State Key Laboratory of Efficient Utilization of Arid and Semi-arid Arable Land in Northern China/ Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, 100081, PR China.
Guangdong Provincial Key Laboratory of Water Quality Improvement and Ecological Restoration for Watersheds, School of Ecology, Environment and Resources, Guangdong University of Technology, Guangzhou, 510006, PR China.
Chemosphere. 2023 Sep;335:139126. doi: 10.1016/j.chemosphere.2023.139126. Epub 2023 Jun 5.
Both soil irrigation and sulfur (S) are associated with the precipitation of cadmium (Cd)-sulfide in paddy soil, their interaction affecting on Cd solubility and extractability is still unknown. This study primarily discusses the effect of exogenous S addition on the bioavailability of Cd in paddy soil under unsteady pe + pH conditions. The experiment was treated with three different water strategies: continuous dryness (CD), continuous flooding (CF), and alternating dry-wet cycles for one cycle (DW). These strategies were combined with three different S concentrations. The results indicate that the CF treatment, particularly when combined with S addition, had the most significant effect on reducing pe + pH and Cd bioavailability in the soil. The reduction of pe + pH from 10.2 to 5.5 resulted in a decrease in soil Cd availability by 58.3%, and Cd accumulation in rice grain by 52.8%, compared to the other treatments. While it was more conducive to the formation of iron plaque on the root surface in DW treatment with S addition at rice maturing stage and enhanced the gathering of Fe/S/Cd. Structural equation model (SEM) analysis further confirmed a significant negative correlation (r = -0.916) between the abundance of soil Fer-reducing bacteria (FeRB) and sulfate-reducing bacteria (SRB) like Desulfuromonas, Pseudomonas, Geobacter, and the Cd content in rice grains. This study provides a basic mechanistic understanding of how soil redox status (pe + pH), S addition, and FeRB/SRB interacted with Cd transfer in paddy soil-rice tissues.
土壤灌溉和硫（S）都与稻田土壤中镉（Cd）-硫化物的沉淀有关，但其相互作用对 Cd 溶解性和可提取性的影响尚不清楚。本研究主要探讨了在非稳态 pe + pH 条件下，外源 S 添加对水稻土中 Cd 生物有效性的影响。该实验采用三种不同的水分策略进行处理：连续干燥（CD）、连续淹水（CF）和一个干湿循环交替（DW）。这些策略与三种不同的 S 浓度相结合。结果表明，CF 处理，特别是与 S 添加相结合时，对降低土壤 pe + pH 和 Cd 生物有效性的影响最为显著。与其他处理相比，pe + pH 从 10.2 降低到 5.5 导致土壤 Cd 有效性降低 58.3%，水稻籽粒中 Cd 积累降低 52.8%。而在 DW 处理中，S 添加更有利于水稻成熟阶段根表面铁斑块的形成，并增强了 Fe/S/Cd 的聚集。结构方程模型（SEM）分析进一步证实了土壤中 Fer 还原菌（FeRB）和硫酸盐还原菌（SRB），如脱硫单胞菌、假单胞菌、地杆菌等的丰度与水稻籽粒中 Cd 含量之间存在显著的负相关关系（r = -0.916）。本研究为了解土壤氧化还原状态（pe + pH）、S 添加以及 FeRB/SRB 如何与水稻土-水稻组织中 Cd 转移相互作用提供了基本的机制理解。
