The Adsorption Characteristics and Impact Mechanism of Phosphorus by Surface Sediments in Natural Freshwater Lakes

A lake is a sink, source, and converter of phosphorus, and its ability to intercept phosphorus in water bodies is receiving increasing attention. In this study, the Nanyi Lake sediment in the middle and lower reaches of the Yangtze River basin was taken as the research object, and the phosphorus adsorption capacity and influencing factors of the sediment in the basin were investigated through a control variable experiment. The adsorption capacities of sediments at the sample points are L1 > L3 > L2, with maximum values of 372.41 mg/kg, 332.53 mg/kg, and 346.27 mg/kg, respectively. Equilibrium adsorption is reached at approximately 5 h for L1 and L2, and 10 h for L3. The interaction between sediment and phosphorus involves physical adsorption and mono-layer adsorption. The increase in temperature does not promote phosphorus migration from overlying water to sediments, but instead triggers phosphorus release from sediments, indicating an exothermic process for phosphorus adsorption on sediments. When the phosphorus concentration in overlying water is below and above 1 mg/L, increasing disturbance intensity results in enhanced phosphorus adsorption and release in sediments, respectively. The presence of humus in the overlying water, especially humic acid compared with fulvic acid, causes stronger adsorption of phosphorus on sediments. Overall, this study contributes to our understanding of phosphorus adsorption characteristics and mechanisms in Nanyi Lake sediments, providing valuable insights for managing and conserving this freshwater ecosystem.