Soil heavy metal contamination has increasingly become a serious environmental issue globally, nearing crisis proportions. There is an urgent need to find environmentally friendly materials to remediate heavy-metal contaminated soils. With the continuing maturation of research on using biochar (BC) for the remediation of contaminated soil, nano-biochar (nano-BC), which is an important fraction of BC, has gradually attracted increasing attention. Compared with BC, nano-BC has unique and useful properties for soil remediation, including a high specific surface area and hydrodynamic dispersivity. The efficacy of nano-BC for immobilization of non-degradable heavy-metal contaminants in soil systems, however, is strongly affected by plant rhizosphere processes, and there is very little known about the role that nano-BC play in these processes. The rhizosphere represents a dynamically complex soil environment, which, although having a small thickness, drives potentially large materials fluxes into and out of plants, notably agricultural foodstuffs, via large diffusive gradients. This review is the first to focus on important nano-BC-rhizosphere processes and provides a balanced perspective on the promise of utilizing nano-BC as a remediation material for treating heavy-metal contaminated soil, while contrasting benefits with potential environmental risks that arise from many as yet unanswered research questions.

土壤重金属污染已日益成为全球严重的环境问题，已接近危机程度。迫切需要寻找环保材料来修复重金属污染的土壤。随着利用生物炭（BC）修复污染土壤的研究不断成熟，作为生物炭的重要组成部分的纳米生物炭（nano-BC）逐渐受到越来越多的关注。与 BC 相比，纳米 BC 具有独特且有用的土壤修复特性，包括高比表面积和水动力分散性。然而，纳米 BC 用于固定土壤系统中不可降解的重金属污染物的功效受到植物根际过程的强烈影响，并且关于纳米 BC 在这些过程中所起的作用知之甚少。根际代表了一个动态复杂的土壤环境，虽然其厚度很小，但通过大的扩散梯度驱动潜在的大量物质流入和流出植物，特别是农业食品。本综述首次关注重要的纳米 BC 根际过程，并就利用纳米 BC 作为修复材料处理重金属污染土壤的前景提供了一个平衡的观点，同时将收益与潜在的环境风险进行了对比许多尚未解决的研究问题。