层状结构包气带土中氟运移规律试验研究

发布时间：2018-06-14 10:16

本文选题：层状包气带土 + 氟运移　；参考：《成都理工大学》2015年硕士论文

【摘要】：包气带是土颗粒、空气、水三者同时存在的一个复杂系统,作为连接地表水、大气水和地下水的一个重要纽带,在水循环中起着重要作用。包气带土也是地表溶质进入地下水的必经通道,溶质在迁移的过程中与土体发生一系列物理、化学、生物等作用,使包气带对溶质运移有一定阻滞作用。在自然界中层状土分布广泛,研究表明层状土中的溶质运移比均质土复杂得多,氟作为地下水中典型的污染物,对人类健康有重要影响,因此研究层状结构包气带土中氟运移规律有重要意义。本文以地质灾害防治与地质环境保护国家重点试验室团队重点课题:非饱和溶质迁移转化规律试验研究(项目编号:SKLGP2011Z001)为依托,在总结前人研究包气带土溶质运移的基础上,对影响层状土中溶质运移的因素进行分析,通过室内土柱试验对不同分层方式、水分供给方式和溶质供给方式下层状包气带土中水分和氟的运移规律进行研究。为弥补室内试验在时间上的局限性,结合Hydrus-1D软件对多种不同分层方式、不同水头高度和不同溶质供给条件下氟在层状包气带土中运移规律进行数值模拟,主要研究成果如下:(1)层状土中湿润锋运移分为两个阶段:第一个阶段,在分层界面以上入渗速率呈非线性变化且随时间的增加而减小;第二个阶段,在分层界面以下入渗速率随时间增加不变。湿润锋入渗深度随时间增加的变化关系可以用y=axb形的幂函数进行表征。层状包气带土剖面上含水率随时间呈反“Z”字形变化,稳定时的含水率接近土体的饱和含水率。(2)土体表层遭受高浓度氟瞬时污染后在15mm/12h降雨强度下,氟在由细及粗和由粗及细两种分层结构土体中运移时,随着时间增加土柱各监测点氟浓度先增加后减小,由于土壤颗粒的吸附作用两种土体结构峰值浓度随时间和深度的增加逐渐降低。比较两种土体结构,氟在由粗及细的土体结构中运移快,试验结束时由细及粗的层状土中氟主要富集在土体上部,由粗及细层状土中氟富集在土柱底部。因此在非饱和条件下由细及粗的层状结构对溶质的阻滞作用强于由粗及细的层状结构。(3)当土柱表层遭受高浓度氟瞬时污染后在定水头入渗和降雨入渗条件下,氟在相同分层方式的土柱中运移规律基本相同,浓度均随时间先增大后减小,但在氟运移速率上有较大差异。氟运移受水分运移的影响,在定水头入渗条件下土壤中水流速度快,对流作用使氟的运移速率也快,试验结束时氟集中在土柱底部;在降雨入渗条件下氟运移受降雨强度的影响,土壤中水流速率慢,氟在土壤孔隙中向下运移速率慢,试验结束时氟主要集中在土柱表层。(4)在同一降雨强度和同一分层方式下改变氟的供给方式,连续供给溶质条件下随着时间增加氟浓度先增大后趋于稳定,试验结束时氟在土柱中均匀分布,浓度与初始的供给浓度接近;瞬时供给溶质条件下,由于降雨的淋溶作用,随时间增加氟浓度先增大后减小,试验结束时氟集中在土柱表层。(5)通过Hydrus-1D软件对不同分层方式、定水头高度和溶质供给条件下,层状土中氟的运移规律进行数值模拟。不同分层方式条件下层状土中氟运移规律不同,表层土体介质渗透性对溶质的运移具有控制作用,表层土颗粒越细,对氟运移的阻滞作用越强,当表层土体相同时,第二层土中细颗粒越多对溶质的阻滞作用强,因此细、中、粗的结构对地下水污染物防治效果最好。不同定水头高度条件下氟随时间和深度的变化不大,水头高度增加氟运移速率略有增大。相同质量的溶质分不同次数供给,供给次数越多表层土中出现的峰值个数越多,峰值浓度越低。(6)结合室内土柱试验和数值模拟,层状包气带土中氟主要随土体水分运动发生运移,不同分层方式、水分供给方式和溶质供给方式都会不同程度的影响氟在层状包气带土中的运移。
[Abstract]:The aeration zone is a complex system of soil particles, air and water at the same time. It plays an important role in the water cycle as an important link between the surface water, the atmospheric water and the groundwater, which is also an important link between the surface water, the atmospheric water and the groundwater. It is also a necessary channel for the surface solute to enter the ground water. The solute has a series of physics and chemistry in the process of migration with the soil. In nature, the layer soil is widely distributed in nature, and the study shows that the solute transport in the layered soil is much more complex than the homogeneous soil. As a typical pollutant in the groundwater, fluorine has an important influence on human health. Therefore, the study of the law of fluorine migration in the layered soil zone soil is heavy. In this paper, based on the experimental research on the transformation law of unsaturated solute transfer (project number: SKLGP2011Z001), based on the key subject of the National Key Laboratory of geological disaster prevention and geological environmental protection, the factors affecting the solute transport in the layered soil are analyzed, and the factors affecting the solute transport in the layered soil are analyzed. In order to make up for the limitation of the laboratory test in time, a variety of different stratification methods, different water head height and different solute supply conditions are applied to the fluorine in the layer under the indoor soil column test to study the movement of water and fluorine in the layer soil layer soil with different layers, water supply and solute supply. The main research results are as follows: (1) the migration of humid front in the layered soil is divided into two stages: the first stage, the infiltration rate above the stratified interface is nonlinear and decreases with the increase of time; the infiltration rate below the stratified interface increases with time in the second stage. The relationship between the depth of the infiltration depth and the time increased with time can be characterized by the power function of the y=axb shape. The water content on the layered soil profile shows a reverse "Z" shape change with time, and the water cut at the stable time is close to the saturated water content of the soil. (2) the soil surface is subjected to a high concentration of fluorine at the 15mm/12h rainfall intensity, and the fluorine is in the thin layer. The fluorine concentration increases first and then decreases with the increase of time and depth, and the peak concentration of two soil structures decreases with time and depth as the adsorption of soil particles increases. Compared to the two soil structures, the fluorine is moved quickly from the coarse and fine soil structure, and the test of fluorine is faster than two soil structures. At the end of the test, fluorine in the thin and coarse layered soil is mainly enriched in the upper part of the soil, and the fluorine is enriched at the bottom of the soil column in the coarse and fine layered soil. Therefore, under unsaturated conditions, the blocking effect of the thin and coarse layered structure on the solute is stronger than that of the coarse and fine layered structure. (3) when the surface of the soil column is subjected to a high concentration of fluorine, it is injected into the fixed water head. Under the conditions of infiltration and rainfall infiltration, the movement of fluorine in the same stratified soil column is basically the same, the concentration increases first and then decreases with time, but there is a great difference in the rate of fluorine migration. The flow of fluorine is influenced by the water migration, the flow rate of the soil is fast and the flow rate of the fluorine is fast under the condition of fixed water head infiltration. Fluorine is concentrated at the bottom of the soil column at the end of the soil. The flow rate of fluorine in the soil is slow and the rate of fluorine moves slowly down in the pore of soil under the condition of rainfall infiltration, and the fluorine is mainly concentrated on the surface of the soil column at the end of the experiment. (4) the supply of fluorine is changed under the same rainfall intensity and the same layer mode, and the solute is continuously supplied. Under the conditions, the fluorine concentration increased first and then stabilized, and the fluorine was evenly distributed in the soil column at the end of the test. The concentration of the fluorine was close to the initial supply concentration. The fluorine concentration increased first and then decreased with the leaching of the rain. The fluorine concentration was concentrated on the surface of the soil column at the end of the test. (5) through Hydrus-1D The movement of fluorine in layered soil under different stratification modes, fixed water head height and solute supply is simulated by software. The migration law of fluorine in layer soil under different stratification conditions is different. The permeability of surface soil medium has control effect on the transport of solute, the thinner the surface soil particles, the stronger the retardation of fluorine migration. When the surface soil is the same, the more fine particles in the second layers have strong blocking effect on the solute, so the fine, medium and coarse structures have the best effect on the prevention and control of the groundwater pollutants. The more the number of supply and supply times, the more peak values in the surface soil, the lower the peak concentration. (6) combined with the indoor soil column test and the numerical simulation, the fluorine in the layered soil and soil is mainly moved with the soil moisture movement, and the different stratification ways, the water supply mode and the solute supply mode will affect the fluorine in the stratified air zone in varying degrees. Movement in the soil.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53;X523

【共引文献】