氮污染物通过饱和粘性土层垂直渗透时迁移机理研究
Study on Transport Mechanism of Nitrogen Pollutants in Saturated Clay Layer under Vertical Infiltration
【摘要】 地下水系统中的粘性土层,一直被人们视为隔水层,仅在近些年来才认识到有时可以作为弱隔水层(或弱透水层)。因此,化学元素在粘性土层中的迁移动力学规律一直是研究的薄弱点。在地下水污染防治与修复技术中,通常以粘性土作为阻滞污染物迁移的阻截墙或防渗层,然而粘性土并不是绝对不透水的,在一定的渗透压下,可能透水,同时水中的污染质也可能穿透粘性土层。因此粘土层的渗透性及污染物在粘土层中的迁移行为、迁移动力学规律成为地下水污染控制与治理中一个重要的研究问题。本文在查阅了大量国内外文献的基础上,以氮这种地下水中最常见的污染物为研究对象,研究内容分为4部分:1通过静态吸附/解吸实验,研究不改变溶液还原条件时,氮的静态吸附、解吸量,吸附、解吸机理,吸附、解吸动力学方程。研究改变溶液还原条件时,氮的静态吸附容量,吸附机理,吸附特点。2通过静态转化实验,研究不改变溶液还原条件时,氮的硝化、反硝化转化过程,转化率,转化机理,转化动力学方程。研究改变溶液还原条件时,氮的转化趋势,转化率,转化机理。3通过动态土柱实验,揭示氮污染物在饱和粘性土中发生垂直渗透时的迁移转化机理,研究氧化还原性、渗透高度、伴同离子对氮污染物通过饱和粘性土层时浓度的影响。4建立饱和粘性土层氮迁移模型。通过以上的研究,更全面的了解氮污染物在饱和粘性土层中垂直渗透时的迁移,转化机理和浓度变化规律。为阻止氮越流迁移,保护和修复地下水环境提供基础的理论依据。
【Abstract】 The clay layer in the groundwater system has been seen as impermeable layer. Only in recent years, it has been sometimes recognized as the weak impermeable layer (or aquitard). Therefore, the transfer kinetics law of chemical elements in the clay layer has been the weak point of the study. In the technology of underground water pollution prevention and repairation, clay as block walls or impermeable layer was usually used to intercept the transfer of pollutants. However, clay is not absolutely impermeable, at a certain osmotic pressure, it may be flooding, Simultaneously, pollution in the water may also penetrate the clay layer. Therefore, the permeability of clay and contaminants’s transfer action, transfer kinetics in the clay layer become an important research question in groundwater pollution control and management.This paper, basic on a large number of domestic and foreign literature , using nitrogen the most common groundwater pollutants as the research object. By understanding the sources,species distribution ,transfer mechanism and hazard of nitrogen in groundwater. By learning on the research of pollutants in clay layer and nitrogen pollutants in groundwater at home and abroad , founding there are two deficiency in the study of nitrogen in Clay layer. (1)Generally,consider the migration law of nitrogen in clay as the same as the migration law in other Soil. (2)The study on migration ,transform law of nitrogen in Clay layer at different reducibility conditions is little.For the deficiency above,this paper through static adsorption / desorption , static conversion,dynamic conversion of nitrogen in clay, more comprehensive understanding the transfer mechanism and concentration change of nitrogen pollutants in the saturated clay layer under vertical penetration. Provide a basis and foundation for preventing nitrogen flow transfer, protecting and restorating of groundwater environment. The content of this paper is divided into four parts: 1 Through static adsorption / desorption experiments, determing static adsorption/desorption amount, mechanism,kinetics equation of nitrogen when does not change the reducibility conditions of solution.Determing static adsorption capacity, adsorption mechanism, adsorption characteristics of nitrogen when change the reducibility conditions of solution.The results of this part show that:clay have a strong adsorption for ammonia. Absorption rate is 60%, and absorption finished in 2 hours. About absorption mechanism, consider the main force is ionic bond . The desorption of ammonia in the clay is slow, five hours later the desorption is in balance,t
