复配钝化剂对稻田重金属有效性及其水稻吸收的影响

针对红壤稻米中重金属Cd超标的问题，通过筛选钝化剂并将其复配用于大田实验，以研究复配钝化剂对土壤有效态重金属(Cd、Pb和Cu)及水稻吸收重金属的影响及其作用机理。室内筛选实验表明，在11种无机和有机钝化剂中，海泡石、生石灰和聚丙烯酰胺对土壤重金属钝化效果较好，使有效态Cd、Pb和Cu分别降低了32.4% ~ 89.2%、19.5% ~ 99.1%和49.4% ~ 92.4%，并将它们确定为复配钝化剂的成分。大田实验结果表明，生石灰、聚丙烯酰胺和海泡石复配对土壤中重金属钝化效果最佳，使有效态Cd、Pb和Cu分别降低了28.6%、20.2%和23.5%(p<0.05)，其钝化机制为离子交换和络合作用。而且，该复配钝化剂对土壤化学性质影响最小。复配钝化剂使稻米中Cd的质量分数降低了21.7% ~ 93.1%(p<0.05)。另外，复配钝化剂对土壤微生物丰度和多样性没有显著影响。考虑到土壤的安全性和稳定性，推荐将生石灰、聚丙烯酰胺和海泡石复配钝化剂用于降低红壤稻米对Cd的吸收以确保粮食安全生产。本研究结果可为重金属污染红壤稻田的安全利用提供参考。

Effects of combined passivators on the availability of heavy metals in red paddy soil and their uptake by rice

To solve the problem of Cd in rice over the food-safe standard, the combined passivators were selected and used in field experiments to explore the effects of the combined passivators on the available heavy metals (Cd, Pb and Cu) in soil and their uptake by rice in red paddy soil. Sepiolite, quicklime and polyacrylamide were used as the components of the combined passivators in field experiment, because laboratory screening results showed that they decreased available Cd, Pb and Cu by 32.4%~89.2%, 19.5%~99.1% and 49.4%~92.4%, respectively. Field experiment results showed that the combination of quicklime, polyacrylamide and sepiolite had the best passivation effect on heavy metals in soil, decreasing the concentrations of available Cd, Pb and Cu by 28.6%, 20.2% and 23.5%, respectively (p<0.05). The passivation mechanism of this combined passivator was ion exchange and complexation. This combine passivator had less impact on soil chemical properties than other combined passivators. The combined passivators decreased the concentration of Cd in rice by 21.7%~93.1% as compared with the control (p<0.05). In addition, the combined passivators had no significant effect on the abundance and diversity of soil microorganisms. Considering the safety and stability of soil, the combination of quicklime, polyacrylamide and sepiolite was the primary recommendation to decrease Cd content of rice in red paddy soil. The research results can provide a basis for the safe utilization of heavy metals-contaminated red paddy soil.