Comparative Effectiveness of Nitrogen Sources for Nutrient Amendment in Bioremediation of Petroleum-Contaminated Soils in Nigeria’s Niger Delta Region

Abstract

Oil spills are a recurrent environmental challenge in Nigeria’s Niger Delta, leading to significant ecological and socio-economic impacts. Bioremediation, particularly nutrient amendment via biostimulation, has emerged as a viable approach for enhancing the natural degradation of petroleum hydrocarbons by indigenous microbes. This study investigates the comparative effectiveness of three nitrogen sources-ammonium (NH₄⁺), nitrate (NO₃⁻), and organic nitrogen-on the degradation of petroleum hydrocarbons in oil-contaminated soils. Using a mesocosm experimental setup with composite soil samples from three communities (Batan, Ajuju, and Umusia), treatments were applied across varying oil concentrations. Results showed that nutrient amendment generally increased total nitrogen (%), enhanced microbial population, and significantly reduced both total petroleum hydrocarbon (TPH) and polyaromatic hydrocarbon (PAH) levels. Ammonium-nitrogen was more effective in stimulating hydrocarbon degradation than nitrate, while organic nitrogen produced the highest microbial proliferation. Regression analysis revealed a strong positive correlation between nitrogen concentration and microbial population growth (r = 0.95). These findings support nitrogen-based biostimulation as a practical, low-impact strategy for accelerating oil spill remediation in tropical environments like the Niger Delta.