Effect of Asphalt contamination on soil Microbial activity and diversity in soils of Uyo Akwa Ibom State

This study assessed the effect of asphalt contamination on soil microbial activity, diversity, and enzymatic function in Uyo and Oron, Akwa Ibom State, Nigeria. Soil samples were collected from three asphalt-contaminated sites — Amitec Asphalt Plant in Oron, Hensec Integrated Services, and Base Engineering in Uyo — and one uncontaminated control site, at 0–20 cm depth. Microbiological analysis included enumeration of Total Heterotrophic Bacteria Count, Total Fungi Count, and Actinomycetes Count, while soil enzyme activities including dehydrogenase, phosphatase, and cellulase were also determined. Results showed that asphalt contamination significantly altered soil parameters, with pH decreasing, organic carbon increasing, electrical conductivity increasing, and available phosphorus reducing. Microbial populations showed a general decline in contaminated soils compared to the control. Hydrocarbon-degrading microbial strains including Pseudomonas aeruginosa, Bacillus subtilis, and Aspergillus niger were identified at contaminated sites. Enzymatic activities were significantly inhibited in contaminated soils compared to the control. The study concludes that asphalt contamination negatively affects soil microbial structure and function, highlighting the ecological risks of asphalt pollution and the need for bioremediation strategies in affected tropical soils.