【作者】 唐璐；

【导师】 薛生国；

【作者基本信息】 中南大学 ， 环境工程， 2025， 博士

【摘要】 冶炼场地重金属在“固相-胶体-液相”的多相传输过程,导致土壤-地下水污染共存情况普遍,严重制约冶炼遗弃场地的再开发和安全利用。水分散性胶体作为重金属跨介质运输的重要载体,其与重金属之间的交互作用是影响重金属地球化学循环过程的关键。然而,重金属胶体在土水介质中的分配行为不清,迁移阻控机制不明,难以支撑场地土壤-地下水协同修复材料设计和技术开发。论文以典型冶炼场地为研究对象,围绕“重金属胶体环境行为”和“土水污染协同阻控”开展研究,明确了场地土壤-地下水重金属的空间分异特征,阐明了重金属胶体在物理/化学因素影响下的稳定性和活化机制,揭示了胶体驱动下重金属在土水多介质的迁移转化规律,研发了多金属同步矿化材料,分析了其对重金属“胶体化”的弱化作用,揭示了多金属快速稳定成矿机理,同时基于“以土治水”策略,利用土壤修复层作为地下水重金属的捕获区,形成土壤-地下水多金属污染协同修复技术体系,并通过场地试验动态评估了修复技术的长效性,为冶炼场地土壤-地下水中重金属迁移转化和污染协同共治提供理论支撑和实践参考。主要研究成果如下:（1）多技术联合探明场地水文地质条件和污染物空间分布特征。结合高密度电阻率成像（ERT）和钻孔数据,地层结构主要分为杂填土层、粘土层和砾石层,含水层对应的视电阻率为15Ω·m。地下水水化学类型以SO₄-Na型为主,受到矿物风化、离子交换及人类活动等过程影响。土壤和地下水Pb污染较轻,Zn、As和Cd污染程度较高。构建污染物空间分布可视化模型,土壤重金属分布呈现“斑块聚集”特征,具有强烈的异质性。地下水污染羽重金属的分布与表层土壤污染点位和地下水流场有关,Cd的污染扩散范围更大。（2）水分散性胶体驱动重金属的多相传输过程。地下水中40.4%、44.8%、34.2%和37.6%的Zn、Pb、As、Cd与水分散性胶体相关。地下水重金属胶体分布具有尺寸效应,Zn（均值90.5%）和As（均值94.4%）更倾向于和大分子量胶体（300 kDa～450 nm）结合。与地下水相比,土壤重金属在胶体中分布比例更高。金属纳米颗粒、铁氧化物、黏土矿物和溶解性有机质（DOM）是水分散胶体的主要组成部分。重金属以胶体形式的迁移是场地多介质污染形成与扩散的重要机制。（3）土壤胶体团聚行为影响重金属胶体在土水多介质中的分配行为。Na⁺、Ca²⁺和Al³⁺作用下,土壤胶体的临界聚沉浓度（CCC）分别为19.3、2.7和0.3 mM,团聚能力高低依次为Al³⁺>Ca²⁺>Na⁺,阴离子的CCC大小为Cl^-<SO₄^2-。外源电解质的加入显著改变了土壤胶体的界面特性。随着离子价态和离子强度的增加,Zeta电位绝对值减小,颗粒之间的斥力能垒明显降低,稳定性降低。结果表明环境中碱性条件、高价阳离子和高离子强度的存在促使土壤胶体团聚,以胶体形式存在的重金属浓度降低,重金属“胶体化”作用减弱。（4）胶体易活化迁移并导致场地重金属污染扩散。模拟土柱在多次冻融循环后淋出液中的颗粒数量浓度从2.7×10⁸±2.4×10⁷颗粒/m L增加至1.4×10⁹±1.2×10⁸颗粒/mL,平均增加了80.1%。冻融循环增大了孔隙尺寸,连通性较好的（配位数≥5）的孔隙数量是原始土壤的1.53倍,有助于形成新的优先流路径。实验中重金属持续释放,淋出液中胶体Zn、Cd、Pb和As的平均占比为61.5%、47.6%、68.0%和59.2%,而且除Pb外,Zn、Cd和As浓度都超过地下水Ⅲ类标准。冻融扰动通过胶体活化释放和迁移路径强化的协同作用,促进重金属胶体迁移。（5）研发改性钙/铝-层状双氢氧化物（CaAl-LDH@500）功能材料,有效减弱重金属“胶体化”。CaAl-LDH@500对Zn、Cd和As的最大吸附容量分别达到286.0、248.3和14.1 mg/g。材料对实际地下水重金属具有优异的吸附效果,并使土壤重金属浸出浓度在实验2周内同步达到地下水Ⅲ类标准。修复过程中,胶体Zn、Cd和As占比分别减少45.5%、38.1%和22.3%,减少重金属以胶体形式的迁移。透射电镜（TEM）和X射线光电子能谱（XPS）结果表明,CaAl-LDH@500通过同晶取代和表面吸附作用,实现Zn、Cd和As同步矿化,阻止重金属跨介质迁移。（6）利用功能材料构建土壤修复层,结合地下水抽出处理,形成基于“以土治水”的土壤-地下水多介质协同修复技术体系。室内模拟实验中土壤修复层可以有效截获地下水重金属,并在长达20次的循环中,地下水重金属浓度和土壤浸出浓度稳定低于地下水Ⅲ类标准限值。不同自然场景中修复功能材料对重金属修复具有长效稳定性。在典型冶炼场地开展为期13个月的修复试验,地下水重金属浓度和土壤浸出风险始终低于标准阈值,表明该技术对土壤-地下水重金属污染具有实际的修复效果。图72幅,表17个,参考文献284篇更多还原

【Abstract】 Heavy metal（loid）s at smelting sites undergo multiphase transport processes in the"solid phase-colloid-liquid phase"system,leading to widespread co-occurrence of soil-groundwater contamination,which severely restricts the redevelopment and safe utilization of abandoned sites.Water-dispersible colloids,as critical carriers for cross-media transport of heavy metal（loid）s,play a key role in their geochemical cycling through interactions with metal（loid）s.However,the partitioning behavior of heavy metal（loid）s-bearing colloids complexes in soil-water systems remains unclear,and the mechanisms governing their migration and control are poorly understood,posing challenges for designing materials and technologies for synergistic soil-groundwater remediation.The thesis focuses on typical smelting sites,addressing“heavy metal（loid）s-bearing colloids environmental behavior”and“pollution control in soil-water systems”.The spatial distribution characteristics of heavy metal（loid）s in soil and groundwater at the smelting site were clarified,and the stability and activation mechanisms of heavy metal（loid）s-bearing colloids under physicochemical influences were elucidated.The colloid-driven migration and transformation patterns of heavy metal（loid）s across soil-water multiphase interfaces were revealed.A synchronous multi-metal mineralization material was developed,which significantly weakens heavy metal（loid）s“colloidization”and achieves rapid stabilization through metal-mineral phase formation mechanisms.Furthermore,based on the strategy of“Soil for Water Remediation”,an integrated remediation technology for multi-metal contamination in soil-groundwater was employed.The long-term effectiveness of this technology was dynamically validated through field trials,providing theoretical support and practical guidance for understanding heavy metal（loid）s migration-transformation processes and enabling co-remediation of soil-groundwater pollution at smelting sites.The main research results are as follows:（1）Elucidating the hydrogeological conditions and spatial distribution characteristics of contaminants at the site forms the basis for investigating heavy metal（loid）s migration and transformation.By integrating Electrical Resistivity Tomography（ERT）and borehole data,the stratigraphic structure is classified into three primary layers:a miscellaneous fill layer,a silty clay layer,and a gravel layer,with an apparent resistivity of 15Ω·m corresponding to the aquifer.Groundwater chemistry is influenced by mineral weathering,ion exchange,and anthropogenic activities.Soil and groundwater exhibit relatively low Pb contamination,while Zn,As,and Cd demonstrate higher contamination levels.A visual model of contaminant spatial distribution establishes correlations between soil pollution and groundwater contaminant plumes.Soil Pb,Zn,As,and Cd distributions display patchy aggregation patterns with significant heterogeneity.Spatial distributions of heavy metal（loid）s in groundwater plumes correlate with surface soil contamination points and groundwater flow fields,with Cd exhibiting more extensive migration.（2）Water-dispersible colloids drive the multiphase transport of heavy metal（loid）s.In groundwater,40.4%of Zn,44.8%of Pb,34.2%of As,and37.6%of Cd were associated with colloids.Heavy metal（loid）s colloidal distribution exhibited size-dependent characteristics,primarily binding to high-molecular-weight colloids（300 kDa-450 nm）,with Zn（mean 90.5%）and As（mean 94.4%）demonstrating stronger affinities for larger colloidal particles.Compared to groundwater colloids,soil colloids contained higher proportions of heavy metal（loid）s.Metal（loid）s-bearing nanoparticles,iron oxides,clay minerals,and dissolved organic matter（DOM）,constituted primary colloidal components actively participating in metal（loid）s transport.Colloidal-mediated transport represents a crucial mechanism for heavy metal（loid）s migration at the soil-groundwater interface.（3）Soil colloidal aggregation behavior governs the partitioning of heavy metal（loid）s colloids in soil-water multiphase media.Under the influence of cations(Al³⁺,Ca²⁺,Na⁺),the critical coagulation concentrations（CCC）for soil colloids were determined to be 19.3,2.7,and0.3 mM,respectively,demonstrating a coagulation capacity hierarchy of Al³⁺>Ca²⁺>Na⁺.For anions,the CCC followed the order Cl^-<SO₄^2-.Exogenous electrolyte addition significantly altered colloidal interfacial properties:with increasing ionic valence and strength,the absolute Zeta potential decreased,leading to substantial reduction of repulsive energy barriers between particles and consequent stability decline.Further separation of ionic species and colloidal-bound fractions revealed that alkaline conditions,polyvalent cations,and elevated ionic strength promoted colloidal aggregation,thereby suppressing the release of heavy metal（loid）s-bearing colloids and effectively weakening the“colloidization”effect of heavy metal（loid）s.（4）Colloids are prone to mobilization and migration under freeze-thaw disturbances,exacerbating the spread of heavy metal contamination at the site.In simulated soil columns,particle number concentrations in leachates increased from an initial 2.7×10⁸±2.4×10⁷ particles/mL to1.4×10⁹±1.2×10⁸ particles/m L after multiple freeze-thaw cycles,showing an average increase of 80.1%.Freeze-thaw cycling enlarged pore dimensions,with the quantity of well-connected pores（coordination numbers≥5）reaching 1.5 times that of pristine soil,facilitating new preferential flow path formation.Continuous heavy metal release persisted throughout freeze-thaw experiments,with colloidal-bound fractions remaining relatively stable:Zn（61.5%）,Cd（47.6%）,Pb（68.0%）,and As（59.2%）on average.Furthermore,Zn,Cd,and As concentrations consistently exceeded Class III groundwater quality standards,except for Pb.Freeze-thaw disturbances promote colloidal metal（loid）s migration through synergistic mechanisms involving colloid activation/release and enhanced migration pathways.（5）A novel CaAl-LDH@500 functional material was developed for simultaneous mineralization of Zn-Cd-As co-contamination in polluted sites and weaken the“colloidization”effect of heavy metal（loid）s,revealing the mechanistic basis for multi-metal（loid）s synchronous ultra-stable mineralization.The maximum adsorption capacities of CaAl-LDH@500 reached 286.0,248.3,and 14.1 mg/g for Zn,Cd,and As,respectively.This material demonstrated superior removal efficiency for heavy metal（loid）s in actual contaminated groundwater.In soil incubation experiments,the addition of 2%CaAl-LDH@500 achieved simultaneous compliance with Class III groundwater quality standards for Zn,Cd,and As leaching concentrations within two weeks.SEM,TEM,and XPS characterization confirmed that multi-metal（loid）mineralization was accomplished through isomorphous substitution and surface adsorption mechanisms,preventing the cross-media migration of heavy metal（loid）s.（6）A soil-groundwater synergetic remediation technology was developed based on a“Soil for Water Remediation”strategy,integrating functional soil remediation layers with pump-and-treat systems for simultaneous multi-metal remediation.Laboratory simulations demonstrated this technology effectively immobilized groundwater Zn,Cd,and As,maintaining concentrations below Class III groundwater standards through 20 operational cycles.Throughout cycling,surface remediation layers successfully intercepted heavy metals from groundwater while maintaining soil leachate concentrations of Zn,Cd,and As below regulatory thresholds.CaAl-LDH@500 exhibited persistent mineralization stability under repeated dry-wet alternations and freeze-thaw cycles.Field validation at a typical smelting site achieved 13-month continuous compliance,with both soil leachability risks and groundwater metal concentrations below Class IV standard limits,confirming the practical feasibility of coordinated soil-groundwater heavy metal remediation.更多还原