A chemometric review of heavy metals (Zn, Cd, Pb, Fe, Cu, Ni and Mn) in top soils of Imo state, Southeastern Nigeria

This study provided a comprehensive review of the status of heavy metals viz Zn, Cd, Pb, Fe, Cu, Ni and Mn in top soils of Imo state from 2010 to 2020. Distribution by zone revealed that 87, 11 and 2% of studies concentrated in Owerri, Okigwe and Orlu zones respectively. Obtained data showed that in Owerriand Okigweconcentration ranged from 4.06 +/- 5.53 for Cd to 2070.03 +/- 2154.99 for Fe and 21.79 +/- 2.06 for Ni to 30371.69 +/- 52450.75 mg/kg respectively. Data collected were further modelled using chemometrics such as contamination factor, pollution load index, geoaccumulation index, enrichment factor, ecological risks index, average daily intake, hazard quotient and index as well as cancer/carcinogenic risks. Result showed that the top soils were highly polluted and enriched particularly for Cd, Pb and Cu. By zone, Okigwe was most polluted while studies are scarce in Orlu. Pollution source assessment showed that the major pollution source were from automechanic related activities and indiscriminate waste dumpsites. Exposure pathways to heavy metals were ingestion > inhalation > dermal. Only Pb and Fe from ingestion pathway will pose risks from intake while non-carcinogenic adverse health risk is only obtainable from the same pathway. Only in Okigwe zone, that Cd, Pb and Ni will pose cancer risks from the ingestion pathway to both adult and children. Overall, results suggested that top soils of Imo state are polluted with high ecological and human health risks to children than adult. Effort to reduce activities that input heavy metals in the soil should be encouraged.