重金属离子在长江中下游沿线典型地基中的迁移特性研究

Migration Characteristics of Heavy Metal Ions in Typical Foundations Along the Middle and Lower Reaches of the Yangtze River

长江中下游沿线分布着众多化工企业,近年来在长江大保护政策框架下,沿岸各地陆续进行化工企业搬迁,关停并转留下大量重金属污染场地,对周围环境和水体形成严重威胁.重金属污染物在长江中下游沿线典型地基中的迁移问题逐渐引起重视.以长江南京段典型淤泥质黏土地基为研究对象,采用气动固结设备模拟地基的天然含水率和应力状态,采用土柱试验测试了重金属离子在地基中的对流-弥散-吸附特性参数.研究结果表明:重金属Pb^(2+)和Cd^(2+)在长江沿线典型地基中的分子扩散系数高于一般黏土地基和高岭土地基,这与淤泥质粉质黏土的夹层结构相关.南京段淤泥质粉质黏土对重金属具有明显的吸附作用,其对Pb^(2+)的吸附能力高于对Cd^(2+)的吸附能力,同时水头高度对重金属吸附特性具有一定影响.根据长江沿线的水文地质条件和数值模拟结果,对沿江水质影响较大的是高渗透性土层中污染物的对流作用.研究结果可为长江沿线典型污染物迁移控制提供理论依据.

There are many chemical enterprises along the middle and lower reaches of the Yangtze River.In recent years,under the framework of the Yangtze River protection policy,chemical enterprises have been relocated in various places along the coast,and a large number of heavy metal polluted sites have been shut down and transferred,which has caused serious damage to the surrounding environment and water bodies.The migration of heavy metal pollutants in typical foundations along the middle and lower reaches of the Yangtze River has been paid more and more attention.In this paper,the typical silty clay foundation in the Nanjing section of the Yangtze River is taken as the research object.The natural moisture content and stress state of the foundation are simulated by pneumatic consolidation equipment,and the convection-dispersion-adsorption characteristic parameters of heavy metal ions in the foundation are tested by soil column test.The results show that the molecular diffusion coefficients of Pb^(2+)and Cd^(2+)in typical foundations along the Yangtze River are higher than those in general clay foundations and kaolin foundations,which is related to the interlayer structure of silty clay.The silty clay in Nanjing section has obvious adsorption effect on heavy metals,and its adsorption capacity for Pb^(2+)is higher than that for Cd^(2+).At the same time,the height of water head has a certain influence on the adsorption characteristics of heavy metals.According to the hydrogeological conditions and numerical simulation results,the convection effect of pollutants in the highly permeable soil layer has a greater impact on the water quality along the Yangtze River.The research results can provide a theoretical basis for controlling the migration of typical pollutants along the Yangtze River.