生物炭与硅酸钠复合施加抑制水稻对土壤铅吸收富集的机制研究

The combinations of biochar and sodium silicate reduced the accumulation and transfer of Pb in soil-rice system

将水稻秸秆生物炭(RB)、玉米秸秆生物炭(MB)分别与硅酸钠(G)复合施加到从矿区周边采集的铅(Pb)污染农田土壤,通过盆栽试验,比较分析了Pb在土壤-水稻系统各部位中的迁移和累积情况,探讨了生物炭与硅酸钠复合施加抑制水稻对Pb吸收转运的机制.结果表明,与对照组相比,生物炭与硅酸钠复合施加(RBG和MBG)使糙米Pb含量显著降低71.0%~75.6%,且比生物炭或硅酸钠单一施加时的降幅更大.其主要机制为:①生物炭与硅酸钠复合施加提高了土壤pH和有机质含量,促进了土壤对Pb的固定,从而使土壤Pb从弱酸提取态向可氧化态Pb转化,在成熟期RBG和MBG处理分别使CaCl_(2)溶液浸提的土壤有效Pb含量降低54.3%和60.0%.②生物炭与硅酸钠复合施加降低了DTPA溶液浸提的土壤有效态Fe含量,减少了根表铁膜的数量(DCB-Fe),而且根系Pb含量与DCB-Fe含量之间呈显著正相关关系,推测生物炭与硅酸钠复合施加使根表用于存储Pb的铁膜减少,从而降低Pb进入根系的几率.③生物炭与硅酸钠复合施加显著降低了分蘖期TF_(根-叶)和成熟期TF_(土-根)、TF_(茎-糙米)、TF_(叶-糙米)(p<0.05),阻碍Pb在糙米中累积.此外,生物炭与硅酸钠复合施加显著提高了稻谷质量(p<0.05).因此,生物炭与硅酸钠复合施加可用于修复铅污染稻田土壤.

To explore the mechanism of the combine application of biochar and sodium silicate to inhibit the transfer of lead(Pb)in soil-rice system,the rice straw biochar(RB)and corn straw biochar(MB)combined with sodium silicate(G)were respectively applied to the Pb-polluted soils,which used in the pot experiment was collected from a field near the Pb-Zn mining area.The results showed that,when compared to the control,the combinations of biochar and sodium silicate significantly reduced the content of Pb in brown rice by 71.0%to 75.6%,which was more pronounced than that of the single application of biochar or sodium silicate.This might be explained by the following mechanisms.①The combination of biochar and sodium silicate increased the soil pH and organic matter content,promoted Pb in soil transfer from the weak acid extractable fraction to oxidizable fraction,and resulted in a reduction of soil available Pb concentration extracted by 0.1 mol·L^(-1)CaCl_(2)solution by 54.3%and 60.0%under RBG and MBG treatments,respectively.②The combined application of biochar and sodium silicate decreased the concentration of soil available Fe and the amount of iron plaque on root surface(DCB-Fe).And there is a significant positive relationship was observed between the Pb content in roots and the DCB-Fe.It might be speculated that the combined application of biochar and sodium silicate reduced the iron plaque used to store Pb on the root surface,thereby reducing the probability of Pb uptake by roots.③The combination of biochar and sodium silicate,hinder the rice plant transport of Pb to restricts its accumulation toward brown tice,reduced the TF_(root-leaf) at tillering stage,TF_(soil-root),TF_(stem-rice),TF_(leaf-rice) at maturity stage.In addition,the combination of biochar and sodium silicate can lead to significantly increased the weight of rice(p<0.05).This study revealed that the combined application of biochar and sodium silicate could be effective in remediation of Pb contaminated paddy soil.