Zhou Jiangming
The Agricultural Technique Popularization Centre of Jiangshan City, Jiangshan, 324100, Zhejiang, China.
Environ Sci Pollut Res Int. 2022 May;29(21):31363-31373. doi: 10.1007/s11356-021-18328-y. Epub 2022 Jan 10.
Continuous flooding has been widely used in paddy field to decrease the accumulation of heavy metal(loid)s by rice due to their decreased solubility and bioavailability of most heavy metal(loid)s under water flooding condition. A field experiment with six drainage treatments during grain-filling stage was performed to investigate the influence of different water flooding conditions on availability of cadmium (Cd), lead (Pb), chromium (Cr), arsenic (As), and mercury (Hg) and their accumulation by rice in alkaline paddy soil. The results showed at the end of experiment, the availability of Cd and Pb in soil with continuous flooding for above 25 days after full heading significantly decreased compared with draining immediately after full heading of rice. But some increase of the As availability in soil with different water regimes was observed at 15 days after beginning of experiment where the As availability was below its detection limit. Meanwhile, the concentrations of Cd and Cr both in rice grains and straws were decreased evidently with prolonged flooding at rice filling stage. The concentrations of Pb and Hg in grain were all below the detection limit, but increased in straw with draining 15 days later compared with draining immediately after full heading of rice. However, water regimes during grain-filling stage had little effect on As uptake by rice in alkaline paddy soil. Moreover, this study also discovered that organic matter may played a critical role in controlling availability of heavy metal(loid)s in alkaline soil. This work demonstrated that at alkaline paddy soil, maintaining water flooding until 5 days before harvest in rice grain-filling stage was an effective method to improve rice safety without decreasing yields in paddy field polluted with Cd, Cr, and As, but careful consideration is required for Pb and Hg.
由于在淹水条件下大多数重金属（类金属）的溶解度和生物有效性降低，持续淹水已被广泛应用于稻田，以减少水稻对重金属（类金属）的积累。进行了一项在灌浆期设置六种排水处理的田间试验，以研究不同淹水条件对碱性稻田土壤中镉（Cd）、铅（Pb）、铬（Cr）、砷（As）和汞（Hg）的有效性及其在水稻中的积累的影响。结果表明，在试验结束时，与水稻齐穗后立即排水相比，齐穗后持续淹水25天以上的土壤中Cd和Pb的有效性显著降低。但在试验开始15天时，观察到不同水分处理的土壤中As的有效性有所增加，而试验开始时As的有效性低于其检测限。同时，随着水稻灌浆期淹水时间延长，水稻籽粒和秸秆中Cd和Cr的含量均明显降低。籽粒中Pb和Hg的含量均低于检测限，但与水稻齐穗后立即排水相比，齐穗后15天排水的秸秆中Pb和Hg的含量增加。然而，灌浆期的水分处理对碱性稻田土壤中水稻吸收As的影响较小。此外，本研究还发现有机质可能在控制碱性土壤中重金属（类金属）的有效性方面起关键作用。这项工作表明，在碱性稻田土壤中，在水稻灌浆期保持淹水至收获前5天是提高水稻安全性且不降低产量的有效方法，该方法适用于受Cd、Cr和As污染的稻田，但对于Pb和Hg则需要谨慎考虑。
