上覆水磷浓度对沉积物孔隙水中磷垂向分布的影响

为探究上覆水磷浓度对沉积物孔隙水中磷垂向分布的影响,通过室内实验,利用薄膜扩散平衡技术(DET)对孔隙水中磷浓度进行测量,分析孔隙水磷浓度的垂向变化规律,并揭示平衡时上覆水磷浓度与孔隙水磷浓度以及上覆水-沉积物界面孔隙水磷浓度的关系。结果表明:上覆水磷浓度越高,则沉积物孔隙水中磷垂向分布达到平衡所需的时间越长,相同垂向位置处孔隙水磷浓度及其浓度梯度越大;孔隙水磷浓度及其浓度梯度随深度增加而降低,表层沉积物孔隙水中磷的扩散作用最强,下层沉积物孔隙水磷浓度受上覆水磷浓度变化影响较小;吸附平衡后,沉积物孔隙水磷浓度和上覆水-沉积物界面孔隙水磷浓度均与上覆水磷浓度呈幂函数关系,而留存在沉积物孔隙水中的磷浓度仅占2.26%～3.80%,上覆水中减少的磷大部分被沉积物吸附。

Effects of phosphorus concentration in overlying water on the vertical distribution of phosphorus in sediment pore water

In order to explore the influence of the phosphorus concentration in the overlying water on the vertical distribution of phosphorus in the pore water of the sediments, a series of laboratory experiments were conducted. The phosphorus concentration in the pore water was measured using the technique of diffusive equilibration in thin films (DET), based on which the vertical changes of the phosphorus concentration in the pore water were analyzed, and the relationship between the phosphorus concentration in the overlying water and the phosphorus content in the sediment pore water, as well as the phosphorus concentration in the pore water at the overlying water-sediment interface was investigated. It shows that the greater the phosphorus concentration in the overlying water, the longer it takes for the vertical distribution of phosphorus in the sediment pore water to reach equilibrium, and the greater the concentration of phosphorus in pore water and its concentration gradient at the same vertical position. The phosphorus concentration in pore water and its concentration gradient decrease with the increase of the depth. Phosphorus diffusion in the pore water of surface sediment is the strongest; however, the phosphorus concentration in the overlying water has no significant effect on phosphorus concentration in the pore water of the substratum sediment. After the adsorption reaches equilibrium, the phosphorus concentration in the sediment pore water and in the pore water at the overlying water-sediment interface have a power function relationship with that in the overlying water, and the remaining phosphorus in the sediment pore water only accounts for 2.26%-3.80%, because most of the phosphorus in the overlying water is adsorbed by the sediments.