巯基化蒙脱石用于镉污染农田安全生产的效果及其持久性

为探讨巯基化蒙脱石（TM）实现镉（Cd）污染农田安全生产的效果及其持久性，开展了连续两年共四季田间水稻试验，研究了在Cd高污染（2.46~3.81 mg ·kg^-1）土壤中，仅第一季施用不等量TM后，不再补施对每季水稻各部位Cd含量和土壤有效态Cd含量的影响.结果发现，TM可显著降低水稻各位Cd含量和土壤中有效态Cd含量，且钝化效果持久性明显.按0.5%和1%施用TM后，第一季水稻各部位Cd含量比对照显著降低，糙米ω（Cd）相比对照的0.98 mg ·kg^-1分别降至0.16 mg ·kg^-1和0.08 mg ·kg^-1，降幅各达84.0%和91.9%，含量低于国家标准GB 2762-2017中Cd的限量值0.2 mg ·kg^-1.0.5%和1%处理下连续种植的后续三季水稻糙米基本都达标，Cd含量分别降低了50.2%~67.8%和56.0%~81.6%.0.5%和1%处理下，第一季土壤有效态Cd质量分数从对照的48.4%分别降至27.9%和18.4%，降低了20.5%和29.9%，后续三季分别降低了10.0%~17.1%和12.4%~20.8%，与对照差异显著.土壤中有效态Cd含量与水稻各部位Cd含量之间存在极显著的正相关关系，TM主要通过降低土壤中有效态Cd含量而减少水稻对土壤Cd的吸收累积，从而使水稻各部位Cd含量降低.综合两年效果试验来看，TM抑制水稻吸收土壤中Cd效果显著，且两年内效果持久性良好，可较好地应用于Cd高污染农田安全生产.

Effect and Persistent Effect of Thiolated Montmorillonite on Safe Production in Cadmium-contaminated Cropland

To explore the effect and persistent effect of thiolated montmorillonite (TM) on safe production in cadmium (Cd) contaminated cropland, a two-year field experiment was conducted with different application amounts of TM. By adding to highly contaminated soils containing 2.46-3.81 mg·kg^-1 Cd with no replenishment, the impacts of TM on concentrations of Cd in different parts of rice and available Cd in soils were investigated. The results showed that TM could significantly reduce the contents of Cd in brown rice as well as the contents and proportions of available Cd in soils, and its persistent effects on the passivation of Cd were obvious. After applying 0.5% or 1% TM to soils, the contents of Cd in different parts of the rice decreased significantly in the first season compared with that in the control. The contents of Cd in brown rice in the first season decreased to 0.16 mg·kg^-1 and 0.08 mg·kg^-1, respectively, by 84.0% and 91.9% compared with that of the control (0.98 mg·kg^-1). Contents of Cd in brown rice were significantly lower than the maximum allowable amount (0.2 mg·kg^-1) set by China (GB 2762-2017). Under the 0.5% and 1% treatments, the contents of Cd in brown rice of the subsequent three seasons under successive planting decreased by 50.2%-67.8% and 56.0%-81.6%, respectively, which were within the allowable amount. The proportions of available Cd in soils in the first season decreased from 48.4% under the control to 27.9% and 18.4%, respectively, which decreased by 20.5% and 29.9% under the 0.5% and 1% treatments. Compared with that in the control, proportions of available Cd in soils of the following three seasons decreased by 10.0%-17.1% and 12.4%-20.8%. There was a significant positive correlation between available Cd contents in soils and Cd contents in various parts of the rice. TM mainly reduced available Cd contents in soils, then reduced the absorption and accumulation of Cd in rice. The results of the two-year field experiment showed significant and continuous effects of TM on inhibiting Cd uptake by rice, which could be applied to the safe production in heavily Cd contaminated cropland.