Remediation of anthracene in mycorrhizospheric soil using ryegrass

Abstract

Rhizosphere bioremediation has become an effective technique that uses green plants to enhance biodegradation of persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), pesticides and radionuclides. Polycyclic aromatic hydrocarbons, due to their hydrophobic nature were found to be retained in the soil. Plants could be grown at the PAH contaminated sites to stimulate the biodegradation in the rhizosphere. In the present study, biodegradation of anthracene was studied using ryegrass in mycorrhizosphere soil by laboratory scale pot culture experiments. Ryegrass (Lolium multiflorum) was grown in pots containing soil contaminated with various levels of anthracene. Soil and plants from treated pots were sampled after 15, 30, 45 and 60 days and compared with uncontaminated planted pots. In the mycorrhizosphere, the concentrations of anthracene in the soil were found to be 5.2, 7.88, 15.43, 33.23 and 41.5 mg/kg at the 15 days harvest which further decreased to 0.31, 0.45, 0.89, 1.89 and 2.43 mg/kg over a period of 60 days when exposed to the initial concentrations of 10, 25, 50, 75 and 100 mg/kg amended in soil, respectively. Plant shoot and root dry biomass were observed to be significantly reduced at higher anthracene concentrations (75 and 100 mg/kg) whereas low concentrations had no distinct effect on plant biomass (p<0.05). The increase in the microbial counts was also monitored and quantified along the degradation of the anthracene in the soil. The findings of this research show that there is rapid degradation of anthracene under the influence of ryegrass mycorrhizosphere.

Key words: Rhizosphere bioremediation, Lolium multiflorum, arbuscular mycorrhizal fungi, PAHs.