固化稳定化是一种广泛使用的重金属污染土壤修复技术，但该技术的微观作用机制一直是研究的难点。土壤作为典型的多孔介质，结构复杂，异质性强，很多微观过程实验开展难度大。本研究以重金属铅的稳定化为例，借助构建的一维凝胶逆扩散和二维多孔微流控体系为模拟实验手段，尝试研究可控反应条件下孔隙结构中磷酸盐诱导铅的稳定化微观过程，并探讨关键影响因子如有机质、pH值、氯离子、孔隙结构等的影响机制，以期为实际污染土壤修复过程中药剂的传质和修复效率优化提供理论依据。主要研究结果如下： （1）在一维凝胶逆扩散体系中，铅和磷酸盐两种反应物在更靠近阴离子一侧产生反应，稳定化反应速率受溶质扩散系数影响，随着稳定化产物的增多，扩散受限，反应速率逐渐降低。在反应介质中添加有机质后，发生铅络合并与磷酸盐竞争，从而影响了稳定化反应动力学；此外还对初步稳定化晶核产生包裹作用，引起结晶体表面能的降低，从而抑制晶核进一步生长，使沉淀粒径降低3个数量级，结晶形貌由表面平滑、结晶度完好变为更加细碎并伴有粗糙表面和错向镶嵌的结构，最终影响反应产物稳定性。 （2）在二维多孔微流控体系中，随着稳定化反应的启动，呈现出显著的空间异质性格局。微流控体系上下边界处为优势流区，孔喉区间属高流速区，孔隙空间属低流速区。铅稳定化反应引起整体反应体系中孔隙度和渗透率降低约40%，磷酸铅沉淀逐步堆积而产生孔隙堵塞。孔隙堵塞后形成更加狭窄的通道，成为首要的高流速区，直至堆积到一定程度后形成相对闭合空间，流速降为零。利用分形维数模型将空间异质性的反应格局中溶质流体、沉淀、结晶过程进行模拟，用以获取孔隙尺度上的异质性迁移和反应行为特征。分析结果表明，这种空间堵塞异质性主要缘于沉淀产生的不规则流场造成的流速异质性，进而对稳定化反应效率产生影响。 （3）影响因子分析表明，多孔体系中铅稳定化反应受环境条件影响明显。pH值越高，产物结晶度越差、结晶颗粒越小，沉淀迁移性和分布范围也越大；偏酸性条件下产物结晶度高，堵塞程度也高，边界区闭合面积大。氯离子的添加在较宽pH值范围内形成磷氯铅矿，随着氯离子浓度升高产物稳定性也有较好的提升。腐殖酸的添加，造成沉淀产物破碎化，孔隙堵塞的情况变得不明显，整体结晶生长过程不显著。各因子对多孔介质中铅稳定化反应的影响机制有助于理解土壤等实际多孔介质中固化稳定化过程的发生、发展和修复效率。

Solidification and stabilization technology has been widely applied to the heavy metals contaminated soil remediation, but the technological microscopic mechanisms still require much attention and research. As a typical natural porous media, the opaque soil system is too complicated to carry out some in situ experiment on microscopic processes. This work tried to establish a 1D counter-diffusion gelling reactor, and a 2D porous microfluidic reactor as tools to investigate the pore-scale microscopic mechanisms of a typical heavy metal i.e. Lead (Pb) immobilization by phosphates, and examine the related key factors that would control the immobilization efficiency like pH, soil organic matter, symbiotic chloride ions and pore structure etc. The characterization tools includes optical microscope for in-situ observation and XRD, SEM-EDS, TEM, LSCM for ex-situ characterization. The purpose of the work was to provide theoretical basis and strengthening understanding for pratical optimization of the amendments mass transfer and remediation effectiveness during the future soil remediation. Main results were summarized as follows: The immobilization reaction in the 1D diffusion-dominated counter-diffusion environment was a crystallization process as a function of time. The supersaturation appeared in the middle of the reactor. The entrapped humic acid (HA) in the medium had no significant influence on the process of crystal nucleation, but made the growth rate and crystal size decrease. With the increase of mass percentage of HA, the crystal morphology became more fragmented, which can be explained partly by the complexation of HA with Pb, making the contact difficult for the two reactants, and the reaction products of crystal nucleus were wrapped by HA on the surface thus inhibiting the growth of the crystal as indicated by the TEM and LSCM. On the other hand, the mineral convention from secondary lead orthophosphates (PbHPO4) to pyromorphite (Pb5(PO4)3(OH) and Pb5(PO4)3Cl) implied the positive promotion of more stable minerals. This approach provides evidence to understand the effects of HA presence on the stabilization of lead in a more intuitive way. Strong spatial heterogeneity was found in the 2D advection-dominated porous microfluidic systems. Flow field was symmetric without chemical reaction with the preferential flow around vertical borders, and flow speed was higher in pore throats than pore spaces. Immobilization reaction gradually decreased the porosity and permeability of the system by precipitant stacking and pore blocking. The blocked pore channel would become primary high-speed way until a relatively immobile zone formed after sufficient stacking, decreased the fluid speed to zero. Fractal dimension and image-based probability analysis indicated that pore occlusion influenced the mass transfer and immobilization effectiveness. Key factors had significant impacts on the pore-scale immobilization of lead by phosphates. Crystallinity of the precipitants became worse and particle size was smaller with higher pH value, boosting the transport and distribution range widely. In contrast, crystallization was well in acid environment but more immobile region was formed due to significant pore blockage. Chloride ion facilitated the pyromorphite formation under wide range of pH value, improving the stability of reaction products. Humic acid fragmented the precipitant as the same effect in gelling system, therefore the pore blocking situation was not obvious and nearly all pore space was filled with precipitants in a long time. As Pb immobilization in real soil situation was usually along with the dissociation of Pb from unstable carbonate, we simulated the transformation processes from lead carbonate to lead phosphates in 2D porous microfluidic system. The results identified the greatest potential reaction sites were accompanied with small pore density and high diffusion potential. The overall results would provide theoretical and practical implications for field remediation of similar heavy metals.