异质性介质中ENPs对典型重金属赋存形态及运移的影响

According to the practical needs of prevention and remediation of heavy metal contaminated farm land, the migration of ENPs and its effect on the migration and transformation of heavy metals in different conditions is one of the critical scientific issues to be clarified. In the proposed project, quartz sand of different sizes will be coated with organic matter, clay mineral colloid, iron salt, manganese salt, aluminum salt, and microbial film. In addition, intact soil column of natural aeolian sandy soil, manual loessial soil, and yellow cinnamon soil will be collected. The soil and quartz sand with different mechanical structures and surface properties will be used as experimental porous media. Adsorption and desorption of heavy metals on different types of ENPs (e.g., nanosized biochar, graphene oxide) will be determined with perturbations of solution pH and ionic strength (IS). The speciation of heavy metals on ENPs will be characterized. The effects of pH, IS, and flow rate on the transport of ENPs and ENP-bound heavy metals will also be evaluated. This proposal focused on: 1) the adsorption and immobilization molecular mechanism and speciation of heavy metals on ENPs, 2) the migration and transformation mechanism of ENPs in heterogeneous porous medium, 3) the influence mechanism of ENPs on the migration and transformation of heavy metals in heterogeneous porous media, and 4) the migration mechanism of ENPs on the heavy metals contaminated heterogeneous porous media. It is anticipated that the project will reveal adsorption mechanisms of heavy metals on ENPs, clarify the speciation of heavy metals on ENPs, reveal the gowning transport mechanism of ENPs in porous media, clarify the roles and impacts of ENPs on the fate and transport of typical heavy metals in heterogeneous porous media. Findings of this proposal will benefit the scientific assessment of ecological effects of ENPs and ENP-bound heavy metals in the subsurface significantly, and provide important theoretical basis for the rational use, discharge, remediation application of ENPs.

针对重金属污染耕地防控和修复的实际需求，围绕人工纳米颗粒（ENPs）对重金属的迁移转化这一科学问题，利用有机质、粘土矿物、铁盐、锰盐、铝盐、微生物膜等处理不同粒径的石英砂，采集风沙土、塿土及黄褐土及原状土柱，形成机械结构、界面性质不同的异质性多孔介质，改变溶液条件，通过ENPs对铅、砷等重金属的吸附解吸和运移实验，重点研究：1）ENPs对重金属的吸附固定分子机制及赋存形态的影响，2）ENPs在异质性介质中的迁移转化机制，3）ENPs对重金属在异质性介质中迁移转化的影响机制，4）ENPs在重金属污染异质性介质中的运移机制。预期结果将明晰典型阴阳离子型重金属在ENPs上的赋存形态，揭示异质性环境中ENPs的迁移及其对重金属迁移的影响特征及机制，对科学客观评估ENPs及其携带重金属在介质中的生态效应具有重要意义，也可为ENPs的合理使用、排放和土壤重金属污染的纳米修复技术等提供重要的理论依据。

项目通过开展微塑料、氧化石墨烯、纳米生物炭、氮化碳等人工纳米颗粒在土壤地下水环境中的迁移归趋及与重金属交互迁移的研究。探明了离子强度、pH等不同化学条件，及流速、介质粗糙度、介质界面性质等物理条件影响下人工纳米颗粒在饱和多孔介质中的运移机制，明确了矿物质以复合金属氧化物的形式存在于多孔介质中，可显着影响土壤环境中纳米颗粒的运移和转化；证实了纳米颗粒的存在增强了铅镉在多孔介质中的移动性，揭示纳米颗粒进入土壤中对重金属迁移规律的影响及其土壤对污染物环境行为的影响，并完善腐殖酸、水铁矿、高岭石和蒙脱石等土壤成分对多孔介质中纳米颗粒和重金属污染物迁移的影响。此外，项目通过探究表面活性剂存在下微塑料在多孔介质中的迁移行为，揭示了在表面活性剂存在下微塑料滞留的潜在机制。通过项目研究明晰了人工纳米颗粒对重金属污染物在饱和多孔介质中的运移机制，深化了胶体易化迁移理论，对科学客观评价纳米颗粒的环境风险具有重要的意义。.取得以下主要结论：.（1）首次将氢键作用、接触角介入纳米颗粒运移的影响研究，证实石墨相氮化碳间的氢键作用增加了溶液状态下的稳定性；并进一步探究了含氧官能团对二维碳纳米材料与重金属共运移的影响机制；为分析纳米颗粒间或介质间氢键作用提供了重要的理论基础；.（2）率先探究表面活性剂作用下新污染物-微塑料在介质中的迁移行为，并扩展经典DLVO理论，明晰了表面活性剂分子产生的渗透势能和弹性势能对微塑料迁移的作用；通过动态接触角计算表面活性剂在微塑料表面的粘附功，揭示了微塑料迁移能力与表面活性剂粘附功间的关系；