【作者】 张红梅；

【导师】 速宝玉；

【作者基本信息】 河海大学 ， 水力学及河流动力学， 2005， 博士

【摘要】 土壤和地下水污染问题已成为环境污染问题中的一个重要研究课题。而污染物种类繁多,其中对氟污染物的研究,是目前比较关注的环境问题之一。由于氟具有特殊的化学性质,它在土壤中的迁移方向和强度,取决于土壤性质和多种环境要素的共同作用,即氟在多孔介质中的运动是一个复杂的物理化学过程。目前研究污染物在饱和、非饱和土壤中迁移转化规律常用的方法是土柱实验,通过室内实验的设计可以帮助我们分析影响迁移转化的各种因素,揭示污染物在多孔介质中的运移机理,同时也可解决野外实验投资大、周期长、不确定因素较多难以控制等问题,从而缩短了实验研究周期。 本文基于多孔介质中溶质运移理论,在实验设计上完整地从小土柱—大土槽、饱和—非饱和、单层土壤—成层土壤作了全套的大量室内实验研究,采用实验和计算相结合的分析研究方法,归纳总结了氟(氯)离子在不同条件下的运移规律,并对非饱和土壤中土水运动参数进行了拟合计算分析研究。主要研究内容如下: (1)通过不同尺度的饱和、非饱和土柱实验,获得氟(氯)在不同质地、不同分层土壤条件下的运移规律,并利用拟合穿透曲线法反求出运移参数。重点研究了不同的加溶质方式对氟离子在土壤中运移规律的影响。结果表明:氟离子在粘粒含量高的的土壤中的阻滞因子和水动力弥散系数均大于粘粒含量低的土壤中的阻滞因子和水动力弥散系数。在加溶质方式上,同时注入NaF和NaCl混合溶液比单独注入NaF溶液在浓度峰值到达时间上要来得慢些,浓度峰值也小,但在清水淋滤过程中合加NaF和NaCl混合溶液时淋出氟的浓度比单加NaF溶液时要大,这表明钠离子的加入对氟离子的迁移起了促进作用。通过氟氯对比试验进一步明确了氟离子较氯离子更加活泼。(2)对各种不同配比的土壤进行了非饱和土水运动参数的大量实验研究,得到了土水特征曲线、非饱和导水率的关系,并利用VG模型对其进行了拟合分析研究。并将所得参数应用到非饱和—饱和土柱实验计算中,为氟运移理论模型的初步应用奠定基础。(3)通过大土柱和准三维大土槽物理模型实验对氟氯离子在垂向和水平方向上动态迁移特性进行了比较研究,得到了不同特性的运移规律。将小土柱物理模型率定的参数应用到大土槽中,并根据实验结果对参数作了修正。在模型编程计算时,为了减小流速波动对氟、氯离子运移的影响,在模型计算中流速没有按常规方法取平均流速,而是研究了分段流速计算的方法,结果表明,后种计算模拟方法更接近实验值。(4)为了探讨氟离子浓度在水平和垂直方向上的淋滤净化过程,采用经验公式对各测点氟离子浓度衰减变化进行拟合研究,表明其符合指数衰减曲线规律。为建立氟离子浓度峰值衰减与沿程距离的相关关系曲线,对水平和垂直两个方向分别采用二次多项式拟合,从相关系数看,两结果是一致的。更多还原

【Abstract】 Contaminant transportation and transformation in soil and groundwater is an important research topic in soil and environmental science. For many kinds of contaminants, the fluoride pollution had already been paid more and more attention on environment problems. On account of fluorine ion has special chemical characteristic, its chemical property was complex in course of migration in porous media. At present, the soil column test was used to study the rule of contaminant transportation and transformation in saturated-un- saturated soil. By way of the test study in laboratory, we can analysis in- fluencing factors and migration mechanism on solute transport in porous media. At the same time, it can solve some problem which decreased test investment, shorted test periods, controlled uncertain factor difficulty and son on. Therefore, it shorted test research periods. On the basis of solute transport theory in the porous media, the whole test were carried out in laboratory, including small soil column test and large soil tank test with homogeneous and heterogeneous in saturated-unsaturated soil. The rule of migration and transformation of the fluoride(chlorine) was studied by virtue of test and numerical simulation in this dissertation ,and curve fitting analysis were doned about soil water retention curve and unsaturated hydraulic conductivity in different soil. Some achievements were drawn as follows.The rule of transportation of fluoride(chlorine ) were obtained through different texture and heterogeneous soil by a large number of soil column tests in saturated-unsaturated soil. The effects of input solute on F"and Cl~- ion transport was especially discussed by series of experiments . Results showed that the value of coefficient of hydrodynamic dispersion (D) and retardation factor (R_d)in soil (sand and kaoline mix) was greater than that in sand .In the way of input solute , the appearing time of maximum value of concentration with input mix solute (NaF and NaCl) was slower than that with input solute(NaF),and concentration apexes was also smaller .But in the course of input water ,the concentration of F" ion in input mix solute was bigger than that in input solute(NaF).This showed that sodium chloride accelerated transportation of F~- ion in different soil.The soil water retention curve and the unsaturated hydraulic conductivity were obtained by various soil experiment. Parameter fitting were studied by using V-G model, applying these result to model calculation of soil column in saturated-unsaturated soil, and model parameter was corrected. This providea basis for primary application of transport model and obtained parameter. The dynamic migration test of F’ and Cl" was carried out by large earth column and large soil tank in laboratory. We obtained different migration rules of F" and Cl" ion .The parameter with small scale soil column test was used to calculate model parameter with large soil tank, and corrected parameter according to measured data. In the course of numerical simulation, in order to decrease influence for F" and Cl" transportation owing to variable velocity ,the average velocity was not used ,instead of changed velocity with time segment. The calculated values with variable velocity was close to the observed data.In order to study eluviation and decontamination process for F" concentration in horizontal and vertical direction, empirical formula was used to fit rule of F" concentration attenuation .The result showed that exponential function was in accorded with rule. In order to study correlativity curve between F" concentration attenuation and distance , quadratic polynomial was used to fit data in horizontal and vertical direction, the both fitting result accorded. Based on much test theory in laboratory and numerical simulation, combined with present status of pollution of region in Shanxi province, trend of contaminant transportation with time and distance was forecasted by mathematical model and parameter from tests according to hydrogeologic condition and pollution status in studied region, and measures preventing from pollution was pointed out. This provided a basis.in effect for studying ground water environment of Shanxi province.更多还原