Key Laboratory for Environmental Factors Control of Agro-product Quality Safety, Ministry of Agriculture and Rural Affairs, Tianjin, 300191, China; Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin, 300191, China.
Agro-Environmental Protection Institute, Ministry of Agriculture and Rural Affairs, Tianjin, 300191, China.
Chemosphere. 2022 Mar;291(Pt 3):133055. doi: 10.1016/j.chemosphere.2021.133055. Epub 2021 Nov 24.
Sulfur (S) can decrease the bioavailability of Cd in paddy soil, and therefore reduce Cd uptake by rice. However, the dynamic influence mechanism of different forms of sulfur on the bioavailability of cadmium in soil has not been systematically studied. In this study, we used Diffusive gradients in thin films (DGT) technology and soil pore water sampling technology to investigate the effects of different types of S application on the bioavailability of Cd. The three forms of S are elemental sulfur (S), sodium sulfate (SO), and mercapto-grafted palygorskite (MP), which have been treated in six ways according to CK, SL, SH, SOL, SOH, MP (L and H are the low and high levels of treatments). The results showed that soluble and labile Cd concentration was quickly fixed after flooding but activated after rice transplantation. Both MP and SL treatments increased the content of dissolved organic carbon (DOC) and significantly reduced the accumulation of Cd in roots and grains. The Cd content of roots treated with MP was only 0.50 mg kg, which was 77.6% lower than the Cd content in CK (2.22 mg kg). S promotes the reduction and dissolution of Fe, and the formation of FeS/FeS is also one of the reasons for the low bioavailability of Cd, while the SH treatment has a greater effect on lowering pH, so the effect of fixing Cd is not obvious. In addition, SO treatment delays the soil reduction process, so it cannot effectively fix Cd. At the stage of rice maturity, dissolved Cd increased in S treatment, but MP treatment did not have this phenomenon. The possible reason was the consumption of DOC or the oxidation of CdS which caused Cd to enter the soil solution. Taken together, Fe-S play a critical role in controlling the mobilization of Cd in paddy systems.
硫（S）可以降低水稻土中镉的生物有效性，从而减少水稻对镉的吸收。然而，不同形式的硫对土壤中镉生物有效性的动态影响机制尚未得到系统研究。在这项研究中，我们使用扩散梯度薄膜（DGT）技术和土壤孔隙水采样技术来研究不同类型的 S 施加对 Cd 生物有效性的影响。三种 S 形式是元素硫（S）、硫酸钠（SO）和巯基接枝坡缕石（MP），它们根据 CK、SL、SH、SOL、SOH、MP（L 和 H 是处理的低和高水平）进行了六种处理。结果表明，淹水后可溶性和不稳定镉的浓度迅速固定，但在水稻移栽后被激活。MP 和 SL 处理均增加了溶解有机碳（DOC）的含量，并显著降低了根和籽粒中 Cd 的积累。用 MP 处理的根中的 Cd 含量仅为 0.50mgkg，比 CK（2.22mgkg）中的 Cd 含量低 77.6%。S 促进 Fe 的还原和溶解，FeS/FeS 的形成也是 Cd 生物有效性低的原因之一，而 SH 处理对降低 pH 值的影响更大，因此固定 Cd 的效果不明显。此外，SO 处理延迟了土壤还原过程，因此不能有效地固定 Cd。在水稻成熟阶段，S 处理中溶解态 Cd 增加，但 MP 处理没有这种现象。可能的原因是 DOC 的消耗或 CdS 的氧化导致 Cd 进入土壤溶液。综上所述，Fe-S 对控制水稻系统中 Cd 的迁移起着关键作用。
