Science of the Total Environment：田间稻麦轮作模式下巯基接枝坡缕石对土壤镉的钝化效应

农业农村部环境保护科研监测所重金属生态毒理与污染修复创新团队在Science of the Total Environment杂志发表题为"Immobilization of soil Cd by sulfhydryl grafted palygorskite in wheat-rice rotation mode: a field-scale investigation"的最新研究成果。

硕士研究生吴义茜为第一作者，梁学峰副研究员和天津农学院孙国红教授为共同通讯作者。研究得到中国农业科学院科技创新工程和中央级科研院所基本科研业务费专项的资助。

Abstract
The safe utilization of heavy metal contaminated farmland has attracted extensive attention of the whole society, and there is an urgent need to develop novel high-efficiency amendments. To clarify the actual remediation effect and potential for large-scale application of sulfhydryl grafted palygorskite (SGP) in Cd polluted soil in wheat-rice rotation mode, a field-scale experiment was conducted. SGP at the dosages of 0.5 g/kg~2.0 g/kg could reduce gain Cd contents by 27.15~59.05% and 16.16~79.47% for wheat and rice, respectively. The maximal decreases of soil available Cd figured out by DTPA extraction in wheat and rice season were 58.18% and 33.67%, respectively. The immobilization ratio for Cd was much more than that of trace elements, including Fe, Mn, Cu, and Zn, Ni. SGP showed an effective immobilization rate for soil Cd under the interference of many elements in the soil, pointing to the targeting and selectivity of its high-efficiency immobilization. It had no lifting effect on soil pH but decreased zeta potentials of soil particles. The sorption of Cd2+ on SGP amended soil could be fitted by the second-order kinetic model and Langmuir isotherm, and the changes of thermodynamic parameters showed SGP strengthened the fixation. SGP made the biological accumulation coefficient and transfer factor of rice grain drop dramatically but had no noticeable effect on these parameters of winter wheat, indicating different botanical responses. SGP as a novel immobilization amendment may provide an efficient and sustainable solution for the remediation of contaminated soil in wheat-rice rotation mode in field-scale.

对重金属污染农用地采取安全利用等风险管控措施保障农产品质量安全是《土壤污染防治法》的明确要求，同时推广应用土壤调理等安全利用技术、创新土壤重金属有效性降低的钝化技术与材料分别被列入《“十四五”土壤、地下水和农村生态环境保护规划》和《“十四五”全国农业农村科技发展规划》。目前镉污染农田土壤钝化修复研究主要集中于中南、华南等地区等水稻主产区，应用较多的土壤钝化调理剂包括石灰类、黏土类和生物炭类等，传统土壤调理剂存在应用剂量偏高、效率有待进一步提升的局限。西南地区部分农田土壤及作物镉含量超标问题引起全社会广泛关注，而适用于西南地区稻麦轮作模式下的钝化材料与技术研究尚不充分。

巯基接枝坡缕石（SGP）是农业农村部环境保护科研监测所自主研发的新型钝化剂，入选农业农村部耕地重金属污染防控联合攻关组第一层次产品。为了阐明稻麦轮作模式下SGP对土壤镉污染实际钝化修复效应，研究团队在四川绵竹开展田间试验。研究发现SGP以0.5g/kg～2.0g/kg剂量施加到表层土壤中，可使小麦和水稻的籽粒镉含量分别降低27.15～59.05%和16.16～79.47%。小麦季和水稻季DTPA提取的土壤有效镉含量最大下降幅度分别为58.18%和33.67%，同时土壤交换态Cd转化为易还原的Fe-Mn氧化物结合态Cd。SGP对Cd的钝化率远高于Fe、Mn、Cu、Zn、Ni等元素，SGP在土壤中多种元素的干扰下对Cd表现出显著的钝化效率，表明其钝化作用的靶向性和选择性。SGP对土壤pH没有提升作用，但降低了土壤颗粒的zeta电位。Cd2+在SGP钝化土壤上的吸附可以用二级动力学模型和Langmuir等温线拟合，化学吸附热力学参数表明SGP增强了Cd2+在土壤颗粒上的吸附。SGP作为一种新型钝化剂，可以为稻麦轮作模式下镉污染农田安全利用提供一种高效、可持续的解决方案。