Combined phytoremediation effect of several plants in PCBs contaminated farmland soils.

A field microzone experiment was carried out to study the co-remediation effect of PCBs contaminatedfarmland soils under different planting models for using three plant species, alfalfa( Medicago sativa L), Elsholtziasplendens and Sedum plumbizincicola. The results indicated that mixed croppings of alfalfa with Elsholtzia splendens orSedum plumbizincicola could enhance PCBs removal in soils compared to the monoculture with alfalfa. About 43.0% ofPCBs were removed from the soils in mixed cropping of alfalfa and Elsholtzia splendens at the end of the 120dexperiment, and 47.8% in mixed cropping of three plants. The mixed croppings of alfalfa with Elsholtzia splendens orSedum plumbizincicola could increase the total biomass of plants, facilitate the uptake and accumulation of the PCBs inplants. Analysis of PCBs composition showed that the planted treatments could decrease the concentration of lowerchlorinated PCBs in soils, and multi-species phytoremediation could improve the transformation of higher chlorinatedPCBs into lower chlorinated PCBs. The mixed croppings of alfalfa with Elsholtzia splendens or Sedum plumbizincicolashow a good potential in the remediation of PCBs contaminated farmland soils.