Assessment of Heavy Metal Contamination and Bioaccumulation in Earthworms Across Varied Land Uses in Ekiti State, Nigeria

This study examines heavy metal contamination and bioaccumulation in earthworms across three sites in Ekiti State, Nigeria: Are Oil Palm plantation, Irasa waste dumpsites, and EKSU Teak plantation. Soil and earthworm samples were analyzed for copper (Cu), cadmium (Cd), lead (Pb), and zinc (Zn) using atomic absorption spectrophotometry. Results showed the highest contamination at Irasa waste dumpsites, with Cu, Cd, Pb, and Zn concentrations averaging 45.2 mg/kg, 8.4 mg/kg, 36.7 mg/kg, and 112.5 mg/kg, respectively. Are Oil Palm plantation exhibited moderate contamination, with Cu, Cd, Pb, and Zn averaging 29.5 mg/kg, 4.2 mg/kg, 18.6 mg/kg, and 67.9 mg/kg. The EKSU Teak plantation showed the lowest levels, averaging 15.3 mg/kg for Cu, 2.1 mg/kg for Cd, 9.8 mg/kg for Pb, and 35.4 mg/kg for Zn. Bioaccumulation analysis revealed a strong correlation with soil contamination, with earthworms from Irasa waste dumpsites containing the highest concentrations of Pb and Cd, at 25.3 mg/kg and 5.6 mg/kg, respectively. Earthworms from Are Oil Palm recorded 13.1 mg/kg for Pb and 2.9 mg/kg for Cd, while those from EKSU Teak had the lowest levels, at 6.5 mg/kg for Pb and 1.5 mg/kg for Cd. The study highlights significant heavy metal contamination and bioaccumulation gradients influenced by anthropogenic activities. The elevated contamination at Irasa waste dumpsites emphasizes the need for pollution control and remediation strategies to protect soil and ecological health.