非饱和条件下铬渣污染土壤中Cr(VI)的环境界面行为及调控机制

我国含铬废渣历史堆存量达600万吨，其堆放场地土壤通常受到了严重的Cr(VI)污染，也已成为周边土壤和水体的污染源。当前，针对铬渣污染土壤形成的非饱和土壤-铬渣-H2O体系中 Cr(VI)的形态转化及分配行为的研究尚不深入。课题拟运用土箱试验观测、同步辐射微观原位表征、量子化学理论计算和准化学平衡模拟，构建原位试验-微观观测-理论计算多维研究方法，阐明非饱和铬渣污染土壤环境中含铬次生矿物的演替过程、关键含Cr(VI)次生矿物生成及物相转化动力学；解析Cr(VI)在铬渣、新生次生矿物、土壤颗粒及H2O溶液中的分配机制；明确含Cr(VI)次生矿物-H2O-土壤颗粒界面上，典型含氧酸根和梯度酸碱性等土壤环境条件对Cr(VI)在铬渣-土壤-H2O体系中的分配规律及转化行为的影响机制。预期通过识别铬渣污染地块土壤中Cr(VI)的关键环境行为并明确其调控机制，为铬渣污染土壤修复方法的构建提供理论依据。

Large quantities of Chromite Ore Processing Residue (COPR) stockpiled in China amount to 6 million tons over the years, and the soils at the storage sites are usually severely contaminated with Cr(VI), which have become pollution sources of the surrounding soils and waters. The morphological transformation and distribution behaviors of Cr(VI) in the unsaturated soil-COPR-H2O system within the COPR-contaminated soils are rarely researched. A multi-dimensional research method including soil box tests, in-situ microscopic characterization of synchrotron radiation, quantum chemistry theoretical calculation and quasi-chemistry equilibrium simulation is proposed in this research. The succession processes of chromium-containing secondary minerals, and the generation of Cr(VI)-containing secondary minerals and their phase transformation kinetics in unsaturated zone of COPR contaminated soil will be illuminated; the distribution mechanisms of Cr(VI) in COPR, newly-formed secondary minerals, soil particles and aqueous solution will be analysed; the influential mechanisms of the typical environmental conditions such as oxyanion and gradual acidity and alkalinity conditions on the distribution and transformation behaviors of Cr(VI) at the interfaces of Cr(VI)-containing secondary minerals-H2O-soil particles in the COPR-soil-H2O system will be figured out. It is expected to identify the key environmental behaviors of Cr(VI) in COPR-contaminated soils and clarify the regulation mechanisms, which may provide the theoretical basis for the construction of the remediation methods of the COPR-contaminated soils.