Earthworms Eudrilus eugeniae as Bio-indicators of Heavy Metal Contamination in Port Harcourt Dumpsites

Abstract

Heavy metal pollution of terrestrial and aquatic ecosystem through improper management of dumpsites and indiscriminate dumping of waste has been recognised as a serious environmental concern in the city of Port Harcourt. It is important to validate the extent of contamination of heavy metals in dumpsites to successfully validate the exposure of humans living around its environs. To investigate heavy metal concentrations in soils of dumpsites, earthworm Eudrilus eugeniae was used as bio indicators in dumpsites Wimpy, Mgbuoba and Rumuokwuta in Obio Akpor local government of Port Harcourt. Earthworm E. eugeniae and soil were sampled during the wet season (July 2006), digested using concentrated HNO3, and concentrations of Pb, Cu, Cd, Ni, Zn and Cr were analysed with an atomic absorption spectrophotometer. Correlation between earthworm E. eugeniae and soil shows that E. eugeniae are good bio indicators of available metal in soil. Concentration of heavy metals in soil samples from dumpsites were within the Canadian environmental guideline for contaminated site remediation and Toronto public health (TPH) guide for soil testing in urban gardens with the exception of Zn which requires remediation action. Bioavailability of metals in soil was shown to be low, suggesting the presence of complex species in soil which reduces mobility of heavy metals.