【作者】 蔡晔；

【导师】 刘德启；

【作者基本信息】 苏州大学 ， 分析化学， 2007， 硕士

【摘要】 随着城市化的快速发展，河流的自然结构也随之被改变，而河流污染也导致了自净功能的下降。因此，河流的生态恢复已是当务之急。探讨不同河型，尤其是平原地区河道结构与水体自净能力、环境容量及营养循环之间的关系，对城市生态河网建设、恢复河流生态结构与功能具有重要的理论指导意义。本文通过在室内开展河道流速、宽深比、弯曲度、有效光辐射变化等因素对河流净化功能的影响的大量模拟实验，取得以下重要结论：缓流水体水中和底泥中有机物、磷等污染物的含量变化受流速的响应很大。当流速低于0.5m／h时，河道中的各种污染物主要以沉积过程为主。当流速超过1.5m／h时，水动力条件有利于河道中有机物的降解。磷的转化过程同时受磷酸酶与水动力扩散作用的共同影响。在低流速的河道中，碱性磷酸酶在水体磷循环过程中扮演着重要角色。磷在流速低于0.5 m／h的缓流河道中主要表现为原位循环现象。当流速在1.0-2.5m／h时，水体中游离磷、总磷含量最低。当流速超过2.5m／h时，又会造成水体中磷含量的迅速升高。在其他条件相同时，河道宽深比对水体中有机物的降解，磷的循环与水／底泥界面交换等都会产生明显的影响。宽深比在3.0左右，有利于河流中有机物的降解。宽深比小于2.0或大于3.0时，水中磷含量都比较高。因此，科学的设计与构筑城市内河河道的宽深比可以获得最大的有机物降解率和最小的磷释放率。河流弯曲度的增大也有利于水体和底泥中的污染物的净化。而弯曲度太大，又会增大水与底泥的接触面积，造成底泥中污染物向水体扩散而影响水质。实验发现弯曲度为1.6时，最有利于水体有机物的降解及水体磷的固定。城市化发展对河流影响的另一个特点是高大建筑物强烈减少了河流生态系统的有效光辐射。光照强度的改变会影响到水体生物群落的结构与生产力，以及污染物的转化过程。实验发现，日光直射的水体中有机物的含量明显比无直射的水体低12％以上，磷也同样如此。因此，这在城市规划或生态河网建设中要引起高度重视。在河道污染管理与控制方面，也要重视输水水质对城市缓流河道水质的影响。城市河道底泥疏浚也要因地、因时制宜。底泥是河道水中磷与有机物的源与汇。实验发现，底泥温度在15℃以上时，河水中有机物的含量最高，也是河流最易发生黑臭的季节，此时可以配合城市内河置水工程，加大换水量及来水水质管理：而底泥疏浚则应该在底泥温度5℃以下的冬季里进行，这样可以取得更好的效果。更多还原

【Abstract】 With the rapid development of urbanization, the natural structure of rivers has beenchanged, and the pollution has also caused self-purification capacity of river descended.Therefore, the ecological restoration of rivers has already become task of top priority. It isreally important to supervise the construction of city ecological river network andrehabilitating ecological structure and function of river by research on river patterns,especially the relationship between river structure and water body self-purification,environmental capacity & nutrition cycle.This article analyzes factors like speed of flow, the width/depth ratios, the bendingcoefficient and active photosynthesis radiation to the changes of river self-purificationcapacity, and we obtained following important conclusion:The speed of flow has an important effect on the contents of organic matters andphosphorus in water and bottom sludge. When the speed of flow blows 0.5 m/h,contaminations in the river were mainly in the form of deposit. When the speed of flowexceeds 1.5 m/h, the hydrodynamics condition was propitious to the degradation of organicmatters in the river, but it promoted the release of phosphorus of sediment from the bottomof river and caused the rise of nutrient. The course of phosphorus cycling was controlledby alkaline phosphatase and hydrodynamic diffusion effect. Alkaline phosphatase playedimportant role in phosphorus cycling in current speed river. When the speed of flow below0.5 m/h, the phosphorus was cycling in-situ; when the speed of flow exceeds 2.5 m/h, thecontent of phosphorus significantly increased.Under the same hydrodynamic conditions, the width/depth ratios of river broughtobvious infection to the degradation of organic matters in water body, and phosphorus cycle and exchange at the interface of water body and bottom sludge. It was veryconducive to the degradation of organic matters when the width/depth ratios of river at 3.0.When the width/depth ratios of river below 2.0 or exceeds 3.0, the content of phosphorusin water body were high. So, we can achieved the maximal degradation of organic mattersand minimum release of phosphorus by design and construct the width/depth ratios of riverscientifically.Augmented the bending coefficient of rivers could also advantageous to thedecontamination of contaminations in the water body and bottom sludge. But the bendingcoefficient too big could increase the contacted area between water and bottom sludge,which would affect the water quality by the pollutants in the bottom sludge diffuse to thewater body. The experiment result indicated that it would most beneficial to the organicmatters degradation and phosphorus fixation in water body when the bending coefficient ofriver was 1.6.Another effect of urbanized development to the river was the big building intenselyreduced the active photosynthesis radiation of the river ecosystem. The change ofillumination intensity would affect the structure and productivity of critter community inwater body, as well as pollutant conversion process. The experiment discovered that, thecontent of organic matters in water body which under straight sunshine was obviouslylower above 12% than in the water body away from direct sunlight, so was the phosphorus.Therefore, this should cause highly recognition in the city planning and construction of cityecological river network.We should pay attention to the influence of supply water quality to the city slow flowriver in the aspect of management and control of River pollution. Sludge dredging in urbanriver also wants to adapt to place and time. The bottom sludge is the sources and sinks ofthe phosphorus and organic matters in river. The experiment discovered that, when theriver bottom sludge temperature exceeds 15℃, the content of organic matters in riverwater were the highest, which is also the river most prone to be black and smelly, whichcan be in line with the urban replacement of water projects, increase water quantity and input water-quality management; and in order to gain better effect, sludge dredging shouldperform during winter when bottom sludge temperature below 5℃.更多还原