基于土粒表面电场调控的土壤镉活化/钝化机制

数量庞大的“表面电荷”和密集分布的“表面氧原子”是土壤矿物和有机胶体的基本特征，因此“电场与表面氧原子”在土壤重金属离子的固定与释放中扮演重要角色。基于量子力学分析，申请者发现黏土矿物表面氧原子与金属阳离子之间存在一种新的共价作用：极化诱导共价，且发现该共价作用可通过调节黏土矿物表面电场进行调节。本项目将通过调节电解质构成来调节土壤电场强度，进而探索土壤电场强度与土壤Cd(Ⅱ)静电吸附能和极化诱导共价吸附能间的定量关系，明确极化诱导共价在土壤Cd(Ⅱ)界面吸持中的主导地位；在此基础上探索静电能和极化诱导共价能对土壤Cd(Ⅱ)吸附/解吸平衡与速率的影响，最终阐明土壤Cd(Ⅱ)活化/钝化的土壤电场调控效果与机制。其创新性在于：基于Cd(Ⅱ)吸持的电场依赖性共价作用力研究，揭示土壤Cd(Ⅱ)吸附/解吸、活化/钝化新机制，从而丰富并深化土壤重金属离子界面反应理论，并为土壤镉污染风险管控提供新思路。

The large amount of surface charges and surface O atoms are basic features of soil inorganic and organic particles. The surface O atoms and the electric fields play key roles in the fixation and release of soil heavy metal cations. Based on the quantum mechanism analysis, the applicant of this project has discovered a new covalent interaction between the surface O atoms on clays and the metal cations: polarization induced covalent bonding. Meanwhile, the discovered covalent bonding can be regulated by adjust the electric field strength at clay particle surface. This project aims to study the quantitative relation between soil electric field strength and polarization induced covalent bonding/electrostatic adsorption energies of Cd(Ⅱ) in soil, and the strength of soil electric field will be adjusted by adjusting the electrolytes composition. In this way, we can specify the domination of polarization induced covalent bonding on cadmium activation-passivation in soil. Based on this, we can further explore the influences of polarization induced covalent bonding and electrostatic energies on adsorption-desorption equilibrium and kinetics of soil cadmium, and thus finally clarify the effects and mechanisms of the activation/passivation adjustment of soil cadmium through adjusting soil electric field. The original innovations of this study is: based on the study of electric field dependent covalent interaction of Cd(Ⅱ), the new mechanism of adsorption-desorption and activation/passivation of soil Cd(Ⅱ) can be revealed; thus, we can enrich and deepen the theory of soil heavy metal interface interaction and provide new idea about risk management of soil Cd(Ⅱ).