River Water Quality Monitoring Section Optimization And Pollution Traceability

The rapid economic and social development has brought unprecedented pressure on the river water environment,and some rivers and lakes cannot meet the water quality management goals.To this end,strengthening water environment monitoring in the watershed can realize the perception of water environment status and provide basic support for water environment governance and management.In recent years,a lot of research has been carried out at home and abroad in establishing water environment monitoring networks and formulating water quality standards,including optimization of monitoring sections and total pollutant control.However,for most small and medium-sized watersheds,despite the serious pollution,they often only monitor the control section,which cannot fully capture the regional pollution situation,and it is difficult to achieve pollution traceability and assessment accountability.To this end,this study faces the actual needs of watershed water environment supervision,taking the Dengsha River Basin in Dalian as the research object,based on the existing national control and municipal control monitoring sections,the overall layout and optimization screening of the river basin monitoring sections,and then use the QUAL2 K water quality model to simulate the migration and transformation of ammonia nitrogen and total phosphorus pollutants.Based on the control section water quality objectives,the stepwise management and control standards of the upstream monitoring section under different water conditions are reversed.Finally,it analyzes the role of monitoring cross-section location and level-by-level control standards in actual pollution incident management and responsibility discrimination in the traceability of pollution sources,so as to provide scientific support for controlling cross-section water quality and water environment monitoring.The results achieved in this article are as follows:(1)Collected and compiled basic data,including the basic profile of Dengsha River Basin and hydrometeorological data.According to the norms and standards,multiple water quality monitoring sections were deployed in the Dengsha River Basin.Water samples were collected on site to obtain water quality parameters of each section.The overall water quality status of the basin was analyzed to determine the main over-standard factors as ammonia nitrogen and total phosphorus.(2)Based on the water quality data of all monitoring sections,systematic clustering method,fuzzy clustering method and matter-element analysis method were used to classify the monitoring sections,and then on the basis of classification,the sections were screened based on the land use type,production method and spatial distribution of each section,and finally selected 6 representative monitoring cross sections.The variance test and the mean test were performed on the samples before and after optimization,and the correlation between the data of adjacent sections before and after optimization was calculated.The results showed that the samples had uniform variance and no significant difference in mean,and the repeated layout of the sections was improved.(3)The QUAL2 K water quality model was determined based on the basic information of the Dengsha River and the water quality data rate of new sections and control sections.The source and contribution rate of pollutants in main monitoring sections were quantified,and the main polluted areas were clarified.Taking the water quality target of the control section as a guideline,priority was given to controlling key polluted areas,and water quality target management standards were formulated.The results show that for the newly optimized section,the control standard of the ammonia nitrogen index is lower in autumn,and the requirements are higher in spring and winter.The control standard of total phosphorus is close in spring,autumn and winter.(4)Based on all cross-section locations and control standards,taking the downstream control cross-section as an example,the possible pollution areas under different combinations of upstream monitoring sections with different water quality concentrations were analyzed,which provided a reference for the practical application of the research method in this paper.