Phytoremediation of an aged petroleum contaminated soil using endophyte infected and non-infected grasses

Phytoremediation is a promising technique for cleaning petroleum contaminated soils. In this study, the effects of two grass species (Festuca arundinacea Schreb. and Festuca pratensis Huds.), infected (E+) and non-infected (E−) by endophytic fungi (Neotyphodiumcoenophialum and Neotyphodium uncinatum, respectively) on the degradation of petroleum hydrocarbons in an aged petroleum contaminated soil was investigated. Plants were grown in the soil for 7 months and unplanted soil considered as control. At the end of the experiment, total and oil-degrading bacteria, dehydrogenase activity, water-soluble phenols, total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) contents were measured in the soil. The results demonstrated that E+ plants contained more root and shoot biomass than E− plants and created higher levels of water-soluble phenols and dehydrogenase activity in the soil, while there was no significant difference in bacterial counts of planted soils. Planting stimulated total and oil-degrading bacterial numbers, dehydrogenase activity and the soil content of water-soluble phenols. Regardless of endophyte infection, PAH and TPH removal in the rhizosphere of plants were 80–84 and 64–72% respectively, whereas the removals in controls were 56 and 31%, respectively. It was revealed that TPHs in retention time range of n-alkanes with C10–C25 chain lengths and TPH were more degraded in the rhizosphere of E+ plants compared to E− ones. Thus, grasses infected with endophytic fungi could be more efficient for removal of TPH from oil-contaminated soils.