The Studies On The Phosphorus Forms And Character Of Phosphorus Adsorption In The Sediment Of Five Big-lakes

Lake eutrophication is one of the most important environmental problems in our country, furthermore, the studies on phosphorus action in the interface of sediment-water is one of the key elements which helps find the mechanism of eutrophication. Among these, the studies on phosphorus forms and phosphorus adsorption of sediment are crucial aspects that can further reveal the mechanism of phosphorus action in the interface of sediment-water and supply direction and theoretical grounds to treatment and management of eutrophic shallow lakes in our country. This paper, distribution character of phosphorus forms in the sediment was analyzed, and isotherms for phosphorus sorption onto superficial sediments was studied under simulative condition.The TP content in sediment range from 217.8 to 3337.2mg/kg, and the TP content in urban lake sediment was generally higher than that in big or middle lake sediment for example Tai hu. The IP was the major phosphorus species. In terms of the range of phosphorus forms content, Fe/Al-P>OP>Ca-P, to the range of percent content, Fe/Al-P>Ca-P>OP. IP in the sediment from the channel is mainly of Fe/Al-P, and IP in the sediment from dredged lake is mainly of Ca-P.The TP content is mainly under the influence of Fe/Al-P and OP. With the increase of TP content, Fe/Al-P percent in IP had a increasing tend. OP in the sediment was significantly and positively correlated to Fe/Al-P and Ca-P, but Fe/Al-P and Ca-P had a little correlation. Grain size had relatively big effect on TP and Ca-P content in the sediments; TN, organic matter content have mainly effected OP and Fe/Al-P in the sediment; CEC have some effect on all of OP, Fe/Al-P and Ca-P; among the major element, SiO₂ have good negative correlation with OP and Ca-P, TFe₂O₃ have the best positive correlation with Fe/Al-P, OP, CaO have the best positive correlation with Ca-P.In the condition of high initial P concentration, isotherms for P sorption onto superficial sediments of shallow lake accord with the Langmuir isotherm as well as the Freundlich isotherm. Comparatively, geochemical characteristics of sediment and phosphorus forms affected mainly on value of K_L.There is the phosphorus desorption in the course of its adsorptions on sediment, and the high initial phosphorus concentration is the reason that the phosphorus desorption was concealed. The phosphate adsorption isotherms on sediments from lakes were fitted by linear model in low initial phosphorus concentration; The phosphate adsoiption-desorption equilibrium concentration on sediment from lake has well positive correlation with its amount of Org., CEC, TN, TP and its amount of different forms phosphorus, and with its amount of TP and its amount of different forms phosphorus the correlation is the best.The phosphorus adsorption was endothermic reaction, and temperature ascending was in favor of it in the sediment, but light contaminated one was more sensitive. The phosphorus adsorption in the sediment possessed particle concentration effect, it was more distinct in heavy contaminated sediment. The adsorption content at pH=6 is more than at ph=9. It shows that the sediments from heavy eutrophic lakes have the trend to release phosphate into the overlying water.