Characterization Of Nitrogen Nutrient Changes In The Reservoir Water Front Zone And Surrounding Catchment Area Of Mi Yun Reservoir

Miyun Reservoir is the most important drinking water source in Beijing,which has been listed in the national important water source list.In recent years,the total nitrogen concentration in Miyun Reservoir has shown a fluctuating upward trend.High concentration of total nitrogen is easy to cause eutrophication and other water pollution phenomena.It increases the pollution degree of the reservoir and reduces the water quality of the reservoir,which poses a serious threat to the water safety of the people in the capital.In this thesis,the characteristics of nitrogen elements in Miyun Reservoir riparian zone and its surrounding catchment area were studied by soil and sediment sampling and indoor simulation experiments.The traceable analysis of nitrogen elements in the reservoir riparian zone and its surrounding catchment area was carried out by using nitrogen and oxygen isotope techniques,to provide support to miyun reservoir protection and management work,To achieve targeted governance and promote sustainable use of water resources.The main conclusions are as follows :(1)The results of physical and chemical properties analysis of soil and sediment showed that the soil bulk density increased,total porosity and field water capacity decreased due to the change of water level.The contents of soil organic matter and total nitrogen were affected by vegetation cover,and the contents of soil organic matter and total nitrogen increased by vegetation cover.The sediment along the shore was submerged,and the content of organic carbon and total nitrogen increased,while the content of nitrate nitrogen decreased.(2)The indoor soil immersion simulation experiment for 30 days showed that the concentration of total nitrogen and nitrate nitrogen in overlying water had a decreasing trend,while the concentration of ammonia nitrogen had a rising trend.The change of nitrate nitrogen concentration was the main factor affecting the total nitrogen content in overlying water.The results showed that during the period of inundation,the soil had adsorption effect on total nitrogen and nitrate nitrogen,and ammonium nitrogen was the release effect.(3)Hydrochemistry and isotope tracer analysis of rainfall runoff in the Kubin belt and surrounding catchment areas were carried out.The results showed that the water quality of runoff was seriously polluted,and total nitrogen was the primary factor affecting water quality.Nitrogen pollution sources in the region mainly come from ammonia fertilizer,soil nitrogen and domestic sewage,and the contribution rates of pollution sources are 41.70 %,33.09 % and 15.64 %,respectively.Different rainfalls have a certain impact on the contribution of pollution sources,and the contribution of ammonia fertilizer is the most affected by rainfall.