硅对土壤-烟草系统中铅迁移及形态分布的影响

通过盆栽试验，以烟草为对象，研究了硅对土壤 烟草系统中铅的迁移以及土壤、烟草中铅形态分布的影响.结果表明： 施硅使非根际土壤可交换态铅向铁锰氧化物结合态转化，使根际土中交换态铅向铁锰氧化物结合态和残渣态转化，降低了土壤中铅的植物有效性与迁移性.施硅显著提高了烟草根部和叶部的生物量，显著降低了烟草铅的总吸收量和烟草各器官的铅含量，其中烟草铅的总吸收量降低了6.5%～44.0%，烟叶铅含量降低了3.1%～60.4%.施硅使烟草根、茎和叶中乙醇提取态、去离子水提取态和氯化钠提取态向盐酸提取态和残渣态转化，降低了烟草体内铅的毒性与迁移性.土壤-烟草系统中土壤向烟草根部的移动指数和根部向茎部的移动指数随施硅量的增加而降低，烟草茎部向叶部的移动指数随着施硅量的增加呈先增高后降低的趋势.硅通过降低土壤铅有效性、缓解铅对烟草的毒害、改变烟草体内铅的形态分布，进而抑制土壤中铅向烟草叶部的迁移，降低烟叶中的铅含量.施硅是降低土壤铅的迁移性及烟叶铅含量的有效措施.

Effect of silicon on translocation and morphology distribution of lead in soil tobacco system.

Taking tobacco as test material, a pot experiment was conducted to study the effect of silicon on translocation of lead (Pb) form soil to tobacco in order to explore effective measures for reducing Pb concentration in tobacco leaf. The results showed that silicon application promoted the transformation of exchangeable Pb into Fe-Mn oxide-bound Pb in non rhizospheric soil, and into Fe-Mn oxide-bound Pb and residual Pb in rhizospheric soil, which decreased the availability and mobility of Pb in the soil. Silicon application significantly reduced the Pb uptake of tobacco, with the content of Pb being decreased by 6.5% to 44.0% in tobacco, and 3.1% to 60.4% in leaf. Silicon application promoted the transformation of ethanol extractable, H₂O extractable Pb and NaCl extractable Pb into HCl extractable Pb and residual Pb in root, stem and leaf of tobacco, which reduced the toxicity and mobility of Pb in tobacco. Silicon restricted the transportation of Pb from soil to tobacco leaf by reducing the mobility index of Pb from soil to root and the mobility index of Pb from root to stem in soil tobacco system. Meanwhile, the mobility index of Pb from stem to leaf in soil-tobacco system showed a rising and falling trend with the increase of Pb application. Silicon inhibited the Pb migration from soil to tobacco leaf by reducing availability of Pb, mitigating toxicity of Pb to tobacco, and changing the distribution of Pb forms in tobacco, consequently reducing Pb concentration of tobacco leaf. These results demonstrated silicon application could be effective in reducing translocation of Pb from soil to tobacco.