Seasonality and ecological risks of polycyclic aromatic hydrocarbons PAHS in environmental media and food crops of Ibaa, Niger Delta, Nigeria

Abstract Introduction Oil exploration in the Niger Delta has resulted in severe contamination of environmental media, with polycyclic aromatic hydrocarbons (PAHs) recognized as priority pollutants by the U.S. EPA. This study assessed the levels and ecological risks of PAHs in soil, sediment, surface water, groundwater, and food crops from Ibaa, an oil-impacted community in the Niger Delta. Methods These samples were collected during the wet and dry seasons and analyzed for 16 priority PAHs using gas chromatography–mass spectrometry (GC–MS) following U.S. EPA protocols. Contamination factors, risk quotients (RQ), and diagnostic ratios were used to evaluate contamination levels and identify PAH sources. Results were compared with international standards from the WHO, USEPA, EU, and Canadian guidelines. Results Total PAH concentrations (Σ16PAHs) in soils ranged from 0.60–12.29 mg/kg, exceeding the Canadian agricultural soil guideline (0.1 mg/kg) by over 100 times. Surface water PAHs reached 0.693 mg/L, surpassing the WHO limit for drinking water (0.0002 mg/L) by more than 3000 times, while groundwater remained below but close to acceptable thresholds (RQ∑PAHs ≤ 0.157). PAHs in food crops (0.007–0.020 mg/kg) slightly exceeded the EU limit (0.01 mg/kg) but posed minimal ecological risk (RQ∑PAHs < 1). Soils and sediments in the dry season showed the highest ecological risk, with diagnostic ratios indicating a predominantly petrogenic source. Conclusion and recommendation The findings demonstrate persistent PAH contamination that threatens soil fertility, aquatic ecosystems, and food safety in Ibaa. The study indicates the potential for bioaccumulation and long-term exposure risks to local populations. Immediate remediation, strict regulatory enforcement, and continuous monitoring are recommended to mitigate ecological and health hazards in the Niger Delta.