氮污染物通過飽和粘性土層垂直滲透時(shí)遷移機(jī)理研究

1、氮污染物通過飽和粘性土層垂直滲透時(shí)遷移機(jī)理研究    氮污染物通過飽和粘性土層垂直滲透時(shí)遷移機(jī)理研究 Study on Transport Mechanism of Nitrogen Pollutants in Saturated Clay Layer under Vertical Infiltration 【摘要】 地下水系統(tǒng)中的粘性土層,一直被人們視為隔水層,僅在近些年來才認(rèn)識(shí)到有時(shí)可以作為弱隔水層(或弱透水層)。因此,化學(xué)元素在粘性土層中的遷移動(dòng)力學(xué)規(guī)律一直是研究的薄弱點(diǎn)。在地下水污染防治與修復(fù)技術(shù)中,通常以粘性土作為阻滯污染物遷移的阻截墻或防滲層

2、,然而粘性土并不是絕對(duì)不透水的,在一定的滲透壓下,可能透水,同時(shí)水中的污染質(zhì)也可能穿透粘性土層。因此粘土層的滲透性及污染物在粘土層中的遷移行為、遷移動(dòng)力學(xué)規(guī)律成為地下水污染控制與治理中一個(gè)重要的研究問題。本文在查閱了大量國內(nèi)外文獻(xiàn)的基礎(chǔ)上,以氮這種地下水中最常見的污染物為研究對(duì)象,研究內(nèi)容分為4部分:1通過靜態(tài)吸附/解吸實(shí)驗(yàn),研究不改變?nèi)芤哼€原條件時(shí),氮的靜態(tài)吸附、解吸量,吸附、解吸機(jī)理,吸附、解吸動(dòng)力學(xué)方程。研究改變?nèi)芤哼€原條件時(shí),氮的靜態(tài)吸附容量,吸附機(jī)理,吸附特點(diǎn)。2通過靜態(tài)轉(zhuǎn)化實(shí)驗(yàn),研究不改變?nèi)芤哼€原條件時(shí),氮的硝化、反硝化轉(zhuǎn)化過程,轉(zhuǎn)化率,轉(zhuǎn)化機(jī)理,轉(zhuǎn)化動(dòng)力學(xué)方程。研究改變?nèi)芤哼€原條

3、件時(shí),氮的轉(zhuǎn)化趨勢(shì),轉(zhuǎn)化率,轉(zhuǎn)化機(jī)理。3通過動(dòng)態(tài)土柱實(shí)驗(yàn),揭示氮污染物在飽和粘性土中發(fā)生垂直滲透時(shí)的遷移轉(zhuǎn)化機(jī)理,研究氧化還原性、滲透高度、伴同離子對(duì)氮污染物通過飽和粘性土層時(shí)濃度的影響。4建立飽和粘性土層氮遷移模型。通過以上的研究,更全面的了解氮污染物在飽和粘性土層中垂直滲透時(shí)的遷移,轉(zhuǎn)化機(jī)理和濃度變化規(guī)律。為阻止氮越流遷移,保護(hù)和修復(fù)地下水環(huán)境提供基礎(chǔ)的理論依據(jù)。 【Abstract】 The clay layer in the groundwater system has been seen as impermeable layer. Only in recent years, it h

4、as 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

5、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 contaminantss transfer act

6、ion, 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 s

7、ources,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 t

8、he 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,dynami

9、c 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 ground

10、water 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 adsorpti

11、on 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

12、 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

13、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 equatio

14、ns 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 i

15、s 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 d

16、ifferent 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

17、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

18、thicker of the layer, the more stronger of its 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 a

19、dsorption 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 nit

20、rate 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 red

21、uced 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 o

22、f 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 N

23、O3-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

24、 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 nit

25、rogen when it occurring vertical migration in the saturated clay layer .  【關(guān)鍵詞】 氮; 飽和粘土層; 遷移規(guī)律 【Key words】 nitrogen; saturated clay layer; migration law   氮污染物通過飽和粘性土層垂直滲透時(shí)遷移機(jī)理研究 內(nèi)容提要 4-8 第1章 緒論 8-20     1.1 課題研究的背景 8-9     1.2 地下水中氮的來源、形態(tài)分布、轉(zhuǎn)化機(jī)理、危害 9-13  

26、;       1.2.1 土壤、地下水中氮的污染來源 9         1.2.2 土壤、地下水中各種氮形態(tài)分布 9-10         1.2.3 粘土中氮轉(zhuǎn)化的過程及機(jī)理 10-12         1.2.4 環(huán)境中氮污染及危害 12-13     1.3 國內(nèi)外研究現(xiàn)狀 13-17 &

27、#160;       1.3.1 污染物通過粘性土層方面的研究 14-15         1.3.2 地下水氮污染方面的研究 15-17         1.3.3 存在的問題 17     1.4 論文的研究目的、研究內(nèi)容、設(shè)計(jì)思路 17-20         1.4.1 研究目的 17 &#

28、160;       1.4.2 研究內(nèi)容 17-18         1.4.3 設(shè)計(jì)思路 18-20 第2章 氮靜態(tài)實(shí)驗(yàn)研究 20-41     2.1 氮吸附/解吸理論的研究 20-30         2.1.1 實(shí)驗(yàn)材料與方法 21-23         2.1.2 實(shí)驗(yàn)結(jié)果及討論 23-

29、30     2.2 氮靜態(tài)轉(zhuǎn)化理論的研究 30-40         2.2.1 實(shí)驗(yàn)方法 32         2.2.2 實(shí)驗(yàn)結(jié)果及討論 32-40     2.3 本章小結(jié) 40-41 第3章 氮污染物在飽和粘性土中遷移轉(zhuǎn)化實(shí)驗(yàn)研究 41-57     3.1 研究內(nèi)容 41     3.2 土柱滲壓實(shí)驗(yàn)準(zhǔn)備階段 41-43         3.2.1 實(shí)驗(yàn)原理 41-42         3.2.2 土樣采集及預(yù)處理 42