The Mian Source Of Nitrogen In Shahe Reservoir And Its Influence On Phytoplankton

Shahe Reservoir in Liyang City is a typical large artificial reservoir within hilly and mountain area of southeast china.It is the important water source of drinking water.In recent years,with the economic development,water of the reservoir gradually tends eutrophication,so it is urgent to protect the reservoir water quality.Nitrogen is the major contribution factor to shahe reservoir eutrophication and it is mainly provided by drainage basin.In order to further understand the influence of basin exploitation on the reservoir water quality,we study the nitrogen from the soil to the river and then to the reservoir.Based on these,we take a stereoscopic analysis for nitrogen sources and its influence on the phytoplankton community structure.Through the analysis of soil nitrogen in the land along Zhongtian River,we found that the main form of the soil nitrogen in this research zone was organic(99.14%),and nitrate was the main form of inorganic nitrogen.Besides,in view of the land use type,garden land and arable land were the main risk areas of nitrogen loss relative to the Woodland.Especially the tea garden,which was the biggest threat to the water environment.It most likely to become nitrogen source with runoff loss.According to the season fluctuation characteristics of the rainfall,we analyzed the spatial and temporal variation characteristics of nitrogen in river and reservoir.The results showed that the seasonal change of nitrogen in river and reservoir was closely related to human activities,especially the agricultural activities.Fertiliser use in agriculture was the main source of nitrogen in water.Under the action of rainfall erosion,soil nitrogen was transported into the river and became the main source of river.Nitrogen of upstream watershed enter the Shahe Reservoir by river transportation and migration,then greatly impacted the phytoplankton biomass and community of the reservoir.Correlation analysis between phytoplankton biomass and environmental factors including nitrogen nutrient showed that the climate condition was the most main factor to regulate phytoplankton biomass in Shahe Reservoir,and the driving function of nitrogen can not be ignored.Algae biomass was significantly positively related to nitrogen nutrient.Bacillariophyta biomass which was the highest in Shahe Reservoir was closely related to ammonium nitrogen.Large amount 'and unreasonable layout of watershed development were the main reason for the excess nitrogen nutrition.Cut nutrient levels from the source and control exogenous nitrogen input were fundamental to protect water quality.Implement pollution source reduction in a planned way,strictly control the ecological destruction and disturbance on the ground,control the fertilizer quantity and fertilization time in agriculture,were the important measures to improve water quality.So,the water quality protection of Shahe Reservoir cannot ignore the comprehensive control of nitrogen nutrient.it was impotant for regulating the phytoplankton community structure and maintaining the ecosystem stability.