Concentrations Pollution Indices of Heavy Metals in Soil around Okerenkoko and Benikrukru, Delta State Nigeria

Abstract

Heavy metal contamination in soils of Niger Delta region, Nigeria driven by oil spills and illegal refining, poses serious ecological and human health risks. This study evaluated subsurface soil pollution in Okerenkoko and Benikrukru communities by determining concentrations of seven heavy metals and associated risks. Eight composite surface soil samples (0–15 cm) were digested and analyzed by atomic absorption spectrophotometry. Mean concentrations were Zn 8.65 ± 4.34, Cu 6.06 ± 3.06, Pb 1.36 ± 0.69, Cr 2.43 ± 1.18, Cd 12.1 ± 5.19, Ni 7.8 ± 1.8, and Hg 1.10 ± 1.36 mg/kg; Zn, Cr, Cd, Ni, and Hg exceeded WHO permissible limits. Pollution indices (CF, PLI, mCd, Igeo) confirmed moderate to very high contamination, while potential ecological risk was dominated by Cd (mean PER 92.27) and Cu (50.77). Human health risk assessment revealed unacceptable non-carcinogenic risk to children (THI 8.08) and elevated lifetime cancer risk (children 9.56 × 10⁻⁴; adults 5.21 × 10⁻⁴), mainly through ingestion. The study confirms severe anthropogenic pollution from petroleum activities, with children most vulnerable. Urgent regulatory enforcement, continuous monitoring, and targeted remediation (phytoremediation) are recommended. This work provides critical baseline data and integrated risk quantification for understudied oil-impacted within the Niger Delta communities.