Additive Effect of Piriformospora Indica Fungus and Rhodococcus Erythropolis Bacteria on Bio-Remediation of Pyrene in a Pb-Polluted Soil Treated With Tire Rubber Ash

Background and purpose:: This research was conducted to evaluate the effect of Piriformospora indica fungus (P. indica) and Rhodococcus erythropolis (R. erythropolis) bacteria on bio-remediation of pyrene in a Pb-polluted soil that was treated with tire rubber ash. Method: Treatment consisted of applying tire rubber ash at the rates of 0 and 300 mg/kg soil, soil polluted with pyrene at the amount of 0 and 100 mg/kg soil, soil pollution with Pb (0, 400 and 800 mg/kg soil), and finally plant inoculated with P. indica fungus and R. erythropolis bacteria, and the plant used in this experiment was canola. After 60 days, plants were harvested and plant Pb and Zn concentration was measured using atomic absorption spectroscopy (AAS). The pyrene concentration in the soil samples were extracted by soxhlet using n-hexane and a 1:1 (v/v) dichloromethane during 24 h and measured according to the Besalatpour et al. (2011). The basal soil microbial respiration was measured as evolved CO2. Results: A significant increase (P=0.05) by 15.1% was observed in pyrene degradation in soil when plant inoculated with P. indica and R. erythropolis. However, soil pollution with Pb significantly decreased the pyrene degradation in the soil. At the same time, adding tire rubber ash to the soil significantly increased the plant biomass and pyrene degradation. Conclusion: Plant inoculation with P. indica and R. erythropolis had an additive effect on pyrene degrading (bio-remediation) in soil that is an important factor in environmental studies. However, soil pollution with heavy metals showed an adverse effect on it.