磷和硅对土壤-烟草系统中铅迁移的影响

Effect of Phosphorus and Silicon on Migration of Pb in Soil-Tobacco System

为探究降低土壤铅活性与烟叶铅含量的有效措施,采用盆栽法研究施磷、施硅及磷硅配施对铅在土壤-烟草系统中迁移的影响。结果表明,在非根际土壤中,施磷使土壤可交换态和碳酸盐结合态铅向铁锰氧化物结合态和残渣态铅转化,施硅使土壤可交换态铅向铁锰氧化物结合态铅转化,磷硅配施使土壤可交换态铅向铁锰氧化物结合态、有机态及残渣态铅转化。与CK相比,施磷、施硅及磷硅配施使根际土壤可交换态铅含量分别降低46.05%、14.24%和48.76%,使烟草铅总吸收量分别降低44.02%、44.04%和65.65%,使烟叶铅含量分别降低63.06%、60.37%和83.24%。施磷可通过降低土壤中铅向根部迁移的移动指数(IM,土-根)和根部向茎部迁移的移动指数(IM,根-茎)来抑制土壤中铅向叶部的迁移;施硅及磷硅配施可通过降低IM,土-根、IM,根-茎和茎部铅向叶部迁移的移动指数(IM,茎-叶)来抑制土壤中铅向叶部的迁移。施磷和施硅是降低烟叶铅含量的有效措施,且配施效果更佳。

A pot experiment was conducted to study effects of phosphorus and silicon on migration of Pb in the soil-tobacco system and to explore approaches to reducing Pb activity in soil and Pb concentration in tobacco leaf. Results show that phosphorus application made exchangeable and carbonate-bound Pb transformed into Fe-Mn oxide-bound and residual Pb in non-rhizospheric soil and silicon application made exchangeable Pb transformed into Fe-Mn oxide-bound Pb. Combined application of phosphorus and silicon made exchangeable Pb transformed into Fe-Mn oxide-bound,organic-bound and residual Pb. Though tobacco roots tend to activate Pb in the rhizosphere,the application of P,Si and P + Si in combination reduced the content of exchangeable Pb in the rhizosphere by 46. 05%,14. 24%,and 48. 76%,respectively,and hence reduction of Pb uptake of tobacco by 44. 02%,44. 04%,and 65. 65%,respectively,thus lowering the concentration of Pb in tobacco leaf by 63. 06%,60. 37%,and 83. 24%,respectively. P application restricted the transportation of Pb from soil to tobacco leaf by reducing the mobility index of Pb from soil to root(IM,soil- root) and that from root to stem(IM,root- stem)as well. Si application and combined P and Si application restricted the transportation of Pb from soil to tobacco leaf by reducing IM,soil- root,IM,root- stemand IM,stem- leaf,(the mobility index of Pb from stem to leaf). Application of P and Si is an effective measure to reduce Pb concentration in tobacco leaf,and combined application of P and Si is more effective than the application of merely P or Si.