Phosphorus Fractions And Its Release Characteristics Of Sediments In Sanjiu Lakes Of Yixing,Western Taihu Lake

Phosphorus is the first controlling factor for lake algae to synthesize their own cells,sediment phosphorus is the endogenous host of lake eutrophication.Yixing,on the west bank of Taihu Lake,was affected by its own development,with serious pollution of urban water and water quality deterioration in Taihu Lake.It is very important to study the status of phosphorus pollution in sediments of Sanjiu Lakes of Yixing,which is of great significance for controlling the eutrophication process and improving the water quality of Taihu Lake.In this paper,columnar and surface sediments in Sanjiu lakes of Yixing was taken as research object.Physical and chemical indicators were determined and analyzed.Phosphorus speciation distribution,and bioavailability of phosphorus in surface sediments were also analyzed by Chemical fraction extraction method.Furthermore,using laboratory simulated disturbance release experiments to explore the release characteristics of phosphorus in surface sediments.The main research results are as follows:(1)Sediments are generally alkaline areas,Tuanjiu TOC was the highest,and nitrogen pollution was also the most serious.The overlying water pH was greater than 7,ORP greater than 0,the performance of alkaline and oxidizability.The overlying water TP ranged 0.200~0.792 mg/L,Grade IV water quality,TN ranged from 2.93~5.58 mg/L,belonging to over ? water quality.(2)The contents of TP in columnar sediments were as follows:Xijiu(289.18~696.10mg/kg)<Tuanjiu(289.18~1007.79mg/kg)<Dongjiu(935.51~1246.00mg/kg).Phosphorus content of all forms decreased significantly with increasing depth,but the decreasing trend of Dongzhu was gentle.The relative content of phosphorus in surface sediments showed Fe-P>Ca-P>Al-P>Org-P>Ex-P>O-P,Ca-P increased with depth more than Fe-P as main ingredient,while there is no significant change in Dongjiu.Al-P,Fe-P were positively correlated with TP and Ex-P,Org-P had a significant positive correlation with TOC.(3)The contents of TP in the surface sediments of Xijiu,Dongjiu and Tuanjiu were 659.04~825.22,514.72~1196.94 and 934.55~205.69 mg/kg,belonging to the category of light and moderate pollution.Fe-P was the highest content of phosphorus in all forms,and Tuanjiu Org-P content is highest.Generalized bioavailability of phosphorus account for 48.01%~82.07%,active Fe/Al-P 44.74%~79.38%,and there is a very high risk of phosphorus release.Fe-P is the main source of interstitial water P,and Ca-P is the main form of phosphorus that causes the overlying water TP to change.(4)Simulation experiment of phosphorus release,the release of DTP and SRP in Dongjiu was the highest,and the balance time is also late.In the process of reabsorption,the adsorption capacity of Tuanjiu to phosphorus was the strongest,while that of Dongjiu was the weakest.DTP and SRP were highly fitted to the release kinetics and reabsorption kinetics models,while DOP was the opposite.DTP and SRP had the maximum release potential at a water/soil ratio of 200,and DOP at a ratio of 25.