Abstract

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 (Neotyphodium coenophialum 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.