Water quality assessment and pollutant reduction methods in high-latitude estuaries and bays

Abstract

The present invention relates to the field of marine environmental protection technology, and specifically discloses a method for water quality evaluation and pollutant reduction in high-latitude estuaries and bays, including: obtaining measured data of a study area; constructing a three-dimensional ecological hydrodynamic numerical model covering the study area, and calibrating and verifying the model; obtaining the spatiotemporal distribution characteristics of hydrodynamics and pollutants in the study area under current conditions in the past year; evaluating the water quality status of the study area after emission reduction using the WQI method, and analyzing the impact of pollutant reduction under different reduction schemes on changes in ecological parameters in the study area; and evaluating the ecological status in the study area after the implementation of different reduction schemes with reference to the actual situation in the study area; and selecting the most suitable pollutant reduction scheme based on the simulation results under different reduction schemes. The present invention overcomes the deficiency of traditional methods that ignore the impact of the freezing period, and can more accurately reflect the impact of the freezing period on water quality, ecological conditions, and pollutant diffusion.

Claims

1. A method for water quality assessment and pollutant reduction in high-latitude estuaries and bays, characterized by: The following steps are involved: S1. Model establishment and validation: Obtain measured data for the study area, including topographic data, hydrological data, and pollutant variables. The study area includes high-latitude estuaries and bays. Construct a three-dimensional ecological hydrodynamic numerical model covering the study area based on the measured data, and calibrate and validate the model using measured hydrodynamic and water quality variable concentration data. Obtain the spatiotemporal distribution characteristics of water dynamics and pollutants in the study area under current conditions in the past year; The water quality status in the study area was evaluated by the WQI method, and the ecological status of the study area under the current conditions was assessed; The three-dimensional ecological hydrodynamic numerical model includes three-dimensional continuity equations, momentum equations, turbulence equations, and pollutant convection, diffusion, migration and transformation equations; S2. Simulate pollutant reduction: Use the WQI method to evaluate the water quality status of the study area after emission reduction, and analyze the impact of pollutant reduction under different reduction schemes on the changes in ecological parameters in the study area. Based on the actual situation in the study area, evaluate the ecological status of the study area after the implementation of different reduction schemes; S3. Establish the best pollutant reduction plan: Based on the simulation results under different reduction plans, the water quality and ecological conditions of the study area are evaluated using the WQI method to select the best pollutant reduction plan; Obtain underwater terrain elevation information and construct a triangular grid for the study area and adjacent sea areas. Use irregular triangular grids in the horizontal direction and perform local densification at sewage outlets and river estuaries. Perform conventional terrain interpolation on the grids in the study area to obtain terrain information for the study area. The water body is stratified vertically using sigma coordinates, with 5-10 vertical stratification layers to capture the vertical flow velocity and water quality variation characteristics of the estuary. The steps to obtain the unique ice age conditions of high-latitude estuaries and bays are as follows: Based on ice cover data, obtain ice boundary range and ice thickness information, and complete the preparation of ice input files in the model; Based on triangular grids and vertical sigma grids, a three-dimensional ecological hydrodynamic numerical model of high-latitude sea areas was constructed. The glacial conditions unique to high-latitude estuaries and bays were incorporated into the three-dimensional ecological hydrodynamic numerical model, and the impact of ice cover conditions on water movement and pollutant migration and transformation in estuaries and bays was considered.

2. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 1, characterized in that: Also includes source data collection: Obtain relevant information of the study area, including hydrological information, topographic data, freezing period-related data, flow of rivers entering the sea, temperature and salinity and water quality variable data, discharge volume of nearby sewage outlets, water quality variable discharge concentration data, water temperature and salinity in different seasons of the sea area, and concentration data of water ecological variables, including phosphate, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, dissolved oxygen, BOD, and chlorophyll.

3. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 1, characterized in that: The time course curves of tide level process, temperature-salinity and water quality variables are given for the open sea boundary, and the time course curves of flow process, temperature-salinity and water quality variables are given for the river boundary.

4. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 1, characterized in that: During the model establishment, the operations for calibrating and verifying the parameters of the three-dimensional ecological hydrodynamic numerical model are as follows: The three-dimensional ecological hydrodynamic numerical model was verified based on the measured data of tidal levels, ocean currents and pollutant concentration changes in the study area. The specific operation was to verify the accuracy and reliability of the model by comparing the calculated values ​​and measured values ​​of tidal levels, velocities and flow directions, and concentrations of water quality variables during high and low tides. The relative error of tidal levels was less than 5%, the relative error of flow velocity was less than 10%, and the relative error of water quality variables was less than 30%. The model results met the accuracy requirements.

5. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 4, characterized in that: A plurality of water quality indicators are comprehensively selected and a unified current water quality evaluation is performed through a fixed WQI method calculation framework. The water quality indicators include temperature, dissolved oxygen, BOD, nutrients and chlorophyll.

6. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 5, characterized in that: In the simulated pollutant reduction, the design is made with reference to the ecological conditions under the current conditions of the study area, ensuring that the runoff of rivers into the sea remains unchanged while designing a plan to reduce the total amount of pollutants transported by rivers and discharged from sewage outlets; Referring to the runoff volume and ecological conditions of the rivers in the study area during the flood and dry seasons, while ensuring that the total amount of pollutants remains unchanged, a plan is designed to change the runoff volume into the sea and the concentration of pollutants discharged from the sewage outlet, and simulate the temporal and spatial distribution characteristics of water quality under different schemes.

7. The method for water quality assessment and pollutant reduction in high-latitude estuaries and bays according to claim 6, characterized in that: Combining the simulation results of different schemes with the WQI water quality assessment method, a comprehensive assessment of the water quality of estuaries and bays is conducted based on the results of different preset reduction schemes, and the assessment results are used to optimize the reduction schemes.

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