硅质钝化材料与促生菌剂组合施用对水稻累积镉效应研究

Effect of Integrative Remediation Measures of Soil Passivation and Growth-promoting Microbial Inoculum on Cd Accumulation in Rice

在镉污染土壤的钝化修复应用中,由于钝化材料一般不具有特异选择性,在钝化重金属的同时往往会同步钝化土壤中的养分,从而导致作物的生长受到抑制。基于课题组前期研发的对Cd具有强吸附能力的改性钼矿和改性泥岩等两种硅质材料和一种兼具解磷、促生长作用的促生芽孢杆菌菌剂在田间试验条件下验证其降低水稻累积Cd效应的影响,并对钝化材料和功能菌剂的组合应用效果进行评价。结果表明,未添加促生菌剂的处理下土壤有效磷含量与对照组之间无显著差异,而单施促生菌剂及其与改性泥岩组合处理均显著增加了土壤的有效磷含量,增幅分别为21.6%和37.8%。各修复处理对稻米产量的增产效果排序为:改性泥岩+促生菌剂>促生菌剂>改性泥岩>改性钼矿,增产幅度为0.5%-8.8%,其中改性泥岩+促生菌剂的增产效果达到显著水平,而改性钼矿+促生菌剂未表现出增产效应。各修复处理均显著地降低了稻米中Cd含量,降低效果排序为:改性钼矿>改性钼矿+促生菌剂>改性泥岩>改性泥岩+促生菌剂>促生菌剂,降低幅度为35.3%-65.0%。除单独施用促生菌剂处理外,其他处理实施后水稻籽粒Cd含量均低于国家食品安全标准限量值(0.2 mg·kg^-1)。采用的改性钼矿的作用机理主要是通过降低Cd从土壤向根系的迁移,而改性泥岩的作用机理处理降低Cd从土壤向根系的迁移外,还会通过增加Cd在茎叶中的滞留效应达到降低籽粒Cd累积的效果。综合组合处理对土壤养分的活化和对水稻的促生效果,在该研究试验用地上,具有弱碱性的改性泥岩与促生菌剂的技术集成是一种兼具促生和降低Cd在水稻中累积效应的Cd污染稻田安全利用技术模式。

In most applications of passivation remediation of cadmium-contaminated soils, soil nutrients would be simultaneously immobilized since generally-used passivants don’t have specific selectivity on heavy metals, which may have a negative effect on plant growth. Two siliceous materials, modified molybdenum ore and modified mudstone, which were previous developed by our group, were employed in this study, as well as a growth-promoting Bacillus inoculum. Field studies were conducted to investigate the effect of single/combined remediation measures on Cd accumulation in rice grain. The results indicated that there was no significant difference in soil available phosphorus content (Olsen-P) between the control group and the treatments without Bacillus inoculum. Treatments ‘Bacillus inoculum’ and ‘Bacillus inoculum+Modified mudstone’ significantly increased soil Olsen-P by 21.6% and 37.8%, respectively. The order of the effect of different remediation treatments on rice yield was: Modified mudstone+Bacillus inoculum>Bacillus inoculum>Modified mudstone>Modified molybdenum ore. The yield-increasing range was 0.5%-8.8%. Among them, the yield-increasing effect of ‘modified mudstone+Bacillus inoculum’ reached a significant level, while no significant effect was found under the treatment of modified molybdenum ore+Bacillus inoculum. Cd accumulation in rice grain were significantly reduced under all treatments. The order of reduction effect was: modified molybdenum ore>modified molybdenum ore+Bacillus inoculum>modified mudstone>modified mudstone+Bacillus inoculum>Bacillus inoculum. The decrease range were 35.3%-65.0%. The Cd content in rice grains was lower than the national food safety standard limit (0.2 mg·kg^-1) under all treatments except for ‘Bacillus inoculum’. In this study, modified molybdenum ore may reduce Cd in rice grain through inhibiting effect of Cd migrate from soil to rice root, while modified mudstone may reduce the accumulation of Cd by increasing the retention effect of Cd in rice shoot (stems and leaves). By comprehensive consideration of remediation and growth promoting effects, an integrative technique of alkalescent modified mudstone and Bacillus inoculum is an effective passivation method and suitable for extensive application in Pearl River Delta.