载入中....
设为首页 收藏本站 联系我们 网站地图
论文网
您现在的位置: 免费毕业论文网 >> 理学论文 >> 生命环境 >> 正文
搜索: 论文

氮污染物通过饱和粘性土层垂直渗透时迁移机理研究

更新时间 2009-12-9 14:03:06 点击数:

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,the desorption rate is low.Through the experimental results of different reduction conditions impact on the nitrogen adsorption process , conclusion that under the conditions of Eh: -375 -150mv, pH: 7 10 ,the stronger of the solution reduction, the higher of its adsorption capacity and adsorption rate.2 Through static conversion experiment, determing nitrification, denitrification transformation process, conversion rate, conversion mechanism, transforming dynamic equations of nitrogen when does not change the reducibility conditions of solution. Determing conversion trend, conversion rate, conversion mechanism of nitrogen when change the reducibility conditions of solution. The results of this part show that: the nitrification and denitrification rate in the clay is rapid, 90 percent of the response is completed in 6 days. In the environment of Eh for 100-300mv, pH for 9-10, nitrification rate constant is less than denitrification rate constant, that is, this conditions is more conducive to the conduct of denitrification. Through the experimental results of different reducibility conditions on the nitrogen transformation process, obtained in the environment of Eh between -375-150mv,enhance the Solution reduction can reduce the nitrogen pollution in groundwater.3 Through dynamic soil column experiments,revealing migration and transformation mechanism of nitrogen pollutants in the saturated clay at the time of occurring vertical migration ,through experiments,determing oxidation-reduction,infiltration height,with the ion on the impact of nitrogen concentration when pollutants through Saturated clay layer.The results of this part show that: The more thicker of the layer, the more stronger of it’s blocking ability on ammonia.Before ammonia penetrate the clay layer,the interception rate is more than 90%.When nitrogen migrate in the saturated clay layer,the main action is adsorption, nitrification. denitrification accounted for a small part. Clay adsorption for ammonia mainly concerned with the cation exchange. Ca2+, Mg2+ concentration is the main factors for adsorption. We divide the chemical transformation of ammonia in the clay into three stages: (1) Weak period of nitrification, leaching time for 1-10 days, at this stage, the effluent nitrate concentration is low, pH is low. (2)Strong period of nitrification, leaching time for 10-20 days, at this stage, the effluent nitrate concentrations is high, H + increased, the effluent pH decreased.(3)Denitrification period , 20 days later, at this stage, the effluent nitrate concentration reduced again, this process will produce a large number of OH-, the effluent pH increased. The change and intensity of this three-stage are impacted by several factors. (1)dissolved oxygen. (2)soil and solution pH, Eh. Through the measure of retardation factor and water chemistry transport parameters of NH4+-N, NO3--N,NO2--N in the clay, conclusion that:With the increasing of clay thickness, the retardation factor of NH4+-N,NO3--N,NO2--N will be increased.That is, the more thick of layer,the block capacity of NH4+-N, NO3--N,NO2--N is greater .And the barrier capable of clay on NH4+-N is stronger than NO3--N,NO2--N. The water chemistry transport parameters of NH4+-N, NO3--N,NO2--N decreased with the increasing of height,that is, the more thick of layers, the more slow of NH4+-N, NO3--N,NO2--N. And soil thickness has little effect on the migration of NO3--N,NO2--N,but has a great impact.on the migration of NH4+-N.4 Establishing transport model of nitrogen in the saturated clay layer. The results show that :The migration process of NH4+-N and nitrogen in the saturated clay layer are in line with the one-dimensional mathematical model. So, we can use the model to predict the concentration trends of nitrogen when it occurring vertical migration in the saturated clay layer . 

【关键词】 氮; 饱和粘土层; 迁移规律
【Key words】 nitrogen; saturated clay layer; migration law
  氮污染物通过饱和粘性土层垂直渗透时迁移机理研究

内容提要 4-8
第1章 绪论 8-20
    1.1 课题研究的背景 8-9
    1.2 地下水中氮的来源、形态分布、转化机理、危害 9-13
        1.2.1 土壤、地下水中氮的污染来源 9
        1.2.2 土壤、地下水中各种氮形态分布 9-10
        1.2.3 粘土中氮转化的过程及机理 10-12
        1.2.4 环境中氮污染及危害 12-13
    1.3 国内外研究现状 13-17
        1.3.1 污染物通过粘性土层方面的研究 14-15
        1.3.2 地下水氮污染方面的研究 15-17
        1.3.3 存在的问题 17
    1.4 论文的研究目的、研究内容、设计思路 17-20
        1.4.1 研究目的 17
        1.4.2 研究内容 17-18
        1.4.3 设计思路 18-20
第2章 氮静态实验研究 20-41
    2.1 氮吸附/解吸理论的研究 20-30
        2.1.1 实验材料与方法 21-23
        2.1.2 实验结果及讨论 23-30
    2.2 氮静态转化理论的研究 30-40
        2.2.1 实验方法 32
        2.2.2 实验结果及讨论 32-40
    2.3 本章小结 40-41
第3章 氮污染物在饱和粘性土中迁移转化实验研究 41-57
    3.1 研究内容 41
    3.2 土柱渗压实验准备阶段 41-43
        3.2.1 实验原理 41-42
        3.2.2 土样采集及预处理 42
        3.2.3 检测项目和分析方法 42
        3.2.4 渗透液的配制 42
        3.2.5 实验装置 42-43
    3.3 土柱渗压实验过程 43-44
    3.4 粘性土层渗透系数的确定 44
    3.5 三氮通过饱和粘性土层时变化规律探讨 44-53
        3.5.1 还原条件和渗透高度对氮浓度的影响 45-47
        3.5.2 出水pH,Eh 的变化及与氮迁移的关系 47-49
        3.5.3 出水各离子浓度的变化及与氮迁移的关系 49-51
        3.5.4 三氮通过饱和粘性土层时穿透、截留、转化探讨 51-53
    3.6 NH_4~+-N、NO_3~--N、NO_2~--N 在粘土中的水化学迁移参数的确定 53-55
        3.6.1 阻滞因子的测定 53-54
        3.6.2 水化学迁移率的测定 54-55
    3.7 本章小结 55-57
第4章 饱和粘性土层氮迁移模型 57-61
    4.1 引言 57
    4.2 迁移模型概化 57-58
    4.3 土柱模拟实验确定模型参数 58-61
第5章 结论 61-63
参考文献 63-68
致谢 68-69
摘要 69-71
ABSTRACT 71-73

返回栏目页:生命环境论文

设为主页】【收藏论文】【保存论文】【打印论文】【回到顶部】【关闭此页