The effects of simultaneous application of plant growth regulators and bioaugmentation on improvement of phytoremediation of pyrene contaminated soils

Polycyclic aromatic hydrocarbons (PAHs) refer to a wide group of soil contaminants whose presence in the environment is a cause of concern. The present study aimed to evaluate the effects of Indole Acetic Acid (IAA) and Pseudomonas aeruginosa on the phytoremediation activities of sorghum bicolor and increase in pyrene removal efficiency in the soil. The initial concentration of pyrene was 150 and 300 mg kg−1 in this experiment. The treatments included unplanted soil (T0), planted soil with sorghum (T1), planted soil with application of IAA (T2), planted soil with application of Pseudomonas sp. (T3), and planted soil with simultaneous application of IAA and Pseudomonas sp. (T4). The pyrene removal rate in the soil was measured every 30 days. Moreover, plant biomass and soil bacteria were measured after 90 days. The results showed that pyrene removal rate significantly increased in the planted treatments compared to the unplanted ones. After 90 days, at the initial concentration of 150-300 mg kg−1, pyrene removal efficiency was 52-92% in T1-T4 and 35-47% in the unplanted treatment (T0). Application of IAA and Pseudomonas sp. significantly increased plant biomass, soil bacteria, and pyrene removal rate in T2, T3, and T4 compared to T1. Therefore, application of IAA in the planted treatments with sorghum could have a significant effect on increasing the removal efficiency of pyrene.