| In recent years,the accelerated industrialization and urbanization process has promoted the social and economic development.and the intensification of human activities has resulted in the decline of water quality.The fundamental measure to improve the quality of water environment is to control the total amount of pollutants,and the core of the total amount control is to distribute the total amount.In order to achieve the total pollutant control target,it is necessary to distribute the total pollutant control target fairly and reasonably,and allocate the total pollutant control target to each pollution source specifically.Therefore,it is of great significance to study a more equitable and reasonable distribution model for improving the water environment.This paper takes the middle reaches of Fenhe River as the research object,considers the development relationship between regional environment and economy,and reasonably determines the total amount control target.Based on the relevant research at home and abroad and the principles of fairness and feasibility,a total pollutant allocation system is constructed to allocate the total pollutant target.The main research contents and conclusions include:(1)Control unit division and water environment problem diagnosisAccording to the water quality requirement of Water Function Zoning of Shanxi Province,the water quality of the middle reaches of Fenhe River was evaluated.Based on the water environment function zoning,administrative zoning and catchment characteristics of the middle reaches of Fenhe River,the ArcGIS hydrological analysis function was used to divide the land and water control units of the main stream of Fenhe River and its main tributaries,Wenyu River and Xiao River.The results show that:1)the middle reaches of Fenhe River basin is divided into 7 land and water control units,including 5 main streams and 2 tributaries.2)The comprehensive pollution index of water quality in the middle reaches of Fenhe River decreased year by year from 2015 to 2019.but it still belongs to poor V water body.The water quality is mainly polluted by nitrogen and phosphorus,among which NH3-N is the primary pollutant.3)The total amount of COD and NH3-N in the middle reaches of Fenhe River basin in 2017 was 20850.25 t and 4466.46 t,respectively,which mainly came from the control unit of Taiyuan B section of Fenhe River.(2)Study on dynamic water environmental capacity in the middle reaches of Fenhe RiverIn this paper,COD and NH3-N were selected as calculation factors,the water quality of the middle reaches of Fenhe River was simulated by using one-dimensional hydrodynamic water quality coupling model,and the water environmental capacity of the middle reaches of Fenhe River in different water periods was calculated by using formula method.The results show that the water environmental capacity of COD in the middle reaches of Fenhe River basin is 65900.83 t/a,and the water environmental capacity of COD in high water season,normal water season and dry water season is 30172.11 t,24498.22 t and 11230.5 t,respectively.The water environment capacity of NH3-N is 3302.98 t/a,and the water environment capacity of high water season,normal water season and dry water season is 1506.25 t,1223.92 t and 572.81 t,respectively.(3)Study on the total pollutant allocation based on information entropy-Gini coefficient methodTaking the primary pollution factor NH3-N as the total volume control factor,on the basis of the relationship between water environmental capacity and the environmental and economic development of the river basin,and taking 2017 as the benchmark year,the control mode of total volume is selected,through the three-level distribution system of "basin-control unit-administrative region-pollution source",and based on the principle of fairness.A total pollutant allocation method based on information entropy-Gini coefficient method was established.The information entropy was used to correct the weights of each allocation index subjectively assigned.The secondary allocation of total pollutant targets under different combined weight schemes was considered,and the Gini coefficient method was used to evaluate the secondary allocation results.The results show that when population and GDP are the main influencing factors,the Gini coefficient of the distribution scheme is the smallest and the distribution scheme is the most fair and reasonable.On the basis of secondary allocation,considering the current situation of pollutant discharge,treatment capacity and pollutant discharge standard of pollutant discharging unit,a linear programming model was constructed,and genetic algorithm combined with particle swarm optimization algorithm was used to optimize the allocation of total pollutant target,and the total pollutant target was allocated to each pollution source. |
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