Evaluating the efficiency of vetiver grass (Vetiverzizanioidesl. nash) in cleaning oil-contaminated soils in pilot scale

Phytoremediation is a novel technology which has been exploited recently to remove environmental pollution. In the study, for cleaning up of crude oil-contaminated soil, named Vetiver Grass )Vetiverzizanioides( was used. Vetiver is a tropical grass with high capacity to cope with different environmental conditions. Experiments were performed in a randomized complete block design with five treatments and three replications. The soil was artificially contaminated with crude oil at two levels of 3% and 6% and treated in the presence and absence of plant, along with control treatment during 16 months of experiment.In this study the TPH of the soil, rhizosphere microbial population (heterotrophic and hydrocarbon degrading bacteria) throughout experiment was monitored and plant growth and dry matter yield was measured at the end of the experiment.The results showed that soil contamination has no significant effect on vetiver plant growth and biomass and this species could thrive in high concentrations of oil contamination.TPH concentrations in treatments of 3% and 6%, decrease 27% and 20% respectively.Microbial population of hydrocarbon degrading and heterotrophic bacteria showed a significant increase compared to the unplanted soil. In the 3% contaminated soil, a noticeable increase of bacterial population was observed in the rhizosphere (81% and 79% for oil-degrading and heterotrophic bacteria, respectively) in comparison with unplanted trial, while in the soil with 6% contamination, stimulating effect of plant was somehow lower (65%and 59% for oil-degrading and heterotrophic bacteria, respectively).Application of vetiverplants could be promising for remediation of soils contaminated with petroleum due to resistance toward high concentrations of oil pollution and potential in the activation of soil degrading microorganisms used.