Vermiremediation Potentials of Lumbricus terrestris and Eudrilus euginae in Heavy Metal Contaminated Soil from Mechanic, Welder workshop and Metallic Dumpsite

The need to reclaim contaminated soils is important in ensuring the sustainability of life and biodiversity. Food crops grown in heavy metal contaminated soils have the risk of passing the accumulated metals to man and such has been demonstrated to cause various diseases in man. In this study, we investigated the potentials to reclaim heavy metal contaminated soil using Eudrilus euginae and Lumbricus terrestris. The contaminated soils were obtained from mechanic, welder and metallic workshops and were grouped individually and as combinations. The soils were incubated with the earthworms and the quantities of heavy metals in soil were determined before and after the growth of the earthworms. The percentage of the heavy lost from soils at the end of the study was calculated to evaluate the ability of the earthworm to enhance the remediation of heavy metal contaminated soil. The presence of the earthworms led to more reduction of the levels of the heavy metals in the soils than natural attenuation. The presence of L. terrestris led to a lower reduction of Cd, Cr and Pb in the combined soil from the three sites but a greater reduction of Zn and Ni from such soil. The presence of E. euginae led to greater loss of all the heavy metals in the soil from the welder workshop and greater loss of Cd, Pb, Ni and Zn in the soil the mechanic workshop than L. terrestris. The presence of E. euginae led to more loss of Cr, Pb, and Ni in combined soils of mechanic and welder workshops and mechanic workshop and metallic dumpsite. The findings of this study show that although the presence of both earthworms enhanced the remediation of heavy metals from the soils, the efficiency of the remediation is organism-specific and site-specific. Study on detailed mechanisms of enhancing heavy metals by earthworms is recommended.