Analysis Of The Influence Of Pollutant Input From The Upper Reaches Of The Yangtze River Estuary

This paper focuses on the impact of pollutants in the upper reaches of the Yangtze River Estuary on the environment of the Yangtze River Estuary,collects and analyzes the basic data of water quality in the Yangtze River Estuary.Based on the environmental quality standard of surface water(GB3838-2002),the single factor evaluation method is used to analyze the current situation and the change trend of the main pollutants in the upper reaches of the Yangtze River Estuary and the Yangtze River Estuary.Based on the analysis of the historical change trend of the main pollutant fluxes from the upper reaches of the Yangtze River Estuary,the influence of the change of the water quantity and quality of the upper reaches of the Yangtze River Estuary on the water environmental quality of the Yangtze River estuary is quantified by the numerical model.It provides a scientific basis for the ecological environment protection,comprehensive environmental management and scientific management of the Yangtze River Estuary,as well as for the preparation of the ecological environment protection plan of the Yangtze River Estuary.The main results are as follows:(1)Study on the current situation and the chang trend of the Yangtze River estuary environment over the years:① in 2018,the five monitoring sections in Xuliujing and the Yangtze River Estuary belong to class Ⅱ～Ⅲ water as a whole(total nitrogen does not participate in the assessment).According to the annual average concentration,the annual average concentration of ammonia nitrogen and total phosphorus in bamboo garden is the largest;the annual average concentration of total nitrogen in Qidong port is the highest,and the annual average concentration of permanganate index in south port is the largest.② From 2005 to 2018,five sections in Xuliujing and Yangtze River Estuary belong to class Ⅱ～Ⅲ water.The interannual change range of ammonia nitrogen is relatively large,showing a downward trend in 2013;the interannual change range of total phosphorus and total nitrogen is generally small,showing a downward trend in 2016;the interannual change range of permanganate index is relatively large,showing an upward trend after 2015.In most years,the average interannual concentrations of ammonia nitrogen,total nitrogen,total phosphorus and permanganate index in non flood season are generally higher than that in flood season.(2)Investigation and analysis of the pollutant fluxes from the upper reaches of the Yangtze River Estuary:① In the aspect of 2005 to 2018 monthly mean value,the seasonal variation of ammonia nitrogen,total nitrogen,total phosphorus and permanganate index is obvious,and the highest value of the flux appears in July(ammonia nitrogen is August)in flood season.From 2005 to 2018,the monthly average flux in flood season(from June to September)is larger than that in non flood season.② In terms of interannual change:before 2011,the range of interannual change of ammonia nitrogen was relatively large,and it remained stable as a whole from 2012 to 2018;the trend of interannual change of total nitrogen,total phosphorus and permanganate index was similar,and it remained stable as a whole before 2012,and it rose year by year from 2013 to 2016,and fell back from 2017 to 2018.(3)Analysis of the impact of the change of water quantity and quality in the upper reaches of the Yangtze River Estuary on the environmental quality of the Yangtze River Estuary:a mathematical model of hydrodynamic water quality in Hangzhou Bay of the Yangtze River estuary is established by using Mike21 model,and 16 calculation schemes are designed to analyze the impact of the change of water quantity and quality in the upper reaches of the Yangtze River Estuary on the environmental quality of the Yangtze River Estuary.① After the increase or decrease of water flow in the upper reaches of the Yangtze River,the water environment in the estuary of the Yangtze River will deteriorate or improve accordingly.The order of monthly average concentration change range is:South Channel>North Channel>North Port>North Branch.② After the water quality of the upper reaches of the Yangtze River is improved or deteriorated,the water environment of the Yangtze River estuary is improved or deteriorated accordingly.③ The correlation analysis of pollutant flux and water quality monthly average concentration category area of the Yangtze River into the sea shows that there is a good correlation between them.The pollutant input from the upper reaches of the Yangtze River estuary is an important factor affecting the water quality of the Yangtze River Estuary.The analysis and Study on the scope and extent of the impact of upstream pollutant input on the environmental quality of the Yangtze River Estuary can provide technical support for the scientific formulation of relevant policies on environmental protection of the Yangtze River Estuary.