摘要：
原位钝化修复在重金属污染土壤修复中有着不可替代的作用,而修复材料在污染农田中的长期应用效果一直是人们关注的焦点.通过野外大田钝化修复试验,研究了不同添加剂量(0、1.25、1.75、2.50、3.25 kg·m-2)凹凸棒粘土对镉(Cd)污染土壤理化性质及对水稻(Oryza sativa L.)和小麦(Triticum aestivum L.)吸收Cd的影响,采用梯度扩散薄膜技术(DGT)评价修复前后土壤中生物可利用态Cd含量的变化.结果表明,施用凹凸棒粘土显著抑制水稻和小麦籽粒中Cd富集量,第一季降幅分别为68.8%~83.3%与54.7%~75.5%,其中2.5 kg·m-2施加剂量对Cd污染土壤的修复效果最佳.施加凹凸棒粘土同样抑制了作物对Zn、Ni等其他重金属的吸收,而对Se吸收影响并不显著.施加凹凸棒粘土显著提高了土壤pH、阳离子交换量(CEC)和土壤细颗粒含量,相关性分析表明,水稻和小麦籽粒中Cd含量与土壤pH呈极显著负相关性(相关系数分别为-0.72和-0.64),推测土壤pH的升高是导致水稻、小麦籽粒中重金属含量降低的一个重要原因.不同施用量凹凸棒粘土均在一定程度上降低了土壤DGT提取态Cd含量,分别下降了82.8%、85.1%、84.4%和67.1%.连续3年原位钝化修复效果跟踪观察结果表明,凹凸棒粘土可持续降低水稻和小麦籽粒中Cd含量,1.25 kg·m-2和1.75 kg·m-2处理组产出的水稻籽粒中Cd含量由2014年的0.140 mg·kg-1与0.215 mg·kg-1分别降低为2016年的0.094 mg·kg-1和0.120 mg·kg-1.综上,凹凸棒粘土在修复Cd污染农田土壤方面具有广阔的应用前景.%In situ immobilization of heavy metals was non-replaceable for contaminated soil remediation at a large scale. The effectiveness of long-term application of amendments was the great concern. In-situ experiments were conducted to study the effects of different attapulgite clay application (0, 1.25, 1.75, 2.50, 3.25 kg·m-2) on the Cd transformation in rice (Oryza sativa L.) and wheat (Triticum aestivum L.) as well as the soil physicochemical properties. Results showed that attapulgite clay markedly decreased Cd concentration by 56.7%~76.9% and 71.0% in rice and wheat, while the optimum remediation results for Cd-contaminated soil was 2.5 kg·m-2 dose. Except for Se, Zn and Ni uptake by crops could be also inhibited. The application of attapulgite clay could also enhance the soil pH, CEC and fine particle content, and might consequently induce the decrease of the DGT-measured Cd concentration. The DGT-measured Cd concentrations in soils decreased by 82.8%, 85.1%, 84.4% and 67.1%, respectively. The significantly negative correlations between soil pH and Cd concentrations in rice (correlation coefficient R, -0.72) and wheat (R,-0.64) were observed, which should be response for the decrease of the bioavailability of heavy metals. Besides, there was a persistent inhabitation of Cd concentrations in crops from 2014 to 2016 by adding attapulgite, which was reflected by that the Cd concentrations in rice with 1.25 kg·m-1 and 1.75 kg·m-2 attapulgite application were reduced from 0.140 mg·kg-1 and 0.215 mg·kg-1 in 2014 to 0.094 mg·kg-1 and 0.120 mg·kg-1 in 2016, respectively. All datasets in this work indicate that attapulgite clay has potentially broad application in remediation of Cd-polluted field.
