稀土工业区土壤中钍形态的植物可利用性评价

Evaluation of phytoavailability of thorium fractions in soil from rare earth industrial area

土壤中钍的生物可利用性与其对生态环境的危害密切相关。分别采用小麦盆栽培养实验和连续萃取方法研究(Triticum aestivumL.)对土壤中钍的吸收及根际土壤和原质土壤中钍形态差别。结果表明,根际土壤中钍的质量分数较原质土壤低,根际土壤和原质土壤中钍的形态分布存在一定差别,根际土壤中非残留态量较原质土壤中高。利用吸附了钍的高岭土、蒙脱土、碳酸钙、无定形氧化铁、无定形氧化锰和腐殖酸等作为小麦水培实验基质材料,并采用连续萃取方法对钍各形态的植物可利用性进行了考察。吸附材料中钍对小麦吸收的贡献指数由大到小的顺序为:高岭土、碳酸钙、腐殖酸、无定形氧化铁、无定形氧化锰、蒙脱土。由各模拟材料结合的优势钍形态,钍各形态的小麦可利用性由大到小的顺序为:离子交换态、碳酸盐结合态、有机质吸附态、无定形铁锰氢氧化物共沉淀态、晶形铁锰氢氧化物结合态。

Harm of thorium to environment is closely related to it＇s bioavailability in soil. The uptake of thorium by wheat （Triticum aestivum L.） and the differences of thorium fractions in rhizosphere soil and bulk soil were investigated by pot experiments of wheat and sequential extraction method, respectively. Result showed that the content of thorium in rhizosphere soil was lower than that in bulk soil, and thorium fractions in rhizosphere soil differed from that in bulk soil, moreover, the contents of non-residual fractions were higher in rhizosphere. After adsorbing thorium, kaolin, montmorillonite, calcium carbonate, amorphous ferric oxide, amorphous manganese oxide, humic acid were used as the culture meterials of water culture experiments, respectively, and the phytoavailability of thorium fractions bond with adsorption materials was investigated by sequential extraction method. The contribution of thorium adsorbed on materials to the wheat uptake of thorium was as follows： Kaolin 〉 calcium carbonate 〉 humic acid 〉 amorphous ferric oxide 〉 amorphous manganese oxide 〉 montmorillonite. According to the primary thorium fractions of each adsorption material, the sequence of phytoavailability of thorium fractions was exchangeable fraction 〉 fraction bound to carbonate 〉 adsorbed fraction 〉 fraction coprecipitated with amorphous ferric and manganese 〉 fraction bound to crystal ferric and manganese oxide.