Study On Pollution Loads And Water Environmental Capacity In Macheng Section Of Jushui River

In order to further curb the pollution of water environment and restore the water environmental function of water body,it is of great theoretical and practical significance to study the pollution load and water environmental capacity of river inflow for the implementation of total pollutant control and river controller management.This paper takes Macheng Section of Jushui River as the research object,and collects the basic data of social economy,natural geography,hydrological water quality and pollution source in the watershed.In the ArcGIS environment,based on the digital elevation model(DEM)data,the automatic extraction method is used to extract the boundary of the watershed of Macheng Section of Jushui River,and on this basis,the control unit is divided.Secondly,using the water quality monitoring data from 2017 to 2018,the single-factor evaluation method was used to evaluate the water quality of Macheng Section of Jushui River.After that,combined with field investigation and data collection,the point source and non-point source pollution loads in the basin were calculated.Then,based on the two-dimensional water quality model of the river was used to calculate the simulated capacity of Macheng Section of Jushui River,and the ideal environmental capacity of Macheng Section of Jushui River was obtained.On the basis of the investigation and analysis of pollution sources,the maximum allowable emissions are determined after considering the non-point source pollutants entering the river and the point source pollutants entering the river.Finally,combined with the natural geography and social development of the basin,the specific targets and related countermeasures for the control of total water pollutant discharge in the basin are proposed.The main research results are as follows:(1)Through the analysis and evaluation of the current situation of the water quality of the main stream of Macheng Section of Jushui River in 2017-2018,concluded the annual water quality compliance rate of the main streams of Macheng Section of Jushui River is97.22% by 2017,and is 94.44% by 2018;Among the three conventional monitoring sections of the main stream of Macheng Section of Jushui River,the water quality of the monitoring section of Taochong Village can reach the Class II standard of Surface Water Environmental Quality Standard(GB3838-2002);the water quality of the Xujiawan section can be maintained at Class II~III,the water quality reached Class IV in May 2017;the water discharge section-Guoyu section can be stably maintained in Class III in 2017,and the water quality in Category V in January and February 2018,and the remaining months meet the standard.(2)Through the investigation and analysis of various pollution sources in the watershed of Macheng Section of Jushui River,it is determined that the total amount of chemical oxygen demand in the river basin in 2017 is 10389.1 tons,and the total amount of ammonia nitrogen into the river is 1415.53 tons.Most of the river basins are affected by point source pollution.From the perspective of the control unit,the Jushui city section control unit and the Yanjiahe control unit are concentrated sewage discharge areas,and their emissions account for nearly 50%.From the point of view of pollutants entering the river,chemical oxygen demand and ammonia nitrogen are mainly affected by urban life and livestock and poultry farming,and the discharge of pollutants accounts for more than80%.(3)The chemical oxygen demand and ammonia nitrogen were selected as the calculation factors of the water environment capacity of Macheng Section of Jushui River basin.Two-dimensional steady-state attenuation model was used to simulate the results.Considering the water environment capacity of the mixed area,the calculation resultsshowed:In 2017,the ideal water environment capacity of COD in Macheng Section of Jushui River was 18510.83 tons,the ideal water environment capacity of ammonia nitrogen was2144.83 tons,the actual water environment capacity of COD was 17409.89 tons,and the actual water environment capacity of ammonia nitrogen was 1972.6 tons.In 2017,the discharge of COD and ammonia nitrogen in Macheng Section of Jushui River can meet the requirements of total amount control.