水动力条件对湖泊水体磷素质量浓度的影响

The effect of water dynamical condition on phosphorus in lake

以环形水槽为研究手段,利用其可控的流速及可模拟的无限长,解决了前人未解决的湖泊水体水动力难以真实模拟的难题,模拟研究了不同流速对湖泊(太湖)水体中磷素质量浓度的影响。研究表明,随着水体流速的变化,湖泊水体中TP质量浓度的变化呈现3个阶段,即下降期、上升期和突增期。从物理化学和泥沙起动理论两方面,结合水流对悬浮物和沉积物的作用,分析了各阶段产生的原因。文章认为下降期的产生是因为在低流速下,一部分磷被悬浮物的絮凝沉淀带走所引起;上升期的产生则是因为流速上升扰动沉积物,使其达到少量动状态所引起;突增期的产生则是因为流速导致了沉积物普遍动而产生的。在研究范围内,溶解性磷质量浓度与水体流速有着明显的正相关关系;而在低流速下,溶解性磷是TP的主要组成成分,其质量浓度的相对比例可高达87%。结合太湖的有关研究,文章认为这是水华现象产生的关键原因。

By using the circular flume as the means of research, this essay exploits the controllable flow rate as well as analogueable infinite length to find the key to the tough problems of hydrodynamic in lake, which was not solved before and is hard to be actually simulated. It analogously studies the influence of varied flow rate on the phosphorus element in the water volume of the lake (Taihu Lake). The research shows that, as the water volume flow rate varies, there are three phases in the change of TP concentration of lake water volume, which are the falling phase, the rising phase and the sudden-rising phase respectively. Combining the function of water flow to suspended substance and precipitant substance from the angle of physical chemistry and silts starting theory, it analyzes the causes of every phase and assumes that the falling phase is caused by a portion of P being carried away by the deposit of suspended substance in the low flow rate; the rising phase is caused by the rising of flow rate disturbing the deposit and causing it to the dynamic stage; the sudden-rising phase is caused by flow rate causing the deposit to move generally. In the research scope, deliquescent P has the obvious positive relationship with the water volume flow rate, r =0.9612. In the low flow rate, it is the major composition of TP, its proportion being as high as 87%. In the terms of the related research on Taihu, it is assumed that it is the key reason of water bloom phenomena.