土壤Cr(Ⅵ)污染的环境问题日益凸显，实现其高效还原固定及长效稳定修复是应对这一问题的关键。针对土壤Cr(Ⅵ)污染修复中面临的还原固定效率受限和修复后Cr(Ⅲ)再氧化问题，本项目以绿色友好型生物炭为基质，采用高还原性纳米硫化铁进行修饰，通过原位煅烧法优化制备高效的生物炭负载纳米硫化铁。借助电化学和活性组分选择性屏蔽等方法，探明纳米硫化铁与生物炭耦合的高效电子传递特征；采用批培养结合XAFS、μ-XRF等技术，明确生物炭负载纳米硫化铁还原固定土壤中Cr(Ⅵ)的效能，阐明其对Cr(Ⅵ)高效固定的微观作用机制及关键影响因子；采用加速老化法结合分子生物学手段，研究生物炭负载纳米硫化铁长期固定铬过程中Cr(Ⅵ)与Cr(Ⅲ)相互转化特征及微生物的潜在驱动规律，揭示其阻控铬再活化的长效稳定机制。研究成果预期可为土壤Cr(Ⅵ)污染的长效稳定修复提供理论依据。

The increasing contamination of soil with Cr(Ⅵ) has been a serious environmental issue. The key points for the remediation of Cr(Ⅵ)-contaminated soils are the effective reduction of Cr(Ⅵ) to Cr(Ⅲ) and the long-term stability of Cr(Ⅲ) in soils. The low immobilization efficiency for Cr(Ⅵ) and the potential secondary pollution risks of Cr(Ⅲ) reoxidation to Cr(Ⅵ) are the main limitations. In this project, nano-sized iron sulfide with effective reduction activity will be introduced to fabricate the efficient biochar supported nano-iron sulfide composites by in-situ calcination method. The coupling features of iron, sulfur, and biochar that promote the electron transfer for Cr(Ⅵ) reduction will be revealed via methods including the electrochemical analysis and selective screening of active components. Batch culture experiments will be conducted to investigate the immobilization capacity of biochar supported nano-iron sulfide composites for Cr(Ⅵ) through reduction, sorption, and precipitation process. Meanwhile, the mechanism and key factors for the efficient immobilization of chromium will be clarified by the techniques including X-ray absorption fine structure (XAFS) and micro X-ray fluorescence (µ-XRF). The transformation characteristics of chromium speciation and the structure abundance of soil microbial community will be monitored during the accelerated aging experiments by the chemical analysis, spectrum analysis of synchrotron radiation, and molecular biology analysis. Finally, the mechanism of inhibiting the chromium reactivation and long-term stability of remediated soils by biochar supported nano-iron sulfide composites will be elucidated. This research will provide scientific supports for the long-term and stable remediation of Cr(Ⅵ) contaminated soils.