[Phosphate adsorption characteristics onto the sediments from shallow lakes in the middle and lower reaches of the Yangtze River].

Adsorption isotherms and kinetics of phosphate onto the 11 sediments taken from shallow lakes in the middle and lower reaches of the Yangtze River were determined in laboratory, and the effect of physical and chemical properties of the sediments on its phosphate adsorption characteristics was also analyzed. The results indicate that: (1) The process of phosphate adsorption onto sediments mainly occurred within 0-10 h, the maximum adsorption rates occurred within 0-0.5 h, and then attends to a dynamic equilibrium; (2) Between the NAP and its organic matter, CEC, total phosphorus, inorganic phosphorus, organic phosphorus, Fe/Al-phosphorus and total nitrogen have remarkable positive correlation; between the maximum adsorption of phosphate and its CEC, inorganic phosphorus, organic matter and total phosphorus have remarkable negative correlation; between the total maximum adsorption of phosphate and its organic matter, CEC, total phosphorus, inorganic phosphorus, organic phosphorus, Fe/Al-phosphorus and total nitrogen have remarkable positive correlation; (3) As regards water quality of the shallow lakes in the middle and lower reaches of the Yangtze River at present, its sediment exists desorption. Between the adsorption-desorption equilibrium concentrations of phosphate onto the sediments and its organic matter, CEC, total nitrogen, the total phosphorus and the content of every form phosphorous have a remarkable positive correlation. Even the sediment from heavily polluted lake also has the tendency to release phosphate into the overlying water in this study.