Fertilizer-assisted Bioremediation of Sandy and Silty Clay Soils contaminated with Crude Oil

Crude oil contamination of farmlands and rivers has been a major concern in Nigeria, especially in places like Ogoni land in Rivers State and some other oil producing states. It has severely impacted on the economic and health status of people in that region. It is important to find ways to ameliorate the harmful effects of crude oil contamination on both terrestrial and aquatic lives. In this study, we investigated the bioremediation profile of sandy and silty clay soils contaminated with crude oil. Contaminated soils were treated with inorganic fertilizer (NPK 15:15:15) and urea to improve the density of soil microbes and enzymes. The total petroleum hydrocarbon (TPH), total heterotrophic bacteria (THB), total hydrocarbon utilizing bacteria (THUB), total heterotrophic fungi (THF), total hydrocarbon utilizing fungi (THUF), and the activities of soil enzymes such as laccase, peroxidase, lipase, and catalase were investigated. The results indicated that treatment of crude oil contaminated soils with NPK and urea increased the activities of soil enzymes and enhanced total soil microbial load that play active roles in biodegradation of petroleum products, thereby suggesting that NPK and urea treatments of soils have the potential of decreasing crude oil contamination and remediating contaminated soils. Furthermore, this study showed that NPK and urea decreased the total petroleum hydrocarbon (TPH) values of both sandy (92.5%) and silty clay (80.5%) soils. The findings from this study, suggest that NPK and urea application to contaminated soils could serve as beneficial remediation agents for quick mitigation of the hazardous effects of crude oil contamination on farmlands.