Evaluation of the Effectiveness of Bioaugmentation-Assisted Phytoremediation of Soils Contaminated with Petroleum Hydrocarbons Using Echinacea purpurea

Abstract

Phytoremediation supported by bioaugmentation is a promising method considered for cleaning up areas polluted with petroleum hydrocarbons. In this study, phytoremediation was carried out using Echinacea purpurea as a phytoremediant on two types of soil: Soil DW—aged soil taken from an excavation pit, Soil OS—soil taken from an oil spill area. The tests for each soil were carried out in six test systems (non-inoculation, inoculation with the B1 microbial consortium, inoculation with the B2 microbial consortium, inoculation with the B1 microbial consortium with the addition of γ-PGA (γ-poly glutamic acid), inoculation with the B2 microbial consortium with the addition of γ-PGA and inoculation with the γ-PGA solution) for 6 months. The effectiveness of the remediation treatments used was assessed based on chromatographic analyses of soil and plant material (roots, shoots) and toxicological analyses using four types of toxicological tests (PhytotoxkitTM (MicroBioTests Inc., Gent, Belgium), OstracodtoxkitTM (MicroBioTests Inc., Gent, Belgium), Microtox® Solid Phase Test (Modern Water Inc., New Castle, DE, USA), MARA (NCIMB Ltd., Aberdeen, UK)). The research conducted showed that the most effective method of bioremediation of soils contaminated with petroleum hydrocarbons was phytoremediation supported by bioaugmentation with the microbial consortium B2 with γ-PGA, which allowed for reducing the concentration of total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs) in the tested soils by 53.98% and 49.54% (Soil DW-5) and 60.47% and 37.55% (Soil OS-5), respectively. In turn, the lowest bioremediation efficiency was recorded in non-inoculated systems, for which the concentration of TPHs and PAHs at the end of the study decreased by 18.40% and 16.14% (Soil DW-1) and 21.87% and 18.20% (Soil OS-1), respectively. The results of toxicological analyses confirmed the relationship between the concentration of TPHs and PAHs in the soil and its toxicity level.