典型生活源污染土性质及演变机理分析

ANALYSIS OF PROPERTIES AND EVOLUTION MECHANISM OF SOIL CONTAMINATED BY TYPICAL MUNICIPAL WASTE

以NaCl、CH3COOH、Na2CO3、Ca-CO3和NH4Cl为典型生活源污染质,通过室内试验、荧光光谱分析和扫描电镜观察等方法对污染土变形和强度特征的演化规律及污染质致污、演化机理进行研究。结果表明:生活源污染质对黏土体的作用可分为酸性或碱性污染质溶解土体中的矿物成分、离子交换或吸附作用和重金属物质或难溶盐类发生的沉淀胶结作用三种方式;Na2CO3为土体提供了一定的碱性环境,导致蒙脱石晶胞结构失稳;NaCl被土中黏粒吸附,增加了扩散层厚度,弱化了土体结构;NH4Cl在土体中发生离子交换作用,使双电层结构变薄,强化了土体结构。生活源污染质降解主要可分为有机质降解产生CH3COOH以及CH3COOH进一步降解形成CO3^2-两个阶段:第一阶段,CH3COOH与土颗粒间的碱性胶结物反应弱化土体强度;第二阶段,CO3^2-与土颗粒间游离的Ca^2+、Mg^2+等反应对土颗粒产生一定的胶结作用,增大土体强度。

In this paper, NaCl, CH 3COOH, Na 2CO 3, Ca-CO 3 and NH 4Cl were used as typical municipal waste to study the evolution rules of deformation and strength characteristics of contaminated soil and the evolution mechanism by laboratory tests, fluorescence spectroscopy and scanning electron microscopy. The results showed that the effects of municipal waste on clay could be divided into three types: mineral composition, ion exchange or adsorption, and precipitation and cementation of heavy metals or insoluble salts. Na 2CO 3 provided a certain alkaline environment for the clay, which led to the destabilization of montmorillonite crystal cell structure. NH 4Cl ion exchange in the clay made the electric double layer structure thinner and strengthened the clay structure. The degradation of municipal waste could be divided into two stages: the degradation of organic matter to produce CH 3COOH and the further degradation of CH 3COOH to form CO3^2-. In the first stage, the reaction between CH 3COOH and alkaline cementation of clay particles weakened the strength. In the second stage, the free Ca^2+ and Mg^2+ reacted with CO3^2- and clay particles produced a certain cementation effect on clay particles and increased the strength of clay.