Pollution characterisation, ecological and human health risks assessment of potentially toxic elements in soils of Ikorodu industrial area of Lagos, Southwestern, Nigeria

Abstract

Rapid developments in industrialisation and urbanisation have resulted in serious environmental pollution. It is therefore imperative to evaluate contamination levels, sources, and ecological and human health risks of potentially toxic elements (PTEs) in soils. This work examined the degree of PTE pollution in soils collected from Ikorodu Industrial Layout in Lagos, Nigeria. Concentrations of PTEs were determined by digesting the soil samples with aqua regia and analysing them using an atomic absorption spectrophotometer (ICE 3000 series). The results showed that the majority of the PTEs analysed did not exceed the guideline values, but Zn was enriched at about 27% of the sampling locations. The enrichment and contamination factor computations revealed Zn and Ni as the highest and lowest contaminants, respectively. Pollution assessment tools employed Enrichment factor and Contamination factor (EF and CF) showed a similar PTE pattern (in descending order): Zn > Pb > Cd > Cu > Fe > Mn > Ni. Ecological risk assessment revealed that about 70% of sampling locations had significant potential ecological risks. Correlation and hierarchical clustering identified geogenic, anthropogenic and mixed contributions to soil PTE load. Hazard index indicators for children and adults wer less than 1, which suggests there was no potential for significant toxicity risks. Carcinogenic risks were estimated for Cd, Ni and Pb and results were within acceptable risk levels, but children are more vulnerable to cancer and non-cancer risks than adults.