| 水分管理对稻田土壤铁氧化物形态转化的影响及其与镉活性变化的耦合关系 |
| 摘要点击 4608 全文点击 492 投稿时间：2021-11-11 修订日期：2021-12-20 |
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| 中文关键词 农地土壤 水分管理 镉(Cd) 铁氧化物 生物有效性 |
| 英文关键词 farmland soil water management cadmium (Cd) iron oxide bioavailability |
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| 中文摘要 |
| 稻田土壤水分管理过程中铁氧化物的形态转化对土壤镉（Cd）活性和水稻Cd累积具有重要影响.以西南地区紫色水稻土为研究对象，通过室内培养试验，探讨了淹水管理方式（持续淹水，CW；干湿交替，DW）联合铁氧化物（针铁矿，G-Fe；铁粉，Fe）施用对Cd污染土壤的pH、氧化还原性质（Eh、pe+pH）、铁氧化物形态转化和Cd有效性变化的影响，分析了水分管理驱动下铁氧化物形态转化与土壤Cd活性演变的耦合关系.结果表明CW管理可显著降低土壤Cd有效性，淹水93 d后DTPA-Cd降低了17.7%~39.2%，CW联合Fe或G-Fe施用显著提升了对土壤Cd的钝化效果，其中G-Fe短期钝化效果好，淹水14 d后DTPA-Cd的含量较对照降低24.3%，而Fe则可持续钝化土壤Cd，淹水93 d后DTPA-Cd的降幅为39.2%，干湿交替下施用铁氧化物则对土壤Cd无钝化效应.相关性分析表明，无定形铁（Feo）的形成（P<0.01）是驱动土壤Cd有效性变化的主要原因：CW使土壤pH逐渐降低并稳定在7.4左右，且土壤保持还原状态，促进了土壤铁氧化物由结晶态（Fec）向Feo转化，进而促使Cd由可交换态向铁锰结合态转化，并最终导致Cd有效性降低；CW联合Fe、G-Fe施用显著提升了Feo的含量和比例，从而强化了对土壤Cd的钝化效果.研究结果揭示了水分管理联合铁氧化物施用对稻田土壤Cd活性的调控效应和机制，为Cd污染稻田土壤安全利用中水分优化管理和含铁钝化剂施用提供了科学依据. |
| 英文摘要 |
| The transformation of iron oxide forms in the process of soil water management in paddy fields has an important impact on soil cadmium (Cd) activity and accumulation in rice. The test soil for this experiment was purple paddy soil in southwest China contaminated with exogenously added Cd. Through indoor cultivation experiments, the effects of water management (continuous flooding, CW; alternating wet and dry, DW) combined with iron oxide application (goethite, G-Fe; iron powder, Fe) on the pH, redox state (Eh, pe+pH), iron oxide form conversion, and Cd bioavailability changes in Cd-contaminated soil were studied. Meanwhile, the coupling relationship between the transformation of iron oxide form and the evolution of soil Cd activity driven by water management were also analyzed. The results showed that DTPA-Cd content was decreased by 17.7%-39.2% after 93 days of flooding, indicating that CW could significantly reduce soil Cd bioavailability. CW combined with Fe or G-Fe application significantly enhanced the passivating effect on soil Cd. Among them, the DTPA-Cd content of G-Fe application was reduced by 24.3% compared with that of the CK after 14 d of flooding; thus, G-Fe was effective in short-term passivation. The reduction in DTPA-Cd content of Fe application was 39.2% after 93 d of flooding, so Fe was able to passivate soil Cd continuously. It was also found that the application of iron oxides under alternating wet and dry conditions had no passivating effect on soil Cd. Furthermore, based on correlation analysis, the formation of amorphous iron (Feo) (P<0.01) was verified as the main reason for the change in Cd bioavailability of Cd in the soil:firstly, the soil pH gradually declined to 7.4, and the soil was kept at reduction conditions under CW, which promoted the morphology transformation from the crystalline state (Fec) to Feo. This transformation subsequently pushed the Cd transformation from the exchangeable state to the iron-manganese combined state and thus resulted in the significant decrease in Cd bioavailability. Meanwhile, the content and proportion of Feo were also significantly increased by the application of CW combined with Fe or G-Fe, thus further enhancing its Cd passivating effect on the soil. This research provides a scientific basis for the optimal water management and the application of iron-containing passivation agent in the safe use of Cd-contaminated paddy soils. |
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