Biodegradation of Petroleum Hydrocarbons in Soil Microcosms by Indigenous Microbial Communities in Ubeji, Nigeria

Crude oil pollution remains a persistent environmental challenge in Ubeji, a suburb of the Niger Delta region of Nigeria located adjacent to the Warri Refining and Petrochemical Company (WRPC). Continuous contamination necessitates regular assessment and sustainable remediation strategies. This study evaluated petroleum hydrocarbon concentrations in crude oil–impacted soils from Ubeji and assessed the intrinsic biodegradation potential of autochthonous soil microorganisms under ex situ conditions. Petroleum hydrocarbon fractions were quantified using Gas Chromatography with Flame Ionization Detection (GC-FID). Contaminated soils were incubated for six months at ambient temperature without nutrient amendment to determine the natural attenuation capacity of native microbial communities. Initial polycyclic aromatic hydrocarbon (PAH) concentrations ranged from <0.001 mg/kg to 86 mg/kg. After six months of incubation, PAH levels decreased by over 90%, reaching <0.001 mg/kg to 2.75 mg/kg. Total aliphatic hydrocarbons (TAH) initially ranged from 3.86 mg/kg to 3662.11 mg/kg and were reduced to <0.001 mg/kg to 22.20 mg/kg, representing more than 95% degradation. Similarly, total petroleum hydrocarbons (TPH) declined by over 95%, from 3.83 mg/kg–3740.40 mg/kg to <0.001 mg/kg–24.42 mg/kg. The substantial reduction in petroleum hydrocarbon concentrations demonstrates that indigenous microorganisms in the Niger Delta wetlands possess significant intrinsic biodegradation capability under favourable abiotic conditions. These findings support the potential application of natural attenuation as a cost effective remediation strategy for crude oil contaminated soils in the region.