黄河兰州段消落带表层沉积物对磷的吸附

为探究黄河消落带表层沉积物对磷的吸附特征，基于吸附动力学、吸附热力学及单因子实验，现场采集黄河 (兰州段) 消落带表层沉积物进行实验室模拟研究。结果表明：沉积物对磷的吸附动力学经历快速吸附、慢速吸附、吸附平衡3个阶段，扰动条件下，在10 min内吸附量达到最大吸附量的85%以上，480 min达到吸附平衡；沉积物对磷的吸附符合Langmuir吸附等温方程，随着温度的升高最大理论吸附量Q_m随之增加，25 ℃时Q_m达到119.831 mg·kg⁻¹；单因子实验中，扰动频率增加对磷的吸附量具有明显的促进作用；pH为7~8时沉积物吸附效果最佳，偏酸性条件次之，偏碱性条件下吸附效果较差；增大上覆水KH₂PO₄浓度，吸附量增加，吸附率整体呈下降趋势。由此可知，黄河消落带表层沉积物对磷元素具有一定的拦截效应，河水的扰动能够促进沉积物对PO₄^3--P的吸附，但是水体的pH值变化及高浓度陆源污染物均会削弱消落带对磷元素的吸附拦截作用。该研究结果可为黄河上游的水污染防治及消落带的生态管理提供研究依据。

Adsorption characteristics of phosphorus by surface sediments in the fluctuation zone of the Lanzhou section of the Yellow River

In order to explore the adsorption characteristics of phosphorus by surface sediments in the fluctuation zone of the Yellow River, based on adsorption kinetics, adsorption thermodynamics and single-factor experiments, the surface sediments of the Yellow River (Lanzhou section) in the fluctuation zone were collected on site for laboratory simulation study. The results showed that the adsorption kinetics of phosphorus onto the sediments contained 3 stages: rapid adsorption, slow adsorption and adsorption equilibrium, and under the disturbance conditions, the adsorption capacity could reach higher than 85% of the maximum adsorption capacity within 10 min, and arrived adsorption equilibrium in 480 min. The adsorption of phosphorus by the sediments conformed to the Langmuir adsorption isothermal equation, and the maximum theoretical adsorption capacity Qm increased with the increase of temperature, and Qm reached 119.831 mg·kg−1 at 25 °C. In the single-factor experiment, the increase of disturbance frequency had a significant promoting effect on the adsorption capacity of phosphorus. When the pH was 7~8, the adsorption effect of the sediments was the best, followed by acidic conditions, and the adsorption effect was poor under alkaline conditions. When the concentration of KH2PO4 in the overlying water increased, the adsorption capacity increased, and the adsorption rate showed a downward trend as a whole. Thus, the surface sediments in the fluctuation zone of the Yellow River had a certain interception effect on phosphorus, and the disturbance of river water could promote the adsorption of PO43--P by the sediments, but the pH change of water and the high concentration of land-based pollutants could weaken the adsorption and interception of phosphorus in the fluctuation zone. The results of this study can provide a research basis for the prevention and control of water pollution in the upper reaches of the Yellow River and the ecological management of the fluctuation zone.