流动水体中泥沙特性对磷分布的影响

发布时间：2018-03-19 03:19

本文选题：泥沙颗粒　切入点：泥沙吸附　出处：《重庆交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：泥沙是磷运动的主要载体,泥沙的运动对于磷的迁移和转化有着重要影响,这种影响主要表现为泥沙对磷的吸附和解吸过程。只有合理地考虑了泥沙对磷的吸附解吸效应,才能正确的判断磷运动的时空变化过程。由此,本文运用明渠和数值模拟手段,模拟研究自然河流的流动水体中泥沙与磷相互作用的动态过程及其基本特性。为了较好的模拟自然条件下河流的流动状态,本文采用循环流明渠模型,在使得泥沙随系统水体一起参与循环的基础上,分析并用泥沙吸附理论解释了不同泥沙粒径、泥沙浓度、水相磷初始浓度条件下泥沙对水体中磷的吸附过程并进行了Elovich方程及二级动力学方程的模拟。对比了现有摇瓶试验和明渠模型试验在试验结果和动力学方程模拟上的区别。本文的研究有以下结论:在悬移质泥沙与磷相互作用的过程中,随着溶解态磷浓度的减小,吸附至泥沙上的颗粒态磷的浓度逐渐增加,在初始阶段减小和增加的速率较大,随着时间的推移这个速率慢慢降低,最后悬移质泥沙与磷的相互作用达到一个动态平衡。粒径较小的泥沙颗粒的吸附能力比粒径较大的泥沙颗粒的吸附能力强。泥沙对磷的吸附容量均随着水体中含沙量的增大而增大。在水相磷初始浓度一定的条件下,随着含沙量的增大,单位质量的泥沙吸附磷的能力存在下降的趋势。虽然单位质量泥沙对磷的平衡吸附量随含沙量的增大而减小,但是泥沙对于磷吸附容量反而随着含沙量的增大而增大。这种特性对于研究水体中磷的自净作用和水体水环境的容量具有重大意义。在相同含沙量、不同磷初始浓度条件下,泥沙对磷的吸附容量均随着初始磷浓度的增大而增大。但随着初始磷浓度的增加,泥沙对磷的吸附量占初始磷的比例越来越低。结论表明,泥沙对磷的吸附有利于降低水体中水相磷的浓度,但水体中磷的浓度越高,水体中泥沙的这种作用越小。本文采用明渠试验,各组平衡时间均在2h左右。在模拟明渠模型中泥沙吸附磷动力学过程方面,虽然Elovich方程模拟出方程相关度都在0.9左右,但与实际曲线仍有较大差别,而二级动力学方程能够较好的模拟明渠模型中泥沙吸附磷动力学过程。相比而言,对与实际情况下的河流磷分布情况,二级动力学方程有更好的指导意义。
[Abstract]:Sediment is the main carrier of phosphorus movement, and its movement has an important effect on the transport and transformation of phosphorus, which is mainly manifested in the process of phosphorus adsorption and desorption. In order to correctly judge the temporal and spatial changes of phosphorus movement, the open channel and numerical simulation are used in this paper. The dynamic process and basic characteristics of the interaction between sediment and phosphorus in flowing water of natural rivers are simulated. In order to better simulate the flow state of rivers under natural conditions, the open channel model of circulating flow is adopted in this paper. On the basis of making the sediment participate in the circulation with the system water body together, the different sediment particle size and sediment concentration are analyzed and explained by the sediment adsorption theory. The adsorption process of phosphorus in water by sediment under the initial concentration of phosphorus in aqueous phase was simulated by Elovich equation and second order kinetic equation. The experimental results and kinetic equations of the existing shaking flask test and open channel model test were compared. The conclusions of this study are as follows: in the process of interaction between suspended sediment and phosphorus, With the decrease of dissolved phosphorus concentration, the concentration of particulate phosphorus adsorbed to sediment increases gradually, and decreases and increases rapidly in the initial stage, and decreases slowly with the passage of time. Finally, the interaction between suspended sediment and phosphorus reached a dynamic equilibrium. The adsorption capacity of small sediment particles was stronger than that of larger sediment particles. The amount of sediment increases with the increase of the initial concentration of phosphorus in the water phase. With the increase of sediment content, the capacity of phosphorus adsorption by sediment per unit mass decreases, although the equilibrium adsorption capacity of sediment per unit mass decreases with the increase of sediment content. However, the adsorption capacity of sediment for phosphorus increases with the increase of sediment content, which is of great significance to the study of the self-purification of phosphorus in water and the capacity of water environment. The adsorption capacity of sediment to phosphorus increases with the increase of initial phosphorus concentration, but with the increase of initial phosphorus concentration, the proportion of phosphorus adsorbed by sediment to initial phosphorus becomes lower and lower. The adsorption of phosphorus by sediment can reduce the concentration of phosphorus in water, but the higher the concentration of phosphorus in water, the less the effect of sediment in water. The equilibrium time of each group is about 2 hours. In simulating the kinetic process of phosphorus adsorption by sediment in the open channel model, although the correlation degree of the equation simulated by Elovich equation is about 0.9, it is still quite different from the actual curve. The second-order kinetic equation can simulate the process of phosphorus adsorption in open channel model, which is more instructive to the distribution of phosphorus in rivers.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X143;TV142

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