矿物材料对Cd污染土壤中Cd的钝化效果

采用土壤培养实验，研究了海泡石、钙基膨润土、钠基膨润土、汉白玉和石灰5种矿物材料在3个添加量下对Cd污染土壤pH和CEC、Cd植物有效性、浸出毒性和生物可给性以及Cd形态分布的影响。结果表明：几种矿物材料均可显著提高土壤pH和CEC。与对照相比，添加几种矿物材料后土壤pH提高0.46~1.15个单位，CEC增加5.8%~39.3%，其提高幅度随添加量的增加而增大。添加矿物材料显著降低土壤Cd的植物有效性（DTPA-Cd）、浸出毒性（TCLP-Cd）和生物可给性（SBET-Cd），且DTPA-Cd、TCLP-Cd和SBET-Cd含量的降低比例分别为9.4%~27.5%、6.4%~23.8%和7.7%~20.5%。添加几种矿物材料后，土壤中酸提取态Cd含量显著降低，残渣态Cd含量显著增加，可还原态和可氧化态Cd含量无明显变化。与对照相比，土壤酸提取态Cd含量降低6.2%~31.4%，残渣态Cd含量增加2.8%~9.7%。几种矿物材料中，海泡石和汉白玉对土壤Cd钝化效果相当，且优于其他矿物材料。

Effects of mineral materials on passivation effect of Cd in Cd-contaminated soil

A soil culture experiment was carried out to study the effects of five mineral materials (sepiolite, Ca-bentonite, Na-bentonite, white marble, lime) at three application rates on soil pH, cation exchange capacity (CEC), available Cd, phytoavailability, bioaccessibility, leaching toxicity, and Cd fractions in Cd-contaminated soil. The experimental results indicated that the five mineral materials increased soil pH and CEC significantly. Compared with the control treatment, the pH and CEC increased by 0.46 to 1.15 and 5.8% to 39.3%, respectively, and values increased proportionally with the increases in the amounts of the mineral materials applied to soil. The diethylenetriaminepentaacetic acid (DTPA) extractions, simple bioaccessibility extraction test (SBET) and the toxicity characteristic leaching procedure (TCLP) were applied to measure plant phytoavailability, bioaccessibility, and leaching toxicity of Cd in Cd-contaminated soil. Application of the five minerals remarkably reduced DTPA-Cd, SBET-Cd, TCLP-Cd in a dose-dependent manner by reduction levels of 9.4% to 27.5%, 6.4% to 23.8%, and 7.7% to 20.5%, respectively, compared to the control treatment. The content of acid extractable Cd dramatically decreased and residual Cd increased, while the reducible and oxidizable Cd showed no obvious changes. Compared with the control treatment, the content of acid extractable Cd decreased by 6.2% to 31.4% and that of residual Cd increased by 2.8% to 9.7% under the mineral material treatments. In all, the five mineral materials had a substantial effect on passivating Cd in Cd-contaminated soil, and the best performances were achieved with the sepiolite and Na-bentonite treatments.