Remediation of anthracene in mycorrhizospheric soil using ryegrass

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

Effect of soil contaminated by diesel oil on the germination of seeds and the growth of Schinus terebinthifolius Raddi (Anacardiaceae) Seedlings

The effect of soil polluted by diesel oil on the germination of seeds and the growth of Schinus terebinthifolius Raddi seedlings was analyzed at different times after contamination of the soil. The experiments were conducted under greenhouse conditions, with four treatments and five repetitions. The four treatments included: soil contaminated 30 (T30), 90 (T90) or 180 (T180) days before planting as well as a non-polluted soil (T0) (control). Soil saturated to 50% of its maximum retention capacity (MRC) was contaminated with diesel oil at a rate of 92.4 mL per kg. The germination rate and germination speed index (GSI) were significantly affected only in T30. The development of the plants was affected significantly in all the treatments, with reductions of biomass and eophyll area. It could be concluded that diesel oil significantly affected the germination, GSI and seedling growth of S. terebinthifolius, but the toxic effect decreased over the time