Analysis of Phosphorus Import CharacteristicofThe Upstream Input Rivers of Three Gorges Reservoir

摘要

Surface water samples were collected from Yangtze River mainstream,Jialing River and Wu River in October 2014 and January 2015.The phosphorus fractions in water and suspended particulate were analyzed to examine the spatial-temporal distribution of phosphorus in three upstream input rivers of Three Gorges Reservoir (TGR) and investigate their import impacts on TGR water environment.The results showed that the concentrations of phosphorus fractions in water of Yangtze River mainstream and Wu River were higher than that of Jialing River.The particle sediment input from Jinsha River was the major impact factor of phosphorus distribution in Yangtze River mainstream,while phosphorus mine exploitation in the upstream greatly affected phosphorus distribution in Wu River.In October 2014,the impounding stage of TGR,total particulate phosphorus (TPP) accounted more than 50％ of total phosphotus (TP)in water of three upstream rivers of TGR,extractable organic phosphorus (Exo-P) and detrial phosphotus (Det-P) were the predominant phosphorus fraction in suspended particulate,and bioavailable phosphorus accounted more than 50％ of particulate phosphorus.Due to the unstable water environment of TGR affected by the anti-season artificial regulation,phosphorus in particle matter were likely to be released,which may influence reservoir water quality in some ways.In January,the high water level stage of TGR,less rainfall and river nmoff in three upstream input rivers of TGR than that in October highlighted the influence of point source input such as industry effulents,agricultural wastewater and domestic sewage,so the predominant phosphorus fraction in water turned to be TDP,accounting for more than 60％ of TP.With the affects of reservoir backwater during high water level stage of TGR,the renewal period of water quality in the tributaries of Yangtze River were extended,and thus plenty of phosphotus were accumulated and water eutrophication were increased in the tributaries of TGR.Based on data of Zhutuo,Beibei,Wulong hydrological stations,the estimated annual total phosphorus flux of three upstream input rivers was 44290.27 t/a,accounting for 83.41％ of total phosphorus flux imported into TGR.