Abstract: The sediment samples from Wuhan to Chongming Island of Shanghai in the middle and lower reaches of the Yangtze River were collected for studying the characteristics of adsorption of Pb²⁺ by sediment via oscillatory adsorption test. The effects of sediment concentration, sediment particle size and organic matter content on Pb²⁺ adsorption were also analyzed. Results show that the adsorption of Pb²⁺on sediment reaches equilibrium after 20 hours. The adsorption kinetics can be analyzed and fitted by quasi-first-order kinetics, quasi-second-order kinetics and Elovich equation. The fitting coefficients are all above 0.85, and especially the fitting coefficient of quasi-second-order kinetics equation amounts to 0.997 8. The values of fitting correlation coefficient R² of Langmuir model for isothermal adsorption of Pb²⁺ are all above 0.9. The isothermal adsorption process of Pb²⁺ is monolayer adsorption mostly on the surface of sediment mainly in the manner of physical adsorption.With the increase of sediment concentration,the adsorption efficiency enhances significantly.When the sediment concentration increases to 1 g/L, the adsorption efficiency reaches the maximum (≈99.8%). The thermodynamic parameters ΔG < 0 and ΔH > 0 of sediment adsorption for Pb²⁺ reveals that the process can be carried out spontaneously. Temperature rising is conducive to instigating the adsorption of Pb²⁺. Organic matter content is in a significant positive correlation (R²=0.968 2, p<0.01) with adsorption energy. The amount of Pb²⁺ adsorbed by sediment increases with the decrease of sediment particle size. The adsorption of Pb²⁺ by sediments mainly occurs in particle size groups smaller than 0.074 mm. Monitoring on the sediment concentration, particle size distribution and its chemical composition in the middle and lower reaches of the Yangtze River should be strengthened so as to keep abreast of the influence of water and sediment changes on the migration and transformation of pollutants such as Pb²⁺.

Key words: sediment, Pb²⁺, adsorption, heavy metal, middle and lower reaches of the Yangtze River