水化氯铝酸钙对土壤铬的钝化修复及风险评估

本研究采集我国棕壤、红壤、黄壤、黑土和褐土5种典型土壤，制备成Cr （VI）浓度为80mg/kg的污染样品，首次应用极具潜力的层状双金属氢氧化物——水化氯铝酸钙对其进行钝化修复，并从土壤特定基本理化性质以及Cr的赋存形态、生态风险以及健康风险等方面对修复效果进行综合评价，对相关机理进行深入探讨，对使用成本进行简析.结果表明，水化氯铝酸钙可显著增加土壤pH值，并有效降低土壤Cr的活跃性、生态风险和健康风险；土壤Cr的活跃性降幅为59.09%~79.22%，生态风险降幅为14.17%~57.66%，在胃阶段和小肠阶段的健康风险（致癌风险）降幅分别为13.04%~63.04%和22.73%~56.60%.土壤Cr的赋存形态中，除了活跃态以外，修复前后均有部分不活跃态具有生态风险或健康风险.水化氯铝酸钙除了可将活跃态Cr转化到不活跃的沉淀态中，部分或完全地降低其生态风险或健康风险外，还能在一定程度上控制某些土壤中其余不活跃态Cr在毒性浸出实验或in vitro试验中的溶出.在相对最优使用量（m_Cr：m_{水化氯铝酸钙}=1：20）条件下，水化氯铝酸钙钝化修复1m³的Cr （VI）含量为80mg/kg的实际污染建设用地土壤，其试剂成本约为6.4元.作为新型Cr污染土壤钝化修复剂，水化氯铝酸钙有望为我国土壤环境质量和人群健康质量的改善做出贡献.

Immobilization remediation of Cr-contaminated soils by hydrocalumite and the relevant risk assessment

Five typical Chinese soils, including brown soil, red soil, yellow soil, black soil and cinnamon soil, were collected and artificially contaminated with Cr(VI) to a concentration of 80mg/kg. Hydrocalumite, a promising layered double hydroxide, was applied as a first attempt to immobilize the Cr-contaminated soils. The remediation effects were comprehensively evaluated on soil basic physicochemical properties, and fractionation, ecological risk and health risk of soil Cr. The relevant mechanisms and cost were discussed. Results showed that hydrocalumite significantly increased soil pH, and effectively reduced the Cr activity (59.09%~79.22%), ecological risk (14.17%~57.66%) and health (carcinogenic) risk (13.04%~63.04% in gastric phase and 22.73%~56.60% in small intestinal phase) of soil Cr. In addition to active Cr fraction, inactive Cr fraction also contributed to its ecological and health risks before and after remediation. Hydrocalumite could not only transform active Cr fraction into inactive precipitated fraction for a partial reduction or a complete elimination of its ecological risk or health risk, but also further suppress the dissolution of other inactive Cr fraction in certain soils in the TCLP or in vitro test. Regarding the reagent cost, a reasonable 6.4CNY could cover the remediation of 1m³ of actual construction land with a Cr(VI) concentration of 80mg/kg, under the relatively optimum dosage (m_Cr:m_{hydrocalumite}=1:20). As a new-type immobilizing agent for Cr-contaminated soils, hydrocalumite is highly expected to make contributions to the improvement of soil quality and public health.