention: The steps to obtain the ice - period conditions unique to high - latitude estuaries and bays are as follows: Based on the ice - cover data, obtain the ice - edge range and obtain the ice - thickness information, and complete the production of the ice input file in the model.

[0012] As a further solution of the present invention: Based on the triangular grid and vertical sigma grid, construct a three - dimensional ecological dynamics numerical model for the high - latitude sea area, add the ice - period conditions unique to high - latitude estuaries and bays to the three - dimensional ecological hydrodynamic numerical model, and consider the impact of ice - cover conditions on the water flow movement and pollutant migration and transformation in the estuary and bay.

[0013] As a further solution of the present invention: in the establishment of the model, the operations of calibrating and verifying the parameters of the three-dimensional ecological hydrodynamic numerical model are as follows: Verify the three-dimensional ecological dynamics numerical model based on the measured data of the tidal level, sea current and pollutant concentration changes in the research area. The specific operation is to compare the calculated values and measured values of the tidal level, velocity and flow direction, and water quality variable concentration during spring and neap tides to verify the accuracy and reliability of the model. Among them, the relative error of the tidal level is less than 5%, the relative error of the flow velocity is less than 10%, and the relative error of the water quality variable is less than 30%. The model results meet the accuracy requirements.

[0014] As a further solution of the present invention: comprehensively select multiple water quality indicators, and conduct a unified current water quality assessment through a fixed WQI method calculation framework. The water quality indicators include temperature, dissolved oxygen, BOD, nutrient salts and chlorophyll.

[0015] As a further solution of the present invention: in the simulation of pollutant reduction, design according to the ecological conditions in the research area under the current situation, and while ensuring that the river runoff into the sea remains unchanged, design a plan to reduce the total amount of pollutants transported by the river and discharged from the sewage outfall; Refer to the runoff and ecological conditions during the wet season and dry season of the rivers in the research area, and under the condition of ensuring that the total amount of pollutants remains unchanged, design a plan to change the runoff into the sea and the concentration of pollutants discharged from the sewage outfall, and simulate the temporal and spatial distribution characteristics of water quality under different plan conditions.

[0016] As a further solution of the present invention: combine the simulation results of different plans and the WQI water quality assessment method to comprehensively evaluate the water quality of the estuary and bay for the results of preset different reduction plans, and use the evaluation results to optimize the reduction plan.

[0017] Beneficial effects of the present invention: The present invention first incorporates the special environmental factors during the freezing period into the comprehensive evaluation of the ecological environment of high-latitude estuaries and bays, overcomes the deficiency of traditional methods that ignore the influence of the freezing period, and can more accurately reflect the influence of the freezing period on water quality, ecological conditions and pollutant diffusion, providing a more scientific basis for ecological protection in high-latitude regions. In addition, this method also comprehensively considers the migration and transformation of multiple pollutant variables, which is more in line with the characteristics of the actual sea area. The present invention adopts a multi-dimensional comprehensive evaluation method of hydrodynamic, water quality, pollution source control, etc., avoids the limitations of single-factor analysis, and can more comprehensively evaluate the health status of the ecological environment, ensuring the comprehensiveness and accuracy of the evaluation results. Moreover, the method of the present invention has strong practicability and operability, can provide practical technical support for the ecological restoration and protection of high-latitude estuaries and bays, and has a wide application prospect. Description of the Drawings

[0018] The present invention will be further described below with reference to the drawings.

[0019] Figure 1 It is a schematic diagram of the estuary modeling grid and terrain in an embodiment of the present invention; Figure 2 It is a tidal level verification diagram in an embodiment of the present invention; Figure 3 It is a site flow velocity verification diagram in an embodiment of the present invention; Figure 4 It is a site flow direction verification diagram in an embodiment of the present invention; Figure 5 It is a site water quality variable verification diagram in an embodiment of the present invention; Figure 6 It is an ice extent diagram for each period in an embodiment of the present invention; Figure 7 It is a distribution diagram of DIN concentration in the estuary area in an embodiment of the present invention; Figure 8 It is a distribution diagram of DIP concentration in the estuary area in an embodiment of the present invention. Detailed implementation manners

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0021] As Figures 1 - 8 shown, considering that the ecological environment of high-latitude estuaries and bays has significant seasonal variations, especially the profound impact of the freezing period on hydrological, climatic, and ecological processes. During the freezing period, the water body mobility weakens, and the diffusion and transformation ability of pollutants significantly weakens. These factors make the ecological environment of estuaries and bays more vulnerable during the freezing period. In addition, factors such as pollutant emissions and overdevelopment in the coastal zone also exert continuous pressure on water quality and ecological conditions, affecting the health of the marine ecosystem. Therefore, the present invention proposes a method for water quality assessment and pollutant reduction in high-latitude estuaries and bays, including the following steps: Step 1, Information collection step: Determine the high-latitude estuary or bay and its surrounding sea areas as the scope of modeling research, obtain the high-precision underwater topography of this area, and use the terrain elevation information to construct triangular meshes for the research area and adjacent sea areas, that is, locally encrypt the key areas of the research using irregular triangular meshes in the horizontal direction. On this basis, perform conventional terrain interpolation on the meshes of the research area to obtain the terrain information of the model calculation domain, and obtain information such as tidal levels, water currents, sea ice, and water quality concentrations at each monitoring station through on-site surveys and actual measurements, so as to be used for subsequent model verification and evaluation of the ecological status under the existing conditions of the research area.

[0022] Step 2, Model establishment step. According to the information in Step 1, based on unstructured triangular meshes, couple the three-dimensional ocean hydrodynamic model and the ecological hydrodynamic model to construct a three-dimensional offshore ecological hydrodynamic numerical model. The model discretizes the equations using the finite volume method of mass conservation.

[0023] Momentum equation:

[0024]

[0025] Continuity equation: ; Temperature equation: ; Salinity equation: ; Density equation: ; Among them, x, y, and z represent the eastward, northward, and vertical coordinates of the coordinate system respectively; u, v, and w are the velocity components in the x, y, and z directions; is the sea surface air pressure; is the hydrostatic pressure; q is the non-hydrostatic pressure; f is the Coriolis force parameter; g is the acceleration due to gravity; , , , respectively represent the horizontal kinetic energy, horizontal heat, and horizontal salinity diffusion terms; is the vertical kinetic energy diffusion term; is the vertical thermal eddy diffusion coefficient; is the vertical eddy viscosity coefficient; T, S, and ρ represent the temperature, salinity, and density of seawater respectively. The total pressure P = + + q, where .

[0026] The water quality equation is as follows: ; In the above formula, represents biogeochemical variables. Considering the transformation between variables, BF is the biogeochemical flux of elements obtained through calculation.

[0027] Step 3: Simulate the pollutant reduction step. Carry out the simulation work in combination with the numerical model in Step 2. First, calibrate and verify the three-dimensional ecological hydrodynamic mathematical model of the coastal area based on the measured tidal level, sea current data, and measured water quality parameters in the study area. The specific operation is to compare the calculated values and measured values of the tidal level, velocity, flow direction, and various water quality parameters during spring and neap tides to verify the accuracy and reliability of the model.

[0028] Step 4: After the model is verified to be reliable, simulate the water quality and ecological parameters under the current conditions of the study area. The results obtained from the simulation are used to evaluate the water quality variables in each season of the area using the WQI method.

[0029] WQI can integrate multiple water quality indicators. The specific formula is as follows: ; In the formula, n is the total number of water quality parameters; C i is the normalized value of variable i; P i is the relative weight of variable i, and its value range is 1 - 4. The range of WQI is between 0 and 100, and it is divided into 5 grades to represent the water quality status, namely: poor (0 ≤ WQI ≤ 25), fair (25 < WQI ≤ 50), medium (50 < WQI ≤ 70), good (70 < WQI ≤ 90), and excellent (WQI > 90).

[0030] Based on the WQI evaluation results and further ecological assessment, plan and design pollutant reduction schemes for different working conditions. It is best to reasonably protect and further optimize the water quality and ecological conditions in the study area. Evaluate the water quality parameters of the results under different working conditions using the WQI method, and analyze the WQI evaluation results and ecological status in detail, and conduct a detailed comparative analysis of each result.

[0031] Step 4: Establish the best reduction scheme step. According to the WQI evaluation results and ecological assessment of the simulated reduction schemes in Step 3, further analyze the water quality improvement effect and ecological restoration situation under each working condition. First, combine the simulation results to analyze each reduction scheme item by item, and evaluate its specific impact on water quality parameters, ecological status, and biodiversity. Through multi-dimensional comparison, screen out the emission reduction scheme that is most beneficial to water quality improvement and ecological restoration. At this time, a series of decision support tools, such as optimization algorithms and multi-objective evaluation models, will be introduced to comprehensively evaluate each scheme to ensure that while achieving water quality improvement, the ecological system function is maximally protected and restored.

[0032] Finally, the best pollutant reduction plan will be established based on the comprehensive evaluation results of each plan. The plan will formulate the best reduction strategy based on the water quality and ecological needs of the actual area, including reducing the main pollution sources, strengthening the treatment and reduction of pollutants, and improving the runoff to promote water exchange capacity. At the same time, it will also design flexible and adaptive reduction strategies based on different seasonal changes and ice period characteristics and the actual conditions of the study area to ensure that water quality can be effectively improved under different environmental conditions and promote sustainable protection and restoration of the ecosystem.

[0033] Example: The present invention has been applied in the Liaohe Estuary. The Liaohe Estuary is a typical high-latitude estuary area in China, with obvious seasonal changes in its hydrology and ecology. The climate in the area belongs to the temperate monsoon climate, with cold and long winters, and usually enters the freezing period between December and March of the following year. The freezing period has an important impact on the hydrology and ecosystem of the Liaohe Estuary. During the freezing period, the fluidity of the water body is weakened, the water exchange is restricted, the accumulation and diffusion of pollutants are inhibited, and the risk of water quality deterioration is increased.

[0034] Combined with the actual situation of Liaohe River Estuary, the present invention numerically simulates the hydrodynamics and water quality processes in the estuary area by constructing a three-dimensional offshore ecological hydrodynamic model. The whole work is carried out according to the following steps: Obtain data information on the Huanghai-Bohai coastline, determine the research calculation domain, and generate a triangular mesh in the calculation domain. Figure 1 The invention is locally encrypted in the river estuary and sewage outlet sea area, and the encrypted area is mainly the estuary area. Figure 1 Larger grids are used in areas far from the estuary input area, and smaller grids are used near the estuary. The grids are set in this way to more accurately simulate the changes in complex hydrological and water quality variables in the estuary input ocean area.

[0035] The underwater topographic information of Liaohe River estuary is obtained, and the interpolation is performed on the triangular meshes in the computational domain, and the topographic data is interpolated to the nodes of each triangular mesh.

[0036] The boundary conditions of the computational domain are determined. The open sea boundary is set at the Bohai Strait, and the river boundary is set at the upper reaches of the Liaohe River and the Daliaohe River.

[0037] The harmonic analysis method is used to obtain the tidal level duration process of this boundary as the open boundary of the open sea, and the runoff of the Liaohe River and the Daliaohe River needs to be given as the river boundary condition.

[0038] An ecological dynamic model of the Bohai Sea area is constructed. According to the characteristics of the Liaohe River estuary, water quality variables are selected. Generally, it is necessary to consider temperature, salinity, BOD, dissolved oxygen, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, active phosphate, silicate and chlorophyll a, and determine the conversion parameters of each water quality variable.

[0039] Obtain hydrological data such as tidal levels, flow directions, and flow velocities at certain points in the Liaohe Estuary for hydrodynamic model verification and calibration; obtain water quality parameters at certain points, such as concentrations of temperature, salinity, dissolved oxygen, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, reactive phosphate, silicate, chlorophyll a, etc., for boundary condition calibration and simulation result verification.

[0040] Production of ice period files. Figure 2 Ice extent maps for each period of the ice period are given (from left to right are the first ten days of December 2023, the first ten days of January 2024, and the last ten days of January 2024). Since part of the Liaodong Bay is covered during the freezing period, the model calculation domain including the freezing period is the entire Bohai Sea area.

[0041] Download the biogeochemical reanalysis dataset containing the open boundary range of the entire study area from the Copernicus Marine Data Service Center, extract the water quality parameter data we need, and make the above open boundary point coordinates and water quality parameter data at each point into a water quality open boundary input file; the water quality boundary of the river is made into a water quality open boundary input file through measured data; data such as solar radiation, air temperature, and wind field are provided by the ERA5 global reanalysis dataset.

[0042] Set the simulation period, conduct hydrodynamic numerical simulation in the waters near the project, complete the calculation of variables such as water level, flow velocity, and flow direction of the tidal current field, and compare the simulated tidal level, flow velocity, and flow direction with the measured data for a period of time. Specifically, as Figure 3 and Figure 4 shown, the high and low tidal levels and the process lines of the calculated and measured tidal level processes are in good agreement, verifying the accuracy.

[0043] Output the flow field vector within the entire calculation domain. If the flow field changes uniformly without sudden changes, it indicates that the tidal wave movement in the study area simulated by the mathematical model is basically similar to the natural tidal wave movement, the boundary control conditions adopted by the mathematical model are appropriate, and the simulated results of the tidal level meet the calculation accuracy requirements. Otherwise, change the boundary conditions and repeat the simulation process.

[0044] Simulate the water quality status in the study area under the current conditions, verify each water quality variable in the simulation, and the verification figure is shown in Figure 5 , and the verification accuracy requirement is that the relative error is not less than 30%, and the accuracy meets the requirements.

[0045] Output the concentration distribution maps of the main pollutants DIN and DIP in the study area ( Figure 6 and Figure 7 ), analyze the simulation rationality. If it is reasonable, conduct a WQI evaluation on the results to obtain the water quality results of different seasons in the Liaohe Estuary sea area.

[0046] Combined with the characteristics of the water environment in the Liaohe Estuary, six key water quality indicators were selected: dissolved oxygen, temperature, chlorophyll a, five-day biochemical oxygen demand, inorganic phosphorus, and inorganic nitrogen, as evaluation factors to calculate the WQI. These water quality indicators can comprehensively reflect the water quality status and its ecological health level of this sea area. Among them, the inorganic nitrogen concentration is calculated as the sum of ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen in the model. The corresponding limit values and weights for each water quality indicator are shown in the following table:

[0047] Emission reduction plans with a 10%, 20%, and 30% reduction in pollutant discharge concentrations in the upstream river were designed respectively, the distribution of the main pollutants simulated by each plan was given, and the WQI water quality evaluation was carried out on the simulation results of different plans to obtain the water quality evaluation results of different seasons in the Liaohe Estuary sea area.

[0048] Emission reduction plans with a 10%, 20%, and 30% reduction in pollutant concentrations at the sewage outfall were designed respectively, the distribution of the main pollutants simulated by each plan was given, and the WQI water quality evaluation was carried out on the simulation results of different plans to obtain the water quality evaluation results of different seasons in the Liaohe Estuary sea area.

[0049] Design plans with a 10% and 20% reduction in the upstream river flow and a 10% and 20% increase in the flow were designed respectively, the distribution maps of the main pollutants simulated by each plan were given, and the WQI water quality evaluation was carried out on the simulation results of different plans to obtain the water quality evaluation results of different seasons in the Liaohe Estuary sea area.

[0050] Design plans with a 10% and 20% reduction in the discharge flow at the sewage outfall were designed respectively, the distribution maps of the main pollutants simulated by each plan were given, and the WQI water quality evaluation was carried out on the simulation results of different plans to obtain the water quality evaluation results of different seasons in the Liaohe Estuary sea area.

[0051] Analyze the WQI water quality evaluation results, and determine the best pollutant reduction plan with the goal of water quality improvement.

[0052] The above has described an embodiment of the present invention in detail, but the content described is only a preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the present invention application should still fall within the patent coverage scope of the present invention.

Claims

1. A method for water quality assessment and pollutant reduction in high-latitude estuaries and bays, characterized in that Including the following steps: S1. Model establishment and verification: Obtain the measured data of the study area, where the measured data includes topographic data, hydrological information, and pollutant variables, and the study area includes high-latitude estuaries and bays; construct a three-dimensional ecological hydrodynamic numerical model covering the study area according to the measured data, and calibrate and verify the model through the measured hydrodynamic and water quality variable concentration data; Obtain the spatio-temporal distribution characteristics of the hydrodynamic forces and pollutants in the study area under the current conditions in the past year; Evaluate the water quality status in the study area by the WQI method and evaluate the ecological status of the study area under the current conditions; The three-dimensional ecological hydrodynamic numerical model includes a three-dimensional continuity equation, a momentum equation, a turbulence equation, and equations for pollutant advection-diffusion, migration, and transformation; S2. Simulate pollutant reduction: Evaluate the water quality status in the study area after emission reduction by the WQI method, and analyze the impact of the reduction of pollutants under different reduction scenarios on the changes in ecological parameters in the study area; and refer to the actual situation of the study area to evaluate the ecological status in the study area after the implementation of different reduction scenarios; S3. Determine the optimal pollutant reduction scenario: Based on the simulation results under different reduction scenarios, evaluate the water quality and ecological status in the study area by the WQI method and select the most suitable pollutant reduction scenario.

2. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 1, characterized in that, It also includes source data collection: Obtain the relevant information of the study area, where the relevant information includes hydrological information, topographic data, data related to the ice period, the flow of the rivers flowing into the sea, temperature, salinity, and water quality variable data, the emissions of the nearby sewage outfalls, the emission concentration data of water quality variables, the water temperature and salinity in different seasons of the sea area, and the concentration data of water ecological variables, and the water ecological variables include phosphate, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, dissolved oxygen, BOD, and chlorophyll.

3. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 2, wherein Obtain the underwater topographic elevation information, and construct a triangular grid of the study area and its adjacent sea area. Use an irregular triangular grid in the horizontal direction and locally encrypt the sewage outfalls and the river estuary sections, and perform conventional topographic interpolation on the grid of the study area to obtain the topographic information of the study area.

4. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 3, characterized in that, Use the sigma coordinate to stratify the water body in the vertical direction, with 5-10 vertical layers to facilitate capturing the velocity and water quality change characteristics in the estuary vertical direction.

5. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 4, characterized in that, Given the tidal level process, the time history curves of temperature, salinity, and water quality variables at the open boundary of the open sea, and given the flow process, the time history curves of temperature, salinity, and water quality variables at the river boundary.

6. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 5, wherein The steps to obtain the ice period conditions unique to high-latitude estuaries and bays are as follows: Based on the ice cover data, obtain the ice boundary range and obtain the ice thickness information, and complete the production of the ice input file in the model.

7. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 6, characterized in that, Based on the triangular grid and the vertical sigma grid, construct a three-dimensional ecological dynamics numerical model of the high-latitude sea area, and add the ice period conditions unique to high-latitude estuaries and bays to the three-dimensional ecological hydrodynamic numerical model, considering the impact of the ice cover conditions on the water flow movement and pollutant migration and transformation in the estuaries and bays.

8. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 7, characterized in that, In the model establishment, the operations of calibrating and verifying the parameters of the three-dimensional ecological hydrodynamic numerical model are as follows: The three-dimensional ecological dynamics numerical model is verified based on the measured data of the tidal level, sea current and pollutant concentration changes in the study area. The specific operation is to compare the calculated values and measured values of the tidal level, velocity and flow direction, and water quality variable concentration during the spring and neap tides to verify the accuracy and reliability of the model. Among them, the relative error of the tidal level is less than 5%, the relative error of the flow velocity is less than 10%, and the relative error of the water quality variable is less than 30%. The model results meet the accuracy requirements.

9. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 8, characterized in that, Multiple water quality indicators are comprehensively selected, and a unified current water quality assessment is carried out through a fixed WQI method calculation framework. The water quality indicators include temperature, dissolved oxygen, BOD, nutrients and chlorophyll.

10. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 9, characterized in that, In the simulation of pollutant reduction, it is designed with reference to the ecological status under the current conditions of the study area. While ensuring that the river runoff into the sea remains unchanged, a plan is designed to reduce the total amount of pollutants transported by the river and discharged from the sewage outfall. With reference to the runoff and ecological status of the study area's rivers during the wet season and dry season, under the condition of ensuring that the total amount of pollutants remains unchanged, a plan is designed to change the runoff into the sea and the pollutant concentration discharged from the sewage outfall, and the spatio-temporal distribution characteristics of water quality under different plan conditions are simulated.

11. The method for evaluating water quality and reducing pollutants in high-latitude estuaries and bays according to claim 10, wherein Combining the simulation results of different plans and the WQI water quality assessment method, a comprehensive assessment of the water quality of the estuary and bay is carried out for the results of different preset reduction plans, and the assessment results are used to optimize the reduction plan.

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