Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Key Laboratory of Environmental Remediation and Ecosystem Health, Ministry of Education, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
Agricultural and Rural Development Center of Yueqing, Yueqing 325699, Zhejiang Province, China.
Sci Total Environ. 2024 Oct 10;946:174265. doi: 10.1016/j.scitotenv.2024.174265. Epub 2024 Jun 25.
Understanding the spatiotemporal processes governing Cd behavior at the soil-solution-root interface is crucial for developing effective remediation strategies. This study examined the processes of chemical remediation in Cd-contaminated paddy soil using rhizotrons over the entire rice growth period. One-dimensional profile sampling with a 10 cm resolution revealed that during the initial flooding, paddy soil was strongly stimulated, followed by stabilization of porewater properties. X-ray diffraction of freeze-dried porewater confirmed the generation of submicron-precipitates such as CdS under continuous flooding, resulting in low ion levels of water-soluble Cd (<1 μg/L) and sulfate (<10 mg/L) in porewater. Two-dimensional imaging technologies indicated the maximum iron‑manganese plaque (IP) within 20-110 μm of the root surface. Subsequently, monitoring O in the rhizosphere with a planar optode by two 100 cm membranes for a consecutive month revealed significant circadian O variations between the root base and tip. Destructive sampling results showed that acid-soluble Cd in soils, as available Cd, is crucial for Cd uptake by rice roots under continuous flooding. The IP deposited on the root surface, as the barriers of Cd translocation, increased with rice growth and blocked Cd translocation from soil to rice by about 18.11 %-25.43 % at maturity. A Si-Ca-Mg compound amendment reduced available Cd by about 10 % and improved Cd blocking efficiency by about 7.32 % through increasing IP concentration, resulting in the absorption ratio of Cd in the amendment group being half that of the control group. By unveiling the complex Cd interactions at the soil-rice interface, this study lays the groundwork for developing effective agricultural practices to mitigate Cd-contaminated paddy and ensure food safety.
了解控制土壤-溶液-根系界面上 Cd 行为的时空过程对于开发有效的修复策略至关重要。本研究在整个水稻生长期间使用根箱研究了 Cd 污染稻田中化学修复的过程。10 cm 分辨率的一维剖面采样表明，在初始淹水期间，稻田受到强烈刺激，随后稳定了孔隙水性质。冷冻干燥孔隙水的 X 射线衍射证实，在连续淹水条件下会生成亚微米级的 CdS 等亚微米级沉淀物，导致水中水溶性 Cd（<1μg/L）和硫酸盐（<10mg/L）的离子水平较低。二维成像技术表明，在根系表面 20-110 μm 范围内存在最大的铁锰斑块（IP）。随后，通过两个 100 cm 膜的平面光导氧传感器在根际中连续监测 O，发现根基和根尖之间存在显著的昼夜 O 变化。破坏性采样结果表明，在连续淹水条件下，土壤中的酸溶 Cd 作为有效 Cd，对水稻根系吸收 Cd 至关重要。沉积在根表面的 IP 作为 Cd 转运的屏障，随着水稻生长而增加，在成熟时可阻止约 18.11%-25.43%的 Cd 从土壤向水稻转运。硅钙镁化合物改良剂通过增加 IP 浓度降低了约 10%的有效 Cd，提高了约 7.32%的 Cd 阻断效率，从而使改良剂组的 Cd 吸收比例降至对照组的一半。本研究通过揭示土壤-水稻界面上复杂的 Cd 相互作用，为开发有效的农业实践以减轻 Cd 污染稻田和确保食品安全奠定了基础。
