降雨作用下固化稳定化重金属污染土浸出特性的模型试验与数值模拟研究

发布时间：2018-07-28 12:47

【摘要】：目前,固化稳定化技术已广泛应用于重金属污染场地治理,同时酸雨对污染土体的影响不容忽视。有必要对固化稳定化重金属污染土在酸雨条件下的浸出特性及环境安全性进行研究。本文依托国家863计划项目《有色冶金企业场地高风险污染土壤的固化稳定化工艺技术研究与示范》(2013AA06A206),国家自然科学基金《城市化过程中天然沉积土污染演化机理与控制技术研究》(41330641)及江苏省杰出青年科学基金项目《特殊路基填土固化稳定再生利用的关键问题研究》(BK2012022)等课题,选择磷酸盐固化稳定化铅锌镉污染土,通过室内试验研究了降雨作用下磷酸盐固化稳定化重金属污染土的物理化学特性、重金属浸出特性、模型试验下渗流及重金属的浸出特性；并采用Geostudio软件对模型试验进行数值分析。取得以下主要成果：(1)通过对固化土进行硫酸硝酸法浸出试验、解吸附试验和半动态浸出试验,研究固化土的浸出特性。结果表明,固化土重金属Pb、Zn、Cd的硫酸硝酸法浸出较未固化污染土分别降低了66%、27%、50%；三种重金属的解吸附曲线符合Freundlich模型；固化土中Pb、Zn、Cd的浸出机理均为扩散控制。根据US EPA Method 1315计算得到Pb、Zn、Cd的表观扩散系数分别为1.05×10-16 m2/s.7.84×10-13 m2/s、2.11×10-12 m2/s;根据ASTM C1308-08方法计算得到Pb、Zn、Cd扩散系数分别为1.33×10-16 m2/s、1.01×10-12 m2/s、2.89×10-12m2/s。(2)渗透试验和土水特征曲线试验结果表明,固化土的饱和渗透系数为3.46×10-6 m/s,其土水特征曲线的Fredlund-Xing模型拟合参数分别为a=26.6kPa, n=3.68, m=0.51。(3)固化土土柱模型试验研究结果表明：土柱底部渗出液中重金属Pb、Zn、Cd的浓度随时间的变化为初始阶段较高,随后迅速下降,最后保持稳定；同时重金属浓度与渗出液pH值具有较好的线性负相关关系,而与渗出液EC有很好的线性正相关关系。(4)土柱模型的Geostudio数值模拟结果表明,当降雨时间足够长时,土体体积含水率、底部渗出速率最终达到稳定状态,模型底部渗出液中Pb、Zn、Cd浓度的数值模拟结果与模型试验结果相近,GeoStudio软件可较好的模拟土柱模型中重金属污染物的运移和浸出。并且通过拟合得到土柱底部重金属累积浸出率随水土比(降雨入渗量与土柱体积之比)变化的双常数预测方程。
[Abstract]:At present, solidification and stabilization technology has been widely used in the treatment of heavy metal contaminated sites, and the influence of acid rain on contaminated soil can not be ignored. It is necessary to study the leaching characteristics and environmental safety of stabilized heavy metal contaminated soils under acid rain. In this paper, based on the National 863 Project "Research and demonstration of solidification and Stabilization Technology of High risk contaminated soil in Non-ferrous Metallurgical Enterprise" (2013AA06A206), the National Natural Science Foundation of China < pollution Evolution Mechanism of Natural Sedimentary soil in the process of urbanization and its Application Research on Control Technology (41330641) and Project of Jiangsu Province Outstanding Youth Science Foundation, Research on key problems of solidified and stable Recycling of Special subgrade fill (BK2012022), etc. The physical and chemical properties and heavy metal leaching characteristics of Phosphate stabilized heavy metal contaminated soil under rainfall were studied through laboratory experiments. The characteristics of seepage and heavy metal leaching under model test were analyzed numerically by Geostudio software. The main results are as follows: (1) the leaching characteristics of solidified soil were studied by sulfuric acid leaching test, desorption test and semi-dynamic leaching test. The results showed that the sulfuric acid leaching of heavy metal Pb ~ (2 +) Zn ~ (2 +) CD in solidified soil was lower than that of unsolidified contaminated soil by sulfuric acid, the desorption curves of three heavy metals were in accordance with Freundlich model, and the leaching mechanism of Pb ~ (2 +) ZnN ~ (2 +) CD in solidified soil was controlled by diffusion control. The apparent diffusion coefficient of US EPA Method 1315 is 1.05 脳 10 -16 m2/s.7.84 脳 10 -13 m 2 / s 2.11 脳 10 -12 m 2 / s, respectively, and the diffusion coefficient of ASTM C1308-08 is 1.33 脳 10 -16 m 2 / s 1.01 脳 10 -12 m 2 / s 2.89 脳 10 -12 m 2 路s. (2) the results of permeation test and soil-water characteristic curve test show that the diffusion coefficient is 1.33 脳 10 ~ (-16) m ~ (-2) 路s ~ (-1) ~ (-1) 脳 10 ~ (-12) m ~ (2) 路s ~ (-1). The saturated permeability coefficient of solidified soil is 3.46 脳 10 ~ (-6) m / s, and the fitting parameters of Fredlund-Xing model of soil-water characteristic curve are a 26.6 KPA, 3.68, 0.51 respectively. (3) the results of model test of solidified soil column show that the concentration of heavy metal Pb ~ (2 +) ~ (2 +) Zn ~ (2 +) in the exudate at the bottom of the soil column varies with time. Into a higher initial stage, The heavy metal concentration has a good linear negative correlation with the exudate pH value, while it has a good linear positive correlation with the exudate EC. (4) the Geostudio numerical simulation results of the soil column model show that there is a good linear and positive correlation between the heavy metal concentration and the pH value of the exudate. (4) the Geostudio numerical simulation results of the soil column model show that, When the rainfall time is long enough, the soil volume moisture content and the bottom seepage rate finally reach the stable state. The numerical simulation results of Pb ~ (2 +) Zn ~ (2 +) CD concentration in the exudate at the bottom of the model are similar to the results of the model test. GeoStudio software can simulate the migration and leaching of heavy metal pollutants in the soil column model. The double constant prediction equation is obtained by fitting the cumulative leaching rate of heavy metals at the bottom of the soil column with the ratio of soil and water (the ratio of rainfall infiltration to the volume of soil column).
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53

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