Effect of Bentonite on phytoremediation of selected PCBs congeners from a transformer oil contaminated soil

Bioremediation technique for the removal of soil polychlorinated biphenyls (PCBs) contamination has been proven by many researchers, however no comprehensive studies on effect of bentonite to improve phytoremediation of PCBs was carried out. In this study, the removal of selected PCBs congeners was assessed in a transformer oil contaminated soil. Bentonite powder was applied to the soil at the rates: 0, 2 and 4 %. Maize (Zea mays L.) were planted in pots. Controls for each treatment were also included in the experiment. Treatments were arranged in a factorial manner in a completely randomized design with three replicates. Plants were harvested after 35 and 70 days. Under planting of maize, concentration of residual PCBs has been decreased significantly with addition of bentonite. Bentonte (4%) increase the average PCBs removal 20.95% in pot experiment after 70 days. Based on the results; initial soil PCBs concentration, and bentonite level could be effective on removal of PCBs from the transformer oil contaminated soil. Effect of bentonite on reduction of residual soil PCBs can be attributed to positive effect on plant growth. Kátai et al. (2008) demonstrated positive effect of bentonite on bacterial population. It has been found that the addition of adequate amount of clay to sandy soil can greatly improve its agricultural value. Bentonites possess high cation-exchange capacities and surface area. These special properties make them perfect materials to carry out combinations of any chemical, physical and biological remediation (Huang et al., 2013). The importance of plants in ensuring that contaminants are removed from soil is illustrated by Leigh et al. (2002). The results suggest that combined application of rhizostimulation and bentonite addition is an effective technique to remove PCBs and remediate transformer oil-contaminated soils.