Bentonite addition to a PCB-contaminated sandy soil improved the growth and phytoremediation efficiency of Zea mays L. and Alternanthera sessilis L.
In this study, the removal of 17 selected PCBi congeners was assessed in a transformer oil-contaminated soil amended with bentonite clay powder applied at the three levels of 0, 2, and 4% and cultivated by Zea mays L. or Alternanthera sessilis L. in a pot experiment. Results showed that Z. mays and A. sessilis were able to reduce the residual concentrations of the PCBi congeners in the contaminated soil significantly (p < 0.05). The average reductions in the ƩPCBi due to Z. mays or A. sessilis cultivations were 34.3 and 21.4%, respectively, depending on initial soil ƩPCBi loading and plant growth period. Moreover, addition of bentonite led to significant (p < 0.05) enhancements in plant growth and dissipation of residual soil PCBi congeners under Z. mays and A. sessilis cultivations. Addition of 4% bentonite to the soil was found to have the greatest positive impact on PCBi removal so that average PCBi dissipations in the soil were 56.1 and 51.8% after growing Z. mays and A. sessilis, respectively. It might be concluded that the combined phytoremediation and bentonite addition is an effective technique for removing PCBi and remediating transformer oil-contaminated coarse-textured soils.