Nitrogen Footprint Management Of Lake Tai Watershed Based On Land Use

On the one hand,the frequent and intense human activities promote the rapid development of social economy,on the other hand,they also have adverse effects on the local and global environment.At present,the input of nitrogen into the global food production system is twice that of the safe planetary boundary,breaking the original balance of the ecosystem.In recent years,the problems of aquatic ecosystem in China are frequent:frequent occurrence of cyanobacteria,aggravation of red tide and decline of water quality,which seriously threaten the normal survival and reproduction of aquatic organisms in the basin and destroy the harmonious coexistence of the whole ecosystem.Nitrogen（N）,as one of the important factors affecting water eutrophication,is very important to improve the water quality of watershed.At the same time,as the carrier of nitrogen input and output,land use plays an important role in the analysis of nitrogen cycle.Therefore,coupling land use and nitrogen management to achieve watershed nitrogen footprint management based on land use is not only the key to reduce the excessive nitrogen in watershed,but also an important way to ensure the sustainable use of land resources and strengthen water pollution control.In this context,this study takes Lake Tai watershed as the research area,through literature review,data collection and quality balance method,based on Arc GIS software,analyzes the quantity and distribution changes of various land use types in Lake Tai watershed from 1995 to 2015;Based on the mass balance,the coupled human and natural system（CHANS）model was constructed to quantify the nitrogen cycle data of the study area from 1995 to 2015.It was found that the total nitrogen input increased from 141.1Gg in 1995 to 244.3Gg in 2010,and then decreased to201.2Gg in 2015.This shows that the treatment of water pollution in Lake Tai watershed has achieved initial results,and the further increase of nitrogen input has been controlled.At the same time,this study innovatively introduced the tool of nitrogen footprint into the calculation of basin scale,and found that the per capita nitrogen footprint of Lake Tai watershed was stable at 30 kg N yr^-1 from 1995 to 2005,and decreased to 25 kg and 20 kg N yr^-1 in 2010 and 2015,indicating that the nitrogen footprint was effectively controlled.In addition,the spatial intensity data of nitrogen footprint show that construction land has become a new hot spot in the calculation of nitrogen footprint in Lake Tai watershed from 1995 to 2015,and the main nitrogen emission source has changed from agricultural production on cultivated land to wastewater emission on construction land and nitrogen oxide emission from fossil fuel combustion.Therefore,in order to control the pollution in Lake Tai watershed,we should first optimize the land use structure and control the growth rate of construction land,so as to effectively control the total nitrogen emission of construction land,which is the hotspot of nitrogen footprint;Secondly,it is necessary to control all kinds of human activities on the construction land,especially to supervise the sewage discharge of the sewage treatment plant on the construction land,improve the sewage discharge standard,improve the sewage treatment equipment,prevent the sewage with high nitrogen content from being directly discharged into the river,and reduce the nitrogen content of the water body;On this basis,we should learn from the experience of other regions to optimize the industrial structure and control water pollution.