电镀污染区植物对复合重金属的富集、转移和对污染土壤的修复潜力

采用野外采样室内分析方法,对重庆市3个电镀厂污染区自然定居的23种优势植物和相应土壤中Cu、Zn、Cr和Ni 4种重金属含量进行测定,揭示了优势植物对复合污染重金属的富集和转移特征。结果表明,电镀污染区土壤中Cu、Zn、Cr和Ni平均含量分别为560.0、722.6、1 364.3和735.7 mg·kg-1,分别为GB 15618—1995《土壤环境质量标准》中三级标准限值的1.40、1.45、3.90和3.68倍。植物对重金属的吸收、富集和转移特性因植物种类、植株部位、污染地及重金属种类的不同而不同,污染地植物吸收的重金属富集滞留在根部较多,扁穗牛鞭草(Hemarthria compressa)和野薄荷(Mentha haplocalyx)表现出超富集Cr的潜力,其地上部分Cr平均含量分别为1 559.2和1 914.6 mg.kg-1,生物转运系数分别为1.29和1.58,生物富集系数分别为1.58和1.79,其他植物地上部分Cr含量超过正常植物百倍以上的有14种,平均富集量为376.4 mg·kg-1,变化范围为121.2～694.3 mg·kg-1,地上部分Ni含量超过正常植物百倍以上的有8种,平均富集量为344.1 mg·kg-1,变化范围为220.3～532.1 mg·kg-1。它们是修复电镀重金属Cr和Ni复合污染土壤的理想植物。

Potentials of 23 Plants Growing in Contaminated Soils Nearby Electroplating Plants for Accumulating and Translocating Heavy Metals and Remedying the Soils

Samples of soils and plants were collected from 3 electroplating plant contaminated areas in Chongqing for analysis in laboratory to investigate concentrations of chromium(Cr),nickel(Ni),zinc(Zn) and copper(Cu) therein and to further explore characteristics of the 23 dominant plants accumulating and translocating heavy metals.Results show that in the soils,the average concentration of Cu,Zn,Cr,and Ni was 560.0,722.6,1 364.3 and 735.7 mg·kg-1,respectively,and about 1.40,1.45,3.90,and 3.68 times,respectively,the threshold value in Grade Ⅲ of the "Standard for Soil Environmental Quality"(GB 15618-1995).The characteristics of plants absorbing,accumulating and transferring heavy metals varied with species and parts of plant,location of contaminated area and kind of metal.Most of the plants in these areas had heavy metals accumulated in the roots.Only Hemarthria compressa and Mentha haplocalyx displayed their characteristics of being Cr hyperaccumulators,with Cr concentration in shoots reaching 1 559.2 and 1 914.6 mg·kg-1,respectively,on average,BTC(biological transfer coefficient) 1.29 and 1.58,respectively,and BAC(biological accumulating coefficient) 1.58 and 1.79,respectively.Besides the two,there were 14 other plants whose Cr concentrations in shoots were over 100 times higher than those of ordinary plant species,with Cr concentrations ranging from 121.2 to 694.3 mg·kg-1 and averaging 376.4 mg·kg-1,and 8 others whose Ni concentrations in shoots were over 100 times higher than those of ordinary plant species,with Ni concentrations ranging from 220.3 to 532.1 mg·kg-1 and averaging 344.1 mg·kg-1.In summary,the findings indicate that these plants are ideal species of plants for phytoremedying soils polluted with multi-heavy metals from electroplating plants.