Biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) by Trichoderma harzianum in Soil Mesocosms near a Thermoelectric Power Plant, Azuay, Ecuador

Biodegradation is emerging as a promising and sustainable strategy for the removal of polycyclic aromatic hydrocarbons (PAHs) from soil. This approach integrates various strategies, such as bioaugmentation and biostimulation of microbial communities with tolerance and biodegradation capabilities. This study evaluated the biodegradation potential of the fungal isolate Trichoderma harzianum (strain UPS-Y1) in mesocosms of soil contaminated with polycyclic aromatic hydrocarbons present in bunker diesel fuel, which is widely used in thermoelectric power plants. The experimental monitoring was conducted by quantifying these compounds at 30, 60, and 90 days, with three replicates for both the inoculated treatments and the non-inoculated controls at each sampling time. The controls were subjected to the same biostimulation and management conditions but without Trichoderma harzianum inoculation. Statistical analyses, including the Friedman test and multivariate techniques, showed temporal changes in PAH concentrations and differences between the inoculated and non-inoculated mesocosms. At 60 days, the concentrations of several compounds, such as naphthalene, acenaphthene, fluorene, fluoranthene, benzo[a]pyrene, benzo[g,h,i]perylene, and indene, decreased to levels below the analytical detection limit. Following this pattern, at the end of 90 days, 14 of the analyzed compounds showed concentrations below the analytical detection limit. These findings indicate that T. harzianum bioaugmentation was associated with enhanced PAH reduction under the biostimulation conditions applied in this study. However, because abiotic controls were not included, the observed reductions cannot be attributed exclusively to fungal activity.