SOIL CONTAMINATION AND RISK ASSESSMENT IN AREAS COVERED BY SHALE BEDROCK IN PARTS OF SOUTH EASTERN NIGERIA
Based on Principal Component Analysis (PCA), PC1, PC3 (surface soil) and PC1, PC2 (subsurface soil) are said to be associated with lithogenic factors derived from parent soil material, while PC 2 (surface soil) and PC3 (subsurface soil) probably originates from anthropogenic sources such as the Pb-Zn mineralization hosted by the shale bedrock. The concentration of these elements in the soils and vegetables reflect the geochemical composition of the shale bedrock in the study area. The calculated potential ecological risk value indicated that only 2.45% of the sites are in the class of great to very great risk zone, whereas 4.92% and 92.63% are in the class of considerable and low risk zones respectively. In addition, calculated composite ecological risk indices also revealed that 95.91% of the sites are in the class of low risk zone, 2.50% and 1.63% are in the class of moderate to considerable risk and very great risk zones and this is mostly attributed to Pb contamination. However, risk assessment calculated via exposure by soil ingestion and dermal contact by these toxic elements were generally low and within safe limit.