Ecological Risk Assessment of Crude Oil Impacted Soils of Selected Communities in Imo and Abia States, Nigeria

This study examined contamination by cadmium, chromium, lead, copper, and manganese in soils from oil-affected parts of Imo and Abia States, Nigeria. Samples from depths of 0 to 45 cm were analysed using atomic absorption spectrometry. Imo soils had high lead levels from 50.10 to 51.44 mg/kg and copper from 73.64 to 73.83 mg/kg. Abia soils were severely contaminated with chromium from 144.53 to 223.39 mg/kg. Average contamination factors for lead were high in both states, Imo 3.58 to 3.67 and Abia 2.90 to 4.88. Cadmium contamination factors showed moderate contamination, Imo 1.07 to 2.2 and Abia 0.65 to 1.22. The degree of contamination was moderate for cadmium and copper, low for chromium and manganese, and considerable for lead in Imo. In Abia, cadmium, chromium, copper, and manganese were low, while lead remained considerable. Although contamination factors were elevated, pollution load indices stayed below 1.0 at all sites, indicating no overall pollution. The geo-accumulation index for lead fell within the moderate contamination range, Imo 1.26 to 1.29 and Abia 0.85 to 1.49. Ecological risk index values were low overall, Imo 64.81 to 99.28 and Abia 48.27 to 69.52, though cadmium posed the highest individual risk. In conclusion, while specific metals, especially lead and cadmium, contaminate these soils, the overall ecological risk remains low.