Ecological vulnerability assessment of trace metals in topsoil around a newly established metal scrap factory in southwestern Nigeria: geochemical, geospatial and exposure risk analyses

In this study, geochemical, geospatial and exposure risk analyses were combined to assess the ecological vulnerability to toxic metals of topsoil around a metal recycling factory in southwestern Nigeria. Samples of topsoil around the facility were collected and analyzed for Cd, Zn, Pb and Fe by atomic absorption spectrophotometer. Enrichment factors (EF) with reference to local background values were calculated to assess the extent of contamination of the topsoil. EF values showed that topsoil was moderately enriched with Cd and Zn, while the Pb level in the topsoil was close to the reference value. Spatial mapping of concentrations indicated potential ecological hazard (PEH) from Cd at the N, SW and SE of the factory; isolated zones of Pb within PEH at the N and SE, whereas 70 % of the area displayed Zn concentrations at the PEH threshold. Mapping of EFCd showed a differential pattern of EF levels, with isolated hotspots of extreme and high enrichments at the N and S, respectively. Ninety-nine percent of the studied topsoil around the factor was minimally enriched in Pb, while EFZn mapping indicated minimal to moderate enrichment. The immediate surroundings of the factory are moderately enriched in Zn, while the extreme N was minimally enriched. Exposure risk assessment gives an estimated hazard index that implies no current risk of health hazards for humans. However, it is advised that an effective pollution control should be implemented, because there is the possibility of increased hazard as production continues.